446 - Tourniquet-induced nerve compression injuries caused by high pressure levels and gradients

This progressively decreases tissue pH and pO2, and in- creases pCO2, K+, and lactate [19, 20]. Muscle is suscep- tible to these metabolic changes, and histological evidence of muscle damage is evident 30 – 60 min after tourniquet inflation [21]. These changes are generally mild and well tolerated. There is increased microvascu- lar permeability with reperfusion, resulting in swelling and tissue oedema, which in some patients can cause a “ post-tourniquet syndrome ” especially if inflation time has been prolonged. Post-tourniquet syndrome is characterized by a swollen, stiff, pale limb with weak- ness developing 1 – 6 weeks after the tourniquet appli- cation. High tourniquet pressure levels and applied pressure gradients combined with ischemia may in- duce more profound damage to muscle than ischemia alone [10, 19]. Tourniquet pressure gradients Reducing tourniquet pressure In order to ensure a bloodless field, the application of early-generation tourniquet devices applied unnecessar- ily high pressure levels to the underlying tissues, with corresponding high applied pressure gradients [2, 6]. Considerable evidence in early literature testifies to the common occurrence of nerve injuries after the use of these tourniquets [1, 2, 4, 6, 16, 22, 23]. Eckhoff (1931) analyzed the causes of tourniquet paralysis, with pleas to use more moderate and controlled applied pressure levels [4]. In a case study Moldaver (1954) described the subtle differences in clinical symptoms associated with tourniquet paralysis, concluding that nerve injury re- sulted from mechanical pressure localized to a very nar- row area [22]. Aho et al. (1983) reported a case of temporary paralysis induced by a pneumatic tourniquet, even though the pressure level was inflated to 250 mmHg for a duration of 75 min. While these parameters are typically considered safe, further investigation re- vealed the gauge was faulty resulting in application of a much higher than intended pressure level [16]. Several early papers reported that use of elastic bandages and faulty gauges in early, non-microprocessor controlled Fig. 1 Diagram illustrating the direction of displacement of the nodes of Ranvier due to pressure gradients near the edges of the cuff, i.e. from a high pressure region beneath the middle of the cuff to regions of lower pressure near the edges. (Republished with permission of John Wiley & Sons - Books., from Ochoa J, Fowler TJ, Gilliatt RW. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. J Anat 1972;113(Pt 3):433 – 55; permission conveyed through Copyright Clearance Center, Inc.) Table 1 Key Insights and Takeaways Key Insights Nerve Injuries • Transient and permanent nerve injuries can be associated with tourniquet use when not used appropriately. Pressure Levels and Gradients • High pressure gradients resulting from narrow cuffs and high applied pressures will cause injury • The lowest effective pressures should be applied, using wide cuffs that conform well to the limb shapes of individual patients Tourniquet Applications • For surgical applications, tourniquet pressure levels and tourniquet pressure gradients should be minimized to reduce tourniquet-induced nerve compression injuries. • For pre-hospital applications, there is a need for guidelines on safe tourniquet selection and pa- tient application, and on safe transfer of pa- tients to surgical settings. • For BFR applications, evidence arising from surgical tourniquet development, research and clinical studies should be used to reduce the potential for tourniquet-induced nerve com- pression injuries. FEBRUARY 2021 | The Surgical Technologist | 69