Anaesth Intens Care (1990), 18, 400-412
Case Reports Inadvertent Spinal Anaesthesia with 0.125% Bupivacaine and Fentanyl During Labour M. J. PAECH*
Department of Anaesthesia, King Edward Memorial Hospital for Women, Perth, Western Australia Key Words: ANALGESIA, OBSTETRIC: epidural, fentanyl, bupivacaine; COMPLICATIONS: spinal anaesthesia
Inadvertent subarachnoid administration of epidural solution is a well-recognised, rare, but potentially life-threatening complication of obstetric analgesia. The recent introduction of combination low-dose bupivacaine and lipophilic opioid for epidural analgesia during labour creates the potential for both unintentional spinal anaesthesia and severe opioid-induced respiratory depression, should this complication occur. This case report describes the unrecognised subarachnoid injection of 0.125% bupivacaine with fentanyl 100 mcg, and a subsequent 'total spinal' after a second larger bolus dose of bupivacaine alone, in an obstetric patient having epidural analgesia in labour. CASE REPORT A 20-year-old, 84 kg primiparous woman was induced for post-maturity. Following two doses of intramuscular pethidine 100 mg, which did not provide adequate analgesia, she requested epidural analgesia. Cervical dilatation at this time was 3 cm. The anaesthetic registrar experienced considerable difficulty in siting an epidural catheter, making several attempts with the woman positioned both lateral and sitting. Eventually the epidural space was identified at a depth of 5 cm in the L2-3 interspace and a 16-gauge three side-holed catheter inserted 4 cm into the epidural space. After negative aspiration, a bolus dose of 12.5 mg of bupivacaine (0.125% plain bupivacaine 10 ml) combined with fentanyl 100 mcg, was administered. Rapid pain relief was obtained and *D.R.C.O.G., F.C. Anaes, F.F.A.R.A.C.S. Staff Anaesthetist. Address for Reprints: Dr. M. J. Paech, Department of Anaesthesia, King Edward Memorial Hospital for Women, 374 Bagot Road, Subiaco, WA 6008, Australia Accepted for publication March 28, 1990
the anaesthetist, without attempting to assess the block, left the delivery suite. Two-and-a-half hours later a top-up was requested. As the woman complained of severe itch, the anaesthetist was notified and instructed the midwife to administer the alternative solution he had charted, plain bupivacaine 0.25% 10 ml. This 25 mg bolus was given as 2 ml followed two minutes later by the further 8 m!. On completion of the injection, the woman complained of 'heavy' legs and hands, and rapidly became apnoeic, with apparent loss of consciousness. She was turned to the left lateral position, and ventilated by a midwife with 100% oxygen via a non-re breathing resuscitation bag. The hospital emergency paging system was incorrectly activated and the after-hours registrar took eight minutes to respond to a standard call to delivery suite. On his arrival, he found the woman to be well oxygenated and perfused, normotensive but apnoeic, with reactive dilated pupils. Intravenous naloxone 0.4 mg was administered with no significant effect and she was intubated without adjuvant drugs, ventilation being continued with 100% oxygen. Vaginal examination revealed 5 cm cervical dilatation, and although fetal cardiotocography was normal, the obstetric registrar in attendance decided to proceed to emergency caesarean section. Just prior to surgery, 30 minutes after intubation, spontaneous movement of the eyes and upper limbs recommenced. Therefore, general anaesthesia was induced with nitrous oxide: oxygen (50:50), enflurane 1% and vecuronium 4 mg. Ten minutes later a healthy male infant with Apgar scores of 9 and 9 was delivered. Surgery was completed thirty minutes later and she was extubated awake with good spontaneous respiration. Shortly after, 100 minutes after her 'collapse', sensory and motor block were assessed as having an upper level ofTl. Anae.thesia and Intensive Care, Vo/. 18, No. 3, August, 1990
CASE REPORT
At two-and-a-half hours, sensory anaesthesia had regressed to T 10 and her first request for postoperative analgesia was made after four hours. With her consent a radiological study was performed using 5 ml of water-soluble iodine-based radiographic contrast (iopamidol). Contrast injected via the epidural catheter was seen to spread into both the subarachnoid and epidural spaces. Further history was elicited from the woman later that day. She described the onset of analgesia after the initial epidural bolus as 'immediate', followed shortly thereafter by inability to move her legs or support herself upright in bed. Her main complaint, however, was severe pruritis involving her face and trunk. After the second bolus she described a rapidly ascending paralysis and the inability to breathe. She had some recall of her initial collapse, her subsequent intubation, and her transfer to the operating theatre. On the first postoperative day she discharged herself against medical advice, showing no evidence of postoperative complications or postdural puncture headache at that time. DISCUSSION
