Decrease In Forearm Blood Flow Research Articles

The dose-response characteristics of the acute non-diuretic peripheral vascular effects of frusemide in normal subjects.

The peripheral venous and arterial effects of frusemide, plasma renin activity and plasma frusemide concentrations were examined during the 15 min period following the i.v. administration of 0, 5, 10, 20, 40 and 80 mg of frusemide in a group of nine salt depleted volunteers. The responses to 80 mg frusemide given orally during the 1 1 h period after administration were also examined. Increases in venous capacitance 5 min after administration of 5 and 10 mg frusemide were observed (P less than 0.05) but no significant increases were apparent after the higher doses. At 10 min, the increases in venous capacitance showed a flat dose response effect with significant increases throughout the dose range (5-80 mg). Decreases in forearm blood flow occurred at 5 and 10 min after frusemide administration at all the doses studied (P less than 0.05) while blood pressure responses at 10 min showed increasing effect with increasing dose. An oral dose of 80 mg frusemide produced a rise in venous capacitance 15 min after administration and a decrease in forearm blood flow during the period 15-60 min without any alteration in heart rate or blood pressure.

Cardiovascular and neurophysiologic correlates of sensory intake and rejection. II. Interview behavior.

ABSTRACTAs part of a three task study of the influence of attentional style on cardiovascular response, 19 normal volunteers were given a 15‐min interview during which systolic and diastolic blood pressure, digital pulse volume, heart rate, and forearm blood flow were recorded. At the same time two observers independently assessed five elements of the subjects' interview behavior; arousal, eye contact with the interviewer, self‐revelation of interview center, attentiveness to the interviewer, and overall transactional engagement in the interview task. When subjects were divided into groups of interview at tenders and nonattenders on the basis of interviewer ratings, attenders had a mean decrease in forearm blood flow and nonattenders a mean increase. These group differences extended across a word identification (sensory intake) and mental arithmetic (sensory rejection) task as well. When subjects were divided into groups of forearm blood flow increasers and decreasers, increasers displayed less attentiveness to the interviewer, less self‐revelation, greater arousal, and less transactional engagement than did decreasers (N=9). Attentiveness to the interviewer and transactional engagement were the two most sensitive behavioral discriminators in comparing the increaser and decreaser groups.

Haemodynamic Effects of Low Doses of Female Sex Steroids

Summary: Haemodynamic changes were monitored serially in 3 groups of healthy young women taking (i) a combined oestrogen‐gestagen oral contraceptive containing a low dose of oestrogen, (ii) an oestrogen alone and (iii) a gestagen alone. Similar significant increases in plasma volume occurred in those women taking the combined preparation and in those taking the oestrogen. A small but significant decrease in forearm blood flow occurred in subjects taking the combined oral contraceptive. Cardiac output, blood pressure, heart rate and hand blood flow did not alter significantly in any of the 3 groups of subjects, while body weight increased in the subjects taking gestagen alone.It is concluded that the combined oestrogen‐gestagen oral contraceptives containing 50 μg. of oestrogen result in minimal haemodynamic side effects, and hence are safer than the older combined preparations containing a higher dose of oestrogen. The increase in plasma volume observed was due to oestrogen rather than gestagen. No additional information was obtained concerning the site of sex steroid action in the cardio‐vascular system.

Cardiovascular response during a word association test and an interview.

ABSTRACTPrevious work has demonstrated a consistent increase in diastolic blood pressure during an interview relative to a word association test. A consideration of normal cardiovascular mechanisms suggests that such increased diastolic pressure could be associated with decreased forearm blood flow. This expectation is at variance with previous studies in which psychological stimuli have been associated only with increased forearm blood flow. Forearm blood flow and pulse rate were measured during rest periods and during a word association test and an interview in 8 normal volunteers and 8 psychiatric inpatients. Twelve of the 16 Ss showed a decrease in forearm blood flow during the interview, thus confirming our expectation. That this decrease is an active response, rather than a passive fall, is suggested by the finding of increased heart rate during the interview. The cardiovascular responses of the patient group differed in some respects from those of the normal group. We hypothesize that the attentional deficit of the schizophrenics in the patient sample may have contributed to this difference.

The role of low pressure baroreceptors in reflex vasoconstrictor responses in man.

