Abstract 112: Reconstitution with Saline Is More Appropriate than Arithmetic Correction When Examining Stress-Hemoconcentration Effects on Coagulation

Abstract

Introduction: The goal of this study was to examine a new physiologically relevant method of correcting for hemoconcentration effects on stress-induced changes in coagulation parameters (i.e., activated partial thromboplastin time (APTT), prothrombin time (PT%), FVIII:C, and FVII:C). Hypotheses: We hypothesized that 1) Area-under-the-curve (AUC) for uncorrected PT% and FVII:C would be greater than AUC corrected arithmetically or with saline or plasma, 2) AUC for APTT uncorrected or corrected with baseline plasma would be less than AUC when corrected with saline and greater than AUC corrected arithmetically, and 3) AUC for FVIII:C would not differ between correction methods. Methods: Blood was drawn from 40 men during a 20-min baseline, a 6-min math stressor and a 20-min recovery period. Two reconstitution techniques were used to adjust for hemoconcentration during stress and recovery using the person’s own plasma from baseline or physiological saline equal to the amount of plasma lost during each period. Results: For PT%, uncorrected AUC (M = 30.6 ± 18.4) was significantly greater than AUC corrected with saline (M = -33.3 ± 25.5, p = .002) or arithmetically (M = -9.1 ± 20.3, p = .001) but was not significantly different from AUC corrected with plasma (M = 25.5 ± 20.8, p = .72). For FVII:C, uncorrected AUC (M = 21.0 ± 33.1) was significantly greater than AUC corrected arithmetically (M = -31.7 ± 36.1, p = .001), but was not significantly different from AUC corrected with saline (M = -6.4 ± 38.3, p = .17) or plasma (M = 33.8 ± 36.8, p = .47). For APPT, uncorrected AUC (M = -15.2 ± 4.9) was significantly less than AUC corrected with saline (M = -6.3 ± 5.2, p = .001) and greater than AUC corrected arithmetically (M = -26.7 ± 6.8, p = .007), but was not significantly different from AUC corrected with plasma (M = -13.5 ± 5.2, p = .47). For FVIII:C, the omnibus test was non-significant (p = .39), suggesting no differences between groups. Conclusions: Saline reconstitution appears to be a more biologically relevant correction method when examining hemoconcentration effects on clotting time and clotting activity, whereas the plasma reconstitution method and arithmetic correction do not seem appropriate. With the exception of FVIII:C, hemoconcentration appears to account for the changes in the coagulation parameters.