Elective or Emergency Childbirth, a Choice Between

¶ … elective or emergency childbirth, a choice between general and local anesthesia is often called for. Cognizing the surroundings helps the birthing process. Therefore, a local anesthetic administered via an intrathecal spinal injection or through a catheter in the epidural space will prove an advantage. Ratcliffe and Evans at John Radcliffe Hospital in Oxford, England attempted tested this advantage on more than 90 elective Cesarean parturients. (Ratcliffe & Evans, 1993) The epidural anesthetic group enjoyed the most advantages. The determinants to support these findings were fetal and maternal health. These were judged by Apgar scores and also the pH values of the umbilical blood. The greatest acidities (pH less than 7.2) were observed in neonates in the spinal anesthesia groups. In terms of general fetal health, 70% of neonates from the general anesthesia group did not meet an Apgar score of greater than seven in the first minute after birth.

APGAR scores are associated with the immediate health and viability of the newborn. These scores are tallied at every minute after birth up to five minutes and up to ten minutes in case of any distress. APGAR is the abbreviation for: Activity, which is indicative of muscle tone, Pulse, Grimace -- a measure of reflex, Appearance, and Respiration. (Parer, 1996) A point is awarded if the baby shows active movement, has a pulse over 100 beats per minute, pulls away and cries, breathes and cries and other wise appears normal. A score of seven to 10 is considered a normal delivery. A score between four and seven necessitates resuscitative action. A score of three or less would necessitate immediate resuscitation. A score of zero over time is indicative of stillbirth. Apgar scores and other hemodynamic measures is a sign of a new born and maternal health. Positioning of the mother can have an impact on these measurements.

Blood loss during childbirth or blood pooling in the extremities following epidurals and local spinal anesthetics, where the peripheral arterial resistance is impaired, results in hypotension. (Emmett et al., 2002) meta-analysis was conducted at the University of Toronto in Canada to assess the efficacies of different treatment modalities to reduce hypotension in women that used spinal and/or epidural anesthetics. (Morgan, Halpern, & Tarshis, 2001)Twenty-three studies were considered for this meta-analysis. The efficacies of the treatment were determined in terms of reduction of incidences of hypotension and other hemodynamic variables. The effects of volume preloading with crystalloid and colloidal solutions, and wrapping in bandages or the use of stockings in addition to the use of vasoconstrictors such as ephedrine was studied. Ephedrine was naturally useful in causing dose related enhanced heart rates and cardiac output -- called for in these cases to counteract the hypotension. Ephedrine was also used as the recourse for intervention when maternal hypotension persisted. The results of this study revealed that crystalloid preloading were not effective in reducing incidents of hypotension when compared to controls. Bandage wrapping were always preferred to stockings. Every study that used colloidal solution preloads indicated that these solutions did help in decrease incidents of hypotension. Only one study reported that preloading with colloidal solutions did not prove useful.

Another meta-analysis of twenty-one relevant studies carried out in Adelaide in Australia indicated that none of the above-mentioned techniques were conclusively implicated in reducing hypotension. The meta-analysis compared crystalloid vs. colloidal solutions used to preempt loss of preload volume, the use of compression techniques vs. controls and the use of ephedrine vs. controls. Besides hypotension, other standard hemodynamic variables were measured for the mother and the fetus. In all four types of study the relative risks (odd ratios) were determined as measures of the use of one technique over another or a technique vs. A control. The odds ratios, respectively for the four studies were 0.78, 0.63, 0.54 and 0.70. (Emmett et al., 2001) Since this is the measure of beneficial results and all the values are over 0.50, the results cannot be considered significant under conventional epidemiological standards.

A study from the University of Liverpool is a good indicator of the current trend in managing maternal hypotension. Some of the problems with creating experimental conditions are fear of the risks to the neonates. (Burns, Cowan, & Wilkes, 2001) Also, the results from different studies are often confounders and there might be a general tendency to go with whatever has been tried and tested. This study was based on survey of obstetricians and anesthesiologists. In each of the different techniques that will be explored in this work, the majority (more obstetricians and anesthesiologists chose an option) opinions are listed. The authors of the study averred overwhelmingly that Hartmann's solution was the preload of choice. Most gave an infusion of one liter. A left lateral tilt was favored; and, ephedrine was used as the vasopressor of choice in maintaining blood pressure.

One of the problems in identifying the best technique is that the results often conflict from one study to another. There is also a lack of wide-ranging and widely accepted guidelines. Very often, researchers will use techniques in conjunction. Unfortunately, these only serve as confounders.

Intravenous fluid / volume loading

Decrease in arterial blood pressure in the peripheral regions following local anesthetics is due to the loss of resistance due to the numbing effects. This results in reduced venous blood flow. Preloading with intravenous infusions is called for to maintain preload cardiac volumes. This assures stroke rates and cardiac outputs. Intravenous infusions attempt to maintain cardiovascular function by mimicking the constituents of blood plasma. These preload solutions can be either crystalloid or colloidal in nature. (Vercauteren et al., 1996) The volumes and the flow rates of intravenous infusions would perhaps play a role in reducing hypotension in addition to the compositions of these solutions. The latter is a measure of how the patient assimilates these solutions.

Infusion of Hartmann's solution in 51 patients from cohort of 104 showed significant improvements in fetal heart rates and maternal instances of hypotension. When compared to the control group, which was composed exclusively of healthy parturients, the fetal heart rate abnormalities decreased from 34% to 12% versus the cohort. Cases of maternal hypotension also decreased to 2% from 28%. (Collins, Bevan, & Beard, 1978)

The results of this study were supported by another study authored by Lewis, Thomas and Wilkes. (Lewis, Thomas, & Wilkes, 1983) They used Hartmann's solution in 60 patients, which they averred was a superior preload alternative than other available choices. Using Hartmann's solution, the incidents of hypotension were reduced to 6.7% according to the results of this study.

Often, the importance of a safe delivery causes researchers to recourse to interventions. A study conducted by Kinsella et al. (Kinsella, Lee, & Spencer, 1990)indicated that though the use of a preload of crystalloid solution improved cases of fetal heart rate in the test cases vs. controls, there were no significant differences in maternal hypotension. This study was conducted at St. Michael's Hospital in Bristol, UK on 105 women. All women were subjects for epidural local anesthesia.

