Comparison of the effects of an opioid-free anesthetic protocol with two opioid-based protocols on the intraoperative cardiovascular response and postoperative pain in cats undergoing elective ovariohysterectomy: A prospective, randomized, blinded, clinical study

This study compared the cardiovascular response to surgery and postoperative pain between an opioid-free protocol and two opioid-based protocols in cats undergoing elective ovariohysterectomy. Cats were randomly allocated into three intramuscular premedication treatments: DEX (dexmedetomidine 7 µg/kg, n = 12), DEXMET (dexmedetomidine 7 µg/kg + methadone 0.3 mg/kg, n = 13) and DEXMOR (dexmedetomidine 7 µg/kg + morphine 0.3 mg/kg, n = 14). Preoperatively, all cats received meloxicam 0.1 mg/kg, subcutaneously. Anesthesia was induced with propofol and maintained with sevoflurane. Heart rate (HR) and systolic arterial pressure (SAP) were measured intraoperatively. Pain was assessed before premedication (Baseline) and postoperatively for 6 h using the Glasgow Composite Measure Pain Scale - Feline (CMPS-F) and Feline Grimace Scale (FGS). Rescue analgesia was given for CMPS-F scores ≥ 5. In all groups, HR and SAP increased intraoperatively, but tachycardia (HR > 200 beats/min) or hypertension (SAP > 180 mmHg) did not occur. Postoperative CMPS-F scores were lower in DEXMET than in DEX; FGS scores in DEX and DEXMOR were higher than in DEXMET. Rescue analgesia was administered to 50 %, 23 % and 29 % cats in groups DEX, DEXMET and DEXMOR, respectively (p > 0.05). The odds ratio (95 % confidence interval) of receiving postoperative rescue analgesia within 6 h for opioid-free versus opioid-based techniques was 2.86 (0.76-11.43). All protocols allowed surgery to be performed without an exacerbated cardiovascular response. Incorporating methadone or morphine in the protocol decreased the odds of requiring postoperative rescue analgesia.

Does perioperative electroacupuncture reduce postoperative pain in dogs undergoing ovariohysterectomy?

Introduction

This study aimed to investigate the analgesic efficacy of perioperative electroacupuncture in fifty-six healthy female dogs undergoing ovariohysterectomy as part of a catch-neuter-release project.

Materials and methods

Ten minutes after sedation with 20 μg/kg medetomidine combined with 0.3 mg/kg butorphanol intramuscularly, the dogs were randomly allocated into two groups and received either electroacupuncture (EA, n = 27) or sham acupuncture (C, n = 29) treatment for 10 min (after sedation until the end of the surgery) at 6 different acupuncture points LI-4 (Large intestine 4), LIV-3 (Liver 3), ST-36 (Stomach 36), SP-6 (Spleen 6) bilateral. After administration of 0.2 mg/kg meloxicam and anesthesia induction with 2 mg/kg ketamine intravenously, ovariohysterectomy was performed by the same experienced surgeon using a midline surgical approach in dorsal recumbency. Pain was evaluated by two blinded and independent anesthetists using the Short Form of the Multimodal Glasgow Composite Pain Scale (mCMPS-SF) before sedation (T0), and three (T3), six (T6), and 24 h (T24) after anesthesia induction.

Results

Postoperative pain scores did not differ significantly between the groups (p = 0.36), but increased significantly three (T3) (p = 0.001) and six (T6) (p = 0.001) hours after surgery compared to before sedation and 24 h postoperative in both groups. Three hours after surgery (T3), 89.4% and six hours postoperatively (T6), 71.4% of the dogs in both groups exceeded the analgesic intervention threshold of the mCMPS-SF, indicating the need for rescue analgesia.

Discussion

The results of the study indicate that perioperative electroacupuncture treatment did not improve postoperative pain in dogs undergoing ovariohysterectomy. Therefore, a 10-min electroacupuncture treatment may be insufficient to provide effective postoperative analgesia. The pain assessment in feral dogs was notably impacted by anxious behavior, which may have influenced the final outcome The pain threshold was exceeded in ¾ of the dogs in the early postoperative phase (T3, T6), suggesting that the widely used anesthesia protocol consisting of butorphanol, ketamine and medetomidine in combination with meloxicam may not provide long-lasting and sufficient pain relief.

Pain Management in Animals with Oncological Disease: Opioids as Influencers of Immune and Tumor Cellular Balance

Advancements in understanding pain physiopathology have historically challenged animals' absence of pain senses. Studies have demonstrated that animals have comparable neural pain pathways, suggesting that cats and dogs likely experience pain similarly to humans. Understanding brain circuits for effective pain control has been crucial to adjusting pain management to the patient's individual responses and current condition. The refinement of analgesic strategies is necessary to better cater to the patient's demands. Cancer pain management searches to ascertain analgesic protocols that enhance patient well-being by minimizing or abolishing pain and reducing its impact on the immune system and cancer cells. Due to their ability to reduce nerve sensitivity, opioids are the mainstay for managing moderate and severe acute pain; however, despite their association with tumor progression, specific opioid agents have immune-protective properties and are considered safe alternatives to analgesia for cancer patients.

