A pilot assessment of alpha-stat vs pH-stat arterial blood gas analysis after cardiac arrest

Glenn M. Eastwood, Satoshi Suzuki, Cristina Lluch, Antoine G. Schneider, Rinaldo Bellomo

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Purpose: Resuscitated cardiac arrest (CA) patients typically receive therapeutic hypothermia, but arterial blood gases (ABGs) are often assessed after adjustment to 37°C (alpha-stat) instead of actual body temperature (pH-stat). We sought to compare alpha-stat and pH-stat assessment of Pao2 and Paco2 in such patients. Materials and methods: Using ABG data obtained during the first 24 hours of intensive care unit admission, we determined the impact of measured alpha vs calculated pH-stat on Pao2 and Paco2 on patient classification and outcomes for CA patients. Results: We assessed 1013 ABGs from 120 CA patients with a median age of patients 66 years (interquartile range, 50-76). Median alpha-stat Pao2 changed from 122 (95-156) to 107 (82-143) mm Hg with pH-stat and median Paco2 from 39 (34-46) to 35 (30-41) mm Hg (both P <.001). Using the categories of hyperoxemia, normoxemia, and hypoxemia, pH-stat estimation of Pao2 reclassified approximately 20% of patients. Using the categories of hypercapnia, normocapnia, and hypocapnia, pH stat estimation of Paco2 reclassified approximately 40% of patients. The mortality of patients in different Pao2 and Paco2 categories was similar for pH-stat and alpha-stat. Conclusions: Using the pH-stat method, fewer resuscitated CA patients admitted to intensive care unit were classified as hyperoxemic or hypercapnic compared with alpha-stat. These findings suggest an impact of ABG assessment methodology on Pao2, Paco2, and patient classification but not on associated outcomes.

Original languageEnglish
Pages (from-to)138-144
Number of pages7
JournalJournal of Critical Care
Volume30
Issue number1
DOIs
Publication statusPublished - Feb 1 2015

Fingerprint

Blood Gas Analysis
Heart Arrest
Body Temperature
Gases
Intensive Care Units
Hypocapnia
Induced Hypothermia
Hypercapnia

Keywords

  • Arterial blood gas
  • Cardiac arrest
  • Hyperoxemia
  • Hypocapnia
  • Hypoxemia
  • Intensive care

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine
  • Medicine(all)

Cite this

A pilot assessment of alpha-stat vs pH-stat arterial blood gas analysis after cardiac arrest. / Eastwood, Glenn M.; Suzuki, Satoshi; Lluch, Cristina; Schneider, Antoine G.; Bellomo, Rinaldo.

In: Journal of Critical Care, Vol. 30, No. 1, 01.02.2015, p. 138-144.

Research output: Contribution to journalArticle

Eastwood, Glenn M. ; Suzuki, Satoshi ; Lluch, Cristina ; Schneider, Antoine G. ; Bellomo, Rinaldo. / A pilot assessment of alpha-stat vs pH-stat arterial blood gas analysis after cardiac arrest. In: Journal of Critical Care. 2015 ; Vol. 30, No. 1. pp. 138-144.
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N2 - Purpose: Resuscitated cardiac arrest (CA) patients typically receive therapeutic hypothermia, but arterial blood gases (ABGs) are often assessed after adjustment to 37°C (alpha-stat) instead of actual body temperature (pH-stat). We sought to compare alpha-stat and pH-stat assessment of Pao2 and Paco2 in such patients. Materials and methods: Using ABG data obtained during the first 24 hours of intensive care unit admission, we determined the impact of measured alpha vs calculated pH-stat on Pao2 and Paco2 on patient classification and outcomes for CA patients. Results: We assessed 1013 ABGs from 120 CA patients with a median age of patients 66 years (interquartile range, 50-76). Median alpha-stat Pao2 changed from 122 (95-156) to 107 (82-143) mm Hg with pH-stat and median Paco2 from 39 (34-46) to 35 (30-41) mm Hg (both P <.001). Using the categories of hyperoxemia, normoxemia, and hypoxemia, pH-stat estimation of Pao2 reclassified approximately 20% of patients. Using the categories of hypercapnia, normocapnia, and hypocapnia, pH stat estimation of Paco2 reclassified approximately 40% of patients. The mortality of patients in different Pao2 and Paco2 categories was similar for pH-stat and alpha-stat. Conclusions: Using the pH-stat method, fewer resuscitated CA patients admitted to intensive care unit were classified as hyperoxemic or hypercapnic compared with alpha-stat. These findings suggest an impact of ABG assessment methodology on Pao2, Paco2, and patient classification but not on associated outcomes.

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