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Biomedical subjects

D G Allen

Publications and source records attributed to D G Allen.

At least 163 records · Page 9Linked to original sources
PubMed1988

Evaluation of acepromazine/meperidine/atropine premedication followed by thiopental anesthesia in the cat.

Cardiopulmonary function was assessed in healthy cats premedicated with intramuscular acepromazine, meperidine, atropine combination (premix), followed by induction and maintenance with intravenous thiopental for 30 min. Cardiac output by thermodilution, heart rate, blood pressure and blood gas analysis were evaluated over 120 min. A minor degree of respiratory depression was noted in the cats. Cardiac index (cardiac output/kg) was significantly depressed following thiopental induction and for the entire 120 min studied. Stroke volume was significantly reduced after premix administration and for 90 min posthiopental induction. No significant change in heart rate, systemic vascular resistance or blood pressure was observed. Significant cardiovascular depression was produced by the premedicant, and this persisted following thiopental anesthesia.

Acepromazine↗
PubMed1988

Cardiopulmonary effects of a ketamine/acepromazine combination in hypovolemic cats.

The cardiopulmonary effects of a ketamine/ acepromazine combination was studied in ten cats subjected to a 25% whole blood volume loss. Test parameters included cardiac output, measured via thermodilution, heart rate, respiratory rate, arterial blood pressure (systolic, diastolic and mean) and blood gas analysis. Values for cardiac index, stroke volume and systemic vascular resistance were calculated from these data. Posthemorrhage, cardiac output, cardiac index, stroke volume, heart rate and measurements of arterial blood pressure were significantly decreased (p less than 0.05). Following the induction of ketamine/ acepromazine anesthesia, cardiac output, cardiac index, stroke volume and heart rate showed mild but statistically insignificant declines and were above their respective posthemorrhage values 120 min into ketamine/ acepromazine anesthesia. Measurements of arterial blood pressure showed further declines from their respective posthemorrhage values that were statistically significant (p less than 0.05). Following hemorrhage, respiratory rate increased significantly (p less than 0.05), associated with a fall in arterial CO2 tension. During ketamine/ acepromazine anesthesia, respiratory rate showed a dramatic and significant decline (p less than 0.05) with arterial CO2 tension rising to prehemorrhage values. Systemic vascular resistance, arterial O2 tension and pH remained essentially unchanged throughout the experimental period.

Acepromazine↗
PubMed1988

Cardiopulmonary effects of a halothane/oxygen combination in hypovolemic cats.

The cardiopulmonary effects of a halothane/oxygen combination were studied in eight cats subjected to a 25% whole blood volume loss. Test parameters included cardiac output measured via thermodilution, heart rate, respiratory rate, arterial blood pressure (systolic, diastolic and mean) and blood gas analysis. Values for cardiac index, stroke volume and systemic vascular resistance were calculated from these data. Posthemorrhage cardiac output, cardiac index, stroke volume and measurements of arterial blood pressure were significantly decreased (p less than 0.05). Heart rate remained unchanged. Following induction of halothane anesthesia the above parameters experienced a further significant decline (p less than 0.05) from their immediate preanesthetic (i.e. posthemorrhage) values. Heart rate also significantly decreased (p less than 0.05). Thirty minutes following the cessation of halothane anesthesia these values returned to near-hemorrhage levels, being above their respective preanesthetic values. Systemic vascular resistance initially rose, peaking ten minutes into halothane anesthesia, before gradually falling to prehemorrhage values at the end of halothane anesthesia. Following hemorrhage, respiratory rate demonstrated a transient increase, associated with an arterial CO2 tension fall, before returning to initial values at the preanesthetic time. During halothane anesthesia respiratory rate remained unchanged whereas arterial CO2 tension rose significantly (p less than 0.05) and pH declined slightly from preanesthetic readings. These returned to prehemorrhage values 30 minutes following the cessation of halothane anesthesia.

Anesthesia, Inhalation↗
PubMed1987

Management and outcome of pregnancy complicated by severe pre-eclampsia of early onset.

