The effect of intravenous ondansetron on maternal haemodynamics during elective caesarean delivery under spinal anaesthesia: a double-blind,randomised, placebo-controlled trial

BackgroundSpinal anaesthesia for caesarean delivery is frequently associated with adverse effects such as maternal hypotension and bradycardia. Prophylactic administration of ondansetron has been reported to provide a protective effect. We studied the effect of different doses of ondansetron in obstetric patients.MethodsThis prospective double-blind, randomised, placebo-controlled study included 128 healthy pregnant women scheduled for elective caesarean delivery under spinal anaesthesia. Women were randomly allocated into four groups (n = 32) to receive either placebo or ondansetron 2, 4 or 8 mg intravenously before induction of spinal anaesthesia. Demographic, obstetric, intraoperative timing and anaesthetic variables were assessed at 16 time points. Anaesthetic variables assessed included blood pressure, heart rate, oxygen saturation, nausea, vomiting, electrocardiographic changes, skin flushing, discomfort or pruritus and vasopressor requirements.ResultsThere were no differences in the number of patients with hypotension in the placebo (43.8%) and ondansetron 2 mg (53.1%), 4 mg (56.3%) and 8 mg (53.1%) groups (P = 0.77), nor the percentage of time points with systolic hypotension (7.3% in the placebo group and 11.1%, 15.7% and 12.6% in the ondansetron 2, 4 and 8 mg groups, respectively, P = 0.32). There were no differences between groups in ephedrine (P = 0.11) or phenylephrine (P = 0.89) requirements and the number of patients with adverse effects.ConclusionsIn our study, prophylactic ondansetron had little effect on the incidence of hypotension in healthy parturients undergoing spinal anaesthesia with bupivacaine and fentanyl for elective caesarean delivery.     

Comparison of the potency of phenylephrine and norepinephrine bolus doses used to treat post-spinal hypotension during elective caesarean section

BackgroundPhenylephrine, although considered the vasopressor of choice, can cause reflex bradycardia and a fall in cardiac output. Norepinephrine, due to its direct positive chronotropic and reflex negative chronotropic actions, is expected to overcome this problem. However, limited information about its effective dose for management of post-spinal hypotension, and its potency compared to phenylephrine, is available.MethodsOne hundred consecutive patients who developed post-spinal hypotension were treated with a predetermined dose of either phenylephrine or norepinephrine. Correction of hypotension after one minute was considered ‘success’. The starting dose for the first patient and testing interval (the incremental or decremental dosing) were 100 μg and 10 μg in the phenylephrine group, and 6 μg and 0.5 μg in the norepinephrine group. Doses for subsequent patients were determined by the responses of previous patients according to the Narayana rule for up-down sequential allocation. ED95 and ED50 of phenylephrine and norepinephrine boluses and their potency ratio were calculated.ResultsUsing Probit analysis, ED95 and ED50 values were 43.1 µg (95% CI 39.5 to 65.0 µg) and 33.2 µg (95% CI 5.1 to 37.0 µg) for phenylephrine, and 3.7 µg (95% CI 3.5 to 4.7 µg) and 3.2 µg (95% CI 1.8 to 3.4 µg) for norepinephrine. The relative potency ratio of norepinephrine and phenylephrine was 11.3 (95% CI 8.1 to 16.9).ConclusionBased on the results of this study, norepinephrine is about 11 times more potent than phenylephrine. When used as bolus doses for treatment of hypotension, 100 μg phenylephrine should be approximately equivalent to 9 μg norepinephrine.     

Association of renin-angiotensin-aldosterone system genetic polymorphisms with maternal hypotension during spinal anaesthesia for caesarean delivery: a retrospective cohort study

