Management of failed intubation in a septic parturient

British Journal of Anaesthesia 89 (2): 328±30 (2002)

CASE REPORTS Management of failed intubation in a septic parturient D. Hinchliffe* and A. Norris Department of Anaesthesia, University Hospital, Nottingham NG7 2UH, UK *Corresponding author We describe a case in which regional anaesthesia for Caesarean section was initially avoided because of the presence of systemic infection. However, attempted induction of general anaesthesia resulted in failed tracheal intubation and so an epidural catheter was sited and used for the operation. Awake ®breoptic tracheal intubation was performed after surgery, when it was clear that ventilatory support on the intensive care unit would be needed. The relative risks of regional versus general anaesthesia when infection and dif®cult laryngoscopy coincide are discussed. Br J Anaesth 2002; 89: 328±30 Keywords: anaesthesia, obstetric; anaesthetic techniques, epidural; complications, infections; complications, intubation tracheal Accepted for publication: April 9, 2002

Systemic infection is a relative contraindication to regional anaesthesia because of the risk of introducing infected blood into the subarachnoid or epidural space. However, the absolute risk of epidural abscess or meningitis appears to be low in the obstetric population, and in patients predicted to be dif®cult to intubate, epidural or spinal anaesthesia may represent a safer choice than rapid sequence induction. Awake intubation may be the safest option of all, but is likely to be dif®cult during labour.

Case report Our patient, a 25-year-old nurse at 33 weeks' gestation in her ®rst pregnancy, presented to the delivery suite at 17:45 with a 3-day history of malaise and a 24 h history of spontaneous rupture of membranes. In the preceding 12 h she had developed rigors and was complaining of severe abdominal pain. One week previously, at her ®rst antenatal visit, her weight was 105 kg. On admission her temperature was 40°C, heart rate was 160 beats min±1, arterial pressure was 117/70 mm Hg and respiratory rate was 24 bpm. There were strong, regular and frequent uterine contractions. On vaginal examination, the cervix was 1 cm dilated and clear foulsmelling liquor was draining. The cardiotocograph showed a fetal tachycardia of 200 beats min±1. A full blood count, including platelets, and plasma electrolyte concentrations were normal. The partial thromboplastin time was 24.3 s

(control 30.5 s) and prothrombin time 7.9 s (control 10.0 s). In view of the prolonged interval after rupture of the membranes, the severe abdominal pain and offensive vaginal discharge, a diagnosis of chorioamnionitis was made and antibiotic therapy was commenced with i.v. cefuroxime and metronidazole. The anaesthetist (senior house of®cer) was asked to assess the patient prior to urgent Caesarean section. In addition to the above ®ndings, only the soft palate was visible on performing the Mallampati test.1 More senior anaesthetic assistance (specialist registrars, years 2 and 5) was requested and the decision was made to proceed with general anaesthesia in view of the presence of systemic infection. Oral 0.3 M sodium citrate 30 ml was administered, and standard monitoring (pulse oximetry, electrocardiography and non-invasive arterial pressure) was started. Immediately before induction of anaesthesia, the heart rate was 140 beats min±1, arterial pressure was 110/ 60 mm Hg and SpO2 was 96% breathing air. At 18:15, following 3 min of preoxygenation at 10 litres min±1 via a tight-®tting face mask and a Mapleson D circuit, a rapid sequence induction of general anaesthesia was performed using etomidate 20 mg and succinylcholine 100 mg. Cricoid pressure was applied as soon as loss of consciousness occurred. On laryngoscopy, only the tip of the epiglottis was visualized, the supraglottic structures appeared oedematous, and the SpO2 decreased to 80% within 90 s. Without any