Anesthetic and analgesic techniques used for cats undergoing ovariohysterectomies in general practice in the United States

OBJECTIVE

To better document anesthetic and analgesic protocols used by veterinarians in general practice within the United States (US) when performing elective ovariohysterectomy in cats.

STUDY DESIGN

Cross-sectional survey.

POPULATION

Veterinary practitioners in the US who are members of the Veterinary Information Network Inc. (VIN).

METHODS

An online anonymous survey was distributed to VIN members. The survey included questions pertaining to preanesthetic evaluation, premedication, induction, monitoring and maintenance protocols, and postoperative analgesia and sedation protocols when performing ovariohysterectomy in cats.

RESULTS

A total of 1324 veterinarians completed the survey. Respondents (number; %) reported performing preanesthetic laboratory tests [packed cell volume (256; 19.3%), complete blood cell count (893; 67.4%) and biochemistry panels (1101; 83.2%)] and preanesthetic examinations (1186; 89.6%) on the morning of surgery. The most frequently administered drugs for premedication were dexmedetomidine (353; 26.7%) and buprenorphine (424; 32.0%). The most frequently administered induction agent was propofol (451; 61.3%), and isoflurane (668; 50.4%) was the most common agent for maintenance of anesthesia. The majority of respondents reported placing intravenous catheters (885; 66.8%), administering crystalloid fluids (689; 52.0%) and providing heat support (1142; 86.3%). Participants reported using perioperative and postoperative analgesia including opioids (791; 59.7%), non-steroidal anti-inflammatory drugs (NSAIDs; 697; 52.6%) and NSAIDs dispensed for home use (665; 50.2%). Cats were commonly released home on the day of surgery (1150; 86.9%), and most participants reported contacting owners for follow-up within 1-2 days (989; 74.7%).

CONCLUSIONS AND CLINICAL RELEVANCE

Anesthetic protocols and management techniques for routine feline ovariohysterectomy differ widely among US veterinarians who are VIN members, and results from this study may be of use to evaluate anesthetic practices from this population of veterinarians.

Acute kidney injury in 18 cats after subcutaneous meloxicam and an update on non-steroidal anti-inflammatory drug usage in feline patients in Australia

OBJECTIVES

Acute kidney injury (AKI) is a well-known but poorly documented adverse effect of non-steroidal anti-inflammatory drugs (NSAIDs) in cats. We aimed to describe instances of NSAID-associated AKI in cats and survey Australian veterinarians on NSAID use in acute settings.

METHODS

Medical records of cats that developed an AKI subsequent to the administration of meloxicam were obtained by searching the databases of seven practices in Queensland, as well as by contemporaneously contacting select veterinary colleagues of the authors in both general and specialist small animal practice. An online questionnaire was created for the survey, and the URL distributed to Australian practitioners.

RESULTS

A total of 18 cases were retrieved, all of which received injectable meloxicam. The indication(s) for its use and the dosage prescribed were within the manufacturer's recommendations for Australian veterinarians. The majority of cases (13/18 cats) received the label dose of 0.3 mg/kg subcutaneously (SC) on the day of the procedure. In 12/18 cats, the injection was given in association with general anaesthesia or sedation. Fourteen cats survived to hospital discharge. Of 187 survey respondees, 89% routinely administered NSAIDs for surgery-related analgesia, with 98% prescribing meloxicam and 84% of these giving it SC. Ninety percent of respondees routinely administered NSAIDs for non-surgical-related analgesia, with 99% prescribing meloxicam and 35% of those giving it SC.

CONCLUSIONS AND RELEVANCE

We strongly recommend that practitioners avoid prescribing meloxicam SC in cats. This recommendation is emphatic in situations where concurrent dehydration and/or hypotension are possible.

Sedation quality of alfaxalone associated with butorphanol, methadone or pethidine in cats injected into the supraspinatus or the quadriceps muscle

OBJECTIVES

The aim of this study was to compare the quality of sedation with three different anaesthetic protocols (alfaxalone combined with butorphanol, methadone or pethidine) administered intramuscularly in cats, and to evaluate the influence of the injection site (between supraspinatus and quadriceps muscles) on the onset and quality of sedation.

METHODS

A total of 151 cats were selected for this study. Cats were sedated with alfaxalone (3 mg/kg) combined with either butorphanol (0.3 mg/kg; n = 50), methadone (0.3 mg/kg; n = 53) or pethidine (5 mg/kg; n = 48). The combination was injected intramuscularly into the supraspinatus (n = 79) or quadriceps muscle (n = 72). The data included a scoring system for the quality of sedation and physiological parameters, such as heart rate (HR), respiratory rate, body temperature and occurrence of mydriasis, monitored during the first 30 mins of anaesthesia.

RESULTS

The opioid associated with alfaxalone influenced the overall sedation score, the degree of myorelaxation, the occurrence of mydriasis and HR. The overall sedation score was poorer with butorphanol than with methadone (P = 0.008), and butorphanol induced a lower degree of myorelaxation than methadone (P = 0.013). The injection into the supraspinatus showed better qualitative results for sedation and a faster onset time (in about 3 mins) than that into the quadriceps (P <0.001). HR decreased from baseline (P <0.001) and over time (P <0.001), mainly in cats of the butorphanol-supraspinatus and pethidine-quadriceps groups (P = 0.004). The occurrence of mydriasis was lower after butorphanol than after methadone and pethidine (P = 0.025), while the incidence of side effects did not differ among groups.

