Hemodynamic evaluation by serial right heart catheterizations after cardiac arrest; protocol of a sub-study from the Blood Pressure and Oxygenation Targets after Out-of-Hospital Cardiac Arrest-trial (BOX)

Impact of Blood Pressure Targets in Patients With Heart Failure Undergoing Postresuscitation Care: A Subgroup Analysis From a Randomized Controlled Trial

BACKGROUND

To assess the effect of targeting higher or lower blood pressure during postresucitation intensive care among comatose patients with out-of-hospital cardiac arrest with a history of heart failure.

METHODS

The BOX trial (Blood Pressure and Oxygenation Targets After Out-of-Hospital Cardiac Arrest) was a randomized, controlled, double-blinded, multicenter study comparing titration of vasopressors toward a mean arterial pressure (MAP) of 63 versus 77 mm Hg during postresuscitation intensive care. Patients with a history of heart failure were included in this substudy. Pulmonary artery catheters were inserted shortly after admission. History of heart failure was assessed through chart review of all included patients. The primary outcome was cardiac index during the first 72 hours. Secondary outcomes were left ventricular ejection fraction, heart rate, stroke volume, renal replacement therapy and all-cause mortality at 365 days.

RESULTS

A total of 134 patients (17% of the BOX cohort) had a history of heart failure (patients with left ventricular ejection fraction, ≤40%: 103 [77%]) of which 71 (53%) were allocated to a MAP of 77 mm Hg. Cardiac index at intensive care unit arrival was 1.77±0.11 L/min·m-2 in the MAP63-group and 1.78±0.17 L/min·m-2 in the MAP77, P=0.92. During the next 72 hours, the mean difference was 0.15 (95% CI, -0.04 to 0.35) L/min·m-2; Pgroup=0.22. Left ventricular ejection fraction and stroke volume was similar between the groups. Patients allocated to MAP77 had significantly elevated heart rate (mean difference 6 [1-12] beats/min, Pgroup=0.03). Vasopressor usage was also significantly increased (P=0.006). At 365 days, 69 (51%) of the patients had died. The adjusted hazard ratio for 365 day mortality was 1.38 (0.84-2.27), P=0.20 and adjusted odds ratio for renal replacement therapy was 2.73 (0.84-8.89; P=0.09).

CONCLUSIONS

In resuscitated patients with out-of-hospital cardiac arrest with a history of heart failure, allocation to a higher blood pressure target resulted in significantly increased heart rate in the higher blood pressure-target group. However, no certain differences was found for cardiac index, left ventricular ejection fraction or stroke volume.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03141099.

Management of Patients After Cardiac Arrest

Cardiac arrest remains a significant cause of morbidity and mortality, although contemporary care now enables potential survival with good neurologic outcome. The core acute management goals for survivors of cardiac arrest are to provide organ support, sustain adequate hemodynamics, and evaluate the underlying cause of the cardiac arrest. In this article, the authors review the current state of knowledge and clinical intensive care unit practice recommendations for patients after cardiac arrest, particularly focusing on important areas of uncertainty, such as targeted temperature management, neuroprognostication, coronary evaluation, and hemodynamic targets.

Impact of blood pressure targets on central hemodynamics during intensive care after out-of-hospital cardiac arrest

OBJECTIVES

The aim was to investigate the advanced hemodynamic effects of the two MAP-targets during intensive care on systemic hemodynamics in comatose patients after cardiac arrest.

DESIGN

Secondary analysis of a randomized controlled trial.

SETTING

Primary vasopressor used was per protocol norepinephrine. Hemodynamic monitoring was done with pulmonary artery catheters (PAC) and measurements were made on predefined time points. The primary endpoint of this substudy was the difference in cardiac index within 48 h from a repeated measurements-mixed model. Secondary endpoints included systemic vascular resistance index (SVRI), heart rate, and stroke volume index.

PATIENTS

Comatose survivors after out-of-hospital cardiac arrest.

INTERVENTIONS

The "Blood pressure and oxygenations targets after out-of-hospital cardiac arrest (BOX)"-trial was a randomized, controlled, double-blinded, multicenter-study comparing targeted mean arterial pressure (MAP) of 63 mmHg (MAP63) vs 77 mmHg (MAP77).

MEASUREMENTS AND MAIN RESULTS

Among 789 randomized patients, 730 (93%) patients were included in the hemodynamic substudy. From PAC-insertion (median 1 hours after ICU-admission) and the next 48 hours, the MAP77-group received significantly higher doses of norepinephrine (mean difference 0.09 µg/kg/min, 95% confidence interval (CI) 0.07-0.11, pgroup < 0.0001). Cardiac index was significantly increased (0.20 L/min/m2 (CI 0.12-0.28), pgroup < 0.0001) as was SVRI with an overall difference of (43 dynes m2/s/cm5 (CI 7-79); pgroup = 0.02). Heart rate was increased in the MAP77-group (4 beats/minute; CI 2-6, pgroup < 0.003), but stroke volume index was not (pgroup = 0.10).

CONCLUSIONS

Targeted MAP at 77 mmHg compared to 63 mmHg resulted in a higher dose of norepinephrine, increased cardiac index and SVRI. Heart rate was also increased, but stroke volume index was not affected by a higher blood pressure target.

Serial assessments of cardiac output and mixed venous oxygen saturation in comatose patients after out-of-hospital cardiac arrest

AIM

To assess the association with outcomes of cardiac index (CI) and mixed venous oxygen saturation (SvO2) in comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA).

METHODS

In the cohort study of 789 patients included in the "BOX"-trial, 565 (77%) patients were included in this hemodynamic substudy (age 62 ± 13 years, male sex 81%). Pulmonary artery catheters were inserted shortly after ICU admission. CI and SvO2 were measured as soon as possible in the ICU and until awakening or death. The endpoints were all-cause mortality at 1 year and renal failure defined as need for renal replacement therapy.

RESULTS

First measured CI was median 1.7 (1.4-2.1) l/min/m2, and first measured SvO2 was median 67 (61-73) %. CI < median with SvO2 > median was present in 222 (39%), and low SvO2 with CI < median was present in 59 (11%). Spline analysis indicated that SvO2 value < 55% was associated with poor outcome. Low CI at admission was not significantly associated with mortality in multivariable analysis (p = 0.14). SvO2 was significantly inversely associated with mortality (hazard ratioadjusted: 0.91 (0.84-0.98) per 5% increase in SvO2, p = 0.01). SvO2 was significantly inversely associated with renal failure after adjusting for confounders (ORadjusted: 0.73 [0.62-0.86] per 5% increase in SvO2, p = 0.001). The combination of lower CI and lower SvO2 was associated with higher risk of mortality (hazard ratioadjusted: 1.54 (1.06-2.23) and renal failure (ORadjusted: 5.87 [2.34-14.73].

CONCLUSION

First measured SvO2 after resuscitation from OHCA was inversely associated with mortality and renal failure. If SvO2 and CI were below median, the risk of poor outcomes increased significantly.

REGISTRATION

The BOX-trial is registered at clinicaltrials.gov (NCT03141099, date 2017-30-04, retrospectively registered).