Liberation from invasive mechanical ventilation has a huge impact on quality of life and healthcare expenses. Weaning is more difficult and complex in patients who have been ventilated for a longer time (i.e. more than seven days) or have undergone multiple failed weaning attempts and thus are classified weaning category three according to Boles at al. [1] Current national and international guidelines are in favour of a rather restrictive transfusion regime. This recommendation is mainly based on the work of Hebert et al. [2] where no benefit or a liberal transfusion approach could be found. Patients in the Hebert study however had become acutely ill and did not show any impairment or dysfunction of the respiratory muscles~Weaning class 3 patients however suffer from an overload of their respiratory muscles either cause by an increased load or decreased capacity.~In either instance unloading of the respiratory muscles is key to improve the capability of spontaneous breathing. One possible way to achieve this goal is to improve oxygen delivery.~Oxygen delivery is determined by the cardiac output times the oxygen content of the blood. The latter is mainly determined by the haemoglobin concentration and the oxygen saturation (Hb x 1.34 x SaO2 + PO2 x 0.003). Previous studies have shown that in patients with a strained respiratory pump blood transfusions improve the work of breathing [3].~A more liberal transfusion strategy therefore might improve the weaning outcome ventilator dependant patients [4]~This study is designed as a prospective, randomized, open labeled blinded End-point evaluation to test the hypothesis that a liberal transfusion strategy decreases the time needed for weaning.~Patients who are anemic (Hb < 9 mg/dl) and were admitted to our specialized weaning unit are either randomized to a conservative or liberal transfusion regime if they are agreed to participate.~The goal in the liberal transfusion group is to keep the Hb at > 12 mg/dl and transfusions are given in single units until this threshold is achieved.~Patients then undergo routine weaning procedures consistent of daily or multiple daily weaning trials paired with intermittent ventilation targeted do rest the respiratory muscles.~Daily physiologic data are recorded as well as adverse events. Primary outcome is the time needed to wean the patients off invasive mechanical ventilation, mortality is a secondary criterium.~The study is planned to include 120 patients in blocks of 40 patients. Interim analysis will be performed after each block and the study will be terminated if a significant result is achieved.~Boles, JM, J Bion, A Connors, M Herridge, B Marsh, C Melot, R Pearl, H Silverman, M Stanchina, A Vieillard-BaronandT Welte, Weaning from mechanical ventilation. Eur Respir J, 2007. 29(5): p. 1033.~Hebert, PC, G Wells, MA Blajchman, J Marshall, C Martin, G Pagliarello, M Tweeddale, I SchweitzerandE Yetisir, A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group. N Engl J Med, 1999. 340(6): p. 409.~Schonhofer, B, M Wenzel, M GeibelandD Kohler, Blood transfusion and lung function in chronically anemic patients with severe chronic obstructive pulmonary disease. Crit Care Med, 1998. 26(11): p. 1824.~Sato, T, EJ BedrickandC Tsai, Model Selection for Multivariate Regression in Small Samples. Biometrics, 1998. 54(1): p. 391.
The aim of this study is to determine, whether a liberal transfusion strategy is helpful to liberate patients from prolonged invasive mechanical ventilation.~Patients who are difficult to wean according to the criteria by Boles et al [1] are limited by the capacity of their respiratory muscles.~Improved oxygen delivery achieved by blood transfusions however is known to decrease the work of breathing [2] and thus in theory can improve weaning success [3].~This study is designed as a prospective, randomized, open labeled blinded End-point evaluation to test the hypothesis that a liberal transfusion strategy decreases the time needed for weaning.~Boles, JM, J Bion, A Connors, M Herridge, B Marsh, C Melot, R Pearl, H Silverman, M Stanchina, A Vieillard-BaronandT Welte, Weaning from mechanical ventilation. Eur Respir J, 2007. 29(5): p. 1033.~Schonhofer, B, M Wenzel, M GeibelandD Kohler, Blood transfusion and lung function in chronically anemic patients with severe chronic obstructive pulmonary disease. Crit Care Med, 1998. 26(11): p. 1824.~Schonhofer, B, H BohrerandD Kohler, Blood transfusion facilitating difficult weaning from the ventilator. Anaesthesia, 1998. 53(2): p. 181.