Efficacy of dexmedetomidine in suppressing cardiovascular and hormonal responses to general anaesthesia for caesarean delivery: a dose-response study

BackgroundPreoperative dexmedetomidine administration blunts haemodynamic and hormonal responses to tracheal intubation and reduces anaesthetic requirements. We hypothesized that dexmedetomidine would reduce the maternal haemodynamic and hormonal responses to elective caesarean delivery without harmful neonatal effects.MethodsAfter ethical approval, 68 parturients scheduled for elective caesarean delivery under general anaesthesia were randomly allocated to receive either placebo, or 0.2, 0.4 or 0.6 μg/kg/h intravenous dexmedetomidine (n = 17 per group) 20 min before induction. Anaesthesia was induced using a rapid-sequence technique with propofol and suxamethonium, and was maintained with 0.5–0.75 minimum alveolar concentration sevoflurane. Changes in maternal heart rate, mean blood pressure, minimum alveolar concentration sevoflurane, uterine tone, serum cortisol level, and Apgar scores, Neurologic Adaptive Capacity Scores and acid–base status were recorded.ResultsAfter induction, patients receiving dexmedetomidine had smaller increases in heart rate (P < 0.001) than those in the placebo group. Patients who received 0.4 and 0.6 μg/kg/h infusions of dexmedetomidine showed slower heart rates (?21.5% and ?36%, respectively; P < 0.001), lower mean blood pressures (?17% and ?25%, respectively; P < 0.001), sevoflurane minimum alveolar concentrations (?40% and ?44.5%, respectively; P < 0.001) and serum cortisol levels (?27% and ?34.6%, respectively; P < 0.001) and higher sedation scores for the first 15 min after extubation and greater uterine tone (P < 0.002). Apgar scores, NACS and acid–base status were similar in the four groups.ConclusionPreoperative administration of dexmedetomidine 0.4 and 0.6 μg/kg/h is effective in attenuating the maternal haemodynamic and hormonal responses to caesarean delivery under sevoflurane anaesthesia without adverse neonatal effects.     

The role of total intravenous anaesthesia for caesarean delivery

Obstetric general anaesthesia technique usually involves intravenous induction and maintenance with volatile agents. Total intravenous anaesthesia has gained in popularity in non-obstetric practice because of environmental concerns associated with volatile inhalational anaesthetics and evidence of a superior recovery profile. Publications on the use of total intravenous anaesthesia for caesarean delivery are sparse. The limited evidence suggests that total intravenous anaesthesia may confer benefits for caesarean delivery, including reducing the risk of haemorrhage. However, there are practical barriers to utilising total intravenous anaesthesia in obstetric anaesthesia. We discuss the evidence and potential role of total intravenous anaesthesia for caesarean delivery.     

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.     

Inspired oxygen concentration during general anaesthesia for caesarean section

The effects on maternal oxygen saturation, foetal wellbeing and umbilical blood gases were compared when parturients received either 30 or 50% oxygen prior to delivery by Caesarean section under general anaesthesia. Maternal arterial oxygen saturation was significantly increased in the group receiving 50% oxygen. There was no difference between the two groups in terms of Apgar score minus colour, time to sustained respiration or umbilical cord blood gas estimations. The use of 30% inspired oxygen during uncomplicated Caesarean section is advocated.     

Maternal and fetal outcome of anaesthesia for caesarean delivery in preeclampsia/eclampsia in Enugu, Nigeria: a retrospective observational study

BACKGROUND: Maternal mortality, for which preeclampsia is a major cause, is a problem in Nigeria. Accurate data are available for caesarean sections in the University of Nigeria Teaching Hospital, Enugu. We therefore studied the outcome of caesarean section among these high-risk patients. METHOD: We conducted a retrospective survey of hospital records of patients with preeclampsia/eclampsia who had caesarean delivery in this unit over a four-year span from July 1998 to June 2002. RESULTS: There were 3926 deliveries and 4036 births (3611 live births), with 898 women (23%) delivered by caesarean section. Of these, 125 (14%) had preeclampsia/eclampsia, 103 (82.4%) presenting for emergency caesarean delivery and 22 (17.6%) elective. General anaesthesia was used in 116 patients (92.8%) and spinal in nine. The major indications for surgery were severe preeclampsia/eclampsia in patients with unfavourable cervix (68%), fetal distress/intrauterine growth restriction (7.2%) and previous caesarean section (6.4%). There were six maternal deaths, all with general anaesthesia, giving a case fatality rate of 5.2% of general anaesthetics or 4.8% of caesarean deliveries. The cause of death was anaesthetic in three patients, cerebrovascular accident and pulmonary oedema in two and intraoperative haemorrhage in one. There were 13 stillbirths and 10 neonatal deaths. CONCLUSION: Maternal and fetal mortality were high. Poverty, late presentation, lack of equipment and inexperienced management were major contributory factors. Use of spinal anaesthesia should be encouraged in view of recent favourable reviews and cheaper cost.     