BackgroundUnless prevented, hypotension occurs in up to 80% of normotensive women undergoing spinal anaesthesia for caesarean delivery. Renin-angiotensin-aldosterone system genetic polymorphisms have been associated with hypertensive disease, but few studies investigated effects on blood pressure regulation under spinal anaesthesia. We postulated that these polymorphisms increased vasodilation and maternal hypotension during spinal anaesthesia.MethodsA retrospective secondary analysis of data from four prospective trials with similar inclusion/exclusion criteria evaluating phenylephrine/ephedrine delivery systems during spinal anaesthesia for elective caesarean delivery. Angiotensin type-1 receptor (AT1R) (A1166C), angiotensin-converting enzyme (ACE) (I/D), and aldosterone synthase CYP11B2 (C344T) polymorphisms were identified from stored specimens. The associations between the polymorphisms and hypotension (systolic blood pressure <80% of baseline), and vasopressor use, were determined by univariable and multivariable regression.ResultsOf 556 patients, 378 (68.0%) had hypotension. The AC/CC genotypes of AT1R (A1166C) were associated with hypotension by univariable analysis (OR 2.70, 95% CI 1.38 to 5.28, P=0.004]) and multivariable analysis (OR 3.65, [95% CI 1.68 to 7.94, P=0.004]) after adjustment for age, race, intravenous fluid volume, and block height. No difference in vasopressor use or adverse maternal or fetal outcomes were noted. Baseline characteristics were similar, with the exception of higher baseline blood pressure, block height, and intravenous fluid volume in the hypotensive group. There was no significant association between ACE and CYP11B2 polymorphisms and hypotension.ConclusionAC/CC genotypes of AT1R (A1166C) polymorphism were associated with maternal hypotension under spinal anaesthesia for caesarean delivery. An association with cardiovascular indices and high-risk parturients should be examined.     

An open-label randomized controlled clinical trial for comparison of continuous phenylephrine versus norepinephrine infusion in prevention of spinal hypotension during cesarean delivery

BackgroundDuring spinal anesthesia for cesarean delivery phenylephrine is the vasopressor of choice but can cause bradycardia. Norepinephrine has both β- and α-adrenergic activity suitable for maintaining blood pressure with less bradycardia. We hypothesized that norepinephrine would be superior to phenylephrine, requiring fewer rescue bolus interventions to maintain blood pressure.MethodsEighty-five parturients having spinal anesthesia for elective cesarean delivery were randomized to Group P (phenylephrine 0.1 μg/kg/min) or Group N (norepinephrine 0.05 μg/kg/min) fixed-rate infusions. Rescue bolus interventions of phenylephrine 100 μg for hypotension, or ephedrine 5 mg for bradycardia with hypotension, were given as required to maintain systolic blood pressure. Maternal hemodynamic variables were measured non-invasively.ResultsThere was no difference between groups in the proportion of patients who required rescue vasopressor boluses (Group P: 65.8% [n=25] vs. Group N: 48.8% [n=21], P=0.12). The proportion of patients who received ⩾1 bolus of phenylephrine was similar between groups (Group P: 52.6% [n=20] vs. Group N: 46.5% [n=20], P=0.58). However, more patients received ⩾1 bolus of ephedrine in the phenylephrine group (Group P: 23.7% [n=9] vs. Group N: 2.3% [n=1], P <0.01). The incidence of emesis was greater in the phenylephrine group (Group P: 26.3% vs. Group P: 16.3%, P <0.001). Hemodynamic parameters including heart rate, the incidence of bradycardia, blood pressure, cardiac output, cardiac index, stroke volume, and systemic vascular resistance and neonatal outcome were similar between groups (all P <0.05).ConclusionNorepinephrine fixed-rate infusion has efficacy for preventing hypotension and can be considered as an alternative to phenylephrine.     

Haemodynamic effects of glycopyrrolate pre-treatment before phenylephrine infusion during spinal anaesthesia for caesarean delivery

BackgroundPhenylephrine given during spinal anaesthesia for caesarean delivery often induces a decrease in heart rate which may decrease cardiac output. Anticholinergic drugs may be given to attenuate this effect but may also cause more labile blood pressure. This study evaluated the effects of glycopyrrolate pre-treatment on non-invasively measured cardiac output and accuracy of blood pressure control.MethodsAt induction of spinal anaesthesia for caesarean delivery, 104 patients randomly received intravenous glycopyrrolate 4 μg/kg or saline placebo. Systolic blood pressure, measured at 1-min intervals, was maintained near baseline using closed-loop feedback computer-controlled phenylephrine infusion with crystalloid cohydration. Cardiac output and stroke volume were measured using suprasternal Doppler ultrasonography at baseline and 5-min intervals for 20 min. Blood pressure control was assessed using performance error calculations.ResultsEleven patients were excluded. Patients who received glycopyrrolate (n = 45) had greater cardiac output over time (P < 0.001), greater heart rate over time (P < 0.001), similar stroke volume over time (P = 0.95), and lower median phenylephrine infusion rate (P = 0.006) compared with control (n = 48). There was no difference in the incidence of hypotension between groups. Analysis of blood pressure control showed greater positive bias, greater inaccuracy and greater wobble in the glycopyrrolate group (all P < 0.05). Neonatal outcome was similar between groups.ConclusionsGlycopyrrolate 4 μg/kg given at the start of a phenylephrine infusion increased heart rate and cardiac output but also decreased accuracy of blood pressure control, increased the incidence of hypertension and caused an increased incidence of dry mouth postoperatively compared with control.     

