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H Ording

Publications and source records attributed to H Ording.

6 recordsLinked to original sources
PubMed1992

Ca(2+)-ATPase and Na(+)-K(+)-ATPase content in skeletal muscle from malignant hyperthermia patients.

The purpose of this study was to determine the concentration of Ca(2+)-ATPase and Na(+)-K(+)-ATPase in biopsies from vastus lateralis muscle of 24 patients, who underwent a diagnostic contracture test for susceptibility to malignant hyperthermia (MH). Ca(2+)-ATPase was quantified as the Ca(2+)-dependent 32P incorporation in whole muscle homogenates. Na(+)-K(+)-ATPase was quantified as the [3H]ouabain-binding capacity in intact muscle samples. These methods avoid isolation of membranes, a procedure that may influence the results due to interindividual variation in recovery. The results show that both enzymes can be determined in (frozen) muscle biopsies weighing 50 mg. Neither the concentration of Ca(2+)-ATPase nor that of Na(+)-K(+)-ATPase differed in biopsies from subjects diagnosed as susceptible (MHS) or nonsusceptible (MHN) to MH. Our data support the view that changes in the concentration of Ca(2+)-ATPase and/or Na(+)-K(+)-ATPase do not play a primary role in the pathogenesis of MH.

Adult↗
PubMed1992

[Malignant hyperthermia].

Malignant hyperthermia (MH) is a life threatening complication following anaesthesia with potent inhalational agents and suxamethonium. The signs of MH are caused by increased metabolism and secondary stimulation of the sympathetic nervous system due to uncontrolled, high intracellular concentrations of calcium in skeletal muscle. The hyperthermia is secondary to the increased energy turnover. Calcium release from the sarcoplasmic reticulum is increased due to a low threshold for release and prolonged opening of the calcium channel upon normal stimulation. The gene encoding the calcium channel is localized on chromosome 19 in humans, and a substitution of cysteine for arginine has recently been described in one family with MH.

Calcium↗
PubMed1992

Sources of variability in halothane and caffeine contracture tests for susceptibility to malignant hyperthermia.

In vitro contracture tests for susceptibility to malignant hyperthermia (MH) were performed in 96 patients according to the protocol of the European MH Group. In addition, tests were performed with halothane 0.44 mmol l-1 and 0.66 mmol l-1, and caffeine 2 mmol l-1, each added as a single bolus dose to fresh specimens. For all tests the size of contractures were recorded, and for the diagnostic tests the halothane and caffeine threshold concentrations were determined (i.e. the minimal concentrations eliciting a contracture of 0.2 g). The caffeine specific concentration (CSC, i.e. the concentration increasing force 1.0 g) and the % increase with caffeine 2 mmol l-1 were calculated from the dose response curves. Various diagnostic criteria in use by the North American MH Group were applied, and diagnostic outcome compared with the result obtained by the protocol of the European MH Group. Thirty-five patients were susceptible to MH (MHS), 33 were non-susceptible (MHN), and 28 had equivocal results of the tests (MHE). Additional tests were made in 34 MHS, 32 MHN, and 26 MHE patients. Contractures elicited by bolus addition of halothane or caffeine were significantly larger than those observed following the same dose of drug added cumulatively (P less than 0.05). Contractures greater than or equal to 0.7 g following halothane 3% (bolus dose) were seen in 78% of MHS patients and 18% of MHN patients, A CSC less than 4 mmol l-1 was elicited in 86% of MHS and 30% of MHN patients, whereas an increase in force greater than or equal to 4% or greater than or equal to 7% was seen in 71% and 34% of MHS patients, respectively, and in none of the MHN patients. Using the criterion of greater than or equal to 0.7 g in the halothane test and greater than or equal to 4% increase in the caffeine test gave the best agreement between diagnostic outcome with the European and North American protocols: All 34 MHS patients (100%) were positive to one or more tests, but so were eight of 32 MHN patients (25%), giving an overall diagnostic agreement of 88%. We conclude that, in our laboratory, the results obtained with the two major protocols for investigation of MH susceptibility are not identical. Patients surviving fulminant MH, however, react abnormally to nearly all the tests. For validation and possibly further standardization of the tests each laboratory must investigate a large number of normal controls and as many patients surviving fulminant MH as possible.

Adolescent↗
PubMed1991

Evaluation of 119 anaesthetics received after investigation for susceptibility to malignant hyperthermia.

A questionnaire was sent to the first 371 patients investigated for MH susceptibility at the Danish MH Register, in order to assess sequelae from the muscle biopsy and possible subsequent anaesthetic complications. The purpose was to evaluate both the safety of anaesthetizing MH-susceptible (MHS) patients without the use of trigger agents, and the safety of giving trigger agents to non-susceptible (MHN) patients. Eighty-eight per cent of patients alive replied to the questionnaire. Of these, 22% complained about discomfort at the site of the biopsy, 2% had experienced problems when needing a subsequent anaesthetic, and 0.9% had had trouble when applying for life or accident insurance. The median observation period for all patients following the muscle biopsy was 5.5 years (range 27 months-11 years). During this period, 36 MHS patients had been anaesthetized 52 times (28 general and 23 regional anaesthetics, data missing in one case) without any MH-related complications. None of the patients had received prophylactic dantrolene. Three MHE patients had received non-trigger anaesthetic agents on three occasions without development of MH. Thirty-five MHN patients had been anaesthetized 64 times, and 13 of these MHN patients had received trigger agents 26 times without any signs of MH. An estimate of the probability of clinical MH developing in MHN patients subsequently anaesthetized with trigger agents was found to be 0-24.7% (95% confidence limits), whereas the probability of clinical MH developing in MHS patients anaesthetized with non-trigger agents was 0-9.7% (95% confidence limits).

Adjuvants, Anesthesia↗