Title: Outpatient surgery for an MHS
A 25-year-old patient, with a history of malignant hyperthermia based on a clinical episode, has had an uneventful anesthetic for knee arthroscopy under general anesthesia with non-trigger agents.
1. Can the surgery be done in an outpatient facility?
(a) No
(b) Yes
2. What is the minimum time that she should be kept in the PACU/step-
down area since the surgery has gone well?
(a) 4 hours
(b) 2 hours in PACU/step-down area
(c) 1 hour in PACU and 1.5 hours in phase 2 PACU/step down
(d) There is no minimum time required
3. Should he be pretreated with dantrolene?
(a) Yes
(b) No
4. If she has not had a muscle biopsy for MH diagnosis, should she?
(a) No, the clinical episode is enough evidence
(b) Yes, ideally, to confirm
(c) No, because she will be treated as MHS even though the result
may be negative.
(d) Yes, the muscle biopsy test is highly recommended and will help
research for the development of a molecular genetic test.
(e) A and C
(f) B and D
5. Suppose the patient is a medical student and wishes to pursue a
career in anesthesiology. Would you advise her not to?
(a) Yes, because concentrations of anesthetics in an OR could cause MH.
(b) No. Concentrations of anesthetics in an OR that are scavenged
are not a danger.
Answers:
1. B
2. C
3. B
4. F
5. B
Narrative:
An outpatient facility properly stocked with dantrolene and other measures to deal with MH is an acceptable venue for surgery for the MH susceptible.
For many years, MHS patients undergoing routine surgery with non-trigger agents were advised to be kept in the recovery room and /or hospital facility for four hours post-operatively because of concern about a possible MH episode. However, a recent study by the MH group in New Zealand has demonstrated that a much briefer post-op stay is safe (Pollock N. Langton E. Stowell K. Simpson C. McDonnell N. Safe duration of post-operative monitoring for malignant hyperthermia susceptible patients. Anaesthesia & Intensive Care. 32(4):502-9, 2004 Aug).
It is generally advised that confirmatory testing for MH susceptibility is advisable for those who sustained a suspected MH episode. By diagnosing one patient as MHS without confirmation, many in the family are then labeled as MH susceptible as well since the syndrome is inherited in an autosomal dominant manner, perhaps inappropriately.
There is no documented case of MH precipitated by occupational exposure to anesthetic gases such as may be found in the OR. Low concentration of trigger agents (levels found in the OR environment) do not even trigger MH-susceptible animals. Finally, anecdotally, there are several MH-susceptible anesthesiologists /CRNAs who have not had problems working in the OR.
Henry Rosenberg, MD, CPE
Saint Barnabas Medical Center
Livingston, NJ 07039