Neonatal outcomes following phenylephrine or norepinephrine for treatment of spinal anaesthesia-induced hypotension at emergency caesarean section in women with fetal compromise: a randomised controlled study

BackgroundNorepinephrine is as effective as phenylephrine for management of spinal anaesthesia-induced hypotension. Most of the studies comparing these vasopressors have been conducted in healthy pregnant women undergoing elective caesarean section. In the current study, we tested the null hypothesis that there is no difference in neonatal outcome when phenylephrine or norepinephrine is used to treat spinal anaesthesia-induced hypotension in women undergoing emergency caesarean section for fetal compromise.MethodsPatients undergoing caesarean section for fetal compromise who developed spinal anaesthesia-induced hypotension were randomised to receive phenylephrine 100 μg or norepinephrine 8 μg for treatment of each hypotensive episode, defined as systolic blood pressure <100 mmHg. Umbilical cord arterial and venous blood samples were obtained for blood gas analysis. The primary outcome measure was umbilical artery pH.ResultsOne hundred patients (50 in each group) were studied. There was no significant difference in umbilical artery pH between the two groups (mean difference 0.001; 95% CI −0.032 to 0.034). The number of hypotensive episodes, vasopressor boluses required, the incidence of bradycardia, heart rate and blood pressure trends following vasopressor administration, and the incidence of nausea/vomiting were not significantly different between groups.ConclusionPhenylephrine 100 μg and norepinephrine 8 μg were not significantly different in terms of neonatal outcome when administered as intravenous boluses for treatment of spinal anaesthesia-induced hypotension in parturients undergoing emergency caesarean sections for fetal compromise.     

Ultrasound to identify the lumbar space in women with impalpable bony landmarks presenting for elective caesarean delivery under spinal anaesthesia: a randomised trial

BackgroundUltrasound can facilitate neuraxial blockade in patients with poorly defined anatomical surface landmarks, but there are no studies comparing an ultrasound-guided technique with landmark palpation for spinal anaesthesia. The objective of this study was to compare pre-procedural lumbar ultrasonography with landmark palpation to locate the needle insertion point in women with impalpable lumbar spinous processes presenting for caesarean delivery.MethodsAfter institutional ethics committee approval, 20 women with impalpable lumbar spinous processes presenting for elective caesarean delivery were recruited. Patients were randomised to palpation or ultrasound. The primary outcome of the study was the number of needle passes to achieve lumbar puncture. Secondary outcomes were the overall procedural time and patient satisfaction score.ResultsThere was no difference in mean (±SD) body mass index of both groups (ultrasound 39.1 ± 5.02 kg/m² vs. palpation 38.3 ± 3.77 kg/m²). There were significantly fewer needle passes in the ultrasound group (median 3 [IQR 1.8–3.2]) compared to the palpation group (median 5.5 [IQR 3.2–7.2] (P=0.03)). More time was required to locate the needle insertion point in the ultrasound group (ultrasound 91.8 ± 30.8 s vs. palpation 32.6 ± 11.4 s, P <0.001). There was no difference in the total procedural time between groups (ultrasound 191.8 ± 49.4 s vs. palpation 192 ± 110.9 s, P=0.99).ConclusionThe use of ultrasonography to locate the needle insertion point reduced the number of needle passes in women with impalpable lumbar spinous processes undergoing elective caesarean delivery under spinal anaesthesia. Its use did not prolong overall procedural time.     

