Combined spinal-extradural anaesthesia for preterm and term caesarean section: is there a difference in local anaesthetic requirements?

Failed spinal anesthesia for cesarean delivery: prevention, identification and management

PURPOSE OF REVIEW

There is an increasing awareness of the significance of intraoperative pain during cesarean delivery. Failure of spinal anesthesia for cesarean delivery can occur preoperatively or intraoperatively. Testing of the neuraxial block can identify preoperative failure. Recognition of the risk of high neuraxial block in repeat spinal in case of preoperative failure is important.

RECENT FINDING

Knowledge of risk factors for block failure facilitates prevention by selecting the most appropriate neuraxial procedure, adequate intrathecal doses and choice of technique. Intraoperative pain is not uncommon, and neither obstetricians nor anesthesiologists can adequately identify intraoperative pain. Early intraoperative pain should be treated differently from pain towards the end of surgery.

SUMMARY

Block testing is crucial to identify preoperative failure of spinal anesthesia. Repeat neuraxial is possible but care must be taken with dosing. In this situation, switching to a combined spinal epidural or an epidural technique can be useful. Intraoperative pain must be acknowledged and adequately treated, including offering general anesthesia. Preoperative informed consent should include block failure and its management.

Comparative dose-response study of intrathecal hyperbaric ropivacaine for cesarean delivery in preterm singleton versus twin pregnancies

INTRODUCTION

Previously, we demonstrated that patients with full-term singletons and preterm twins require similar dose of intrathecal hyperbaric ropivacaine. However, these findings may be attributable to enrolled patients with preterm twin pregnancies. In this study, we aimed to determine the intrathecal dose requirements of hyperbaric ropivacaine for twins and singletons at equal gestational ages.

METHODS

We enrolled 75 patients with preterm singletons and 75 patients with preterm twins scheduled for cesarean delivery under combined spinal-epidural anesthesia in this two-arm parallel, randomized, double-blind, dose-response study. Patients with singletons and twins were randomly assigned to receive one of five different doses of hyperbaric ropivacaine: 10, 12, 14, 16, or 18 mg. A probit regression model was used to determine the dose effective in 50% of patients (ED50) and dose effective in 90% of patients (ED90) values. The relative median potency was calculated to compare the ED50 between patients with twins and singletons.

RESULTS

Intrathecal ropivacaine ED50 and ED90 (with 95% CI) in patients with preterm singletons were 9.9 (7.2 to 11.5) mg and 16.8 (14.5 to 22.9) mg, respectively. In patients with preterm twins, these values were 9.2 (95% CI 6.4 to 10.8) mg and 15.6 (95% CI 13.6 to 20.6) mg. Between patients with preterm twins and preterm singletons, the relative potency (ED50 ratios) was 0.933 (95% CI 0.72 to 1.15).

CONCLUSIONS

During preterm gestation, intrathecal hyperbaric ropivacaine dose requirements for scheduled cesarean delivery were not different between patients with twins and singletons.

TRIAL REGISTRATION NUMBER

ChiCTR2100051382.

Comparison of Phenylephrine and Ephedrine in Treatment of Spinal-Induced Hypotension in High-Risk Pregnancies: A Narrative Review

Purpose

To compare maternal and fetal effects of intravenous phenylephrine and ephedrine administration during spinal anesthesia for cesarean delivery in high-risk pregnancies.

Source

An extensive literature search was conducted using the US National Library of Medicine, MEDLINE search engine, Cochrane review, and Google Scholar using search terms “ephedrine and phenylephrine,” “preterm and term and spinal hypotension,” “preeclampsia and healthy parturients,” or “multiple and singleton gestation and vasopressor.” Society of Obstetric Anesthesia and Perinatology meeting abstracts for the past 4 years were also searched for relevant studies.

Principle findings

Both phenylephrine and ephedrine can be safely used to counteract hypotension after spinal anesthesia in patients with uteroplacental insufficiency, pregnancy-induced hypertension, and in non-elective cesarean deliveries. Vasopressor requirements before delivery in high-risk cesarean sections are reduced compared to healthy parturients. Among the articles reviewed, there were no statistically significant differences in umbilical arterial pH, umbilical venous pH, incidence of fetal acidosis, Apgar scores, or maternal hypotension when comparing maternal phenylephrine and ephedrine use.

