Rapid lab 865

The pH and PCO₂ were measured by blood gas analysis (Rapid Lab 865, Bayer Diagnostics, Tarrytown, NY, USA, at 37°C). Actual bicarbonate and base excess values were calculated according to the recommendations of the National Committee for Clinical Laboratory standards. Serum sodium, chloride, albumin and lactate concentrations were measured using central chemical analyzers (Roche Modular P800 Module, Roche Diagnostics, Indianapolis, IN, USA). We calculated the relative plasma volume changes in percentage from (Hb0/Hb90)–((1-Hct90/1-Hct0)), in which Hb is haemoglobin and Hct haematocrit, measured at 0 min and 90 min (Sysmex SE-9000, Sysmex Corporation, Kobe, Japan) [29 (link)]. We calculated, in each patient, the sodium chloride concentration difference as a measure of apparent strong ion difference and the corrected anion gap as a measure of strong ion gap [3 (link),4 (link),28 (link)]. The anion gap (AG) was calculated from sodium minus chloride and bicarbonate concentrations and the corrected AG from AG + (0.25 x (45-[albumin in g/L]))–(lactate in mmol/L) to estimate unmeasured, non-lactic acid, anions. Hence, we integratively used physochemical (according to Stewart) and Henderson-Hasselbalch principles to assess acid base status [2 (link),5 (link)].

The primary outcome was ETCO₂ values, which were determined every 30 s by averaging the ETCO₂ values for the preceding 30 s interval. Aortic and RA pressures were continuously monitored (CS/3 CCM; Datex-Ohmeda, Helsinki, Finland), and the data were transferred to a personal computer using S/5 Collect (Datex-Ohmeda, Helsinki, Finland). Coronary perfusion pressure (CPP) was calculated by subtracting the end-diastolic RA pressure from the simultaneous end-diastolic aortic pressure. Aortic systolic pressure, aortic diastolic pressure, and CPP were sampled at 30 s intervals by averaging pressures from five consecutive compressions. CBF was continuously monitored, and its value was sampled every 30 s. Arterial blood gases (Rapidlab 865; Bayer Health Care, Fernwald, Germany) were measured at the pre-arrest baseline and end of each ventilation type.