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Failed intubation in a septic parturient

attempt at tracheal intubation, the decision was made to wake up the patient in the supine position with a left lateral tilt, maintaining cricoid pressure throughout. It was possible to establish a patent airway using an oropharyngeal airway and a jaw-thrust manoeuvre. A second anaesthetist provided hand ventilation via the rebreathing bag. Spontaneous respiration occurred within 4 min of induction of anaesthesia and the patient was transferred to the left lateral position while cricoid pressure was maintained. There was no regurgitation of gastric contents. On return of consciousness, the patient was confused and tachypnoeic (32 bpm).The SpO2 was 92% while breathing 100% oxygen. The patient remained tachycardic at 150 beats min±1 and the arterial pressure was 100/50 mm Hg. A consultant obstetric anaesthetist was now in attendance, and epidural anaesthesia was established with the patient in the left lateral position. Four cm of catheter were left in the epidural space. A total of 20 ml 0.5% bupivacaine with fentanyl 100 mg was administered by slow bolus injection, resulting in a sensory block (loss of cold sensation) from T6 to S5. A lower-segment Caesarean section was performed successfully. During surgery crystalloid 2000 ml and colloid 1000 ml, in addition to ephedrine 60 mg and methoxamine 16 mg (18 mg and 4 mg, respectively, prior to delivery) were required to maintain the mother's systolic pressure above 90 mm Hg. During surgery SpO2was between 88% and 92%, although high-¯ow oxygen was poorly tolerated. The infant had Apgar scores of 5 and 9 at 1 and 5 min respectively, and was transferred to the neonatal unit for observation. Samples of umbilical cord venous blood revealed a fetal pH of 6.96 and base de®cit of 15.9. After surgery, the patient was tachypnoeic (55 bpm) and oxygenation remained poor, with an SpO2 of 90% on 15 litre min±1 oxygen via a facemask with reservoir bag. Analgesia was effective, and the minute volume appeared to be good. Widespread inspiratory crackles were heard on auscultation of the chest, and diffuse pulmonary in®ltrates were present on chest radiograph. There was no signi®cant clinical improvement following a diuresis augmented by furosemide 20 mg; we therefore decided to intubate the patient's trachea to facilitate ventilatory support on the intensive care unit. We performed an awake ®breoptic tracheal intubation following i.v. sedation with midazolam 2 mg and initial nasendoscopy to con®rm patency of the nose. Topical anaesthesia of the airway was achieved using 2% lidocaine gel 10 ml with phenylephrine to the nose, 4% lidocaine gargle, and spray via the ®brescope. The cricothyroid membrane was dif®cult to identify, so a transcricoid injection of local anaesthetic was not used. The procedure was well tolerated and the patient was subsequently transferred to the intensive care unit where the initial diagnosis of chorioamnionitis was con®rmed by the isolation of Group B streptococci from multiple sites, including

placental swabs. Enterococci were identi®ed in blood cultures. A norepinephrine infusion 0.1±0.5 mg kg±1 min±1 was required for 48 h to maintain arterial pressure and urine output. Supplemental oxygen requirements decreased, chest radiograph changes gradually resolved, and mechanical ventilation was stopped after 8 days. On the neonatal unit, the baby was treated with supplementary oxygen and i.v. antibiotics. Mother and baby were discharged home 15 days after delivery, having made good recoveries.

