In critically subjects in ICU, they need constant care and vigilance. Despite all patients being treated, triage protocol must be adapted. Evaluation of subjects with extreme intensive care need us vital for clinician, it has higher importance in India and alike nations that have a poor bed to patients’ ratio. Hence, it is vital for clinicians in ICU to keep priority based on survival chances and prognosis. Normal pH of blood is an outcome of efficacious acid-base balance, which is vital for consistent organ and cell function. The acid-base status is maintained with a narrow range of proper body functioning. pH derangement in body result in subjects requiring intensive support till machinations are brought under control of internal hemostasis in the body.¹

ABG or arterial blood gas has proved its vital role since long showed its vital role in managing critically ill subjects. It has been assessed that standard base excess and lactate can help in providing more comprehensive view of mortality and health in a subject. When metabolism of body disturbs, its sometime increase acid build-up owing to various factors as decreased flushing of tissues due to blood stasis and oxygen supply-demand imbalance. Base excess provides measure of acid-base imbalance in body. Base excess is described as standalone indicator of metabolic acidosis or alkalosis. It can determine illness severity and is independent of any underlying respiratory disorders. Standard base excess is difference in normalized base buffer and actual base buffers in standard conditions. Concerning clinical aspect, standard base excess represent amount of base which must be neutralized or added to attain a pH of 7.4 under controlled condition of 37°C and 40mmHg.²

Another parameter that can be assessed with ABG analyzer that provides an overview of acid-base status in the body is lactate. Hyperlactatemia has been linked with adverse outcomes in critically ill subjects. Various studies on sepsis subjects have reported lactate as a useful tool for identification. Subjects that present with shock usually have hyperlactatemia which result from tissue hypoperfusion (type A lactic acidosis). Treatment is aimed to increase oxygen delivery by using inotropic therapy, blood transfusions, and fluids. Hyperlactatemia can also arise from independent causes than anaerobic metabolism (type B lactic acidosis) as impaired mitochondrial oxidation, sympathetic stimulation, and hepatic dysfunction. On the other hand, sepsis affects lactate clearance which can lead to increased lactate level in circulation even when impaired vital signs are not seen. Point-of-care lactate testing can enable early illness detection as atraumatic or septic shock that can have adverse patient outcomes.³

Recent literature data has reported that base excess improvement and lactate clearance improvement are more powerful indicators of mortality risk in critically ill patients than single-point measurement. The effect of initial treatment on the capability of the body to neutralize the derangements have a promising outcome even with highly abnormal levels at admission. Existing literature data reports that mortality rates are decreased significantly when these levels are corrected in the first 24 hours.⁴ The present study was aimed to assess the effect of change in the BE (base excess) and lactate clearance in the first 24 hours on the clinical outcomes in critically ill subjects admitted to the intensive care unit of an Indian institute.

The present retrospective study was aimed to assess the effect of change in the BE (base excess) and lactate clearance in the first 24 hours on the clinical outcomes in critically ill subjects admitted to the intensive care unit of an Indian institute. The study was done at Department of Pathology and General Medicine of the Institute. Verbal and written informed consent were taken from all the subjects before study participation. The cadavers were taken from Department of Human Anatomy of the Institute.

The study assessed the records of all the subjects that were critically ill and were admitted to the Institute within the defined study period where medical data and records were extracted from ICU for ABG analysis. The study included subjects aged 18 years or more, admitted to the ICU on ventilatory support from the very first day, samples were received in the clinical biochemistry laboratory within 24 hours of admission, and had complete medical data and records. Heparinized arterial blood samples were received in laboratory that were used for ABG analysis. The exclusion criteria for the study were subjects that were admitted following elective surgical procedures and had incomplete records. Clinical outcomes assessed were duration of stay and mortality rates. Normal lactate levels and BE was taken as < 1.5 mmol/L and −2 to +2.

Subjects in the study were divided to non-survivors and survivors and their serum lactate and standard base excess were assessed at admission and 24 hours were collected and compared. Mean and standard deviation was assessed in both the groups. Mean level in non-survivors and survivors was assessed using independent t-test. Subjects were divided into 3 subgroups concerning lactate levels and SBE. First group included subjects that had abnormal levels that reached normal within 24 hours, 2^nd group had normal levels at admission that remained normal till 24 hours, and 3^rd group had abnormal levels that did not improve in 24 hours of admission.

The gathered were analyzed statistically using the chi-square test, Fisher’s exact test, Mann Whitney U test, and SPSS (Statistical Package for the Social Sciences) software version 24.0 (IBM Corp., Armonk. NY, USA) using ANOVA and student's t-test. The significance level was considered at a p-value of <0.05.

