BLOOD FLOW IN THE HAND AND FOREARM AFTER PARAVERTEBRAL BLOCK OF THE SYMPATHETIC GANGLIA. EVIDENCE AGAINST SYMPATHETIC VASODILATOR NERVES IN THE EXTREMITIES OF MAN

The effect of indoramin on peripheral blood flow

1 The effect of indoramin, a new hypotensive agent, on peripheral blood flows of six normal subjects was determined and compared to placebo in a double-blind, randomized study. 2 Indoramin (0.25 mg/kg), administered intravenously, resulted in an increased forearm muscle volume as measured by strain gauge plethysmography and an increase in the skin temperature of the hand but not to the skin of the chest. 3 It is concluded that these effects are the result of α-adrenoceptor blockade.

Adrenergic control of the human cutaneous circulation

The cutaneous circulation is influenced by a variety of thermoregulatory (skin and internal temperature-driven) and nonthermoregulatory (e.g., baroreflex, exercise-associated reflexes) challenges. The responses to these stimuli are brought about through vasoconstrictor nerves, vasodilator nerves, and changes in the local temperature of the vessels themselves. In this review, we examine how thermoregulatory influences mediate changes in skin blood flow through the sympathetic nervous system. We discuss cutaneous vascular responses to both local and whole-body heating and cooling and the mechanisms underlying these responses, with the overarching conclusion that sympathetic function plays significant roles in reflex vasoconstriction and vasodilatation and in the responses to both local cooling and local heating of the skin.

Indoramin. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in hypertension and related vascular, cardiovascular and airway diseases

Indoramin is a postsynaptic selective alpha 1-adrenoceptor antagonist used in the treatment of hypertension. In contrast to some other alpha-blockers, animal studies suggest that its blood pressure lowering effect results from relaxation of peripheral arterioles as a consequence of blockade of postsynaptic alpha 1-adrenoceptors. Furthermore, unlike some other alpha-blockers, this lowering of blood pressure is rarely associated with reflex tachycardia or postural hypotension. Therapeutic trials have shown indoramin to be effective in lowering blood pressure in all grades of hypertension: mild and moderate hypertension when used alone, but generally in combination with a thiazide diuretic, and in moderate to moderately severe hypertension when used in combination with a beta-blocker and diuretic. In a few small comparative studies, no significant difference was found in the blood pressure lowering effects between indoramin and methyldopa, propranolol and prazosin. Side effects were similar for indoramin, propranolol and methyldopa; however in the 1 comparative study with prazosin, prazosin produced a lower incidence of sedation. Indeed, the most common side effect with indoramin therapy has been sedation of a mild to moderate and/or transient nature, reported in about 19% of cases. Other side effects which have sometimes led to a withdrawal of indoramin treatment have been dry mouth, dizziness, and in males, failure of ejaculation; however, side effects may be reduced by starting therapy with smaller doses and titrating more gradually.

Relationship between pulse amplitude and thermal exchange in the finger: the effect of smoking

In 24 healthy volunteers finger pulse amplitude and heart rate (HR) were monitored by pulse plethysmography and thermal exchange from the finger and were compared before and after the smoking of a single cigarette. Thermal exchange was measured using a direct calorimeter consisting of a recording bath and a reference bath, both of which were filled with water at 18 degree C. The subject immersed the two distal phalanx of a finger into the recording bath. The water thermal gradient between both baths after 4 min of finger immersion and the maximal value of heat loss from the finger to the water were recorded. Decreases in the water thermal gradient (from 6.06 to 5.33 degrees C, P less than 0.05) in maximal value of heat loss (from 22.5 to 18.75 w.m-2, P less than 0.01) and in plethysmographic wave amplitude (from 25.8 to 14.6 mm, P less than 0.01) and increased HR (from 72 to 83 beats min-1) were observed in smokers. These changes were not statistically significant in non-smokers. Water thermal gradient and maximal value of heat loss correlated with plethysmographic wave amplitude before and after smoking but not with HR in the 24 subjects studied. The present study shows a good relationship between vascular phenomena and thermal exchange in the fingers. The variations of finger pulse amplitude provide an adequate and sensitive adjustment of thermal exchange since the effects of smoking a single cigarette can be detected by both PWA and calorimetric measurements in the finger.