A study at the University of Natal in South Africa also showed that flow rates of crystalloid volumes in preloading did not have an affect on decreasing hypotension in parturients. In fact, a few members of the rapid infusion cohort suffered from "unacceptable hypertension." (Rout, Akoojee et al., 1992) Twenty patients were divided into two subgroups of 10 patients each. The subgroups were administered crystalloid solutions of a specific volume over a period of 20 minute, or twice as rapidly over 10 minutes. The number of patients that suffered from hypotension was not significantly different between the two groups (6 and 7 patients).

The central venous pressure in the rapid infusion group was higher. But this did not impact the incidences of hypotension.

A relatively less used crystalloid solution is dextrose. (Warwick & Weingarten, 1994) Also, normal saline is not typically indicated because it does not contain a true balance of electrolytes and non-electrolytes. A study of 119 parturients for elective Cesarean procedures were administered either a five percent solution of dextrose in saline or a normal saline solution. The infusions were conducted two hours prior to the cesarean delivery. (Wilson et al., 1999) Over two hours, approximately, a quarter of liter of solution was intravenously infused. The results of the study indicate that adding dextrose to the preload solution did not in anyway reduce the incidents of hypotension. Bupivacaine 0.75%, fentanyl and morphine was the anesthetic cocktail of choice in this study. An infusion of fluids along with ephedrine was used to treat any resulting hypotension. Also, the need for ephedrine and the dosage of ephedrine administered did not depend on whether the patients used the dextrose vs. The normal saline solution.

A reevaluation study at the University of Natal by Rout and co-workers decisively concluded that there was no need for the use for a mandated fixed volume of preload prior to a spinal or epidural anesthetic. Their study indicated that the effects of crystalloid preloading were indeed useful and gave lesser incidents of hypotension that were statistically significant, but specific volumes were not called for. Their study included 144 patients that were unequally divided into two subgroups. All patients opted for Cesarean births. The test subgroup was larger than the control subgroup. The control subgroup was given no preload solutions. The test subgroup was administered a crystalloid preload 20 minute prior to the injection of the anesthetic. Seventy one percent of the control group suffered from hypotension versus 55% of the test subgroup. Hypotension was determined as 100 mmHg of systolic arterial pressure or a decrease by 20% of the baseline SAP. (Rout et al., 1993)

Researchers at the Queen Mother Hospital in Glasgow, Scotland have also abandoned the routine of specific volume preloading. They studied 60 healthy elective Cesarean delivery women with a preload volume of 1000 mL of crystalloid solution versus 200 mL. (Jackson, Reid, & Thorburn, 1995) Arterial pressure was measured soon after the anesthetic was applied. Ephedrine interventions were called for as soon as hypotension was observed. The threshold for this was set at 90 mm Hg or 30% of the baseline pressure. The significant differences in preload volumes did not significantly affect the incidents of hypotension. The authors of the study reported that 10 women from the 1000 mL cohort and 9 women from the 200 mL cohort were suffered from hypotension lasting greater than 3 minutes before ephedrine was administered.

While the above two studies indicate that volume of crystalloid solution has nothing to do with the overall outcome of maternal and fetal hemodynamics, another study by a Hahn and Resby at the Karolinska Institute in Sweden report that the body processes volume differently in attempting to maximize venous return preload. And this mechanism of processing may have a bearing on maternal hypotension. Volume handling was studied by attempting identify how the volume loss from reduced venous return is compensated by the infusion of fluids. The two solutions used were lactated Ringer's solution and a 3% dextran solution. (Hahn & Resby, 1998) The parameters measured to determine volume handling were blood hemoglobin concentrations and urine amounts. There are no conclusive mechanisms for how the body compensates for volume loss with infused solution because the observed results have to be applied two theoretical models, the results of which vary.

And in yet another study conducted at Harvard Medical School, the necessity of maintaining crystalloid volume has been questioned. The results for 55 parturient women who were administered volumes of 10, 20 and 20 mL/kg of crystalloid preload solutions indicates that not only did the volumes affect the onset of hypotension after the anesthesia was injected, even the duration of the hypotension did not change. (Park et al., 1996) Ephedrine was used to correct to normal blood pressure. And the need for ephedrine intervention did not change for the three groups. The researchers also conclude that there is a significant danger of fetal or maternal edemas if case of larger preload volumes. For this study, the colloid osmotic pressure and the mean arterial pressure were parameters measured as determinants of hypotension.

A new mode of thinking has emerged as regards to the amounts of volume and concentrations of preloading solutions, whether crystalloid or colloidal. This school of thought involves precluding the use of preload solutions by administering lower dosages of anesthetic and epidural blocks. The idea is that lower concentrations of anesthetics will enhance venous returns, thereby decreasing incidents of hypotension. Hofmeyr, at University of the Witwatersrand in South Africa, carried out a meta-analysis to determine exactly this notion. The author of this study agrees that there could be significant biases in the clinical trials chosen for the meta-analysis. (Hofmeyr, 2002) Confounders such as results from some studies that indicated the beneficial uses of crystalloid solutions in conjunction with high dosages of anesthetics conflicted with other clinical trials that did not find significant improvements in the use of crystalloid preloads. A study that indicated that those administered low doses of anesthetics also did not suffer from higher incidences of maternal hypotension or abnormal fetal hemodynamics. The author concedes however, that the cohort for this study was too small and further work would be needed to ascertain the results of this study.

The use of colloids in preventing post-anesthetic hypotension is shown through studies to have more beneficial effects than merely using crystalloid solutions. A study by Kee et al. from the Chinese University of Hong Kong on 68 patients revealed that using a colloidal preload will have a largely prevent hypotension. The cohort was divided into a group of 33 parturients that were given a 4% solution of gelatin (product name Gelofusine) at 15 ml/kg. (Ngan Kee et al., 2001) The control group of 35 individuals was not given a colloidal preload. The efficacy of colloidal preloading was measured; besides on the low mean systolic arterial pressures, on the amount of vasopressor, metaraminol, which was intravenously fed to the patients to ensure that the blood pressure was at 90 to 100% of the baselines. The efficacy of the gelatin groups was established based on results, which showed that the control group needed a more rapid infusion of the vasopressor and at greater concentrations. The average dosage was 0.6 mg/mL more for the control group. The low mean SAP was also lower for the control group that the colloid preload group. The lowest point of the mean SAP was about 7 mm of Hg.