CONCLUSIONS AND RELEVANCE

All three protocols provided a good quality of sedation and allowed performing the scheduled procedure. Moreover, the injection into the supraspinatus muscle showed superior results in all the qualitative scores of sedation and quicker onset time than that into the quadriceps muscle.

Randomised clinical trial comparing the perioperative analgesic efficacy of oral tramadol and intramuscular tramadol in cats

OBJECTIVES

The aim of this study was to evaluate the analgesic efficacy of oral tramadol in cats undergoing ovariohysterectomy.

METHODS

Twenty-four female domestic cats, American Society of Anesthesiologists class I, aged 4-24 months, were included in this positive controlled, randomised, blinded clinical trial. Cats admitted for ovariohysterectomy were allocated to group oral tramadol (GOT, n = 12) or group intramuscular tramadol (GIMT, n = 12). In GOT, tramadol (6 mg/kg) was given orally 60 mins, and saline was given intramuscularly 30 mins, before induction of anaesthesia. In GIMT, granulated sugar in capsules was given orally 60 mins and tramadol (4 mg/kg) intramuscularly 30 mins before induction of anaesthesia. In both groups, dexmedetomidine (0.007 mg/kg) was given intramuscularly 30 mins before induction of anaesthesia with intravenous propofol. Anaesthesia was maintained with isoflurane in oxygen, and atipamezole (0.037 mg/kg) was given intramuscularly 10 mins after extubation. The UNESP-Botucatu multidimensional composite scale was used to conduct pain assessments before premedication and at 20, 60, 120, 240 and 360 mins post-extubation or until rescue analgesia was given. To compare groups, the 60 min postoperative pain scores and the highest postoperative pain scores were analysed via a two-tailed Mann-Whitney test, and the incidences of rescue analgesia were analysed via a Fisher's exact test; P <0.05.

RESULTS

There was no significant difference between groups for the 60 min (P = 0.68) pain scores. The highest postoperative pain score was higher for GIMT compared with GOT (P = 0.04). Only two cats required rescue analgesia, both from GIMT. The incidence of rescue analgesia was not significantly different between groups (P = 0.46).

CONCLUSIONS AND RELEVANCE

In the present study, preoperative administration of oral tramadol at 6 mg/kg to cats provided adequate analgesia for 6 h following ovariohysterectomy surgery.

Sedative effects of acepromazine in combination with nalbuphine or butorphanol, intramuscularly or intravenously, in healthy cats: a randomized, blinded clinical trial

OBJECTIVES

The aim of this study was to compare the sedative effects in cats administered acepromazine-nalbuphine and acepromazine-butorphanol, intramuscularly (IM) and intravenously (IV), and the occurrence of adverse cardiorespiratory effects.

METHODS

Forty-six cats were randomly divided into four groups and administered acepromazine (0.05 mg/kg) combined with nalbuphine (0.5 mg/kg) or butorphanol (0.4 mg/kg), IV (ACP-NALIV and ACP-BUTIV groups, respectively) or IM (ACP-NALIM and ACP-BUTIM groups, respectively). Sedation scores, ease of intravenous catheter placement (simple descriptive scale [SDS] scores), physiologic variables, venous blood gases and the propofol dose required for anesthetic induction were recorded.

RESULTS

Mild sedation was observed in all groups approximately 30 mins after treatment administration (timepoint T1, prior to propofol administration). Sedation scores at T1 increased above baseline in all groups (P <0.05), but no significant difference was observed among groups. Dynamic interactive visual analogue scale sedation scores (range 0-100 mm) recorded at T1 were (median [interquartile range]): ACP-NALIM, 12 (10-12); ACP-NALIV, 11 (6-16); ACP-BUTIM, 11 (7-14); and ACP-BUTIV, 12 (7-19). Overall, SDS scores did not change from baseline at T1 and there was no significant difference among groups. The propofol dose did not differ among groups. Blood gases remained within the reference intervals for cats. Significant decreases from baseline were detected for all groups in systolic arterial pressure (SAP). Mean ± SD values at T1 were (mmHg): ACP-NALIM, 108 ± 13; ACP-NALIV, 102 ± 10; ACP-BUTIM, 97 ± 13; and ACP-BUTIV, 98 ± 21. Arterial hypotension (SAP <90 mmHg) was recorded at T1 in 0/11, 1/13, 4/11 and 5/11 cats in groups ACP-NALIM, ACP-NALIV, ACP-BUTIM and ACP-BUTIV, respectively, and was further exacerbated after the induction of anesthesia with propofol.

CONCLUSIONS AND RELEVANCE

In healthy cats administered acepromazine-nalbuphine and acepromazine-butorphanol, IM and IV, the degree of sedation was mild regardless of the protocol and the route of administration. The main adverse effect observed was a reduction in arterial blood pressure.

Comparison of the effects of methadone and butorphanol combined with acepromazine for canine gastroduodenoscopy

OBJECTIVE

To evaluate the feasibility of gastroduodenoscopy in dogs premedicated with acepromazine in combination with butorphanol or methadone.