Inadvertent spinal anaesthesia following dural puncture at epidural space localisation or catheterisation occurs in about 1 in 3000 to 4000 obstetric epidurals. I ,2 In this case report, dural puncture, during a difficult epidural insertion, was unrecognised by the registrar anaesthetist, as was subarachnoid placement of the epidural catheter. Furthermore, signs suggestive of spinal anaesthesia were not detected by either the anaesthetist or attending midwife, so that when a subsequent (and larger) bupivacaine bolus dose was administered a life-threatening 'total spinal' ensued. The almost immediate onset of complete pain relief is a striking feature which should alert the anaesthetist to subarachnoid administration of local anaesthetic during obstetric analgesia. In contrast, after the normal epidural administration of a low-dose bupivacaine-fentanyl combination, clinically effective relief of labour pain is achieved in ten to fifteen minutes,3,4 as with stronger solutions of bupivacaine alone. The duration of effect of such combination solutions epidurally is approximately 90 to 120 minutes,3,4 as opposed to the 150 minutes before a top-up was required in this case. Severe pruritis is a common feature of subarachnoid opioids, including fentanyl. 5,6 In contrast, epidural fentanyl results in mild pruritis in about 30% of obstetric cases, but is rarely severe or of a facial distribution, usually being confined to the trunk and limbs. 7 Finally, motor block is usually minimal with low-dose combinations. In this case the woman had neither dyspnoea nor Anaesthesia and Intensive Care, Vol. 18. No. 3, August, 1990
401
upper limb weakness, but the profound truncal and lower limb weakness she experienced was not recognised as unusual. Failure to recognise subarachnoid catheter placement has been reported previously when a combination of low-dose bupivacaine and lipophilic opioid (0.125% bupivacaine-pethidine 25 mg 10 ml) was given for obstetric analgesia. 8 The degree of sensory-motor block which resulted from the initial epidural bolus is consistent with the administered dose of bupivacaine. Subarachnoid bupivacaine 0.125% 10 ml with adrenaline has recently been investigated as an agent for spinal caesarean section. 9 A sensory level of T9 was achieved within two minutes, mean maximum level being T2 (range C5-T5). Profound motor block of the lower extremities developed rapidly, but no patient experienced respiratory difficulty. Regression of sensory anaesthesia to Tll occurred in three hours. The effect of subarachnoid fentanyl has not been well evaluated. Preliminary human studies have shown the significant analgesic effect of 6.25 to 50 mcg doses, but have not investigated respiratory effects in detail. 5,6,10 A study of elderly males undergoing urological operations found that 50 mcg of subarachnoid fentanyl resulted in early respiratory depression in all cases. Two patients had periodic breathing and one a respiratory, followed by cardiac arrest, sixty minutes postadministration. I I Although the pharmacokinetics of subarachnoid fentanyl have not been investigated, this probably reflects rapid cephalad cerebrospinal fluid spread to the brainstem respiratory centre of an excessively large dose for this route. Accidental subarachnoid administration of another lipophilic opioid, pethidine, in a clinically appropriate epidural dose, has also produced severe respiratory depression and coma. 12 In this case report, respiratory depression, as assessed by respiratory rate monitoring at 15, 30 and 60 minutes post-injection, did not appear to occur. Respiratory rate may correlate poorly with both hypoventilation and hypoxaemia after spinal opioid administration,D but along with observation of conscious state, is the basis of minimum routine monitoring in most hospitals. Although so called 'isobaric' plain bupivacaine is not recommended as a spinal anaesthetic agent in the obstetric population (due to variability in both speed of onset and upper level of block), 12.5 mg (as 0.5% 2.5 ml) for caesarean section results in a mean sensory dermatomal level of T2.14 In this case, following 25mg ofbupivacaine (as 0.25% 10 ml), a characteristic total spinal ensued, with the rapid onset of apnoea and loss of consciousness, although without hypotension. Sixty minutes later at the
402
M. J. PAECH