There are several direct-comparison studies, which show that colloid preloading is more beneficial than crystalloid preloading. The advantages that colloids offer are smaller volumes of preload solutions.

A study of 26 healthy parturients undergoing elective C-sections were given half a liter either of lactated Ringer's solution or half that amount of a hydroxyethyl starch colloidal solution. Comprehensive observations of maternal hemodynamics reveal that the incidents of maternal hypotension were significantly larger in the crystalloid preload group at 62%, versus 38% for the other group. The results did not have any effect on fetal hemodynamics based on Apgar tests. Despite these findings, the researchers at the Oulu University Central Hospital in Finland agreed that the results were inconclusive. (Karinen et al., 1994) The pulsed Doppler techniques that they used to measure maternal hemodynamics reveal a potential confounder. This parameter was the pulsatility index (PI). These indices are measures of uterine arterial response. No matter what the subgroup, these values spiked and dipped and settled down quickly. This led the researchers to believe that the uterine arterial response does not change depending on the preload solution.

In another study by the same group in Finland, the pulsatility indices and other hemodynamics were studied for the fetuses. The studies were performed on a similar cohort as the above study. The relative amounts of crystalloid vs. colloidal solutions (2:1 by volume) were also the same. Comprehensive hemodynamics measurements were taken. The results indicate that colloid vs. crystalloid preloads have no effect on the outcome of the birth or the health of the baby. A few additionally, perhaps insignificant factors were observed: on infusion with the colloidal solution, the pulsatility index for the mothers generally decreased; on infusion with the crystalloid solution, the fetal heart rates temporarily increased. (Karinen et al., 1995) study at the Hammersmith Hospital in London for 50 women with elective Cesarean option revealed that hemodynamics results including hypotension did not significantly change based on the group that was administered with two liters of crystalloid preload with 1 liter of a colloid preload.

On the other hand, a study of 20 women who were given either solely Hartmann's solution (1 liter) or a combination of Hartmann's solution with a 5% added polygelatin (Haemaccel) of 0.5 liters showed that infusion with the mixture presented with reduction in hypotension. (Murray, Morgan, & Whitwam, 1989) The maternal hypotension reduced to 5% in the mixture group, versus 45% in the crystalloid group.

A study at the University of Texas Southwestern Medical School by Sharma and co-workers revealed that a 6% colloidal solution (500 mL) was significantly more effective at reducing hypotension in post spinal anesthetic for tubal ligations than twice the volume of a lactated Ringer's preload. (Sharma, Gajraj, & Sidawi, 1997) Of the forty members of this study, 52% of the 21 patients from the Ringer's preload group needed intervention for symptoms of hypotension. Only 16% of 19 members of the colloid group presented with hypotension. More ephedrine had to be infused as an intervention for hypotension in the crystalloid group.

Similarly overwhelming benefits were not observed for the colloid group participating in a study of the efficacy of preloading in elderly patients who were undergoing hip replacement surgery. While this colloid group (Haemaccel, 500 mL) showed higher overall systolic blood pressure, morbidity from hypotension was not significantly implicated in the other groups. The other groups were given 500 mL of Hartmann's crystalloid preload solution; the control group did not receive any pre-hydration. (Hallworth, Jellicoe, & Wilkes, 1982) The age range of this test group was from 60 to 89 years. There were no differences in the dosage requirements for ephedrine interventions in cases of severe or mild cases of hypotension.

A study by Riley and co-workers comes out strongly in favor of the use of colloid preloading as opposed to crystalloid preloading. Riley and co-workers undertook this study to assess the relative efficacy of the use of lactated Ringer's solution vs. A 6% hetastarch solution. (Riley et al., 1995) Forty women who opted for cesarean delivery were divided into two groups. One group received a preload of 2 Liters of lactated Ringer's solution. The second group received 500 mL of a 6% hetastarch solution in addition to a liter of Ringer's solution. The results were overwhelmingly in favor of hetastarch that the researchers recommend that it be used as a standard prior to the use of local spinal or epidural anesthetics. Over 85% of the lactated Ringer group showed symptoms of hypotension versus 45% of the hetastarch group. The hetastarch group had a higher SAP by 7 mm Hg. The lactated Ringer group also had a higher heart rate and a shorter time before the onset of hypotension. This group also needed more frequent and higher doses of ephedrine.

In terms of comparing colloid and crystalloid preloads or combinations of the two, serum albumin infusions do not offer any advantages over lactated Ringer's solutions. A study of sixty patients was divided into three groups. Each group was administered a 1200 mL solution. The first group was given exclusively lactated Ringer's solution. The remaining two groups were given different combinations or Ringer and serum albumin at varying percentage volumes and concentrations. (Ramanathan et al., 1983) The albumin levels were measured immediately and 24 hours after the infusion. Results indicate that all the groups fared similarly without an advantage to any one group in this study.

Researchers at the University of Goteborg in Sweden tested exclusion of large volumes of preloads when smaller volumes with prophylactic concentrations of ephedrine could be mixed with colloid solutions. The researchers divided the test cohort into two groups. These groups were given a mixture of 7.5 mg of ephedrine with 3% dextran 70 colloidal solution, intravenously. The second group was also medicated intravenously with twice the volume of only dextran solution. (Wennberg et al., 1992) There were no advantages in terms of reducing hypotension between the two medications. This means that larger volumes were not necessary when mixtures would work just as well. The researchers also informed that incidences of maternal nausea were lesser in the mixture group.

VASOPRESSORS

One of the problems with identifying appropriate dosage of anesthesia is that too little results in discomfort from peripheral pain; too much results in the maternal hypotension de to impaired venous (blood) return. The anesthetist has to balance these conditions such conditions are optimal for such obstetric procedure. The preceding section of this work provided a detailed discussion of the combinations of the relative efficacies of replacing preload volumes of venous returns with crystalloid or colloidal solutions. These techniques and additional physical techniques will be discussed later in this work. Each of the physical techniques is used to prevent the overuse of medication because of the need to preserve maternal, fetal and neonate health. In most clinical trials however, ephedrine is identified as the gold standard for immediate rescue. Ephedrine is used to correct for decreases in blood pressure. It works by increasing cardiac output, the heart rate and hence the arterial pressure. The mechanism of ephedrine action is a combination of that of an ? And ? adrenoreceptor. The following section will explore the role of ephedrine not only as an intervention, but a prophylaxis. Because of the positive effects of ephedrine in reducing incidences of hypotension, one might consider using it to maintain pressure soon after the epidural or spinal injection is administered. Clinical trials (discussed hence) then become necessary to identify the appropriate dosage. This is important because of the dangers of a higher than necessary dosage that might cause hypertension and tachycardia endangering the life of the fetus and introduce neonate abnormalities.

