Albumin Administration and Outcomes in Cardiac Surgery
Condition: Thoracic Surgery
Study type: Observational

Summary: 
      The invesitgators utilized the Cerner HealthFacts database (a large HIPAA-compliant
      clinical-administrative database maintained by Cerner Inc., USA) to identify a cohort of
      6,249 adults that underwent on-pump cardiac surgery for valve and/or coronary artery
      procedures between January 2001 and March 2013. Of these, the investigators selected 1136
      patients who received 5% albumin on the day of or the day following cardiac surgery and
      matched them (1:1) with 1136 patients who did not receive albumin. Characteristics on which
      patients were matched included patient demographic, hospital and procedural characteristics,
      baseline patient comorbidities including preoperative CKD and 26 other grouped conditions, as
      well as acute severity of illness at admission to ICU.
    

Detailed description: 
      Following development of the study plan and project summary, approval was obtained (November
      25th 2013) from the Duke University Medical Center institutional review board, who reviewed
      the study outline, including endpoints and treatment exposure groups prior to data
      extraction. HIPAA-compliant data were then extracted from the U.S. Cerner HealthFacts®,
      (Cerner Corp., Kansas City, MO) database. Patients who underwent cardiac surgery utilizing
      CPB between Jan 2001 and March 2013 were identified. In addition to hospital characteristics
      (bed-size, teaching status, location), encounter-level patient data (demographics, admission
      source, payer), comprehensive time-stamped medication orders, pharmacy records, laboratory
      results, admission and discharge diagnoses (International Classification of Diseases Ninth
      Revision Clinical Modification, ICD-9-CM codes) and procedures were available.

      Study Population Adults that underwent isolated valve, isolated CABG or two or more
      procedures utilizing CPB, and who survived for at-least 24 hours were eligible for inclusion
      (except when CABG was performed emergently following a PCI). Procedures were identified using
      ICD-9-CM codes (39.61 = extracorporeal circulation auxiliary to open heart surgery) or CPT
      codes (indicating 'on-pump' surgery). Patients with missing or incomplete admission,
      procedure, and/or discharge dates, gender, and age were excluded. Discrete encounters less
      than four hours apart within the same hospital system, were considered contiguous. We also
      excluded those patients undergoing heart transplantation (ICD-9 procedure code 37.51) or with
      any of the following Elixhauser comorbidities: AIDS, lymphoma, metastatic cancer, solid
      tumors without metastases. Only the first operative procedure during this time was considered
      and patients undergoing multiple non-contiguous procedures were excluded.

      Definition of Exposure The study cohort consisted of patients that had either received at
      least 500mL of any crystalloid (0.9% saline, buffered salt solutions such as Plasma-Lyte,
      Lactated Ringers etc.) with or without any volume of 5% albumin - the 'albumin' and
      'crystalloid only' cohorts respectively. All intravenous fluids documented on the day of or
      the day following surgery were considered in order to determine eligibility for inclusion,
      and fluid volumes from the day of through two days following surgery were monitored. The
      investigators excluded crystalloids administered in smaller containers (<=250mL volume) as
      these were most likely to be used for medication delivery rather than for the maintenance of
      hydration or expansion of intravascular blood volume in this adult population. Such volume
      thresholds were not imposed for colloids in the 'albumin' cohort however. Patients were
      excluded from the study if they received any other colloid (e.g. albumin over 5%
      concentration or hydroxyethyl starch) or hypertonic saline. Patients were not excluded from
      the albumin arm if they received plasma protein fraction (PPF) however.

      Definition of Outcomes The primary outcome was in-hospital mortality during the index
      admission in which cardiac surgery was performed. The investigators also examined in-hospital
      mortality within 30, 60, and 90 days after the index procedure. Secondary endpoints included
      major postoperative adverse cardiac, renal, hepatic, metabolic, pulmonary, neurologic,
      hematologic, or infectious events defined using clinical parameters or administrative codes
      (ICD-9-CM). Additional administrative secondary outcomes included: Length-of-stay,
      readmissions, and re-operations (return to operating room). MACE at 30, 60 and 90 days were
      calculated from four separate binary categories: 1) in-hospital mortality; 2) post-operative
      stroke or cerebrovascular accident per ICD-9 diagnosis codes not present-on-admission for the
      index visit or for subsequent visits within respective MACE timeframes; 3) post-operative
      revascularization or PCI; and 4) post-operative myocardial infarction. A composite binary
      indicator was also reported for any one or greater MACE condition met within the respective
      timeframes.
    

Intervention name(s): Albumin
Intervention type(s): Drug
Intervention description(s): patients that had either received any volume of 5% albumin in addition to at least 500mL of any crystalloid (0.9% saline, buffered salt solutions such as Plasma-Lyte, Lactated Ringers etc.)
Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        Adults that underwent isolated valve, isolated CABG or two or more procedures utilizing CPB