Transient dilutional acidosis but no lactic acidosis upon cardiopulmonary bypass in patients undergoing coronary artery bypass grafting

Abstract

IntroductionDilutional acidosis may result from the introduction of a large fluid volume into the patients’ systemic circulation, resulting in a considerable dilution of endogenous bicarbonate in the presence of a constant carbon dioxide partial pressure. Its significance or even existence, however, has been strongly questioned. Blood gas samples of patients operated on with standard cardiopulmonary bypass (CPB) were analyzed in order to provide further evidence for the existence of dilutional acidosis.Material and methodsBetween 07/2014 and 10/2014, a total of 25 consecutive patients scheduled for elective isolated coronary artery bypass grafting with CPB were enrolled in this prospective observational study. Blood gas samples taken regularly after CPB initiation were analyzed for dilutional effects and acid-base changes.ResultsAfter CPB initiation, hemoglobin concentration dropped from an average initial value of 12.8 g/dl to 8.8 g/dl. Before the beginning of CPB, the mean value of the patients’ pH and base excess (BE) value averaged 7.41 and 0.5 mEq/l, respectively. After the onset of CPB, pH and BE values significantly dropped to a mean value of 7.33 (p < 0.0001) and –3.3 mEq/l (p < 0.0001), respectively, within the first 20 min. In the following period during CPB they recovered to 7.38 and –0.5 mEq/l, respectively, on average. Patients did not show overt lactic acidosis.ConclusionsThe present data underline the general existence of dilutional acidosis, albeit very limited in its duration. In patients undergoing coronary artery bypass grafting it seems to be the only obvious disturbance in acid-base homeostasis during CPB.

Histidine and other amino acids in blood and urine after administration of Bretschneider solution (HTK) for cardioplegic arrest in patients: effects on N-metabolism

“…The excretion of a surplus of 3 mmol urea (see above) should result in an additional base deficit of only −1 mEq/L. Thus, in relation to acute metabolic acidosis originating from massive dilution of endogenous bicarbonate based on administration of both the priming and the cardioplegic solution (Teloh et al 2015 ), the impact of nitrogen metabolism on acid base status in the intraoperative phase is minor. Due to persistent metabolism in the postoperative phase, however, the acidifying effect caused by enhanced urea excretion might get more pronounced over the course of time.…”

“…After weaning from the heart–lung machine, patients received 56 mL Inzolen (Dr. Franz Koehler Chemie, Bensheim, Germany) on average. For further details see (Teloh et al 2015 ).…”

Postoperative Compensatory Ammonium Excretion Subsequent to Systemic Acidosis in Cardiac Patients

“…As described previously, a total of 25 patients supposed to have CABG surgery were enrolled in a prospective nonrandomized observational study at the Department of Thoracic and Cardiovascular Surgery affiliated to the University Hospital Essen from July 2014 until October 2014 [4]. The study has been approved according to the guidelines of the Declaration of Helsinki by the Medical Ethics Committee of the University Hospital Essen.…”

“…During the operation as well as in the postoperative phase, patients received different fluids intravenously (Table 1), according to those values published previously [4, 16]. …”

“…In conventional on-pump CABG surgery procedures using crystalloid cardioplegic solution, dilutional acidosis is frequently found after administration of the cardiopulmonary bypass (CPB) priming volume and cardioplegia [1–4]. Lactic acidosis might also develop during the operative and postoperative course depending on different parameters like CPB and cross-clamp duration and postoperative hemodynamic status [1, 5, 6].…”