The use of remifentanil during general anaesthesia for caesarean delivery in two patients with severe heart dysfunction

We describe the management of two patients with severe heart dysfunction requiring caesarean section because of incipient left ventricular failure. One patient had a bicuspid valve and developed symptoms of severe aortic incompetence during pregnancy. The second patient had known hypertrophic obstructive cardiomyopathy and developed chest pain and symptoms of left ventricular failure at 32 weeks' gestation. In both cases the worsening cardiac disease prompted the decision for operative delivery. We decided to employ general anaesthesia and achieved cardiovascular stability using remifentanil as an adjunct.     

Pregnancy complicated by aortic dissection: caesarean delivery during extradural anaesthesia

We report a case where dissection of the aorta occurred in pregnancy; only medical management was undertaken. Delivery was by Caesarean section during extradural anaesthesia and was accomplished safely several weeks after the dissection. The aetiology, association with pregnancy, diagnosis and management of acute dissection of the aorta are discussed.      

Acute magnesium toxicity in an obstetric patient undergoing general anaesthesia for caesarean delivery

Magnesium is commonly used in the prevention of eclampsia. Reports of acute toxicity are rare and we are not aware of detailed management algorithms. We present a case of acute magnesium toxicity presenting as ventilatory impairment and failure to rouse adequately from general anaesthesia. The patient was managed with controlled ventilation, further sedation, intravenous calcium gluconate, forced diuresis and dextrose-insulin infusion. We present a guideline for the management of life-threatening magnesium toxicity and discuss measures that may prevent future similar occurrences.     

Maternal and neonatal effects of bolus administration of ephedrine and phenylephrine during spinal anaesthesia for caesarean delivery: a randomised study

BackgroundMaternal haemodynamic changes and neonatal well-being following bolus administration of ephedrine and phenylephrine were compared in 60 term parturients undergoing elective caesarean delivery under spinal anaesthesia.MethodsIn a randomised double-blind study, women received boluses of either ephedrine 6 mg (group E; n=30) or phenylephrine 100 μg (group P; n=30) whenever maternal systolic pressure was ?80% of baseline.ResultsChanges in systolic pressure were comparable in the two groups. There were no differences in the incidence of bradycardia (group E: 0% vs. group P: 16.7%; P>0.05), nausea (group E: 13% vs. group: P 0; P>0.05) and vomiting (group E: 3.3% vs. group P: 0; P>0.05). Umbilical artery (UA) pH (group E: 7.29 ± 0.04 vs. group P: 7.32 ± 0.04; P=0.01) and venous pH (group E: 7.34 ± 0.04 vs. group P: 7.38 ± 0.05; P=0.002) were significantly greater in group P than in group E. UA base excess was significantly less in group E (-2.83 ± 0.94 mEq/L) than in group P (-1.61 ± 1.04 mEq/L; P<0.001). Apgar scores at 1, 5 and 10min and neurobehavioural scores at 2-4 h, 24 h and 48 h were similar in the two groups (P>0.05).ConclusionsPhenylephrine 100 μg and ephedrine 6 mg had similar efficacy in the treatment of maternal hypotension during spinal anaesthesia for elective caesarean delivery. Neonates in group P had significantly higher umbilical arterial pH and base excess values than those in group E, which is consistent with other studies.     