STUDY DESIGN

Prospective, randomized, double-blinded clinical trial.

ANIMALS

A group of 40 client-owned dogs.

METHODS

Dogs were randomly allocated to one of two groups and give intramuscular acepromazine 0.02 mg kg^-1 combined with either butorphanol 0.3 mg kg^-1 (group ACEBUT) or methadone 0.2 mg kg^-1 (group ACEMET). General anaesthesia was induced with propofol and ketamine and maintained with sevoflurane (2.3%) in oxygen. Cardiopulmonary variables were recorded at 5 minute intervals during anaesthesia. Feasibility of the entire gastroduodenoscopy was evaluated with a visual analogue scale (VAS) from 0 (best) to 100 (worst) (primary outcome of the study). Lower oesophageal sphincter dilatation and duodenal intubation were scored. Pylorus diameter was measured with standard endoscopic inflatable balloons. Overall cardiovascular stability was assessed during anaesthesia, using a VAS (0-100), as was the presence of fluid in the oesophagus, regurgitation, need for mechanical ventilation, and intraoperative and postoperative rescue analgesia (secondary outcomes of the study). Differences between treatments were analysed with Mann-Whitney U, Student t test, Fisher exact test or mixed model analysis of variance as appropriate. Subsequently, feasibility VAS of the gastroduodenoscopy was assessed for noninferiority between groups. The noninferiority margin was set as -10.

RESULTS

All gastroduodenoscopies were successfully completed in both groups using an endoscope tip diameter of 12.8 mm in all but one dog. Feasibility of gastroduodenoscopy was evaluated as 2.9 ± 5.6 in group ACEBUT and 5.1 ± 5.8 in group ACEMET. No significant differences between groups were detected in any measured or assessed variables, and noninferiority was confirmed.

CONCLUSION AND CLINICAL RELEVANCE

In our study population, the effects of methadone and butorphanol when combined with acepromazine were comparable.

Intramuscular alfaxalone and methadone with or without ketamine in healthy cats: effects on sedation and echocardiographic measurements

OBJECTIVE

To evaluate the effect of alfaxalone and methadone administered intramuscularly (IM), with or without ketamine, on sedation and echocardiographic measurements in healthy cats.

STUDY DESIGN

A randomized, blinded, clinical study.

ANIMALS

A group of 24 client-owned cats.

METHODS

Baseline echocardiographic evaluation (bEchoCG) was performed. Cats were given IM alfaxalone (2 mg kg^-1) and methadone (0.3 mg kg^-1) with (AMK group) or without (AM group) ketamine (1 mg kg^-1). A sedation score (0-5, indicating none to good sedation) was assigned at 5 (T5), 10 (T10) and 15 (T15) minutes after IM injection. At T15, a second echocardiographic evaluation (sEchoCG) was performed. Data are shown as median (range). Significance was p < 0.05.

RESULTS

Finally, 21 cats were included. Sedation score was significantly higher in the AMK (11 cats) than in the AM group (10 cats): 4 (1-5) versus 0.5 (0-4) at T5 (p = 0.003); 4 (1-5) versus 1.5 (0-5) at T10 (p = 0.043); and 4 (1-5) versus 2 (0-5) at T15 (p = 0.024). All echocardiographic measurements obtained were within reference ranges. Between the groups, aortic root area (p = 0.009) and end-diastolic aortic dimension (p = 0.011) were significantly higher in the AM group at bEchoCG and sEchoCG, respectively. Within each group, values at bEchoCG and sEchoCG showed no significant differences, except for pulmonary peak velocity (0.85 m second^-1; p = 0.028) in the AMK group and ejection time (154 m second; p = 0.03) in the AM group; both variables decreased after sedation.

CONCLUSIONS AND CLINICAL RELEVANCE

In this population of healthy cats, neither protocol produced clinically meaningful effects on the echocardiographic variables evaluated. Alfaxalone with methadone produced mild sedation, whereas the addition of 1 mg kg^-1 ketamine induced adequate sedation for diagnostic procedures.

Comparison of perioperative analgesia using the infiltration of the surgical site with ropivacaine alone and in combination with meloxicam in cats undergoing ovariohysterectomy

Background

Infiltration of the surgical site with local anesthetics combined with nonsteroidal anti-inflammatory drugs may play an important role in improving perioperative pain control. This prospective, randomized, blinded, controlled clinical trial aimed to evaluate intraoperative isoflurane requirements, postoperative analgesia, and adverse events of infiltration of the surgical site with ropivacaine alone and combined with meloxicam in cats undergoing ovariohysterectomy. Forty-five cats premedicated with acepromazine/meperidine and anesthetized with propofol/isoflurane were randomly distributed into three treatments (n = 15 per group): physiological saline (group S), ropivacaine alone (1 mg/kg, group R) or combined with meloxicam (0.2 mg/kg, group RM) infiltrated at the surgical site (incision line, ovarian pedicles and uterus). End-tidal isoflurane concentration (FE’ISO), recorded at specific time points during surgery, was adjusted to inhibit autonomic responses to surgical stimulation. Pain was assessed using an Interactive Visual Analog Scale (IVAS), UNESP-Botucatu Multidimensional Composite Pain Scale (MCPS), and mechanical nociceptive thresholds (MNT) up to 24 h post-extubation. Rescue analgesia was provided with intramuscular morphine (0.1 mg/kg) when MCPS was ≥6.