Pre-operative carbohydrate loading prior to elective caesarean delivery: a randomised controlled trial

IntroductionWomen undergoing elective caesarean deliveries are fasted for long periods prior to surgery and can become catabolic. The use of pre-operative carbohydrate drinks to optimise patients ahead of major surgery is now well established. However, evidence to support this in women undergoing elective caesarean delivery is limited.MethodsWe conducted a single-blind randomised control trial to study the effect of carbohydrate preloading on the presence of urinary ketones in mothers undergoing elective caesarean deliveries compared with standard care, fasting from midnight the night before surgery with free clear fluids until two hours prior to surgery.ResultsTwo-hundred-and-nine patients were allocated to either standard care (n=104) or pre-operative carbohydrate drinks (n=105) prior to elective caesarean section. Twenty-five were excluded from the analysis, leaving 184 (n=90; n=94). The incidence of urinary ketones immediately prior to surgery was lower in the carbohydrate group, 18.1% compared with 61.1% in the standard care group (P<0.001). Relative risk (95% CI) 3.33 (2.12 to 5.26), with a number needed-to-treat of three to prevent urinary ketosis in one woman. There were no major adverse events.ConclusionThe results of this study support the introduction of carbohydrate drinks ahead of caesarean delivery to offset the effects of pre-operative fasting. However, the results may not be generalisable to all maternity units due to differences in fasting protocols.     

Ephedrine versus ondansetron in the prevention of hypotension during cesarean delivery: a randomized,double-blind,placebo-controlled trial

BackgroundMaternal hypotension is common after spinal anesthesia for cesarean delivery. We compared the effects of prophylactic ephedrine with ondansetron on post-spinal blood pressure.MethodsOne hundred and sixty-eight term, singleton parturients were enrolled in this prospective, double-blind, placebo-controlled trial. Patients were randomized to receive either prophylactic intravenous ephedrine 10 mg (Group E), ondansetron 8 mg (Group O) or normal saline (Group P) immediately after spinal anesthesia. The primary outcome was maternal blood pressure between spinal block and delivery; secondary outcomes were nausea and vomiting scores, Apgar scores, numbers requiring intraoperative vasoconstrictors and the dose of vasoconstrictors required.ResultsFifty-six patients were recruited to each group, but two in Group P were excluded from the analysis owing to protocol violations. There were no significant differences between the groups in maternal systolic, diastolic or mean arterial pressures, or the proportion of patients experiencing hypotension. The proportion of patients in Group E requiring intraoperative ephedrine or any vasoconstrictor (ephedrine and/or norepinephrine) was significantly lower than that in Group P (P=0.023 and 0.034, respectively). The proportion of patients in Group O requiring intraoperative norepinephrine was significantly lower than that in Group P (P=0.02). There was no difference in the proportions of patients in Groups E and O requiring any vasoconstrictors (P=0.34).ConclusionsThere was no significant difference in maternal blood pressure in women administered prophylactic ephedrine or ondansetron after spinal anesthesia for cesarean delivery compared with placebo. Ephedrine reduced the proportion of patients requiring a rescue vasoconstrictor before delivery.     

A randomised controlled trial of phenylephrine and noradrenaline boluses for treatment of postspinal hypotension during elective caesarean section

Phenylephrine is currently the vasopressor of choice during elective caesarean section, but it can cause reflex bradycardia. Noradrenaline, a potent α-agonist and weak β-agonist, may be associated with a lower incidence of bradycardia. However, comparative information is limited. This double-blind randomised controlled trial compared the effects of 100 μg phenylephrine and 5 μg noradrenaline administered as boluses for the treatment of postspinal hypotension during elective caesarean section in women with an uncomplicated singleton pregnancy. Hypotension was defined as a decrease of ≥ 20% from baseline systolic arterial pressure, or an absolute value < 100 mmHg. Ninety women were included in the study. The primary outcome was the incidence of maternal bradycardia < 60 beats.min⁻¹. There was no difference in the incidence of bradycardia (37.8% with phenylephrine vs. 22.2% with noradrenaline; p = 0.167), number of hypotensive episodes, number of boluses required to treat the first hypotensive episode or reactive hypertension. The total number of boluses used was higher in the phenylephrine group (p = 0.01). Maternal heart rate at 1 min after vasopressor administration was non-significantly lower using phenylephrine vs. noradrenaline (p = 0.034, considering p < 0.01 as statistically significant). The umbilical artery pH was higher using phenylephrine than with noradrenaline (p = 0.034). In conclusion, both vasopressors reversed postspinal hypotension without a statistically significant difference in maternal bradycardia. However, in view of the lower umbilical artery pH when using noradrenaline, further research is warranted to study its placental transfer and fetal metabolic effects.     

