PubMed Health⌕ Search

Biomedical subjects

A Coull

Publications and source records attributed to A Coull.

At least 19 recordsLinked to original sources
PubMed1994

Are air inlets necessary with Haemaccel?

Haemaccel is often used for the resuscitation of shocked patients. It is common practice to introduce an air inlet into the plastic container to increase the flow rate. We investigated how much difference an air inlet made. We compared the flow rates with no air inlet, a single air inlet, a 2 x 2 cm hole (equivalent to multiple air inlets) and a pressure infusion cuff. Although the use of an air inlet compared with no air inlet reduced the time to infuse 500 ml by 27 s, the difference was only clinically significant over the final 100 ml. A pressure cuff produced the fastest flow, reducing the time by 68 s. Use of an air inlet, however, precludes subsequent use of a pressure cuff. We recommend that the practice of using air inlets for Haemaccel and other similarly packaged products is abandoned.

Air↗
PubMed1986

Relationship of spinal cord blood flow to vascular anatomy during thoracic aortic cross-clamping and shunting.

No satisfactory explanation exists as to why paraplegia occurs despite distal aortic perfusion during thoracic aortic operations. We studied the hemodynamics, paraplegia rate, and spinal cord blood flow with radioactive microspheres in 17 male adult baboons, with particular reference to the arteria radicularis magna. The groups consisted of control animals, subjected to cross-clamping for 60 minutes, and animals with aorto-aortic shunts operational for 60 minutes. There were no significant left ventricular hemodynamic advantages with shunting. Shunting significantly increased lumbar spinal cord blood flow (p = 0.0009), which correlated with the distal aortic mean pressure (r = 0.59, p = 0.008). However, lower thoracic spinal cord blood flow did not increase during shunting (p = 0.2) and did not correlate with the distal aortic pressure (r = 0.11, p = 0.64). This is due to the vascular anatomy of the anterior spinal artery, which was, as in man, smaller above (0.278 mm) than below (0.744 mm) the entry of the arteria radicularis magna. Resistance to flow, as calculated by Poiseuille's equation, was 51.7 times greater up the anterior spinal artery as compared with down this artery. The vascular anatomy explains the absence of paraplegia in one baboon in the cross-clamp group and paraplegia in one baboon in the shunt group. Thus, distal aortic perfusion protects the spinal cord below the arteria radicularis magna but not above it.

Animals↗
PubMed1985

Comparison of the antihypertensive effect of enalapril and propranolol in black South Africans.

Angiotensin-converting enzyme (ACE) inhibitors are useful antihypertensive agents. Enalapril maleate is a new ACE inhibitor with actions similar to those of captopril but with fewer side-effects. A study was conducted on 19 black South Africans with mild or moderate essential hypertension; enalapril was compared with propranolol as monotherapy or together with hydrochlorothiazide in a 1-year randomized, double-blind, parallel study. Neither enalapril nor propranolol alone produced consistent, significant reductions in blood pressure. There were no significant differences between the blood pressure responses to enalapril and to propranolol (either with or without hydrochlorothiazide). It is concluded that neither enalapril nor propranolol is effective as monotherapy in the treatment of hypertension in South African blacks, but that both require the addition of a thiazide diuretic.

Adult↗
PubMed1984

Effect of antihypertensive therapy on left ventricular function and myocardial perfusion at rest and during exercise.

We studied left ventricular function by equilibrium-gated technetium-99m ejection fraction and global left ventricular perfusion by thallium-201 scintigraphy in 43 patients with mild to moderate hypertension. Patients were studied at rest and during submaximal (approximately 50% of VO2 max) supine bicycle exercise, off therapy and on four forms of therapy for 16 weeks: methyldopa (n = 9); propranolol (n = 9); hydrochlorothiazide (n = 9); and enalapril (n = 16). None of the patients had focal myocardial ischaemia or heart failure. There were no differences between methyldopa, propranolol, hydrochlorothiazide and enalapril in blood pressure responses to exercise. However, heart rate at rest (57 +/- 4.6 beats/min) and during exercise (108 +/- 8.0 beats/min) was significantly lower in patients on propranolol than in other groups (70 +/- 3.9 and 117 +/- 5.5 beats/min for methyldopa; 75 +/- 3.3 and 119 +/- 4.9 beats/min for hydrochlorothiazide; 74 +/- 2.8 and 125 +/- 2.6 beats/min for enalapril). In the propranolol-treated group, mean ejection fraction fell from 55% at rest to 49% during exercise. This suggests that cardiac output is likely to be lower and peripheral resistance higher during exercise in patients on propranolol than on other forms of treatment. There were no significant differences in coronary perfusion responses to exercise, however, or in the ratio of coronary perfusion to rate-pressure product, between any of the groups. These findings suggest that the limitation in exercise tolerance often reported by patients on beta-blockers is not due to coronary insufficiency during exercise, but to an attenuation of the cardiac output response to exercise, together with a raised peripheral vascular resistance.

