Optimal VAsopressor TitraTION in Patients 65 Years and Older

Background:

When it is severe, hypotension compromises tissue perfusion and organ function, leading to multiple organ failure and death. Commonly in intensive care units (ICUs), excessive vasodilation causes hypotension. In response, clinicians administer vasopressors to induce vasoconstriction and thereby raise blood pressure. However, these medications may reduce blood flow to vital organs, including the heart, and therefore damage them. Titrating vasopressors therefore requires balancing the risks of organ dysfunction arising from vasopressors or hypotension. Current guidelines recommend titrating vasopressors to a mean arterial pressure (MAP) of 65 mmHg. By not specifying an upper limit, guidelines and clinicians put more emphasis on preventing hypotension than on minimizing vasopressor exposure. Permissive hypotension, defined as a MAP target below traditional levels, may reduce vasopressor-induced harm while avoiding organ dysfunction induced by severe hypotension.

Observational data show that the average MAP in Canadian patients on vasopressors is 75 mmHg, 10 mmHg above current guideline recommendations and self-reported practices.The recent CIHR-funded OVATION pilot RCT (n=118) of permissive hypotension met feasibility objectives of demonstrating a separation in mean MAP between arms (9 mmHg, p<0.0001) and enrolling patients efficiently (2.3 patients/site/month). Investigators have also completed an individual patient data meta-analysis with the French SEPSISPAM trial and found that a lower MAP target may be beneficial in patients 65 years old.

Objective:

The overarching goal of this randomized controlled trial (RCT) of permissive hypotension vs. usual blood pressure targets in hypotensive patients ≥65 years old is to determine whether permissive hypotension reduces the risk of harm associated with usual vasopressor therapy. The proposed RCT has specific objectives to ascertain the effect of permissive hypotension vs. usual care on: 1) markers of organ injury (primarily in the heart at day 3, secondarily (on day 3 and day 7) in the brain, liver, intestine, and skeletal muscle); 2) global tissue dysoxia (assessed by plasma lactate); 3) organ function (assessed by Sequential Organ Failure Assessment [SOFA] Score ); 4) resource utilization, 5) pre-specified adverse events, 6) mortality at 90 days and 6 months; 7) cognitive impairment in survivors at 6 months.

Methods:

Eligible patients will be randomized to target MAP 60-65 mmHg vs. usual care. By comparing permissive hypotension to usual care, we improve acceptance from clinicians and reduce the risk that the control group will diverge widely from usual care. Investigators will enroll patients in 7 Canadian ICUs. The deferred consent model will be adopted, successfully used in the pilot trial. Risk of bias will be minimized by allocation concealment, blinding of outcome assessors, complete hospital follow-up and intention-to-treat analysis.

Relevance:

This RCT proposal is embedded in the international OVATION-65 program of research, which includes the ongoing NIHR-funded UK65 Trial which measures 90-day mortality as the primary outcome. The Canadian OVATION-65 RCT is the only trial that measures organ injury biomarkers, providing crucial clinical information regardless of the effect on mortality. Results are expected to be incorporated into guidelines to inform practice worldwide.

Sample size:

The OVATION-65 Trial was designed to be complementary to the 65 Trial conducted in the United Kingdom. The original proposal, which consisted in a larger and simpler trial (n=800 participants, focused on biomarkers of organ injury) was abandoned because funding applications to the Canadian Institutes for Health Research and the Canadian Frailty Network were unsuccessful. The current trial was supported by a combination of multiple more modest operating grants awarded by the Université de Sherbrooke and the Centre de Recherche du CHU de Sherbrooke (see Funding sources). However, each grant required a distinct objective increasing the complexity of the analysis plan and sample size calculation. Certain analyses were incorporated into funding applications for local experiments on a small scale. By combining funds from multiple sources, we are able to enroll up to 200 participants, however we lack resources to measure every outcome on 200 participants. Outcomes that cannot be measured on every participant or as well as those that were planned originally but that remain unfunded are described briefly in the secondary outcomes section and specified as ancillary studies. They will be reported separately.

Attempts to obtain funding for a larger OVATION-65 Trial continued until the end of 2018. Sufficient funding was secured to enroll up to 200 patients, but trial enrollment was terminated on 21 February 2020 after 159 patients were enrolled, on the recommendation of the DSMC following publication of the 65 trial. Six-month follow-up will be complete in August 2020. The statistical analysis plan will be registered and published before analyzing the data.