Position-Related Postoperative Peripheral Neuropathy After Laparoscopic Colorectal Surgery: A Comparative Single-Center Prospective Cohort Study.

Background: Laparoscopic colorectal surgery requires perioperative positioning in the dorsal lithotomy position and intermittent Trendelenburg position. This position is associated with postoperative peripheral neuropathy (PPN), which is a substantial cause of anesthesia-related claims. The objective of this study was to assess the incidence of PPN of patients positioned in lithotomy position with shoulder braces, and second to compare this group with patients positioned on the foam mattress Pink Pad®. Materials and Methods: This consecutive single-center prospective cohort study of 155 patients undergoing colorectal surgery was performed between November 2014 and June 2015. After initial results the implementation of the Pink Pad took place and a total of 52 patients were included between May 2016 and February 2017 to compare the two groups. Results: Positioning with the shoulder brace regimen during laparoscopic colorectal surgery was related to the development of PPN in 33% of cases, as opposed to 15% with Pink Pad. Positioning with shoulder braces increased the risk of PPN with an odds ratio of 3.14 (95% confidence interval: 1.10-8.992) when compared with positioning on Pink Pad. Conclusion: Position-related PPN is an important complication after laparoscopic colorectal surgery. This study concludes that careful attention should be paid to positioning and favors Pink Pad over positioning with shoulder braces. Prolonged time in anesthesia is a predictor of PPN. Clinical Trial Number: H-2-2014-FSP75.

Pain and sensory dysfunction 6 to 12 months after inguinal herniotomy.

Inguinal hernia repair is associated with a 5%-30% incidence of chronic pain, but the pathogenesis remains unknown. We therefore evaluated pain and sensory dysfunction by quantitative sensory testing 6-12 mo after open hemiorrhaphy. Before sensory testing, all patients (n = 72) completed a short-form McGill Pain Questionnaire and a functional impairment questionnaire. Sensory dysfunction in the incisional area was evaluated by quantification of thermal and mechanical thresholds, by mechanical pain responses (von Frey/pressure algometry), and by areas of pinprick hypoesthesia and tactile allodynia. The incidence of chronic pain was 28% (20 of 72). Quantitative sensory testing and pressure algometry did not demonstrate differences between the pain and nonpain groups, except for a small but significant increase in pain response to von Frey hair and brush stimulation in the pain group. Hypoesthesia, or tactile allodynia, in the incisional area was observed in 51% (37 of 72) of the patients, but the incidence did not differ significantly between the pain group and the nonpain group (14 of 20 versus 23 of 52; P > 0.3). We concluded that cutaneous hypoesthesia, or tactile allodynia, is common after inguinal hemiotomy but has a low specificity for chronic postherniotomy pain. Factors other than nerve damage may be involved in the development of chronic posthemiotomy pain.

Arthroscopic knee surgery does not modify hyperalgesic responses to heat injury.

BACKGROUND: Experimental studies suggest that surgical injury may up- or down-regulate nociceptive function. Therefore, the aim of this clinical study was to evaluate the effect of elective arthroscopically assisted knee surgery on nociceptive responses to a heat injury. METHODS: Seventeen patients scheduled to undergo repair of the anterior cruciate ligament and 16 healthy controls were studied. The first burn injury was induced 6 days before surgery, and the second burn was induced 1 day after surgery with a contact thermode (12.5 cm2, 47 degrees C for 7 min) placed on the medial aspect of the calf contralateral to the surgical side. Ibuprofen and acetaminophen were given for 2 days before the first burn injury and again from the time of surgery. In the controls, the two burn injuries were separated by 7 days. Sensory variables included cumulated pain score during induction of the burn (visual analog scale), secondary hyperalgesia area, and mechanical and thermal pain perception and pain thresholds assessed before and 1 h after the burn injury. RESULTS: The heat injuries induced significant increases in pain perception (P < 0.001) and decreases in pain thresholds (P < 0.02). Baseline heat pain thresholds were higher during the second burn injury in patients (P < 0.001) and controls (P < 0.01). However, there were no significant differences in pain to heat injury (P > 0.8), secondary hyperalgesia areas (P > 0.1), mechanical and thermal pain perception (P > 0.1), or mechanical and thermal pain thresholds (P > 0.08) in the burn area before surgery compared to after surgery. CONCLUSION: Arthroscopic knee surgery did not modify nociceptive responses to a contralaterally applied experimental burn injury.

