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Biomedical subjects

D W Amory

Publications and source records attributed to D W Amory.

At least 37 records · Page 2Linked to original sources
PubMed1985

Regional blood flows during induced hypotension produced by nitroprusside or trimethaphan in the rhesus monkey.

In monkeys anesthetized with 70% nitrous oxide and 0.5% inspired halothane in oxygen, we measured changes in systemic hemodynamics and regional blood flows produced by nitroprusside and trimethaphan. Regional blood flow measurements were made using the radioactive microsphere technique. Control measurements were made before infusion of nitroprusside and trimethaphan into each animal in sequence in amounts adequate to reduce mean arterial pressure to approximately 55 +/- 5 mm Hg. Measurements were made during each drug infusion after a stable period of hypotension lasting at least 30 min. During nitroprusside infusion, cerebral blood flow remained unchanged, but myocardial blood flow increased significantly. However, pressure-rate product, an indirect measure of myocardial oxygen consumption, was unchanged, implying that myocardial blood flow exceeded myocardial oxygen requirement. During trimethaphan infusion, cerebral blood flow decreased, although cerebral metabolic rate for oxygen was unchanged due to increased oxygen extraction by the brain. Trimethaphan also produced a decrease in myocardial blood flow that was in proportion to the decrease in myocardial oxygen requirement as indicated by pressure-rate product. Neither drug produced changes in renal or total hepatic blood flows. We conclude that brain oxygen reserve is decreased during hypotension induced by trimethaphan. Blood flows to other organs are not significantly impaired in monkeys during hypotension to a mean arterial pressure of approximately 55 mm Hg induced by either nitroprusside or trimethaphan.

Animals↗
PubMed1984

The effect of prostacyclin infusion on platelet hemostatic function in patients undergoing cardiopulmonary bypass.

Prostacyclin (PGI2) infusion was studied in patients during cardiopulmonary bypass for coronary artery bypass grafting to assess its capacity to protect platelet hemostatic function. Twelve patients received PGI2 at doses ranging from 20 to 70 ng/kg/min by continuous infusion directly into the bubble oxygenator. Nine control patients were also studied. Platelet counts were not different in the two groups; the platelet count at the completion of the operation was decreased by a mean of 29% in treated patients and 40% in control patients (p greater than 0.15). Bleeding times were uniformly greater than 30 minutes following 30 minutes on bypass in both groups (p greater than 0.5). Also there was no difference in the bleeding times between the treated and untreated groups in the immediate postbypass period (p greater than 0.05). In addition, no difference in transfusion requirements was observed between the treated and control groups. However, plasma levels of platelet factor 4 were lower in the treated patients (p less than 0.05), and, more significantly, blood pressure was lower at all time points in the treated patients (p less than 0.001) despite the greater use of vasopressors. We conclude that PGI2 infusion in this study was of no hemostatic benefit but produced significant hypotension, a potential source of morbidity.

Adult↗
PubMed1983

Regional blood flow during cardiopulmonary resuscitation in dogs using simultaneous and nonsimultaneous compression and ventilation.

We studied regional blood flow (QR) using radiolabeled microspheres and measured hemodynamic variables in 20 anesthetized dogs in normal sinus rhythm and during ventricular fibrillation treated with cardiopulmonary resuscitation (CPR). Nonsimultaneous compression and ventilation CPR (NSCV-CPR) was performed in seven dogs with a pneumatic piston that gave 50 chest compressions/min with an open airway with 10 ventilations at an airway pressure of 33 mm Hg interposed between each fifth and sixth compression. Simultaneous compression and ventilation (SCV-CPR) was performed in seven dogs with the piston and in six other dogs with a circumferential pneumatic vest. Both devices gave 30 compressions/min simultaneously with 30 ventilations that elevated airway pressure to 80 mm Hg., The abdomen was bound during SCV-CPR. Regional blood flow (mean +/- SD) to the cerebral hemispheres, cardiac ventricles, and kidneys, expressed as ml/min/100 g tissue, was 3.1 +/- 4.0, 3.4 +/- 3.3 and 1.5 +/- 1.5, respectively, during NSCV-CPR; 11.5 +/- 5.9, 4.9 +/- 4.7 and 2.7 +/- 2.7 during SCV-CPR (vest); and 16.2 +/- 7.2, 11.0 +/- 4.0 and 20.1 +/- 20.2 during SCV-CPR (piston) (all p less than 0.05 compared with NSCV-CPR). These results indicate that QR to all organs studied is reduced below normal sinus rhythm levels during CPR for ventricular fibrillation, QR to the brain is proportionately greater than QR to the heart and kidneys, and QR to the brain is greater with both forms of SCV-CPR than with NSCV-CPR.

