Significant Decrease In Blood Flow Research Articles

Neurotensin-induced increase in intestinal blood flow in the anesthetized rat.

Cardiac output (CO) and blood flow to major organs were investigated in pentobarbital-anesthetized rats using 85Sr and 141Ce labelled microspheres (MS) of 15 microns diameter injected into the left ventricle. Changes in organ blood flow and CO were measured after intraventricular dextran (3.4 mumol/kg/min) and intravenous neurotensin (NT) at two different rates, 2.5 nmol/kg/min and 0.125 nmol/kg/min. Dextran, known to give anaphylactoid response in rats, reduced the mean arterial pressure (MAP) from 118 +/- 17 to 55 +/- 8 mmHg (p less than 0.001) concomitant with a 56% decline in CO and significant decreases in blood flow to most organs. At 2.5 nmol/kg/min, NT caused a pattern of changes in MAP, CO and organ blood flow similar to that obtained with dextran, and thus consistent with an indirect response via mast cell stimulation. NT injected at 0.125 nmol/kg/min resulted in a significant increase (30%) in blood flow to the small intestine (p less than 0.01) without changes in MAP or CO. Vascular resistance decreased by 30% in the small intestine (p less than 0.01) and by 20% in the large intestine (p less than 0.05). The results show that circulating NT, at concentrations below those eliciting hypotension, enhances intestinal blood flow without significant changes in other organs.

Cerebral blood flow changes in orthostatic dysregulation fainters

The changes in blood flow of both the internal carotid and the vertebral artery during orthostatic test with or without fainting attack were studied in 25 healthy children and 30 patients with orthostatic dysregulation (OD). In healthy children and non-fainted OD patients, no change in blood flow occurred in either the internal carotid artery or the vertebral artery during orthostatic test. On the other hand, a significant decrease in blood flow of the internal carotid artery and/or the vertebral artery occurred during fainting of OD patients. These data suggest that three mechanisms might be involved in fainting of OD patients; a decrease in blood flow of the internal carotid artery, the vertebral artery and a decrease in blood flow of both these arteries.

Haemodynamics of the delayed skin flap: a total blood-flow study

Pedicle skin flaps in dogs were delayed and venous outflow measured at various times following a delay procedure. An initial small but significant decrease in blood flow was noted in the first 48 hours postoperatively in several flaps suggesting that a denervation supersensitivity-arteriovenous shunt mechanism may be active at this time. In all flaps after the second day, total flap blood flow markedly increased compared to the initial measurement. This suggests that the most significant haemodynamic event occurring during the delay period is the development of vascular collaterals.

Mild hypothermia: Its effect on cardiac output and regional perfusion in the neonatal piglet

Cardiac output and regional perfusion was measured in neonatal piglets using radionuclide labeled microspheres. Measurements made at normal core body temperature (38-39.5 degrees C) were compared to those obtained after a 4-5 degrees C reduction in temperature. There is a significant reduction in cardiac output and in the myocardial, renal, pancreatic, and adrenal blood flow. The separated layers of the gastrointestinal tract wall are subject to varying decreases in blood flow. The mucosa of the distal small intestine demonstrated the most significant decreases in blood flow during mild hypothermia.

GASTROINTESTINAL BLOOD FLOW DISTRIBUTION IN COLD-EXPOSED SHEEP

The influence of acute and chronic cold exposure on the distribution of cardiac output to the gastrointestinal tract was measured in adult sheep (35–50 kg) using radioactive microspheres containing 141Ce and 113Sn. Groups of four sheep were exposed in controlled temperature chambers to either (1) control temperature, 18 °C for 10–12 wk; (2) acute cold, exposure to 3 °C for 12 h; (3) chronic cold, exposure to 3 °C for 10–12 wk. In the control, acute cold and chronic cold treatments, respectively, 26.4, 20.5 and 19.4% of cardiac output was distributed to the gastrointestinal tract. The estimated amount of blood flow (mL/100 g wet tissue/min) to the total gastrointestinal tract was not significantly different among the three treatment groups (67 mL/100 g/min for the control versus 62 and 50 mL/100 g/min, respectively, for the acute cold and the chronic cold sheep). However, there was a significant decrease in blood flow to the reticulo-rumen of the acute cold- and chronic cold-exposed sheep (34.0 and 37.8 mL/100 g wet tissue/min for the acute and chronic cold sheep versus 56.0 mL/100 g/min for the control sheep). The redistribution of gastrointestinal blood flow induced by exposure to cold may be a factor in reduced nutrient absorption in cold-exposed ruminants.