completion of caesarean section, full recovery of consciousness and adequate spontaneous ventilation were present. Subsequent radiographic findings indicate it is possible only part of this dose entered the subarachnoid space, due to differential flow through the epidural catheter side-holes. The decision to perform caesarean section immediately in this case is worthy of consideration. On most occasions immediate delivery will be chosen on fetal grounds - that is, the presence of fetal distress at a time when urgent vaginal delivery is not possible. During 'total spinal', hypotension, severe and difficult to correct, may be present, severely compromising uteroplacental blood flow, fetal oxygenation and well-being. On this occasion the woman was positioned to avoid aortocaval compression, was adequately hydrated and remained normotensive throughout. There were no other maternal complications (for example acid aspiration) which may have warranted early delivery to expedite her management. A more conservative approach to obstetric management (continuous fetal monitoring, awaiting spontaneous maternal recovery for later vaginal delivery), may have been appropriate for this primigravid woman. This case highlights several other important considerations. First, dural puncture by needle or catheter may go unrecognised, even after aspiration. IS A test dose for subarachnoid catheter placement, although a contentious subject 16, can only be recommended, particularly if multiple attempts have been made to identify the epidural space. No test dose is completely reliable and patient safety relies on the presence of a vigilant anaesthetist. In this case, the anaesthetist left without carefully considering the clinical features of the epidural analgesia obtained or checking the woman for sensory changes in the relevant dermatomal distribution. Although changes in temperature perception may not be marked with low-dose epidural combinations, complete sensory anaesthesia would suggest a subarachnoid block. The principle that 'every dose is a test-dose' is also important. All epidural boluses should be administered in divided doses using small incremental aliquots. Had this method been applied to the second bolus ofbupivacaine alone, it is possible the potentially lethal consequences of a 'total spinal' may have been averted. Obstetric deaths due to inadequate management of this major complication continue to be reported overseas. IS The failure to recognise the subarachnoid injection of a low-dose bupivacaine-fentanyl combination on establishment of epidural analgesia in labour suggests perhaps even greater
vigilance is required when low-dose bupivacainefentanyl mixtures are used, and attention should be drawn to this in the review or development of educational programs, monitoring and management protocols for both practitioners and midwifery staff. It is imperative that well trained nursing and medical staff are readily available for prompt, appropriate resuscitation and management, as was provided in this case. In conclusion, this case report is the first to describe the inadvertent subarachnoid administration of low-dose bupivacaine-fentanyl combination during epidural analgesia in labour. Neither severe respiratory depression nor total spinal anaesthesia occurred; however, the incorrect catheter placement was not recognised and potentially life-threatening high spinal anaesthesia followed a larger subsequent bolus of bupivacaine alone.
REFERENCES
1. Crawford JS. Some maternal complications of epidural analgesia for labour. Anaesthesia 1985; 40: 1219-1225. 2. King Edward Memorial Hospital for Women WA; Obstetric Epidural Audit, 1973-1988 (in press). 3. Celleno D, Capogna G. Epidural fentanyl plus bupivacaine 0.125 per cent for labour; analgesic effects. Can J Anaesth 1988; 35:375-378. 4. Reynolds F, O'Sullivan G. Epidural fentanyl and perineal pain in labour. Anaesthesia 1989; 44:341-344. 5. Bohannon TW, Estes MD. Evaluation of subarachnoid fentanyl for postoperative analgesia (abstract). Anesthesiology 1987; 67:A237. 6. Leighton BL, De Simone CA, Norris MC, BenDavid B. Intrathecal narcotics for labour revisited: fentanyl 25 mcg and morphine 0.25 mg provide rapid, profound analgesia (abstract). Anesthesiology 1988; 69:A680. 7. Cohen SE, Tan S, Albright GA, Halpern J. Epidural fentanyl-bupivacaine mixtures for obstetric analgesia. Anesthesiology 1987; 67:403-407. 8. Brownridge P. Another misplaced epidural catheter. Anaesth Intensive Care 1984; 12:369-371. 9. Van Zundert AA, De Wolf AM, Vaes L, Soetens M. High volume spinal anaesthesia with bupivacaine 0.125% for cesarean section. Anesthesiology 1988; 69:998-1003. 10. Hunt CO, Datta S, Hauch M, Ostheimer GW, Hertwig L, Naulty JS. Perioperative analgesia with subarachnoid fentanyl-bupivacaine (abstract). Anesthesiology 1987; 67:A621. 11. Celleno D, Capogna G, Dardes N, Moscatelli B. Ventilatory effects of subarachnoid fentanyl (abstract). Reg Anesth 1988; 13;2S:29. 1·2. Brownridge P, Wrobel J, Watt-Smith J. Respiratory depression following accidental subarachnoid pethidine. Anaesth Intensive Care 1983; 11:237-240. Anaesthesia and Intensive Care. VD/. 18. No. 3. August. 1990
CASE REPORT 13. Etches RC, Sandler AN, Daley M. Respiratory depression and spinal opioids. Can J Anaesth 1989; 36: 165-185. 14. Russell IF, Holrnqvist ELO. Subarachnoid analgesia for caesarean section. Br J Anaesth 1987; 59:347-353.
