Circulatory Effects of Succinylcholine in Man

Abstract

SUMMARY The effects of intravenous (standard apnoeic) and intra‐arterial doses of succinylcholinc chloride (SCh) on peripheral circulation (forearm, hand, skeletal musculature, skin, mucosa of the sigmoid colon), arterial blood pressure and heart rate were studied in 15 unanaesthetized and 17 anaesthetized subjects. Standard apnoeic doses of SCh injected intravenously in anaesthetized subjects produced circulatory changes usually of a biphasic character, a sudden initial decrease in peripheral blood flow and heart rate followed by an increase throughout The apnoeic period; there was also a rise in arterial blood pressure. The initial decrease occurred synchronously with the preparalytic activity of the skeletal musculature (twitchings), but unlike the latter also after repeated injections of SCh. The magnitude of the initial decrease was, on an average, 16 per cent for the peripheral circulation, and 7 per cent for heart rate. The subsequent average increase amounted to 16 per cent above the initial control value for the peripheral circulation, 8 per cent (5 mm Hg) for the systolic, 21 per cent (6 mm Hg) for the diastolic and 9 per cent (4 mm Hg) for the mean arterial blood pressures. Doses of SCh which caused local muscular relaxation on continuous infusion into the brachial artery of unanaesthetized subjects also caused an average blood flow increase in forearm and hand of 43 per cent. This blood flow response remained only during the first few minutes, and then gradually decreased to the control level during the course of the next 10–15 minutes. After the second or third repeated intravenous injection of SCh, but not after further injections, a sudden and marked bradycardia sometimes occurred, with a duration of up to 3 minutes. With repeated intravenous injections of SCh in a standard apnoeic dose, the size and duration of both the circulatory reactions and the duration of the apnoeic period gradually decreased (‘tachyphylaxis’). The individual sensitivity to SCh was rather variable. This was particularly evident in patients with a labile and hyperkinetic circulation (‘vasoregulatory asthenia’) in whom the average blood flow increase during continuous intra‐arterial infusion of SCh was considerably higher than in the control group. The circulatory changes after an intravenous injection of an apnoeic SCh dose should be evaluated in relation to the various interfering factors, such as anaesthesia, atropine premedication, endotracheal intubation, positive‐pressure ventilation, hypoxia, hypercapnia, hypothermia during anaesthesia, and acidosis. The possible mechanisms by which SCh exerts its circulatory effects are discussed, especially the direct effects on the vessels and heart and the indirect effects via nervous or humoral mediators. It is concluded that SCh seems to be a general vasodilator substance. A review of the literature shows that the vasodilator effect of SCh also exists in circulatory areas of the body not directly studied in the present investigation. The vasodilatation is partially caused by a ...

The influence of suxamethonium on cardiovascular and respiratory function in the anaesthetized horse

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