 |
 |
 |
|
| home | CME | help | feedback | subscriptions | archive |
|
© 1997 The Journal of Bone and Joint Surgery, Inc. The Effect of Local Infiltration with Morphine before Carpal Tunnel Release*  , HAIFA, ISRAELInvestigation performed at the Rambam Medical Center, Haifa
We compared the effect of infiltration with a mixture of 1 per cent lidocaine and two milligrams of morphine in twenty-five patients who were to be managed with a carpal tunnel release with the effect of infiltration with 1 per cent lidocaine only in a second group of twenty-five patients who were to have such a release. In both groups, the injection was administered after inflation of the tourniquet. During the procedure, the patients' movement and vocalization of discomfort did not differ substantially between the groups. However, in the immediate postoperative period, the patients who had received morphine indicated a significantly higher score (on a visual-analog scale) for peak intraoperative pain than did the patients who had received lidocaine only (2.44 ± 1.73 points compared with 1.32 ± 1.22 points; p = 0.01). The numbers of patients who had pain in the recovery room, the numbers of patients who received analgesics in the recovery room, and the scores for pain at the time of discharge were similar for the two groups. The score for pain on the first postoperative day was more than 4 points for seven patients who had received morphine, whereas no patient who had received lidocaine only had a score of more than 4 points (p = 0.01); however, the amount of analgesics taken at home was similar for the two groups. Postoperative complications, which included hypotension, fainting, weakness, and chest pain, occurred in eight patients (32 per cent) who had received morphine and in none who had received lidocaine only (p < 0.01).
Opioid agonists have an effect on the peripheral receptors of sensory nerves2,5,12 in addition to their central action on opioid receptors in the brain and the spinal cord10,11. The immune cells in injured tissues produce endogenous opioid peptides that act at these opiate-receptor sites on the peripheral sensory nerves and inhibit nociception7,13 and peripheral substance-P release16. We studied the clinical usefulness of peripherally administered opiates for providing analgesia for patients who were managed with a carpal tunnel release.
Fifty patients who were to be managed with a carpal tunnel release were included in a randomized double-blind study. The protocol for the study was approved by the institutional Human Studies Committee, and informed consent was given by each patient. The carpal tunnel release was recommended for patients who had positive findings on electrodiagnostic studies and for whom non-operative treatment with a splint and local injection of steroids had failed. Patients were excluded if they had a history of a coagulation disorder, an allergy to local anesthetics or morphine, a history of abuse of drugs (including sedatives or narcotics), autoimmune disease, or Raynaud disease. The patients were assigned to receive a mixture of morphine and lidocaine or lidocaine only, according to a predetermined randomization schedule. None of the patients were given any premedication or intravenously administered sedatives. All of the operations were performed in the hospital by the same one of us (S. S.) with the same operative technique. The patients were monitored throughout the procedure with automated recording of blood pressure, continuous electrocardiography, and pulse oximetry readings. After inflation of the tourniquet, six milliliters of a liquid containing 1 per cent lidocaine and two milligrams of morphine or six milliliters of 1 per cent lidocaine only was injected locally; the surgeon was blinded with regard to the contents of the syringe. Additional injections of 1 per cent lidocaine were given intraoperatively at the discretion of the surgeon. At the conclusion of the procedure, the surgeon graded the intraoperative vocalization and movement of the patient. According to the vocalization scale, a score of 0 points was given when the patient had been quiet; 1 point, when the patient had complained of pain or had moaned; and 2 points, when the patient had shouted, screamed, or cried. The movement of the patient was graded as 0 points when the patient had not moved; 1 point, when the patient's movement had stopped after the surgeon had provided an explanation; and 2 points, when the patient's movement had necessitated additional injection of a local anesthetic. In the recovery room, in which the patients were observed for one to two hours before they were discharged (if there were no complications), the patients were asked to grade the peak (most severe) intraoperative pain on a ten-centimeter visual-analog scale on which zero indicated no pain and ten, unbearable pain. Paracetamol (500 milligrams) was given orally to patients who had pain. Two hours after the operation, or just before discharge if the patient was to leave sooner, the patients were asked if they had had pain in the recovery room and were instructed to grade it on the visual-analog scale. In addition, the need for analgesics and any complications that occurred in the recovery room were recorded. The patients were discharged with written instructions and were advised to take paracetamol tablets as needed for control of pain. The patients were asked to grade the pain on the visual-analog scale and to document the use of any analgesics on the first postoperative day. The demographic data for the groups were evaluated with use of chi-square analysis (for gender) and analysis of variance (for weight and age). The relevant-sized frequency-table analysis or a chi-square analysis of contingency table and the Fisher exact test were used for comparison of categorical data such as the scores for intraoperative movement and vocalization as well as the presence of pain and the need for analgesics in the recovery room. The non-parametric Mann-Whitney test was used to evaluate the scores for pain in the recovery room and on the first postoperative day. The score for pain on the first postoperative day was also assessed by dividing the patients into two groups—those who had a score of 4 points or less and those who had a score of more than 4 points—and comparing the data with chi-square analysis. The use of analgesics at home was analyzed with use of the Fisher least-significant-difference procedure for post hoc testing. The results were significant if p < 0.05.