Results

Area under the curve (AUC) of FE’ISO was significantly lower (P < 0.0001) in the RM (17.8 ± 3.1) compared to S (23.1 ± 2.2) and R groups (22.8 ± 1.1). Hypertension (systolic arterial pressure > 160 mmHg) coinciding with surgical manipulation was observed only in cats treated with S and R (4/15 cats, P = 0.08). The number of cats receiving rescue analgesia (4 cats in the S group and 1 cat in the R and RM groups) did not differ among groups (P = 0.17). The AUC of IVAS, MCPS and MNT did not differ among groups (P = 0.56, 0.64, and 0.18, respectively). Significantly lower IVAS pain scores were recorded at 1 h in the RM compared to the R and S groups (P = 0.021–0.018). There were no significant adverse effects during the study period.

Conclusions

Local infiltration with RM decreased intraoperative isoflurane requirements and resulted in some evidence of improved analgesia during the early postoperative period. Neither R nor RM infiltration appeared to result in long term analgesia in cats undergoing ovariohysterectomy.

Combined spinal and general anaesthesia in 58 cats undergoing various surgical procedures: description of technique and retrospective perioperative evaluation

OBJECTIVES

The aim of this retrospective study was to describe the spinal anaesthesia (SA) technique and evaluate the incidence of perioperative complications in cats.

METHODS

The anaesthetic records of cats of American Society of Anaesthesiologists physical status I, II and III, which received general and SA for different surgeries between 2012 and 2016, were examined. SA was administered through a 25 G Quincke needle, using an isobaric solution of bupivacaine and morphine at the level of either the L7-S1 interspaces (sternal recumbency) or the L5-6/L6-7 interspaces (lateral recumbency). Procedural failure rate (PFR), drugs and dose used, heart rate (HR), arterial blood pressure, incidence of bradycardia (HR <100 bpm) and hypotension (mean arterial pressure [MAP] <60 mmHg for at least 5 mins), intraoperative rescue analgesia (iRA) and any other detrimental events and their treatment until discharge were recorded. Abdominal surgery cases were excluded from the intraoperative evaluation.

RESULTS

A total of 58 anaesthetic records met the inclusion criteria and were analysed. PFR related to the space of injection (L7-S1 vs L5-6/L6-7) was 3/11 (27%) and 1/47 (2%), respectively (P = 0.017). The total median dose of intrathecal bupivacaine and morphine was 0.8 (range 0.5-1.6 mg/kg) and 0.10 (0.05-0.18 mg/kg), respectively. Nine of 46 (20%) cats received iRA, and no iRA cases were reported with a dose of bupivacaine higher than 0.8 mg/kg. Median HR and MAP before intrathecal injection (T0) and 10 mins after (T1) were, respectively, 118 bpm (range 74-190 bpm) and 106 bpm (67-160 bpm) (P = 0.005), and 65 mmHg (range 50-94 mmHg) and 52 mmHg (range 35-85 mmHg) (P = 0.003). Bradycardia was reported in 18/46 (39%) cats and hypotension in 23/46 (50%) cats. No complications were recorded during the observation period.

CONCLUSIONS AND RELEVANCE

SA was characterised by a low PFR when performed at the L5-6/L6-7 interspaces and low postoperative complications. Hypotension and bradycardia were the most common side effects.

Comparison between methadone and buprenorphine within the QUAD protocol for perioperative analgesia in cats undergoing ovariohysterectomy

OBJECTIVES

The aim of this study was to investigate the analgesic efficacy of methadone vs buprenorphine within the QUAD protocol for anaesthesia in cats undergoing ovariohysterectomy.

METHODS

One hundred and twenty cats were recruited to an assessor-blinded, randomised clinical trial. Cats received either methadone (5  mg/m2) or buprenorphine (180 µg/m2) combined with ketamine, midazolam and medetomidine intramuscularly. Anaesthesia was maintained with isoflurane in oxygen. Atipamezole was administered at extubation. Pain was assessed using the feline Composite Measure Pain Scale (CMPS-F), a dynamic interactive visual analogue scale (DIVAS) and mechanical nociceptive threshold (MNT). Sedation, pain, heart rate and respiratory rate were measured prior to QUAD administration, before intubation, and 2, 4, 6 and 8 h post-QUAD administration. If indicated by the CMPS-F, rescue analgesia was provided with 0.5 mg/kg of methadone administered intramuscularly. Meloxicam was administered after the last assessment. Differences in pain scores between groups were compared using a two-way repeated-measures ANOVA and requirement for rescue analgesia was compared using a χ2 test.

RESULTS

Cats administered methadone had lower CMPS-F scores over time (P = 0.04). Eighteen of 60 cats required rescue analgesia in the methadone group vs 29/60 in the buprenorphine group (P = 0.028). All cats that received rescue analgesia required it within 6 h post-QUAD administration. There were no differences between groups in MNT or pain measured using the DIVAS.

CONCLUSIONS AND RELEVANCE

Methadone produced clinically superior postoperative analgesia for the first 8 h after neutering than buprenorphine when used within the QUAD protocol.

