Clinical Blood Loss Research Articles

The Association between Pulse Pressure and Stroke Volume during Lower Body Negative Pressure and Graded Hemorrhage

Due to the relationship between stroke volume (SV) and pulse pressure (PP) during lower body negative pressure (LBNP), we hypothesized that PP reflects SV during hemorrhage (HEM). After a 5‐minute baseline, 6 men were exposed to LBNP at ‐15, ‐30, and ‐45 mmHg for 5 minutes at each pressure. After 45 minutes of recovery, three progressive 333‐ml stages of HEM (1 L total) were performed. SV was assessed using a CCNexfin and PP was calculated using an arterial catheter. SV (111 ± 2.1 vs. 77 ± 6.7 mL; p= 0.04) and PP (58±2.7 vs. 41 ± 4.3 mm Hg; p = 0.03) decreased from baseline to ‐45 mmHg LBNP. SV (118 ± 4.4 to 99 ± 6.8 mL; p = 0.06) and PP decreased (58 ± 2.9 to 48 ± 4.9 mmHg; p = 0.06) from baseline to ‐1 L of HEM. PP correlated with SV during HEM (amalgamated r2= 0.98) and LBNP (amalgamated r2= 0.99). There was limited inter‐subject variability in PP vs. SV during LBNP (r2 range 0.57 to 0.99, 5/6 had an r2 >; 0.90), but substantial inter‐subject variability during HEM (r2range 0.21 to 0.99, 2/6 had an r2 >; 0.90). Reductions in PP induced by LBNP or HEM are strongly correlated with SV. However large inter‐individual differences in this correlation during HEM, which may indicate a significantly variable compensatory response in human arterial distensibility, may limit the use of PP as a surrogate for SV during clinical blood loss. Funded by U.S. Army MRMC Combat Casualty Care Research Program Grant # W81XWH‐11–1‐0823.

The efficacy of B-type natriuretic peptide for early identification of blood loss in traumatic injury

Background Because B-type natriuretic peptide (BNP) secretion has a direct linear correlation with intravascular volume status, it was assessed as an initial marker for blood loss (BL) in polytrauma patients. Methods Hemodynamically unstable trauma patients between 18 and 45 years had serial BNP levels and hemoglobin (Hgb) levels obtained on admission, at 8 and 24 hours, and every morning during resuscitation. Results The 14 patients were categorized into 2 groups based on the 24-hour trend in Hgb levels: clinically significant blood loss (Hgb decrease >3 g/dL) or no clinical blood loss (Hgb decrease <3 g/dL). On admission, the 5 patients in the no blood loss group had normal BNP levels, whereas the 9 patients in the BL group had below-normal BNP levels. Because patients in the BL category were resuscitated, their BNP levels normalized. Conclusions BNP levels below normal are indicative of intravascular volume loss in traumatically injured patients.