Animals↗
PubMed1982

Transpulmonary polymorphonuclear leukocyte number after cardiopulmonary bypass.

Polymorphonuclear leukocyte (PMN) numbers were determined in samples of central venous or pulmonary artery blood and in simultaneously drawn samples of systemic arterial blood 5 min before institution of cardiopulmonary bypass (CPB) and 5 min after the termination of CPB in 10 adult patients. In only 2 of 10 patients was the systemic arterial PMN number lower than that in central venous or pulmonary arterial blood in the post-CPB period. The results suggest that intrapulmonary PMN sequestration, reported to be a frequent consequence of complement activation during CPB, is a transient and self-limited phenomenon in most persons.

Adult↗
PubMed1981

Lidocaine and pentylenetetrazol seizure thresholds in cats are not reduced after enflurane anesthesia.

Some previous reports indicate that the excitability of the brain may be increased for days following enflurane anesthesia. The authors investigated this possibility in cats by determining whether or not pentylenetetrazol- (Metrazol) or lidocaine-seizure thresholds decreased after repeated enflurane exposure. The lidocaine-seizure threshold was bracketed in 4 cats, and the pentylenetetrazol-seizure threshold was bracketed in another 4 cats. Each cat was then exposed to 4 per cent enflurane for 2 hours on 4 successive days. Twenty-four hours after the last enflurane exposure, the cats were injected with the previously determined subthreshold dose of pentylenetetrazol (6.4 mg/kg, on the average) or lidocaine (7.8 mg/kg, on the average). No cat convulsed. It was therefore concluded that under our experimental conditions, repeated enflurane exposure does not increase the sensitivity to drugs which nonselectively excite the central nervous system (e.g., pentylenetetrazol) or to drugs which mimic temporal lobe epilepsy (e.g., lidocaine). This finding cast doubt that brain excitability is increased in the post-enflurane anesthetic period.

Anesthesia↗
PubMed1980

Effect of total sympathetic blockade on plasma renin activity during surgery.

The interaction of sympathetic blockade and decreased mean arterial pressure on plasma renin activity during surgery was studied in dogs. Plasma renin activity was measured during lumbar laminectomy before and after sympathetic blockade produced by subarachnoid spinal anaesthesia. Plasma renin activity was significantly increased during laminectomy. Twenty minutes after sympathetic blockade there were marked decreases in mean arterial pressure and plasma renin activity; but with mean arterial pressure continuing to decline, plasma renin activity showed moderate increases at 50 minutes after sympathetic blockade. It is concluded that increases in plasma renin activity seen during surgical operations can be attenuated by sympathetic blockade produced by subarachnoid or epidural spinal anaesthesia, although decreases in mean arterial pressure resulting from the sympathetic blockade continue to provide a stimulus for renin secretion.

Animals↗
PubMed1980

Effects of circulatory arrest and rewarming on regional blood flow during surface-induced hypothermia.

Regional blood flow and distribution of cardiac output (CO) were evaluated by the radioactive microsphere technique in rhesus monkeys during surface rewarming following the induction of deep hypothermia (20 degrees C.) under deep ether anesthesia. A comparison of animals subjected to 30 minutes of circulatory arrest and those not arrested revealed cerebral, coronary, and renal vascular resistance and flow patterns consistent with a hyperemic response to circulatory arrest at 20 degrees C. Throughout rewarming cerebral and coronary absolute flows tended to be at or above the flows noted at comparable cooling temperatures in a previous study. Renal flow fraction (% Qt) were well preserved during rewarming to 30 degrees C., but a decrease was observed thereafter. Carcass (muscle, skin, bone) %Qt was also reduced following rewarming, especially in arrested animals. CO appeared to be similar to those noted at comparable cooling temperatures until 30 degrees C. during rewarming; thereafter, CO did not fully recover to awake control levels. These data suggest that regional flow is redistributed from the carcass and renal circulations to cerebral and coronary circulations in response to hemodynamic alterations during surface rewarming. It was concluded that autoregulative responses to both circulatory arrest and hemodynamic factors are elicited during surface rewarming from deep hypothermia to 20 degrees C. with the method described.

