Difficult weaning: Principles and practice of a structured diagnostic approach

Difficult weaning from mechanical ventilation is a major problem in critically ill patients. The pathophysiology of weaning failure is complex and multiple causes for difficult weaning may exist in any single patient. We have recently developed a structural framework (‘ABCDE’) for the assessment and treatment of difficult-to-wean patients. In this article, we present the case of a difficult-to-wean 68-year-old male with chronic obstructive pulmonary disease who had been on mechanical ventilation for three weeks. The patient was referred to our centre for assessment of the cause of weaning failure. During a spontaneous breathing trial at our centre an extensive physiological evaluation revealed diastolic dysfunction as the most important cause for weaning failure. It was advised to titrate continuous intravenous nitroglycerin to control systolic blood pressure during subsequent spontaneous breathing trials. In addition, oral antihypertensive drugs were added to control hypertension throughout the day. After treatment in the referring hospital, the patient was successfully weaned from mechanical ventilation within one week. This case report illustrates that a structured approach to weaning failure can unmask hidden pathology and help in the development of a tailored treatment strategy. Introduction In most patients, mechanical ventilation can be discontinued as soon as the underlying reason for acute respiratory failure has resolved. However, approximately one third of patients are considered difficult to wean from mechanical ventilation and six percent of patients still require mechanical ventilation more than seven days after the first weaning attempt.1 The pathophysiology of weaning failure is complex and multiple causes for difficult weaning may exist in any single patient. Determining the primary reason for weaning failure requires an in-depth knowledge of the underlying pathophysiology. For Difficult weaning: Principles and practice of a structured diagnostic approach this purpose, we have recently developed a diagnostic approach for difficult weaning.2 Our ‘weaning ABC’ enables clinicians to systematically review the most likely causes for weaning failure. If we understand the barriers that impede successful weaning in some patients, then tailored treatment strategies can be developed to free patients from mechanical ventilation. The following topics should be included in any evaluation of a difficult-to-wean patient: airway / lung dysfunction, brain dysfunction, cardiac dysfunction, diaphragm / respiratory muscle dysfunction, and endocrine / metabolic dysfunction. In this article we demonstrate how the ABC approach can be used in clinical practice. This case report does not discuss the rationale for each individual diagnostic technique in depth, as this has recently been published elsewhere.2 Case report A 68-year-old male, body weight 105 kg, height 1.84 m, was referred to our centre for evaluation of difficult weaning from mechanical ventilation. The patient’s past medical history revealed chronic obstructive pulmonary disease (COPD) GOLD IV, paroxysmal atrial fibrillation, alcohol abuse and struma. Furthermore, the patient had a 53-pack-year history of smoking. Before hospital admission he lived independently with regard to daily activities, but had some help with housekeeping. The patient was admitted to hospital with an acute exacerbation of COPD due to pneumonia (pH 7.32, PaCO2 8.8 kPa, HCO3 33 mmol/L). The following day the patient was admitted to the intensive care unit (ICU) with progressive respiratory failure (pH 7.29, PaCO2 9.6 kPa) and invasive ventilation was initiated. After three days he was successfully extubated. However, after two weeks, while still in hospital, he was readmitted to the ICU for invasive mechanical ventilation due to progressive respiratory failure. Despite multiple attempts, he could not be weaned from the ventilator during the next three weeks due to “exhaustion”. On referral to our centre, he was able to sustain J. Doorduin1,2, A.J.C. Haans1,2, J.G. van der Hoeven1,2, L.M.A. Heunks1,2 1Department of critical care Medicine and 2Nijmegen expertisecentrum voor Ontwenning van de Beademing (NexcOB), radboud University Nijmegen Medical centre, the Netherlands