Ventilatory targets following brain injury

Abstract

Purpose of reviewRecent studies have focused on identifying optimal targets and strategies of mechanical ventilation in patients with acute brain injury (ABI). The present review will summarize these findings and provide practical guidance to titrate ventilatory settings at the bedside, with a focus on managing potential brain-lung conflicts.Recent findingsPhysiologic studies have elucidated the impact of low tidal volume ventilation and varying levels of positive end expiratory pressure on intracranial pressure and cerebral perfusion. Epidemiologic studies have reported the association of different thresholds of tidal volume, plateau pressure, driving pressure, mechanical power, and arterial oxygen and carbon dioxide concentrations with mortality and neurologic outcomes in patients with ABI. The data collectively make clear that injurious ventilation in this population is associated with worse outcomes; however, optimal ventilatory targets remain poorly defined.SummaryAlthough direct data to guide mechanical ventilation in brain-injured patients is accumulating, the current evidence base remains limited. Ventilatory considerations in this population should be extrapolated from high-quality evidence in patients without brain injury – keeping in mind relevant effects on intracranial pressure and cerebral perfusion in patients with ABI and individualizing the chosen strategy to manage brain-lung conflicts where necessary.

Modern mechanical ventilation strategies for the acute care surgeon: What you need to know

“…We currently have limited data regarding optimal approaches in this setting, but common principles are reviewed in Figure 4. 45 45 The VENTIBRAIN study (NCT04459884) is a multicenter observational study on the optimal practice of mechanical ventilation and ventilator settings in brain-injured patients and association with patient outcomes. The VENTIBRAIN study was initiated in September 2021 and is scheduled to enroll 3,000 patients, with study completion date estimated in December 2023, and will provide extensive information to hopefully improve mechanical ventilation outcomes in these patients for the future.…”

“…Optimal lung protective mechanical ventilation may be challenging in these patients because of the need to also manage optimal partial pressure of carbon dioxide targets in addition to intracranial pressure and cerebral blood flow targets. We currently have limited data regarding optimal approaches in this setting, but common principles are reviewed in Figure 4 45 …”

“…CBF, cerebral blood flow; CPP, cerebral perfusion pressure; HOB, head of bed; ICP intracranial pressure; JVO, jugular venous outflow; LTVV, low tidal volume ventilation; MAP, mean arterial pressure; PaCO 2 , partial pressure of carbon dioxide; PbtO 2 , partial pressure of brain tissue oxygen. Source: Taran et al 45 …”

American Association for the Surgery of Trauma/American College of Surgeons Committee on Trauma clinical protocol for management of acute respiratory distress syndrome and severe hypoxemia

“…In patients with both ARDS and traumatic brain injury, optimal PaCO 2 targets with LTV ventilation should be adjusted to maintain adequate cerebral perfusion pressure and cerebral oxygen delivery using a personalized approach based on intracranial pressure and multimodal brain and cerebral monitoring. [20][21][22] Optimal and High Versus Low PEEP Current evidence supports that patients with moderate or severe ARDS (PaO 2 /FIO 2 ≤ 200) should receive higher levels of PEEP, based on a meta-analysis of individual patient data from 3 large RCTs of higher vs. lower PEEP. 23,24 Patients with moderate/severe ARDS randomized to higher PEEP had significantly lower mortality (adjusted RR, 0.90; 95% CI, 0.81-1.00) and better oxygenation (higher P/F ratio).…”

“…In trauma patients with ARDS, LTV ventilation will likely result in hypercapnia, and may have potential adverse effects in patients with traumatic brain injury. In patients with both ARDS and traumatic brain injury, optimal PaCO 2 targets with LTV ventilation should be adjusted to maintain adequate cerebral perfusion pressure and cerebral oxygen delivery using a personalized approach based on intracranial pressure and multimodal brain and cerebral monitoring 20–22 …”