Circulatory responses to systemic infusions of estrone and estradiol-17α in nonpregnant, oophorectomized ewes

Uterine arterial blood flow dose-response curves to systemic infusions of either estrone (E1) or estradiol-17α (E2α) were determined in ten oophorectomized, nonpregnant ewes. Maximum uterine blood flow occurred with 5 μg per kilogram of E1 and ≥ 20 μg per kilogram of E2α. Total uterine blood flow measured with isotope-labeled microspheres rose more than tenfold following 30 μg per kilogram of either estrogen, as did blood flow to the myometrium, endometrium, and uterine caruncles (p < 0.05). Distribution of uterine blood flow was unaltered. Cervical and vaginal blood flows increased ten-to twenty-fold with E1 and E2α, while mammary gland blood flow rose 54 and 77 per cent. Significant increases in adrenal and thyroid blood flows were documented. The only significant decrease in blood flow occurred in the pancreas (− 13 per cent; p < 0.05) following E2α infusion. At the dose studied, E1 and E2α are potent vasodilators of reproductive tissues, especially the cervix and vagina. As they appear to be the major estrogens during ovine pregnancy, it is likely they participate in the preparation of these tissues for parturition.

Effect of phentolamine on the somatostatin-induced inhibition of glucagon and insulin secretion

Synthetic cyclic somatostatin was infused into either the cranial pancreaticoduodenal artery or the femoral vein of anesthetized dogs with or without previous administration of phentolamine. Somatostatin infused into the pancreatic artery at a dose of 50 ng/kg/min for 10 min caused significant decreases in blood flow and plasma basal concentrations of both glucagon and insulin in the cranial pancreaticoduodenal vein, resulting in a profound decline of bihormonal output during the infusion. Arterial plasma glucose was not reduced during the administration of somatostatin in the pancreatic artery. These somatostatin-induced decreases failed to be eliminated by a 0.2 mg/kg injection of phentolamine into the femoral vein followed by a 9-min infusion of this α-adrenergic blocker (0.02 mg/kg/min) into the pancreatic artery immediately prior to the somatostatin administration. An inhibition of glucagon and insulin output and a fall of plasma glucose caused by somatostatin (1.7 μg/min) infused into the femoral vein for 30 min also were not abolished by a prolonged and simultaneous infusion of phentolamine (0.2 mg/min) into the femoral vein over a period of 2 hr. These results indicate that α-adrenergic receptor mechanisms do not play a major role in the inhibition of islet glucagon and insulin secretion by somatostatin.

Circulatory response to systemic infusion of norepinephrine in the pregnant ewe

Seven pregnant ewes from 100 to 137 days of gestation were infused with systemic doses of norepinephrine and uterine arterial flow dose-response curves were determined. A constant infusion of norepinephrine at a mean rate of 0.24 μg per minute per kilogram led to a 39.3 per cent decrease in total uterine arterial blood flow as measured with isotope-labeled microspheres while systemic pressure was unaltered. At this dose the reduction in endometrial blood flow (−64 per cent) was significantly greater than that in either the myometrium (−45 per cent) or placental cotyledons (−31 per cent) (p < 0.005). Significant decreases in blood flow to small bowel, skeletal muscle, vagina, cervix, Fallopian tubes, kidneys, spleen, pancreas, and mammary gland were documented. There were no significant increases in blood flow. This study demonstrates that during the period of pregnancy studied, the overwhelming response to norepinephrine is vasoconstriction and that the vascular beds of all the tissues of pregnant uterus are sensitive to the alpha-adrenergic effects of norepinephrine.

