The Effects of Targeted Mild Hypercapnia on Right Ventricular Function After Out-of-Hospital Cardiac Arrest: A Substudy of the Targeted Therapeutic Mild Hypercapnia After Resuscitated Cardiac Arrest Trial.

BACKGROUND

Targeting hypercapnia during invasive mechanical ventilation with subsequent respiratory acidosis may impair right ventricular (RV) function and cause RV failure. RV dysfunction is common after cardiac arrest and may be associated with poor outcomes.

RESEARCH QUESTION: Does targeting mild hypercapnia after out-of-hospital cardiac arrest (OHCA) adversely affect RV function, and is RV failure after OHCA associated with increased mortality?

STUDY DESIGN AND

METHODS

In this single-center, preplanned substudy of the Targeted Therapeutic Mild Hypercapnia After Resuscitated Cardiac Arrest (TAME) trial, patients were randomized to mild hypercapnia (Paco2, 50-55 mm Hg) or normocapnia (Paco2, 35-45 mm Hg) for 24 hours. Transthoracic echocardiography was performed shortly after ICU admission, during and after the intervention period. Time-matched right heart catheterization (RHC) was performed when available. RV systolic function was assessed with tricuspid annular plane systolic excursion (TAPSE), S', and fractional area change (FAC), with 2 of 3 measurements less than abnormal thresholds defined as dysfunction. RV failure was defined as RV systolic dysfunction combined with a cardiac index of < 2.0 L/min/m2 and central venous pressure of > 12 mm Hg.

RESULTS

A total of 111 patients were randomized and evaluated with echocardiography. RHC was performed in 84 patients. TAPSE similarly was reduced in both treatment groups at ICU admission. During the intervention, TAPSE, S', and FAC were higher in the hypercapnia group (P < .05). Accordingly, 13 patients (25%) in the hypercapnia group demonstrated RV systolic dysfunction compared with 37 patients (64%) in the normocapnia group (P < .001). RV failure was present in 30 patients: 8 patients in the hypercapnia group and 22 patients in the normocapnia group (P = .011). RV failure was associated with increased 6-month mortality (hazard ratio, 2.89; 95% CI, 1.37-6.10; P = .005).

INTERPRETATION: Among patients resuscitated from OHCA, targeting mild hypercapnia compared with normocapnia was not associated with worsened RV function, but rather with less RV dysfunction and failure. RV failure was associated with increased 6-month mortality.

CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov; No.: NCT03114033; URL: www.

CLINICALTRIALS: gov.