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Gas exchange as monitored in mixed venous and arterial blood during experimental cardiopulmonary resuscitation
Author(s) -
Wiklund L.,
Jorfeldt L.,
Stjernström H.,
Rubertsson S.
Publication year - 1992
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1992.tb03492.x
Subject(s) - medicine , anesthesia , resuscitation , sodium bicarbonate , perfusion , ventilation (architecture) , bicarbonate , cardiopulmonary resuscitation , cardiology , chemistry , mechanical engineering , engineering
Nineteen anaesthetized piglets were investigated. After catheterization and a stabilization period, ventricular fibrillation was induced with a transthoracic DC shock, after which a 10‐min period of cardiopulmonary resuscitation (CPR) took place. CPR included manual chest compression and mechanical ventilation with pure oxygen. After 1 min of CPR, an infusion of alkaline buffer was begun and completed within 5 min. A total of 50 mmol of either sodium bicarbonate (n = 6) or tris buffer mixture (n = 7) were given. These two groups were compared with a third control group (n = 6) receiving the same volume of normal saline. After 8 min of CPR all animals were given 0.5 mg adrenaline i.v., and after 10 min DC shocks were used to revert the heart back to normal sinus rhythm. Our results demonstrate that blood flow and not ventilation is the limiting factor for the efficient disposal of CO 2 during CPR. This also applied when the demand for CO 2 transport was increased by administration of sodium bicarbonate. The respiratory exchange ratio increased 1.9‐fold, indicating that the transport of carbon dioxide was less affected than that of oxygen. The estimated alveolo‐arterial oxygen tension difference, shunt, and overall ventilation/perfusion ratio increased, creating an inverse hyperbolic relationship between arterial Pco 2 and Po 2 . The difference between mixed venous and arterial Pco 2 correlated well to the mixed venous Pco 2 , implying more efficient pulmonary elimination of Pco 2 when the mixed venous Pco 2 was high. Pulmonary gas exchange during CPR appears to be independent of alkaline buffer therapy in the form of sodium bicarbonate or tris buffer mixture. We conclude that experimental closed chest CPR seems to be accompanied by a change in the V'A/Q' relationship in the lungs with simultaneously increased dead space and shunt.