Evidence for central innervation of intracerebral blood vessels: Local cerebral blood flow measurements and histofluorescence analysis by the sucrose-phosphate-glyoxylic acid (SPG) method

Local cerebral blood flow using a hydrogen clearance technique and a histofluorescent modification of the glyoxylic acid method (SPG method) were used in rats to study the influence of brain stem centers on intracerebral flood flow. Recording of local cerebral blood flow following stimulation of the locus coeruleus but not of the ventrocaudal nucleus of the lateral lemniscus showed a significant blood flow decrease in anterior brain regions where innervation of ascending adrenergic pathways are known to occur. Adrenergic innervation using the SPG method (sucrose-potassium phosphate-glyoxylic acid) histofluorescence could not be verified in the rat but was evident in the dog and rhesus monkey brain sections examined. The results provide additional evidence suggestive of a role for the locus coeruleus in modulating or controlling intracerebral blood flow in these animals. In addition, histofluorescent visualization of intracerebral vessels in dog and monkey show an association between adrenergic varicosities and arterioles in bilaterally ganglion-ectomized animals. This adrenergic-vascular association was not seen in the rat. The results provide further evidence that central adrenergic innervation from the brain stem may control intracerebral blood flow independent of sympathetic influence.

Effects of local anesthetic agents on the uterine vasculatures and myometrium

Intravascular procaine, lidocaine, mepivacaine, and bupivacaine decrease blood flow to the placental and nonplacental vascular beds of gravid ewes by stimulating vasoconstriction and myometrial contractility. These effects appear to be direct ones since they are not affected by alpha-adrenergic blockade. Dose-response curves determined in nonpregnant ewes indicate that significant decreases in blood flow may occur at arterial blood concentrations encountered clinically. It is proposed that reduced placental blood flow is the cause of fetal bradycardia following paracervical block anesthesia. The implications of these findings in obstetric anesthesia are discussed.

Effect of dihydroergotamine on perpheral circulation during epidural anaesthesia in man.

The effect of intravenous administration of dihydroergotamine (DHE) on regional blood flow in the forearm and calf after pharmacological nerve blockade of the lower body induced by epidural anaesthesia has been studied in 13 subjects. After anaesthesia, DHE induced a significant increase in blood flow in the forearm with intact innervation and a significant decrease in blood flow in the nerve-blocked calf. On the average, the arterial blood pressure increased slightly. The calculated local vascular resistance increased in the nerve-blocked calf, probably due to a direct myogenic constrictive effect of DHE. In the intact forearm, local vascular resistance decreased. The results indicate that DHE exerts a complex effect on resistance vessels in addition to its well-known effect on the capacitance vessels.

The role of selective angiography in the diagnosis and treatment of hepatoportal arteriovenous fistula.

An hepatoportal arteriovenous fistula is a unique complication of abdominal trauma. Of 5 previously reported cases, 4 resulted from penetrating injury and only 1 was attributable to blunt trauma (1, 3, 4, 7, 9). The present report documents the occurrence of hepatoportal fistula following blunt abdominal trauma in a child. The case is significant not only for its rarity, but also as a demonstration of the value of selective angiography in the diagnosis, treatment, and postoperative assessment of this lesion. An 8-year-old girl sustained a fracture of the right femur and abdominal injuries as a result of an automobile accident in January 1968. The child was admitted to a local hospital in hypovolemic shock and underwent exploratory laparotomy. At operation, bleeding from liver and right kidney lacerations was controlled with chromic catgut sutures. Renal shut-down developed postoperatively and the patient was transferred to the W. A. Shands Teaching Hospital. Six weeks later, following a prolonged convalescence, an intravenous urogram showed a nonfunctioning right kidney, and a selective right renal angiogram demonstrated a renal artery aneurysm, laceration of the kidney, and renal vein thrombosis. These studies also suggested the presence of an hepatic artery aneurysm (Fig. 1). The patient was asymptomatic at this time and definitive treatment was deferred. Three months later, repeat right renal angiography showed obliteration of the renal artery aneurysm and atrophy of the lacerated kidney. Selective angiography of the superior mesenteric artery confirmed the presence of an hepatoportal fistula in association with the hepatic artery aneurysm (Fig. 2). On the basis of these findings, an exploratory laparotomy was performed. At operation, an hepatoportal arteriovenous fistula was identified by angiography in the posterior aspect of the right hepatic lobe. Blood flow into this lesion was from both the anterior and the posterior branches of the right hepatic artery. Filling of the aneurysm was no longer visible on a repeat angiogram following suture ligation of the right main hepatic artery. A concomitant right nephrectomy was also performed. The patient's postoperative convalescence was entirely uneventful, and she was discharged two weeks after surgery. Selective mesenteric angiography was performed two months later for postoperative evaluation. Although minimal residual filling of the hepatoportal arteriovenous fistula persisted through small collateral vessels from the inferior phrenic, left hepatic, and left gastric arteries, a significant decrease in blood flow through the fistula and aneurysm was evident (Fig. 3 and 4). The patient was asymptomatic, and studies of hepatic and renal function were normal. She was discharged with periodic evaluation planned for the future. Discussion Recent advances in surgery of the liver have emphasized the importance of an exact preoperative diagnosis as to the type and extent of hepatic injury.

