Role of cryoanalgesia in the control of pain after thoracotomy.

Thoracotomy causes severe postoperative pain, which is difficult to manage since the use of systemic analgesics often causes respiratory depression. Cryoanalgesia of the intercostal nerves has been advocated as an effective means of local analgesia without serious side effects. A prospective randomised blind trial to investigate the efficacy of the technique was carried out. A total of 53 patients undergoing thoracotomy were allocated to either the trial or a control group. At thoracotomy the surgeon was informed of the patient's trial allocation. The trial group received one minute of direct cryotherapy to at least five intercostal nerves related to the incision. All patients received methadone via the lumbar epidural route in a dose calculated according to their weight. A linear analogue assessment of postoperative pain was made by the patients as soon as they were sufficiently awake. An independent record of all postoperative analgesia was kept. After discharge from hospital further assessments were made at least six weeks after operation. Statistical analysis of the scores of postoperative pain and analgesic consumption showed that there was no significant difference between the trial and the control group. There was, however, a suggestion of an increase in the long term morbidity, although these figures were not amenable to statistical analysis. Thus is has not been possible to demonstrate a role for cryoanalgesia in the control of post thoracotomy pain.