Renal replacement therapy in patients on extracorporeal membrane oxygenation support: Who and how.

Patients undergoing extracorporeal membrane oxygenation (ECMO) support frequently develop renal failure requiring renal replacement therapy (RRT). RRT may be performed via a dialysis catheter based approach or via the ECMO circuit. We describe our experience with both techniques. A total of 68 patients undergoing ECMO support at our institution were retrospectively analyzed. Predictors of renal failure requiring RRT were determined. Patients undergoing RRT via a dialysis catheter were compared with those undergoing RRT via the ECMO circuit. 10 of the 68 patients required RRT support prior to ECMO. Of the remaining 58 patients, 25 (43%) required new RRT support on ECMO. Lower albumin levels and postcardiotomy shock were predictive of new renal failure requiring RRT on ECMO. RRT performed via the ECMO circuit demonstrated similar efficacy as via a dialysis catheter. Outcomes were much worse for patients requiring new RRT on ECMO support, with a doubling of the length of ECMO support and less that one-third the survival rate of patients not requiring RRT on ECMO support. New renal failure requiring RRT occurs in nearly one-half of patients on ECMO support, with poor outcomes. RRT may be performed via the ECMO circuit with similar efficacy as via a dialysis catheter.

The use of high-frequency percussive ventilation after cardiac surgery significantly improves gas exchange without impairment of hemodynamics.

OBJECTIVE: Respiratory failure represents a significant source of morbidity and mortality for surgical patients. High-frequency percussive ventilation (HFPV) is emerging as a potentially effective rescue therapy in patients failing conventional mechanical ventilation (CMV). Use of HFPV is often limited by concerns for potential effects on hemodynamics, which is particularly tenuous in patients immediately after cardiac surgery. In this manuscript we evaluated the effects of HFPV on gas exchange and cardiac hemodynamics in the immediate postoperative period after cardiac surgery, in comparison with CMV. METHODS: Twenty-four consecutive cardiac surgery patients were ventilated in immediate postoperative period with HFPV for two to four hours, then they switched to a CMV using the adaptive support ventilation mode for weaning. Arterial blood gases were performed during the first and second hour on HFPV, and at 45 minutes after initiation of CMV. Respiratory settings and invasive hemodynamic data (mixed venous oxygen saturation, central venous pressure, systemic and pulmonary blood pressure, cardiac output and index) were collected utilizing right heart pulmonary catheter and arterial lines during HFPV and CMV. Primary outcome was improvement in the ratio between partial pressure of oxygen to fraction of inspired oxygen (P/F ratio) and changes in hemodynamics. RESULTS: Analysis of data for 24 patients revealed a significantly better P/F ratio during the first and second hour on HFPV, compared with a P/F ratio on CMV (420.0 ± 158.8, 459.2 ± 138.5, and 260.2 ± 98.5 respectively, p < 0.05), suggesting much better gas exchange on HFPV than on CMV. Hemodynamics were not affected by the mode of the ventilation. CONCLUSIONS: Improvement in gas exchange, reflected in a significantly improved P/F ratio, wasn't accompanied by worsening in hemodynamic parameters. The significant gains in the P/F ratio were lost when patients were switched to conventional ventilation. This data suggest that HFPV provides significantly better gas exchange compared with CMV and can be safely utilized in postoperative cardiac patients without any significant effect on hemodynamics.

Utility of brain natriuretic peptide as a predictor of atrial fibrillation after cardiac operations.

BACKGROUND: Atrial fibrillation (AF) occurs frequently after coronary bypass grafting and valve operations. Brain natriuretic peptide (BNP) has been shown to predict recurrence of AF in congestive heart failure. It is a potential biomarker for preoperative risk stratification for development of AF in at-risk patients. METHODS: A total of 398 consecutive patients were prospectively evaluated for new-onset AF after heart operations. Patients with a history of AF and presence of permanent pacemaker were excluded. BNP levels were measured before and immediately after the operation. RESULTS: AF occurred in 20%. AF was more likely to develop in patients who were older, who underwent valve operations, had a lower ejection fraction, and a larger left atrial size. Preoperative exposure to statins (62% vs 43%, p < 0.01) and angiotensin inhibitors (60% vs 45%, p = 0.02) was more common in patients without AF. BNP values were insignificantly higher preoperatively (361 vs 302 mg/dL, p = 0.3) and postoperatively (312 vs. 229 mg/dL, p = 0.15) in patients with AF. Multivariate logistic analysis showed that older age (odds ratio [OR], 3.1, 95% confidence interval [CI], 1.7 to 5.6), lower ejection fraction (OR, 2.0; 95% CI, 1.2 to 3.3), larger left atrial size (OR, 3.1; 95% CI, 1.9 to 4.9), and nonuse of angiotensin inhibitors (OR, 2.3; 95% CI, 1.1 to 4.8) were independently associated with AF. CONCLUSIONS: This study does not support use of BNP for prediction of AF. Age, low ejection fraction, large left atrial size, and nonuse of angiotensin blocking agents were found to be significant predictors of AF development.

Malignant hyperthermia following systemic rewarming after hypothermic cardiopulmonary bypass.

Malignant hyperthermia (MH) is a rare hypermetabolic disorder of skeletal muscle that can be fatal if not recognized and treated aggressively. We describe a patient with a suspected family history of MH who developed hyperpyrexia, acidosis, and hypermetabolism after cardiac surgery despite a nontriggering anesthetic. No drugs were identified as being causative and we theorize that systemic rewarming was the inciting cause of MH in this MH-susceptible individual via a mechanism similar to heat stroke.