The attenuation by reserpine or guanethidine of the cutaneous vasoconstriction caused by tobacco smoking

The effect of reserpine and guanethidine on the vasoconstriction in the foot induced by smoking 2 cigarettes was studied in normal subjects. Large daily clinical doses of guanethidine or reserpine were given for 2 and 3 weeks, respectively. Blood flow in the foot was measured by venous-occlusion water plethysmography. A pre-drug (control) study was performed on each subject; cigarette smoking produced a significant decrease in blood flow and an increase in vascular resistance in the foot. A statistically significant attenuation of the vasoconstrictor response in the foot to cigarette smoking was found with both drugs, compared to the pre-drug studies. Subjects evidenced a depletion of catecholamines during administration of the agent, by a significant decrease in pulse rate, by postural hypotension, by hypotension after exercise, and by blockade or attenuation of the Valsalva “overshoot.” Since reserpine and guanethidine produced a marked attenuation of the cutaneous vasoconstrictor response to smoking, the conclusion is that cigarette smoking exerts its effects on the circulation in the skin via the sympathetic nerves, and that the release of catecholamines from the adrenal medulla is not important. Patients with peripheral vascular disease who refuse to stop smoking may benefit from the use of catecholamine-depleting agents.

Measurement of uterine blood flow and uterine metabolism: VI. Effects of oxytocic, vasopressor, and vasodepressor drugs on the blood flow to the postpartum uterus in unanesthetized sheep

In a previous report1 we presented data on the effects of spontaneous and oxytocin-induced labor as well as the effects of postpartum uterine involution on uterine blood flow as measured with the electromagnetic flowmeter in unanesthetized pregnant dogs and sheep. It was shown that uterine contraction, regardless of whether it resulted from spontaneous labor or from labor induced with oxytocin, was accompanied by a significant decrease in blood flow which was roughly proportional to the magnitude of the contraction. During uterine relaxation a reactive hyperemia-like phenomenon was observed during which the blood flow returned to, or was slightly higher than, control levels. Immediately after delivery of the fetus and placenta an initial and precipitous fall in uterine blood flow occurred. This was followed by a slower and more progressive decrease which roughly paralleled the involution of the uterus.Since oxytocic drugs are commonly used as hemostatic agents in obstetrics in the postpartum period, the present study was intended to investigate their effects on uterine blood flow after delivery of the fetus and placenta. The studies also include data on the effects of epinephrine, norepinephrine, and hydralazine (Apresoline) on postpartum uterine blood flow.

Peripheral and visceral vascular effects of exercise in the erect position.

In able-bodied young men, the effect of exercise upon the blood flow in forearm, hand, kidney and liver was studied in the erect and supine postures. Work load varied from 3500 to about 9000 kg-m in 15 minutes. The effect of a heavy protein meal in combination with exercise was also investigated. Blood flow in forearm and hand was estimated with venous occlusion plethysmography. Kidney flow was measured with PAH clearance method without catheterization. Liver flow was approximately obtained with Bromsulphalein infusion. Only with a work load of 4000 kg-m or more was there definite reduction in kidney flow, which occurred more readily in the erect posture. No significant decrease of blood flow below resting control level was found in other investigated vascular areas. O2 consumption for pedaling exercises was the same in the two postures. In relation to total cardiac output during heavy exercise, reduction in kidney flow makes a relatively small contribution to circulatory homeostasis. These results were obtained on able-bodied young men under physiologic conditions of exercise and were distinctly different from those on ‘normal patients,’ with forced standing or on the tilt table or under the stress of catheterization with or without sedation. Submitted on January 14, 1957