403
15. Prince G, McGregor D. Obstetric epidural test doses. Anaesthesia 1986; 41: 1240-1250. 16. Dain SL, Rolbin SH, Hew EM. The epidural test dose in obstetrics: is it really necessary? Can J Anaesth 1987; 34:601-605.
Hyperbaric Oxygen for Cerebral Arterial Air Embolism Occurring During Caesarian Section F. M. DAVIS*, P. w. GLOVERt AND E. MAYCOCKt Hyperbaric Unit, The Princess Margaret Hospital and Department of Anaesthesia, Christchurch Women's Hospital, Christchurch, New Zealand Key Words: OBSTETRIC ANAESTHESIA: lower segment caesarean section, hyperbaric oxygen, clinical; COMPLICATIONS: air embolism, cerebral arterial gas embolus
Massive air embolism is a rare, sometimes lethal, complication of caesarean section. \-4 We describe a case of paradoxical cerebral arterial gas embolism treated with hyperbaric oxygen (HBO) with a subsequent good outcome. CASE HISTORY The patient, a 33-year-old woman, gravida 2, para 1, presented for elective lower segment caesarean section for grade 4 placenta praevia. There had been three slight episodes of bleeding in an otherwise normal pregnancy. Preoperatively, she gave a vague history of a childhood cardiac defect. Later information suggested this was rheumatic fever. She also complained of 'rheumatism' in her legs since childhood. No abnormality of the cardiovascular system was detected on examination. She was extremely anxious and refused epidural anaesthesia. Premedication was with ranitidine 150 mg orally night and morning and sodium citrate 30 ml prior to induction. An intravenous line was established and she was placed in the left lateral tilt position. Following preoxygenation, a rapid sequence induction was performed with thiopentone 300 mg and suxamethonium 100 mg, and endotracheal intubation achieved without incident. The patient was mechanically ventilated with nitrous 'M. D., F.F.A.R.C.S., F.F.A.R.A.C.S. tF.F.A.R.A.C.S ;F.F.A.R.A.C.S Address for Reprints: Dr. F. M. Davis, Department of Anaesthesia, Christcburcb Scbool of Medicine, P.O. Box 4345, Christcburcb, New Zealand. Accepted for publication April 23, 1990.
Anaesthesia and Intensive Care, Vol. 18, No. 3. August. 1990
oxide:oxygen 1: 1 ratio with 0.5% halothane via a circle system. Following delivery of the baby, fentanyl 100 micrograms and pethidine 100 mg were given intravenously. Muscle paralysis was maintained with atracurium. The electrocardiogram, blood pressure, oxygen saturation, end-tidal C02 and inspired O 2 were monitored throughout anaesthesia and a ventilator disconnect alarm was in place. At surgery, the uterine incision passed through the anteriorly situated placenta, necessitating its partial stripping from the uterine wall. A healthy baby girl was delivered six minutes after induction, with Apgar scores of six and nine at one and five minutes respectively. The anaesthetic course was uneventful apart from modest hypotension (90 mmHg systolic) for ten minutes immediately after delivery. No significant changes in other parameters were noted at the time. Blood loss of approximately 1500 ml was replaced intravenously with four litres Hartmann's solution. When surgery was finished, muscle paralysis was reversed and the patient extubated head-down on her side once satisfactory breathing and airway control had been re-established, although she was still asleep. Thirty minutes later, she remained unrousable. Blood pressure was 90 mmHg systolic and a wound haematoma and haematuria were noted. A coagulation screen was done and a two-unit blood transfusion commenced. Following naloxone 0.2 mg she appeared more awake but was restless and uttering incomprehensible sounds. A dense left hemiplegia was apparent. She was transferred to the intensive care unit of
Case Reports Inadvertent Spinal Anaesthesia with 0.125% Bupivacaine and Fentanyl During Labour M. J. PAECH*
Department of Anaesthesia, King Edward Memorial Hospital for Women, Perth, Western Australia Key Words: ANALGESIA, OBSTETRIC: epidural, fentanyl, bupivacaine; COMPLICATIONS: spinal anaesthesia