The antinociceptive effects of intravenous administration of three doses of butorphanol tartrate or naloxone hydrochloride following hydromorphone hydrochloride to healthy conscious cats

OBJECTIVE

To evaluate thermal antinociception from intravenous (IV) administration of hydromorphone alone or followed by butorphanol or naloxone in cats.

STUDY DESIGN

Randomized, controlled, masked, crossover design.

ANIMALS

A group of eight adult female cats.

METHODS

Cats were administered six treatments of two IV injections 30 minutes apart: treatments S-S, two 0.9% saline; H-S, hydromorphone (0.1 mg kg^-1) and saline; H-LB, hydromorphone and butorphanol (0.02 mg kg^-1); H-MB, hydromorphone and butorphanol (0.1 mg kg^-1); H-HB, hydromorphone and butorphanol (0.2 mg kg^-1); H-N, hydromorphone and naloxone (0.04 mg kg^-1). Skin temperature (ST), thermal threshold (TT) and sedation score (SS) were recorded before (baseline) and for 8 hours after the first injection. Percentage maximum possible effect (%MPE), thermal excursion (TE), TT, SS and ST were compared using two-way repeated measures anova or Friedman test followed by Tukey's or Dunn's multiple comparisons test when appropriate. Significance was set at p ≤ 0.05.

RESULTS

Data from seven cats were analyzed. There were no significant differences among treatments in baseline values, SS and within S-S over time. Compared with respective 0.5 hour values following hydromorphone administration, %MPE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 4-8 hours for H-MB; at 6-8 hours for H-HB and at 1-8 hours for H-N. Compared with respective 0.5 hour values, TE was significantly lower at 4-8 hours for H-S; at 3-8 hours for H-LB; at 2 and 4-8 hours for H-MB; at 6 and 8 hours for H-HB and at 1-8 hours for H-N.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol and naloxone reduced hydromorphone-induced thermal antinociception. Butorphanol preserved hydromorphone antinociceptive properties better than naloxone. Butorphanol is recommended during non-life-threatening scenarios as a partial reversal agent for hydromorphone in cats.

Effect of non-steroidal anti-inflammatory drugs on postoperative respiratory and heart rate in cats subjected to ovariohysterectomy

Objectives The use of physiological parameters such as respiratory rate and heart rate to assess pain has long been discussed. The aim of the study was to compare postoperative respiratory rate and heart rate in cats subjected to flank ovariohysterectomy treated with a preoperative non-steroidal anti-inflammatory drug (NSAID) or no NSAID, and determine whether these parameters are suitable for postoperative pain assessment in cats. We hypothesised that cats without an NSAID would experience more postoperative pain, which may increase heart rate and respiratory rate. Methods A total of 168 female privately owned cats were studied. All cats were premedicated with medetomidine (0.08 mg/kg) and butorphanol (0.4 mg/kg) subcutaneously and anaesthesia was induced with intramuscular ketamine (5 mg/kg). Cats were divided into subgroups; controls (no NSAID) or cats given an NSAID, carprofen (4 mg/kg) or meloxicam (0.3 mg/kg), at premedication or induction of anaesthesia. Cats were subjected to flank ovariohysterectomy by the same surgeon. Atipamezole was administered 2.5 h after induction of anaesthesia. Respiratory rate and heart rate were measured 3.5 h after the induction of anaesthesia. Data were analysed using one-way ANOVA with mixed procedure and Tukey's adjustment method for multiplicity. Results The postoperative respiratory rate and heart rate per minute for all cats were 34.0 ± 8.6 and 167.5 ± 27.4, respectively. Neither respiratory rate nor heart rate differed significantly between the control group and the NSAID groups or between different time points of administration of NSAIDs. Conclusion and relevance Assuming there was less postoperative pain in the group administered NSAIDs, the results of the study presented no support for use of respiratory rate and heart rate as parameters for postoperative pain assessment in individual cats. Study limitations included a lack of pain scoring and baseline data for respiratory rate and heart rate.

Effect of administration rate on propofol requirement in cats

Objectives The objective of this study was to determine the effect of administration rate on propofol dose for induction of anesthesia and the effect of methadone on this dose. Methods This was a prospective, randomized, blinded clinical study. Forty male cats (mean ± SD age 1.5 ± 0.8 years) were admitted for orchiectomy. Cats were randomly allocated to receive acepromazine (0.05 mg/kg) with either methadone (MET; 0.3 mg/kg) or saline (SAL; 0.03 ml/kg). Each premedication group then received anesthetic induction with propofol at 5 (F) or 1.5 mg/kg/min (S), resulting in the following four groups: MET-F, SAL-F, MET-S and SAL-S. Sedation scores were assigned at 15 and 30 mins after premedication using a simple descriptive scale (SDS) and a visual analog scale (VAS). After assignment of sedation scores, respiratory frequency ( fR) was recorded, and anesthetic induction began and was continued until cats lost their palpebral reflexes and jaw tone, and the eye globe rotated ventromedially. The time for induction and the total amount of propofol needed was recorded, and intubation was then performed. After intubation, fR was also recorded. Results SDS and VAS sedation scores were low at 15 and 30 mins after premedication. There was no significant difference in sedation scores by time or between the groups at any time on any scale. The amount of propofol needed to achieve anesthetic induction was 5.3 ± 1.1 mg/kg in group MET-F, which was statistically lower when compared with the other three groups, which demonstrated no difference among them. Conclusions and relevance Premedication with acepromazine and methadone was not able to produce adequate sedation in healthy cats. The slow induction rate is not adequate for use in cats considering that all of the animals demonstrated excitement during anesthetic induction. The fast administration rate was able to produce adequate induction of anesthesia and reduce the amount of propofol needed to achieve intubation only when using methadone.

