Do blood pressure changes following a small bolus of propofol correlate with fluid responsiveness as assessed with stroke volume variation – an experimental study

Abstract

Background For many years, in everyday practice at intensive care units (ICUs) and in high-risk surgery patients, there has been a need for objective and repetitive methods to assess patients’ volemia. Hypotension consecutive to propofol administration may be dependent on volemia. In oligovolemic patients, propofol-induced sympathetic nervous system depression may cause a decrease in blood pressure greater than that in normovolemic patients. The aim of the study was to determine whether blood pressure decrease after a small bolus of propofol will correlate with fluid responsiveness evaluated with stroke volume variation (SVV) obtained with a PiCCO (Getinge AB, Göteborg, Sweden) device. Methods We enrolled 50 intensive care unit (ICU) patients whose lungs were mechanically ventilated. The patients were temporarily sedated with midazolam infusion for the length of the trial. Prior to propofol injection, the following parameters were acquired for every patient: heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), invasive blood pressure and infusion rate of catecholamines and noradrenergic vasopressors. The PiCCO device was calibrated, and stroke volume variation (SVV) was calculated and recorded. Each patient received consecutive propofol boluses of 0.25 mg kg− 1, 0.5 mg kg− 1, and 1.0 mg kg− 1. After each bolus, systolic and diastolic invasive blood pressure, heart rate (HR), continuous cardiac output (CCO), continuous cardiac index (CCI), stroke volume index (SI), and stroke volume variation (SVV) were recorded every fifteen seconds for ten minutes. Results We found a statistically significant weak-to-moderate positive correlation after propofol 1 mg kg− 1 between ΔSBP and SVV for every timepoint (p < 0.05). Additionally, we discovered statistically significant differences (t test, p = 0.004), with a mean difference of -15.42 mmHg (95% CI, -25.73 to -5.11), between ΔSBP (135) in patients receiving > 0.2 mcg kg− 1 min− 1 norepinephrine and patients receiving ≤ 0.2 mcg kg− 1 min− 1 norepinephrine. Conclusion We found that a 1 mg kg− 1 bolus of propofol cannot predict fluid responsiveness in ICU patients receiving norepinephrine infusion. We believe, however, that these findings open a new field for further study in noninvasive haemodynamic measurements. Trial registration Prior to the study, Independent Bioethical Committee consent was sought and obtained (NKKBN/91-147/2019). This study was registered at ClinicalTrails.gov (NCT03917446) on 17th April 2019, retrospectively registered.