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Results
The original study cohort consisted of 1025 patients who had a total of 1030 separate admissions for cardiac surgical procedures during the study period. Within this cohort, 326 patients met 1 or more of the exclusion criteria. Specifically, 242 underwent surgical ablation for atrial fibrillation, 174 patients had a history of atrial fibrillation, and 74 had undergone prior cardiothoracic surgery. Therefore, the final cohort used in the data analysis consisted of 699 patients: 473 in the sodium nitroprusside group and 226 in the control group.
Baseline demographic and perioperative characteristics of the study population are presented in Table 1. The groups were well balanced overall for the risk of POAF. However, the prevalence of congestive heart failure and use of cardiopulmonary bypass were higher in the sodium nitroprusside group. Conversely, patients in the control group had a higher prevalence of mitral valve disease and use of intraaortic balloon pumps and preoperative inotropic medications. The average cross clamp and perfusion times were also higher in the control group.
A total of 183 patients (26.2%) experienced POAF. Results of both the univariate and multivariate analyses are provided in Table 2. There was no significant difference on either univariate or multivariate analysis found in the odds of POAF with the use of intraoperative sodium nitroprusside. The stepwise regression model found an odds ratio of 0.827 (95% CI 0.565 to 1.210) for the association of POAF with the use of sodium nitroprusside. Univariate predictors significantly associated with POAF included chronic kidney disease stages III, IV, and V; preoperative β-blocker use; combined CABG and valve surgery; ICU readmission; and postoperative pneumonia. Significant independent predictors for POAF from the stepwise regression model included patient age (OR 1.06; 95% CI 1.04 to 1.08), preoperative β-blocker use (OR 2.15; 95% CI 1.37 to 3.38), and readmission to the ICU (OR 6.48; 95% CI 2.99 to 14.02). The incidence of POAF on univariate analysis was significantly higher in patients receiving preoperative β-blockers versus those not receiving preoperative β- blockers. This difference remained significant for patients in the sodium nitroprusside group who did (99/350) compared to those who did not (21/123) receive a preoperative β-blocker (OR 1.92; 95% CI 1.13 to 3.24).
Matching patients based on propensity score resulted in 138 matched patient pairs. The baseline demographic and perioperative characteristics of the propensity score–matched cohort were well balanced (Table 3). The difference in the incidence of POAF between groups was not statistically significant (control, 36 [26.1%] vs nitroprusside, 29 [21.0%]; p = 0.418) and there was no significant difference in the odds of POAF found in the propensity score–matched cohort (unadjusted OR 0.774; 95% CI 0.454 to 1.319).
Results of the secondary outcomes are presented in Table 4. Patients in the sodium nitroprusside group spent a statistically significantly shorter amount of time in the ICU than patients in the control group. However, there was no significant difference found in hospital length of stay between groups. Although in-hospital mortality was lower in the sodium nitroprusside group, the difference did not reach statistical significance. The incidence of TIA, however, was higher in the sodium nitroprusside group, but was also not significant.
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