Increased Blood Volume Following Resolution of Acute Cardiogenic Pulmonary Oedema: A Retrospective Analysis

Background: Acute cardiogenic pulmonary oedema (APO) occurs due to an increase in pulmonary microvascular pressure and massive transvascular fluid filtration into the lungs, causing respiratory insufficiency. Objective: To determine whether fluid sequestration in the lungs effectively leads to contraction of the circulating blood volume, leading to relative hypovolaemia, and whether resolution of APO and fluid shift to the vascular compartment restores the circulating volume. Methods: A retrospective analysis was conducted in the intensive care unit of a university teaching hospital, April - September 2007. It comprised a cohort of APO patients and a control group of patients with acute exacerbation of chronic obstructive pulmonary disease (COPD) with similar demographics. Patient demographics, haematocrit, haemoglobin levels, total protein and albumin levels, and arterial blood gas were analysed at presentation and after clinical resolution or at 24 hours. Fluid balance charts were reviewed. Blood, plasma and cell volume changes were calculated using haemoglobin levels and haematocrit. Results: 52 patients (27 with APO; 25 with COPD) were included. Median haematocrit decreased significantly and the calculated blood and plasma volumes showed statistically significant increases after treatment in the APO group when compared with the COPD group (P < 0.001). Fluid intake and output were well balanced in both groups. Conclusions: Patients with APO are hypovolaemic at the onset relative to their state after treatment. With treatment and resolution of APO, hypovolaemia is corrected and circulating volume is restored.