General anesthesia in tetanus patient undergoing emergency surgery: A challenge for anesthesiologist

Abstract

Tetanus is an acute often fatal disease produced by gram positive obligate anaerobic bacterium Clostridium tetani. Tetanolysin damages local tissue and provides optimal conditions for bacterial multiplication. It is therefore important to perform a wide debridement of any wound suspected of being a portal of entry for the bacteria. Little evidence exists to recommend specific anesthetic protocols. We encountered a child scheduled for fracture both bone forearm with developing tetanus. Initial management done with intravenous (i.v) diazepam, phenobarbitone, and metronidazole. After premedication with midazolam and fentanyl, induction was done by propofol 60 mg, vecuronium 2.5 mg, ventilated with O₂+ N₂O 50:50 with sevoflurane 2% and tracheal intubation was done with 5.5 ID cuffed PVC endotracheal tube. Anesthesia was maintained with sevoflurane 2% and vecuronium intermittently when required. Intraop vitals were stable. On completion of surgery, reversal given and patient was extubated uneventfully and shifted to recovery room. Little evidence exists to recommend specific anesthetic technique for tetanus patient posted for surgery. When present, obvious wounds should be surgically debrided. Ideally patients considered for surgery should undergo anesthesia and surgery before severe autonomic dysfunction develops. Most anesthetic managements are based on limited evidence. However, we used sevoflurane and vecuronium successfully, further study is needed to establish their efficacy and safety. Major challenges lie in the control of muscle rigidity and spasm, autonomic disturbances and prevention of complications.

INTRODUCTION

Tetanus is an acute often fatal disease produced by gram positive obligate anaerobic bacterium Clostridium tetani. Incubation period is 3-21 days. It can enter motor, sensory, and autonomic neurones. Centrally, transmission along the gamma-aminobutyric acid (GABA) and glycinergic neurones is interrupted; and at the level of spinal cord, inhibitory neurones are blocked. The disease is characterized by generalized muscle rigidity, autonomic instability, and sometimes convulsions.

CASE REPORT

We encountered an 8-years-old male child weighing 22 kg admitted for fracture both bone forearm surgery with history of fall from tree 15 days back. Bone was coming out of the wound. He was talking irrelevantly and having hallucinations. While examining, the patient started developing intermittent spasm of upper limbs. Ionized calcium done which was 9.1, total leukocyte count (TLC) 21,500, blood urea 58 mg%, and other routine investigations were normal. He received last tetanus toxoid at 5 year age. Patient had painful spasms, with no trismus. Deep tendon reflexes were brisk, clonus+, and planter was silent. He was given human tetanus immunoglobulin 500 U intramuscluar (i.m), intravenous (iv) diazepam 7.5 mg QID, phenobarbitone 500 mg in 100 ml normal saline (N.S.) slow infusion followed by 100 mg OD, metronidazole 250 mg TDS, dressing changed alternate day and wound condition improved. On 4^th day of admission, patient was posted for surgery. Patient was conscious, oriented, with adequate mouth opening and Mallampatti grade II, heart rate 130/min and blood pressure was 126/74 mmHg. Premedication with inj. midazolam 1.5 mg and fentanyl 50 μg was given. After preoxygenation for 3 min, induction was done by propofol 60 mg, vecuronium 2.5 mg, ventilated with O₂+ N₂O 50:50 with sevoflurane 2% and tracheal intubation was done with 5.5 ID cuffed PVC endotracheal tube. Anesthesia was maintained with sevoflurane 2% and vecuronium intermittently when required. Intraop vitals were stable. On completion of surgery, reversal given and patient was extubated uneventfully and shifted to recovery room.

DISCUSSION

Tetanus is an infectious disease caused by exotoxins tetanospasmin and tetanolysin produced by Clostridium tetani. Tetanolysin damages local tissue and provides optimal conditions for bacterial multiplication. It is therefore important to perform a wide debridement of any wound suspected of being a portal of entry for the bacteria.[1] Tetanus is classified into five grades according to presence or absence of five criteria, that is, lock jaw, incubation period of 7 days or less, fever within 24 h of development of lock jaw, presence of spasm, and period of onset 48 h or less.[2]

Hypoxemia in tetanus is common because of a restrictive defect from chest wall rigidity leading to atelectasis, ventilation perfusion mismatch, and increased bronchial secretions obstructing the airways.[3] Accompanied by increased abdominal pressures and gastrointestinal stasis, even the awake patient is at increased risk of aspiration.[3] Mortality is due to respiratory failure and cardiovascular collapse associated with autonomic instability.[4]

Surgical procedures like debridement, tracheostomy, etc., in tetanus patients are necessary. Little evidence exists to recommend specific anesthetic protocols. Management includes administration of antitetanus human immunoglobulin to bind free toxin, immunization, antibiotics, debridement of wound if needed and control of muscle spasm and autonomic instability.