There are other inherent dangers. This is in cases of parturients that are prone to hypertension. If such dangers are imminent, other alternatives must be developed and tested. The following section will also explore the role of phenylephrine's role in reducing maternal hypotension. Results will also be discussed in comparing the efficacies of the two. Treatment modalities will also be discussed when epinephrine and phenylephrine are combined.

Epinephrine

Identifying the appropriate dosage is very important in this study. In order to identify appropriate dose of ephedrine, Simon et al. At the Hopital Saint-Vincent de Paul in Paris, France divided a test group of 108 women who opted for Cesarean deliveries. The test group was divided into three subgroups. (Simon et al., 2001) The first group was given a 10 mg dose of ephedrine intravenously. Similarly, groups II and III were administered 15 and 20 mg doses. These doses were given 2 minutes after the spinal anesthetic was administered. The anesthesia was given in the full lateral position. The patients were then uniformly placed in a supine position with a 15-degree left lateral tilt. Positioning will be discussed in detail in the following sections. This position is necessary to displace the uterus in a manner that does not press on the inferior vena cava thus causing further breakdown in the venous return.

Typical hemodynamic parameters were measured for the mother and the baby. The relevant statistics for this work were the mean arterial pressures, and the systolic and diastolic pressures. For this study, the magic number above or below a blood pressure baseline was considered as 30%. The upper threshold was also considered in this study to identify if the dosage in one or more groups was considered as high for fear of causing hypertension. Five mg boluses were given to the patients to correct for any hypotension.

No more than 50 mg of ephedrine was given to any of the women in either test groups. The study concluded that 10 mg of intravenous infusion of ephedrine was insufficient to combat the effects of hypotension. Better results were obtained in the subgroups given 15 and 20 mg of ephedrine. The fear of hypertension was ever present. And though seven of the 108 women showed signs of hypertension after ephedrine infusion, the number of women who suffered: two, two and three from the 10 mg, 15 mg and 20 mg subgroups, respectively, did not enable the researchers to correlate presentations of hypertension with the strengths of the ephedrine doses delivered.

Ephedrine has also been shown to work as an oral prophylactic. Clinical trials on 100 women were conducted at the Om hospital in Nepal. Spinal local anesthetics were administered for abdominal surgery. (Kafle, Malla, & Lekhak, 1994) The patients were given preload solutions intravenously. Prior to the administration of the anesthetic, one group of women was given an oral dose of ephedrine of dosage of 30 mg; the control group was treated with fluids. Post-anesthesia, the patients were treated with ephedrine to correct for symptoms of hypotension. The authors of the study concluded that the orally administered ephedrine significantly reduced the presentations of hypotension when compared to the control group. The need for supplemental ephedrine was more than twice as high in the control group that the oral-ephedrine group. The need to treat with inotrope fluids was also much higher in patients from the control groups.

The study by Simon et al. cites a study conducted by Kee and co-workers at the Chinese University of Hong Kong. (Kee et al., 2000) The French group, while studying the dosage criticizes the work by the Kee group in identifying 30 mg of IV ephedrine as effective in reducing maternal post-anesthetic hypotension. (Simon et al., 2001) One of the reasons was that the high dose of ephedrine produced unacceptable levels of hypertension. In contrast to the Simon group study however, the Kee group showed the smallest average instances of hypotension in the group that was administered 30 mg of ephedrine. In this study, hypotension presentations were higher in the 10- mg and 20-mg group but were statistically very similar. The study by the Simon group had averred that while 10 mg might be less than optimal, 30 mg might create problems of hypertension; and 20 mg was optimal in reducing symptoms of maternal hypotension. This study was conducted for 80 women for elective Cesarean delivery.

The authors of the Hong Kong study also concede that there were significant cases of hypertension and the high dose of ephedrine did not improve the neonate condition. They however, indicated that cases (albeit smaller) of hypertension were also seen in the lower ephedrine concentration groups and one hypertensive patient was from the control group that was not given ephedrine.

The previous section dealt with the need to preload patients with crystalloid or colloidal solutions before the anesthetic was injected. Following a study from the Queen Mary Hospital in Hong Kong, researchers Chan et al. concluded that in the presence of prophylactic doses of ephedrine prior to anesthesia administration preclude the need for preloading. Forty-six women undergoing elective cesarean procedures were given either a Hartmann solution preload or 0.25 mg/kg solution of ephedrine. (Chan et al., 1997) Hypotension was measured at two different levels. If the mother-to-be SAP declined by 20% of baseline, it was considered moderate. A decline of lower than 30% of baseline merited a designation of severe hypotension. Among the test subjects there were no significant differences between the two subgroups presenting moderate hypotension. However, the incidence of severe hypotension occurred almost twice (65% to 35%) among patients that were prescribed the crystalloid preload. Instances of shivering were more than three times in patients with the Hartmann's preload. Better umbilical pH values were observed for the ephedrine group.

In another study from Holbaek Central Hospital in Denmark, forty-eight patients who underwent spinal anesthesia were divided equally into three groups. While all groups were given a preload, the first group was given a 12.5 mg does of ephedrine intravenously; the second group was administered 37.5 mgs of ephedrine intramuscularly; the placebo group was not given ephedrine. The results indicate that the instances of hypotension were significantly larger in the placebo group. (Hemmingsen, Poulsen, & Risbo, 1989) Interestingly, the authors try to assess the responses of the patients based on their pre-procedures ASA (American Society of Anesthesiologists) classifications. The researchers indicated that the higher ASA risk patients were more likely to suffer from hypotension, some lower than 33% when compared to the baselines. The ASA provides patient classifications that range from roman numerals I to V and E. The latter (E) stands for emergency. Class I is for a normal healthy patient. Class II and III are for patients with mild or severe systemic disease presentations, respectively.

