Augmented Renal Clearance in the Adult Non-critically Ill Surgery Patient: a Prospective Point Prevalance Study and Identification of Risk Factors

This point prevalence study investigates the prevalence of augmented renal clearance (i.e. a measured 8-hour urinary creatinine clearance >= 120 ml/min/1.73m²) in an adult non-critically ill abdominal and trauma surgery population.

Secondary objectives are the identification of risk factors associated with ARC in this specific study population.

In every included patient, an 8-hour urine collection was carried out over an 8-hour time period to determine the CrCl8h. Participants were asked to empty the bladder at the start of the collection. From then, patients were asked to collect urine in a recipient during the following 8 hours. If an indwelling transurethral or suprapubic urinary catheter was in situ, the collection bag was emptied at the start of the collection. After 8 hours, total urinary volumes (Uv8h) were measured with a measuring cup and urinary creatinine concentrations were determined by laboratory analysis (enzymatic analysis by Roche Diagnostics). Midterm serum creatinine samples were obtained at 4 hours after the start of the urinary collection. Based on these values, CrCl8h was calculated according to the standard formulas and normalized to a body surface area (BSA) of 1.73m².

The following demographic and clinical data were prospectively recorded or calculated: age, sex, total body weight, lean body weight, length, BMI, BSA, presence of an urinary catheter, pre- or postoperative status, 'preoperative American society of anesthesiology' (ASA) score, relevant medical history with respect to the kidney function or SCr levels (i.e. arterial hypertension, chronic kidney disease, diabetes mellitus, paralyzed patients or patients with amputated limb(s)), length of stay (LOS) since admission in the hospital until the day of collection (LOShosp), since admission on the ward until the day of collection (LOSward), since surgery until the day of collection (LOSsurgery), LOS in the hospital at discharge (LOSdisch), number of surgical interventions since admission until the day of collection, the mean daily volume of administered fluids based on the 3 days before the day of collection (d-3, d-2, d-1) as well as on the day of collection (d0), the relevant co-medication during d-3, d-2 and d-1 as well as d0, number of patients with one or more postoperative complication(s) (POC), number of POCs per patient and the highest severity grade of POCs per patient, C-reactive protein concentration (CRP) and white blood cell count (WBC) on d-1 or d0, baseline SCr (i.e. a SCr value from maximum 1 year old collected during a consultation), preoperative SCr (i.e. first SCr during hospital stay but before any surgical procedure) and SCr at discharge from the hospital. From the surgical procedure closest to the day of collection, we collected duration of anesthesia and surgical procedure, the administration of vasopressor agents, the volume and type of resuscitation fluids administered during surgery (i.e. crystalloids, colloids or blood derivates) and volumes of urine and blood loss. Additionally, in abdominal surgery patients, following demographic data were collected: elective or emergency surgical procedure, presence of a nasogastric tube and an ileo- or colostoma on the day of collection, reason for admission (i.e. colorectal, hepatobiliary or other), whether there was an oncologic indication for surgery and laparoscopic or open surgery. In trauma surgery patients following demographic data were collected additionally: the injury severity score (ISS) on admission, diagnosis at admission (i.e. trauma with fracture, trauma without fracture, infection, removal of osteosynthesis material or other) and type of fracture (if trauma with fracture). The type and severity of postoperative complications were classified using the Clavien-Dindo classification. All data were retrieved from the patient's computerized medical files and were registered in a patient study file (appendix 9.3) and in a Microsoft Office Access 2007 database.