Authors: Alex Dyson Ray Stidwill Val Taylor Mervyn Singer
Publish Date: 2009/07/18
Volume: 35, Issue: 10, Pages: 1783-1791
Abstract
Standard resuscitation practice for shock states mandates use of high flow high concentration oxygen However this may induce microvascular constriction and potentially impair regional oxygen delivery We thus investigated the impact of varying inspired oxygen concentrations in a rat model of progressive haemorrhageTissue oxygen tension the balance between local O2 supply and demand was measured in four different organ beds liver renal cortex muscle bladder with concurrent assessment of cardiorespiratory function and organ perfusion in a spontaneously breathing anaesthetised rat model 10 aliquots of circulating blood volume were removed at 15 min intervals until death Different oxygen fractions in the gas mixture 015–10 were administered following 20 blood removal A control group consisted of normovolaemic animals breathing varying oxygen fractionsSurvival times following progressive haemorrhage were similar in animals breathing room air 98 ± 10 min 60 O2 102 ± 6 min or 100 O2 90 ± 4 min but significantly worse in those breathing 15 O2 52 ± 8 min P 001 Significant derangements of blood pressure aortic blood flow and lactataemia were observed in both hypoxaemic and hyperoxaemic groups compared to normoxaemic animals Breathing 100 O2 increased arterial PO2 sevenfold and tPO2 approximately threefold over baseline values during normovolaemia and mild haemorrhage 20 blood volume removal However with progressive haemorrhage and despite maintained PaO2 values tissue PO2 fell in line with the decrease in global oxygen deliveryThis work was funded by the UK Medical Research Council and Integrative Pharmacological Fund This work was undertaken at UCLH/UCL who receive a proportion of funding from the UK Department of Health’s NIHR Biomedical Research Centre’s funding scheme We thank Oxford Optronix for kindly providing the tPO2 probes
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