Fifty-six patients with severe gestational proteinuric hypertension presenting at less than 32 weeks' gestation with a live fetus were studied to determine complications, possible treatment and outcome. Sixteen patients (28%) were delivered within 72 hours of presentation for maternal or fetal reasons. In 10 patients the blood pressure settled and they received no antihypertensive therapy but 33 patients received oral antihypertensive therapy (mainly monohydralazine and oxprenolol) in an attempt to delay delivery. The mean presentation to delivery interval in these patients was 11.4 +/- 9.1 days with a range of 1 day - 7 weeks, but 17 patients (51.5%) were delivered within 1 week of presentation. The final 13 patients in the series developed serious medical or obstetric complications during the attempt to delay delivery. The caesarean section rate was 75%. There was a 24.5% overall perinatal mortality, and 19% of infants were small for gestational age. Nine infants were delivered before 28 weeks' gestation with only 1 survivor. Antihypertensive therapy allowed delivery to be delayed to after 28 weeks in 11 patients with only 1 perinatal death. The fetal survival was 100% in patients presenting after 30 weeks' gestation. The unpredictability of the course of disease leads to difficulty in deciding the most appropriate management.

Adult↗
PubMed1987

Predicting the outcome of labour.

A retrospective study of 50 primigravid patients delivered at Somerset Hospital, Cape Town, is reported. It was found that as the birth weight increases a larger brim area is necessary for successful vaginal delivery. The implications of this in terms of prediction of outcome of labour are discussed.

Adolescent↗
PubMed1987

The social policy statement: a reappraisal.

The social policy statement has been an extremely influential text in recent nursing history. Its potential as a guide in the future, however, depends on whether the view of the world it represents is one that nurses want to support. This article analyzes the concepts of person and society that underlie the definition of nursing. It suggests that at least two noncomplementary models of person and society are operating in the policy statement and discusses implications of those models for a theory of nursing.

Humans↗
PubMed1987

The effects of hypertonicity on tension and intracellular calcium concentration in ferret ventricular muscle.

1. Tension and intracellular calcium concentration ([Ca2+]i) were measured in isolated ferret papillary muscles exposed to hypertonic solutions. [Ca2+]i was measured with aequorin which was microinjected into surface cells of the preparation. Correction was made for the effects of ionic strength on aequorin sensitivity to Ca2+. 2. Application of 100 mM-mannitol increased both developed tension and the intracellular Ca2+ signals on contraction (the Ca2+ transients). 300 mM-mannitol increased the Ca2+ transients further but led to a decrease in developed tension. 3. Mannitol caused a concentration-dependent slowing in the time course of a stimulated contraction but had no effect on that of the Ca2+ transient. 4. As the mannitol concentration was increased, the muscles exhibited increased viscosity which was demonstrated by measuring the tension response to a sudden stretch during diastole. This is probably a consequence of cell shrinkage and may cause the slower time course of the contraction. 5. In the presence of 300 mM-mannitol, oscillations of diastolic [Ca2+]i were detectable in both stimulated and quiescent preparations. However, in stimulated preparations the oscillations in mannitol were smaller than when a Ca2+ transient of similar amplitude was achieved by other means. 6. Immediately after the application or removal of mannitol large spontaneous Ca2+ signals were often observed. These signals were even larger in Na+-free solutions, suggesting that they cannot be attributed to Na+-Ca2+ exchange. 7. The increase in developed tension in 100 mM-mannitol can be accounted for by the increased Ca2+ transients in combination with the inhibitory effects of ionic strength on myofibrillar tension production (Kentish, 1984). The decrease in developed tension at 300 mM-mannitol is dominated by the inhibitory effect of increased ionic strength on maximum Ca2+-activated tension.

Aequorin↗
PubMed1987

Myocardial contractile function during ischemia and hypoxia.

There is good evidence that elevated [Ca2+]i, produced by an influx of Ca2+ in exchange for Na+, is the underlying pathology in reperfusion or reoxygenation damage. Further measurements of [Na+]i and [Ca2+]i during ischemia and reperfusion, coupled with information about metabolic levels, are needed to confirm or refute this hypothesis. Contributions to cell damage by other mechanisms, e.g., oxygen free radicals, certainly cannot yet be excluded.

Adenosine Triphosphate↗
PubMed1987

Effects of saffan on cardiopulmonary function in healthy cats.

