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Biomedical subjects

N S Faithfull

Publications and source records attributed to N S Faithfull.

12 recordsLinked to original sources
PubMed1992

Resuscitation fluids and oxygen transport in haemorrhagic shock.

This study examined the cardiovascular and oxygen transport/consumption relationships in haemorrhagic shock and resuscitation using Human Albumin and Gelatin solutions in a porcine haemorrhagic shock model. Immature pigs (17-25 kg) were anaesthetised and ventilated with nitrous oxide, oxygen and isoflurane. Aortic pressure monitoring and monitoring of pulmonary pressures and cardiac output via a Swan-Ganz catheter were instituted. A controlled haemorrhage of 40% of blood volume at 1% blood volume per minute was followed 30 minutes later by resuscitation with 60% of blood volume of 4.5% Human Albumin (Immuno) or 4% Modified Fluid Gelatin (Gelofusine). Haemorrhage caused marked decreases in (CI), mean arterial pressure and oxygen delivery (DO2). Oxygen consumption (V02) remained unchanged. Resuscitation with Albumin and Gelatin raised CI to values 60% to 70% above control though only Albumin restored DO2. Deterioration was more rapid in the Gelatin group due to the estimated half a life of 3 hours in this model. Oxygen extraction was 10% higher in the Gelatin group 2 hours after resuscitation. The role of oxygen radicals in haemorrhagic shock is discussed.

Albumins↗
PubMed1992

Myocardial oxygen supply under critical conditions, the effects of hemodilution and fluorocarbons.

This article reviews the factors influencing myocardial oxygen supply and demand. The regulative mechanisms in coronary blood flow, especially in critical conditions, are explained. Myocardial oxygenation in coronary artery disease is discussed with special reference to pharmacological intervention. An extensive evaluation of the effects of hemodilution on both the healthy and diseased heart is presented. Effects of hemodilution with fluorocarbons for the treatment or prevention of myocardial ischemia are shown with the aid of intramyocardial oxygen partial pressure measurements.

Animals↗
PubMed1992

Increased plasma O2 solubility improves O2 uptake of in situ dog muscle working maximally.

A perfluorocarbon emulsion [formulation containing 90% wt/vol perflubron (perfluorooctylbromide); Alliance Pharmaceutical] was used to increase O2 solubility in the plasma compartment during hyperoxic low hemoglobin concentration ([Hb]) perfusion of a maximally working dog muscle in situ. Our hypothesis was that the increased plasma O2 solubility would increase the muscle O2 diffusing capacity (DO2) by augmenting the capillary surface area in contact with high [O2]. Oxygen uptake (VO2) was measured in isolated in situ canine gastrocnemius (n = 4) while working for 6 min at a maximal stimulation rate of 1 Hz (isometric tetanic contractions) on three to four separate occasions for each muscle. On each occasion, the last 4 min of the 6-min work period was split into 2 min of a control treatment (only emulsifying agent mixed into blood) and 2 min of perflubron treatment (6 g/kg body wt), reversing the order for each subsequent work bout. Before contractions, the [Hb] of the dog was decreased to 8-9 g/100 ml and arterial PO2 was increased to 500-600 Torr by having the dog breathe 100% O2 to maximize the effect of the perflubron. Muscle blood flow was held constant between the two experimental conditions. Plasma O2 solubility was almost doubled to 0.005 ml O2 x 100 ml blood-1 x Torr-1 by the addition of the perflubron. Muscle O2 delivery and maximal VO2 were significantly improved (at the same blood flow and [Hb]) by 11 and 12.6%, respectively (P < 0.05), during the perflubron treatment compared with the control. O2 extraction by the muscle remained the same between the two treatments, as did the estimate of DO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Oxygen delivery from fluorocarbon emulsions--aspects of convective and diffusive transport.

Perfluorocarbons (PFCs) deliver oxygen due to their physical characteristics and the convective delivery to tissues; this has been amply demonstrated in numerous animal models and in clinical trials. PFC emulsions have also been used for organ perfusion and augmentation of oxygenation to cell cultures. By reason of their small particle size, PFC emulsions penetrate collateral capillaries of an ischemic microcirculation, both supplying oxygenation and possibly restoring flexibility of acidotically stiffened erythrocytes by reinstituting aerobic metabolism. There is also evidence that PFCs can augment tissue oxygenation by increasing oxygen solubility in the plasma phase of blood; this improves diffusion gradients between plasma and tissues even at relatively low doses of PFC. This hypothesis is supported by the ability of PFCs to increase oxygen tensions in tissues such as blood, brain, liver, kidney, pancreas, skeletal muscle, retina etc. PFCs can also on occasions increase critical oxygen extraction coefficients and should therefore be effective in supporting oxidative metabolism in states of extreme cardio-respiratory insufficiency. This theory represents a new concept in oxygen delivery and may define a new class of therapeutic agents that can improve tissue oxygen supply in various pathological states involving low oxygen delivery and ischemia.

Animals↗
PubMed1991

Development of the coronary vasculature in hypoxic fetal rats treated with a purified perfluorocarbon emulsion.

OBJECTIVE: To quantitatively define the coronary vascular bed in the 21-day-old rat fetus with gestational normoxia and hypoxia; to determine if maternal supplemental oxygen and/or oxygen-carrying perfluorocarbons (PFCs) influence development of coronary vessels; and to compare the results using purified and unpurified PFC treatment. DESIGN: Unilateral uterine artery ligation was introduced on gestational day 17 in pregnant animals. Control fetuses were from unligated uterine horns. Experimental intervention occurred during gestational days 17 to 21, with fetuses recovered on day 21. Developing coronary vessels were analyzed quantitatively via light microscopy. ANIMALS: Pregnant Sprague Dawley rats. INTERVENTIONS: Following ligation, pregnant rats received no further treatment, supplemental oxygen inhalation alone, or daily intravenous purified PFC treatment, with or without supplemental oxygen. MAIN RESULTS: Hypoxia caused an increase in resorptions (P less than 0.001), and decreased fetal body weight (P less than 0.001) and heart weight (P less than 0.05). Although the area occupied by developing coronary vessels (sinusoids) was substantially increased, maturation was unchanged. Oxygen supplementation alone did not appreciably influence fetal resorptions or body weight in ligated horns, but did increase fetal heart weight. Sinusoidal area decreased (P less than 0.01), with no effect on sinusoidal maturity. Purified PFC treatment did not alter maternal weight gain or fetal body weight, and moderately decreased resorptions in ligated horns. Fetal heart weight was augmented with purified perflurochemical, while unpurified perfluorochemical treatment diminished heart weight. Both PFC emulsions substantially decreased sinusoidal area. CONCLUSIONS: Perflurocarbon treatment associated with supplemental oxygen is capable of improving the hypoxic effects on fetal heart and coronary vessel development if the emulsion used is appropriately purified.

Animals↗
PubMed1991

Post-operative headache--a multifactorial analysis.

ASA Grade I and II patients admitted for day-case urological surgery received no premedication or an oral dose of temazepam 10 mg. Anaesthesia was induced with methohexitone and maintained with nitrous oxide, oxygen and halothane or enflurane via a Mapleson A circuit. The incidence of post-operative headache was investigated by an independent observer. Eighty patients were studied (50 male and 30 female) of whom 32 (40%) had post-operative headaches. Post-operative headache was significantly correlated with female sex and frequent 'normal' headache occurrence. The lack of previous surgical experience was a significant risk factor and a loose insignificant association existed with age, the use of halothane and the presence of pre-operative headache. Temazepam premedication had no effect and was associated with significantly more patients complaining of feeling cold.

Acetaminophen↗