Introduction: To maximize the use of intensive care unit (ICU) re­­sources, it is important to estimate the prevalence and risk factors for prolonged ICU unit stay after coronary artery bypass grafting (CABG) surgery.

Material and methods: This retrospective cohort study included all patients who underwent primary isolated CABG at Landspitali between 2001 and 2018. Patient information was collected from hospital charts and death registries. Patients who stayed in the ICU for the conventional one night postoperatively were compared with those who needed longer stays in the ICU. Survival rate was estimated with the Kaplan-Meier method. Predictors for prolonged ICU stay were calculated with logistic regression and the outcome used to create a calculator that estimates the probability of prolonged ICU stay.

Results: Out of 2177 patients, 20% required prolonged ICU stay. Patients with prolonged stay were more frequently female (23% vs 16%, p=0.001), had a higher rate of cardiovascular risk factors and higher EuroSCORE II (4.7 vs. 1.9, p<0.001). They also had a higher rate of impaired renal function before surgery (14% vs. 4%, p<0.001) and emergent surgery (18% vs. 2%, p<0.001). Furthermore, these patients had higher rates of both short-term and long-term complications, and lower long-term survival (85% vs 68% five-year survival rate, p<0.0001). Independent risk factors for prolonged ICU stay were advanced age, female gender, EuroSCORE II, history of heart diseases, impaired renal function and emergent surgery.

Conclusions: Every fifth patient had a prolonged ICU stay after CABG. Several risk factors predicted prolonged ICU stay after CABG, in particular patients' medical condition before surgery, EuroSCORE II and emergent surgery. A better understanding of the risk factors for prolonged ICU stay will hopefully aid in scheduling CABG surgeries at Landspitali.

Table I   Comparison of background factors between study groups. Number of cases (%) is shown except for age, BMI and EuroSCORE II where mean ± standard deviation is shown. Chi-square test was used to compare catergorical variables and t-test to compare continuous variables.

Table II   Comparison of drug use between study groups prior to operation. Number of cases (%) is shown. Chi-square test was used to compare catergorical variables.

Table III   Comparison of short term complications between study groups. Number of cases (%) is shown. Chi-square test was used to compare catergorical variables.

Table IV  Raw and adjusted odds ratio (OR) for length of stay in ICU after surgery.

Figure I   Number of nights in the ICU for patients that stayed in the ICU for two nights or more. The number of patients that stayed in the ICU for less than two nights is not shown (n=1746).

Figure II a   Comparison of survival outcomes between study groups.

Figure II b   Comparison of MACCE-free survival outcomes between study groups.

Figure III   Example of the results from an online calculator that estimates the probablity of prolonged ICU stay after CABG in Landspitali. The calculator can be found with the link: https://notendur.hi.is/mingi/calculator.html.