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Biomedical subjects

R F Hickey

Publications and source records attributed to R F Hickey.

At least 55 records · Page 3Linked to original sources
PubMed1983

A canine model of acute coronary artery stenosis: effects of deliberate hypotension.

Coronary artery disease is considered a contraindication to inducing hypotension during surgery because the combined effects of stenosis and hypotension in reducing distal coronary artery perfusion pressure might produce myocardial ischemia. To study the effect of deliberate hypotension (mean systemic pressure, 50 mmHg) on regional myocardial perfusion, oxygenation, and lactate extraction, we constricted the left-anterior descending coronary artery (LADCA) in dogs. Two degrees of stenosis were studied: "critical" stenosis, which reduced resting coronary blood flow from 34.4 to 31.2 ml/min and abolished reactive hyperemia of the LADCA in response to 10 s of total coronary artery occlusion; and a more "severe" stenosis, which reduced resting coronary blood flow by 40%. LADCA pressure was measured distal to the stenosis, and LADCA perfusion pressure was obtained by subtracting the left ventricular end-diastolic pressure from the coronary artery diastolic pressure measured past the stenosis. Hypotension was induced by administering sodium nitroprusside, halothane at a high concentration, or trimethaphan. Lactate extraction and oxygen consumption were measured across the myocardium distal to the stenosis (from the coronary artery to the great cardiac vein) and across the whole heart (from the coronary artery to the coronary sinus). Regional myocardial blood flow was measured using radioactive microspheres. A transmural electrocardiogram was obtained from electrodes implanted in the subendocardium and the subepicardium in the distribution of the LADCA distal to the stenosis. Although the combination of critical stenosis and hypotension reduced regional myocardial blood flow and lowered LADCA perfusion pressure to 27 +/- 3 (SE) mmHg, myocardial ischemia did not occur, as evidenced by continued lactate extraction and no redistribution of transmural blood flow or change in ST segment. On the other hand, the combination of severe stenosis and hypotension reduced LADCA perfusion pressure to 17 +/- 2 (SE) mmHG and produced evidence of ischemia by regional lactate production, reduction of the subendocardial/subepicardial flow ratio, and depression of the ST segment.

Animals↗
PubMed1982

Treatment of myocardial ischemia with halothane or nitroprusside-propranolol.

An experimental animal model was used to compare the effect of the two drug interventions on myocardial ischemia. Elevation of the ST segment on epicardial electrocardiogram in response to temporary occlusion of the coronary artery was used as an index of ischemia. For multiple sites distal to the left-anterior descending coronary artery (LADCA), ST segments were obtained, measured, and totaled (sigma ST). The effects of halothane (1.1% end-tidal concentration) were compared with those of a combination of nitroprusside and propranolol. The combination was given in a dosage that produced values for systemic blood pressure, heart rate, and maximal positive left-ventricular dP/dt (LV dP/dt) that were similar to those produced by halothane. Control measurements were obtained during chloralose-urethrane anesthesia. Both drug interventions reduced systemic blood pressure, heart rate, and left-ventricular dP/dt similarly. Occlusion of the left-anterior descending coronary artery alone did not change any of these hemodynamic variables. Although both drug interventions reduced sigma ST, the reduction was statistically significantly greater with halothane than with nitroprusside-propranolol.

Animals↗
PubMed1981

Adrenergic response to morphine-diazepam anesthesia for myocardial revascularization.

To evaluate sympathetic nervous system activity during narcotic-hypnotic "balanced anesthesia," plasma catecholamine concentrations and hemodynamic variables were assessed simultaneously in 10 men with coronary artery disease who received, sequentially, morphine sulfate, 3 mg/kg IV, and diazepam, 0.25 to 0.35 mg/kg IV, for myocardial revascularization surgery. Infusion or morphine sulfate rates of 5 to 10 mg/min significantly decreased both mean systemic arterial pressure (from 98 plus or minus 6 to 84 plus or minus 5 torr, p less than 0.01) and systemic vascular resistance index (from 38 plus or minus 3 to 30 plus or minus 5 units, p less than 0.05). These changes were associated with 2-fold increases in plasma norepinephrine levels (from 246 plus or minus 31 to 488 plus or minus 85 pg/ml, p less than 0.01) and 4-fold increases in plasma epinephrine levels (from 129 plus or minus 20 to 570 plus or minus 182 pg/ml, p less than 0.01). Addition of diazepam further decreased systemic arterial pressure (from 84 plus or minus 5 to 73 plus or minus 3 torr, p less than 0.01) and was associated with significant decreases in cardiac and stroke volume indices when compared with values obtained after morphine sulfate alone. Plasma concentrations of both norepinephrine and epinephrine also declined in association with these hemodynamic changes. Following skin incision, systemic arterial pressure and systemic vascular resistance index increased, the latter to the highest measured value (50 units). Norepinephrine concentrations increased significantly more than it had after morphine-diazepam anesthesia (321 plus or minus 63 pg/ml). It was concluded that the administration oif high dose morphine anesthesia acutely activates the sympathoadrenal system while producing peripheral vasodilation. Diazepam, when used following morphine to assure loss of consciousness, exacerbates the hypotensive effects produced by morphine and is associated with decreased levels of plasma catecholamines. Surgical incision produces significant peripheral sympathetic activation and increases vascular resistance during morphine-diazepam anesthesia.

