We studied the effects of a cold pressor test on the plasma catecholamine levels of ten patients undergoing coronary angiography, to determine whether the pressor changes were related to adrenergic activity. To investigate the relative contribution of adrenal medullary catecholamine release, we subjected two adrenalectomised volunteers to the same test. Arterial blood was assayed for dopamine (DA), adrenaline (A) and noradrenaline (NA). We found significant rises in the levels of all three catecholamines in the angiography patients, accompanied by a significant elevation in arterial blood pressure. In both the adrenalectomised patients a rise in blood pressure was seen but no significant rise in plasma catecholamines could be demonstrated. We postulate that although adrenal medullary catecholamine release occurs in response to the cold pressor test, the blood pressure elevation is independent of such adrenal activity. Sampling radial arterial blood may not reflect changes in plasma levels of peripherally released NA.
The changes in the plasma concentrations of noradrenaline, adrenaline and dopamine, during tracheal intubation, were studied in 17 patients. Nine patients received pancuronium and eight alcuronium to produce neuromuscular blockade. In the patients receiving pancuronium, intubation of the trachea was accompanied by an increase in mean arterial pressure, and in the plasma concentrations of noradrenaline and adrenaline. In the alcuronium group, there were no significant changes in the plasma concentrations of any catecholamine, nor any change in mean arterial pressure in response to intubation of the trachea.
Tracheal intubation can be accompanied by significant increases in arterial pressure, heart rate and the plasma levels of noradrenaline and adrenaline. The drugs used at induction can enhance or attenuate these responses. In nine patients who had received gallamine, intubation was associated with a 45% rise in mean arterial pressure, a twofold rise in plasma adrenaline and a 49% rise in plasma noradrenaline concentration. When a mixture of pancuronium and alcuronium (in a ratio of 4: 1 0 by weight) was used in ten patients, blood pressure fell 24 % after induction and rose 49% after intubation. A 24% rise in plasma noradrenaline in response to intubation was also observed. Compared with pancuronium alone, the use of the mixture attentuates the rise in blood pressure and noradrenaline concentration associated with intubation but does not abolish them. In addition, the mixture was associated with a significant fall in blood pressure between induction and intubation, whereas this was not found with gallamine.
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