After reviewing indications, precautions and potential complications, we now will address potential recommendations for tourniquet use in lower extremity surgery as compiled by review of the literature.
Key Recommendations Regarding Length Of Tourniquet Time
Non-disrupted inflation duration should be less than or equal to 120 minutes with a reperfusion interval of greater than or equal to 10 minutes every hour (beginning at 120 minutes of tourniquet inflation time). One consistency noted within this review of the literature is that tourniquet-related complications increase as tourniquet time increases;1 this directly relates to the hypoxic environment created by tourniquet inflation and the potential for resultant soft tissue damage.2
In general, animal studies suggest that at two hours of tourniquet inflation, the histologic,3 electrophysiological,4,5 and musculoskeletal impact4,6 of tourniquet use, while present and quantifiable, largely remains reversible.7
Few clinical studies examine tourniquet times greater than two hours. However, those studies with tourniquet inflation exceeding two hours displayed prolonged periods of ischemia that may cause irreversible complications; primarily neurologic.8,9 A systematic review of available literature conducted in 2012 commented on the lack of data available to distinguish at which point from 120 to 180 minutes is tourniquet inflation considered unsafe, later recommending that greater than or equal to 2.5 hours could be considered appropriate if one employs an appropriate ‘breathing period’ from the tourniquet.7
The (lower) pressures at which one uses tourniquets in modern practice may warrant further research in order to set specific time independent parameters for safe tourniquet use and to establish time as a separate factor from pressure. Until such data is available, most surgeons in practice accept the parameters of non-disrupted tourniquet inflation between 90-120 minutes as relatively safe2 with the need for reperfusion intervals assessed after the 120-minute mark.7
What You Should Know About Reperfusion Intervals
There is general agreement that tourniquet inflation should be for as short a time as possible, at as low a pressure as possible to minimize complications. However, there are certain circumstances under which surgery may exceed 120 minutes. For these circumstances, one may consider applying tourniquet “breathing periods.”7,10
A “breathing period” is a time of tourniquet deflation with subsequent re-inflation during the same procedure. This deflation interval allows for temporary reperfusion of the limb, assisting in repletion of the adenosine triphosphate (ATP) depleted during the period of ischemia11 as well as facilitating a shorter time to metabolic recovery with final tourniquet release.2,12,13 By decreasing metabolite load, reperfusion intervals are thought to be tissue protective in surgeries lasting over two hours.13
In an effort to determine optimal reperfusion times for prolonged tourniquet use, Newman demonstrated that hourly release of the tourniquet for 10 minutes ensured rapid metabolic recovery with maintenance of ATP levels in the muscle distal to the tourniquet. When deflating the tourniquet for intervals of only five minutes, tissue pH was more acidotic in the muscles beneath and distal to the tourniquet after subsequent ischemia.3
Pedowitz and colleagues came to a similar conclusion after measuring technetium-99 pyrophosphate uptake in animal skeletal muscle as a marker of muscle injury.4 In this study, researchers demonstrated that two hours of tourniquet-induced ischemia significantly increased technetium uptake in the thigh beneath the tourniquet; however, when employing hourly reperfusion periods of 10 minutes, there was significantly reduced technetium uptake into injured muscle (i.e. less injury observed).
As 120 minutes of non-disrupted inflation time appears to be safe, recommendations exist that if one anticipates a need for surgical hemostasis greater than two hours, one may minimize muscle injury with 10 minute reperfusion intervals after each hour of cuff inflation.4,7,12,14,15
How Shape And Size Of Tourniquets Affects Outcomes
Contoured (curved) cuffs permit lower efficacious tourniquet pressures compared to straight cuffs on conical shaped extremities, such as that of the lower extremity, wider cuffs (four to five inches) distribute pressure more evenly to tissue structures, and the cuff should overlap itself on application ideally by seven to 15 cm.12,16
With the lower extremity placement of tourniquets there are generally three respective areas of placement: thigh; calf; and ankle. Of those, thigh and ankle tourniquet placements are common in podiatric surgery. At the respective tourniquet locations, the lower extremity is essentially tapered and conical in shape rather than cylindrical.
The literature notes that the combination of using a tourniquet that is as wide and contoured as possible permits a reduced pressure gradient across the cuff thereby reducing the required tourniquet pressure for arterial occlusion.1,17 Additionally, selecting a tourniquet with overlap length that minimizes fluctuations in pressure perioperatively is optimal, though no statistical justification for a measurement range has been identified.
Shape. For this tapered shape in the lower extremity, contoured tourniquet cuffs are ideal as they afford lower occlusion pressures when compared to straight cuffs of equal width.14,18,19 On average, a pressure reduction of 20 mmHg can take place with a wide, contoured cuff versus a standard width cylindrical cuff.19
One may attribute this reduction in limb occlusion pressure to the increased surface contact area via better fit, creating more equal distribution of pressure from center to distal tourniquet edges once inflated. Contoured tourniquets may also have the additional benefit of decreased displacement once inflated, theoretically reducing distraction during operative time and keeping the surgical field consistently visually optimized.
Width. There is an inverse relationship in the lower extremity between occlusion pressure and tourniquet width, denoting that the greater the tourniquet width, the lower the tourniquet pressure needed for arterial occlusion. Conversely, a narrower tourniquet width requires higher tourniquet pressures for appropriate arterial occlusion.3,17-23
One can attribute this inverse relationship to the increased efficiency in pressure transmission to deeper tissues when applied through a greater surface area (i.e. a wider cuff).21 When limited to the arterial occlusive pressure of a tourniquet, wider tourniquets have the additional benefit of increased duration tolerance and decreased perceived tourniquet pain.23 With respect to decreased limb occlusion pressure (LOP), studies comparing widths ranging from four to 10 cm as ‘narrow’ note a superiority of ‘wide’ cuffs ranging from 12 to 18 cm.3,17,18,20-23
Length. There is no standard guideline for cuff length. This should ideally be a flexible measurement based on each patient case; however there are suggestions of cuff length overlap in literature. Unclear as to the origin for the justification for this measurement range, Derner and Buckholtz in 1991 recommended that tourniquet cuff length should overlap six to eight inches in order to produce a more accurate tourniquet gauge perioperatively.15 More recently, various literature has quoted an ideal overlap between seven and 15 cm.12,14,16
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