Disinvestment in Hydroxyl-ethyl Starches (HES) for Cardiac Surgery

Fluid replacement therapy is administered to patients requiring volume resuscitation following significant blood loss, or for maintenance fluid requirements. Severe blood loss can lead to anemia, reduced oxygen carrying capacity, and organ failure. Options for fluid replacement include red blood cell transfusion, colloids such as hydroxyethyl starches (HES), albumin, and gelatin as well as crystalloids such as normal saline and Ringer's lactate. Until recently, use of HES at the London hospitals and other major health sciences centers was concentrated in cardiac surgery patients and non-critically ill perioperative patients. In April 2013, the London Health Sciences Centre (LHSC) opted to discontinue the use of HES altogether, based on evidence suggesting that HES may be harmful compared to alternative fluid therapies.

The decision to disinvest in HES became effective on April 2, 2013. The hospitals no longer purchased HES, and clinicians used alternative fluids for volume resuscitation. Alternatives available at the hospitals included Ringer's lactate, normal saline, and albumin. All HES product was removed from patient care areas.

The investigators will perform a before/after analysis of the impact of HES disinvestment using a retrospective observational cohort study design, employing data obtained from administrative and clinical databases. Exposure to HES before disinvestment will be assumed to be 100% of cardiac surgical patients, and, after a washout period surrounding the time of disinvestment, exposure to HES will be assumed to be 0% after disinvestment.

The study population will be defined retrospectively in terms of the intervention received and the time period of the intervention.

Inclusion criteria

• The London Health Sciences Centre disinvested in hydroxyethyl starches on April 2, 2013. The study population will include individuals undergoing cardiac surgery and discharged from hospital in one of two eras:

• Era 1 (365 days prior to disinvestment in HES): the time period between April 1, 2012 and March 31, 2013, or
• Era 2 (365 days following disinvestment in HES): the time period between June 1, 2013 and May 31, 2014 (NB: after a 2-month washout period to ensure all HES supplies had been exhausted).
• Specifically, the study population will be comprised of patients who underwent the following cardiac surgical procedures:

• Coronary artery bypass graft only
• Coronary artery bypass graft with aortic valve replacement
• Coronary artery bypass graft with aortic valve repair
• Coronary artery bypass graft with mitral valve replacement
• Coronary artery bypass graft with mitral valve repair
• Coronary artery bypass graft with a valve surgical procedure (replacement and/or repair) involving up two valves

Exclusion criteria

• Individuals undergoing heart transplants, aortic dissections, and other cardiac procedures not listed in the inclusion criteria above will be excluded.
• Individuals with any portion of the acute length of stay spanning the washout period (April 1, 2013 to May 31, 2013) will be excluded. Specifically, the following patients will be excluded:

• Patients admitted prior to April 1, 2013 that remained in hospital on April 1, 2013.
• Patients admitted during the washout period (April 1, 2013 to May 31, 2013) that remained in hospital on May 31, 2013.
• Patients admitted and discharged during the washout period.
• We will exclude subsequent cardiac surgical procedures for individuals meeting the inclusion criteria more than once during the study timeframe (i.e. each patient's data will only be used once).
• Individuals enrolled in the randomized controlled clinical trial entitled, "VolulyteTM in Cardiac Surgery" (ClinicalTrials.gov Identifier: NCT01553617) will be excluded from the cohort. The purpose of this study was to assess the efficacy and safety of 6 % Hydroxyethyl Starch 130/0.4 in an Isotonic Electrolyte Solution (VolulyteTM) compared to 5% Human Serum Albumin as volume replacement therapy in elective open-heart surgery in adult patients on cardiopulmonary bypass. Individuals enrolled in the trial were randomized to priming of the cardiopulmonary bypass machine and volume therapy as necessary with either Volulyte or Human Serum Albumin. The study began in October 2012 and was completed in January 2014, with a total enrolment of 133 patients. The approximate number enrolled at LHSC was 30. Because the study period overlaps with that of the pre- and post- disinvestment eras, individuals enrolled in this study will be excluded from the retrospective cohort.