Pre-emptive analgesia: an unsolved problem

Effect of wound infiltration with ropivacaine or bupivacaine analgesia in breast cancer surgery: A meta-analysis of randomized controlled trials

BACKGROUND

Although not completely painless, breast-conserving surgery is considerably less painful than modified radical mastectomy. Local anesthetics are speculated to reduce postoperative pain when placed at the surgical site. Thus, we conducted a systematic review of randomized controlled trials to evaluate the efficacy of bupivacaine or ropivacaine analgesia for pain relief in breast cancer surgery.

METHODS

PubMed, Embase, the Cochrane Library, Scopus, and the ClinicalTrials.gov registry were searched for studies published up to July 2015. Individual effect sizes were standardized, and a meta-analysis was performed to calculate a pooled effect size by using random effects models. Pain was assessed using a visual analog scale at 1, 2, 12, and 24 h postoperatively. The secondary outcomes included complications and analgesic consumption.

RESULTS

We reviewed 13 trials with 1150 patients. We found no difference in postoperative pain reduction at 1, 12, and 24 h after breast cancer surgery between the experimental and control groups. The severity of pain was significantly reduced in the experimental group (weighted mean difference -0.19; 95% confidence interval: -0.39-0.00) at 2 h postoperatively. Moreover, postoperative analgesic consumption did not differ significantly between the groups. No major drug-related complication was observed in any study.

CONCLUSION

Administration of the local anesthetics bupivacaine or ropivacaine during breast cancer surgery decreased pain significantly at only 2 h but did not reduce pain at 12, and 24 h postoperatively.

Evaluation of the effects of methadone and tramadol on postoperative analgesia and serum interleukin-6 in dogs undergoing orthopaedic surgery

BACKGROUND

Acute postsurgical pain is of great interest due to potential risk of becoming chronic if not treated properly, worsening patient's recovery and quality of life. Twenty-eight dogs with ruptured cruciate ligaments were divided into three groups that received intramuscular injections of 4 mg/kg of tramadol (TRA), 0.5 mg/kg of methadone (MET0.5), or 0.7 mg/kg of methadone (MET0.7). Physiological parameters (heart and respiratory rates and blood pressure) were evaluated at specified times: baseline (TBL), 1 (T1), 2 (T2), 4 (T4), 6 (T6), and 24 (T24) hours after premedication. Pain scores were described by visual analogue scale (VAS), modified Glasgow Composite, and Colorado University Acute Pain scales. Blood samples for measurement of interleukin (IL)-6 were collected at TBL, T1, T6, and T24. This was a prospective, randomised investigation to evaluate the efficacy of tramadol and methadone as premedications in dogs undergoing osteotomies.

RESULTS

There were no statistically significant differences between groups with respect to age, weight, gender, surgery time, and time to extubation. Heart rate, respiratory rate, and blood pressure values were maintained within acceptable ranges, and a reduction was observed at T2 in MET0.5 and MET0.7 compared with TBL. Increases in VAS scores were observed in TRA at T4 compared with TBL, T1, and T24 and between T1 and T6 (p < 0.001). In MET0.5, there was significant increase in VAS score at T4 compared with T1 (p < 0.001). TRA and MET0.5 showed significantly higher mean ± SD VAS scores (3.4 ± 2.5 and 2.5 ± 2.6, respectively) than MET0.7 (1.1 ± 1.5) at T4 (p < 0.001). TRA showed greater demand of rescue analgesia (four animals in T4 and two in T6) (p < 0.037). There were no statistically significant differences in sedation scores, Colorado Scale scores, or interleukin levels between groups and time points.

CONCLUSIONS

Methadone given as premedication in doses of 0.7 mg/kg was better at controlling pain compared with lower doses and tramadol. However, dosage increases, administered as rescue analgesia, promoted adequate pain control even in tramadol group. Influence of these analgesics on IL-6 release could not be demonstrated, but significant levels were not found.

Pathological sprouting of adult nociceptors in chronic prostate cancer-induced bone pain

Pain frequently accompanies cancer. What remains unclear is why this pain frequently becomes more severe and difficult to control with disease progression. Here we test the hypothesis that with disease progression, sensory nerve fibers that innervate the tumor-bearing tissue undergo a pathological sprouting and reorganization, which in other nonmalignant pathologies has been shown to generate and maintain chronic pain. Injection of canine prostate cancer cells into mouse bone induces a remarkable sprouting of calcitonin gene-related peptide (CGRP(+)) and neurofilament 200 kDa (NF200(+)) sensory nerve fibers. Nearly all sensory nerve fibers that undergo sprouting also coexpress tropomyosin receptor kinase A (TrkA(+)). This ectopic sprouting occurs in sensory nerve fibers that are in close proximity to colonies of prostate cancer cells, tumor-associated stromal cells and newly formed woven bone, which together form sclerotic lesions that closely mirror the osteoblastic bone lesions induced by metastatic prostate tumors in humans. Preventive treatment with an antibody that sequesters nerve growth factor (NGF), administered when the pain and bone remodeling were first observed, blocks this ectopic sprouting and attenuates cancer pain. Interestingly, reverse transcription PCR analysis indicated that the prostate cancer cells themselves do not express detectable levels of mRNA coding for NGF. This suggests that the tumor-associated stromal cells express and release NGF, which drives the pathological reorganization of nearby TrkA(+) sensory nerve fibers. Therapies that prevent this reorganization of sensory nerve fibers may provide insight into the evolving mechanisms that drive cancer pain and lead to more effective control of this chronic pain state.