Effects of ketamine and alfaxalone on application of a feline pain assessment scale

OBJECTIVES

The objective of this study was to compare the effects of ketamine and alfaxalone on the application of a validated feline-specific multidimensional composite pain scale (UNESP-Botucatu MCPS).

METHODS

In a prospective, randomized, blinded, crossover trial, 11 adult cats (weight 4.4 ± 0.6 kg) were given dexmedetomidine (15 μg/kg) and hydromorphone (0.05 mg/kg) with either alfaxalone (2 mg/kg) or ketamine (5 mg/kg) as a single intramuscular injection for the induction of general anesthesia. After orotracheal intubation, general anesthesia (without surgery) was maintained for 32 mins with isoflurane, followed by atipamezole. The following parameters were recorded at baseline, 1-8 h and 24 h post-extubation: pain (pain expression and psychomotor subscales) and sedation scale scores. Alfaxalone treatment injection sites were examined for inflammation at baseline, postinjection, and 8 h and 24 h post-extubation.

RESULTS

Psychomotor scores were higher with ketamine at hours 1 (3.5 [0-5.0], P <0.0001), 2 (2.5 [0-4.0], P <0.0001) and 3 (0.5 [0-4.0], P = 0.009) post-extubation compared with alfaxalone (hour 1, 0 [0-2]; hour 2, 0 [0-0]; hour 3, 0 [0-0]). Six cats in the ketamine group crossed the analgesic intervention threshold. In contrast, pain expression scores did not differ significantly between treatments at any time (P >0.05); one cat from each group crossed the analgesic intervention threshold. Sedation was greater with ketamine (1 [0-3], P = 0.02) than alfaxalone (0 [0-1]) 1 h post-extubation. No cats had visible inflammation at the injection sites at any time.

CONCLUSIONS AND RELEVANCE

Ketamine has a confounding effect on the psychomotor subscale of the pain scale studied, which may lead to erroneous administration of rescue analgesia. In contrast, alfaxalone was not associated with significant increases in either pain subscale. These effects of ketamine should be considered when evaluating acute postoperative pain in cats.

Evaluation and optimisation of propofol pharmacokinetic parameters in cats for target-controlled infusion

The aim of this study was to develop and evaluate a pharmacokinetic model-driven infusion of propofol in premedicated cats. In a first step, propofol (10 mg/kg) was administered intravenously over 60 seconds to induce anaesthesia for the elective neutering of seven healthy cats, premedicated intramuscularly with 0.3 mg/kg methadone, 0.01 mg/kg medetomidine and 2 mg/kg ketamine. Venous blood samples were collected over 240 minutes, and propofol concentrations were measured via a validated high-performance liquid chromatography assay. Selected pharmacokinetic parameters, determined by a three-compartment open linear model, were entered into a computer-controlled infusion pump (target-controlled infusion-1 (TCI-1)). In a second step, TCI-1 was used to induce and maintain general anaesthesia in nine cats undergoing neutering. Predicted and measured plasma concentrations of propofol were compared at specific time points. In a third step, the pharmacokinetic parameters were modified according to the results from the use of TCI-1 and were evaluated again in six cats. For this TCI-2 group, the median values of median performance error and median absolute performance error were -1.85 per cent and 29.67 per cent, respectively, indicating that it performed adequately. Neither hypotension nor respiratory depression was observed during TCI-1 and TCI-2. Mean anaesthesia time and time to extubation in the TCI-2 group were 73.90 (±20.29) and 8.04 (±5.46) minutes, respectively.

Methadone in combination with medetomidine as premedication prior to ovariohysterectomy and castration in the cat

OBJECTIVES

The aim of the study was to evaluate the tolerability, sedative and analgesic effects of methadone in combination with medetomidine for premedication prior to neutering in healthy cats.

METHODS

This was an assessor-blinded, randomised, clinical research study. Forty-five cats were recruited and divided into three treatment groups of 15. Following premedication with medetomidine (20 µg/kg) and one of the three test drugs - methadone 0.5 mg/kg, buprenorphine 20 µg/kg or butorphanol 0.4 mg/kg intramuscularly - anaesthesia was induced with propofol and maintained with isoflurane, and neutering was carried out. Sedation and physiological parameters were assessed before premedication, after premedication before induction of anaesthesia, and at 90 mins and 2, 3, 4, 6, 7, 8 and 24 h after premedication. Pain and mechanical nociceptive threshold were assessed at similar time points.

RESULTS

There were no differences between groups with respect to age, sex, duration of anaesthesia or surgery. Most cats had low pain scores in the postoperative period, with small differences in pain scores between groups at individual time points only. Five, two and no cats required additional rescue analgesia in the postoperative period in the butorphanol, methadone and buprenorphine groups, respectively, representing no significant difference between groups.

