You will be provided with the titles and abstracts of a collection of medical RCT reports studying a clinical question -- for instance, the efficacy of an intervention on some medical outcome. Please write a few sentences synthesizing the findings of these reports, which could serve as a conclusion section for a systematic review article. Your response should not include any other text. The RCT reports are below.



Title 1:
Lumbar wedge versus pelvic wedge in preventing hypotension following combined spinal epidural anaesthesia for caesarean delivery.
Abstract 1:
Aortocaval compression is a major cause of maternal hypotension. A randomised controlled clinical trial was designed to compare two wedged supine positions for prevention of hypotension following combined spinal epidural anaesthesia for caesarean delivery. Sixty parturients undergoing elective caesarean delivery were randomly assigned to two different wedged supine positions. After the completion of subarachnoid injection, parturients were placed with either a wedge under the right pelvis (group P pelvic wedge) or under the right lumbar region (group L, lumbar wedge). Systolic blood pressure and heart rate were recorded every minute for 20 minutes from the subarachnoid injection. Hypotension, defined as systolic blood pressure <100 mmHg or 80% of the baseline, was treated with intravenous ephedrine 5 mg. The incidence of hypotension, ephedrine use and neonatal Apgar scores and umbilical arterial pH were recorded. The incidence of hypotension was significantly higher in group P than that in group L (23/30 [77%] vs. 14/30 [47%], P=0.016). Systolic blood pressure decreased significantly in both groups at seven, eight and nine minutes (P < 0.001); moreover it was lower at seven, eight and nine minutes in group P than in group L (P < 0.01). Heart rate did not change significantly in either group. There were no significant differences between the two groups for Apgar score and umbilical arterial pH. A lumbar wedge is more effective than a pelvic wedge in preventing hypotension following combined spinal epidural anaesthesia for caesarean delivery, although it does not eliminate hypotension.


Title 2:
Lack of benefits of left tilt in emergent cesarean sections: a randomized study of cardiotocography, cord acid-base status and other parameters of the mother and the fetus.
Abstract 2:
To assess the benefits of performing the cesarean section in lateral tilt during active labor.
                University Hospital.
                204 unselected women undergoing cesarean section (21.1% fetal distress, 45.6% cephalo-pelvic disproportion, 26.0% induction failure, 7.4% abnormal presentation) under general (86.8%) or spinal anesthesia (13.2%).
                Randomized study.
                During anesthesia induction and cesarean section 103 women were in partial left lateralization (20 degrees), whereas the remaining 101 remained in the supine position.
                Internal cardiotocography during cesarean section. Umbilical artery acid-base analysis. Newborn evaluation. Maternal hemodynamic parameters.
                Fetal heart rate during cesarean section was similar in both groups, except for a baseline heart rate which was slightly higher in the lateral tilt group (137.5 +/- 19.2 vs 131.1 +/- 20). The umbilical artery pH values, as well as pCO2, base deficit, CO3H and oxygen saturation were similar in both groups. The pO2 value was significantly lower in the lateral tilt group (14.03 +/- 6.04 Hg mm vs 16.02 +/- 7.65). Newborn evaluation was similar in both groups. The blood pressure and heart rate of the mother during the cesarean section were also similar in both groups.
                No benefits were found in performing cesarean section in left lateral tilt.


Title 3:
Manual displacement of the uterus during Caesarean section.
Abstract 3:
Ninety ASA 1 and 2 pregnant women with term singleton pregnancies and no maternal and fetal complications, scheduled for elective or emergency Caesarean section, were randomly allocated to group LT (15 degrees left lateral table tilt, n = 45) and group MD (leftward manual displacement, n = 45). Subarachnoid block was established with a 25-gauge spinal needle at the L3-L4 interspace using 1.5 ml of 0.5% hyperbaric bupivacaine. A median sensory level of T6 was observed in both groups but the incidence of hypotension was markedly lower in group MD when compared to group LT (4.4% vs 40%; p < 0.001) with a significant reduction in mean (SD) ephedrine requirement (6 (0) vs 11.3 (4.9) mg; p < 0.001). The mean (SD) fall in systolic blood pressure was 28.8 (7.3) mmHg in group LT and 20 (12.7) mmHg in group MD. The time to maximum fall in systolic blood pressure was similar in both groups (4.5 min). We conclude that manual displacement of the uterus effectively reduces the incidence of hypotension and ephedrine requirements when compared to 15 degrees left lateral table tilt in parturients undergoing Caesarean section.


Title 4:
Hemodynamic effects of a right lumbar-pelvic wedge during spinal anesthesia for cesarean section.
Abstract 4:
Aortocaval compression is a major cause of maternal hypotension. A randomized controlled trial was designed to determine the effectiveness of a mechanical intervention using a right lumbar-pelvic wedge in preventing hypotension after spinal anesthesia for cesarean delivery.
                Eighty healthy women undergoing elective cesarean section were randomly allocated immediately after spinal blockade to either a lumbar-pelvic wedge positioned under the right posterior-superior iliac crest (Wedge group, n=40) or the complete supine position (Supine group, n=40). Hemodynamic values, vasopressor consumption and adverse effects were collected during the surgical procedure. Hypotension was defined as a reduction in systolic blood pressure of 25% from baseline. Patient allocation, management and data collection were performed by a single unblinded anesthetist.
                There was no difference in the incidence of hypotension between the two groups (42.5% vs. 50%, P=0.51). During the first 5 min, blood pressure decreased less in the Wedge group. There were significant differences in median [interquartile range] vasopressor requirements between the Wedge group and the Supine group (1 [0-2] vs. 3 [1-4] mg, P<0.01) and in nausea during the procedure (6 vs. 22 patients, P<0.01).
                In our study population the use of right lumbar-pelvic wedge was not effective in reducing the incidence of hypotension during spinal anesthesia for cesarean section. Patients in whom the wedge was used had higher systolic blood pressure values during the first 5 min of anesthesia and fewer episodes of nausea. The risk of hypotension remains substantial.
                Copyright © 2011 Elsevier Ltd. All rights reserved.


