Increased physiologic dead space fraction is associated with mortality after comprehensive stage 2 operation

Objective: Our objective was to assess the predictive value of physiologic dead space fraction for mortality in patients undergoing the comprehensive stage 2 operation.

Methods: This was a single-centre retrospective observational study conducted at a quaternary free-standing children's hospital specialising in hybrid palliation of single ventricle cardiac disease. 180 patients underwent the comprehensive stage 2 operation. 76 patients (42%) underwent early extubation, 59 (33%) standard extubation, and 45 (25%) delayed extubation. We measured time to extubation, post-operative outcomes, length of stay and utilised Fine gray models, Youden's J statistic, cumulative incidence function, and logistic regression to analyse outcomes.

Results: Delayed extubation group suffered significantly higher rates of mortality (31.1% vs. 6.8%), cardiac arrest (40.0% vs. 10.2%), stroke (37.8% vs. 11.9%), and need for catheter (28.9% vs. 5.1%) and surgical intervention (24.4% vs. 8.5%) (P < 0.001). Physiologic dead space fraction was significantly higher in the delayed extubation group and in non-survivors with a value of 0.3, which was found to be the discriminatory point by Youden's J statistic. For a 0.1 unit increase in physiologic dead space fraction on post-operative day 1, the odds of a patient expiring increase by a factor of 2.26 (95% CI 1.41-3.97, p < 0.001) and by a factor of 3.79 (95% CI 1.65-11.7, p 0.01) on post-operative day 3.

Conclusions: Delayed extubation impacts morbidity and mortality in patients undergoing the comprehensive stage 2 operation. Increased physiologic dead space fraction in the first 60 hours after arrival to the ICU is associated with higher mortality.