The effects of low-voltage electric shock on respiration in the anaesthetized cat

Airflow (v), expired ventilation (VE), oxygen usage (VO2), carbon dioxide production (VCO2), blood pressure (B.P.) and the electrocardiogram (e.c.g.) were measured before and after applying low-voltage electric shocks (15-110 V a.c., 8-45 mA, 50 Hz) from the forelimb to the opposite hind limb of cats anaesthetized with pentobarbitone. Periods of shock application were either short (0.5-1.5 s) or more prolonged (10-30 s). Respiratory arrest from tetanic contractions of the respiratory muscles was always present throughout the period of shock application. Following the shocks, even those of the shortest duration, marked increases in v, respiratory rate, VE, VO2 and VCO2 were recorded. Some of these measurements were still elevated relative to pre-shock levels 60 min in to the post-shock period. During shocks lasting 10-30 s B.P. usually increased markedly in association with elevated pulse pressure but hypotension with absent pulses was also recorded. Following shocks of these durations both hypertensive and hypotensive phases were distinguished sometimes lasting for up to 30 min. Occasionally, the e.c.g. showed ventricular arrhythmias or cardiac standstill in the immediate post-shock period but it was usual for these abnormalities to revert rapidly to normal sinus rhythm. Hypotension invariably followed short-duration shocks. This study indicates that low-voltage shocks, even those applied for short periods, can induce marked respiratory, circulatory and metabolic reactions. Possible mechanisms to account for these reactions are discussed.