Conclusion

From the limited existing data, phenylephrine and ephedrine are both appropriate selections for treating or preventing hypotension induced by neuraxial blockade in high-risk pregnancies. There is no clear evidence that either medication is more effective at maintaining maternal blood pressure or has a superior safety profile in this setting. Further investigations are required to determine the efficacy, ideal dosing regimens, and overall safety of phenylephrine and ephedrine administration in high-risk obstetric patients, especially in the presence uteroplacental insufficiency.

Retrospective comparison of ephedrine and phenylephrine for the treatment of spinal anesthesia induced hypotension in pre-eclamptic patients

OBJECTIVE

To compare neonatal acid base status in parturients who underwent cesarean delivery and received either ephedrine or phenylephrine boluses for the treatment of spinal anesthesia induced hypotension.

RESEARCH DESIGN AND METHODS

After institutional review board approval, the perioperative database of the University of Iowa Hospitals and Clinics was used to identify all women diagnosed with pre-eclampsia and had cesarean delivery under spinal anesthesia for the period 1 January 2005 to 31 July 2014. Data retrieved included patient demographics, indication for cesarean delivery, severity of pre-eclampsia, dose of vasopressor, neonatal umbilical artery pH and Apgar scores.

MAIN OUTCOME MEASURES

Primary outcome was umbilical artery pH.

RESULTS

Data for 146 patients was included in the analysis. Ephedrine was used in 57 patients (group E) and phenylephrine in 89 (group PE) patients. The median umbilical artery pH was 7.30 (IQR 7.20-7.30) and 7.30 (IQR 7.20-7.30) in the ephedrine and phenylephrine groups respectively (P = 0.41). Non-reassuring fetal heart trace was the only factor significantly associated with lower umbilical artery pH on multivariable regression analysis (β = -0.09, P = 0.002).

CONCLUSIONS

We found no difference in neonatal umbilical artery pH between ephedrine and phenylephrine when used to treat spinal anesthesia induced hypotension during cesarean delivery in pre-eclamptic patients. Limitations of the study include its retrospective single center design and the fact that the choice of vasopressor was not randomized.

Head Elevation in Spinal-Epidural Anesthesia Provides Improved Hemodynamics and Appropriate Sensory Block Height at Caesarean Section

PURPOSE

We aimed to determine whether head elevation during combined spinal-epidural anesthesia (CSE) and Caesarean section provided improved hemodynamics and appropriate sensory block height.

MATERIALS AND METHODS

Forty-four parous women undergoing CSE for elective Caesarean section were randomly assigned to one of two groups: right lateral (group L) or right lateral and head elevated (group HE) position, for insertion of the block. Patients were positioned in the supine wedged position (group L) or the left lateral and head elevated position (group HE) until a block height of T5 to light touch was reached. Group HE was then turned to the supine wedged position with maintenance of head elevation until the end of surgery. Hemodynamics, including the incidence of hypotension, ephedrine dose required, and characteristics of the sensory blocks were analyzed.

RESULTS

The incidence of hypotension (16 versus 7, p=0.0035) and the required dose of ephedrine [24 (0-40) versus 0 (0-20), p<0.0001] were greater in group L compared to group HE. In group L, the time to achieve maximal sensory block level (MSBL) was shorter (11.8±5.4 min versus 20.1±6.3 min, p<0.0001) and MSBL was also higher than in group HE [14 (T2) versus 12 (T4), p=0.0015].

CONCLUSION

Head elevation during CSE and Caesarean section is superior to positioning without head elevation in the lateral to supine position, as it is associated with a more gradual onset, appropriate block height, and improved hemodynamics.

Retrospective study of association between choice of vasopressor given during spinal anaesthesia for high-risk caesarean delivery and fetal pH

BACKGROUND

Phenylephrine given during spinal anaesthesia for low-risk caesarean section is associated with higher fetal pH than ephedrine. However, there is little evidence on the effects of ephedrine and phenylephrine in complicated pregnancies. The aim of this study was to compare umbilical artery pH with phenylephrine and ephedrine given during spinal anaesthesia where caesarean section was performed because of an increased risk of fetal compromise.

