Evaluation of indigenously developed closed-loop automated blood pressure control system (claps): a preliminary study

Abstract

Closed-loop systems have been designed to assist anesthetists in controlling anesthetic drugs and also maintaining the stability of various physiological variables in the normal range. In the present study, we describe and clinically evaluated a novel closed-loop automated blood pressure control system (CLAPS) in patients undergoing cardiac surgery under cardiopulmonary bypass. Forty ASA II–IV adult patients undergoing elective cardiac surgery were randomly allocated to receive adrenaline, noradrenaline, phenylephrine and nitroglycerine (NTG) adjusted either through CLAPS (CLAPS group) or manually (Manual group). The desired target mean arterial blood pressure (MAP) for each patient in both groups was set by the attending anesthesiologist. The hemodynamic performance was assessed based on the percentage duration of time the MAP remained within 20% of the set target. Automated controller performances were compared using performance error criteria of Varvel (MDPE, MDAPE, Wobble) and Global Score. MAP was maintained a significantly longer proportion of time within 20% of the target in the CLAPS group (79.4% vs. 65.5% p < 0.001, 't' test) as compared to the manual group. Median absolute performance error, wobble, and Global score was significantly lower in the CLAPS group. Hemodynamic stability was achieved with a significantly lower dose of Phenyepherine in the CLAPS group (1870 μg vs. 5400 μg, p < 0.05, 't' test). The dose of NTG was significantly higher in the CLAPS group (3070 μg vs. 1600 μg, p-value < 0.05, 't' test). The cardiac index and left ventricular end-diastolic area were comparable between the groups. Automated infusion of vasoactive drugs using CLAPS is feasible and also better than manual control for controlling hemodynamics during cardiac surgery. Trial registration number and date This trial was registered in the Clinical Trial Registry of India under Registration Number CTRI/2018/01/011487 (Retrospective; registration date; January 23, 2018).

Appendix 1

• 1. Performance error (PE) = ((measured MAP – target MAP)/target MAP) *100

• 2. Median performance error (MDPE) = {median PEij, j = 1,..., Ni}, is the median of all the PE enumerated. It is a measure of bias and describes whether the measured values are systematically either above or below the target value.

• 3. Median absolute performance error (MDAPE) = median {|PE|ij, j = 1,..., Ni} It is a measure of inaccuracy of the control method.

• 4. Wobble = median {|PEij – MDPEi|, j = 1,..., Ni}, where i is the subject number, j the jth (one) measurement of the observation period, and N the total number of measurements during the observation period. It is an index of time-related changes in performance and measures the intrasubject variability in the performance errors.

• 5. Global score = (MDAPE + Wobble)/fraction of time spent in desired limits.

• 6. Vis score (vasoactive – inotropic score) = Dopamine dose (μg/kg/min) + Dobutamine dose (μg/kg/min) + 100 * Epinepheine dose (μg/kg/min) + 100*Norepinephrine dose (μg/kg/min) + 10,000*vasopressin dose (unit/kg/min)