The mean age (and standard deviation) was 49 ± 11.9 years for the twenty-five patients who received morphine and 50 ± 10.4 years for the twenty-five patients who received lidocaine only. There were eight men and seventeen women in each group. There was no substantial difference between the two groups with regard to the scores for intraoperative movement: the score was 0 points (no movement) for twenty patients who had morphine and for twenty-two who had lidocaine only. The scores for vocalization also were the same for the two groups, with a score of 0 points (quiet) for seventeen patients and a score of 1 point (indicating mild-to-moderate discomfort) in eight patients in both groups (Table I). However, the patients who had received morphine graded the peak intraoperative pain significantly higher (p = 0.01) than did the patients who had received lidocaine only (2.44 ± 1.73 compared with 1.32 ± 1.22 points). There was no substantial difference between the two groups with regard to the number of patients who had pain in the recovery room (ten patients who had had morphine compared with nine who had had lidocaine only) or with regard to the number of patients who received analgesics in the recovery room (eight patients compared with four) (Table I). The scores for pain at the time of discharge were similar for the two groups (2.36 ± 1.22 points for those who had received morphine compared with 2.20 ± 0.82 points for those who had received lidocaine only), but the scores differed on the first postoperative day. This difference was not significant (p = 0.09) when analyzed with the non-parametric Mann-Whitney test; however, it was significant (p = 0.01) when the patients were grouped according to the score for pain (4 points or less and more than 4 points): eighteen patients who had received morphine had a score of 4 points or less and seven had a score of more than 4 points, whereas all twenty-five patients who had received lidocaine only had a score of 4 points or less. The use of analgesics at home was the same for the two groups (ten patients in each).
The two groups did not differ substantially with regard to the number of intraoperative complications or the number of patients who needed additional injections of lidocaine intraoperatively. A surprising finding was the significantly higher rate of postoperative complications (p < 0.01) for the patients who had received morphine (32 per cent; eight patients) compared with that for the patients who had received lidocaine only (0 per cent). The mean age of the eight patients who had complications was 64.4 years, and the complications included fainting, hypotension, and weakness; two patients also had chest pain, which resolved. Additional fluids were administered intravenously to these eight patients, and they stayed in the recovery room for four to twenty-four hours.
Morphine is known to cause the release of histamine, and the systemic effects of this release have been studied previously3,6. Histamine is a powerful activator of nociceptors in the local tissues, leading to substance-P release1. Histamine and substance P produce vasodilation and increased vascular permeability, which lead to the release of bradykinin1. Substance P promotes additional release of histamine from mast cells and serotonin from platelets1. The increased concentration of morphine in the tissues results in a high local concentration of histamine, which, in turn, sets off a cascade of chemical and physiological changes that prime the tissues for pain, leading to peripheral hyperalgesia. Raja et al. found higher scores for pain and an increased use of analgesics in the early postoperative period for their patients who had received morphine intra-articularly; they suggested that these findings were secondary to the local release of histamine caused by morphine. The irony of the results of the study by Raja et al. and of the current study is that the purpose of the local injection of morphine was to lessen the local hypersensitivity of the so-called secondary phase of the tissue injury response1,14,15. Histamine, however, is one of the principal chemical mediators of this peripheral hypersensitivity injury response. The indirect increase in its local concentration may therefore have had the opposite of the desired effect. This may provide an explanation for the increased intraoperative pain in the patients who had received morphine. The absence of any differences between the groups with regard to pain during the early postoperative period suggests that the concentration of morphine had decreased, thereby eliminating the local effects. We are unable to explain why the patients who had received morphine had increased pain on the first postoperative day. When morphine is injected into highly vascular tissue, it may be readily washed out, leaving only a systemic effect, and local histamine-induced vasodilation only accelerates this washout. The difference in the local conditions may explain why the prolonged analgesic effect of an opiate administered intra-articularly cannot be duplicated in other tissues9. Our protocol allowed direct infiltration with morphine in and about the incision, with placement of the tourniquet proximal to the operative site. The tourniquet prevented rapid washout from the tissues and systemic effects as confounding factors, and it also provided time for the morphine to be absorbed. It is known that the inflammatory response is necessary to obtain peripheral analgesia with an opiate4,7,12. Therefore, the failure to demonstrate an analgesic benefit after local infiltration with morphine may be due to a clinical model that simply does not generate an adequate inflammatory response to demonstrate the phenomenon. Alternatively, the high local concentration of morphine may have been dissipated before the creation of an adequate number of the functionally coupled receptors. The high rate of postoperative complications associated with the use of morphine was unexpected. Although two milligrams of morphine is a relatively small dose, it appears to have been sufficient to act systemically, sometimes resulting in weakness, hypotension, and fainting, and thus a delayed discharge from the hospital. The mean age of the patients in whom complications occurred was sixty-four years, compared with an over-all mean age of fifty years; therefore, the complications may represent a more fragile hemodynamic status of older patients. Our study showed no analgesic benefit of local infiltration with morphine before carpal tunnel release. Indeed, the use of morphine was associated with increased pain intraoperatively and one day postoperatively as well as with a high prevalence of postoperative complications.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
  CiteULike  Connotea  Del.icio.us  Facebook  Technorati  Twitter What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Top
Abstract
Introduction| home | CME | help | feedback | subscriptions | archive | site index |
|
Stanford University Libraries' HighWire Press (TM) assists in the publication of JBJS Online. |