Closed-loop assisted versus manual goal-directed fluid therapy during high-risk abdominal surgery: a case-control study with propensity matching

Abstract

Introduction: Goal-directed fluid therapy strategies have been shown to benefit moderate- to high-risk surgery patients. Despite this, these strategies are often not implemented. The aim of this study was to assess a closed-loop fluid administration system in a surgical cohort and compare the results with those for matched patients who received manual management. Our hypothesis was that the patients receiving closed-loop assistance would spend more time in a preload-independent state, defined as percentage of case time with stroke volume variation less than or equal to 12%.

Methods: Patients eligible for the study were all those over 18 years of age scheduled for hepatobiliary, pancreatic or splenic surgery and expected to receive intravascular arterial blood pressure monitoring as part of their anesthetic care. The closed-loop resuscitation target was selected by the primary anesthesia team, and the system was responsible for implementation of goal-directed fluid therapy during surgery. Following completion of enrollment, each study patient was matched to a non-closed-loop assisted case performed during the same time period using a propensity match to reduce bias.

Results: A total of 40 patients were enrolled, 5 were ultimately excluded and 25 matched pairs were selected from among the remaining 35 patients within the predefined caliper distance. There was no significant difference in fluid administration between groups. The closed-loop group spent a significantly higher portion of case time in a preload-independent state (95 ± 6% of case time versus 87 ± 14%, P =0.008). There was no difference in case mean or final stroke volume index (45 ± 10 versus 43 ± 9 and 45 ± 11 versus 42 ± 11, respectively) or mean arterial pressure (79 ± 8 versus 83 ± 9). Case end heart rate was significantly lower in the closed-loop assisted group (77 ± 10 versus 88 ± 13, P =0.003).

Conclusion: In this case-control study with propensity matching, clinician use of closed-loop assistance resulted in a greater portion of case time spent in a preload-independent state throughout surgery compared with manual delivery of goal-directed fluid therapy.

Trial registration: ClinicalTrials.gov Identifier: NCT02020863. Registered 19 December 2013.

Figures

Figure 1

Manual goal-directed fluid therapy protocol. The protocol that anesthesia providers utilize in moderate- and high-risk surgery cases at University of California Irvine Medical Center and that was applied to the patients in the manual group. C.I., Cardiac index; IBW, Ideal body weight; SV, Stroke volume; SVV, Stroke volume variation.

Figure 2

Recruitment and case-matching process. Potential subjects were recruited throughout the study period. At the end of recruitment, and after excluding five cases due to aborted procedures or decision to proceed without an arterial line, there were thirty-five study cases in the closed-loop assisted group. During the same time period, 60 other patients who met the inclusion criteria received manual goal-directed fluid therapy (GDFT). All 35 study patients and 60 manual group patients were run in a propensity match process, after which each closed-loop assisted patient was matched to the closest possible manual patient, leaving 35 patients in each group. ASA, American Society of Anesthesiologists Physical Status patient classification; HR, Heart rate; MAP, Mean arterial pressure; SVI, Stroke Volume Index.

Figure 3

Hemodynamics for the first 5 hours of all cases. Each graph is an overlay of all 25 patients in the group. Only the first 300 minutes of cases (if longer than 5 hours) are shown.

Figure 4

Goal-directed fluid therapy compliance by group. Box plots for the manual and closed-loop assisted groups, including outliers, are shown. The closed-loop assistance not only improved mean compliance to goal-directed fluid therapy (GDT) principles but also substantially reduced the variability in compliance within the group (manual group compliance standard deviation (SD) =14%, closed-loop group compliance SD =6%). Asterisks represent outliers, dot represent extreme outliers.