To the Editor:
I read with interest the article by O'Connor et al. . The technique of using CO2 to prevent air embolization from occurring during open heart surgery is not new. The technique had been used in the late 1950s and early 1960s during the infancy of cardiac surgery. This technique is seldom used in today's modern heart surgery because of the very nature of its adverse effect on that patient population. In the early 1960s, I too was part of a team using CO2 to flood the open chest to ward off the possibility of an air embolism. We1 found the same effects-hypercarbia and acidosis-that O'Connor et al. noted in their article. What they did not mention, and most likely did not observe, however, is another more pressing adverse affect. Along with the acidosis, there are changes in electrolyte balance that may lead to intraoperative or postoperative cardiac arrhythmias. Our team noticed that by administering CO2, its uptake from the open chest by the field suction into the pump system caused the electrolyte, potassium, to markedly decrease. The extreme hypercarbia causes H+ ions to enter the red blood cells to leach K+ (potassium) extracellularly, thereby causing a hypokalemic state that may cause cardiac problems in the postoperative period. This leads to ventricular arrhythmias, either transient or delayed, and even death . Pharmacokinetics and pharmacodynamics for drugs in general may be altered by changes in organ perfusion and by acidosis, which may alter ionization, solubility, and protein binding of pharmacologic agents. Patients taking cardiac medications, such as digitalis or diuretics, may be more susceptible to dysrhythmias using the CO2 flooding technique. Even patients not taking the drugs previously mentioned can develop postoperative cardiac arrhythmias with this technique. The best way to detect and prevent these cardiac adversities is to measure electrolytes every 15-20 min during cardiopulmonary bypass, immediately postpump run and treat low potassium levels. These adverse affects lead to the demise of several patients because they developed major rhythm problems. Our cardiac surgeons abandoned this technique because of the affects from the CO2.
(1) Liu CK, Lippmann M, Telfer N, Tran C. Transient and delayed hypokalemia and ventricular arrhythmia in patients undergoing open-heart surgery [abstract]. Clin Res 1966;14:161.
Maurice Lippmann, MD
Department of Anesthesiology; University of California-Los Angeles School of Medicine; Torrance, CA 90509-2910
1. O'Connor BR, Kossman BD, Park KW. Severe hypercarbia during cardiopulmonary bypass: a complication of CO2
flooding of the surgical field. Anesth Analg 1998;86:264-6.
3. Clowes GHA, Hopkins AL, Simeone FA. A comparison of physiological effects of hypercapnia and hypoxia in the production of cardiac arrest. Ann Surg 1955;142:446-60.