Pathophysiology of overheating in a piglet model: Findings compared with sudden infant death syndrome

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Abstract
Objective: To examine the nature of hyperthermia‐induced pathophysiological changes in an animal model including effects on lung compliance. Methodology: Piglets were randomly assigned to heated or non‐heated groups. Heated animals were warmed to 4°C above normal body temperature while sedated and breathing spontaneously. Cardiorespiratory variables were recorded serially and haematological assessments and blood cultures taken at 0 and 6 h. After 6 h the animals were killed and a limited postmortem was performed. Control animals had all procedures without heating. Results: Heated piglets developed tachycardia, hypotension and a metabolic acidosis in addition to tachypnoea, hypocapnic alkalosis and a neutrophil leucocytosis. Rectal temperature after death fell at the same rate in both groups. Lung histology revealed an excess of lung haemorrhage and alveolar oedema in the heated group. No significant group differences in dynamic lung compliance were demonstrated. Conclusions: The pathological changes that occur during hyperthermia are non‐specific but not incompatible with those found in sudden infant death syndrome. There was no confirmation of the thesis that hyperthermia causes death by altering lung compliance.