Interrogating a clinical database to study treatment of hypotension in the critically ill

Abstract

Objective: In intensive care, it is imperative to resolve hypotensive episodes (HEs) in a timely manner to minimise end-organ damage. Clinical practice guidelines generally recommend initial treatment with fluid resuscitation followed by vasoactive agent administration if patients remain hypotensive. However, the impact of such interventions on patient outcomes has not been clearly established. Hence, the objective of this study was to investigate the relationship between fluid and vasoactive agent interventions and patient outcomes, while highlighting the utility of electronic medical records in clinical research.

Design: Retrospective cohort study.

Setting: Intensive care units (ICUs) at a large, academic, tertiary medical center.

Participants: Patients in Multi-parameter Intelligent Monitoring in Intensive Care II (a large electronic ICU database) who experienced a single HE during their ICU stay. 2332 patients had complete data.

Primary and secondary outcome measures: The primary outcome of interest was inhospital mortality. Secondary outcomes were ICU length of stay (LOS), HE duration, Hypotension Severity Index (defined as the mean arterial pressure curve area below 60 mm Hg during the HE) and rise in serum creatinine.

Results: Fluid resuscitation was associated with significantly shorter ICU LOS among ICU survivors (p=0.007). Vasoactive agent administration significantly decreased HE duration (p<0.001) and Hypotension Severity Index (p=0.002) but was associated with increased inhospital mortality risk (p<0.001), prolonged ICU LOS among ICU survivors (p=0.04) and rise in serum creatinine (p=0.002) after adjustment for confounders. Propensity score analyses as well as sensitivity analyses in treatment-, diagnosis- and ICU service-specific subpopulations corroborated the relationship between vasoactive agents and increased inhospital mortality.

Conclusions: An adverse relationship between vasoactive agents and inhospital mortality was found in patients with hypotension. This study has implications for the care of critically ill patients with hypotension and illustrates the utility of electronic medical records in research when randomised controlled trials are difficult to conduct.

Figure 1

A pictorial illustration of Hypotension Severity Index (HSI) calculation. The greyed area in mm Hg·min represents the HSI in this particular case. Consecutive mean blood pressure measurements are linearly interpolated, and the area below 60 mm Hg from the first to last measurement of the hypotensive episodes (HE) is computed. HSI has the advantage of harnessing both magnitude of mean blood pressure and HE duration.