A patient after undergoing Thoracotomy complained of severe pain. He can be best managed by:
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a. Thoracotomy is one of the most painful surgical incisions currentlyused.
b. In treating the postoperative pain, the balancebetween adequate analgesia and potential side effects has beendifficult to achieve.
c. The pain is caused by the interactionof several factors including incisional pain, interruption ofmuscular and ligamentous structures by the retractor used duringthe surgical procedure and pain of pleural irritation secondaryto the presence of the chest tube.
d. Epidural analgesia is a commonly used form ofpost-thoracotomy pain control and although effective, oftennecessitates the use of urinary catheters and reduces postoperativemobility whilst the epidural is in situ.
e. Cryoanalgesia, localized freezing of the intercostal nerves,is able to offer both short- and longer-term analgesia. It isbased on the application of a cryoprobe, which employs the Joule–Thomsoneffect, whereby carbon dioxide or nitrous oxide is releasedat high pressure (4000–6000 kPa) and allowed to expandrapidly within the bulb of the cryoprobe.
f. This causes coolingof the probe tip to temperatures of approximately -50 to -70°C.When applied to peripheral nerves, localized freezing induceschanges consistent with a second-degree nerve lesion (axonotmesis).
g. The effects of cryoanalgesia are directly relatedto the formation of intra- and extracellular ice crystals, whichresult in microvascular changes and alteration of cellular osmolalityand permeability, causing cell damage and disruption of nerveconduction .