Estimation of renal function in the intensive care unit: the covert concepts brought to light

Abstract

Frantic efforts have been made up to this date to derive consensus for estimating renal function in critically ill patients, only to open the Pandora's box. This article tries to explore the various methods available to date, the newer concepts, and the uncared issues that may still prove to be useful in estimating renal function in intensive care unit patients. The concept of augmented renal clearance, which is frequently encountered in critically ill patients, should always be taken into account, as correct therapeutic dosage of drugs sounds vital which in turn depends on correctly calculated glomerular filtration rate. Serum creatinine and creatinine-based formulae have their own demerits that are well known and established. While Cockcroft-Gault and 4-variable modification of diet in renal diseases formulae are highly inadequate in the intensive care setup for estimating glomerular filtration rate, employing isotopic methods is impractical and cumbersome. The 6-variable modification of diet in renal diseases formula fairs better as it takes into account the serum albumin and blood urea nitrogen, too. Jelliffe's and modified Jelliffe's equations take into account the rate of creatinine production and volume of distribution which in turn fluctuates heavily in a critically ill patient. Twenty-four-hour and timed creatinine clearances offer values close to reality although not accurate and cannot provide immediate results. Cystatin C is a novel agent that offers a sure promise as it is least influenced by factors that affect serum creatinine to a major extent. Aminoglycoside clearance, although still in the dark area, may prove a simple yet precise way of estimating glomerular filtration rate in those patients in whom these drugs are therapeutically employed. Optic ratiometric method has emerged as the most sophisticated one in glomerular filtration rate estimation in critically ill patients.

Population pharmacokinetics and target attainment of ciprofloxacin in critically ill patients

“…Cockcroft-Gault or MDRD), which is not validated for critically ill patients. Changes in serum creatinine are delayed after changes in GFR, and fluid changes in critically ill patients can seriously complicate the capability of serum creatinine to detect small changes in kidney function [50,51].…”

Creatinine Versus Cystatin C: Differing Estimates of Renal Function in Hospitalized Veterans Receiving Anticoagulants

“…2,3 All three equations have limited accuracy for patients with extremely low or high body mass, high glomerular filtration rates, advanced age, and non-white/ non-black ethnicities and races. 13 These equations all rely on serum creatinine, which can fluctuate in acute illness and is often falsely low in chronically ill persons relative to their kidney function. [9][10][11]14 Current guidelines recommend against the sole use of creatinine to dose medications with safety concerns.…”

Consequence of Elevated Fibroblast Growth Factor 23 Levels in Acute Kidney Injury, Renal Recovery and Overall Survival in Intensive Care Unit Patients After Major Surgery

“…Participants were postoperatively admitted to the surgical ICU and developed AKI after emergent or scheduled major abdominal or vascular surgery. Renal function was defined as an estimated creatinine clearance (eGFR) (mL/min) which was estimated daily using the 6-variable Modification of Diet in Renal Disease equation (12). AKI was defined by a modified definition of the Kidney Disease: Improving Global Outcomes (KDIGO) AKI Workgroup, harmonizing differences between the Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease (RIFLE) and the Acute Kidney Injury Network (AKIN) definitions.…”