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LABORATORY DIAGNOSIS OF MALIGNANT HYPERPYREXIA SUSCEPTIBILITY (MHS)
Br. J. Anaesth. (1985), 57, 1038-1046
CORRESPONDENCE
LABORATORY DIAGNOSIS OF MALIGNANT HYPERPYREXIA SUSCEPTIBILITY (MHS)
criteria. The laboratory test limits were purposely set to restrict the diagnosis of MHS and M H N to those patients whose laboratory results would be universally acceptable; both of these diagnoses are of great clinical importance and potential danger. An extended MHE group provided a degree of security for the patients because it was agreed that most of these patients would be reported as MH susceptible in the clinical context. MHN 183
MHE 91
EUROPEAN MH
MHS 75
1
2 3 4 " >4 Caffeine (nrmol litre"1) FIG. I. Diagnostic grouping of 349 patients according to original criteria.
MHN 202
GROUP
(Correspondence to F. R. Ellis, Secretary to the European Group, Dept. of Anaesthesia, St. James's University Hospital, Leeds LS9 7TF.) REFERENCES Ellis, F. R. (1984). European malignant hyperpyrexia group. BT. J. Anaesth., 56, 1183. European MH Group (1984). A protocol for the investigation of malignant hyperpyrexia (MH) susceptibility. Br. J. Anaesth., 56, 1267.
DURATION OF FAST BEFORE ELECTIVE SURGERY
1
2
3
4
>4
Caffeine (mnxil fare"1) FIG. 2. Re-grouping of the 349 patients according to new diagnostic limits.
Sir,—Miller, Wishart and Nimmo (1983) reported that consumption of a light breakfast was not contraindicated before surgery and general anaesthesia in light of their findings of no difference between the volume or pH of gastric contents in a fed population compared with a fasted population. In their conclusion they imply that a pH of 3.0 is safe when discussing aspiration of gastric contents.
Downloaded from http://bja.oxfordjournals.org/ at East Carolina University on July 4, 2015
Sir,—Confirmation of clinical diagnosis of malignant hyperpyrexia (MH) and the subsequent family investigation of relatives of MH patients depends at present on a laboratory study of living muscle tissue. Until recently, each laboratory has determined its own limits of normality from control data which are difficult to obtain. The European MH Group encouraged all member departments to adopt the same experiment procedure, enabling a more rapid collection of comparable data than any individual department could have achieved in the same time. The paper reporting the new diagnostic criteria (European MH Group, 1984) described three categories of patient, namely MHS (patients undoubtedly susceptible to MH), MHN (patients undoubtedly not susceptible to MH) and MHE, whose laboratory results were equivocal according to the new
Whilst the fundamental importance of the MHE category was recognized when the protocol was published (Ellis, 1984), it was stated than that this category would be subject to "permanent review", and would be reduced in proportion in the light of experience. If the inheritance of MH is accepted as a dominant characteristic, there should be no equivocal MHE category, as heterozygotes would be identified as MHS and hornozygote normals as MHN. The MHE result must represent a "grey area" of diagnosis which has no genetic relevance. Combining results obtained by member units of the European MH Group since the acceptance of the protocol, 349 patients were diagnostically grouped as follows: 75 (22%) as MHS; 183 (52%) as MHN; 91 (26%) at MHE (fig. 1). Following a review of all 91 MHE patients, and comparing the laboratory result with the case material and the family relationships, it was agreed to adjust the diagnostic limits to those shown in figure 2, namely: MHS: a halothane contracture at 2 % v/v or less AND a caffeine contracture at 2 mmol litre"1 or less; MHN: no halothane contracture at 2% v/v or less AND no caffeine contracture at 2 mmol litre"1 or less; MHE: all other results. This revision can be seen, first, to have rationalized the diagnostic limits between the three categories and, second, to have almost halved the MHE group from 91 to 51 patients (15%). Of the 40 patients removed from the MHE group, 21 have been incorporated into the MHS group, and 19 into the MHN group. It is still envisaged that many of the MHE patients should be accepted as clinically susceptible to MH, pending further elucidation.