The effects of saffan on cardiopulmonary function were evaluated in eight healthy adult cats. Measured values were cardiac output by thermodilution, heart rate by electrocardiogram, arterial blood gases, respiratory rate and systolic, diastolic and mean arterial blood pressures by arterial catheterization. Calculated values included cardiac index, stroke volume and systemic vascular resistance. Statistical analysis employed paired t-tests comparing pre saffan anesthetic induction and post saffan anesthetic parameters over a 120 minute time sequence. Thirty min after saffan induction, significant depression in cardiac output was evident while stroke volume was significantly depressed at 45 and 60 min, systolic blood pressure at 15 min and respiratory rate at 5, 10 and 15 min. No significant changes occurred in cardiac index, heart rate, arterial blood gases, diastolic and mean arterial blood pressure or systemic vascular resistance. It was concluded that saffan causes significant depression of cardiopulmonary function in normal adult cats.

Alfaxalone Alfadolone Mixture↗
PubMed1986

A model of insulin delivery by a controlled release micropump.

A model has been developed to describe the delivery of insulin from a controlled release micropump (CRM). Basal delivery was provided by diffusion due to a concentration difference driving force across the CRM. This was modelled by considering the CRM to be a series of one-dimensional steady-state diffusion resistances. This delivery model was used to size prototypes and identify the piston, foam and the pump outlet as the controlling resistances to basal insulin transport. Augmented delivery by the CRM was achieved by repeated compression of a foam disk by a mild steel piston which was driven by a solenoid (tested voltage range 0-173 V DC; 5 msec "on" time; frequency 20-40 min-1). The increased delivery was attributed to the combination of mixing inside the pump barrel and displacement of barrel contents into the downstream reservoir. This action was approximated by a three-compartment model, which considered the CRM to consist of a well-mixed upstream reservoir and pump barrel (with a downstream reservoir) separated by two resistances: a constant upstream membrane resistance, (KmAm)-1, and a variable downstream mixing rate resistance, (Qd)-1. A least squares fit of the model to experimental data showed Qd to increase with the cube of the force on the piston and linearly with the compression frequency. In agreement with experimental results, the model predicted the upstream membrane to be rate controlling only at augmented pump resistances close to the value (KmAm)-1. These models were used to design an improved prototype (VIII) which is now being evaluated in vivo in pancreatectomized dogs for its efficacy in restoring and sustaining normoglycemia.

Animals↗
PubMed1986

Is force production in the myocardium directly dependent upon the free energy change of ATP hydrolysis?

We believe that the weight of present evidence suggests that acute contractile failure in hypoxic or ischaemic cardiac muscle is accompanied by a fall in A but this fall is not the direct cause of the reduced force production. The main established causes of acute contractile failure are the effects of intracellular pH and of Pi accumulation on the contractile proteins and, at a later stage, failure of calcium release. It is worth stressing the role of Pi accumulation both because the effects of Pi have only been recognised relatively recently and because it has a large depressant effect. Pi accumulation is the best candidate to explain the rapid fall of force which occurs during hypoxia and ischaemia when ATP levels are unchanged and before pH changes are substantial.

Adenosine Triphosphate↗
PubMed1986

Assessment of techniques for preventing glycolysis in cardiac muscle.

Studies of myocardial function during ischaemic or anoxia would be assisted if it were possible to inhibit glycolysis completely and reversibly. Three methods of preventing glycolysis in isolated perfused ferret hearts were studied: (a) the removal of glucose from the perfusate followed by manoeuvres designed to deplete glycogen stores, (b) the use of 2-deoxyglucose, and (c) the use of iodoacetate. The rate of glycolysis before and after applying the three methods was assessed by measuring lactate production during short periods of anoxia. Metabolic changes associated with each method were investigated with phosphorus nuclear magnetic resonance, and other side effects associated with each method were assessed by measuring developed pressure. The results show that removal of glucose followed by glycogen depletion reduced the rate of glycolysis to any chosen extent and that the method was reversible. 2-Deoxyglucose treatment did not lead to complete inhibition of glycolysis, was not reversible, and reduced the concentrations of phosphocreatinine and adenosine triphosphate in the heart. Iodoacetate treatment completely blocked glycolysis, but it was not reversible and subsequent periods of anoxia lead to a rapid fall in adenosine triphosphate owing to the accumulation of phosphorylated glycolytic intermediates.

Animals↗
PubMed1986

Metabolic consequences of increasing intracellular calcium and force production in perfused ferret hearts.

