The earlier the better: the effect of ICU arrival timing on outcomes in elective cardiac surgery

S. Challa¹, A. M. Wisniewski¹, R. Strobel¹, M. Mazzeffi², J. Kern³, L. Yarboro⁴, K. Yount¹, N. Teman^1
1University of Virginia, Charlottesville, Virginia ²University of Maryland, Baltimore, Maryland ³University of Virginia Health Center, Charlottesville, Virginia ⁴University of Virginia Medical Center, Charlottesville, Virginia

Purpose: Due to staffing changes at scheduled intervals and decreases in essential staff particularly in the evenings, late ICU arrivals may be at higher risk for suboptimal surgical outcomes. Utilizing a regional collaborative, we sought to determine the effect of ICU arrival timing on outcomes in elective isolated coronary artery bypass.

Methods: Using a regional collaborative of hospitals, we identified all adult patients undergoing elective, isolated coronary artery bypass grafting (CABG) from January 2013 until June 2023. Patients with missing predicted risk of mortality (PROM), missing intensive care unit arrival time, or undergoing urgent or emergent cases were excluded from analysis. Late ICU arrival time was defined as arrival between 18:00 and 06:00. Our primary outcome of interest was postoperative morbidity and failure to rescue (FTR) as defined by patients experiencing mortality following the prespecified complications: prolonged ventilation, renal failure, permanent stroke, or reoperation. Continuous variables were analyzed by independent two-sample t-tests with categorical variables analyzed via chi-square testing. Multivariable logistic regression was utilized for risk adjustment to account for baseline operative risk, operative time, intraoperative blood transfusion, and year of surgery.

Results: We identified 11,638 patients that met inclusion criteria of which 972 (8.4%) experienced late ICU arrival. Comorbidities between the groups were similar aside from a higher rate of atrial fibrillation or flutter in the late arrival group (8.3% vs. 6.6%, p=0.03). Late ICU arrival patients had higher mean predicted risk of morbidity or mortality (PROMM) (10.1% ± 7.3% vs. 9.6% ± 6.6%, p=0.048) compared to early ICU arrival patients with longer median cardiopulmonary bypass (CPB) times (96 minutes [78, 119] vs. 93 [73, 116], p< 0.001). Postoperatively, patients arriving to the ICU late experienced more complications including cardiac arrest (1.7% vs. 0.9%, p=0.03), intraoperative or postoperative ECMO (0.6% vs. 0.2%, p=0.01), operative mortality (2.0% vs. 1.1%, p=0.02) and length of stay (6 days [5, 8] vs. 5 days [4, 7], p< 0.001). There was no difference in FTR (1.1% vs. 0.7%, p=0.13) although a significantly higher composite of complications comprising FTR (10.3% vs. 6.7%, p< 0.001) driven by increased prolonged ventilation in the late arrival group (7.7% vs. 4.2%, p< 0.001). Multivariable logistic regression adjusting for perioperative risk demonstrated that late arrival to the ICU was an independent predictor of prolonged ventilation (OR=1.58 [1.21, 2.08], p=0.001).

Conclusion: Following risk adjustment, late ICU arrivals experienced higher rates of prolonged ventilation possibly from hesitation to extubate overnight, although this did not translate to FTR. This suggests a need for system-level changes to address extubation protocols for patients arriving to the ICU in the evening. Additionally, this may also suggest a role in scheduling higher risk cases as first starts.

Identify the source of the funding for this research project: This project was in part funded by NIH/NHLBI T32 training grant (#T32HL007849).