Veno-arterial CO2 difference and respiratory quotient after cardiac arrest: An observational cohort study

Abstract

Background: Despite significant research and progress, cardiac arrest remains a condition with a high mortality rate, and few interventions have been demonstrated to improve outcomes in this patient group. Despite incorporation of adrenaline use in the treatment guidelines over several decades, its potential benefit remains uncertain. After initial resuscitation, patients are often admitted to the intensive care unit (ICU). Mortality approaches 50% in comatose post-cardiac arrest patients, leaving clinicians to face often difficult decisions concerning prognostication and duration of intensive care efforts in this patient population. Aims:The aims of this thesis were: To study the relationship between adrenaline treatment, return of spontaneous circulation (ROSC), and survival in patients with in-hospital cardiac arrest (paper I). To explore the association between the duration of intensive care and survival following cardiac arrest (Paper II). To characterize levels of blood lactate, veno-arterial carbon dioxide difference (p∆CO2) and the ratio of veno-arterial carbon dioxide content difference to arterio-venous oxygen content difference (RQ) in post cardiac arrest patients and to study whether these parameters are associated with mortality after cardiac arrest (paper III and IV). Methods: Data were collected from the Swedish Registry of Cardiopulmonary Resuscitation (papers I and II) and The Swedish Intensive Care Registry (paper II). In paper I, we compared ROSC and 30-day survival in patients that received, or did not receive, adrenaline during resuscitation. In paper II, hospitals were divided into quartiles (hospital groups 1-4) according to their median duration of mechanical ventilation in patients who did not survive to hospital discharge. The primary outcome was the association between the variable 'hospital group' and 30-day survival. In papers III and IV, we measured and evaluated the prognostic implications of RQ and p∆CO2 in two cohorts vi of post-cardiac arrest patients. In paper III, data were collected retrospectively from an institutional registry at Erasme University, Belgium, and RQ and p∆CO2 were assessed from central venous and arterial blood gases once during the initial 24 h after admission. Outcomes were ICU mortality and unfavourable neurologic outcome at 3 months. Paper IV was a prospective study in patients admitted to Sahlgrenska University Hospital. We measured RQ, p∆CO2, and lactate prospectively during the initial 72 h after admission and explored whether RQ or p∆CO2 can identify patients who experienced either early mortality (at 96 h) or mortality during follow up. Results:The relationship between adrenaline treatment and ROSC was dependent on initial rhythm and duration of cardiopulmonary resuscitation (CPR), with patients presenting a shockable rhythm and treated with adrenaline having a lower frequency of ROSC when stratified by CPR duration. In patients with a non-shockable rhythm, the ROSC rate was higher in adrenaline-treated patients when stratification included CPR durati...

Veno‐arterial CO2 difference and lactate for prediction of early mortality after cardiac arrest

“…In a previous study by our group, an increase in ∆pCO 2 was associated with a lower risk of ICU mortality and poor neurologic outcome 28 . That study differed from the current study as data were measured at a single time point during the initial 24 h at the discretion of the treating physician.…”

“…In a previous study by our group, an increase in ΔpCO 2 was associated with a lower risk of ICU mortality and poor neurologic outcome. 28 That study differed from the current study as data were measured at a single time point during the initial 24 h at the discretion of the treating physician. Furthermore, there was a case-mix with patients on extracorporeal membrane oxygenation which possibly affected the relationship between ΔpCO 2 and mortality due to changes in the circulatory physiology with extracorporeal circulatory support.…”

“…Furthermore, there was a case-mix with patients on extracorporeal membrane oxygenation which possibly affected the relationship between ΔpCO 2 and mortality due to changes in the circulatory physiology with extracorporeal circulatory support. 28 In a study by Riviero et al, there was no association F I G U R E 1 Distribution of ΔpCO 2 (kPa) and lactate (mmol/L) during the initial 24 h after randomization in survivors (blue) and non-survivors (green) at 96 h after admission. In a mixed linear model, the average levels of pΔCO 2 were not significantly different between survivors and non-survivors ( p = .61) but lactate was on average higher in non-survivors during the initial 24 h after randomization ( p < .001).…”

“…That study differed from the current study as data were measured at a single time point during the initial 24 h at the discretion of the treating physician. Furthermore, there was a case‐mix with patients on extracorporeal membrane oxygenation which possibly affected the relationship between ∆pCO 2 and mortality due to changes in the circulatory physiology with extracorporeal circulatory support 28 . In a study by Riviero et al, there was no association between ∆pCO 2 during the initial 72 h and 28‐day mortality in postcardiac arrest patients 27 .…”

“…∆pCO 2 may be a more appropriate marker than lactate to identify patients at risk of mortality in the early postresuscitation phase as it is rapidly normalized after ROSC and therefore may reflect real‐time tissue perfusion in postcardiac arrest patients with greater precision 26 . Data on ∆pCO 2 in postcardiac arrest patients is limited 27,28 …”