METHODS

We reviewed the case notes of all women at our hospital from 2000-2003 who had undergone high-risk caesarean section under spinal anaesthesia, where umbilical artery and venous pH had been recorded at delivery. Umbilical artery pH was compared by choice of vasopressor and multiple regression analysis was used to investigate the effects of other possible confounding variables.

RESULTS

One hundred and fifteen patients received no vasopressor, 122 ephedrine (group E) and 148 phenylephrine (group P). The median umbilical artery pH was 7.26 (IQR 7.21-7.30) for the no-vasopressor group, 7.27 (7.22-7.30) for group E and 7.28 (7.22-7.32) for group P (P=0.21). Using multiple regression analysis, the only variable associated with altered umbilical artery pH was a non-reassuring fetal heart trace.

CONCLUSIONS

Umbilical artery pH was similar whether ephedrine or phenylephrine was used to maintain maternal arterial pressure, which contrasts with studies of low-risk caesarean section.

A prospective audit of regional anaesthesia failure in 5080 Caesarean sections

Anaesthesia for Caesarean section was audited over a 5 year period: 5080 cases were performed using spinal 63%, epidural top-up 26%, combined spinal-epidural 5% and primary general anaesthesia 5%. The rate of general anaesthesia conversion of regional anaesthesia was 0.8% for elective and 4.9% for emergency Caesarean section compared to Royal College of Anaesthetists targets of 1% and 3%. The rate of conversion of regional to general anaesthesia in category 1 Caesarean section was 20%. A total of 8% of women had general anaesthesia when both primary general and conversion of regional anaesthesia were combined. The rate of failure to achieve a pain-free operation was 6% with spinals, 24% with epidural top-up and 18% with combined spinal-epidural. Besides the type of anaesthesia and operative urgency, other factors associated with pre-operative failure of regional anaesthesia included body mass index, no previous Caesareans, and indication for Caesarean of acute fetal distress or maternal medical condition. Inadequacy of pre-operative anaesthetic block and duration of surgery were important risk factors for intra-operative failure. For spinal anaesthesia, use of a spinal opioid was associated with less pre-operative failure. For epidural top-up anaesthesia, lower epidural top-up volume was associated with less pre-operative failure, and use of adrenaline was associated with both less pre-operative and intra-operative failure. The rate of serious adverse incidents was 1 : 126 with general anaesthesia and 1 : 501 with regional anaesthesia.

Emergency Caesarean section: best practice*

Good multidisciplinary communication is crucial to the safe management of women requiring non-elective Caesarean section. Anaesthetists should participate actively in resuscitation of the fetus in utero; relief of aortocaval compression is paramount. Epidural top-up with levobupivacaine 0.5% is the anaesthetic of choice for women who have been receiving labour epidural analgesia. If epidural top-up fails to provide bilateral light touch anaesthesia from S5 - T5, a combined spinal-epidural technique with small intrathecal dose of local anaesthetic is a useful approach. Pre-eclampsia is not a contra-indication to single-shot spinal anaesthesia, which is the technique of choice for most women presenting for Caesarean section without an epidural catheter in situ. Induction and maintenance doses of drugs for general anaesthesia should not be reduced in the belief that the baby will be harmed. Early postoperative observations are geared towards the detection of overt or covert haemorrhage.

Caesarean section in a patient with cystic fibrosis

Severely impaired pulmonary function due to cystic fibrosis is associated with a poor pregnancy outcome. A 19-year-old primigravida with cystic fibrosis had a forced expiratory volume in one second 34% of predicted and a low body mass index of 17.1 kg/m(2) before pregnancy. During pregnancy she required several admissions to hospital for deteriorating pulmonary function due to infection. She also developed gestational diabetes and required overnight feeding via a gastrostomy tube throughout pregnancy to improve her nutritional status. With close medical attention, pulmonary function tests remained stable. A joint decision was made to deliver the baby by caesarean section at 33 weeks' gestation as this was considered optimal time for mother and baby and to avoid potential catastrophic pulmonary deterioration later in pregnancy. A combined spinal-epidural technique provided adequate anaesthesia. Pulmonary function tests were performed in theatre before and after the spinal injection, as well as two and five hours postoperatively. Despite a spinal anaesthetic block to T5 bilaterally, lung function tests remained stable. An epidural infusion provided good postoperative analgesia. The outcome was successful for mother and fetus.