Studies were performed on 11 healthy men to evaluate the role of low pressure baroreceptors in the reflex forearm vasoconstrictor responses (plethysmography) to venous pooling produced by lower body negative pressure. Lower body negative pressure (LBNP) at - 5, - 10, - 20, and - 40 mm Hg lowered central venous pressure by 42, 59, 74, and 93%, respectively, and decreased forearm vascular conductance by 24, 29, 34, and 40%, respectively. The decreases in forearm blood flow and conductance during the low levels of venous pooling (LBNP - 5 and - 10 mm Hg) occurred without significant changes in arterial pressure, arterial dP/dt. and heart rate. These results with the low levels indicate that maneuvers which decrease venous return and central venous pressure in man can influence forearm vascular tone without significant changes in the determinants of carotid and aortic baroreceptor activity. During high levels of venous pooling (LBNP - 20 and - 40 mm Hg), significant decreases in arterial pressure and dP/dt and significant increases in heart rate accompanied the further reductions in central venous pressure, forearm blood flow, and forearm vascular conductance. About 73% of the decrease in conductance during venous pooling at LBNP - 40 mm Hg, which was sufficient to decrease arterial pressure and activate high pressure baroreceptor reflexes, occurred during low levels of venous pooling at LBNP - 10 mm Hg without changes in arterial pressure. This suggests that much of the forearm vasoconstriction with the high levels of venous pooling, which were sufficient to decrease arterial pressure, may be accounted for by reflexes originating in areas other than high pressure baroreceptors. The results of these studies suggest that low pressure baroreceptors exert an important influence on forearm vascular tone during decreases in venous return and central venous pressure in man.

Venous constriction in response to head-up tilt in man.

There has been disagreement about the role of the peripheral venous system in cardiovascular adjustments to postural stress in man. In part this seems to be due to the technical difficulty in determining venous distensibility by plethysmographic techniques in situations where concomitant changes in blood flow occur. We have demonstrated in this study that rapid and consistent increases in forearm venous tone assessed by venous occlusion plethysmography do occur on head-up tilt in man, and that they can be readily masked by the parallel marked decrease in forearm blood flow. It is concluded that the peripheral venous system in man is not designed to function only in states of severe stress but rather plays an important role in moment-to-moment adjustments of cardiovascular activity.

Cardiovascular reflexes in tetraplegia.

The effects of bladder stimulation, skeletal muscle spasms and head-up tilting were observed in seven patients with complete cervical cord lesions. Measurements were made on intra-arterial blood pressure, heart rate, hand, forearm and calf blood flow and peripheral venous activity.On bladder stimulation there was an increase in blood pressure and a decrease in heart rate, calf blood flow and hand blood flow; there was venoconstriction. Skeletal muscle spasms caused similar changes.Head-up tilting caused a fall in blood pressure with a rise in heart rate. There was a decrease in forearm blood flow and there was some venoconstriction.

Cardiovascular responses to tilting in tetraplegic man.

1. A study has been made of the effect of head-up tilt on blood pressure, heart rate, forearm blood flow and occluded vein pressure in the hand and foot in non-bedridden patients with chronic, closed, complete, localized traumatic transection of the cervical spinal cord.2. In typical responses the blood pressure fell and the heart rate rose progressively for about 2 min, tending to plateau thereafter. The average falls in mean blood pressure for tilts of +30, +45 and +60 degrees were from 68 to 44, 74 to 36 and 70 to 44 mm Hg respectively, and the corresponding heart rate increases were from 67 to 85, 62 to 97 and 62 to 103 beats/min respectively. One patient lost consciousness when his blood pressure was 29/19 mm Hg and one other patient experienced symptoms suggesting cerebral ischaemia.3. Following the return to horizontal, the blood pressure and heart rate usually returned to their previous values within 1 min and the blood pressure tended to overshoot slightly in the following few minutes. No immediate blood pressure overshoot occurred after the tilt except in association with a spasm of skeletal muscles.4. There was consistently a decrease in forearm blood flow, sometimes to unrecordably low levels and a venoconstriction with postural change and it is argued that these changes are the result of spinal cardiovascular reflexes to peripheral vessels. Following the return to the horizontal position, there was occasionally a large immediate increase in forearm blood flow.5. Following the intravenous administration of 3 mg atropine on two occasions, head-up tilting produced further small heart rate increases.6. Spasms of skeletal muscle occur frequently in these patients and greatly modify the effects of postural stimuli. Bladder percussion also modifies the normal response.

Observations on the effect of external counterpressure on the circulation through the forearm

The effect of exposure of a 15-cm. forearm segment to counterpressures in the range of 10 to 50 cm.H 2O on forearm blood flow was measured in each of 6 subjects. An increase in counterpressure resulted in an approximately linear decrease in forearm blood flow. There was no consistent evidence for the existence of a range of counterpressures over which apparent blood flow remained constant. Results of experiments in which forearm blood flow was measured at counterpressures of 10 and 45 cm.H 2O, during body heating and during the period of elevated blood flow in the forearm after exercise of the forearm muscles, did not demonstrate that exposure to a counterpressure of 45 cm.H 2O, in our apparatus, caused suppression of blood flow through the skin of the forearm. Exposure of the forearm segment to a counterpressure of 45 cm.H 2O for 45 minutes did not result in reactive hyperemia comparable to that induced in skin, at other sites, by periods of arterial occlusion of much shorter duration. Although it may be possible to suppress blood flow in skin, without affecting blood flow in muscle, by applying counterpressure to a short segment of forearm, our experiments indicate that it is not possible to do this in longer segments.