CLINICAL SIGNIFICANCE OF METABOLIC ACIDOSIS IN CRITICALLY ILL PATIENTS WITH ACUTE KIDNEY INJURY

Introduction:

Metabolic acidosis occurs because of a marked increase in endogenous production of acid (such as L-lactic acid and ketoacids), loss of HCO3-or potential HCO3-salts (diarrhea or renal tubular acidosis [RTA]), or progressive accumulation of endogenous acids. The Boston method, uses measurements of arterial pH, CO2 pressure (PCO2), and [HCO3-] plus an analysis of the anion gap (corrected for a normal plasma albumin level of 4.5 g/dL).This is the most widely used and generally accepted approach used clinically by Nephrologists, and the easiest model to understand. 

 An alternative to bicarbonate as an index of the metabolic component is base excess (BE), a parameter devised from experimentation and traditional acid-base theory by Siggaard-Andersen in 1960 .

 ATN is the most common form of intrinsic AKI, particularly in critically ill patients. It represents only one of multiple forms of AKI.

According to one study, the mortality of AKI in critically ill patients requiring dialysis is 80 %.. Small changes in serum creatinine of as little as 25% above baseline are a significant predictor of all-cause short-term mortality.

A meta-analysis of eight studies of hospitalized patients (most of whom were critically ill or had heart failure) confirmed a graded relationship between increasing severity of AKI and short-term mortality. Most importantly, it confirmed that even mild forms of AKI are clinically relevant; an increase in serum creatinine of 0.3 mg/dl (26 μmol/l) was associated with a short-term relative risk for death of 2.3 (95% CI 1.8-3.0).

 In this study we assess the mortality risk of patients admitted in ICU with acute kidney injury and different types of metabolic acidosis.

Methods:

Study setting: All patients diagnosed to have AKI and metabolic acidosis being admitted in ICU.

Study duration: 18 months - (1st July 2018 to 30th December 2019).

Study design– Prospective descriptive study

Sample size: 120

Inclusion criteria

•        Standard base excess < -3

•        Presence of Acute kidney injury

•        Admitted in ICU

Exclusion criteria

•        Age less than 18

•        Chronic Liver disease

•        Acute liver failure

•        CKD Stage 5

•        Poisoning

•        Acute coronary syndrome with cardiogenic shock.

•        Renal transplant recipients

In the study, patients admitted with metabolic acidosis and acute kidney injury due to different etiologies will be considered.

In the study population, the blood investigations are done immediately on admitting to ICU.

Metabolic acidosis in our study is sub grouped into lactate acidosis, high anion gap and normal anion gap metabolic acidosis.

•        Normal blood lactate concentration in unstressed patients is 0.5-1 mmol/L57. Patients with  critical illness can be considered to have normal lactate concentration of less than 2 mmol/L.

•        Hyperlactatemia defined as a persistent, mild to moderate (2-4 mmol/L57) increase in blood lactate concentration without metabolic acidosis.

•        Mild lactic acidosis is the persistence of arterial serum lactate (2-4mmol/L) in the presence of metabolic acidosis.

•        Severe lactic acidosis is the persistence of arterial serum lactate ( >4mmol/L ) in the presence of metabolic acidosis.

Sample Size estimation:

 Formula

 N= 

Where,

            p         :  Prevalence of lactic acidosis in critically ill patients with metabolic acidosis

            d         :  Absolute precision =9

            1- a/2 :  Desired Confidence level=95%

                     N=120

Calculation

Sample size    n=[1.962 *0.56(1-0.56)]/{0.09}2=120

Data collection method:   All variables were incorporated in a dedicated windows Excel sheet. All patients who get admitted in ICU in the hospital having acute kidney injury with metabolic acidosis will be evaluated. Data is collected from the electronic medical records. Multivariate logistic regression analysis will be the method used to check whether metabolic acidosis is an independent factor affecting the mortality in critically ill patients. 

Statistical method:

The statistical analysis was  performed by IBM  SPSS  Statistics 20 version.All categorical  variables will be described  as frequency  and percentage . All continues variable will be described as mean±S.D. Normality will be checked by Kolmogrov-smirnove test. Independent samples Kruskal-Wallis H test will be used to test the significance among the non-parametric data. Pearson Chi-square test fisher’s exact test will be used to find the association  between categorical variable. We  analyzed hospital survival in metabolic acidosis patients using the chi-square and the Kaplan-Meier methods.

Results:

Conclusions:

Acute kidney injury with any type of metabolic acidosis in critical care settings has a very high mortality (37.5 %).

Lactic acidosis has a higher mortality compared to high anion gap metabolic acidosis with normal lactates or normal anion gap metabolic acidosis.

The median  intensive care unit and  hospital stay was  higher in Lactic acidosis group compared  to High anion gap metabolic acidosis  group or Normal anion gap metabolic acidosis.

The mean Acute Physiology and Chronic health evaluation 2 score was also significantly higher in patients  who died (in all the three groups of metabolic acidosis.) .

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.