The present retrospective study was aimed to assess the effect of change in the BE (base excess) and lactate clearance in the first 24 hours on the clinical outcomes in critically ill subjects admitted to the intensive care unit of an Indian institute. The present retrospective study assessed 108 critically ill subjects that were retrospectively assessed for ABG (arterial blood gas) analysis and were admitted to ICU. Standard BE and lactate levels were assessed at admission and 24 hours after the admission. Subjects were divided into survivors and non-survivors where survivors were classified based in the change in levels in 24 hours and were correlated with the hospital stay duration.

It was seen that among 108 subjects admitted to ICU, the age range was 18-81 years with the mean age of 53 years. There were 68 male subjects and remaining subjects were females. The mean stay duration in these subjects was 7 days. Among 108 subjects, 22% (n=80) were non-survivors and 60% (n=64) subjects survived in the study. Mean lactate levels at admission in all subjects was 2.0±1.23 mmol/L, whereas, at 24 hours, it was 2.2±1.90 mmol/L. Median standard base excess at admission was -3.5, whereas, at 24 hours, it was -1.5. Reference range for lactate was taken as <1.5 mmol/L; SBE = –2 to +2 (Table 1).

The study results showed that the 108 subjects were divided as non-survivors and survivors to assess the correlation of lactate and SBE values to the mortality. The mean level of lactate at admission and at 24 hours of admission was assessed in non-survivors and survivors. The difference in the mean values at 24 hours-time was seen to be statistically significant in the two groups of survivors and non-survivors with the p-value of <0.001 (Table 2).

It was also seen that for median assessed at admission and 24- hours after admission in non-survivors and survivors, median SBE levels at 24 hours were significantly lower in non-survivors and survivors. These results correlated significantly to lactate levels and SBE for mortality with p-values of 0.03 and 0.01 respectively. Also, the subjects that were not normal since admission and SBE levels did not return to normal passed away. Subjects where lactate levels deranged after 24 hours of admission had longer stay duration compared to subjects where levels returned to normal had a shorter stay. However, change in SBE showed no significant effect on hospital stay duration with p=0.17.

Table 1: Descriptive statistics in the study participants

Table 2: Comparison of mean lactate levels in survivor and non-survivor study subjects

Table 3: Comparison of median standard base excess in non-survivor and survivors

The present retrospective study assessed 108 critically ill subjects that were retrospectively assessed for ABG (arterial blood gas) analysis and were admitted to ICU. Standard BE and lactate levels were assessed at admission and 24 hours after the admission. Subjects were divided into survivors and non-survivors where survivors were classified based in the change in levels in 24 hours and were correlated with the hospital stay duration. This design was similar to the study design adopted by the previous studies of Zhang Z et al⁵ in 2014 and Zante B et al⁶ in 2018 where study design similar to the present study was also adopted by the authors in their studies.

The study results showed that among 108 subjects admitted to ICU, the age range was 18-81 years with the mean age of 53 years. There were 68 male subjects and remaining subjects were females. The mean stay duration in these subjects was 7 days. Among 108 subjects, 22% (n=80) were non-survivors and 60% (n=64) subjects survived in the study. Mean lactate levels at admission in all subjects was 2.0±1.23 mmol/L, whereas, at 24 hours, it was 2.2±1.90 mmol/L. Median standard base excess at admission was -3.5, whereas, at 24 hours, it was -1.5. Reference range for lactate was taken as <1.5 mmol/L; SBE = –2 to +2. These results were consistent with the findings of Park M et al⁷ in 2011 and Husain FA et al⁸ in 2003 where authors assessed subjects with demographic data comparable to the present study.

It was seen that the 108 subjects were divided as non-survivors and survivors to assess the correlation of lactate and SBE values to the mortality. The mean level of lactate at admission and at 24 hours of admission was assessed in non-survivors and survivors. The difference in the mean values at 24 hours-time was seen to be statistically significant in the two groups of survivors and non-survivors with the p-value of <0.001. These findings were in agreement with the results of Kraut JA et al⁹ in 2010 and Caputo ND et al¹⁰ in 2015 where results reported by the authors for correlation of lactate and SBE values to the mortality were similar to the results of the present study.

The study results also showed that for median assessed at admission and 24- hours after admission in non-survivors and survivors, median SBE levels at 24 hours were significantly lower in non-survivors and survivors. These results correlated significantly to lactate levels and SBE for mortality with p-values of 0.03 and 0.01 respectively. Also, the subjects that were not normal since admission and SBE levels did not return to normal passed away. Subjects where lactate levels deranged after 24 hours of admission had longer stay duration compared to subjects where levels returned to normal had a shorter stay. However, change in SBE showed no significant effect on hospital stay duration with p=0.17. These results were in line with the findings of Kellum JA et al¹¹ in 2000 and Shapiro NI et al¹² in 2005 where results for SBE in survivors and non-survivors were similar to present study.

The present study, within its limitations, concludes that there is a 24-hour trend in standard base excess and lactate levels that are strong predictors of mortality in ICU compared to initial values. Prompt treatment and care to control these metabolic derangements in first few hours of hospital admission which can greatly increase the probability of survival in subjects along with reduced morbidity.

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