Abstract
ABSTRACT
Objective
Acid–base patterns and their association with clinical outcomes have not been characterised using venous‐specific reference ranges in a sedative‐specific cohort. We aimed to characterise acid–base phenotypes in sedative toxidrome using venous‐specific thresholds, examine agent‐specific associations and evaluate relationships to adverse outcomes.
Methods
Retrospective cohort study of 374 consecutive patients referred to a toxicology service with sedative poisoning between November 2022 and November 2023. VBG data (pH, pCO
2
, HCO
3
and lactate) were classified into acid–base phenotypes using venous‐specific reference ranges (venous respiratory acidosis: pH 2
> 51 mmHg; hypercapnia with preserved pH: pH 7.31–7.41, pCO
2
> 51 mmHg). Outcomes of interest were endotracheal intubation, ICU admission and in‐hospital complications. Associations were assessed using chi‐squared tests, Mann–Whitney
U
tests and ROC curve analysis.
Results
VBG was obtained in 330 of 374 patients (88.2%). Venous respiratory acidosis occurred in 54 patients (16.4%), hypercapnia with preserved pH in 81 (24.5%) and normal venous pH in 153 (46.4%). Opioid exposures had the highest hypercapnic burden (59%) compared with anti‐psychotic exposures (20%;
p
p
= 0.001) and complications (64.8% vs. 32.7%,
p
2
≥ 65 mmHg was associated with ICU admission in 50.0%. Venous pH had the strongest discriminative performance across outcomes (AUC 0.631–0.683).
Conclusions
Venous respiratory acidosis identifies a high‐risk subgroup. Hypercapnic burden varies substantially by agent class. These findings support routine early VBG measurement in sedative overdose and highlight the importance of venous‐specific thresholds when interpreting point‐of‐care acid–base results.