-
25. Malignant Hyperpyrexia Syndrome
- Hong Kong University Press, HKU
- Chapter
- Additional Information
25. Malignant Hyperpyrexia Syndrome Denborough an d Lovel l (1960 ) describe d a n Australia n family , whos e severa l members had died of hyperpyrexia o f sudden onset during, or shortly after, genera l anaesthesia. Suc h complications wer e then referre d t o a s 'ethe r convulsion' , 'post operative hea t stroke ' o r othe r simila r terms . Th e presen t ter m 'malignan t hyper pyrexia ' was introduced b y Gordon (1966) . Since then this syndrome (with a poten tially fata l outcome ) o f abnorma l reaction s t o anaesthesi a ha s bee n increasingl y recognized. Britt and Kalow (1970) reported on 11 5 cases and a fair number of cases have been described from man y countries. Malignant hyperpyrexia nowaday s has to be o n th e lookou t for , guarde d against , recognize d an d treate d promptl y whe n i t occurs and, if at all possible, avoided. Patients with malignant hyperpyrexi a (hyperthermia ) syndrom e (MHS), generally considered a mos t seriou s complication , hav e usuall y receive d suxamethoniu m o r halothane or both . Amongst th e mor e commo n manifestation s ar e a 'triad' , a s described b y Relto n and Britt (1972), consisting of : (a) Rigidity. Thi s occurs in 60-70 per cent of patients below the age of 20 years, who seem to have an inherited muscular abnormality. In the remaining 30-40 per cent of patients, usually ove r th e ag e of 2 0 years, this muscular rigidit y occur s onl y occasionally (Brit t and Kalow, 1970) . (b) Signs of hyper metabolicstate. Thes e occu r early . The y ar e usuall y non-specifi c and include tachycardia, tachypnoea, hyperpnoea, cyanosi s and sweating . (c) Rapid rise in body temperature (by about 1° F every few minutes). The shape of the plotted-rise curve is significant . Other change s include the acceleration o f lactic acid and carbo n dioxid e produc tion as well as a massive mobilization of glycogen from the liver. The consumption of oxygen i s increased an d excessiv e hea t i s generated. Adenosin e triphosphat e i s depleted , causin g a n increas e i n th e permeabilit y o f th e muscl e membrane . Calciu m passes in, while potassium and phosphate pass out. Causes There seems to be no singl e theory abou t th e possible causes, although a n abnor mality in a calcium storing membrane of skeletal and cardiac muscle cells is strongly 354 Anaesthesia and Other Specialties suspected. Th e anaestheti c agen t ma y caus e th e defectiv e membran e t o releas e it s stored calciu m t o th e cytoplasm , thereb y triggerin g sustaine d contraction s o f th e muscle fibres. Heredity seem s t o pla y a prominen t par t an d thi s i s described b y a numbe r o f workers such as Britt, et al (1969) , Britt and Kalow (1970), Denborough an d Lovel l (1960). It was shown that th e genetic abnormality appeare d t o be transmitted a s an autosomal dominan t trai t wit h reduce d penetranc e an d variabl e expressibility . Th e possibility of a multifactorial geneti c disorder, with the pattern of inheritance ranging from recessiv e t o dominan t wit h grade d susceptibilitie s i n betwee n ha s als o bee n suggested (Ellis, et al, 197 7 and Kalow, et al, 1979) . Isaacs an d Barlo w (1970 ) though t tha t susceptibl e member s i n a famil y ma y b e detected by an elevated seru m creatinin e phosphokinase (CPK ) level. However, elevated values for CP K are demonstrated i n only about 7 0 per cent of the susceptibl e people. Member s o f susceptibl e familie s ma y exhibi t abnormalitie s o f muscle s (muscle cramps , squint , ptosi s and eve n kyphoscoliosis). Furthermore , CPK , whe n elevated, shows an overall increase over normal values (of 0-94 \i mol/min/1), while serum aldolas e may likewis e exceed norma l value s (o f 2.2-17 p , mol/min/1). A sub clinical myopathy may also be present. A...