Local cooling does not prevent hyperalgesia following burn injury in humans.

One of the oldest methods of pain relief following a burn injury is local application of ice or cold water. Experimental data indicate that cooling may also reduce the severity of tissue injury and promote wound healing, but there are no controlled studies in humans evaluating the anti-inflammatory or anti-hyperalgesic potential of early cooling after thermal injury. Twenty-four healthy volunteers participated in this randomized, single-blinded study. Following baseline measurements, which included inflammatory variables (skin temperature, erythema index) and sensory variables (thermal and mechanical detection thresholds, thermal and mechanical pain responses, area of secondary hyperalgesia), first degree burn injuries were induced on both calves by contact thermodes (12.5 cm(2), 47 degrees C for 7 min). Eight minutes after the burn injury, contact thermodes (12.5 cm(2)) were again applied on the burns. One of the thermodes cooled the burn (8 degrees C for 30 min) whereas the other thermode was a non-active dummy on the control burn. Inflammatory and sensory variables were followed for 160 min after end of the cooling procedure. The burn injury induced significant increases in skin temperature (P<0.0005), erythema index (P<0.0001), thermal pain responses (P<0.0005), mechanical pain responses (P<0.005) and secondary hyperalgesia, and significant decreases in heat pain threshold (P<0.0005) and mechanical pain threshold (P<0.0005). There were no post-cooling effects on skin temperature (P>0.5), erythema (P>0.9), heat pain threshold (P>0.5), thermal or mechanical pain responses (P>0.5) or the development of secondary hyperalgesia (P>0.4) compared with the control burn. However, a significant, albeit transient, increase in cold detection threshold was observed on the cooled burn side (P<0.0001). In conclusion, cooling with 8 degrees C for 30 min following a first degree burn injury in humans does not attenuate inflammatory or hyperalgesic responses compared with a placebo-treated control burn.

Analgesic effects of dexamethasone in burn injury.

BACKGROUND AND OBJECTIVES: Glucocorticoids are well-known adjuvant analgesics in certain chronic pain states. There is, however, a paucity of data on their analgesic efficacy in acute pain. Therefore, the aim of the study was to examine the analgesic effects of dexamethasone in a validated burn model of acute inflammatory pain in humans. METHODS: Twenty-two volunteers were investigated in a double-blind, randomized, placebo-controlled cross-over study. Intravenous dexamethasone 8 mg or placebo was administered on 2 separate study days. Two hours after drug administration, a first-degree burn injury was produced on the medial aspect of the nondominant calf (12.5 cm2, 47 degrees C for 7 minutes). Quantitative sensory testing included pain ratings to thermal and mechanical stimuli (visual analog scale [VAS]), assessments of thermal and mechanical detection thresholds, and areas of allodynia and secondary hyperalgesia. RESULTS: The burn injury induced significant increases in erythema (P <.0001) and hyperalgesia (P <.001) in both groups. Pain ratings and development of tactile allodynia during the burn did not differ between dexamethasone and placebo treatments (P >.6). There were no significant differences between treatments in regard to skin erythema (P >.8), thermal or mechanical thresholds (P >.2), thermal or mechanical pain response (P >.2), or mechanical secondary hyperalgesia (P >.2). Dexamethasone had no analgesic effects in normal skin. CONCLUSIONS: The study indicates that systemic administration of dexamethasone 2 hours before a burn injury does not reduce the inflammatory-mediated changes in quantitative sensory thresholds, pain perception, or skin erythema in humans.