A class IV patient faces a threat to life. A Class V patient will not survive without the recommended procedure. In the Denmark study, the cohort of participants was non-obstetric. Their ASA classifications ranged from I to III. (Rolbin et al., 1982)

At the University Hospital in Antwerp in Belgium, the relative efficacy of ephedrine in resolving issues of maternal hypotension was tested vs. A placebo group of parturients that were fed normal saline. The concentration of ephedrine was 5 mg.

The saline or ephedrine was given soon after the spinal anesthesia. A combination crystalloid (I liter of Hartmann solution) and colloid (500 mL of hetastarch) was given to the patients before anesthesia. Severe hypotension was identified at 30% lower than the baseline systolic arterial pressure. Fifty-eight percent of the saline patients presented with hypotension versus 25% of the ephedrine group. Only two members of the ephedrine group had severe hypotension vs. ten from the saline group. (Kee et al., 2000). These groups considered 10 mg of ephedrine was less than an optimal does. The Belgian researchers conclude that this result holds for parturients that were prehydrated. Judging by the efficacious results for colloidal preloads, it is possible that the preload mixture and not insignificant amount of colloid preload helped in reducing hypotension.

Dosage of ephedrine is always a concern. While it helps with reducing incidences of hypotension, the resulting hypertension can hurt the mother and the fetus and cause significant problems in the neonate due to changes in blood pH. Researchers Rout et al. from the University of Natal in South Africa concluded that intramuscular administrations of high doses of ephedrine were not to be recommended. (Rout, Rocke et al., 1992) They also suggested that the use of high doses (50 mg of ephedrine) be abandoned. Their conclusions come from studies of 30 healthy parturients. The ephedrine doses of 25 mg and 50 mg were given. Controls were established with subnormal solutions of NaCl (0.9%). The results are more related to the incidences of hypertension. Hypertension resulted in nine patient in the 50 mg group and five patients in the 25 mg group. Typically, the pressures exceeded 20% of the baselines with the average increase of more than 28% over the baseline. The researchers were particularly concerned with rising blood pressure in case of failure of the spinal anesthetic to work effectively. They agreed that a situation such as this would necessitate general anesthesia and pose a significant threat to the life of the fetus.

The results, on the other hand, are beneficial with lower doses of ephedrine as was shown in clinical trials at the Rotunda Hospital in Dublin Ireland. While the control group was administered a 0.9% solution of NaCl, the test groups were given 6mg and 12 mg of ephedrine. These ephedrine doses were administered in single 6 mg boluses. All 68 members of this cohort were first given a lactated Ringer's preload. For cases of hypotension, interventions of 6 mg boluses of ephedrine were used. The ephedrine and the control solution were given post-anesthesia. The results of this study indicate that the 12 mg administration of ephedrine was ideal in preventing hypotension, when compared to presentations from the control group. (Loughrey, Walsh, & Gardiner, 2002) Also, the ephedrine interventions were also significantly lower with the 12 mg group.

One might assume that the next step in attempting to study the prophylactic effects of ephedrine would be to inject it as part of the anesthetic concoction. For this purpose, Fong et al. At the New York Cornell hospital used ephedrine sulfate. (Fong et al., 1996) This compound was used in conjunction with the epidural block and introduced at the same time. Patients were prehydrated with a colloid preload and placed in a supine position with a right wedge and a 15-degree tilt. A gross value for judging hypotension was set at 90 mm Hg or at 70% of baseline values. The results were inconclusive and actually showed the test group presenting with hypotension than the control group. The researchers provide results of their statistical analysis to show that the differences were not statistically significant. On observing the methodology of this trial, one might realize that this result is not surprising.

Hypotension is concerned with reduced venous return. An injection of ephedrine sulfate in the epidural space abutting the spinal column probably does not access the blood stream such that it can work on increasing the heart rate and cardiac output, and consequently the blood pressure. This trial was conducted for 50 healthy parturients. Tsen et al. At the Harvard Medical School also observed no improvements when ephedrine was mixed with the spinal anesthetic. Both the test and the control groups presented with maternal hypotension 70% of the time. (Tsen et al., 2000)

In a departure from what has been typically observed and also discussed above, a study of 122 healthy parturients some of whom were given a 10 mg bolus of ephedrine vs. none for a control group showed that the incidences of hypotension were the same (as percentage) between the test and control groups. (Shearer et al., 1996) Hemodynamic studies on the fetus reveal the ephedrine in this case resulted in the lowering of umbilical pH values.

Phenylephrine

In trying to identify the role of phenyl epinephrine in reducing maternal hypotension and maintaining other hemodynamic parameter (maternal and fetal) normal, researchers Kee and co-workers at the Chinese hospital of Hong Kong tested the effects of phenylephrine in 74 patients. Every patient was given 100 micrograms of phenylephrine intravenously following anesthesia. The blood pressures of the cohort were then monitored. (Ngan Kee, Khaw, & Ng, 2004) This group was then divided into three groups. The division of groups was based on the use of phenylephrine in maintaining systolic arterial pressures at 100%, 90% and 80% of the baseline. Not surprisingly, the incidences of hypotension in the first group were the lowest. Consequently, the amount of phenylephrine used for the first group as also the largest.

It seems that phenylephrine does values do not significant affect umbilical pH values and would be recommended when the neonate health is considered.

Phenylephrine can also be administered with the epidural cocktail in preventing maternal hypotension according to researcher from the Mackay Memorial Hospital in Chinese Taipei. The study was conducted for 81 patients undergoing procedures for hernia. In the typical epidural mixture, phenylephrine was added. The four groups were administered 0, 50, 100 and 200 micrograms of phenylephrine. (Cheng et al., 1999) The best results, in terms of lowest incidences of hypotension, were observed in the fourth group that was given 200 micrograms. The researchers inform that lidocaine was the primary anesthetic agent administered with the epidural mixture.

