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…