Dose effects of morphine and butorphanol alone and in combination after burn injury in the rat

Butorphanol in combination with dexmedetomidine provides efficient pain management in adult burn patients

OBJECTIVE

This study aimed to compare the sedation and analgesic effects of butorphanol alone and butorphanol in combination with dexmedetomidine on dressing changes in adult burn patients.

METHOD

From June 2016 to May 2019, 44 adult burn patients from our department were enrolled in this prospective, double-blinded study. Their total burn surface area (TBSA) varied from 10% to 30%; and the depth of burn injury ranged from second degree to third degree. The patients were randomized into two groups. In the control group, butorphanol combined with saline was injected into the body via venous route during dressing change. In the observation group, butorphanol in combination with dexmedetomidine was injected. The variation in mean blood pressure, heart rate, respiratory rate, and peripheral oxygen saturation were recorded at various time-points of the procedure. Visual Analogue Scale (VAS) of pain and Ramsay Sedation Scores (RSS) were also recorded at different time points. Consumption of butorphanol and adverse events in these two groups were compared.

RESULTS

The mean blood pressure and heart rate were significantly decreased in the observation group before butorphanol injection (P < 0.05) and before the dressing change (P < 0.05). The respiratory rates and peripheral oxygen saturation of these two groups showed no significant differences at all time points (P > 0.05). Patients in the observation group had lower VAS scores during dressing change (P < 0.05). The RSS Scores in the observation group were higher than those in the control group during (P < 0.05) and after the dressing change (P < 0.05). The consumption of butorphanol was more in the control group (P < 0.05), and the adverse events recorded in the control group were higher (P < 0.05).

CONCLUSION

Butorphanol combined with dexmedetomidine can reduce analgesic use of butorphanol during dressing change. This combination resulted in a higher sedation score and fewer adverse effects.

Haemodynamic changes and stress responses of piglets to surgery during total intravenous anaesthesia with propofol and fentanyl

The purpose of the study was to assess the haemodynamic (blood pressure and heart rate) changes and stress responses (serum cortisol and serum amyloid A [SAA] concentrations) to surgery in piglets during total intravenous anaesthesia (TIVA) with propofol and fentanyl. After preanaesthetic medication with intramuscular midazolam (0.5 mg/kg body mass), ketamine (10 mg/kg) and butorphanol (0.5 mg/kg) anaesthesia was induced in five piglets, with intravenous propofol (1 mg/kg) followed by tracheal intubation and mechanical lung ventilation. Soft tissue surgery was performed in the jugular and inguinal regions during TIVA with propofol (8 mg/kg/h) and fentanyl (35 μg/kg/h). Anaesthesia was maintained for 300 min after surgery as the piglets were the control group of a project involving extracorporeal membrane oxygenation. Mean plasma cortisol concentration decreased significantly ( P < 0.05) from 59 ± 39.9 nmol/L (mean ± 1 SD) before surgery to 7.5 ± 2.5 nmol/L 300 min after end of surgical procedure. The mean SAA concentrations increased over the same period from 1.6 ± 2.3 μg/mL to 4.2 ± 5.6 μg/mL without statistical significance. The baseline (presurgery) mean arterial pressure (MAP) was 72 ± 9 mmHg compared with 72 ± 11 mmHg 300 min after end of surgery. Neither heart rate nor lactate concentrations changed significantly over the same time points: heart rate was 104 ± 11 and 103 ± 15 beats/min whereas mean lactate concentrations were reduced from 1.14 ± 0.45 mmol/L to 0.90 ± 0.22 mmol/L. Haemodynamic stability, a decrease in serum cortisol and a non-statistically significant rise in mean SAA concentrations suggest that the anaesthetic described suppresses the stress response of piglets to surgery without adverse cardiovascular effects. Therefore, it may prove useful in cardiovascular research.

Activation of peripheral cannabinoid receptors attenuates cutaneous hyperalgesia produced by a heat injury

Accumulating evidence suggests that cannabinoids can produce antinociception through peripheral mechanisms. In the present study, we determined whether cannabinoids attenuated existing hyperalgesia produced by a mild heat injury to the glabrous hindpaw and whether the antihyperalgesia was receptor-mediated. Anesthetized rats received a mild heat injury (55 degrees C for 30 s) to one hindpaw. Fifteen minutes after injury, animals exhibited hyperalgesia as evidenced by lowered withdrawal latency to radiant heat and increased withdrawal frequency to a von Frey monofilament (200 mN force) delivered to the injured hindpaw. Separate groups of animals were then treated with an intraplantar (i.pl.) injection of vehicle or the cannabinoid receptor agonist WIN 55,212-2 at doses of 1, 10, or 30 microg in 100 microl. WIN 55,212-2 attenuated both heat and mechanical hyperalgesia dose-dependently. The inactive enantiomer WIN 55,212-3 did not alter mechanical or heat hyperalgesia, suggesting the effects of WIN 55,212-2 were receptor-mediated. The CB1 receptor antagonist AM 251 (30 microg) co-injected with WIN 55,212-2 (30 microg) attenuated the antihyperalgesic effects of WIN 55,212-2. The CB2 receptor antagonist AM 630 (30 microg) co-injected with WIN 55,212-2 attenuated only the early antihyperalgesic effects of WIN 55,212-2. I.pl. injection of WIN 55,212-2 into the contralateral paw did not alter the heat-injury induced hyperalgesia, suggesting that the antihyperalgesia occurred through a peripheral mechanism. These data demonstrate that cannabinoids primarily activate peripheral CB1 receptors to attenuate hyperalgesia. Activation of this receptor in the periphery may attenuate pain without causing unwanted side effects mediated by central CB1 receptors.