This was a prospective observational study in the medical intensive care unit (MICU) of the National Hospital, Colombo, Sri Lanka over a six-month period. We screened all patients admitted to the MICU for inclusion. We excluded patients who had chronic kidney disease and were on renal replacement therapy, and those whose duration of ICU stay was shorter than 48 hours.
Standard demographic, clinical and physiological data was obtained prospectively from all the patients.
Demographic information included age, gender and date of admission. Clinical data included the primary diagnosis, presence of co-morbidities and the need for mechanical ventilation. Physiological data included Glasgow Coma Scale, arterial oxygen tension (PaO2)/fraction of inspired oxygen (FiO2) ratio, blood pH, serum sodium, potassium, bilirubin, haemoglobin, platelet and white cell count. Data on kidney function included serum creatinine, urea and urine output. Severity of illness on admission and during the ICU stay was assessed using the SOFA score.
We defined several primary diagnostic categories based on the primary reason for admission to ICU; classification into a diagnostic category was based on the diagnosis documented at the point of admission by the treating clinician. A diagnosis of sepsis/septic shock was made where the primary reason for admission was a sepsis related diagnosis , and included sepsis associated with pneumonia, gastrointestinal disease, urinary tract infections, central nervous system infections, soft tissue infections and sepsis of undetermined source. A cardiac diagnosis was made where the primary reason for admission was cardiogenic shock (systolic blood pressure <90 mmHg, absence of hypovolemia, and clinical signs of poor tissue perfusion i.e., oliguria, cyanosis, cool extremities, altered mentation ), cardiac arrest, congestive cardiac failure (bilateral basal crackles, cardiomegaly, elevated jugular venous pressure ) and acute myocardial infarction (rise in troponin and either ischaemic chest pain, new ST-T wave changes or pathological Q waves on ECG ). A respiratory diagnosis encompassed primary respiratory arrest, aspiration syndrome, non-cardiogenic pulmonary oedema (not related to sepsis), exacerbations of chronic obstructive pulmonary disease or asthma, and pulmonary embolism. A diagnosis of gastrointestinal haemorrhage included bleeding due to peptic ulcers, diverticulosis and varices. All other non-surgical gastrointestinal diagnoses were categorized as ‘other’.
A metabolic/poisoning diagnoses included non-operative causes of metabolic coma, diabetic ketoacidosis, drug overdose or other endocrinopathies. Primary neurologic diagnoses included stroke, intra-cerebral haemorrhage, subarachnoid haemorrhage, epidural haematoma or other neurological causes for coma.
AKI was defined based on the AKIN criteria , as an abrupt (within 48 hours) reduction in kidney function (absolute increase in serum creatinine of ≥0.3 mg/dl (≥26.4 μmol/l), percentage increase in serum creatinine of ≥50% (1.5-fold from baseline), or reduction in urine output (documented oliguria of <0.5 ml/kg per hour for more than six hours)). The 3 stages of AKI were considered to be: stage 1- increase in serum creatinine of ≥0.3 mg/dl (≥26.4 μmol/l) or increase to ≥150% to 200% (1.5-2-fold) from baseline or urine output < 0.5 ml/kg per hour for >6 hours; stage 2- increase in serum creatinine to >200% to 300% (>2- to 3-fold) from baseline or urine output <0.5 ml/kg per hour for >12 hours; stage 3- increase in serum creatinine to >300% (>3-fold) from baseline (or serum creatinine of ≥4.0 mg/dl (≥354 μmol/l) with an acute increase of at least 0.5 mg/dl (44 μmol/l) or urine output <0.3 ml/kg per hour for 24 hours or anuria for 12 hours.
Data was collected using a structured datasheet, administered by a research assistant, from the case notes and by interviewing the patients (or relatives where the patients were unable to communicate) and treating physicians. Collected data were analyzed using SPSS version 16.0®. Categorical data were expressed as proportions and subgroups were analyzed using Pearson Chi-square test. Kaplan-Meier analysis was used to compare length of stay.
Ethics clearance was obtained from the Ethics Review Committee, National Hospital, Colombo on 07th December 2011 (No AA/ETH/2011). Informed written consent was obtained from patients, or from the closest relative where the patient was too ill to communicate. All investigations that the patients were subjected to were a part of the routine workup done in any critically ill patient. No personal information was collected, and individual patient data was coded to the bed-head ticket number. All datasheets were kept in a locked cabinet by the senior investigators.