Anesthesia↗
PubMed1979

Morphine decreases peripheral vascular resistance and increases capacitance in man.

The response of the human peripheral circulation to morphine in large doeses independent of cardiac and respiratory influences has not been delineated. In 28 patients during cardiopulmonary bypass, alterations of peripheral vascular resistance (PVR) and capacitance in response to rapid arterial injection of morphine, 0.5 mg/kg or 1 mg/kg alone, or preceeded by promethazine, 1 mg/kg, naloxone, 10 mug/kg, or naloxone, 20 mug/kg, were recorded over 15 min at a constant perfusion rate. Both doses of morphine decreased PVR by 46 percent at 2 min, with values returning to control at 9 min. When promethazine preceded morphine, the decrease in PVR after morphine was 25 percent. Naloxone did not alter the response. An increase in capacitance of 600 ml observed 5 min after morphine administration did not revert to control after 15 min, and was unaltered by prior administration of naloxone.

Blood Pressure↗
PubMed1978

Chronic low back pain: evaluation and therapy.

Chronic low back pain is a common complaint afflicting a large percentage of the population. More interest is required in solving this problem, which is of large economic proportions. This paper reports some procedures by which this may be achieved.

Back Pain↗
PubMed1977

Denervation of spinal facet joints for treatment of chronic low back pain.

This paper describes a neurolytic technique for the denervation of the posterior lumbar spinal facet joints for the treatment of chronic low back pain. Results are reported of a pilot study, using a simple outpatient procedure and achieved relief of pain in 80% of cases. No major complications were encountered.

Back Pain↗
PubMed1976

The effects of age on baroreceptor reflex function in man.

The relationship of age to baroreceptor reflex activity was determined in 35 healthy volunteers ranging in age from 19 to 65 years. Intra-arterial catheters were placed and blood pressure and pulse rate responses of each subject were observed during a Valsalva maneuver (31 subjects) and during the Pressor Test (33 subjects). The Valsalva maneuver consisted of a forced expiration sufficient to raise a column of mercury 40 torr for 10 seconds. This resulted in a reduction in pulse pressure (Baroreceptor stimulus) during the maneuver followed by a transient overshoot in diatolic pressure (response) following its termination. In comparison to younger subjects, older subjects had a greater reduction in pulse pressure but similar overshoot in diastolic pressure. The pressor test consisted of observing the effect of increasing systolic blood pressure (stimulus) on pulse duration (response) following the intravenous administration of phynylephrine. By relating each systolic pressure to the immediately succeeding R-R interval, a linear relationship was found. Its slope expressed in milliseconds of R-R interval change per torr increase in systolic pressure is an index of baroreflex function. Older subjects have less cardiac slowing compared to younger subjects and a hyperbolic relationship exists between age and slope (r = 0.84, p less than 0.05). These tests indicate that baroreceptor reflex function decreases with aging.

Adult↗
PubMed1976

Systemic hypertension following myocardial revascularization. A method of treatment using epidural anesthesia.

Seven of 12 patients (58%) undergoing myocardial revascularization surgery became hypertensive in the immediate postoperative period. The hypertensive patients had significant elevations in peripheral vascular resistance (22.0 +/- 2.0 S.E. resistance units) compared to measurements in normotensive patients (15.6 +/- 1.3 S.E. resistance units) (p less than 0.05), whereas the heart rates and cardiac indices were similar. Administration of thoracic epidural anesthesia to postoperatively hypertensive patients lowered systemic arterial pressure by decreasing peripheral vascular resistance (p less than 0.005) but not affecting the pulse rate and cardiac index. The ratio diastolic pressure-time index/systemic pressure-time index (DPTI/SPTI), an indirect measurement of subendocardial oxygenation, increased from preanesthetic values of 0.80 +/- 0.08 S.E. to 1.09 +/- 0.09 S.E. (p less than 0.025) after the systemic arterial pressure was lowered in postoperatively hypertensive patients. Hypertensive episodes following myocardial revascularization procedures appear related to increased alpha-adrenergic activity, which products elevation in peripheral vascular resistance. Decreasing peripheral vascular resistance by chemical sympathectomy with thoracic epidural anesthesia lowers the systemic arterial pressure and improves the DPTI/SPTI ratio.

Anesthesia, Epidural↗
PubMed1976

The magnitude and duration of respiratory depression produced by fentanyl and fentanyl plus droperidol in man.

In 10 healthy male volunteers breathing 100% oxygen, we determined the effect of four intravenous dose levels of fentanyl (0.0015, 0.003, 0.006 and 0.009 mg/kg) and two of fentanyl plus droperidol (i.e., Innovar, 0.003 and 0.006 mg/kg of fentanyl with 2.5 mg of droperidol for each 0.05 mg of fentanyl) on PECO2 and the slope of the ventilatory response to imposed increases in PECO2. All doses of fentanyl and fentanyl plus droperidol depressed the slope and shifted the curve to the right. Depression was dose related and was maximum 5 minutes after administration. The slope returned to control by 2 hours postinjection even at the highest narcotic dose. However, the rightward shift of the CO2 response curve require 4 hours to return to control. Droperidol added to fentanyl did not increase or prolong the respiratory depression seen with fentanyl alone at equivalent dose levels. Nausea and emesis occurred more frequently with fentanyl alone and orthostatic hypotension occurred more frequently with droperidol plus fentanyl. Dysphoria was a prominent consequence of fentanyl plus droperidol administration.

Adult↗