Patients with mild tetanus should be deeply anesthetized and possibly paralyzed to prevent triggering hypertensive crises and spasms during the procedure.[5] Avoidance of unnecessary stimulation and premedication with sedative and analgesics is mandatory. Initial management of muscle spasms involves sedation and a dark, quiet room. Benzodiazepines, barbiturates, anticonvulsants, narcotics, baclofen, dantrolene,[6] and propofol[7] have been used successfully. Benzodiazepines augment gamma amino butyric acid (GABA) agonism, by inhibiting an endogenous inhibitor at the GABA receptor. Diazepam[8] may be given by various routes, but long acting metabolites (oxazepam and desmethyldiazepam) may lead to cumulation and prolonged coma. Midazolam has been used with less apparent cumulation.[9] Additional sedation may be provided by phenobarbitone (which further enhances GABAergic activity)[10] and chlorpromazine.[11] Baclofen completely relieve spasms when given via the intrathecal route, but carries a significant risk of respiratory depression.[3] The use of dantrolene to control refractory spasms has also been reported.[12]

In case of failure to control spasm by benzodiazepines, nondepolarizing muscle relaxant is used. Nondepolarizing agents occupy the postsynaptic receptors, preventing acetylcholine neuromuscular transmission by competitive inhibition and produce muscle relaxation. Neuromuscular blocking drugs with steroid molecule should be avoided in view of prolonged weakness.[13] Pancuronium could worsen hypertension and tachycardia in severe cases.[14,15] Vecuronium, atracurium, and rocuronium have been used successfully.[7] Individual drugs have not been compared in randomized trials. Depolarizing neuromuscular blocker succinylcholine should be used with caution, as it may trigger hyperkalemic arrest. This may possibly be related to acute renal failure leading to hyperkalemia or myoglobinuria. Sedation with propofol controls spasms and rigidity without the use of neuromuscular blocking drugs.[16]

Spinal anesthesia has been used for lower extremity debridement in a patient with mild tetanus.[17] There are a few literature examining the safety of volatile anesthetics. Volatile anesthetic agents enhance the activity of inhibitory postsynaptic receptors while inhibit excitatory sympathetic channel activity. Sevoflurene relieves tetany and allows airway control and ventilation.[18]

Supraglottic airway devices may further diminish the need for endotracheal intubation. During mask ventilation, a nasal airway can facilitate ventilation even in the presence of masseter spasm.

For patients with severe tetanus, electrolyte derangements from tetanus-induced renal dysfunction should be corrected preoperatively.[3] Invasive monitoring should be secured, and drug infusions for intraoperative management of autonomic storms should be prepared. Ideally, patients should be considered for surgical procedures like debridement and tracheostomy before severe autonomic dysfunction develops.[5]

Control of autonomic dysfunction

Autonomic dysfunction is the most serious complication presenting with labile hypertension, tachycardia, arrhythmia, profuse sweating, pyrexia, increased CO₂, increased catecholamines, and later on hypotension.[19] Propranolol,[20] labetolol, and esmolol have been used successfully.[21] Clonidine reduces sympathetic outflow; thus, reducing arterial pressure, heart rate, and catecholamine release from the adrenal medulla.[1] Other useful effects include marked sedation and anxiolysis. Epidural mepivicaine and spinal bupivacaine[3] have been reported to reduce cardiovascular instability.

Magnesium, a presynaptic neuromuscular blocker, blocks catecholamine release from nerves, and adrenal medulla,[22] is an anticonvulsant and a vasodilator and has been used to treat both spasms and autonomic dysfunction.[13,19] In overdose, it causes weakness, sedation, hypotension, and bradyarrhythmia[7] along with decreased tidal volume, impaired cough, and increased secretions. Regular monitoring of serum magnesium and calcium levels are required and ventilatory support must be immediately available.

Several drugs show potential for use in the future. Sodium valproate inhibits GABA catabolism, thus preventing the clinical effects of tetanus toxin.[23] Dexmedetomidine, an α2-adrenergic agonist, may reduce sympathetic overactivity. Adenosine reduces presynaptic norepinephrine release and antagonizes the inotropic effects of catecholamines.[24]

CONCLUSION

Little evidence exists to recommend specific anesthetic technique for tetanus patient posted for surgery. When present, obvious wounds should be surgically debrided. Ideally patients considered for surgery should undergo anesthesia and surgery before severe autonomic dysfunction develops. Most anesthetic managements are based on limited evidence. However, we used sevoflurane and vecuronium successfully, further study is needed to establish their efficacy and safety. Major challenge lie in the control of muscle rigidity and spasm, autonomic disturbances, and prevention of complications.