Mr. B. has experienced a myocardial infarction (MI), and this has impacted his body’s acid-base balance. At present, Mr. B. is in metabolic acidosis. This is evidenced by a low pH, an HCO3 level which is normal, but on the low side, and a low PCO2 level. The low PCO2 level indicates the body is trying to normalize the metabolic pH disturbance by eliminating the volatile acid, CO2 (Heuther, 2020).
The cause of this acidosis is an overproduction of lactic acid by cells in the body. Cells may overproduce lactic acid because of the poor perfusion and cellular hypoxia caused by the heart being unable to pump blood (and, therefore, oxygen) efficiently throughout the body during cardiac arrest (Chiara et al., 2020). In the absence of oxygen, cells must use fermentation to produce energy, and lactic acid is a by-product of this inefficient process. It is important to recognize this effect on pH when treating a patient after cardiac arrest, since the severity of this imbalance has been correlated with worse outcomes after ICU admission (Jamme et al., 2018). One factor Jamme and colleagues (2018) cited in these outcomes is the risk of multi-organ failure, as tissues are injured by reperfusion once resuscitation is achieved.
Chiara, R., Siwicka-Gieroba Dorota, Andras, S., Battaglini, D., Dąbrowski Wojciech, Schultz, M. J., de, J. E., Chloe, G., Rocco Patricia, R. M., & Pelosi, P. (2020). Pathophysiology and clinical consequences of arterial blood gases and pH after cardiac arrest. Intensive Care Medicine Experimental, 8http://dx.doi.org.wilkes.idm.oclc.org/10.1186/s40635-020-00307-1
Huether, S. E., McCance, K. L., & Brashers, V. L. (2020). Understanding pathophysiology. Elsevier.
Jamme, M., Omar Ben, H. S., Guillemet, L., Dupland, P., Bougouin, W., Charpentier, J., Jean-Paul, M., Pène, F., Dumas, F., Cariou, A., & Geri, G. (2018). Severe metabolic acidosis after out-of-hospital cardiac arrest: Risk factors and association with outcome. Annals of Intensive Care, 8(1), 1-8. http://dx.doi.org.wilkes.idm.oclc.org/10.1186/s13613-018-0409-3