Combined spinal epidural anaesthesia is better than spinal or epidural alone for Caesarean delivery

Abstract

Editor—General anaesthesia for Caesarean delivery is associated with substantially greater maternal risk than regional anaesthesia.1Hawkins JL Koonin LM Palmer SK et al.Anesthesia-related deaths during obstetric delivery in the United States.Anesthesiology. 1997; 86: 277-284Crossref PubMed Scopus (605) Google Scholar Most of the deaths occurring during general anaesthesia are airway or aspiration related. Spinal and epidural anaesthesia have therefore become more widely utilized in surgical obstetric practice. Spinal anaesthesia is simple to institute, rapid in its effect and produces excellent operating conditions. Continuous epidural analgesia is more titratable, may produce less haemodynamic swings, and can be topped up if surgery is prolonged or postoperative pain relief is required. Both techniques have a failure rate of 2–5% even with experienced practitioners. The introduction of combined spinal–epidural anaesthesia (CSEA) offers benefits of both spinal and epidural anaesthesia. CSEA also offers the prospect of reducing the anaesthetic failure rate to only a fraction of either technique used alone. In theory, if the failure rate of either spinal or epidural anaesthesia used alone was 4%, then the chance of both techniques failing at the same time, if combined, would be 0.16%. Our institution is a large training hospital with many anaesthetics being performed by anaesthesia residents under supervision of a consultant anaesthetist. Recently, we started administering CSEA as a routine for Caesarean section in patients without an existing labour epidural in place, and who had no contraindications to regional anaesthesia. It was our impression, based on our quality assurance activities, that our regional anaesthesia failure rate (as defined by the necessity to administer general anaesthesia after the block) had decreased dramatically. To verify this increased success rate, we have retrospectively reviewed 6 months of our experience (525 cases) in regard to success rate, safety, and any procedural difficulties related to CSEA for Caesarean delivery. After approval of our Institutional Review Board, we reviewed all the Caesarean sections that were performed from July 15, 1999 to January 15, 2000 under the CSEA. The patients were usually placed in the sitting position. Under sterile conditions, the epidural space was entered using a loss-of-resistance technique and a 17 G Tuohy needle. A needle-through-needle technique was then used wherein a 27 G Whitacre point, 12.7 cm spinal needle was introduced into the subarachnoid space. Based upon weight and height, 7.5–10.5 mg of bupivacaine 0.75% in dextrose 8.5% was used for the spinal injection. The lower dose range was frequently used for patients with pregnancy-induced hypertension in whom wide swings of blood pressure were anticipated. Fentanyl 10–15 μg was added to the spinal anaesthetic. Immediately after the spinal injection, a 20 G epidural catheter was threaded into the epidural space and secured in position. Ephedrine 10–15 mg was administered i.v. as prophylaxis against hypotension at the time of the spinal injection in most patients. If the level of anaesthesia from the spinal anaesthetic was judged to be inadequate for the operation, the epidural catheter was used to inject incremental doses of lidocaine 2% with 1:200 000 epinephrine. The total dose of epidural lidocaine was titrated to achieve appropriate surgical anaesthesia. After delivery of the baby, preservative-free morphine 3–4 mg was usually injected via the epidural catheter, and the catheter was removed before leaving the operating room. For the purposes of the study, the success of CSEA was defined as an absence of the need to administer general anaesthesia prior to or during the Caesarean section (see Table 1).Table 1Success rate of combined spinal–epidural anaesthesia (CSEA)No.%Patients receiving CSEA525Spinal anaesthesia alone adequate for surgery38873.9Epidural supplementation required for inadequate spinal10620.2Failure to obtain CSF through spinal needle (epidural catheter alone used for surgery)132.4Paraesthesia during placement of spinal needle requiring abandonment of spinal injection10.2Inability to thread the epidural catheter after injection of spinal142.7General anaesthesia required due to inadequate regional anaesthesia (spinal failed, epidural failed therefore failed CSEA)30.6Overall success rate of CSEA52299.4 Open table in a new tab The duration of surgery varied from 29 to 197 min and included two Caesarean-hysterectomies. There were two inadvertent dural punctures with the Tuohy needle and both required a blood patch to treat post dural puncture headache. There were no cases of severe hypotension or of high block requiring ventilation or tracheal intubation. The anaesthetic success rate of 99.4% confirmed our view that CSEA is superior to either single-shot spinal or continuous epidural anaesthesia alone for Caesarean section. Although the need to supplement the spinal anaesthetic via the epidural was higher (20.2%) than the commonly accepted failure rates for spinal anaesthesia, there is a possible explanation. Knowing that the epidural catheter will be there as a ‘back-up’ if necessary, allows the anaesthetist to choose a dose for the spinal that is at the ‘low end’ of the range of possible doses. This may contribute to the safety of the technique, possibly reducing the risk of complications secondary to a high block from too large a spinal dose for that patient. Similarly, the presence of the epidural catheter as back-up to supplement a spinal that is too low, gives the anaesthetist the opportunity to perform a ‘modified CSEA’ wherein they purposefully select a partial spinal anaesthetic dose when the patient has severe pregnancy-induced hypertension or other disorders that make the prospect of dramatic haemodynamic changes particularly concerning.2Rawal N Single segment combined subarachnoid and epidural block for Caesarean section.Can Anaesth Soc J. 1986; 33: 254-255Crossref PubMed Scopus (37) Google Scholar 3Rawal N Schollin J Wesstrom G Epidural versus combined spinal epidural block for Caesarean section.Acta Anaesthesiol Scand. 1988; 32: 61-66Crossref PubMed Scopus (164) Google Scholar In 13 cases, there was a failure of the spinal needle to obtain CSF. There are several possible explanations for such failure. The Tuohy needle may be inadvertently off the midline when it reaches the epidural space, therefore guiding the spinal needle lateral to the thecal sac. Tenting of the dura, without perforating it by the rather blunt pencil-point type spinal needle, has also been described.4Rawal N Van Zundert A Holmstrom B et al.Combined spinal–epidural technique.Reg Anesth. 1997; 22: 406-423Crossref PubMed Google Scholar In 14 cases, there was inability to thread the epidural catheter after injection of the spinal medication. This problem has been described, but the mechanism remains uncertain.5Carrie LES Epidural versus combined spinal epidural block for Caesarean section.Acta Anaesthesiol Scand. 1988; 32: 595-596Crossref PubMed Scopus (45) Google Scholar The low incidence (0.5%) of ‘wet taps’ we experienced during CSEA has been described previously. During CSEA, the opportunity to replace the spinal needle to rule out proximity to the dura is beneficial when the anaesthetist is uncertain of the exact position of the tip of the Tuohy needle relative to the epidural space.6Coates MB Combined subarachnoid and epidural techniques.Anaesthesia. 1982; 37: 89-90Crossref PubMed Scopus (89) Google Scholar In summary, we found CSEA to be a considerable improvement to single-shot spinal or continuous epidural anaesthesia in the provision of reliable and safe regional anaesthesia for the parturient undergoing Caesarean section.