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Biomedical subjects

H Mass

Publications and source records attributed to H Mass.

15 recordsLinked to original sources
PubMed1998

Comox Valley Nursing Centre: from collaboration to empowerment.

The Comox Valley Nursing Centre was initiated as a two year demonstration project by the Registered Nurses Association of British Columbia (RNABC) and funded by the Ministry of Health. The purpose of the project was to demonstrate innovative nursing practice in a primary health care context. Findings from the project were expected to inform provincial health care planning, nursing scope of practice, and health and nursing policy development. A free standing nursing center was planned and implemented through a collaborative effort by RNABC, nurses and community residents. An external team of researchers evaluated the project using a variety of methods, including participatory action research. During the project an innovative nursing practice, based on principles of collaboration, developed and has continued during the extended provincial and regional funding of the Centre. Drawing from the evaluation findings, case studies and using Henneman, Lee and Cohen's (1995) concept analysis of collaboration, this paper describes how the principles of collaboration were actualized or suppressed. The paper examines how collaboration impacted empowerment for nurses, clients and the community. Lessons learned about the reciprocal relationships between collaboration and empowerment, implications for nursing practice, and how the approach can contribute to a better understanding of the impact of collaborative practice approaches on health care delivery are discussed.

British Columbia↗
PubMed1995

N-acetylcysteine diminishes injury induced by balloon angioplasty of the carotid artery in rabbits.

The effect of N-acetylcysteine (NAC) on preventing or ameliorating the injury associated with percutaneous transluminal angioplasty was investigated in rabbits. Carotid artery angioplasty (CA) was performed on 8 control (vehicle-treated) rabbits and 7 rabbits treated with NAC, 250 mg/kg, administered orally in Nutrical paste for 10 days prior to and 10 days following CA. Single blind histologic evaluation of the angioplasty sites demonstrated a significant reduction in the incidence in vessel: 1) inflammation; 2) endothelial damage; 3) thrombus formation; 4) elastic lamina damage in the NAC rabbits. The percentage of control versus NAC treated animals exhibiting damage in each category were: inflammation: 75% vs 14%; endothelial damage: 88% vs 57%; thrombus formation: 88% vs 43%; laminal damage: 63% vs 14%. The results suggest that NAC treatment may be a valuable therapeutic agent in effectively preventing or reducing angioplasty-induced vessel damage.

Acetylcysteine↗
PubMed1994

Parenteral magnesium sulphate restores regional contractile function in the post-ischaemic canine myocardium.

The effects of parenteral magnesium sulphate (MS) on the regional contractile response of stunned myocardium was examined in 45 pentobarbital anaesthetized dogs. The hearts were instrumented to measure left ventricular pressure (LVP), coronary flow velocity (CFV), mean arterial blood pressure (MAP), and regional contractile function (percent segment shortening, %S; and end-diastolic segment length, EDL). Stunning was produced by a 10 min occlusion of the first descending branch of the left circumflex coronary artery. Immediately upon release of the occlusion, either magnesium sulphate or a dextrose vehicle (D5W, n = 15) was infused. Magnesium sulphate was given intravenously (IV-MS, 100 mg/kg, n = 15) or intracoronarily (IC-MS, 1.5 mg/kg, n = 15). Coronary occlusion was consistently associated with significant decreases in coronary flow velocity and %S in all groups. Following IV-MS, heart rate (HR) and mean arterial blood pressure decreased significantly from preocclusion values, whereas end-diastolic segment length tended to increase and left ventricular pressure remained constant. IC-MS did not produce any changes in heart rate, mean arterial blood pressure, end- diastolic segment length or left ventricular pressure. At the end of the magnesium sulphate infusion (IV or IC), and for the next 60 min, %S returned to or above pre-occlusion values (P < 0.05 vs. D5W). Dyskinesia and hypokinesia were abolished in the magnesium sulphate groups, but were still present in the D5W group at the end of the 60 min period (P < 0.05 vs. pre-occlusion). We conclude that parenteral magnesium sulphate significantly improves regional contractile function in the stunned myocardium. Data from the IC-MS group would suggest a direct myocardial effect, independent of changes in preload, afterload, heart rate or flow.

Animals↗
PubMed1993

Pressure-flow characteristics of intramural and total coronary collateral networks.