Analgesic effects of intrathecal tramadol in patients undergoing caesarean section: a randomised,double-blind study

BackgroundIntrathecal tramadol combined with local anaesthetics has been used for postoperative analgesia following lower abdominal and perineal surgery. The present study evaluated the effect of intrathecal tramadol on spinal block characteristics and neonatal outcome after elective caesarean section.MethodsEighty full-term parturients scheduled for elective caesarean section were randomly divided into two groups. In the fentanyl group, patients received intrathecal 0.5% bupivacaine 10 mg with fentanyl 10 μg; in the tramadol group, patients were given the same dose of bupivacaine with tramadol 10 mg. Sensory and motor block characteristics, duration of postoperative analgesia, maternal side effects, and neonatal outcome were compared.ResultsOne patient in the tramadol group and two patients in the fentanyl group were excluded from data analysis. Median [interquartile range] duration of postoperative analgesia in the tramadol and the fentanyl groups was 300 [240–360] min and 260 [233–300] min respectively (P = 0.02). The incidence of shivering was lower in patients who received tramadol (5%) than those who had fentanyl (32%) (P = 0.003). Apgar scores, umbilical cord acid–base measurement and neurologic and adaptive capacity scores were comparable between the two groups.ConclusionCompared to intrathecal fentanyl 10 μg, tramadol 10 mg, as an adjunct to bupivacaine for subarachnoid block for caesarean section, showed a longer duration of analgesia with a reduced incidence of shivering.     

A randomised controlled trial of the effect of a head-elevation pillow on intrathecal local anaesthetic spread in caesarean section

BackgroundA head-elevation pillow places a patient in a ramped posture, which maximises the view of the larynx during laryngoscopy, particularly in obese parturients. In our institution an elevation pillow is used pre-emptively for neuraxial anaesthesia. We hypothesised that head-elevation may impair cephalad spread of local anaesthetic before caesarean section resulting in a lower block or longer time to achieve a T6 level. We aimed to investigate the effect of head-elevation on spread of intrathecal local anaesthetics during anaesthesia for caesarean section.MethodsOne-hundred parturients presenting for caesarean section under combined spinal-epidural anaesthesia were randomised to either the standard supine position with lateral displacement or in the supine position with lateral displacement on an head-elevation pillow. Each patient received intrathecal hyperbaric bupivacaine 11 mg, morphine 100 μg and fentanyl 15 μg. Patients were assessed for adequacy of sensory block (T6 or higher) at 10 min.ResultsSensory block to T6 was achieved within 10 min in 65.9% of parturients in the Elevation Pillow Group compared to 95.7% in the Control Group (P<0.05). Compared to the Control Group, patients in the Elevation Pillow Group had greater requirements for epidural supplementation (43.5% vs 2.1%, P<0.001) or conversion to general anaesthesia (9.3% vs 0%, P<0.04).ConclusionsUse of a ramped position with an head-elevation pillow following injection of the intrathecal component of a combined spinal-epidural anaesthetic for scheduled caesarean section was associated with a significantly lower block height at 10 min.     

A prospective observational study of the change in regional cerebral oxygen saturation during cesarean delivery in women receiving phenylephrine prophylaxis for spinal hypotension

BackgroundSpinal hypotension causes decreased regional cerebral oxygen saturation (ScO₂) in women undergoing cesarean delivery. In this study we aimed to measure the change in ScO₂ using near infrared spectroscopy in women receiving a prophylactic phenylephrine infusion during cesarean delivery under spinal anesthesia.MethodsThis was a prospective, observational cohort study. Fifty-three women had ScO₂ measurements at the following time points: preoperatively, in the supine position with 30° of left lateral tilt; one and five minutes after spinal anesthesia; at the time of skin incision; immediately after delivery; one minute after commencing the oxytocin infusion; at completion of surgery, and one hour after surgery. Spinal anesthesia and a prophylactic phenylephrine infusion were administered according to a standard treatment protocol. Statistical analysis used the Wilcoxon Signed Rank test with Bonferroni’s correction for multiple comparisons.ResultsBlood pressure was maintained within 20% of baseline throughout surgery. The baseline mean (range) ScO₂ was 61.5% (54.0–66.3%). It decreased significantly at all subsequent measurement points. The maximum decrease was five minutes after spinal anesthesia. Thirty-four (64.2%) of the parturients exhibited ScO₂ values <20% of baseline, or a decrease to below an absolute value of 50%. There was no significant correlation between systolic blood pressure and mean ScO₂.ConclusionSpinal anesthesia with phenylephrine infusion during cesarean delivery is associated with a significant decrease in ScO₂ levels, maximal five minutes later. Further studies are required to establish the clinical significance of this finding.     