Adult↗
PubMed1982

Inhibition of adrenaline-forming enzyme in the brain prevents one-kidney, one-clip hypertension and deoxycorticosterone acetate-salt hypertension in the rabbit.

1. Phenylethanolamine N-methyltransferase (PNMT) converts noradrenaline into adrenaline and brain PNMT is elevated in spontaneously hypertensive and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. In view of the evidence for the involvement of central adrenergic neurons in renal hypertension, we measured the blood pressure response in one-clip, one-kidney Goldblatt hypertensive and DOCA-salt hypertensive rabbits to the PNMT inhibitor SK&F 64139, injected into the lateral cerebral ventricles. 2. Intracerebroventricular injection of SK&F 64139 (10 micrograms/kg) significantly attenuated the mean arterial blood pressure rise in one-clip, one-kidney and DOCA-salt rabbits, at 4 and 8 weeks. 3. These findings support the idea the hypertension in this animal model required an intact adrenaline biosynthetic process, and that central catecholaminergic neurons may be involved in the pathogenesis of low-renin dependent forms of hypertension.

Animals↗
PubMed1982

Effects of tiapamil on haemodynamics and myocardial salvage during myocardial infarction in the baboon.

We studied the effects of tiapamil during myocardial infarction in the anaesthetized baboon. 10 animals received placebo and 8 animals the drug. After basal measurements the left anterior descending coronary artery was ligated. Measurements were repeated at 15 min and 2-hourly until the 12th h after occlusion. Placebo or drug (1 mg X kg-1 and 50 micrograms X kg-1 X min-1) was administered 20 min after occlusion. Tiapamil decreased afterload by reducing peripheral resistance. Blood flow to the peripheral ischaemic zone was increased. These effects resulted in myocardial salvage manifest as a reduction in serum creatine kinase (MB) isoenzyme levels and less myocardial damage at 12 h than that predicted for the placebo group by S-T segment mapping 15 min after occlusion.

Animals↗
PubMedDate not supplied

Effect of peroral administration of sotalol on the hemodynamics of the baboon.

We investigated the effect of oral administration of sotalol on coronary and renal blood flow and other hemodynamic parameters of the baboon. Measurements were made in anesthetized baboons under basal conditions and during the intravenous infusion of isoproterenol at rates of 0.5, 1.0, 2.0 microgram. min-1 in an experimental (n = 20) and a control (n = 6) group. Subsequently, sotalol (dose 1-4 mg.kg-1, mean 2.25 mg.kg-1) or placebo was administered. After 2 h the procedure was repeated. Measurements included renal (RBF) and coronary (COR BF) blood flow, cardiac output (CO), heart rate (HR), stroke volume (SV), left ventricular systolic pressure (LVSP), maximum positive dP/dt (dP/dt max), aortic diastolic (APD) and mean (APM) pressures, heart rate-left ventricular systolic pressure product (RPP), and left ventricular stroke work index (LVSWI). RBF and COR BF were determined indirectly from the rate of 133 Xe clearance. In the control group, changes before and after the administration of placebo did not differ significantly for all parameters. In the experimental group, changes after sotalol administration were significantly lower for COR BF, CO, HR, LVSP, dP/dt max, APD, APM and RPP, but were not significantly different for RBF, SV and LVSWI. Beta-blockade had no effect on RBF. The reduction in COR BF was associated with a reduction in RPP (myocardial oxygen consumption). However, the oxygen supply-demand relationship was maintained. Decrease in CO was largely due to reduction in HR since SV (and LVSWI) were unaffected by Beta-blockade.

Administration, Oral↗
PubMedDate not supplied

Sotalol and infarct size after coronary ligation in the baboon.

