The Impact of Continuous Haemofiltration with High-Volume Fluid Exhange during Cardiopulmonary Bypass Surgery on the Recovery of Patients with Impaired Renal Function: A Pilot Randomised Trial

BACKGROUND:

There is widespread variability in clinical
practice within cardiac surgery units worldwide on the use of
haemofiltration. The clinical impact and safety of this modality is,
however, unknown.

OBJECTIVES:

The primary pilot trial
objectives were as follows: to assess the feasibility of randomising 60
patients with impaired kidney function undergoing on-pump coronary
artery bypass
graft (CABG) surgery within 6 months; to assess the suitability and
reliability of our chosen outcome measures; to explore issues that may
impact on recruitment into a definitive trial; and to undertake an
exploratory economic evaluation.

DESIGN:

A pilot, single-centre, open-label randomised trial.

SETTING:

Liverpool Heart and Chest Hospital NHS Foundation Trust between November 2010 and March 2012.

PARTICIPANTS:

Men
and women, aged > 18 years of age, undergoing on-pump CABG surgery,
who had pre-operative impaired kidney function indicated by an estimated
glomerular filtration rate (eGFR) of < 60 ml/minute adjusted for 1.73 m(2) of body surface area.

INTERVENTIONS:

Group 1: patients who received haemofiltration during bypass (experimental group). Group 2: patients who did not receive haemofiltration during bypass (control group).

MAIN OUTCOME MEASURES:

(1)
Feasibility outcome measures: barriers to recruitment to a larger trial
were documented as observations made during the recruitment period of
the trial. Reliability of data collection methods was monitored using a
13-point case record form validation check for data entry against the
patient clinical notes and the trial database. (2) The main clinical
outcomes were frequency of intensive care unit (ICU) stay of duration
> 3 days and the length of ICU stay days. (3) Other clinical outcomes
were the need for postoperative haemofiltration in the ICU, mechanical
ventilation time, hospital stay, composite of outcome of unfavourable
perioperative events and eGFR values at 6 weeks’ follow-up. (4)
Secondary health economic feasibility outcomes.

RESULTS:

Recruitment
into the pilot trial was from 21 November 2010 to 30 March 2012.
Thirty-seven eligible patients were consented and successfully
randomised into the trial arms (30%). The main issues impacting on
recruitment were the high volume of off-pump CABG surgery within the
centre; recruitment being restricted to research nurses’ working hours
of the week; issues arising associated with the screening process for
identifying prospective eligible patients based on eGFR values; protocol
deviations/treatment crossovers; and unexpected outbreaks of pandemic
influenza and other infectious conditions. The data collection process
was sufficiently robust, with few errors detected. The length of ICU
stay days was deemed a suitable primary outcome. There was an overall
trend towards reduction in the length of ICU stay for patients who were
given intraoperative haemofiltration, more so for those with diabetes.
The economic evaluation estimated that the incremental costs per person
were £1744 lower for the intraoperative haemofiltration group, while the
incremental benefits per person increased by 0.11.

CONCLUSION:

Given
sufficient resources and broadening of the inclusion criteria, the
recruitment into a larger multicentre trial is feasible and may
demonstrate potential clinical and cost benefits of using intraoperative
haemofiltration in this group of patients. However, owing to the small
sample size in this pilot trial, no firm conclusions can be drawn from
the findings at this stage. The outcomes of this pilot study are very
encouraging and suggest that it is feasible to design a continuous
superiority trial with the length of ICU stay days or time to tracheal
extubation as the primary outcome measure, provided that guidelines for
avoiding bias are implemented. An alternative primary outcome measure
that avoids bias is mortality. The inclusion criteria should also be
widened to include all cardiac surgery patients with impaired renal
function.