Animals↗
PubMed1980

Blood pressure, not cardiac output, determines blood loss during induced hypotension.

Cardiac output characteristically decreases during trimethaphan infusion but is well maintained or increased during sodium nitroprusside infusion. We postulated that at similar levels of mean arterial pressure, sodium nitroprusside might be associated with greater blood loss than trimethaphan due to the increase in cardiac output. We studied 20 young healthy patients scheduled for bilateral sagittal osteotomies of the mandible. Ten subjects received trimethaphan and 10 subjects received sodium nitroprusside. Using halothane (0.8% to 1%) and nitrous oxide (60%) for maintenance of anesthesia, trimethaphan or sodium nitroprusside was infused to maintain mean arterial pressure between 55 to 60 torr. Cardiac output was measured in five subjects in each group. Heart rate and cardiac output increased significantly and total peripheral resistance decreased significantly during sodium nitroprusside infusion when compared to trimethaphan infusion. There were no significant differences in duration of hypotension or in blood loss. We conclude that operative blood loss during induced hypotension is determined by mean arterial pressure, not cardiac output.

Adolescent↗
PubMed1979

Effects of ether anesthesia and surface-induced hypothermia on regional blood flow.

Regional blood flow and distribution of cardiac output (CO) were evaluated by the radioactive microsphere technique in seven rhesus monkeys prior to anesthesia, following the induction of deep ether anesthesia and throughout the cooling course during surface-induced hypothermia to temperatures of 20 degrees C. As given, deep ether anesthesia alone significantly decreased CO 10% to 15% and output fraction (Qt) was decreased to the carcass, increased to the splanchnic circulation (although not statistically significant), and unchanged to other organs, while total vascular (TVR) and organ resistances were reduced. With the addition of cooling, CO progressively decreased. Individual organ Qt's, however, did not change from anesthetized normothermic values; thus organ flows decreased parallel to the reduction of CO as cooling progressed. TVR and organ vascular resistances increased to levels in excess of 150% of anesthetized precooling values, apparently as the result of viscosity rather than vascular changes.

Anesthesia, Inhalation↗
PubMed1979

Effects of glucagon on regional blood flow during cardiogenic shock.

We studied the effects of two dosage levels of glucagon infusion on systemic hemodynamic and regional blood flow measurements during experimental cardiogenic shock in monkeys. Cardiogenic shock was induced in monkeys by embolization of coronary arteries with glass microspheres. Glucagon 1 microgram/kg/min was infused in five monkeys and five remaining monkeys received glucagon infusion at 10 micrograms/kg/min. Radioactive microsphere technique was used to measure regional blood flows. During cardiogenic shock, there were significant decreases in heart rate, mean arterial pressure, cardiac output and rate of rise of left ventricular pressure and significant increases in total peripheral resistance. Blood flows to the heart, brain, kidney and splanchnic bed were markedly reduced. Neither dosage level of glucagon produced any significant improvement in systemic hemodynamic or regional blood flow values. Glucagon produced only nonsignificant increases in splanchnic blood flow during cardiogenic shock. These findings suggest that glucagon infusions in dosages of 1 microgram/kg/min and 10 micrograms/kg/min do not improve systemic or regional hemodynamic status in severe cardiogenic shock.

Animals↗
PubMed1977

Systemic and regional blood flow during epidural anesthesia with epinephrine in the Rhesus monkey.

Hemodynamic and regional blood flow measurements were made in five rhesus monkeys before and 10, 20, 40 and 80 min after induction of high epidural anesthesia (T1) with lidocaine (1%) containing 1:200,000 epinephrine. Following induction of epidural anesthesia with epinephrine, there were significant decreases in heart rate, mean arterial pressure, cardiac output and myocardial and renal blood flow. The percentage of cardiac output received by the brain was significanly increased following epidural anesthesia with epinephrine, thus evidencing autoregulation to maintain cerebral blood flow. Vascular resistance in the lower extremity was significantly decreased during anesthesia, indicating arteriolar dilatation. Also, during anesthesia, the lungs received a significantly increased proportion of the microspheres, suggesting an increased peripheral arteriovenous shunting of microspheres due to the arteriolar dilatation.

