Passive Leg Raising Attenuates and Delays Tourniquet Deflation-induced Hypotension and Tachycardia
Condition: Hypotension; Tachycardia
MeSH terms: Hypotension; Tachycardia
Study type: Interventional

Summary: 
      Background:

      The pneumatic tourniquet is frequently used in total knee arthroplasty. Tourniquet deflation
      may result in hypotension and tachycardia caused by the rapid shift of blood volume back to
      the ischemic limb and a decrease in cardiac preload. Passive leg raising (PLR) represents a
      "self-volume challenge" that can result in an increase in preload. Such a PLR-induced
      increase in preload was hypothesized to attenuate the decrease in preload resulting from
      tourniquet deflation. This study was designed to evaluate the effect of PLR on hypotension
      and tachycardia following tourniquet deflation.

      Methods:

      Seventy patients who underwent unilateral total knee arthroplasty were assigned to either the
      bilateral PLR group (n = 35) or the control group (n = 35), in a prospective randomized
      trial. The patients' blood pressure and heart rate were measured before, during, and after
      tourniquet deflation.
    

Detailed description: 
      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.

      Step 3 (T8-T10): In the PLR group, PLR was maintained and the tourniquet was deflated and
      hemodynamic recordings and measurements were taken at 2, 4, and 6 min after tourniquet
      deflation. At this step, blood pressure and heart rate were recorded for 6 min because
      previous reports have suggested that the nadir of the blood pressure occurred within 5 min
      after tourniquet deflation. In the control group, the tourniquet was deflated while the
      patient's legs remained in the baseline position and hemodynamic measurements were obtained
      at points corresponding to those in the PLR patients.

      Step 4 (T11-T17): In the PLR group, the legs were returned to the baseline position and a
      fourth set of recordings and hemodynamic measurements were obtained 1, 3, 5, 10, 15, 30, and
      60 min later. In the control group, the legs remained in the baseline position and
      corresponding hemodynamic measurements were obtained.

      Statistical Methods Differences in demographic characteristics and perioperative data between
      the PLR and control patients were examined using chi-square or Student's t tests, depending
      on the measure. Hemodynamic measurements were analyzed over time by comparing the T6-T17
      measurements to the T5 measurements in each group. Intragroup hemodynamic changes were
      analyzed using repeated measures one-way analysis of variance, followed by the Fisher's
      least-significant difference post-test. The generalized estimating equations test was used to
      compare the differences between groups (PLR and control group), with respect to blood
      pressure and heart rate measurements. The difference in the length of time from tourniquet
      deflation to the nadir in blood pressure between the groups was determined by Student's t
      test. The SPSS software (Version 15 SPSS Inc., Chicago, Illinois) was used for all analyses.
      All the tests were two-sided, and P < 0.05 was considered significant.
    

Intervention name(s): passive leg raising
Intervention type(s): Procedure
Intervention description(s): bilateral PLR was achieved by raising the legs of patient
Other intervention name(s): PLR
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Passive leg raising, blood pressure, heart rate