Comparison

For reasons mentioned above, while different vasopressors are being tested, though ephedrine remains the medication of choice. A study at the University of Northern Ireland tested the efficacy of ephedrine vs. methoxamine in terms of the hemodynamic variables for the mother and the fetus. (Wright et al., 1992) The uteral pulsatility index has been discussed previously. Maternal hypotension was measured in relation to this index. Though the final results in this study did not prove any conclusive evidence whether ephedrine or methoxamine was superior in reducing hypotension, there is reason to believe that ephedrine is better. Hypotension is inversely correlated with the uteral pulsatility index. The index did not change in patients that did not experience decreases in blood pressure. The indices did increase when symptoms of hypotension appeared. Injection with methoxamine had the effect of temporarily increasing the pulsatility indices, though these values decreased to baseline levels within two minutes of administering the vasopressor. Morgan has reviewed the role of epinephrine in preventing hypotension and academia or excessive acidity in the fetal blood. In this review, conducted at the University Hospital of Wales, Morgan avers that phenylephrine or methoxamine might be used. (Morgan, 1994) The author does not believe however, that it is indicated as a reducer of obstetric hypotension.

Catecholamines are hormones whose secretion-rise correlates with labor. Adrenaline and noradrenaline are examples of catecholamines. They enable the neonate to deal with the shock of birth. Catecholamines help to clear the infant's lungs in preparation for normal breathing, speed up the metabolic rate for quick stabilization, and promote a rich supply of blood to the heart and brain. These hormone levels increase in the mother and the neonate. (Sullivan, 2003) The effect of using ephedrine and phenylephrine was assessed in parturients. Measurements of the catecholamine levels along with other hemodynamic parameters indicate that the phenylephrine is as efficacious as ephedrine. 5 mg of ephedrine were used for one group. The phenylephrine group was given 40 micrograms of the compound. The medications were administered intravenously. The neonates in the ephedrine groups showed higher values of noradrenaline than the phenylephrine group. This might have important consequences. (LaPorta, Arthur, & Datta, 1995) Noradrenalin, often acting with adrenaline slows the fetal heart rate down. It enables the neonate to survive oxygen deprivation during birthing.

Another study conducted at the Harvard Medical School yielded results, which seem to indicate that under the right dose-concentrations, phenylephrine works as well as ephedrine in reducing maternal hypotension following a spinal anesthetic. The study of 60 healthy elective cesarean delivery patients randomly assigned to receive either 10 mg sequential boluses of ephedrine or 80-microgram boluses of phenylephrine as necessary to maintain baseline blood pressures. (Moran et al., 1991) Typical hemodynamic variables were measured. The partial CO2 pressures and pH of umbilical arterial blood were measured for the two groups. There were differences in the values. The researchers declare that though the values are different, for patients in the ephedrine group, carbon dioxide pressure was higher and umbilical blood pH values were lower. But values for both groups were within acceptable normal limits. For most other factors including maternal hypotension, the numbers were not different to statistical significance.

Similar differences (as above) were seen in umbilical arterial pH values in a clinical trial of 38 elective Cesarean delivery parturients. The subjects were prehydrated with lactated Ringer's preload. After the administration of spinal anesthesia, the patients were treated with either 5 mg boluses of ephedrine or 100-microgram boluses of phenylephrine. The incidences of maternal hypotension were reduced in both cases without statistically significant differences. (Thomas et al., 1996) Heart rate drops occurred with phenylephrine significantly more than in the ephedrine group. Atropine had to be given to these subjects to restore heart rates to compensate for impaired venous returns.

The amount of phenylephrine or ephedrine administered is important. A study of 29 parturients in Birmingham Maternity Hospital, in Edgbaston, England were administered either 1 mg/min of ephedrine, 2 mg/min of ephedrine and 10 micrograms/minute of phenylephrine. In order to maintain threshold arterial pressures, 6 mg boluses of ephedrine were used for the ephedrine group and 20-microgram boluses were used for the phenylephrine group. The results indicate that all of the phenylephrine patients did not meet the upward threshold for hypotension. The best results were indicated for the 2-mg/min ephedrine groups for every parameter measured. (Hall et al., 1994) Except in cases of prohibitively high doses, neither ephedrine nor phenylephrine affects neonate status or blood acidities. The same was observed in the Edgbaston study for all the test groups.

A meta-analysis was conducted at the Chinese hospital of Hong Kong by Lee and co-workers. The researchers reviewed several studies that compared the relative efficacies of phenylephrine vs. ephedrine and found that there were no differences in the incidences of maternal hypotension. (Lee, Ngan Kee, & Gin, 2004) One important factor was that umbilical blood pH values for phenylephrine consistently trended towards being more basic. However, these numbers were well within acceptable limits. Ephedrine increases cardiac output and maintains blood pressure by increasing the heart rate. Phenylephrine which is an ?1-adrenoreceptor does not influence heart rates. Women from the phenylephrine group often became bradycardic (heart rates fell to less than 60 beats per minute).

Most of the studies thus far involve intravenous infusions of vasopressors. Intramuscular doses tend to be generally larger. Ayorinde and co-workers have studied the effects of intramuscular injections of either ephedrine or phenylephrine in different doses. These clinical trials were conducted to study the effectiveness of these vasopressors as preemptors in reducing maternal hypotension. The cohort in this study was divided into four groups -- the fourth group was the control and was only given a saline solution. The first and second groups were administered 4 and 2 mgs, respectively, of phenylephrine intramuscularly. The third group was given intramuscular injections of 45 mg of ephedrine. (Ayorinde et al., 2001) The medications were delivered immediately after the spinal anesthesia. The results are not as effective as intravenously delivered vasopressors. This is because they are not injected directly into the blood stream. Incidences of maternal hypotension were generally large, though the low concentration phenylephrine group and the control group showed almost seventy percent incidences of hypotension. In terms of relative incidences, the higher phenylephrine concentrations and the ephedrine group showed reduced hypotension presentations and lower need for rescue.

Combined

Researchers at the James Cook University Hospital in Cleveland attempted to recognize not only the relative efficacies of ephedrine vs. phenylephrine, but also sought to reduce the ephedrine dose and hence prevent fetal blood acidosis by combining ephedrine and phenylephrine. Fetal acidosis is determined by an umbilical blood pH of less than 7.2. The researchers divided the test cohort into three groups. The first group was given 100 micrograms/ml of phenylephrine. The second group was given 3 mg/ml of ephedrine and the third group was given a combination that included half the concentrations of ephedrine and phenylephrine of Groups I and II. Hemodynamic variables were measured with special emphasis on arterial pressure and umbilical blood pHs. (Cooper et al., 2002) The results revealed that the phenylephrine group and the mixed vasopressor group had better results for umbilical blood pHs. Only one of the phenylephrine and mixed groups had higher acidities in the umbilical blood versus 10 participants from the ephedrine group. In terms of maternal hypotension, neither of the subgroups presented any advantages. While the results for subjects in the mixed group did not vary significantly from the phenylephrine group, the researchers averred that phenylephrine was distinctly advantageous because there were less reports of nausea and vomiting in the mothers in that group than the mixed group.

