The following is a summary of “Clinical practice and effect of carbon dioxide on outcomes in mechanically ventilated acute brain-injured patients: a secondary analysis of the ENIO study,” published in the January 2024 issue of Critical Care by Robba et al.
Whether controlling blood partial pressure of carbon dioxide (PaCO2) affects outcomes in patients with high brain pressure (ICP) remains uncertain.
Researchers conducted a retrospective study to characterize PaCO2 targets and incidence of abnormal values in acute brain-injured (ABI) patients during their first ICU week, additionally exploring potential links between PaCO2 and in-hospital mortality.
They conducted a secondary analysis of a prospective observational study with adult patients undergoing invasive ventilation for traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), intracranial hemorrhage (ICH), or ischemic stroke (IS). PaCO2 measurements were taken from ICU admission on days 1, 3, and 7. Normocapnia as PaCO2 35–45 mmHg; mild hypocapnia: 32–35 mmHg; severe hypocapnia: 26–31 mmHg; forced hypocapnia: <26 mmHg; hypercapnia: >45 mmHg.
The results showed 1476 patients (65.9% male, mean age 52 ± 18 years). Upon ICU admission, 804 (54.5%) patients exhibited normocapnia (1.37 episodes per person/day during ICU stay), while 125 (8.5%) and 334 (22.6%) displayed mild or severe hypocapnia (0.52 and 0.25 episodes/day). Forced hypocapnia and hypercapnia were administered in 40 (2.7%) and 173 (11.7%) patients. PaCO2 demonstrated a U-shaped correlation with in-hospital mortality, with only severe hypocapnia and hypercapnia associated with an increased probability of in-hospital mortality (omnibus P value = 0.0009). Substantial differences were noted among various subgroups of ABI patients.
Investigators concluded that while normocapnia and mild hypocapnia were prevalent in ABI patients, extreme PaCO2 deviations were linked to significantly higher in-hospital mortality.
Source: link.springer.com/article/10.1007/s00134-023-07305-3
