Cardiopulmonary arrest acidosis

Vasopressin is a potent vasoconstrictor that increases blood pressure and systemic vascular resistance. It may have several advantages over epinephrine. First, the metabolic acidosis that frequently accompanies cardiopulmonary arrest can blunt the vasoconstrictive effect of epinephrine this does not occur with vasopressin. Second, stimulation of P receptors by epinephrine can increase myocardial oxygen demand and complicate the postresuscitative phase of CPR. Vasopressin can also have a beneficial effect on renal blood flow in the kidney, causing vasodilation and increased water reabsorption. 

Under normal conditions, lactate is metabolized in the liver and the blood lactate level is between 1 and 2 mM. Lactate accumulation in body fluids can be due to increased production and/or decreased utilization. Blood lactate-to-pyruvate ratio below 25 suggests defects in a gluconeogenic enzyme (Chapter 15) or pyruvate dehydrogenase (discussed later). A common cause of lactic acidosis is tissue hypoxia caused by shock, cardiopulmonary arrest, and hypoperfusion. Inadequate blood flow leads to deprivation of oxygen and other nutrients to the tissue cells as well as to the removal of waste products. Oxygen deprivation leads to decreased ATP production and accumulation of NADH, which promotes conversion of pyruvate to lactate. 

Respiratory acidosis with metabolic acidosis Example Cardiopulmonary arrest Severe pulmonary edema Drug ingestion with central nervous system depression... 

In most cases of acute respiratory acidosis, such as following cardiopulmonary arrest, sodium bicarbonate therapy is not indicated and may be detrimental. Blood gas analysis should guide therapy. 

Tay S, Lee IL. Survival after cardiopulmonary arrest with extreme hyperkalaemia and hypothermia in a patient with metformin-associated lactic acidosis. BMJ Case Rep 2012. http //dx.doi.org/10.1136/bcr-2012-007804. 

At one time it was suggested to administer bicarbonate during cardiopulmonary resuscitation following cardiac arrest however, recent evidence suggests that little benefit is provided and its use may be detrimental. For treatment of acidosis in this clinical situation, concentrate efforts on restoring ventilation and blood flow. According to the American Heart Association guidelines, use as a last resort after other standard measures have been utilized. 

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