Human Factors Analysis of Goal-Directed Perfusion in Cardiac Surgery

Abstract

The cardiac surgery operating room (OR) is a complex sociotechnical environment requiring the seamless integration of human-human and human-machine teams. Perfusionists in particular play a critical role in ensuring patient stability by operating the cardiopulmonary bypass (CPB) machine. Goal-directed perfusion (GDP) (oxygen delivery [DO2] ≥ 280 mL/min/m2 during CPB in cardiac surgery) is recommended given the positive results of the Goal-Directed Perfusion Trial (GIFT). However, the additional cognitive burden required by the perfusionist, and associated with the heightened vigilance needed to maintain the GDP threshold, is unknown. The objective of this study was to investigate the relationship between DO2 and perfusionists’ perceived cognitive workload in cardiac surgery.Methods: Experienced perfusionists indicated their perceived cognitive workload immediately after cardiac surgery procedures (N=15) using the validated SURG-TLX index dimensions (mental demands, physical demands, temporal demands, task complexity, situational stress, and distractions). A two-tailed Spearman’s correlation was calculated to investigate the relationship between DO2 and SURG-TLX. IRB approval and informed consent from all participants were obtained.Results: Cases analyzed included 13 coronary artery bypass graft and 2 aortic valve replacement procedures. Patients averaged 66.3 years (SD: 8.3 years) with an average 30-day predicted mortality of 1.03% and 30-day predicted morbidity of 9.36%. Average pump time was 113 minutes (range 77 minutes to 170 minutes). Average body surface area was 2.15 m2 (SD: 0.17 m2).Lower DO2 levels (averaged across the duration of total pump time) were significantly associated with higher overall perceived task load (rs(13) = -0.62, p = 0.014), mental demands (rs(13) = -0.73, p = 0.002), and situational stress (rs(13) = -0.62, p = 0.017) (Figure 1). No significant correlations were detected between average DO2 levels and remaining cognitive workload dimensions.Conclusions: This is the first study to evaluate human factors associated with achieving GDP in cardiac surgery. Self-reported measures indicate an elevation in mental demands and situational stress which correspond to lower DO2 values, supporting further investigation into perfusionists’ cognitive state to avoid episodes of cognitive overload and facilitate maintenance of GDP.