Reduced exposure to vasopressors through permissive hypotension to reduce mortality in critically ill people aged 65 and over: the 65 RCT
Authors: Mouncey Paul R , Richards-Belle Alvin , Thomas Karen , Harrison David A , Sadique M Zia , Grieve Richard D , Camsooksai Julie , Darnell Robert , Gordon Anthony C , Henry Doreen , Hudson Nicholas , Mason Alexina J , Saull Michelle , Whitman Chris , Young J Duncan , Lamontagne François , Rowan Kathryn M ,   the 65 trial investigators
Published: March 2021

Background
Vasopressors are administered to critical care patients to avoid hypotension, which is associated with myocardial injury, kidney injury and death. However, they work by causing vasoconstriction, which may reduce blood flow and cause other adverse effects. A mean arterial pressure target typically guides administration. An individual patient data meta-analysis (Lamontagne F, Day AG, Meade MO, Cook DJ, Guyatt GH, Hylands M, et al. Pooled analysis of higher versus lower blood pressure targets for vasopressor therapy septic and vasodilatory shock. Intensive Care Med 2018;44:12–21) suggested that greater exposure, through higher mean arterial pressure targets, may increase risk of death in older patients.

Objective
To estimate the clinical effectiveness and cost-effectiveness of reduced vasopressor exposure through permissive hypotension (i.e. a lower mean arterial pressure target of 60–65 mmHg) in older critically ill patients.

Design
A pragmatic, randomised clinical trial with integrated economic evaluation.

Setting
Sixty-five NHS adult general critical care units.

Participants
Critically ill patients aged ≥ 65 years receiving vasopressors for vasodilatory hypotension.

Interventions
Intervention – permissive hypotension (i.e. a mean arterial pressure target of 60–65 mmHg). Control (usual care) – a mean arterial pressure target at the treating clinician’s discretion.

Main outcome measures
The primary clinical outcome was 90-day all-cause mortality. The primary cost-effectiveness outcome was 90-day incremental net monetary benefit. Secondary outcomes included receipt and duration of advanced respiratory and renal support, mortality at critical care and acute hospital discharge, and questionnaire assessment of cognitive decline and health-related quality of life at 90 days and 1 year.

Results
Of 2600 patients randomised, 2463 (permissive hypotension, n = 1221; usual care, n = 1242) were analysed for the primary clinical outcome. Permissive hypotension resulted in lower exposure to vasopressors than usual care [mean duration 46.0 vs. 55.9 hours, difference –9.9 hours (95% confidence interval –14.3 to –5.5 hours); total noradrenaline-equivalent dose 31.5 mg vs. 44.3 mg, difference –12.8 mg (95% CI –18.0 mg to –17.6 mg)]. By 90 days, 500 (41.0%) patients in the permissive hypotension group and 544 (43.8%) patients in the usual-care group had died (absolute risk difference –2.85%, 95% confidence interval –6.75% to 1.05%; p = 0.154). Adjustment for prespecified baseline variables resulted in an odds ratio for 90-day mortality of 0.82 (95% confidence interval 0.68 to 0.98) favouring permissive hypotension. There were no significant differences in prespecified secondary outcomes or subgroups; however, patients with chronic hypertension showed a mortality difference favourable to permissive hypotension. At 90 days, permissive hypotension showed similar costs to usual care. However, with higher incremental life-years and quality-adjusted life-years in the permissive hypotension group, the incremental net monetary benefit was positive, but with high statistical uncertainty (£378, 95% confidence interval −£1347 to £2103).

Limitations
The intervention was unblinded, with risk of bias minimised through central allocation concealment and a primary outcome not subject to observer bias. The control group event rate was higher than anticipated.

Conclusions
In critically ill patients aged ≥ 65 years receiving vasopressors for vasodilatory hypotension, permissive hypotension did not significantly reduce 90-day mortality compared with usual care. The absolute treatment effect on 90-day mortality, based on 95% confidence intervals, was between a 6.8-percentage reduction and a 1.1-percentage increase in mortality.

Future work
Future work should (1) update the individual patient data meta-analysis, (2) explore approaches for evaluating heterogeneity of treatment effect and (3) explore 65 trial conduct, including use of deferred consent, to inform future trials.

Trial registration
Current Controlled Trials ISRCTN10580502.

Funding
This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 14. See the NIHR Journals Library website for further project information.