Pressure Tolerance Thresholds Research Articles

Oxycodone vs. fentanyl in the treatment of early post‐operative pain after laparoscopic cholecystectomy: a randomised double‐blind study

It has been suggested that oxycodone is superior to other opioids in the treatment of visceral pain. We therefore compared the effect of intravenous (i.v.) oxycodone and i.v. fentanyl on post-operative abdominal (visceral) pain after outpatient laparoscopic cholecystectomy. Seventy-eight patients were randomised to intra- and post-operative pain treatment with either oxycodone (n=39) or fentanyl (n=39). The patients received 10 mg oxycodone/100 microg fentanyl at the end of anaesthesia. In the post-anaesthetic care unit (PACU), 5 mg oxycodone/50 microg fentanyl was administered to patients with moderate pain [3-5 on a numeric rating scale (NRS)], and 10 mg oxycodone/100 microg fentanyl was administered to patients with severe pain (>5 on an NRS). The following measures were recorded: intensity of pain at arrival, after 30, 60 and 90 min and at discharge from the PACU; total consumption of oxycodone/fentanyl; nausea; vomiting; sedation and pressure tolerance thresholds. The median intra- and post-operative consumption of oxycodone was 15 mg (range: 10-40 mg) and the consumption of fentanyl was 200 microg (range: 100-500 microg). The intensity of abdominal pain was significantly lower in the oxycodone group at arrival (P<0.05), after 30, 60 and 90 min, and at discharge from the PACU (P<0.01). There was a strong tendency towards more side effects with oxycodone. Oxycodone provided better analgesia but also more side effects, suggesting that the doses used in the present study may not be equipotent.

MULTIDISCIPLINARY PAIN ABSTRACTS: 16 . Clinical Science (16)

The present double‐blind, placebo‐controlled study was designed to test quantitatively the effect and of nerve growth factor (NGF) injected into the masseter muscle. Pressure pain thresholds (PPT) and pressure tolerance thresholds (PTOL) were used as indices of mechanical allodynia and hyperalgesia in the jaw‐closing muscles. In addition, perceived pain intensity was assessed by the subjects on a 0 to 10 numerical rating scale (NRS) with the jaw at rest and in relation to various oral functions (chewing, yawning, talking, swallowing, drinking and smiling). Repeated measures analysis of variance (ANOVA) was used to test for significant effects. Injection of NGF into the masseter muscle was associated with significantly reduced PPT for 7 days and PTOL for 1 day. Buffered isotonic saline injections into the masseter muscle also significantly lowered the PPT after 1 day and isotonic saline had no significant effect on PTOL. In contrast, assessment of PPT and PTOL in the noninjected temporalis muscles demonstrated a significant increase after 14 to 28 days, which may have reflected an adaptation to the test procedure. NRS scores of chewing and yawning were significantly increased for 7 days following NGF injection. Systemic adverse effects were noted in one subject who reported fever and slight discomfort about 8 hours after the NGF injection. In conclusion, this is the first study to show that injection of NGF into the human masseter muscle causes local signs of mechanical allodynia and hyperalgesia that persist for at least 7 days as well as pain during strenuous jaw movement. The present pain model is safe and may be used to gain further insight into the neurobiological mechanisms of muscle pain and sensitization.

Injection of nerve growth factor into human masseter muscle evokes long-lasting mechanical allodynia and hyperalgesia

Nerve growth factor (NGF) is a neurotrophic protein with a pivotal role in development and maintenance of the nervous system on one side and inflammatory and neuropathic pain states on the other. NGF causes clear signs of behavioral hyperalgesia in animal models and following intradermal and systemic administration in humans. The present double-blinded, placebo-controlled study was designed to test quantitatively the effect and duration (1 h, 1, 7, 14, 21 and 28 days) of NGF (5 μg in 0.2 ml) injected into the masseter muscle. Pressure pain thresholds (PPT) and pressure tolerance thresholds (PTOL) were used as indices of mechanical allodynia and hyperalgesia in the jaw-closing muscles. In addition, perceived pain intensity was assessed by the subjects on a 0–10 numerical rating scale (NRS) with the jaw at rest and in relation to various oral functions (chewing, yawning, talking, swallowing, drinking and smiling). Repeated measures analysis of variance (ANOVA) was used to test for significant effects. Injection of NGF into the masseter muscle was associated with significantly reduced PPT for 7 days (ANOVA: P<0.001) and PTOL for 1 day ( P<0.001). Buffered isotonic saline injections into the masseter muscle also significantly lowered the PPT after 1 day but to a significantly smaller extent than the NGF injections ( P<0.001) and isotonic saline had no significant effects on PTOL. In contrast, assessment of PPT and PTOL in the non-injected temporalis muscles demonstrated a significant increase after 14–28 days ( P<0.001), which may have reflected an adaptation to the test procedure. NRS scores of chewing and yawning were significantly increased for 7 days following NGF injection ( P<0.001). Systemic adverse effects were noted in one subject who reported fever and slight discomfort about 8 h after the NGF injection. In conclusion, this is the first study to show that injection of NGF into the human masseter muscle causes local signs of mechanical allodynia and hyperalgesia that persist for at least 7 days as well as pain during strenuous jaw movement. The present pain model is safe and may be used to gain further insight into the neurobiological mechanisms of muscle pain and sensitization.