Inadvertent subarachnoid administration of epidural solution is a well-recognised, rare, but potentially life-threatening complication of obstetric analgesia. The recent introduction of combination low-dose bupivacaine and lipophilic opioid for epidural analgesia during labour creates the potential for both unintentional spinal anaesthesia and severe opioid-induced respiratory depression, should this complication occur. This case report describes the unrecognised subarachnoid injection of 0.125% bupivacaine with fentanyl 100 mcg, and a subsequent 'total spinal' after a second larger bolus dose of bupivacaine alone, in an obstetric patient having epidural analgesia in labour. CASE REPORT A 20-year-old, 84 kg primiparous woman was induced for post-maturity. Following two doses of intramuscular pethidine 100 mg, which did not provide adequate analgesia, she requested epidural analgesia. Cervical dilatation at this time was 3 cm. The anaesthetic registrar experienced considerable difficulty in siting an epidural catheter, making several attempts with the woman positioned both lateral and sitting. Eventually the epidural space was identified at a depth of 5 cm in the L2-3 interspace and a 16-gauge three side-holed catheter inserted 4 cm into the epidural space. After negative aspiration, a bolus dose of 12.5 mg of bupivacaine (0.125% plain bupivacaine 10 ml) combined with fentanyl 100 mcg, was administered. Rapid pain relief was obtained and *D.R.C.O.G., F.C. Anaes, F.F.A.R.A.C.S. Staff Anaesthetist. Address for Reprints: Dr. M. J. Paech, Department of Anaesthesia, King Edward Memorial Hospital for Women, 374 Bagot Road, Subiaco, WA 6008, Australia Accepted for publication March 28, 1990
the anaesthetist, without attempting to assess the block, left the delivery suite. Two-and-a-half hours later a top-up was requested. As the woman complained of severe itch, the anaesthetist was notified and instructed the midwife to administer the alternative solution he had charted, plain bupivacaine 0.25% 10 ml. This 25 mg bolus was given as 2 ml followed two minutes later by the further 8 m!. On completion of the injection, the woman complained of 'heavy' legs and hands, and rapidly became apnoeic, with apparent loss of consciousness. She was turned to the left lateral position, and ventilated by a midwife with 100% oxygen via a non-re breathing resuscitation bag. The hospital emergency paging system was incorrectly activated and the after-hours registrar took eight minutes to respond to a standard call to delivery suite. On his arrival, he found the woman to be well oxygenated and perfused, normotensive but apnoeic, with reactive dilated pupils. Intravenous naloxone 0.4 mg was administered with no significant effect and she was intubated without adjuvant drugs, ventilation being continued with 100% oxygen. Vaginal examination revealed 5 cm cervical dilatation, and although fetal cardiotocography was normal, the obstetric registrar in attendance decided to proceed to emergency caesarean section. Just prior to surgery, 30 minutes after intubation, spontaneous movement of the eyes and upper limbs recommenced. Therefore, general anaesthesia was induced with nitrous oxide: oxygen (50:50), enflurane 1% and vecuronium 4 mg. Ten minutes later a healthy male infant with Apgar scores of 9 and 9 was delivered. Surgery was completed thirty minutes later and she was extubated awake with good spontaneous respiration. Shortly after, 100 minutes after her 'collapse', sensory and motor block were assessed as having an upper level ofTl. Anae.thesia and Intensive Care, Vo/. 18, No. 3, August, 1990
CASE REPORT
At two-and-a-half hours, sensory anaesthesia had regressed to T 10 and her first request for postoperative analgesia was made after four hours. With her consent a radiological study was performed using 5 ml of water-soluble iodine-based radiographic contrast (iopamidol). Contrast injected via the epidural catheter was seen to spread into both the subarachnoid and epidural spaces. Further history was elicited from the woman later that day. She described the onset of analgesia after the initial epidural bolus as 'immediate', followed shortly thereafter by inability to move her legs or support herself upright in bed. Her main complaint, however, was severe pruritis involving her face and trunk. After the second bolus she described a rapidly ascending paralysis and the inability to breathe. She had some recall of her initial collapse, her subsequent intubation, and her transfer to the operating theatre. On the first postoperative day she discharged herself against medical advice, showing no evidence of postoperative complications or postdural puncture headache at that time. DISCUSSION