CORRESPONDENCE
LABORATORY DIAGNOSIS OF MALIGNANT HYPERPYREXIA SUSCEPTIBILITY (MHS)
criteria. The laboratory test limits were purposely set to restrict the diagnosis of MHS and M H N to those patients whose laboratory results would be universally acceptable; both of these diagnoses are of great clinical importance and potential danger. An extended MHE group provided a degree of security for the patients because it was agreed that most of these patients would be reported as MH susceptible in the clinical context. MHN 183
MHE 91
EUROPEAN MH
MHS 75
1
2 3 4 " >4 Caffeine (nrmol litre"1) FIG. I. Diagnostic grouping of 349 patients according to original criteria.
MHN 202
GROUP
(Correspondence to F. R. Ellis, Secretary to the European Group, Dept. of Anaesthesia, St. James's University Hospital, Leeds LS9 7TF.) REFERENCES Ellis, F. R. (1984). European malignant hyperpyrexia group. BT. J. Anaesth., 56, 1183. European MH Group (1984). A protocol for the investigation of malignant hyperpyrexia (MH) susceptibility. Br. J. Anaesth., 56, 1267.
DURATION OF FAST BEFORE ELECTIVE SURGERY
1
2
3
4
>4
Caffeine (mnxil fare"1) FIG. 2. Re-grouping of the 349 patients according to new diagnostic limits.
Sir,—Miller, Wishart and Nimmo (1983) reported that consumption of a light breakfast was not contraindicated before surgery and general anaesthesia in light of their findings of no difference between the volume or pH of gastric contents in a fed population compared with a fasted population. In their conclusion they imply that a pH of 3.0 is safe when discussing aspiration of gastric contents.
Downloaded from http://bja.oxfordjournals.org/ at East Carolina University on July 4, 2015
Sir,—Confirmation of clinical diagnosis of malignant hyperpyrexia (MH) and the subsequent family investigation of relatives of MH patients depends at present on a laboratory study of living muscle tissue. Until recently, each laboratory has determined its own limits of normality from control data which are difficult to obtain. The European MH Group encouraged all member departments to adopt the same experiment procedure, enabling a more rapid collection of comparable data than any individual department could have achieved in the same time. The paper reporting the new diagnostic criteria (European MH Group, 1984) described three categories of patient, namely MHS (patients undoubtedly susceptible to MH), MHN (patients undoubtedly not susceptible to MH) and MHE, whose laboratory results were equivocal according to the new
Whilst the fundamental importance of the MHE category was recognized when the protocol was published (Ellis, 1984), it was stated than that this category would be subject to "permanent review", and would be reduced in proportion in the light of experience. If the inheritance of MH is accepted as a dominant characteristic, there should be no equivocal MHE category, as heterozygotes would be identified as MHS and hornozygote normals as MHN. The MHE result must represent a "grey area" of diagnosis which has no genetic relevance. Combining results obtained by member units of the European MH Group since the acceptance of the protocol, 349 patients were diagnostically grouped as follows: 75 (22%) as MHS; 183 (52%) as MHN; 91 (26%) at MHE (fig. 1). Following a review of all 91 MHE patients, and comparing the laboratory result with the case material and the family relationships, it was agreed to adjust the diagnostic limits to those shown in figure 2, namely: MHS: a halothane contracture at 2 % v/v or less AND a caffeine contracture at 2 mmol litre"1 or less; MHN: no halothane contracture at 2% v/v or less AND no caffeine contracture at 2 mmol litre"1 or less; MHE: all other results. This revision can be seen, first, to have rationalized the diagnostic limits between the three categories and, second, to have almost halved the MHE group from 91 to 51 patients (15%). Of the 40 patients removed from the MHE group, 21 have been incorporated into the MHS group, and 19 into the MHN group. It is still envisaged that many of the MHE patients should be accepted as clinically susceptible to MH, pending further elucidation.