Volume assessment in patients with necrotizing pancreatitis: a comparison of intrathoracic blood volume index, central venous pressure, and hematocrit, and their correlation to cardiac index and extravascular lung water index.

OBJECTIVE: Volume depletion and/or increased hematocrit are associated with poor prognosis in necrotizing pancreatitis. Several studies suggest that intrathoracic blood volume index (ITBI) might be superior to central venous pressure (CVP) with regard to preload assessment. Therefore, the aim of our study was to evaluate the predictive value of CVP and hematocrit with regard to ITBI, and to correlate these parameters to cardiac index (CI).

DESIGN: Prospective study.

SETTING: Medical intensive care unit, university hospital.

PATIENTS AND INTERVENTIONS: Within 24 hrs of intensive care unit-admission, 96 hemodynamic measurements using the PiCCO system were performed in 24 patients with necrotizing pancreatitis.

MAIN RESULTS: Mean CVP (12.11 +/- 5.97 mm Hg; median 11.5 normal: 1-9 mm Hg) was elevated, whereas mean ITBI (822.8 +/- 157.0 mL/m2; median 836 mL/m2; normal: 850-1000 mL/m2) was decreased. Fifty-one of 96 ITBI values were decreased (prevalence of hypovolemia of 53%). No CVP value was decreased. Fifty-three CVP measurements were elevated despite simultaneous ITBI levels indicating a normal or decreased preload. Sensitivity, specificity, positive predictive value, and negative predictive value of CVP with regard to volume depletion (ITBI <850 mL/m2), were 0%, 100%, 0%, and 47%, respectively. An increase in hematocrit (hematocrit >40% [female] or >44% [male]) was found in 11 of 51 measurements with decreased ITBI. Sensitivity, specificity, positive predictive value, and negative predictive value of an increase in hematocrit with regard to volume depletion according to ITBI were 22%, 82%, 58%, and 48%, respectively. ITBI and delta-ITBI significantly correlated to CI and delta-CI (r = .566, p < 0.001; r = .603, p < 0.001), respectively. CVP and delta-CVP did not correlate to CI and delta-CI, respectively. There was a significant correlation between ITBI and extravascular lung water index (r = .392; p < 0.001), but no correlation between CVP and extravascular lung water index (r = .074; p = 0.473).

CONCLUSIONS: Volume depletion according to ITBI was found in more than half the patients. The predictive values of CVP and hematocrit with regard to volume depletion were low. ITBI and its changes significantly correlated to CI and its changes, which was not observed for CVP and delta-CVP. Therefore, ITBI appears to be more appropriate for volume management in necrotizing pancreatitis than CVP or hematocrit.