In another study to identify the effects of combined ephedrine and phenylephrine vs. ephedrine alone, thirty-nine parturients participated in a study at the Hopital Antoine Beclere in France. One group was given 2mg/min of ephedrine and the second group was given a mixture of 2 mg/min of ephedrine plus 10 micrograms/mL of phenylephrine. The results of this study indicate that the mixture group suffered less incidences of maternal hypotension. (Mercier et al., 2001) The differences were 37% versus 75% for the ephedrine group. Both groups were prehydrated with a crystalloid preload. The infusions were continuous in order to maintain blood pressures at either 100 mg Hg or at 80% of the pre-anesthetic baselines. The amounts of ephedrine required in continuous infusion were also significantly larger in the ephedrine group than the mixed group.

Another study reveals the possible role of epinephrine in increasing cardiac performance following lowered venous returns. This study performed on more than 350 parturients. The cohort was divided into two groups and then further divided. The first division was based on whether the woman chose a vaginal delivery or a cesarean delivery. Each of these divisions was then divided whether the epidural was delivered by gravimetric flow or through an injection. Epinephrine was the medication of choice to prevent hypotension and it was combined in a single cocktail that was given with the epidural. All the other ingredients of this cocktail were typical of an epidural injection administered via a catheter. One might suppose that the gravimetric flow method was slower in terms of time of administration. But every hemodynamic variable measured was better for the gravimetric group. And this included incidences of hypotension. This study was conducted at the Robert Wood Johnson Medical School in New Jersey. (Cohen & Amar, 1997) study at the Chinese University of Hong Kong tested a vasopressor, metaraminol. Forty-five elderly patients involved with procedures for femur fractures were given either a colloidal preload, metaraminol or a combination of the two. (Critchley & Conway, 1996) The results indicated that there are significant advantages to this vasopressor in reducing post anesthetic hypotension. The mixed group performed the best in terms of restoration of baseline blood pressures. However, there are no studies for this drug in POSITIONING

There are different positions that are suggested during labor. These positions are recommended for two primary reasons: To ease the movement of the baby through the birth canal and to minimize discomfort to the mother.

Positioning is also seen as important in trying to reduce the ill effects of hypotension following emergency or elective cesarean sections using spinal or epidural anesthetics. Of the recommendations, lying down with a head tilt and slight feet elevation is used more often. Other recommendations include squatting (Islam et al., 2004)

While out of the scope of this particular work, it is important to recognize the results of a meta-analysis of several clinical trials that tested different outcomes of the standing vs. supine position during the second stage of birthing. The general consensus was that there was a standing position was preferred to the lying position. The authors of this meta-analysis however caution that one mode should not be preferred over the other at the cost of the would-be mother's comfort. The areas where the standing position proved advantageous were in the duration of labor, the need for a birth cushion and reduction in episiotomies and perineal tears. (Gupta & Nikodem, 2000) Women who opted for the standing position also identified with decreased pain and also a decreased need for assistance during delivery. The study, conducted at the University of Birmingham, UK revealed that the only disadvantage of the standing to the supine birthing technique was a greater loss of blood. This one disadvantage has a greater bearing on this thesis -- hypotension in parturients.

In trying to identify the best position following the administration of spinal, epidural or a combination anesthetic, a study revealed that the position during which the anesthetic is administered is also very important. The parturient can take the birthing position immediately after an injection of spinal anesthesia. In the case of an epidural however, there is a delay. This delay is because of the introduction of a catheter through which the epidural has to be delivered. In a combination anesthesia choice therefore, what position is appropriate is important. A study by Yun and co-workers at the Albert Einstein Medical College, New York, revealed that the administration of the combination anesthesia while sitting is detrimental to the lateral decubitus position. This latter position is also called lying on the side. (Yun, Marx, & Santos, 1998) The study tested the left lateral decubitus position because women involuntarily lie on the left side during pregnancy.

The women were given 1000ml of lactated Ringer's solution, which is also known as Hartmann's solution. This mixture is used for rehydrating in cases of trauma, and is often used for women before the birthing process can begin. Lactated Ringer's solution consists of Sodium chloride, sodium lactate (this is the lactate difference between the regular Ringer's solutions) and potassium chloride in distilled water. Between 300ml to a half liter of this solution was intravenously administered even as the combination spinal and epidural anesthesia was being administered. This cohort-group consisted of 22 women. Of these, 12 were administered the anesthesia in a sitting position, while 10 lay on their sides. Interestingly, enough incidents of hypotension were considerably greater in the group that was given CSE in the sitting position than the later decubitus position. Forty-seven percent of the former had problems with hypotension compared with 32% of the latter. Also, the amount of ephedrine given to correct the blood pressure to normal was twice as much as patients in the sitting position than those women that received the anesthesia while lying on their sides.

Post local anesthesia, there is a pooling of blood in the lower extremities with decrease in the pressure of venous blood return. Leg blood pressures were measured in women in late term pregnancies based on a supine position or a position with a left or right pelvic tilt. Doppler sound studies of several major arteries through the legs revealed that the arteries suffered no major compressions. But a chance from a tilt to a fully supine position was responsible for increased leg blood flow. The researchers at the University of London believed that this was due to the compression of the inferior vena cava. (Kinsella, Lee, & Spencer, 1990) change was not observed when the pelvic tilt changed from the left to the right side or vice versa. Fetal hemodynamics also did not change based on the positioning of the would-be mother. The researchers also concluded that more research needed to be done since their studies revealed that the pressure effects from positioning could not be adequately detected from leg pressure and Doppler studies.

A similar study at the University Of North Carolina Memorial Hospital agreed with the above conclusions. This study of 25 women revealed that a supine position vs. lateral tilts did not have any affect for two different angles, 5 and 10 degrees, on hemodynamic conditions of heart rate, blood pressure of the mother and the fetus. Perhaps because of confounding issues, the authors relented, that two of the patients had problems of hypotension. All the women were tested in all the positions. The two hypotension-presenting patients showed symptoms in the supine and 5-degree tilt positions. (Ellington et al., 1991) The authors concluded that these results were not conclusive. But they recommend a 10-degree or higher lateral tilt for all tests involving women in the later stages of pregnancies.