Comparison of nalbuphine,ondansetron and placebo for the prevention of shivering after spinal anaesthesia for urgent caesarean delivery: a randomised double-blind controlled clinical trial

BackgroundShivering is a common complication of caesarean delivery with neuraxial anaesthesia. The effective prevention and treatment of shivering, especially before delivery, is important and difficult. We tested the hypothesis that prophylactic nalbuphine and ondansetron can prevent post-spinal anaesthesia shivering in parturients undergoing urgent caesarean delivery.MethodsSixty parturients scheduled for urgent caesarean delivery before spinal anaesthesia were selected and divided randomly into three groups. After peripheral venous catheterisation, parturients were given intravenous nalbuphine 0.08 mg/kg (group N), ondansetron 8 mg (group O), or normal saline (group C).ResultsThe incidence of shivering and of severe (grade ≥3) shivering was significantly lower in group N (15% and 15%, respectively) than in group C (80% and 65%) before delivery (P <0.001 and P=0.003); and significantly less shivering was observed in group N than in group C in the first 30 min after anaesthesia (P=0.001). Up to 60 min after anaesthesia, the incidence of grade ≥3 shivering remained lowest in group N (P=0.003). According to the data during the period from anaesthesia until delivery, the number needed-to-treat for nalbuphine was 1.54 (95%CI 1.13 to 2.41). No significant differences were found between groups O and N or groups O and C at any time. The incidence of dizziness in group N was significantly higher than that of groups O or C (P=0.009).ConclusionNalbuphine 0.08 mg/kg can prevent post-spinal anaesthesia shivering in parturients undergoing urgent caesarean delivery but causes transient dizziness, while ondansetron 8 mg had no significant effect.     

Serum oxytocin concentrations in elective caesarean delivery: a randomized comparison of three infusion regimens

Background

The aim of this study was to determine serum oxytocin concentrations following different regimens of prophylactic oxytocin administration in women undergoing elective caesarean delivery.

Methods

Thirty healthy pregnant patients were randomized, after clamping of the umbilical cord, to receive intravenous oxytocin in one of the following groups: G1 (n = 9), 10 IU of oxytocin infused over 30 min (0.33 IU/min); G2 (n = 11), 10 IU of oxytocin infused over 3 min and 45 s (2.67 IU/min); and G3 (n = 10), 80 IU of oxytocin infused over 30 min (2.67 IU/min). Both patient and surgeon were blinded to allocation. Uterine tone was assessed by surgical palpation. Serum oxytocin concentration was determined by enzyme immunoassay before anaesthesia (T0) and at 5 (T5), 30 (T30) and 60 (T60) min after the start of oxytocin infusion.

Results

Serum oxytocin concentrations (mean ± standard error, ng/mL) were not significantly different in the groups at T0 (0.06±0.02, 0.04±0.02 and 0.07±0.04, respectively, P = 0.76), and T60 (0.65±0.26, 0.36±0.26 and 0.69±0.26, respectively, P = 0.58). G3 showed higher concentrations than G1 at T5 (3.65±0.74 versus 0.71±0.27, P = 0.01) and at T30 (6.19±1.19 versus 1.17±0.37, P < 0.01), and were higher than G2 at T30 (6.19±1.19 versus 0.41±0.2, P < 0.01). Haemodynamic data and uterine tone were considered satisfactory and similar in all groups. No additional uterotonic agents were needed.

Conclusion

Serum oxytocin measurements made using enzyme immunoassay in healthy pregnant women undergoing elective caesarean delivery showed that administration of 80 IU oxytocin over 30 min resulted in higher serum oxytocin levels after 5 and 30 min than the two other regimens. The concentrations did not differ between groups at 60 min.     