The purpose of the present investigation was to determine the pressure-flow (PF) relationship of intramural collaterals and to determine whether their characteristics differ significantly from those of the total collateral network, defined as the epicardial plus intramural collateral network. Because a significant portion of the collateral flow is diverted away from the retrograde flow measurement, we embolized the coronary vessel on which the retrograde flow was measured with spheres of various sizes until the retrograde flow was maximized and retrograde flow diversion blocked. The PF relationship was obtained before and after the epicardial collaterals were cauterized to determine the characteristics of the total and intramural collateral network. PF data for the collateral circulations were obtained by changing the inflow pressure to all coronary vessels simultaneously and by measuring the retrograde flow while maintaining the retrograde outflow pressure at 0 mmHg. The PF characteristics of the total and intramural collateral circulations could be fitted by either a second-degree polynomial or linear equation. In both cases the pressure intercept crossed the origin of the axes. The average contribution of intramural collaterals to total retrograde flow was 58 +/- 5%. We conclude that the PF characteristics of intramural collaterals parallel those of the total collateral circulation.

Animals↗
PubMed1993

On the use of parenteral magnesium salts in the treatment of acute ischaemic heart disease: a brief review.

With the advent of pharmacological, mechanical and surgical revascularization as firstline therapies in acute coronary artery disease syndromes, the search for adjunctive pharmacotherapy against reocclusion and reperfusion injury has intensified. In addition, safe pharmacotherapeutic intervention conferring survival advantage is required for those at high risk ineligible for recanalization or beta blockade. Of major importance, in this vein, is the intriguing association between parenteral magnesium and the amelioration of myocardial ischaemia and the eradication of lethal ischaemic ventricular arrhythmias reasserted in both animal and human studies. In addition, in more recent years, parenteral magnesium has been linked to the amelioration of reperfusion injury in animal experiments. In this paper we shall review the literature with respect to myocardial ischaemia, its pathophysiology and treatments. In doing so, we shall present data that strongly supports the logistic use of parenteral magnesium compounds as essential therapy in the treatment of acute ischaemic heart disease associated with necrosis, and a potential role in ablating reperfusion injury.

Electrophysiology↗
PubMed1992

Hemodynamics of heartworm infection.

To determine the hemodynamic responsiveness of dogs testing positive for heartworms (direct blood smear), we compared the response of control and heartworm-infected animals to stellate stimulation (SS). Using the anesthetized, open-chest model, twenty dogs (10 control and 10 heartworm-positive) were instrumented to measure left ventricular pressure (LVP), arterial pressure (AP), and coronary flow velocity (CFV) of the left circumflex coronary artery. CFV was converted to flow per gram tissue (CBFG) by weighing the perfusion area of the circumflex artery. The average wet weight of the worm mass infecting the dogs was 1.0 +/- 0.1 g, which represented an average of 5% of the right ventricular free wall weight. Overall heart size and right ventricular weights were greater in the heartworm-positive animals, as well as heart weight to body weight ratios. Prior to SS, LVP was the same for both groups. However, dP/dt and CBFG were 21% and 19% lower, respectively, in the heartworm-positive animals. Stellate stimulation sufficient to produce a 30-mmHg rise in AP led to 25%, 13%, and 40% increases in LVP, dP/dt, and CBFG, respectively, in the control animals. Increases of 22%, 10%, and 52% in the same parameters were observed in the heartworm-positive animals. Although control dP/dt and CBFG in the heartworm-positive animals were lower than in the heartworm-negative animals, heartworm infection at this level did not hinder myocardial responsiveness to SS.

Animals↗
PubMed1989

Pressure-flow characteristics of coronary collaterals in dogs.

In this study we utilized two methods to investigate the pressure-flow, P-F, relationship of the coronary collateral vessels in a beating, blood-perfused, isolated heart preparation. In the first method (free-flow method), 12 dog hearts were perfused at pressures ranging from 100 to 0 mmHg, whereas the retrograde flow (index of collateral flow) was measured on the circumflex coronary artery, LCA, against atmospheric pressure, first during autoregulation and then after maximum vasodilation. In the second method (back-pressure method), the back pressure to retrograde flow was varied from 0 to 100 mmHg, whereas the perfusion pressure to the remaining vessels was maintained constant at 100 mmHg. This procedure was performed on four hearts with and without embolization of the LCA by 25-microns spheres. The free-flow method demonstrated a linear P-F relationship with an average correlation coefficient, r, of 0.98. The pressure intercept was 1.7 +/- 1.2 mmHg. The back-pressure method yielded a relationship that was more curvilinear with an average pressure intercept of 13 mmHg without embolization and 38 mmHg with embolization. An analog of the coronary and collateral circulation was used to illustrate that, in the back-pressure method, changes in the coronary resistance at low pressures contributed to the nonlinearity of the collateral P-F characteristics and that the network formed between the collateral and coronary resistances was responsible for the higher pressure intercept value.