Blockade of nerve sprouting and neuroma formation markedly attenuates the development of late stage cancer pain

For many patients, pain is the first sign of cancer and, while pain can be present at any time, the frequency and intensity of pain tend to increase with advancing stages of the disease. Thus, between 75 and 90% of patients with metastatic or advanced-stage cancer will experience significant cancer-induced pain. One major unanswered question is why cancer pain increases and frequently becomes more difficult to fully control with disease progression. To gain insight into this question we used a mouse model of bone cancer pain to demonstrate that as tumor growth progresses within bone, tropomyosin receptor kinase A (TrkA)-expressing sensory and sympathetic nerve fibers undergo profuse sprouting and form neuroma-like structures. To address what is driving the pathological nerve reorganization we administered an antibody to nerve growth factor (anti-NGF). Early sustained administration of anti-NGF, whose cognate receptor is TrkA, blocks the pathological sprouting of sensory and sympathetic nerve fibers, the formation of neuroma-like structures, and inhibits the development of cancer pain. These results suggest that cancer cells and their associated stromal cells release nerve growth factor (NGF), which induces a pathological remodeling of sensory and sympathetic nerve fibers. This pathological remodeling of the peripheral nervous system then participates in driving cancer pain. Similar to therapies that target the cancer itself, the data presented here suggest that, the earlier therapies blocking this pathological nerve remodeling are initiated, the more effective the control of cancer pain.

Preemptive Ropivacaine Local Anaesthetic Infiltration Versus Postoperative Ropivacaine Wound Infiltration in Mastectomy: Postoperative Pain and Drain Outputs

OBJECTIVE

The aim of this study was to investigate if preemptive local infiltration (PLA) with ropivacaine could improve postoperative pain and determine its effect on drain output postmastectomy with axillary dissection.

METHODS

This was a prospective, randomized trial comprising 30 women allocated to two groups: one to receive postoperative wound infiltration (POW) of 20 mL of 0.2% (40 mg) ropivacaine (Naropin) versus PLA with 20 mL of 0.2% ropivacaine (Naropin) diluted with 80 mL of 0.9% saline, total volume 100 mL. A visual analogue scale (0-100 mm) and angle of shoulder abduction were used for evaluation of pain. Postoperatively, all patients received oral ibuprofen 400 mg tds.

RESULTS

There was no significant difference in postoperative pain for the first 3 days between the two groups. There were wider shoulder abduction angles in the 1st and 3rd postoperative days in the PLA group, but this was not significant. Operative time was significantly shorter in the PLA group than in the POW group (69.34+/-59.37 minutes vs. 109.67+/-26.96 minutes; p=0.02). The axillary drain was removed earlier in the preemptive group, 5.4+/-1.55 days versus 6.8+/-2.04 days in the postoperative group (p=0.04).

CONCLUSION

We found no difference in postoperative pain between preemptive tumescent ropivacaine infiltration and postoperative ropivacaine wound infiltration.

Can antiemetics really relieve pain?

The analgesic properties of 2 antiemetic agents--metoclopramide and ondansetron--were investigated in studies which showed that metoclopramide may decrease postoperative opioid requirements, but the analgesic effect of ondansetron is controversial. The postoperative effects of metoclopramide and ondansetron on pain in patients undergoing laminectomy were evaluated. Forty six patients were randomized into 3 groups: group M, which consisted of 15 patients who received intravenous (IV) metoclopramide 0.5 mg 30 minutes before surgery; group O, which consisted of 16 patients who received ondansetron IV 0.1 mg 30 minutes before surgery; and group C, which consisted of 15 patients who received the same volume of saline IV 30 minutes before surgery. The efficacy and duration of analgesia were assessed using a visual analogue scale (VAS) at 0, 0.5, 1, 3, 6, and 24 hours after surgery. Hemodynamic parameters, additional analgesic requirements, and adverse effects were recorded for the study groups. Diclofenac 75 mg was administered intramuscularly as a rescue analgesic during the postoperative period. VAS scores were lower in the metoclopramide group than in the ondansetron and control groups (P<.05, each). The patients in the ondansetron and control groups required much more diclofenac than the patients in the metoclopramide group (P<.05). Metoclopramide administered preoperatively provided postoperative analgesia in patients undergoing elective laminectomy.