CONCLUSIONS AND RELEVANCE

Medetomidine combined with methadone for premedication prior to neutering in healthy cats provided adequate analgesia for the first 6 h after administration with no adverse effects; effects overall were comparable with medetomidine combined with buprenorphine or butorphanol. Administration of further analgesia with methadone at 6 h and a non-steroidal anti-inflammatory drug at 8 h provided adequate analgesia for the first 24 h after surgery.

Evaluation of the perioperative analgesic efficacy of buprenorphine, compared with butorphanol, in cats

OBJECTIVE

To compare the analgesic effects of buprenorphine and butorphanol in domestic cats.

DESIGN

2-phase positive-controlled randomized masked clinical trial.

ANIMALS

39 healthy female cats (10 in phase 1 and 29 in phase 2).

PROCEDURES

Cats admitted for ovariohysterectomy received buprenorphine (4 in phase 1; 14 in phase 2) or butorphanol (6 in phase 1; 15 in phase 2). In phase 1, cats were premedicated with buprenorphine (0.02 mg/kg [0.009 mg/lb], IM) or butorphanol (0.4 mg/kg [0.18 mg/lb], IM), in combination with medetomidine. Anesthesia was induced with propofol (IV) and maintained with isoflurane in oxygen. After extubation, medetomidine was antagonized with atipamezole. A validated multidimensional composite scale was used to assess signs of pain after surgery starting 20 minutes after extubation and continuing for up to 360 minutes, and pain score comparisons were made between the 2 groups. Phase 2 proceeded similar to phase 1 with the following addition: during wound closure, cats from the butorphanol and buprenorphine groups received butorphanol (0.4 mg/kg, IM) or buprenorphine (0.02 mg/kg, IM), respectively.

RESULTS

Phase 1 of the study was stopped after 10 cats were ovariohysterectomized because 9 of 10 cats required rescue analgesia at the first evaluation. In phase 2, at the first pain evaluation, pain scores from the buprenorphine group were lower, and all cats from the butorphanol group required rescue analgesia. None of the cats from the buprenorphine group required rescue analgesia at any time.

CONCLUSIONS AND CLINICAL RELEVANCE

Buprenorphine (0.02 mg/kg, IM) given before surgery and during wound closure provided adequate analgesia for 6 hours following ovariohysterectomy in cats, whereas butorphanol did not.

The safety of high-dose buprenorphine administered subcutaneously in cats

The safety of a proprietary formulation of buprenorphine hydrochloride administered subcutaneously (SC) to young cats was investigated in a blinded, randomized study. Four cohorts of eight cats aged approximately 4 months were administered saline, 0.24, 0.72 or 1.20 mg/kg/day buprenorphine SC for nine consecutive days, representing 0×, 1×, 3× and 5× of the intended dose. Cats were monitored daily for evidence of clinical reactions, food and water intake and adverse events (AEs). Physical examinations, clinical pathology, vital signs and electrocardiograms (ECGs) were evaluated at protocol-specified time points. Complete necropsy and histopathologic examinations were performed following humane euthanasia. Four buprenorphine-treated cats experienced AEs during the study, two unrelated and two related to study drug administration. The two cats with AEs considered related to drug administration had clinical signs of hyperactivity, difficulty in handling, disorientation, agitation and dilated pupils in one 0.24 mg/kg/day cat and one 0.72 mg/kg/day cat. All of these clinical signs were observed simultaneously. There were no drug-related effects on survival, injection response, injection site inspections, body weight, food or water consumption, bleeding time, urinalysis, respiration rate, heart rate, ECGs, blood pressures, body temperatures, macroscopic examinations or organ weights. Once daily buprenorphine s.c. injections at doses of 0.24, 0.72 and 1.20 mg/kg/day for 9 consecutive days were well tolerated in young domestic cats.

Effects of continuous rate infusion of butorphanol in isoflurane-anesthetized calves

PURPOSE

To assess the hemodynamic changes and bispectral index (BIS) following administration of a continuous rate infusion (CRI) of butorphanol in isoflurane-anesthetized calves.

METHODS

Eight calves weighing 110 ± 12 kg were included in the study. Anesthesia was induced with 5% isoflurane in O2 delivered via face mask and maintained with end-tidal concentration of 1.4%. IPPV was set to a peak inspiratory airway pressure of 15 cmH2O and respiratory rate of six breaths minute-1. Forty minutes after the start of anesthetic maintenance, 0.1 mg kg-1butorphanol was administered intravenously, followed by a CRI of 20 µg kg-1 minute-1. Hemodynamic variables and BIS were recorded before butorphanol administration (T0), and at 10, 20, 40 and 80 minutes following the CRI. Anesthesia was discontinued after the last recording and the calves were allowed to recover. The time to sternal recumbency (SRE) and standing (ST) were evaluated.

RESULTS

There were no significant differences between the moments in all hemodynamic variables and BIS. The time to SRE and ST was 9 ± 5 and 14 ± 7 minutes, respectively.

CONCLUSION

The continuous rate infusion did not produce clinically relevant changes in hemodynamic or bispectral index values compared to baseline in mechanically ventilated and unstimulated calves anesthetized at 1.4% isoflurane.