UTILITY OF SERIAL BLOOD GAS ANALYSIS IN GUIDING CONTINUOUS RENAL REPLACEMENT THERAPY (CRRT) MANAGEMENT IN A NIGERIAN ICU: A RETROSPECTIVE OBSERVATIONAL STUDY

Continuous renal replacement therapy (CRRT) is widely used for

managing acute kidney injury (AKI) and multi-organ dysfunction in critically ill

patients. However, maintaining acid–base balance and hemodynamic control during

therapy remains challenging, particularly in resource-limited ICUs. Serial blood gas

analysis (BGA) provides real-time feedback that can guide treatment adjustments, yet

evidence regarding its optimal frequency and clinical impact in African settings is

scarce. This study evaluated the effect of BGA frequency on metabolic control,

hemodynamic stability, and outcomes among patients receiving CRRT in a tertiary ICU

in Southeast Nigeria.

A retrospective observational study was conducted among 66 critically ill 

patients who underwent CRRT between January 2023 and January 2025 at Regions 

Healthcare, Owerri. Data were extracted from ICU records, including comorbidities, 

sepsis status, acid–base profiles, blood gas monitoring frequency, hemodynamic 

parameters, and survival outcomes. Metabolic acidosis was defined using two criteria

from the KDIGO Clinical Practice Guideline for Acute Kidney Injury and the Surviving 

Sepsis Campaign (SSC) definitions of tissue hypoperfusion

\: Definition 1 (pH <7.35, HCO₃⁻ <22 mmol/L, pCO₂ <45 mmHg, lactate ≥4 mmol/L) 

and Definition 2 (excluding lactate). Statistical associations were analysed using Chisquare, Fisher’s exact, and t-tests with significance set at p <0.05.

The mean age of patients was 58.2 ± 14.6 years. Predominant comorbidities

were hypertension (60.6%), chronic kidney disease (47.0%), and sepsis (86.4%). Using

Definition 1, metabolic acidosis was detected in 33.3% before CRRT, 30.3% during,

and 39.4% after therapy, suggesting persistent tissue hypoperfusion–driven acidosis.

When lactate was excluded (Definition 2), acidosis incidence fell to 13.6%, 9.1%, and

9.1%, respectively, indicating effective biochemical correction during CRRT.

Respiratory alkalosis was frequent, rising from 43.9% pre-CRRT to 56.1% post-CRRT,

implying compensatory hyperventilation. Persistent lactate elevation was more

frequently observed among patients treated with sustained low-efficiency dialysis

(SLED) and continuous veno-venous hemodiafiltration (CVVHDF). Although the frequency of BGA was not significantly related to acid–base adequacy (p=0.190), it

showed a meaningful impact on hemodynamic stability (p=0.041). Patients who had

more frequent BGA (≥6 times) exhibited less intradialytic hypotension (20%) and better

survival (80%) compared with those monitored fewer times (16.7–66.7% survival).

CRRT duration also varied significantly by BGA frequency (p<0.001), indicating

closer monitoring allowed for safer, sustained therapy. These findings suggest that

frequent, targeted BGA may enhance physiologic stability and CRRT tolerance even in

low-resource settings

Serial blood gas monitoring is a valuable bedside tool for guiding CRRT 

in critically ill Nigerian patients. While its frequency did not directly alter acid–base 

adequacy, it was strongly associated with improved hemodynamic control and a trend 

toward better survival. Incorporating standardized BGA-guided protocols could 

enhance CRRT outcomes and support clinical decision-making in ICUs with 

constrained resources. Further multicenter studies are warranted to establish frequencybased guidelines tailored to the African critical care context.