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Induced hypotension during anaesthesia can result in deterioration in gas exchange with increases in intrapulmonary shunting and physiological deadspace. Cardiovascular stability has been previously demonstrated with isoflurane-induced hypotension but the effects on gas exchange have not been carefully studied. We have examined the shunt fraction (QS/QT) and physiological dead space to tidal volume ratio (VD/VT) before, during and following deliberate hypotension in twelve patients. Group I (n = 6) received an isoflurane-oxygen-air mixture with an FIO2 of 0.5 while Group II (n = 6) received an isoflurane-oxygen mixture with an FIO2 of 1.0. Mean blood pressure was reduced from 76 +/- 2 mmHg to 47 +/- 2 mmHg in the combined group. Neither QS/QT nor VD/VT changed significantly during the hypotensive state in either group. We conclude that isoflurane induced hypotension is associated with minimal pulmonary derangement.

in six healthy volunteers, integrated evoked electromyography (IEEMG) measured in response to ulnar nerve stimulation was correlated with respiratory function -tidal volume (VT), forced vital capacity ( FVC ), forced expiratory volume in one second (FEVt), maximum negative inspiratory pressure (NIP) Neuromuscular blocking agents are routinely utilized in general anaesthesia to facilitate tracheal intubation and provide adequate relaxation for surgical procedures. Because neuromuscular weakness may lead to hypoventilation and/or upper airway obstruction, not infrequent complications observed in the recovery room, it is important that any residual neuromuscular blockade following a surgical procedure be detected and adequately reversed. J.2 Electrical stimulation of a peripheral nerve with subsequent observation of the mechanical or electromyographic response of its innervated muscle helps to determine the degree of neuromuscular blockade during administration of muscle relaxants. 3-6 Furthermore, correlations between train-of-four and tetanic stimulation and variables of respiratory function have been established. 7-9 However, an inexpensive and reliable, quantitative monitor of mechanical twitch response is as yet CAN J ANAESTH 1990/ 37: 3/pp. 307-12