Intra-operative fluid warming in elective caesarean section: a blinded randomised controlled trial

BackgroundWe assessed the effect of warming intravenous fluids during elective caesarean section under combined spinal-epidural anaesthesia in a blinded, randomised controlled trial.MethodSeventy-five women having elective caesarean section were randomly assigned to receive all intravenous fluids at room temperature, or heated in a cabinet set at 45°C or via a Hotline^® fluid warmer (Smiths Medical International Ltd, Watford, Herts, UK). After 10 mL/kg crystalloid preload, combined spinal-epidural anaesthesia was performed. Core and ambient temperatures, thermal comfort and shivering were measured every 15 min thereafter. The primary outcome was the temperature at 60 min.ResultsTemperature decreased in all groups. Although the temperature decrease at 60 min was similar in the heated cabinet and Hotline® groups, the room temperature group exhibited a greater decrease [difference 0.4°C (95% CI 0.2-0.6°C); P = 0.015]. More women felt cold in the room temperature group (8: 32%) than in the heated cabinet set (3: 12%) and Hotline® (1: 4%) groups (P = 0.02), but the incidence of shivering was similar: 11 (44%), 9 (36%) and 7 (28%) respectively. Apgar scores and neonatal cord gases were similar.ConclusionWarming intravenous fluids mitigates the decrease in maternal temperature during elective caesarean section under combined spinal-epidural anaesthesia and improves thermal comfort, but does not affect shivering. Intravenous fluids should be warmed routinely in elective caesarean section, especially for cases of expected long duration, but the use of pre-warmed fluids is as efficient and cheaper than using a Hotline^® fluid warmer.     

Stroke volume optimization after anaesthetic induction: An open randomized controlled trial comparing 0.9% NaCl versus 6% hydroxyethyl starch 130/0.4

Objective

Postinduction hypotension during general anaesthesia could be corrected by a rapid cardiac preload optimization by fluid infusion. The type of fluid to be used in this context remains debated. The aim of our study was to compare the amount of fluid challenges required to optimize stroke volume after induction of anaesthesia with colloid (HES) or crystalloid (0.9% NaCl).

Design

Open randomized prospective parallel-group study.

Patients and methods

Fifty-six adult patients scheduled to undergo orthopaedic surgery under general anaesthesia were randomly assigned to receive, either 0.9% NaCl (n = 28), or HES (n = 28). Cardiac preload optimization directed by oesophageal Doppler was performed after induction with fluid challenges of 250 ml of solution until stroke volume (SV) no longer increased by 10%. Primary endpoint was: number of fluid challenges required to achieve SV optimization. Secondary endpoints were: number of patients responding to the first fluid challenge, proportion of patients requiring ephedrine and the ephedrine dose required to restore arterial pressure.

Results

Percentages of responders were 61% and 63% in the 0.9% NaCl and HES groups, respectively. Number of fluid challenges necessary for SV optimization was not significantly different between 0.9% NaCl group and HES group (2 [1–2] versus 2 [1–2], P = 0.33). Number of patients needing ephedrine, and well as the associated ephedrine dose, did not differ significantly.

Conclusions

Our study suggests that after induction, crystalloid and colloid expand the intravascular volume with equivalent efficacy immediately after administration and correct in a similar way the postinduction hypotension.     

Ephedrine versus phenylephrine as a vasopressor for spinal anaesthesia-induced hypotension in parturients undergoing high-risk caesarean section: meta-analysis,meta-regression and trial sequential analysis

BackgroundPhenylephrine is the preferred vasopressor for the prevention and treatment of spinal anaesthesia-induced hypotension during caesarean section, because studies on low-risk elective patients found it to have a less detrimental effect on umbilical artery pH compared with ephedrine. However, limited data exist from high-risk parturients and parturients with uteroplacental insufficiency.MethodsWe systematically searched for randomised, controlled, double-blinded trials of these two vasopressors in high-risk caesarean sections. We applied conventional meta-analysis, trial sequential analysis, computing the required information size that would exclude type I and II errors, contour-enhanced funnel plot testing for publication bias, meta-regression to assess the dose–response relationship, and the Grading of Recommendations Assessment, Development, and Evaluation system (GRADE). The incidence of fetal acidosis (umbilical arterial pH <7.2) was the primary outcome.ResultsEight trials (712 patients) with low risk of bias were identified. Pooling six studies of patients with preeclampsia and other reasons for fetal compromise, as well as subgroup analysis of the preeclampsia studies, revealed no significant differences in the incidence of fetal acidosis. Trial sequential analysis showed that the required information size was not reached. The funnel plot was not suggestive of publication bias. Meta-regression showed no dose-response relationship. The GRADE score was moderate quality.ConclusionsDespite several studies and a large number of patients there was insufficient evidence to make a recommendation for choice of vasopressor in high-risk caesarean section. Trials with adequate power to detect differences in the incidence of fetal acidosis between ephedrine and phenylephrine are required to provide evidence-based guidance.