Detecting susceptibility to malignant hyperthermia.
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Biomedical subjects
Publications and source records attributed to F R Ellis.
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We have studied in 22 patients the effect of adding hyaluronidase to bupivacaine during axillary brachial plexus block (BPB) in a double-blind design. Patients received BPB using bupivacaine 2 mg kg-1 with adrenaline 1 in 200,000, either with or without hyaluronidase 3000 iu, in a volume of 0.5 ml per 2.54 cm of the patient's height. The use of hyaluronidase did not increase the speed of onset of anaesthesia or reduce the incidence of inadequate nerve block. Hyaluronidase produced a significant reduction in the duration of anaesthesia. Changes in grip strength and skin temperature were useful in assessing the onset and progress of BPB.
We are frequently asked if patients, in whom only postoperative pyrexia has been observed, should be considered as potentially susceptible to malignant hyperthermia (MHS). Of 30 patients of this type studied in this Unit, none was shown to be MHS. We consider that postoperative pyrexia alone is unlikely to signify MH.
In a double-blind, randomized, controlled prospective study, 30 grade ASA I/II patients received a continuous i.v. infusion of normal saline or esmolol hydrochloride before induction of anaesthesia and tracheal intubation. Arterial pressure and heart rate were measured to assess the pressor response to laryngoscopy and intubation. The heart rate decreased in the esmolol group before induction of anaesthesia. The pressor response to laryngoscopy was significantly less marked in the esmolol group.
The "K-type" designation is used to describe a patient being investigated for malignant hyperthermia (MH) when concurrent administration of caffeine and halothane induces muscle contracture (rigidity, spasm) in vitro, but when halothane and caffeine given separately produce a normal response. It is accepted in some centres that K-type individuals are susceptible to malignant hyperthermia (MHS). In this paper, the K-type is shown not to correlate with the MH susceptible (MHS) status as accepted by the European MH group.
We have evaluated a spin labelled electron spin resonance technique to identify malignant hyperthermia susceptible (MHS) patients. We studied 19 patients, 10 MHS and nine MHN (normal), using the standard European procedure. We were unable to obtain any evidence that this technique could be used to diagnose MH susceptibility. Furthermore, there was no significant difference in the fluidity of the red blood cell membranes between the two groups, which would have been indicative of a generalized membrane abnormality in MH.
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A 34-year-old female patient developed methaemoglobinaemia following a femoral nerve block using prilocaine. The concentrations of methaemoglobin in the blood of the next eight patients receiving this block were assayed, and found to be significantly increased above baseline concentrations, but very significantly less than the concentration in the patient with symptomatic methaemoglobinaemia. Pulse oximetry was of value in making the diagnosis.
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Malignant hyperthermia may be a human stress syndrome, of which heat stroke is one manifestation. Two men in military service who had episodes of exertional heat stroke, and their immediate family members, were tested for susceptibility to malignant hyperthermia by in-vitro contracture tests on skeletal muscle samples. Muscle from both patients had a normal response to caffeine but an abnormal response to halothane. Muscle from the father of one patient had an abnormal response to halothane, and that from the father of the second patient had an abnormal response to ryanodine. The results indicate that clinical heat stroke may be associated with an underlying inherited abnormality of skeletal muscle that is similar, but not identical, to that of malignant hyperthermia.
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In vitro contracture tests used currently for malignant hyperthermia (MH) do not possess absolute specificity. This is potentially a great problem in the study of the genetic approach which offers the best prospect for the development of a non-invasive diagnostic test for the condition. The calcium release channel of the sarcoplasmic reticulum has been proposed as the site of the MH defect. Ryanodine, which binds avidly to this channel, was shown to differentiate between muscle of MH susceptible and normal patients in terms of in vitro contracture response. This ryanodine contracture response is proposed as a potentially specific in vitro diagnostic test for MH.
An assessment of local anaesthetic blockade of the lateral femoral cutaneous nerve using a standard technique was made. The rate of successful blockade was high, but the area of sensory loss was inconsistent between patients and was more anterior and distal than described in textbooks of anatomy.
Two patients who developed hypermetabolic reactions during anaesthesia and surgery and who were suffering from arthrogryposis multiplex congenita are reported and it is proposed that the reaction is distinct from malignant hyperthermia and independent of the anaesthetic agents used. The implications for anaesthetists involved in the management of patients with arthrogryposis multiplex congenita are discussed.
Conditions for insertion of the laryngeal mask were assessed following induction of anaesthesia with either propofol 2.5 mg/kg or thiopentone 4.0 mg/kg in 80 patients premedicated with diazepam 10 mg. Insertion following induction with thiopentone resulted in a greater incidence of gagging (p less than 0.01). The use of additional induction agent, where necessary, resulted in no ultimate significant difference between the groups for the provision of satisfactory conditions.
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