A hospital recently asked about the existence of evidence and recommendations regarding tourniquet inflation/deflation cycles, after a complicated knee surgery in that hospital lasted 7 hours with three separate inflations of 2 hours, 1 hour 15min. and 40 min. with 30 min. deflation between the first and second inflation and approximately 1 hour deflation between the second and third inflation.
The following excerpts from the existing literature provide information on recommended tourniquet inflation times and re-inflation practices. The excerpts demonstrate that there are no established, evidence-based recommendations for tourniquet re-inflation times and durations. Also evident from these excerpts is any mention of tourniquet pressures, yet there is convincing and well established evidence that higher tourniquet pressure levels and higher tourniquet pressure gradients beneath the cuff are associated with higher probabilities of nerve and soft-tissue injuries . There is also good evidence that lower and safer personalized tourniquet pressure levels and pressure gradients can be achieved through the measurement of the Limb Occlusion Pressures (LOPs) of individual patients . Thus to develop evidence for a best practice, a future study might be warranted in which tourniquet pressure levels and pressure gradients are studied in conjunction with different inflation/deflation/reinflation periods.
| “One way of avoiding ischemic injury to muscle cells may be to employ a so-called tourniquet downtime technique, in which the tourniquet is released for a short period and then is reinflated. However, there is no evidence to support use of this technique, the suggested reperfusion time between successive ischemic periods has ranged from three to twenty minutes47, and time limits for subsequent ischemia are unknown. Furthermore, some authors have questioned the benefit of any tourniquet release and reinflation if the total tourniquet time does not exceed three hours48. In view of this controversy and in the absence of convincing evidence otherwise, we do not recommend a routine tourniquet inflation time of more than two hours. Accurate monitoring and minimization of tourniquet time are recommended.” 
| “There is no clearcut rule as to how long a tourniquet may be inflated safely, although various investigators have addressed effects of ischemia on muscle and nerve to define a relatively “safe” period of tourniquet hemostasis. In practice, safe tourniquet inflation time depends greatly on the patient’s anatomy, age, physical status, and the vascular supply to the extremity. Unless instructed otherwise, report to the surgeon when 60 minutes of tourniquet time has elapsed. There is general agreement that for reasonably healthy adults, 90 minutes should not be exceeded without releasing the tourniquet for a short time.
Releasing the tourniquet allows for removal of metabolic waste products from the limb and nourishment of the tissue with oxygenated blood. During this time, elevate the limb 60 degrees to encourage venous return and apply steady pressure to the incision with a sterile dressing. Tissue aeration periods should last at least 10 and preferably 15 minutes the first time and 15 – 20 minutes subsequently. To proceed with the surgery, re – exsanguinate the limb before reinflating the cuff. Take care during this procedure to maintain the sterility of the operative field. No known safe limit to the number of aeration intervals during prolonged tourniquet time has been established.”
| “Even with relatively short tourniquet inflation times (ie, 26 minutes ± eight minutes), researchers have found significant markers of systemic inflammatory response when they were measured 15 minutes after tourniquet deflation.106 Inflation times of 60 minutes for an upper extremity and 90 minutes for a lower extremity have been identified as a general guideline for inflation duration.17 However, some sources indicate that two hours is a safe time limit for tourniquet inflation.20,31 In pediatric patients, inflation times of less than 75 minutes for lower extremities has been recommended.114
Irreversible skeletal muscle damage is thought to begin after three hours of ischemia and is extensive at six hours.115 Allowing intermittent reperfusion restores oxygenation and releases toxins.31 Deflating the tourniquet every two hours with at least a 10-minute reperfusion time has been identified as a strategy to consider to decrease the risk for tissue damage.28 Another approach is to release the tourniquet after 90 minutes for at least 10 to 15 minutes for the first reperfusion period, then 15 to 20 minutes for each subsequent reperfusion period.17 However, it has also been reported that implementing reperfusion periods after 60 to 90 minutes of ischemia can contribute to muscle injury. 23 ”
| “The practice of using breathing periods represents an attempt to reduce ischaemic injury. This involves releasing the tourniquet after a set period of ischaemia to allow reperfusion, with the aim of returning tissue to its pre-ischaemic state, before subjecting the limb to a further period of ischaemia. Several studies have defined the appropriate breathing periods for the time ischaemia is required.
Pedowitz, using technetium uptake, found in a rabbit model that with a tourniquet time of four hours, skeletal muscle injury beneath the cuff was reduced significantly by hourly ten minute reperfusion intervals.11 He noted that a ten-minute reperfusion period after a two-hour tourniquet tended to exacerbate muscle injury. Reperfusion intervals could prolong the duration of anaesthesia, increase blood loss, or produce haemorrhagic staining and oedema.12 Nevertheless, Sapega and colleagues recommended on the basis of studies on dogs that ischaemic injury to muscle can be minimised by limiting the initial period of tourniquet time to 1.5 hours.13 Release of the tourniquet for five minutes permitted a further period of 1.5 hours. With knowledge of the ischaemia–reperfusion syndrome, the use of breathing periods is not logical, as reperfusion is now recognised as a major cause of damage to limbs after ischaemia. Further damage by free-radical-mediated mechanisms is likely even after the biochemistry of the venous blood returns to normal equilibrium. Work in animals has suggested that allowing reperfusion may actually increase the amount of damage to the ischaemic limb in certain structures.14 ”
A PDF containing selected excerpts from the references below can be found here
 Noordin S, McEwen JA, Kragh JF Jr, Eisen A, Masri BA. Surgical tourniquets in orthopaedics. J Bone Joint Surg Am. 2009;91(12):2958-2967.
 Younger AS, McEwen JA, Inkpen K. Wide contoured thigh cuffs and automated limb occlusion measurement allow lower tourniquet pressures. Clin Orthop Relat Res. 2004 Nov;(428):286-93.
 McEwen JA. Tourniquet use and care. http://www.tourniquets.org/use_care.php
 Recommended practices for care of patients undergoing pneumatic tourniquet-assisted procedures. In: Perioperative Standards and Recommended Practices. Denver, CO: AORN, Inc; 2013; p. e25-e50.
 Klenerman L. The Tourniquet Manual Principles and Practice. London: Springer; 2003.
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