Reported practice of temperature adjustment (α-stat v pH-stat) for arterial blood gases measurement among investigators from two major cardiac arrest trials.

BackgroundTwo major cardiac arrest trials are evaluating different strategies that may potentially mitigate neurological injury after cardiac arrest and are allowing co-enrolment. However, one trial will target hypothermia and the other will target mild hypercapnia, in which the carbon dioxide (CO2) measurement may be influenced by the choice of temperature adjustment during arterial blood gases (ABGs) measurement. The trials have agreed to standardise assessment by the α-stat method.ObjectivesTo describe the Targeted Therapeutic Mild Hypercapnia after Resuscitated Cardiac Arrest (TAME) and Targeted Hypothermia versus Targeted Normothermia after Out-of-hospital Cardiac Arrest (TTM2) site investigators' self-reported practice of ABG analysis and, in particular, their view of whether α-stat or pH-stat assessment of ABGs is considered optimal.MethodsWe performed an online anonymous multichoice survey. Of the 136 site investigators emailed, 70 (51%) responded. Of these, 19 (27%) were participating in the TAME trial only, 22 (31%) were in TTm2 only, and 29 (41%) were participating in both.ResultsThe majority of respondents identified α-stat (41/68, 60%) compared with pH-stat (27/68, 40%) as their usual approach to ABG analysis when targeting 33°C. In addition, the proportion and pattern of concern over hyperventilation was similarly reported as either "not concerned" or "neutral" when using an α-stat (46/69, 66%) or pH-stat (50/68, 73%) ABG analysis approach. Finally, for the purpose of a randomised controlled trial, most respondents either "strongly agreed", "agreed" or "neither agreed nor disagreed" to use the α-stat (59/69, 85%) or the pH-stat (61/70, 87%) approach.ConclusionOur survey findings support the acceptability of the decision to apply the α-stat approach across participating sites for both trials.