We investigated the hemodynamic effects and myocardial salvage actions of sotalol during experimental myocardial infarction in the baboon. Ten baboons received placebo and six were given sotalol. In anesthetized open-chest baboons base-line determinations included heart rate (HR), rate-pressure product (RPP), left ventricular dP/dt, aortic pressures, serum creatine kinase MB isoenzyme (CK-MB) activity, and a 16-point epicardial ST segment map. The left anterior descending coronary artery was then ligated and the measurements were repeated at 15-min and at 2-h intervals up to 12 h after occlusion. At 12 h, coronary blood flow and myocardial CK activity were also measured. Twenty minutes after ligation, either sotalol (3 mumol . kg-1 followed by 2 nmol . kg-1 . min-1) or placebo (saline) was administered intravenously. Sotalol reduced HR but not dP/dt or the degree of afterload. The reduction in HR resulted in a significant decrease in RPP (myocardial O2 consumption). Sotalol administration also resulted in a decrease in coronary blood flow (myocardial O2 supply). There were no significant differences between the two groups in serum CK-MB activity or in the extent of myocardial damage, as predicted by the 15-min ST-segment deviations and myocardial CK activity at 12 h. The reduction in myocardial oxygen demand caused by sotalol was accompanied by a decrease in oxygen supply. As a consequence, no significant reduction in myocardial ischemic damage was found in the group given sotalol.

Animals↗
PubMedDate not supplied

Role of catecholamine degradative enzymes and the adrenergic innervation in determining the cerebrovascular response to infused norepinephrine.

Cerebral blood flow responses to intra-arterial infusion of norepinephrine (NE) at 0.55 microgram/kg/min and 1.1 microgram/kg/min were studied in 3 groups of baboons. The flow was measured by the intracarotid 133xenon clearance technique using a computer program to calculate flow (height over area--H/A) flow (initial slope--is) and cerebral metabolic utilization of oxygen (CMRO2). The normal response to NE was to increase flow without significant changes in CMRO2. Blockade of catechol-o-methyl transferase (COMT) produced vasoconstrictor responses to these same NE doses. Monoamine oxidase blockade abolished the normal vasodilation. Denervation of the cerebral circulation with intracisternal 6-hydroxydopamine produced vasoconstrictor responses with flow (H/A) but not with flow (is). It is concluded that the extra-neuronal COMT enzyme is important in limiting the access of blood-borne NE to cerebrovascular constrictor receptors.

Adrenergic Fibers↗
PubMedDate not supplied

Cerebrovascular reactivity and metabolism after subarachnoid hemorrhage in baboons.

Subarachnoid hemorrhage (SAH) was induced in baboons by puncturing the middle cerebral artery. Four to seven days later cerebral blood flow (CBF) responses to changing PaCO2 and to intracarotid infusion of 1.0, 2.5 and 5.0 micrograms of 5-hydroxytryptamine (5-HT)/kg/min were studied using the intracarotid 133xenon clearance technique. Indices of cerebral metabolism were determined by measuring arterio-venous differences for oxygen, pyruvate, lactate and glucose. The results were compared with those from sham-operated baboons. In the sham-operated group normal CO2 reactivity was seen, and 5-HT infusion did not produce any significant change in CBF or cerebral metabolism. By contrast, the group in which SAH was induced showed a significant decrease in CBF and cerebral oxygen utilization, and attenuated CO2 reactivity.

Animals↗
PubMedDate not supplied

The analgesic effect of odour and music upon dressing change.

Vascular wounds may require frequent dressing changes over a long period of time, often involving pain, which may not be adequately controlled with conventional analgesia. Complementary analgesia may be beneficial as an adjunctive therapy. This pilot study presented eight patients with two odour therapies, lavender and lemon, two music therapies, relaxing and preferred music and a control condition, during vascular wound dressing changes. Although the therapies did not reduce the pain intensity during the dressing change there was a significant reduction in pain intensity for the lavender therapy and a reduction in pain intensity for the relaxing music therapy after the dressing change. This supports the use of these complementary therapies, which are inexpensive, easy to administer and have no known side effects, as adjunctive analgesia in this patient population. Earlier administration before dressing change may enhance these effects. Further research is required to ascertain why certain complementary therapies are more effective than others at relieving pain.

Aged↗