Inadvertent spinal anaesthesia following dural puncture at epidural space localisation or catheterisation occurs in about 1 in 3000 to 4000 obstetric epidurals. I ,2 In this case report, dural puncture, during a difficult epidural insertion, was unrecognised by the registrar anaesthetist, as was subarachnoid placement of the epidural catheter. Furthermore, signs suggestive of spinal anaesthesia were not detected by either the anaesthetist or attending midwife, so that when a subsequent (and larger) bupivacaine bolus dose was administered a life-threatening 'total spinal' ensued. The almost immediate onset of complete pain relief is a striking feature which should alert the anaesthetist to subarachnoid administration of local anaesthetic during obstetric analgesia. In contrast, after the normal epidural administration of a low-dose bupivacaine-fentanyl combination, clinically effective relief of labour pain is achieved in ten to fifteen minutes,3,4 as with stronger solutions of bupivacaine alone. The duration of effect of such combination solutions epidurally is approximately 90 to 120 minutes,3,4 as opposed to the 150 minutes before a top-up was required in this case. Severe pruritis is a common feature of subarachnoid opioids, including fentanyl. 5,6 In contrast, epidural fentanyl results in mild pruritis in about 30% of obstetric cases, but is rarely severe or of a facial distribution, usually being confined to the trunk and limbs. 7 Finally, motor block is usually minimal with low-dose combinations. In this case the woman had neither dyspnoea nor Anaesthesia and Intensive Care, Vol. 18. No. 3, August, 1990
401
upper limb weakness, but the profound truncal and lower limb weakness she experienced was not recognised as unusual. Failure to recognise subarachnoid catheter placement has been reported previously when a combination of low-dose bupivacaine and lipophilic opioid (0.125% bupivacaine-pethidine 25 mg 10 ml) was given for obstetric analgesia. 8 The degree of sensory-motor block which resulted from the initial epidural bolus is consistent with the administered dose of bupivacaine. Subarachnoid bupivacaine 0.125% 10 ml with adrenaline has recently been investigated as an agent for spinal caesarean section. 9 A sensory level of T9 was achieved within two minutes, mean maximum level being T2 (range C5-T5). Profound motor block of the lower extremities developed rapidly, but no patient experienced respiratory difficulty. Regression of sensory anaesthesia to Tll occurred in three hours. The effect of subarachnoid fentanyl has not been well evaluated. Preliminary human studies have shown the significant analgesic effect of 6.25 to 50 mcg doses, but have not investigated respiratory effects in detail. 5,6,10 A study of elderly males undergoing urological operations found that 50 mcg of subarachnoid fentanyl resulted in early respiratory depression in all cases. Two patients had periodic breathing and one a respiratory, followed by cardiac arrest, sixty minutes postadministration. I I Although the pharmacokinetics of subarachnoid fentanyl have not been investigated, this probably reflects rapid cephalad cerebrospinal fluid spread to the brainstem respiratory centre of an excessively large dose for this route. Accidental subarachnoid administration of another lipophilic opioid, pethidine, in a clinically appropriate epidural dose, has also produced severe respiratory depression and coma. 12 In this case report, respiratory depression, as assessed by respiratory rate monitoring at 15, 30 and 60 minutes post-injection, did not appear to occur. Respiratory rate may correlate poorly with both hypoventilation and hypoxaemia after spinal opioid administration,D but along with observation of conscious state, is the basis of minimum routine monitoring in most hospitals. Although so called 'isobaric' plain bupivacaine is not recommended as a spinal anaesthetic agent in the obstetric population (due to variability in both speed of onset and upper level of block), 12.5 mg (as 0.5% 2.5 ml) for caesarean section results in a mean sensory dermatomal level of T2.14 In this case, following 25mg ofbupivacaine (as 0.25% 10 ml), a characteristic total spinal ensued, with the rapid onset of apnoea and loss of consciousness, although without hypotension. Sixty minutes later at the
402
M. J. PAECH
completion of caesarean section, full recovery of consciousness and adequate spontaneous ventilation were present. Subsequent radiographic findings indicate it is possible only part of this dose entered the subarachnoid space, due to differential flow through the epidural catheter side-holes. The decision to perform caesarean section immediately in this case is worthy of consideration. On most occasions immediate delivery will be chosen on fetal grounds - that is, the presence of fetal distress at a time when urgent vaginal delivery is not possible. During 'total spinal', hypotension, severe and difficult to correct, may be present, severely compromising uteroplacental blood flow, fetal oxygenation and well-being. On this occasion the woman was positioned to avoid aortocaval compression, was