Discussion Rapid arterial desaturation is a feature of obstetric general anaesthesia and was particularly marked in this case. One model of arterial desaturation predicts a time of 170 s for the SpO2 to fall to 85% following the onset of apnoea in the obese patient after pre-oxygenation.1 Our patient was bacteraemic and in labour so further reducing the oxygen store, increasing oxygen consumption and impairing the effectiveness of pre-oxygenation. A diagnosis of lung injury secondary to sepsis was later made on the intensive care unit. If present initially, this would also help to explain the rapid arterial desaturation. We saw no evidence of regurgitation, and aspiration was not suspected. Sodium citrate was the only antacid given in view of the short interval between consultation and surgery. We sometimes use i.v. ranitidine in similar situations and this together with metoclopramide may reduce the risk of acid aspiration, particularly at extubation, although both were inadvertently overlooked in this case. `Negative pressure' pulmonary oedema was thought to be unlikely in the absence of upper airway obstruction. Potential dif®culty with laryngoscopy (Mallampati class 3, weight >90 kg) had been identi®ed in our patient,2 but general anaesthesia was attempted because of the perceived risk of meningitis or extradural abscess from a regional anaesthetic technique. What is the magnitude of this risk? Chestnut noted no cases of meningitis and only one case of epidural space infection in a series of over 500 000 obstetric epidurals (with an assumed bacteraemia incidence of approximately 1%) and suggests that, following antibiotic therapy, regional anaesthesia can be justi®ed in the presence of systemic infection.3 In a series of 531 patients with chorioamnionitis who had undergone regional techniques there were no reports of subsequent epidural or spinal infection.4 Case reports of suspected or proven epidural abscesses are increasingly recognized, although they appear to be particularly associated with prolonged use of catheters in intensive care or in patients with infected wounds.5 Epidural catheterization has been argued to represent a greater infection risk than spinal anaesthesia because of vein damage and the use of an indwelling catheter. Spinal anaesthesia, on the other hand, breaches the meningeal barrier and was avoided in our patient partly for this reason. Evidence from bacteraemic rats supports

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cisternal puncture as a risk for subsequent meningitis.6 Extrapolation of these results to anaesthetic practice in humans is dif®cult, however, because of differences in the site and relative size of the dural puncture, differing organisms and the bactericidal properties of local anaesthetics.7 In children having diagnostic lumbar puncture, subsequent meningitis depends on the type of organism but not on the act of lumbar puncture itself.8 Although large epidemiological series involving tens of thousands of spinal anaesthetics have not found patients with meningitis,9 there are case reports following regional anaesthesia in obstetric patients.10 The causative organisms isolated in these cases do not point to haematogenous spread but rather to contamination from the skin or the operator. Swanson and Madej, reviewing the subject of regional anaesthesia in the febrile parturient, argue that although there is a theoretical risk of seeding infection, this may be outweighed by real bene®ts.11 Cardiovascular problems associated with infection such as relative hypovolaemia and a reduced systemic vascular resistance may also be relative contraindications to regional anaesthesia. In our patient we considered that epidural anaesthesia, with its slower onset, would be easier to manage than a spinal block. The degree of cardiovascular compromise was probably underestimated. Our patient needed signi®cant volume expansion and use of vasopressors to maintain the arterial pressure once the block was effective. Our normal practice is to use phenylephrine boluses of 50±100 mg if ephedrine is ineffective or in the presence of maternal tachycardia.12 Methoxamine was used in this case, although it has been reported to reduce uterine perfusion and increase uterine tone.13 The problems of regional anaesthesia for these patients must be balanced against the problems of failed tracheal intubation. It has been suggested that rapid sequence induction of general anaesthesia in obstetric patients with two or more predictors of dif®cult laryngoscopy, as in our case, should be avoided in favour of a regional technique or awake tracheal intubation.4 It is recognized, however, that anaesthetists often avoid awake tracheal intubation.14 There are several possible explanations for this, which include lack of faith in the predictive factors, lack of skill in awake tracheal intubation, time pressure, and a desire not to subject the patient to unnecessary discomfort.14 An awake tracheal intubation could have been performed at the outset but assistance for this was not requested as the dif®culty of laryngoscopy was underestimated. The presence of frequent strong contractions would also have made it dif®cult for our patient to cooperate. After the failed tracheal intubation attempt, when the consultant with relevant expertise was available, we felt the presence of maternal confusion,

hypoxia and fetal distress would have made the procedure dif®cult and possibly dangerous. Later, awake tracheal intubation was performed under more controlled conditions after delivery of the baby and before transfer to the intensive care unit. We believe our case illustrates the problem anticipated by Chestnut, where overemphasis on systemic infection as a contraindication to regional anaesthesia may inadvertently expose the patient to greater risks associated with failed tracheal intubation.5 When dif®cult laryngoscopy is anticipated, serious consideration should be given to awake tracheal intubation if there are co-existing relative contraindications to regional anaesthesia.

References

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