Animals↗
PubMed1989

Collateral influence on pressure-flow characteristics of coronary circulation.

The purpose of this study was to determine the role of the coronary collateral circulation on the shape of the coronary pressure-flow (P-F) relationship and its effects on the pressure at zero flow (PZF) or pressure intercept. We investigated the P-F characteristics of the coronary circulation under two conditions. 1) To minimize the influence of collaterals, we measured coronary flow by timed collections of coronary sinus outflow in 15 dog hearts, as perfusion pressure to all vessels was varied; 2) to maximize the effect of collaterals, we measured circumflex artery flow in six dog hearts, as perfusion pressure to only the circumflex coronary artery was varied and the pressure in the remaining vessels was maintained constant. We used an isolated heart preparation in which ventricular chamber and venous outflow pressures equalled atmospheric pressure and the vessels were maximally dilated with adenosine. In the first condition, the P-F relationship was curvilinear with a PZF of 0 mmHg; in the second condition, the P-F relationship was curvilinear with a PZF of 16 +/- 2 mmHg, and flow was retrograde at pressures below PZF. We conclude that in both conditions the curvilinearity of the coronary P-F relationship was the result of nonlinear elastic properties of blood vessels, not requiring the "waterfall" concept to be invoked, and that in the second condition the influence of collateral vessels produced the positive pressure intercept.

Animals↗
PubMed1987

Myocardial flow and function after regional beta-blockade in exercising dogs.

This study was designed to examine the contribution of beta 1- and beta 2-adrenergic receptors in modulating coronary blood flow and cardiac function in exercising dogs. Dogs were chronically instrumented to measure left circumflex flow velocity (CFV), heart rate, regional left ventricular function [systolic shortening, (%S) and maximum velocity of shortening (dL/dt(s)max)], and global left ventricular function [left ventricular pressure (LVP and dP/dtmax)]. Exercise significantly increased LVP (31 +/- 4%), dP/dtmax (130 +/- 17%), heart rate (116 +/- 20%), %S (28 +/- 6%), dL/dt(s)max (89 +/- 23%), and CFV (91 +/- 25%). Regional injection of the non-selective beta-blocker propranolol (1.0 mg) into the circumflex artery during exercise was associated with decreases in LVP (-8 +/- 3%), dP/dtmax (-17 +/- 3%), %S (-15 +/- 4), dL/dt(s)max (-13 +/- 4%), and CFV (-22 +/- 4%). Selective beta 1-receptor blockade with atenolol (1.0 mg, i.c.) was associated with similar decreases in LVP (-7 +/- 3%), dP/dtmax (-33 +/- 4%), %S (-12 +/- 3%), dL/dt(s)max (-17 +/- 2%), and CFV (-18 +/- 3%) during exercise. In contrast, selective beta 2-receptor blockade with ICI 118551 (250 micrograms, i.c.) produced significant decreases in only CFV (-11 +/- 2%) during exercise. Thus, the data suggest that the reductions in myocardial contractile function and flow after regional beta-blockade are primarily due to a decrease in myocardial beta 1-receptor stimulation. In addition, there apparently is a small involvement of either coronary vascular or pre-synaptic beta 2-receptors in mediating the coronary vascular flow response during exercise.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

When is it appropriate to intervene?

I work in a long-term setting where the residents all have written levels of intervention. Last week I came across a resident who was choking on a piece of food and unable to breathe. Even though I knew he had a DNR order as a component of his written level of intervention, I initiated action to rescue him. In thinking about this afterward, and discussing it with colleagues, we began to question whether I should have done this since it could be said that I was acting against his wishes. What is your opinion on this?

Airway Obstruction↗
PubMedDate not supplied

Primary health care in action.

In a 40-page report on the Comox Valley Nursing Centre Demonstration Project RNABC says the project showed what nurses can do when they are allowed to practice the full scope of their profession. Overall, the project was a success in making a contribution to understanding the principles of primary health care and community-based nursing practice.

Community Health Centers↗