adequately hydrated and remained normotensive throughout. There were no other maternal complications (for example acid aspiration) which may have warranted early delivery to expedite her management. A more conservative approach to obstetric management (continuous fetal monitoring, awaiting spontaneous maternal recovery for later vaginal delivery), may have been appropriate for this primigravid woman. This case highlights several other important considerations. First, dural puncture by needle or catheter may go unrecognised, even after aspiration. IS A test dose for subarachnoid catheter placement, although a contentious subject 16, can only be recommended, particularly if multiple attempts have been made to identify the epidural space. No test dose is completely reliable and patient safety relies on the presence of a vigilant anaesthetist. In this case, the anaesthetist left without carefully considering the clinical features of the epidural analgesia obtained or checking the woman for sensory changes in the relevant dermatomal distribution. Although changes in temperature perception may not be marked with low-dose epidural combinations, complete sensory anaesthesia would suggest a subarachnoid block. The principle that 'every dose is a test-dose' is also important. All epidural boluses should be administered in divided doses using small incremental aliquots. Had this method been applied to the second bolus ofbupivacaine alone, it is possible the potentially lethal consequences of a 'total spinal' may have been averted. Obstetric deaths due to inadequate management of this major complication continue to be reported overseas. IS The failure to recognise the subarachnoid injection of a low-dose bupivacaine-fentanyl combination on establishment of epidural analgesia in labour suggests perhaps even greater
vigilance is required when low-dose bupivacainefentanyl mixtures are used, and attention should be drawn to this in the review or development of educational programs, monitoring and management protocols for both practitioners and midwifery staff. It is imperative that well trained nursing and medical staff are readily available for prompt, appropriate resuscitation and management, as was provided in this case. In conclusion, this case report is the first to describe the inadvertent subarachnoid administration of low-dose bupivacaine-fentanyl combination during epidural analgesia in labour. Neither severe respiratory depression nor total spinal anaesthesia occurred; however, the incorrect catheter placement was not recognised and potentially life-threatening high spinal anaesthesia followed a larger subsequent bolus of bupivacaine alone.
REFERENCES
1. Crawford JS. Some maternal complications of epidural analgesia for labour. Anaesthesia 1985; 40: 1219-1225. 2. King Edward Memorial Hospital for Women WA; Obstetric Epidural Audit, 1973-1988 (in press). 3. Celleno D, Capogna G. Epidural fentanyl plus bupivacaine 0.125 per cent for labour; analgesic effects. Can J Anaesth 1988; 35:375-378. 4. Reynolds F, O'Sullivan G. Epidural fentanyl and perineal pain in labour. Anaesthesia 1989; 44:341-344. 5. Bohannon TW, Estes MD. Evaluation of subarachnoid fentanyl for postoperative analgesia (abstract). Anesthesiology 1987; 67:A237. 6. Leighton BL, De Simone CA, Norris MC, BenDavid B. Intrathecal narcotics for labour revisited: fentanyl 25 mcg and morphine 0.25 mg provide rapid, profound analgesia (abstract). Anesthesiology 1988; 69:A680. 7. Cohen SE, Tan S, Albright GA, Halpern J. Epidural fentanyl-bupivacaine mixtures for obstetric analgesia. Anesthesiology 1987; 67:403-407. 8. Brownridge P. Another misplaced epidural catheter. Anaesth Intensive Care 1984; 12:369-371. 9. Van Zundert AA, De Wolf AM, Vaes L, Soetens M. High volume spinal anaesthesia with bupivacaine 0.125% for cesarean section. Anesthesiology 1988; 69:998-1003. 10. Hunt CO, Datta S, Hauch M, Ostheimer GW, Hertwig L, Naulty JS. Perioperative analgesia with subarachnoid fentanyl-bupivacaine (abstract). Anesthesiology 1987; 67:A621. 11. Celleno D, Capogna G, Dardes N, Moscatelli B. Ventilatory effects of subarachnoid fentanyl (abstract). Reg Anesth 1988; 13;2S:29. 1·2. Brownridge P, Wrobel J, Watt-Smith J. Respiratory depression following accidental subarachnoid pethidine. Anaesth Intensive Care 1983; 11:237-240. Anaesthesia and Intensive Care. VD/. 18. No. 3. August. 1990
CASE REPORT 13. Etches RC, Sandler AN, Daley M. Respiratory depression and spinal opioids. Can J Anaesth 1989; 36: 165-185. 14. Russell IF, Holrnqvist ELO. Subarachnoid analgesia for caesarean section. Br J Anaesth 1987; 59:347-353.