Regional anaesthesia for labour,operative vaginal delivery and caesarean delivery: a narrative review

This narrative review discusses recent evidence surrounding the use of regional anaesthesia in the obstetric setting, including intrapartum techniques for labour and operative vaginal delivery, and caesarean delivery. Pudendal nerve blockade, ideally administered by an obstetrician, should be considered for operative vaginal delivery if neuraxial analgesia is contraindicated. Regional techniques are increasingly utilised in clinical practice for caesarean delivery to minimise opioid consumption, reduce pain, improve postpartum recovery and facilitate earlier discharge as part of enhanced recovery protocols. The evidence surrounding transversus abdominis plane and quadratus lumborum blockade supports their use when: long-acting neuraxial opioids cannot be administered due to contraindications; if emergency delivery necessitates general anaesthesia; or as a postoperative rescue technique. Current data suggest quadratus lumborum blockade is no more effective than transversus abdominis plane blockade after caesarean delivery. Transversus abdominis plane blockade, wound catheter insertion and single shot wound infiltration are all effective techniques for reducing postoperative opioid consumption, with transversus abdominis plane blockade favoured, followed by wound catheters and then wound infiltration. Ilio-inguinal and iliohypogastric, erector spinae plane and rectus sheath blockade all require further studies to determine their efficacy for caesarean delivery in the presence or absence of long-acting neuraxial opioids. Future studies are needed to: compare approaches for individual techniques; determine which combinations of techniques and dosing regimens result in optimal analgesic and recovery outcomes following delivery; and elucidate the populations that benefit most from regional anaesthesia in the obstetric setting.     

Absence of memory for intraoperative information during surgery under adequate general anaesthesia

Using the isolated forearm technique (IFT), we wished to determine if patients known to be unresponsive to commands during general anaesthesia with nitrous oxide, halothane and neuromuscular blocking agents had any evidence of explicit or implicit recall. Two groups of women, studied in a single-blind sequential block design, heard different tapes, either a command and information tape (n = 34) or radio static (n = 34), throughout surgery. Four women (two radio static, two command) had unequivocal evidence of explicit recall for a period near the beginning or end of the procedure, at a time when the IFT was not being used. With or without hypnosis, category generation, serial position of category exemplars and word association tests did not reveal evidence of priming. We conclude that during light general anaesthesia with nitrous oxide, halothane and atracurium, patients had neither explicit nor implicit memory for information presented during a period when they are known to be unresponsive to commands.      

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.     

Epidural anaesthesia for caesarean delivery in triple and quadruple pregnancies

Background: Mechanical and/or hormonal factors may increase the spread of epidural anaesthesia in pregnancy, and hormonal changes are more pronounced in high-order pregnancies. However, no previous study has evaluated the dose requirements and haemodynamic effects of epidural anaesthesia for caesarean delivery in this latter situation.
Methods: The anaesthetic requirements to obtain a T4 upper sensory level were restrospectively compared in triple (n=19) or quadruple (n=2) pregnancies to 31 singleton pregnancies who received epidural anaesthesia for elective caesarean delivery using 2% lidocaine with 1/200 000 adrenaline.
Results: In high-order pregnancies, the gestational age at delivery was lower than in singleton pregnancies (34.9±1.9 weeks vs 38.2±1.1 weeks; P =0.0001) whereas maternal body weight (76.5±8.7 kg vs 73.4±14.8 kg; NS) and lidocaine requirements (428±95 mg vs 426±98 mg; NS) were similar. Moreover, although the overall incidence of hypotension was not different (multiple pregnancy; 65% vs 58% in singletons), ephedrine (5.4±5.3 mg vs 10.7±13.8 mg; P <0.05) and additional fluid requirements during onset of the block (4.3±1.7 mL/kg vs 5.3±2.6 mL/kg; P =0.03) were less than in singletons.
Conclusion: We found surprisingly similar anaesthetic requirements for epidural anaesthesia in high-order and singleton pregnancies. Mechanical factors may have played an important role. Moreover, the need for ephedrine and fluids was less in high-order pregnancies. This could be related to more pronounced physiological changes or to different physician attitudes.     

Distractions during critical phases of anaesthesia for caesarean section: an observational study

Aviation's ‘sterile cockpit’ rule holds that distractions on the flight deck should be kept at a minimum during critical phases of flight. To assess current practice at comparable points during obstetric regional anaesthesia, we measured ambient noise and distracting events during 30 caesarean sections in three phases: during establishment of regional anaesthesia; during testing of regional blockade; and after delivery of the fetal head. Mean (SD) noise levels were 62.5 (3.9) dB during establishment of blockade, 63.9 (4.1) dB during testing and 66.8 (5.0) dB after delivery (p < 0.001). The median rates of sudden, loud (> 70 dB) noises, non‐clinical conversations and numbers of staff present in the operating theatre increased during each of the three phases. Conversely, entrances into, and exits from, theatre per minute were highest during establishment of regional anaesthesia and decreased over the subsequent two time periods (p < 0.001).