Postoperative respiratory effects of intravenous fentanyl compared to intravenous methadone in dogs following spinal surgery

Randomized clinical trial comparing outcomes after fentanyl or ketamine-dexmedetomidine analgesia in thoracolumbar spinal surgery in dogs

Background

Opioids are widely used for perioperative pain control in dogs undergoing spinal surgery, but alternatives may be required because data suggest that opioids exacerbate inflammation in the injured spinal cord and veterinary access to opioids may become more restricted in the future.

Objectives

To compare recovery of ambulation and other functions between spinal cord‐injured dogs receiving peri‐operative fentanyl and those receiving a ketamine‐dexmedetomidine combination.

Animals

A total of 102 client‐owned dogs undergoing decompressive surgery for thoracolumbar intervertebral disc herniation.

Methods

Randomized clinical trial. Dogs were randomized 1:1 to fentanyl or a ketamine‐dexmedetomidine combination for intra and postoperative analgesia. Primary outcome was time to recovery of ambulation; secondary outcomes were the postoperative Colorado Acute Pain Scale, the short‐form Glasgow Composite Measure Pain Scale, time to recovery of voluntary urination and time to unassisted eating.

Results

No difference was found in time to recovery of ambulation between groups (adjusted sub‐hazard ratio, 0.83; 95% confidence interval [CI], 0.55‐1.24; P = .36) or in pain scores (Colorado: χ² = 14.74; P = .32; Glasgow: χ² = 6.61; P = .76). Differences in time to recovery of eating and urination were small but favored ketamine‐dexmedetomidine (adjusted odds ratios, 3.31; 95% CI, 1.53‐7.16; P = .002 and 2.43; 95% CI, 1.00‐5.96; P = .05, respectively).

Conclusions and Clinical Importance

There was no evidence that, at the doses used, fentanyl impaired ambulatory outcome after surgery for thoracolumbar intervertebral disc herniation in dogs. Pain control appeared similar between groups. Secondary outcomes suggested minor benefits associated with ketamine‐dexmedetomidine. The ketamine‐dexmedetomidine combination appears to be a reasonable alternative to peri‐operative opioids.

Thoracolumbar retrolaminar block in seven dogs undergoing spinal surgery

Background

Thoracolumbar intervertebral disc extrusion is a common neurologic complaint in dogs and is associated with debilitating pain that requires careful analgesic management to avoid the transition to a chronic pain state. Recently, there has been an increased effort to incorporate regional anaesthetic techniques whenever possible, both for perioperative analgesia management and for prevention of chronic pain. A novel regional anaesthetic technique named retrolaminar block is a fascial plane block where the local anaesthetic is injected directly on top of the dorsal aspect of the vertebral lamina, in the fascial plane between the lamina and the epaxial muscles. The technique was recently described in humans and it is claimed to provide analgesia in patients undergoing thoracic and lumbar procedures. To the authors’ knowledge, the retrolaminar block has not been previously reported in live dogs.

Case presentation

Seven dogs presented to our hospital for suspected thoracolumbar intervertebral disc extrusion were anaesthetised using an anaesthetic premedication and induction protocol tailored for each individual animal. Once the suspected diagnosis was confirmed, all seven dogs were placed in sternal recumbency, and the target thoracolumbar vertebral spinous process was identified with palpation. A unilateral retrolaminar block was performed in all dogs with 2 mg/kg of 0.25% bupivacaine. Physiologic parameters, as well as responses to nociceptive stimuli, were monitored throughout the anaesthetic event.

Intraoperatively, one dog required a bolus of fentanyl to control nociceptive stimulation while the epaxial muscles were retracted. No further intraoperative rescue analgesia was required in any of the cases. The postoperative pain was assessed using the Short Form of Glasgow Composite Measure Pain Scale for dogs every four hours for the duration of the dogs’ hospitalization. The retrolaminar block reduced the intraoperative requirement for systemic opioids and other adjunct analgesic agents and all dogs were comfortable throughout their hospitalization and up until the time of their discharge.

Conclusions

This case report presents the performance of the retrolaminar block technique as part of multimodal analgesia management in seven dogs undergoing thoracolumbar spinal surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13620-022-00224-7.

Plasma concentration, cardiorespiratory and analgesic effects of ketamine-fentanyl infusion in dogs submitted to mastectomy

Background

The analgesic and cardiorespiratory effects of ketamine, fentanyl, or ketamine-fentanyl constant rate infusion (CRI) in dogs undergoing mastectomy were evaluated. Seventeen female dogs received CRI of ketamine (GK [n = 6]: bolus 0.5 mg/kg; CRI 20 µg/kg/min in intra- and postoperative periods], fentanyl (GF [n = 5]: bolus 20 µg/kg; intraoperative CRI 5 20 µg/kg/hour and postoperative CRI 2 20 µg/kg/hour), or combination of ketamine-fentanyl (GKF [n = 6]: aforementioned doses) for 8 h. Cardiorespiratory, blood gas analyses, plasma drug concentrations, sedation score (SS), Pain Scores were evaluated.

Results

The heart rate decreased in the GF and GKF (p < 0.04); the mean arterial pressure was lower in the GKF than in the GK at 35 min (p < 0.001). Maximum plasma concentrations were observed 5 min after bolus in the GK (2847.06 ± 2903.03 ng/mL) and GKF (2811.20 ± 1931.76 ng/mL). Plasma concentration in intraoperative period of ketamine was of > 100 ng/mL in 5/5 and 2/5 animals in the GKF and GK, respectively; and > 1.1 ng/mL of fentanyl in 4/5 and 3/5 in GKF and GF, respectively.

