Aviation “threat and error model” in congenital cardiovascular surgery: ineffective intra-operative error rescue leads to dangerous error cycles

tion with response to heparin. METHODS: Pediatric patients had a comprehensive coagulation panel performed prior to cardiac surgery (antithrombin, protein C/S, coagulation factors II (FII), FVII, FVIII, FIX, FX, FXI, FXIII, fibrinogen, prothrombin time/international normalized ratio (PT/INR) and activated partial thromboplastin time). Previously published, age-appropriate values obtained from normal children were used as reference values across age groups. We also examined the effect of preoperative oxygen saturation and C-reactive protein on blood levels of coagulation factors. The Hemostatic Management System (Medtronic) was used to measure response to the initial heparin dose. RESULTS: Of the 157 enrolled patients, 8%were 10 years old; 31% had a cyanotic condition and 11% had recent heparin exposure. Patients had lower coagulation circulating level activity than expected for age, ranging from 61% to 92% of age-appropriate values (p<0.001 for all) with the exception of PT/INR (106% of age-normal, p1⁄40.002) and circulating FVIII (114% of age-normal, p<0.001). Abnormalities were mostly consistent across age groups. Lower oxygen saturation was associated with lower coagulation system activity (FIX:2.6(1.4)% per -10% oxygen saturation, p1⁄40.06; FVII:3.3(1.3)%, p1⁄40.01; protein C:-3.4(1.6)%, p1⁄40.04). Increasing C-reactive protein was associated with increased FX (+4.0(1.8)% per pmol/L C-reactive protein, p1⁄40.03) and fibrinogen levels (+1.5(0.7)g/L per pmol/L C-reactive protein, p1⁄40.03). Response to initial heparin dose (prior to bypass) was impaired in patients with lower activity of the coagulation system, particularly antithrombin, factors II, IX, X, XI and fibrinogen reuslting in greater thrombin generation during cardiac surgery. CONCLUSION: Children about to undergo cardiac surgery have multiple abnormalities within their coagulation system that affect response to heparin; this in turn affects heparin management and monitoring during surgery and predisposes to both thrombosis and bleeding. Future research identifying determinants of heparin sensitivity and developing potential corrective strategies are warranted. CIHR