The combined spinal–epidural technique

In recent years, the use of regional anaesthesia techniques for surgery, obstetrics and post operative pain management have increased in popularity. The combined spinal-epidural (CSE) technique has attained widespread popularity for patients undergoing major surgery below the umbilicus who may require prolonged and effective postoperative analgesia. The CSE technique is now well established in several institutions. This chapter includes the clinical experience, advantages and potential problems, and discusses future perspectives of the CSE technique.

The combined spinal-epidural technique

Epidural and spinal blocks are well-accepted regional techniques, but they have several disadvantages. The CSE technique can reduce or eliminate the risks of these disadvantages. CSE block combines the rapidity, density, and reliability of the subarachnoid block with the flexibility of continuous epidural block to extend duration of analgesia. The CSE technique is used routinely at many institutions, particularly for major orthopedic surgery and in obstetrics. It has been used in tens of thousands of patients without any reports of major problems. Although at first sight the CSE technique appears to be more complicated than epidural or spinal block alone, intrathecal drug administration and siting of the epidural catheter are both enhanced by the combined, single-space, needle-through-needle method. Concerns about the epidural catheter entering the theca via the small puncture hole are now considered to be unfounded, but as with all epidural catheter techniques, vigilant monitoring of the patient during and after any injection is paramount. CSE is an effective way to reduce the total drug dosage required for anesthesia or analgesia. The intrathecal injection achieves rapid onset with minimal doses of local anesthetics and opioids, and the block can be prolonged with low-dose epidural maintenance administration. In addition, the sequential CSE method can be used to extend the dermatomal block with minimal additional drugs or even saline. Reduction in total drug dosage has made truly selective blockade possible. Many studies have confirmed that low-dose CSE with local anesthetic and opioid, or low-dose epidural block alone, will provide effective analgesia with minimal motor and proprioceptive block. Such neurologic selective blockade has made it possible for most patients to walk and bear down normally in labor or postoperatively. There remains concern about the risk of infection being increased when the CSE technique is used in place of epidural block alone. Despite a recent flurry of reports of meningitis with CSE procedures, there is no evidence the CSE block is more hazardous than epidural or subarachnoid block alone. Arguably, the single-space, needle-through-needle CSE technique will continue to improve with new needle designs and other advances to improve further the success rate and reduce complications, such as neurotrauma, PDPH, and infection. Over the past decade it has become clear that the CSE technique is a significant advance in regional blockade.

Oxford positioning technique improves haemodynamic stability and predictability of block height of spinal anaesthesia for elective caesarean section

A novel positioning technique was tested to see whether the unpredictability of block height and haemodynamic instability during spinal anaesthesia for caesarean section could be reduced. In this 'Oxford' position, the woman is placed left lateral with an inflated bag under the shoulder and pillows supporting the head. Following spinal injection the woman is turned to an identical right lateral position. This is maintained until just before incision to minimise aorto-caval compression, when she is placed in the wedged supine position. Sixty women undergoing elective caesarean section were randomised to receive spinal anaesthesia using hyperbaric bupivacaine in either the Oxford (group O), or the sitting position followed immediately by the wedged supine position (group S). Ephedrine 6 mg was given every minute that systolic blood pressure was less than 80% of baseline. In group S, 9/30 women lost pinprick sensation up to T4 at 5 minutes compared with 2/30 in group O (chi2 test, P = 0.04). Block height was more variable in group S than in group O (f test, P = 0.001). Blood pressure decreased by a greater amount initially: group S women required more ephedrine (15.5 +/- 12.9 versus 9.2 +/- 7.7 mg, t test, P = 0.03). Block height with spinal anaesthesia for caesarean section is more predictable and haemodynamically stable if the Oxford position is used whilst anaesthesia develops.