Adjuvants, Anesthesia↗
PubMed1976

Systemic and regional blood flow during epidural anesthesia without epinephrine in the rhesus monkey.

The radioactive-microsphere technique was used to determine distribution of cardiac output and regional blood flow in rhesus monkeys before and 10, 20, 40, and 80 minutes after induction of epidural anesthesia with lidocaine (1 per cent) without epinephrine. Four monkeys were studied during low epidural anesthesia (sensory level T10) and five other monkeys were studied during high epidural anesthesia (sensory level T1). During T10 epidural anesthesia. During T1 epidural anesthesia, blood flow (per 100 g tissue) to the lower extremity was significantly increased 10 minutes after induction of anesthesia. There was no other significant change in regional blood flow during T10 epidural anesthesia. During T1 epidural anesthesia, blood flow to the heart was significantly reduced at 10 minutes, blood flow to the liver was significantly reduced at 10 and 40 minutes, blood flows to kidneys and miscellaneous organs (lymph nodes, salivary glands, etc.) were significantly reduced at 10, 20, and 40 minutes, and blood flow to the brain was significantly reduced throughout anesthesia. Vascular resistance in the lower extremity was reduced in each monkey following epidural anesthesia, indicating arteriolar dilatation. Also, during both levels of anesthesia, the lungs received an increased proportion of the microspheres, suggesting an increased periopheral arteriovenous shunting of microspheres due to the arteriolar dilatation.

Anesthesia, Epidural↗
PubMed1975

Systemic and regional blood-flow changes during spinal anesthesia in the rhesus monkey.

The radioactive microsphere technique was used to determine the distribution of cardiac output and regional blood flow in rhesus monkeys before and 10,20,40, and 80 minutes after induction of spinal anesthesia. Five monkeys were studied during low spinal anesthesia (sensory level T10) and five other monkeys were studied during high spinal anesthesia (sensory level T1). Each monkey served as its own control. There was no significant change in regional blood flow during T10 spinal anesthesia. During T1 spinal anesthesia, blood flow (per 100 g of tissue) to kidneys was significantly reduced at 20, 40, and 80 minutes, blood flows to liver and carcass were significantly reduced at 20 and 40 minutes and blood flows to miscellaneous organs (lymph nodes, salivary glands, etc.) were significantly reduced throughout anesthesia. Blood flows to heart, brain, and lower extremity during T1 spinal anesthesia showed only non-significant changes. Vascular resistance in the lower extremity was significantly reduced during both levels of spinal anesthesia, indicating arteriolar dilatation. Also, during both levels of anesthesia, the lungs received an increased proportion of the radioactive microspheres, suggesting increased peripheral arteriovenous shunting of microspheres due to the arteriolar dilatation.

Anesthesia, Spinal↗
PubMed1975

Comparison of the cardiopulmonary effects of subcutaneously administered epinephrine and terbutaline in patients with reversible airway obstruction.

The cardiopulmonary effects of epinephrine and terbutaline were compared in a doubleblind crossover study in 23 subjects with chronic obstructive airway disease. On each of three days each subject received a single subcutaneous dose of saline, 0.25 mg of epinephrine or 0.5 mg of terbutaline. Treatment with epinephrine produced significant increases in forced vital capacity (FVC), forced expiratory volume in one second (FEV-1), maximal expiratory flow rate (MEFR) and maximal mid-expiratory flow (MMEF). Terbutaline caused even more pronounced increases in all four parameters and exhibited a longer duration of action. Neither drug altered arterial pH, arterial oxygen pressure (PaO-2), or arterial carbon dioxide pressure (PaCO-2). With regard to cardiovascular effects, no alterations in either systolic or diastolic pressure were observed. Administration of epinephrine and terbutaline caused statistically significant increases in heart rate. The effect of terbutaline was more pronounced that that of epinephrine. In addition, terbutaline caused a heart rate-related depression of the T-wave of the lead 2 ECG. Neither drug altered any of the hematologic, hemochemical or urinary parameters monitored before and after treatment. Side effects were seen in eight subjects after administration of saline solution, in 13 subjects after epinephrine and in 19 subjects after terbutaline. None of these side effects was considered clinically serious and none required treatment. It is concluded from this study that subcutaneously administered terbutaline is a more effective bronchodilator than epinephrine.

Adult↗