Ventilation in patients with intra-abdominal hypertension: what every critical care physician needs to know

Abstract

The incidence of intra-abdominal hypertension (IAH) is high and still underappreciated by critical care physicians throughout the world. One in four to one in three patients will have IAH on admission, while one out of two will develop IAH within the first week of Intensive Care Unit stay. IAH is associated with high morbidity and mortality. Although considerable progress has been made over the past decades, some important questions remain regarding the optimal ventilation management in patients with IAH. An important first step is to measure intra-abdominal pressure (IAP). If IAH (IAP > 12 mmHg) is present, medical therapies should be initiated to reduce IAP as small reductions in intra-abdominal volume can significantly reduce IAP and airway pressures. Protective lung ventilation with low tidal volumes in patients with respiratory failure and IAH is important. Abdominal-thoracic pressure transmission is around 50%. In patients with IAH, higher positive end-expiratory pressure (PEEP) levels are often required to avoid alveolar collapse but the optimal PEEP in these patients is still unknown. During recruitment manoeuvres, higher opening pressures may be required while closely monitoring oxygenation and the haemodynamic response. During lung-protective ventilation, whilst keeping driving pressures within safe limits, higher plateau pressures than normally considered might be acceptable. Monitoring of the respiratory function and adapting the ventilatory settings during anaesthesia and critical care are of great importance. This review will focus on how to deal with the respiratory derangements in critically ill patients with IAH.

Computed tomographic assessment of lung aeration at different positive end-expiratory pressures in a porcine model of intra-abdominal hypertension and lung injury

“…The optimal mechanical ventilation, and more specifically, the optimal level of PEEP in patients with IAH remains unknown (7,(12)(13)(14). Previous experimental results of our group show that high PEEP levels counteract the negative respiratory effects of IAH (8,11,15).…”

“…We examined the effect of PEEP in the presence of IAH and healthy lung to allow comparison with the results obtained in injured lungs. As IAH and PEEP only minimally affect oxygenation in healthy lungs, the role of PEEP is to provide safe protective lung ventilation and not to improve oxygenation (14).…”

“…Whether patients with IAH and healthy lungs may benefit from higher PEEP levels to reduce the risk of atelectotrauma and ventilator-induced lung injury remains unknown (3,14,16).…”

“…Surprisingly, higher PEEP levels increased lung tissue mass in injured but not in healthy lungs. The oleic acid induced increase in E L resulted in higher plateau airway and intra-thoracic pressures for a given tidal volume, which may itself decrease thoracic lymph drainage (30) or increase intra-thoracic blood volume (14). However, whether higher PEEP in patients with IAH and lung injury increases the risk of lung edema remains debatable.…”

A Clinician’s Guide to Management of Intra-abdominal Hypertension and Abdominal Compartment Syndrome in Critically Ill Patients

“…It is important to realize that the presence of IAH/ACS may lead to changes in general ICU management [45]. Respiratory management is affected since studies have shown that higher ventilation pressures (both PEEP and plateau pressures) can be used safely in patients with increased IAP and may be warranted in order to maintain alveolar recruitment [46]. Elevated IAP has profound effects on the cardiovascular system and the microcirculation; it changes normal values for hemodynamic monitoring and can mimic a state of fluid responsiveness [47].…”