31P nuclear magnetic resonance was used to measure the relative concentrations of phosphorus-containing metabolites in Langendorff-perfused ferret hearts. Intracellular concentrations of inorganic phosphate ([Pi]i), phosphocreatine [( PCr]i), ATP ([ATP]i) and [H+] (pHi) were determined. Exposure of the heart to strophanthidin (10-40 microM) produced an increase in developed pressure over 5-10 min. In the presence of strophanthidin, [ATP]i was unchanged, [PCr]i showed a small fall, [Pi]i showed a small rise and there was a small acidosis. Exposure of the heart to a solution in which all the Na had been replaced by K (0 Na(K) solution) produced an increase of resting pressure which then decayed. During this contracture [PCr]i fell transiently and [Pi]i rose transiently with approximately the same time course as the contracture. However, [ATP]i remained constant throughout. The exposure to the 0 Na(K) solution also produced an intracellular acidosis. The changes in [PCr]i and [Pi]i and the intracellular acidosis were all increased during perfusion with 0 Na(K) if the heart had previously been exposed to strophanthidin. The efflux of lactate from the heart was increased during the exposure to the 0 Na(K) solution. The magnitude of this increase was enhanced by prior exposure to strophanthidin. The increase of intracellular lactate (calculated from this efflux) was sufficient to account for the observed intracellular acidification. An increase of lactate efflux could also be measured when an isolated papillary muscle was exposed to the 0 Na(K) solution. The intracellular acidification produced by Na removal was substantially decreased after prevention of glycolysis either by substrate depletion or by the application of iodoacetate. Elevation of the extracellular calcium concentration ([Ca2+]o) produced a large increase of developed pressure which was accompanied by a small transient increase of [Pi]i, a decrease of [PCr]i and a small intracellular acidosis. There was also an increase of lactate efflux. After exposure to strophanthidin the same increase of [Ca2+]o decreased developed pressure. The associated rise in [Pi]i and fall in [PCr]i were increased but there was no significant acidosis under these conditions. In addition to other explanations (Allen, Eisner, Pirolo & Smith, 1985a), it is likely that the fall of force is partly accounted for by the rise of [Pi]i.

Adenosine Triphosphate↗
PubMed1986

Nursing and men's health. Some critical considerations.

This article addresses issues concerning the relationships among nursing, a nascent "men's health" movement, and the established "women's health" movement. Suggestions are made in regard to the potential positive contributions of a men's health movement that recognizes masculinity as a social reality while aiding men with health problems from a holistic nursing perspective.

Adolescent↗
PubMed1986

Shared governance: a strategy for transforming organizations. Part 1.

In translating this to nursing, shared governance systems can be used to effectively implement transformational philosophies. The process is not easy; it does, however, offer new hope for realizing the maximum potential of nursing services within organizations and for effectively meeting the challenges presented by the complex changes occurring in our world. Part 2 of this series will address specific strategies for operationalizing transforming principles in a nursing organization.

Authoritarianism↗
PubMed1986

Shared governance: a strategy for transforming organizations. Part 2.

Nursing leaders know change is not easy: it produces varying degrees of chaos and ambiguity. Maintaining control and traditional structure to minimize either chaos or ambiguity, however, does not achieve the final goal: organizational transformation and effective responses to changes in the environment and the organization. Given our current environment and its demands, we must remember that superficial changes will not address the fundamental problems. Transforming philosophies are relevant and needed in organizations. Transformation requires a shift in our perspectives, our attitudes, and our beliefs. Shared governance is one strategy for assisting in transforming nursing organizations. By sharing power and control with staff, leaders can effectively help to empower the whole and provide leadership that is visionary and creative. The end result of this transformation is meaningful collaboration and a humane, quality nursing system responsive to client needs.

Administrative Personnel↗
PubMed1986

Evaluation of a xylazine-ketamine hydrochloride combination in the cat.

Cardiopulmonary function was assessed in healthy cats given a xylazine-ketamine hydrochloride combination intramuscularly. Cardiac output, heart rate, stroke volume and cardiac index were significantly decreased. Systolic, diastolic and mean arterial blood pressure were also significantly decreased. Systemic vascular resistance and central venous pressure were significantly increased. Blood gas values remained stable. In conclusion, significant cardiovascular depression was noted in normal cats given the xylazine-ketamine combination at the dosages listed.

Animals↗