403
15. Prince G, McGregor D. Obstetric epidural test doses. Anaesthesia 1986; 41: 1240-1250. 16. Dain SL, Rolbin SH, Hew EM. The epidural test dose in obstetrics: is it really necessary? Can J Anaesth 1987; 34:601-605.
Hyperbaric Oxygen for Cerebral Arterial Air Embolism Occurring During Caesarian Section F. M. DAVIS*, P. w. GLOVERt AND E. MAYCOCKt Hyperbaric Unit, The Princess Margaret Hospital and Department of Anaesthesia, Christchurch Women's Hospital, Christchurch, New Zealand Key Words: OBSTETRIC ANAESTHESIA: lower segment caesarean section, hyperbaric oxygen, clinical; COMPLICATIONS: air embolism, cerebral arterial gas embolus
Massive air embolism is a rare, sometimes lethal, complication of caesarean section. \-4 We describe a case of paradoxical cerebral arterial gas embolism treated with hyperbaric oxygen (HBO) with a subsequent good outcome. CASE HISTORY The patient, a 33-year-old woman, gravida 2, para 1, presented for elective lower segment caesarean section for grade 4 placenta praevia. There had been three slight episodes of bleeding in an otherwise normal pregnancy. Preoperatively, she gave a vague history of a childhood cardiac defect. Later information suggested this was rheumatic fever. She also complained of 'rheumatism' in her legs since childhood. No abnormality of the cardiovascular system was detected on examination. She was extremely anxious and refused epidural anaesthesia. Premedication was with ranitidine 150 mg orally night and morning and sodium citrate 30 ml prior to induction. An intravenous line was established and she was placed in the left lateral tilt position. Following preoxygenation, a rapid sequence induction was performed with thiopentone 300 mg and suxamethonium 100 mg, and endotracheal intubation achieved without incident. The patient was mechanically ventilated with nitrous 'M. D., F.F.A.R.C.S., F.F.A.R.A.C.S. tF.F.A.R.A.C.S ;F.F.A.R.A.C.S Address for Reprints: Dr. F. M. Davis, Department of Anaesthesia, Christcburcb Scbool of Medicine, P.O. Box 4345, Christcburcb, New Zealand. Accepted for publication April 23, 1990.
Anaesthesia and Intensive Care, Vol. 18, No. 3. August. 1990
oxide:oxygen 1: 1 ratio with 0.5% halothane via a circle system. Following delivery of the baby, fentanyl 100 micrograms and pethidine 100 mg were given intravenously. Muscle paralysis was maintained with atracurium. The electrocardiogram, blood pressure, oxygen saturation, end-tidal C02 and inspired O 2 were monitored throughout anaesthesia and a ventilator disconnect alarm was in place. At surgery, the uterine incision passed through the anteriorly situated placenta, necessitating its partial stripping from the uterine wall. A healthy baby girl was delivered six minutes after induction, with Apgar scores of six and nine at one and five minutes respectively. The anaesthetic course was uneventful apart from modest hypotension (90 mmHg systolic) for ten minutes immediately after delivery. No significant changes in other parameters were noted at the time. Blood loss of approximately 1500 ml was replaced intravenously with four litres Hartmann's solution. When surgery was finished, muscle paralysis was reversed and the patient extubated head-down on her side once satisfactory breathing and airway control had been re-established, although she was still asleep. Thirty minutes later, she remained unrousable. Blood pressure was 90 mmHg systolic and a wound haematoma and haematuria were noted. A coagulation screen was done and a two-unit blood transfusion commenced. Following naloxone 0.2 mg she appeared more awake but was restless and uttering incomprehensible sounds. A dense left hemiplegia was apparent. She was transferred to the intensive care unit of
