Malignant Hyperthermia and Day Stay Surgery

Anesthesia for muscle biopsy to test susceptibility to malignant hyperthermia

Introduction

Malignant hyperthermia is an autosomal dominant pharmacogenetic disorder, characterized by hypermetabolic crisis triggered by halogenated anesthetics and/or succinylcholine. The standard method for diagnosing malignant hyperthermia susceptibility is the in vitro muscle contracture test in response to halothane-caffeine, which requires muscle biopsy under anesthesia. We describe a series of anesthetic procedures without triggering agents in malignant hyperthermia, comparing peripheral nerve block and subarachnoid anesthesia.

Method

We assessed the anesthetic record charts of 69 patients suspected of malignant hyperthermia susceptibility who underwent muscle biopsy for in vitro muscle contracture in the period of 7 years. Demographic data, indication for malignant hyperthermia investigation, in vitro muscle contracture test results, and surgery/anesthesia/recovery data were analyzed.

Results

Sample with 34 ± 13.7 years, 60.9% women, 65.2% of in vitro muscle contracture test positive. Techniques used: peripheral nerve blocks — lateral femoral and femoral cutaneous, latency 65 ± 41 min — (47.8%); subarachnoid anesthesia (49.3%), and total venous anesthesia (1.4%). There was 39.4% failure of peripheral nerve block and 11.8% of subarachnoid anesthesia. Adverse events (8.7%) occurred only with subarachnoid blockade (bradycardia, nausea, and transient neurological syndrome). All patients remained in the post-anesthesia care unit until discharge. Age and weight were significantly higher in patients with blockade failure (ROC cut-off point of 23.5 years and 59.5 kg) and blockade failure was more frequent in the presence of increased idiopathic creatine kinase.

Conclusion

Anesthesia with non-triggering agents has been shown to be safe in patients with malignant hyperthermia susceptibility. Variables such as age, weight, and history of increased idiopathic creatine kinase may be useful in selecting the anesthetic technique for this group of patients.

[Anesthesia for muscle biopsy to test susceptibility to malignant hyperthermia]

INTRODUCTION

Malignant hyperthermia is an autosomal dominant pharmacogenetic disorder, characterized by hypermetabolic crisis triggered by halogenated anesthetics and/or succinylcholine. The standard method for diagnosing malignant hyperthermia susceptibility is the in vitro muscle contracture test in response to halothane-caffeine, which requires muscle biopsy under anesthesia. We describe a series of anesthetic procedures without triggering agents in malignant hyperthermia, comparing peripheral nerve block and subarachnoid anesthesia.

METHOD

We assessed the anesthetic record charts of 69 patients suspected of malignant hyperthermia susceptibility who underwent muscle biopsy for in vitro muscle contracture in the period of 7 years. Demographic data, indication for malignant hyperthermia investigation, in vitro muscle contracture test results, and surgery/anesthesia/recovery data were analyzed.

RESULTS

Sample with 34±13.7 years, 60.9% women, 65.2% of in vitro muscle contracture test positive. Techniques used: peripheral nerve blocks - lateral femoral and femoral cutaneous, latency 65±41minutes - (47.8%); subarachnoid anesthesia (49.3%), and total venous anesthesia (1.4%). There was 39.4% failure of peripheral nerve block and 11.8% of subarachnoid anesthesia. Adverse events (8.7%) occurred only with subarachnoid blockade (bradycardia, nausea, and transient neurological syndrome). All patients remained in the post-anesthesia care unit until discharge. Age and weight were significantly higher in patients with blockade failure (ROC cut-off point of 23.5 years and 59.5kg) and blockade failure was more frequent in the presence of increased idiopathic creatine kinase.

CONCLUSION

Anesthesia with non-triggering agents has been shown to be safe in patients with malignant hyperthermia susceptibility. Variables such as age, weight, and history of increased idiopathic creatine kinase may be useful in selecting the anesthetic technique for this group of patients.

Safe duration of postoperative monitoring for malignant hyperthermia patients administered non-triggering anaesthesia: an update

The postoperative care of malignant hyperthermia (MH) patients is subject to international variation, with a paucity of data in the literature to guide management. Over a series of three studies, our aim was to evaluate whether MH-susceptible patients (and relatives who had not yet been investigated), who had received a non-triggering anaesthetic, could be managed in the same way as the standard surgical population. Following a retrospective study, 206 anaesthetics were administered in a prospective second study to MH-susceptible/related individuals who were monitored for a minimum of one hour in the post anaesthesia care unit and a further 90 minutes in a step-down facility. No problems relating to MH were encountered. The postoperative monitoring time was subsequently changed and, in a third study, patients were managed no differently from standard surgical patients. One hundred and twenty-five anaesthetics were administered with no evidence of problems. This data shows that standard postoperative monitoring times are safe and appropriate in MH-susceptible patients.

Safety of exposure of malignant hyperthermia non-susceptible patients and their relatives to anaesthetic triggering agents

As the reliability of malignant hyperthermia normal in vitro contracture test results has been questioned, this study set out to determine the reliability of malignant hyperthermia normal results in New Zealand. Three hundred and twenty-nine anaesthetics were administered to malignant hyperthermia normal patients, identified through the Palmerston North Hospital malignant hyperthermia database. Anaesthetic records were retrieved and scrutinised for a malignant hyperthermia reaction using the Malignant Hyperthermia Clinical Grading Scale. Patients were exposed to one or more of eight triggering agents and multiple anaesthetic agents were administered in 41% of cases. Six variables were analysed, and although a minority of variables were abnormal in a small number of patients, none of the findings supported a malignant hyperthermia reaction. While the analysis was limited by the adequacy of the anaesthesia records, it was supported by negative DNA analysis in 55% of patients. This study supports several previous studies in demonstrating that patients in New Zealand tested non-susceptible to malignant hyperthermia can safely be given triggering agents.

Anesthesia for patients with a history of malignant hyperthermia

PURPOSE OF REVIEW

Malignant hyperthermia-susceptible patients have an increased risk during anaesthesia. The aim of this review is to present current knowledge about pathophysiology and triggers of malignant hyperthermia as well as concepts for safe anaesthesiological management of these patients.

RECENT FINDINGS

Trigger substances and mechanisms have been well defined to date. Anaesthesia can be safely performed with i.v. anaesthetics, nitrous oxide, nondepolarizing muscle relaxants, local anaesthetics as well as xenon. Attention must be directed to the preparation of the anaesthetic machine because modern workstations need longer cleansing times than their predecessors. Alternatively, activated charcoal might be beneficial for elimination of volatile anaesthetics. Day case surgery can be performed in malignant hyperthermia-susceptible patients, if all safety aspects are regarded. Whether there is an association between malignant hyperthermia susceptibility and other disorders is still a matter of debate.

SUMMARY

The incidence of malignant hyperthermia is low, but the prevalence can be estimated as up to 1: 3000. Because malignant hyperthermia is potentially lethal, it is relevant to establish management concepts for perioperative care in susceptible patients. This includes preoperative genetic and in-vitro contracture testing, preparation of the anaesthetic workstation, use of nontriggering anaesthetics, adequate monitoring, availability of sufficient quantities of dantrolene and appropriate postoperative care. Taking these items into account, anaesthesia can be safely performed in susceptible patients.