Article Text

other Versions

Download PDFPDF
Spontaneous Hyperventilation and Brain Tissue Hypoxia in Patients with Severe Brain Injury
  1. Emmanuel Carrera,
  2. John M Schmidt,
  3. Luis Fernandez,
  4. Pedro Kurtz,
  5. Kiwon Lee,
  6. Maxwell Merkow,
  7. Jan Claassen,
  8. E Sander Connolly,
  9. Stephan A Mayer,
  10. Neeraj Badjatia*
  1. 1 Columbia University Medical Center, United States
  1. Correspondence to: , ; nbadjatia{at}neuro.columbia.edu

Abstract

Background: Hyperventilation has been shown to be associated with cerebral vasoconstriction and increased risk of infarction. Our aim was to determine whether spontaneous reduction of end-tidal CO2 (EtCO2) was associated with an increased in brain tissue hypoxia (BTH).

Method: We studied twenty-one consecutive patients (Mean age; 50±16 years; 15 women) undergoing continuous monitoring for brain tissue oxygenation (PbtO2), intracranial pressure (ICP), cerebral perfusion pressure (CPP), and EtCO2; mean values were recorded hourly BTH was defined as brain tissue oxygen tension (PbtO2) <15 mmHg.

Results: Diagnoses included subarachnoid hemorrhage (67%), intracranial hemorrhage (24 %) and traumatic brain injury (10%). Overall, BTH occurred during 22.5% of the study period (490/2179 hourly data). The frequency of BTH increased progressively from 15.7 % in patients with normal EtCO2 (35-44 mmHg) to 33.9% in patients with EtCO2 < 25 mmHg (p<0.001). The mean tidal volume and minute ventilation of 7 ± 2 ml/kg and 9 ± 2 L/min, respectively. Hypocapnia was associated with higher measured-than-set respiratory rates and maximal minute ventilation values, suggestive of spontaneous hyperventilation. Using a generalized estimated equation (GEE) and after adjustment for GCS, ICP, and core temperature, the variables independently associated with BTH events were EtCO2 (OR: 0.94; 95%CI: 0.90-0.97; P<0.001) and CPP (OR: 0.98; 95%CI: 0.97-0.99; P=0.004).

Conclusion: The risk of brain tissue hypoxia in critically brain-injured patients increases when EtCO2 values are reduced. Unintentional spontaneous hyperventilation may be a common and under-recognized cause of brain tissue hypoxia after severe brain injury.

Statistics from Altmetric.com

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Footnotes