The haemodynamic instability score: Development and internal validation of a new rating method of intra-operative haemodynamic instability.

BACKGROUND: There is no consensus on how to define haemodynamic instability during general anaesthesia. Patients are often classified as stable or unstable based solely on blood pressure thresholds, disregarding the degree of instability. Vasoactive agents and volume therapy can directly influence classification but are usually not considered.

OBJECTIVE: To develop and validate a scoring tool to quantify the overall degree of haemodynamic instability.

DESIGN: Retrospective observational study.

SETTING: University hospital.

PATIENTS: The development cohort consisted of 50 patients undergoing high-risk surgery with a control group of 50 undergoing video-assisted thoracoscopic surgery. In the validation cohort, there were 153 high-risk surgery patients and 78 controls.

INTERVENTION: None.

MAIN OUTCOME MEASURES: The haemodynamic instability score (HI-score) was calculated as a weighted continuous measure ranging from 0 to 160 points, intended to reflect deviations of blood pressure and heart rate from predefined thresholds, and infusion rates of vasoactive agents and fluids. Thresholds were first determined in a development cohort and subsequently tested in a validation cohort. Results are presented as median [interquartile range].

RESULTS: In the validation cohort the HI-score was 59 [37 to 96] in the high-risk surgery group compared with 44 [24 to 58] in the control group (P < 0.001). The score of the haemodynamic domain did not differ (P = 0.69) between groups: 10 [8 to 16] vs. 10 [8 to 16]. However, scores for volume therapy and vasoactive medication were significantly higher in the high-risk surgery group compared with the control group: 14 [6 to 30] vs. 6 [2 to 18], P = 0.003 and 35 [15 to 75] vs. 15 [5 to 35], P < 0.001, respectively.

CONCLUSION: We developed the HI-score and demonstrated that it can appropriately quantify the degree of intra-operative haemodynamic instability. The HI-score provides a clinical tool which, after further external validation, may have future applications in both patient management and clinical research.