Physiological changes in status epilepticus. Reproduced from Shorvon SD. A handbook of epilepsy treatment, with permission of the publisher, Blackwell Science
| Phase 1: compensation | |||
|---|---|---|---|
| During this phase, cerebral metabolism is greatly increased because of seizure activity, but physiological mechanisms are sufficient to meet the metabolic demands, and cerebral tissue is protected from hypoxia or metabolic damage. The major physiological changes are related to the greatly increased cerebral blood flow and metabolism, massive autonomic activity, and cardiovascular changes | |||
| Cerebral changes | Systemic and metabolic changes | Autonomic and cardiovascular changes | |
| Increased blood flow | Hyperglycaemia | Hypertension (initial) | |
| Increased metabolism | Lactic acidosis | Increased cardiac output | |
| Energy requirements matched by supply of oxygen and glucose (increased glucose and oxygen utilisation) | Increased central venous pressure | ||
| Massive catecholamine release | |||
| Tachycardia | |||
| Increased lactate concentration | Cardiac dysrhythmia | ||
| Increased glucose concentration | Salivation | ||
| Hyperpyrexia | |||
| Vomiting | |||
| Incontinence | |||
| Phase 2: decompensation | |||
| During this phase, the greatly increased cerebral metabolic demands cannot be fully met, resulting in hypoxia and altered cerebral and systemic metabolic patterns. Autonomic changes persist and cardiorespiratory functions may progressively fail to maintain homeostasis | |||
| Cerebral changes | Systemic and metabolic changes | Autonomic and cardiovascular changes | |
| Failure of cerebral autoregulation; thus cerebral blood flow becomes dependent on systemic blood pressure | Hypoglycaemia | Systemic hypoxia | |
| Hyponatraemia | Falling blood pressure | ||
| Hypokalaemia/ hyperkalaemia | Falling cardiac output | ||
| Hypoxia | Metabolic and respiratory acidosis Hepatic and renal dysfunction | Respiratory and cardiac impairment (pulmonary oedema, pulmonary embolism, respiratory collapse, cardiac failure, dysrhythmia) | |
| Hypoglycaemia | Consumptive coagulopathy, | ||
| Falling lactate concentrations | DIC, multiorgan failure Rhabdomyolysis, myoglobulinuria | Hyperpyrexia | |
| Falling energy state | |||
| Rise in intracranial pressure and cerebral oedema | Leucocytosis | ||
The physiological changes listed above do not necessarily occur in all cases. The type and extent of the changes depicted depend on aetiology, clinical circumstances, and the methods of treatment employed.
DIC, disseminated intravascular coagulopathy.