Advanced, Clinical Subspecialties
In regard to tourniquet management during limb surgeries, the inflation pressures, duration, and release guidelines are not clear. Traditionally, orthopedic surgeons have practiced fixed inflation pressures, typically 200-250 mmHg for upper arm and 250-350 mmHg for thigh; however, this practice does not take into account the age or BP of the patient. Surgeons have also practiced inflating a fixed amount of pressure above the systolic arterial pressure, typically +50-100 mmHg for upper arm and +100-150 mmHg for thigh. Most recently, however, guidelines set forth by the Association of periOperative Nurses (AORN) and Association of Surgical Technologists (AST) suggest using limb occlusion pressure (LOP) to calculate tourniquet inflation pressure. This is the pressure in the tourniquet at which the distal arterial blood flow, as assessed by a Doppler probe held over a distal artery, is occluded. The AORN guidelines recommend adding a “safety margin” to the LOP to cover intraoperative fluctuations in BP. For instance, if LOP < 130, 131-190, or >190 mmHg, the respective safety margins are 40, 60, and 80 mmHg. For pediatric patients, the safety margin is 50 mmHg.
Tourniquet deflation should occur after 1.5h for the upper limb and 2h for the lower limb for a period of at least 15 minutes to allow for limb re-perfusion prior to re-inflation if necessary. For pediatric patients, 1 hour is the recommended inflation time for both upper and lower extremities.
For IV regional anesthesia (Bier block), the proximal cuff should be inflated 50-100 mmHg above the arterial SBP. When tourniquet pain occurs (~30-45 minutes), management includes inflating the distal cuff, palpating the distal tourniquet to assure functionality, and deflating the proximal tourniquet. If the surgical procedure is completed within 20 minutes after IV injection of local anesthetic, gradually release the tourniquet in several steps, with 2-minute intervals between deflations to avoid local anesthetic systemic toxicity.