The Effect of Passive Leg Raising or Experimental Clinical Practices on the Prevention of Hypotension Following Tourniquet Release in Total Knee Arthroplasty Patients

This study was a prospective randomized trial, which was approved by the Institutional Review Board of the hospital, and informed consent was obtained from each patient enrolled in the study. Patients with degenerative joint disease of the knee scheduled to receive unilateral total knee arthroplasty were enrolled in this study within one year. Exclusion criteria were bilateral total knee arthroplasty, previous knee surgery, cardiac arrhythmia, uncontrolled hypertension (systolic blood pressure > 170 mmHg), presence of a known aortic aneurysm, recent stroke or myocardial infarction, unstable angina pectoris, New York Heart Association functional class III or IV, and American Society of Anesthesiologists physical status IV to V. A series of numbered, opaque, sealed envelopes were used to randomly allocate participants to the bilateral PLR group (n = 35) or to the control group (n = 35). The trial flow chart is illustrated in Figure 1. The primary outcome measures were the blood pressure and heart rate before, during, and after tourniquet deflation.

The sample size estimate, based on previous studies8, indicated that 35 patients were required for each group in order to have a 90% chance of detecting a significant difference (P = 0.05, two-sided) between the groups. Patients were premedicated with fentanyl and/or midazolam for anxiolysis 5 min before induction of anesthesia. Spinal anesthesia was performed via the L3-L4 or L4-L5 interspace with a single dose of isobaric bupivacaine. A drop in systolic blood pressure to lower than 90 mmHg triggered ephedrine administration during the study.

Figure 2 illustrates the study protocol, which was divided into 4 steps. Blood pressure and heart rate were measured at each time point (T1-T17) throughout the protocol. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean blood pressure (MBP) were measured using noninvasive, automated techniques and a continuous electrocardiogram allowed measurements of heart rate. In addition, the doses of bupivacaine and ephedrine administrated, as well as the upper anesthetized level, and total fluid volume administered before tourniquet deflation were recorded.

Step 1 (T1-T5): In both groups, after induction of spinal anesthesia, the patient was placed in a supine position with a well-padded proximal tourniquet. The leg was exsanguinated with an Esmarch bandage, and a pneumatic tourniquet was applied and inflated to a pressure of 280-300 mm Hg, followed by the arthroplastic surgery. Recordings and measurements were taken at 30, 15, 10, 5, and 1 min before bilateral PLR (step 2).

Step 2 (T6-T7): In the PLR group, at the completion of the total knee arthroplasty, bilateral PLR was achieved by raising the patient's legs to a 45 degree angle. Recordings and measurements were taken 2 and 4 min after initiation of PLR. In the control patients, the legs were left in the baseline position, but hemodynamic measurements were still taken at time points corresponding to those in the PLR group.