Title 5:
Incidence of venous air embolism during cesarean section is unchanged by the use of a 5 to 10 degree head-up tilt.
Abstract 5:
One hundred healthy parturients were divided at random into two demographically similar groups and were positioned for cesarean section either horizontally or flexed 5 to 10 degrees head up, with a 15 degrees lateral tilt. A Doppler ultrasound transducer was positioned over the fourth intercostal space parasternally. Initially, two patients received spinal, three general, and 95 epidural anesthesia. Two patients subsequently needed general for failed epidural anesthesia. Changes in Doppler heart tones (greater than 15 sec duration) indicative of venous air embolism (VAE) were identified 15 times in 11 patients--seven in supine and four in head-up patients (no statistically significant difference). Six awake patients (three horizontal, three head-up) developed chest tightness or pain during surgery, but only one episode correlated with VAE. No patient developed breathlessness. Moderate hypotension (greater than 10% decrease in systolic arterial pressure [SAP]) occurred in seven of 11 (63.6%) patients with, and in 26 (29.2%) of 89 patients without, VAE (P less than 0.001). More severe hypotension (SAP less than 90 mm Hg) due to bleeding occurred once. We conclude that a modest (5-10 degrees) head-up position does not influence the occurrence of VAE in patients having cesarean section. An 11% incidence of clinically insignificant VAE, although low, is still worrisome, as even small air bubbles in the circulation are potentially harmful, especially if the foramen ovale is patent. VAE during cesarean section should be anticipated and the anesthetic management planned accordingly.


Title 6:
Maternal cardiovascular consequences of positioning after spinal anaesthesia for Caesarean section: left 15 degree table tilt vs. left lateral.
Abstract 6:
Sixty healthy women undergoing elective Caesarean section were randomly allocated to either a measured 15 degrees left table tilt position (n = 31) or full left lateral position (n = 29) for a 15-min period after spinal blockade. Arm and leg blood pressure, ephedrine requirements, symptoms, fetal heart rate, cord gases and Apgar scores were recorded. Mean ephedrine requirements and incidence of hypotension were similar in the two groups. Arm systolic arterial pressure over time was similar in both groups, but leg systolic arterial pressure over time was significantly lower in the tilt group (p < 0.001); the mean leg systolic arterial pressure was lower for all 15 sequential recordings in the tilt group, reaching statistical significance (p < 0.05) at 4, 5, 6 and 8 min. Differences in maternal nausea, vomiting and bradycardia and fetal outcome were not statistically significant. Following spinal anaesthesia, even a true 15 degrees left table tilt position is associated with aortic compression.


Title 7:
Advantages of left over right lateral tilt for caesarean section.
Abstract 7:
The relative merits of right and left lateral tilt were assessed in 75 parturients at elective caesarean section. Significant maternal hypotension (aortocaval occlusion) occurred more frequently with rightward tilt (left hip supported). The clinical and biochemical status of the fetus was generally more favourable with left lateral tilt, as were the maternal-to-fetal blood gas gradients and relationships. The routine use of left lateral tilt is advocated.


Title 8:
The effect of head-down tilt position on arterial blood pressure after spinal anesthesia for cesarean delivery.
Abstract 8:
The effect of the head-down tilt position after induction of spinal anesthesia for cesarean delivery on blood pressure and level of sensory block was examined.
                Patients were allocated randomly into two groups, the head-down tilt group (n = 17) and the horizontal group (n = 17). In the head-down tilt group, patients were positioned with a 10 degrees head-down tilt immediately after supine positioning, while those in the horizontal group were maintained in a horizontal position. All patients received 500 mL of lactated Ringer's solution intravenously over 10 minutes prior to spinal injection, a wedge was placed under the patient's right hip, and the operating table was rotated 5 degrees in a counterclockwise direction to provide left uterine displacement. Hypotension (defined as systolic blood pressure below 100 mm Hg) was treated with 5 mg ephedrine intravenously and an increase in the infusion rate of lactated Ringer's solution. The change in systolic blood pressure was expressed as percent change from the baseline value.
                Systolic blood pressure decreased 20% at 3 minutes after spinal block in both groups but recovered to half of this decrease. The incidence of postspinal hypotension was not different between the two groups. The total amount of ephedrine and lactated Ringer's solution administered during the first 20 minutes of spinal block did not differ between the two groups nor did the extent of the cephalad spread of analgesia 20 minutes after spinal block (T4 +/- 2 vs T4 +/- 1 for the head-down and horizontal groups, respectively).
                The head-down position is concluded to have no effect on the incidence of hypotension during spinal anesthesia for cesarean delivery.
There is limited evidence to support or clearly disprove the value of the use of tilting or flexing the table, the use of wedges and cushions or the use of mechanical displacers. A left lateral tilt may be better than a right lateral tilt and manual displacers may be better than a left lateral tilt but larger studies with more robust data are needed to confirm these findings.