Haemodynamic and neurological responses of ventilated and apnoeic calves to succinyldicholine

Succinyldicholine-induced asphyxia in awake calves led to massive catecholamine release by the adrenal medulla. Hypertension and bradyarrhythmias resulted. Electroencephalograms recorded during periods of succinyldicholine-induced apnoea indicated that calves were probably conscious and under psychic stress for at least 4 min after the onset of apnoea. Electroencephalographic signs indicative of decreased consciousness became evident in one calf only after 4,8 min of apnoea but were absent in 3 calves subjected to maximum periods of apnoea of 4,1; 3,2 and 4,4 min. The latter 3 calves all recovered with no apparent neurological deficit after intravenous injection of plasma pseudocholinesterase.