Chapter 74

### Introduction

Cryoanalgesia, that is, the use of low temperatures to provide analgesia, is a pain management technique that can be applied to a variety of painful situations. From the topical application of ice to a sprained ankle or cryoneurolysis of an intercostal nerve for postoperative pain control in a post-thoracotomy patient to cryoneurolysis of the trigeminal nerve for trigeminal neuralgia, cryoanalgesia has a multitude of uses. This chapter focuses on the application of cryoanalgesia for acute and chronic pain management.

### Historical Perspectives

The first account of the use of cryoanalgesia for pain control was recorded by Hippocrates (460–377 bc). He described the use of ice and snow packs to prevent pain from surgery.1 An 11th century Anglo-Saxon monk, Avicenna of Persia (980–1070), and Severino of Naples (1580–1656) also recognized the use of cold as preemptive analgesia for surgery.1,2 Other historical recorders who recognized the value of cryoanalgesia include Napoleon’s surgeon general, Baron Larre (1812), Dr James Arnott (1851), and Richardson (1866).1,2

Recently, Irvine Cooper and his colleagues (1961) developed the first prototype of a cryoprobe that could be used for analgesia.1,3 It utilized the principle of phase change using liquid nitrogen to produce a temperature of –196°C. Several years later in 1967, Amoils developed a smaller cryoprobe that employed the Joule-Thompson principle and used carbon dioxide or nitrous oxide to produce temperatures to –50°C.4) Present cryoprobes use either of these two principles to produce a temperature of at least –70°C.

Cryoneurolysis involves using cold to induce nerve injury, thus providing analgesia. The exact cellular mechanism of nerve injury is not known. Theories include ischemic necrosis, physical destruction by large cellular ice crystals, damage to proteins, minimal cell volume, production of autoantibodies, and membrane rupture caused by rapid water loss.5 Cryolesioning causes a second-degree nerve injury as classified by Sunderland. A second-degree injury involves degeneration of the axon and myelin sheaths (wallerian degeneration) from the site of freezing distally to the nerve’s termination.6 The minimum temperature required is 20°C or lower.5 The endoneurium, perineurium, and ectoneurium remain intact, thus regeneration is possible. The return of normal sensory and motor activity depends primarily on two factors: the rate of axonal regrowth (average of 1 to 2 mm per day) and the distance of the cryolesion from the end organ, although nerve conduction velocity remains only reduced to an average of 35 days.1,7,8

The success of a cryolesion depends on several factors: the rate of freezing and thawing, the temperature attained by the tissue in proximity to the cryoprobe, and the size of the cryolesion.7 Evans and Gill et al showed that repeat freeze-and-thaw cycles enlarged the size of the cryolesion, improving the success of the block.5,9 Freeze cycles are typically 1.5 to 3 minutes with ...

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