British Journal of Anaesthesia, Vol 75, Issue 4 413-416, Copyright © 1995 by The Board of Management and Trustees of the British Journal of Anaesthesia
D. Lomax and S. Valentine
We have performed a randomized prospective study of the effects of inspired
oxygen fraction (FIO2) on the haemodynamic changes after protamine
infusion. Thirty-four patients undergoing first time coronary artery bypass
surgery were allocated randomly to receive either an FIO2 of 1.0 (group O)
or 0.35 (group A) after cardiopulmonary bypass. Before and after infusion
of protamine, haemodynamic measurements were obtained, including mean
arterial pressure (MAP), mean pulmonary artery pressure, central venous
pressure, pulmonary capillary wedge pressure (PCWP), cardiac index (CI),
pulmonary vascular resistance index (PVRI) and systemic vascular resistance
index (SVRI). In group O, there were increases in mean MAP (8%), PVRI (48%)
and SVRI (18%), and decreases in mean CI (10%) and PCWP (15%). Group A
showed changes of 0%, -8%, -6%, +3% and +32%, respectively. We found a
significant difference between groups in changes in PVRI (P < 0.0001),
SVRI (P < 0.01), CI (P < 0.05) and PCWP (P < 0.001). During
infusion of protamine, 31% of patients in group O and 6% of patients in
group A had a decrease in systolic arterial pressure to less than 80 mm Hg
(ns, chi-square test). These observations suggest that FIO2 alters the
haemodynamic effects of protamine.
CLINICAL INVESTIGATIONS
Effect of inspired oxygen on the cardiovascular effects of protamine after cardiopulmonary bypass
Royal Perth Hospital, Wellington St, Perth 6001, Western Australia
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