Relative roles of heart rate and ventricular stroke volume for the regulation of cardiac output during controlled hypotension with sodium nitroprusside in man

Effects of posture, hypotension and locally applied vasoconstriction on the middle ear microcirculation in anaesthetized humans

Studies by laser-Doppler flowmetry of middle ear microcirculation changes induced by physical and chemical stimuli in the animal have only recently been made. This prospective study, performed in humans, was designed to compare the effects of a postural manoeuvre (headup tilt 30 degrees), hypotension and locally applied vasoconstriction on middle ear blood flow during anaesthesia. Circulatory changes provoked by a headup tilt of 30 degrees, and successive intravenous boluses of potent vasodilators, were compared with circulatory changes provoked by locally applied adrenaline, in ten healthy patients in good physical states undergoing middle ear surgical repair. Heart rate and direct arterial pressure were continuously recorded via a radial artery cannula. Middle ear blood flow was continuously recorded via a laser-Doppler probe placed on the promontorium cavi tympani. Metabolic parameters (partial pressure of O2 and CO2 in arterial blood, pH, arterial lactate concentrations) and arterial concentrations of propofol were measured just before and just after the experiment. Headup tilt did not modify heart rate, mean arterial pressure or middle ear blood flow. Vasodilators (nicardipine, nitroprusside, nitroglycerin) provoked a fall in arterial pressure (P < 0.0001, P < 0.0001, P < 0.019, respectively), but did not induce any significant variations in heart rate; variations occurred in middle ear blood flow (P > 0.05, not significant) which were different according to patients and agents. Locally applied adrenaline provoked a fall in the middle ear blood flow (P < 0.0012), with no effect on heart rate and arterial pressure. There were no significant changes in metabolic values, or propofol serum concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of hypotension on cutaneous and subcutaneous blood flow in anaesthetized humans

The aim of this study was to determine the effect of controlled hypotension on subcutaneous and cutaneous haemodynamics in humans. Moderate hypotension was achieved with nitroglycerin (NTG) and sodium nitroprusside (SNP) infusion during narconeuroleptanalgesia in seven patients. Subcutaneous and cutaneous blood flow were measured by a superficial and deep heat clearance (HC) technique. The mean arterial pressure (BPa) decreased by 23%-30% and heart rate (fc) increased but only during NTG infusion (+22%; P less than 0.02). Subcutaneous and cutaneous blood flows remained unchanged despite a significant decrease in calculated cutaneous resistance (NTG: -26%, P less than 0.01; SNP: -34%, P less than 0.02] and subcutaneous vascular resistance changed only with SNP (-31%, P less than 0.02). After hypotension was discontinued the subcutaneous blood flow decreased (-13%, P = 0.05), whereas subcutaneous vascular resistance returned to its control values. An inverse relationship was found between fc and BPa (NTG: r = -0.525, P less than 0.01; SNP: r = -0.622, P less than 0.01) as well as with subcutaneous blood flow (NTG: r = -0.653, P less than 0.001; SNP: r = -0.573, P less than 0.01). In addition, we found oscillatory changes in deep HC values which differed in magnitudes (NTG 0.22 (SEM 0.09) W.m-1.degree C-1 vs SNP 0.42 (SEM 0.1) W.m-1.degrees C-1, P less than 0.01) and frequencies (NTG 0.02 (SEM 0.006) Hz vs SNP 0.01 (SEM 0.002) Hz, P less than 0.01). Despite unchanged blood flow, the effects of controlled hypotension on cutaneous and subcutaneous haemodynamics were different depending on the type of drug. These differences may have been related to counterregulatory responses and/or to direct vascular effects.

Effect of the combination of alinidine and other anti-anginal drugs on heart rate and blood pressure in healthy volunteers

1. Heart rate and blood pressure changes following the administration of alinidine 30 mg alone and in combination with atenolol 25 mg, nifedipine retard 20 mg and glyceryl trinitrate 500 micrograms were investigated in three groups of six healthy male volunteers. 2. Concomitant administration of alinidine and atenolol reduced (P less than 0.05) supine, standing and exercise heart rate when compared with alinidine alone. The maximum reduction in exercise heart rate was 116 +/- 2.4 beats min-1 for the combination vs 129.0 +/- 3.1 beats min-1 for alinidine alone. 3. Supine (3, 4, 8 h) and standing (2 h) systolic BP were also reduced (P less than 0.05) with the alinidine and atenolol combination compared with alinidine alone. Little change occurred in diastolic blood pressure. 4. Alinidine and nifedipine in combination reduced (P less than 0.05) the nifedipine induced increase in heart rate in the supine (2, 4 h) and standing (4 h) position and following exercise (2, 4 h). No further decreases in systolic and diastolic blood pressure occurred with the combination. 5. Alinidine administered 2 h before a glyceryl trinitrate challenge reduced (P less than 0.05) the glyceryl trinitrate induced increase in standing heart rate at all time intervals (1 to 6 min); the maximum reduction occurred at 3 min (105.0 +/- 4.3 (glyceryl trinitrate) vs 86.8 +/- 6.7 beats min-1 (combination]. Systolic blood pressure was further reduced at all time intervals with glyceryl trinitrate taken in the presence of alinidine.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of catecholamine-induced tachycardia with alinidine in the anesthetized dog

Sinus tachycardia is a common complication of beta-adrenergic agonist therapy. A new selective bradycardic agent, N-allyl-clonidine, or alinidine, has been found effective against sinus tachycardia caused by a variety of stimuli. To determine whether it would also control catecholamine-induced sinus tachycardia, the effects of alinidine in two groups of anesthetized dogs treated with either dobutamine, 10 microg/ kg/min, or isoproterenol, 0.1 microg/kg/min, were studied. In both groups, alinidine significantly reduced the heart rate (P < .0001 in the dobutamine group, and P < .005 in the isoproterenol-infused dogs). The other hemodynamic effects of dobutamine were not adversely affected by alinidine, while the isoproterenol-infused dogs had a further afterload reduction when treated with alinidine. It is concluded that alinidine is effective against catecholamine-induced sinus tachycardia, possibly through mechanisms not related to beta-adrenergic receptors.

Acute effects of alinidine on heart rate and blood pressure in healthy subjects and patients with hyperkinetic heart syndrome

The effects of a single dose of alinidine (0.5 mg/kg i.v.), the N-allyl-derivative of clonidine, on heart rate and blood pressure were investigated in healthy volunteers and in patients with hyperkinetic heart syndrome, at rest and during bicycle exercise. In healthy volunteers plasma catecholamine levels were also determined. Alinidine did not change heart rate at rest in the healthy volunteers but it did significantly reduce exercise-induced tachycardia, whereas blood pressure and plasma catecholamine levels were not significantly affected by alinidine, either at rest or during exercise. In patients with hyperkinetic heart syndrome, alinidine reduced heart rate at rest and during exercise to a similar extent as propranolol (0.1 mg/kg i.v.). The blood pressure did not change with alinidine but it was significantly reduced by propranolol. The observation that an alinidine-induced reduction of heart rate occurs without a concomitant fall in blood pressure, and without a clonidine-like symphatho-inhibitory action, is in line with experimental findings suggesting a specific bradycardic action of alinidine under short-term conditions.