Conclusion

Ketamine with/without fentanyl provided analgesia without significant cardiorespiratory and guaranteed the minimal plasma levels with analgesic potential during the 8 h.

Indications, complications, and mortality rate following craniotomy or craniectomy in dogs and cats: 165 cases (1995-2016)

OBJECTIVE

To determine the most common indications for cranial surgery and identify risk factors associated with the occurrence of complications and death in the perioperative period following cranial surgery.

ANIMALS

150 dogs and 15 cats.

PROCEDURES

For this multi-institutional retrospective case series, medical records of dogs and cats that underwent cranial surgery at any of the 4 participating institutions between 1995 and 2016 were reviewed. Variables were evaluated included species, sex, age, neurolocalization, history of preoperative seizures, surgical approach, histological results, perioperative complications, and outcome. Logistic regression analysis was performed to assess for risk factors for complications.

RESULTS

The most common neurolocalization was the forebrain (110/165 [66.7%]), with 94 (57.0%) animals having had seizures preoperatively. The rostrotentorial (116/165 [70.3%]) and caudotentorial (32/165 [19.4%]) surgical approaches were most commonly reported. The most common indication was the treatment of meningioma (75/142 [52.8%]). Complications arose in 58 of the 165 (35.2%) cases within 24 hours and in 86 (52.1%) cases 1 to 10 days postoperatively. Perioperative complications included hypotension (38/165 [23.0%]) and anemia (27/165 [16.4%]). During the postoperative period, the most common complications were neurologic deficits, seizures, postoperative anemia, and aspiration pneumonia. The mortality rate with death or euthanasia perioperatively or ≤ 10 days postoperatively was 14.5% (24/165). Long-term complications occurred in 65 of the 165 (39.4%) animals, with seizures and neurologic deficits being the most common.

CLINICAL RELEVANCE

Cranial surgery was performed most commonly for the removal of neoplastic lesions in dogs and cats, and most complications were not life-threatening.

Use of acupuncture as adjuvant analgesic technique in dogs undergoing thoracolumbar hemilaminectomy

The aim of this study was to investigate the analgesic efficacy of a preoperative acupuncture treatment in 24 client-owned dogs undergoing thoracolumbar hemilaminectomy. Dogs were randomly assigned to either group A (Acupuncture) or group C (Control). Before skin incision, group A was treated with acupuncture, performed under general anaesthesia for 30 min. Rescue intraoperative fentanyl was administered following a 20% increase in cardiovascular parameters compared to baseline values, measured before incision. An observer masked to the treatment assessed pain, pre- and postoperatively, with the Glasgow (GCPS), the Colorado (CPS) pain scales and a Visual Analogue Scale (VAS); additionally, the mechanical thresholds (MT) were measured with the Electronic von Frey Anaesthesiometer (EVF) at four points located near the herniated disc. The groups were compared with respect to intraoperative cardiovascular and respiratory variables, rescue fentanyl administered in total and at different surgical events (first incision [FI], drilling [DR], disc removal [RE] and skin suturing [ST]), and pre- and postoperative pain scores and MT. Group A received less fentanyl than group C (P = 0.014); this difference was significant at FI P = 0.035) and RE (P = 0.004). The improvement in postoperative CPS score (P = 0.013), VAS score (P = 0.003) and MT (P = 0.001) compared to preoperative values was greater for group A than for group C, whereas the treatment assignment had no effect on postoperative changes in GCPS compared to baseline. Pre-operative acupuncture may help improving perioperative analgesia in dogs with intervertebral disc herniation undergoing thoracolumbar hemilaminectomy.

The effect of fluconazole on oral methadone in dogs

OBJECTIVE

To determine the effects of fluconazole on oral methadone pharmacokinetics and central effects mediated by opioid receptors in dogs.

STUDY DESIGN

Prospective, incomplete block.

ANIMALS

A total of 12 healthy Beagle dogs.

METHODS

Dogs were randomly allocated into two groups of six dogs. In total, four treatments (two treatments/group) were administered including: oral methadone (1 mg kg^-1); oral fluconazole (5 mg kg^-1) every 12 hours starting 24 hours prior to oral methadone (1 mg kg^-1); oral fluconazole (2.5 mg kg^-1) every 12 hours starting 24 hours prior to oral methadone (1 mg kg^-1); and oral fluconazole (5 mg kg^-1) every 24 hours starting 12 hours prior to oral methadone (1 mg kg^-1). At least 28 days were implemented as a washout period between fluconazole treatments. Rectal temperature (RT), heart rate (HR), respiratory rate (f_R), sedation scores and blood samples were obtained for 24 hours after methadone administration. Plasma drug concentrations were measured with liquid chromatography/mass spectrometry.

RESULTS

Significantly higher maximum plasma methadone concentration (mean, 25-46 ng mL^-1) occurred in all fluconazole-administered treatments than in methadone alone (1.5 ng mL^-1). The mean 12 hour methadone plasma concentration in fluconazole treatments was 11-20 ng mL^-1. Significantly decreased RT and variable sedation occurred in all fluconazole treatments, but no changes occurred with methadone alone. There were no differences in HR or f_R among treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Fluconazole significantly increases the extent and duration of oral methadone exposure in dogs resulting in significant central opioid effects.