The known or suspected patient

Malignant-hyperthermia-susceptible patients and their families should not be denied essential surgery on the grounds of malignant hyperthermia alone.

In the majority of situations a malignant-hyperthermia-safe technique will offer little increased risk except in certain rare circumstances when the avoidance of succinylcholine and anesthetic vapors is a potential hazard (e.g. crash induction for full stomach, difficult airway, etc.).

Family screening is recommended to avoid exposing other family members, which may include a large number of individuals, to a less than optimum anesthetic technique. Although family screening may seem a costly, time-consuming, and invasive procedure, only a small proportion of family members need to be screened to identify all malignant-hyperthermia-susceptible individuals ( Ellis.§.t al 1986). There is no undisputed record of a patient who has been shown to be malignant hyperthermia negative by the in vitro contracture test having a subsequent malignant hyperthermia reaction during anesthesia.

Problem areas for malignant-hyperthermia-susceptible patients are as follows:

1. full stomach and rapid-sequence induction;

2. the difficult airway and inability to use inhalational induction;

3. prevention of awareness when using inhalational drugs;

4. provision of a vapor-free anesthetic machine, circuit, and ventilator.

A wide range of anesthetic agents are safe for malignant-hyperthermia-susceptible patients ( Tabje.,2). The anesthetist should have a knowledge and understanding of malignant hyperthermia, and anesthesia should be conducted in a well-equipped hospital operating theater. Adequate basic monitoring (i.e. ECG, non-invasive blood pressure, core temperature, capnography, and pulse oximetry) is essential for all procedures.

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Jfl bat aflHffsle agtm «ufrg kbar* (^wwil h Table 2 Agents which can be used in malignant hyperthermia patients

Ideally, a vapor-free anesthetic machine should be used. However, if this is not available, the vaporizers should be removed from the machine, which should then be flushed with oxygen for about 20 min to remove traces of vapor. A fresh clean breathing circuit should be used. Ventilators should also be flushed with oxygen before use.

There is still some uncertainty about the use of agents such as the phenothiazines following a reported malignant hyperthermia reaction many years ago. In view of their wide use it is unlikely that the phenothiazines play a significant part in triggering a malignant hyperthermia reaction. They are not contraindicated but should be used cautiously. However, they can cause neuroleptic malignant syndrome which clearly is a different condition ( Krivosic-Horber^

The role of both intrinsic and extrinsic catecholamines remains unclear. A study of the effect of ephedrine on in vitro muscle contractures caused by halothane did show an increased response but at considerably greater concentrations than those used clinically. Drugs having a sympathomimetic effect should be used cautiously in malignant-hyperthermia-susceptible individuals.

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