Sixty women that opted for cesarean birth were divided into two subgroups. Prior to the surgery, spinal anesthesia was applied. The first group received the injection in a position where the table was tilted at a 15-degree angle leftwards. The second group of 29 women (randomly assigned a sub-group designation) received the anesthesia in a fully left-lateral position. Apgar scores, arm arterial pressures and leg arterial pressures were measured for the group. The women in each subgroup were required to maintain their position for a full fifteen minutes after the administration of the anesthesia. (Rees et al., 2002) The hemodynamic variables measured showed no significant differences between the two subgroups. The singular difference was in the leg arterial pressure -- lower pressure for women in the tilt group. These differences were maintained for the duration during which the arterial pressures were measured. Women in both subgroups felt post-anesthesia symptoms such as nausea and vomiting equally.

Forty women participated in a clinical trial at the Bellshill maternity hospital in Lanarkshire. (Inglis, Daniel, & McGrady, 1995) The respondents were injected with anesthesia either in the sitting position or in the right lateral position. Then they were placed in the supine position with a left lateral tilt of 20 degrees. The onset of anesthesia was measured in different regions of the spine with variable results. The patients from the lateral group showed faster anesthetic onset time in the sixth vertebra. From the resulting hypotension however, the lateral group also required more ephedrine.

A comprehensive study to reveal the effect of positioning of maternal and fetal hemodynamics indicated that a lateral tilt of 20 degrees offered no statistically significant advantages. The confounders in this group were factors that necessitated the cesarean section. These cesareans were not elective. Fetal distress, one of the reasons for the emergency cesarean could have interfered with the statistical determinants of hemodynamics. The study was conducted for over 200 women. Approximately half were operated in the supine position. The other half was prescribed a leftward tilt of 20 degrees. The parameters that were measured were fetal heart rates, oxygen and carbon dioxide partial pressures and umbilical blood pH values. After birth evaluations revealed no differences in the hemodynamics for the mother or the babies. Fetal rates were minimally higher by approximately six beats per minute for the tilt cohort. But the researchers did not consider these to be statistically significant. The only hemodynamic parameter that can be considered significant was the fetal blood oxygen partial pressure, which was lower in the lateral tilt group, when compared to the supine group. None of the two hundred women in this cohort underwent elective cesareans. The problems presented by the patients range from "fetal distress and cephalo-pelvic disproportion to induction failure and abnormal presentations." (Matorras et al., 1998)

Positioning is important in the intermediate stages after the anesthetic is administered and before the cesarean surgery is performed. A cohort of 87 parturients was tested for hypotension after the CSE was administered. CSE was administered in the sitting position after 2 minutes spend in the right lateral position -- though the authors did not provide a rationale for this move. Each sub-group consisted of roughly half the number of respondents. The patients were studied in two positions: the supine position with a left 20-degree tilt, and in the full left lateral position. In the position for the study, the patients in the full lateral position showed lower incidences of hypotension. (Mendonca et al., 2003) In terms of percentages, it was approximately 64%, when compared to 90% of the supine cohort. In terms of the surgery however, even the left lateral group suffered the same hypotension problems as when their positions were adjusted to ready them for surgery. The left lateral position is significant in reducing hypotension. Even when ephedrine was given to correct for blood pressure problems, the left lateral group needed half the dosage of ephedrine as the supine group. This is an important consideration in terms of treating hypotension even after birthing.

Another study conducted at the Mount Sinai School of Medicine gives different results than the previous study. It recommends a leftward tilt of 30 degrees when compared to a full left lateral position. (Beilin et al., 2000) The study did not only compare relative hypotension but the efficacy of the action of the epidural. A catheter was first inserted into the patients. This test group consisted of 293 women in active labor. In the study positions, the women were given 13 ml of 0.25% bupivacaine. After fifteen minutes, the sensitivity of the women to typical pain-stimuli (pinprick in the lower extremities) was tested. More women from the later decubitus group needed additional anesthetic medication vs. those in the tilt group. In terms of maternal hemodynamics, there were no significant differences between the two groups. Even in representing symptoms of hypotension, there were no significant differences. The authors of the study do mention that more patients in the lateral decubitus group needed ephedrine to correct blood pressure. This study clearly shows the importance of positioning in administering anesthesia, though the conclusions based on presentations of hypotension might not be as conclusive.

The results of most of the studies reported thus far are concerned with the lower part of the body. Clinical trials conducted at the KK Women's and Children's Hospital in Singapore indicated that the position of head during administration of anesthetic was also very important from the incidence of hypotension and also from the amount of anesthesia required. Sixty women who chose to deliver via cesarean section were part of this study. One group of the test participants were administered the spinal anesthesia lying in a supine position with a right lateral tilt. (Loke, Chan, & Sia, 2002) The second group also lay in the same position. Except that the head was tilted up at 10 degrees. After the spinal block was given, all the patients were shifted to a left lateral position. The hemodynamic parameters for this group were measured at regular intervals until the second stage of labor was complete. 90 mm Hg was considered the threshold below which ephedrine was administered, every time.

The average systolic pressure for the horizontal group was 10 mm Hg lower than that for the head-tilt group, whose SAP mean was 109 m Hg. This sub-group also needed less concentrations of anesthesia. This study indicates that in addition to position of the body, head tilt should also be considered.

While the Singapore study concluded on the salubrious effects of the head-up tilt positioning reducing hypotension, a study at the University of Tsukuba in Japan concluded that a similar head-down tilt had no effect on hypotension when compared to a control group. The study included 34 parturients. The control and test subgroups were formed of 17 respondents each. Each patient was positioned horizontally, soon after which the test group's heads were tilted down by 10 degrees. (Miyabe & Sato, 1997) After an intravenous administration of lactated Ringer's solution, the patients were administered the spinal anesthetic. A wedge was placed under the patients' hips and a slight left lateral tilt was achieved to achieve left uterine displacement. The systolic arterial pressures were monitored. There were no significant differences in hemodynamic returns or hypotension presentations between the test and control groups. The lower threshold for blood pressure correction was set at 100 mm Hg. Ringer's lactate and ephedrine was given to combat hypotension. There were no differences in the amounts of pressure correction interventions between the two groups.