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

Can a Sacrococcygeal Epidural of 0.25% Bupivacaine Prevent the Activation of the Sympathetic Nervous System during Feline Ovariectomy?

The ovariectomy (OVE) procedure can trigger somatosensory and visceral peritoneal nociception. Sacrococcygeal epidural (ScE) anesthesia may complement or replace systemic analgesia used for feline OVE, reducing opioid consumption and their related undesirable adverse effects and consequently reducing or completely blocking the sympathetic nervous system activation during this procedure. The present study aimed to evaluate the activation of the sympathetic nervous system resulting from adding an ScE injection of bupivacaine 0.25% (0.3 mL kg-1) in feline OVE and identify whether this translates to hemodynamic variables stability. A Parasympathetic Tone Activity (PTA) monitor was applied given that it performs analysis of heart rate variability (HRV) detecting changes in sympathetic and parasympathetic tone, making it a good tool for detecting activation of the sympathetic nervous system during the study. Two groups of animals were evaluated in five perioperative times, namely, the control group (CG) (n = 18) with systemic analgesia alone and the sacrococcygeal epidural group (ScEG) (n = 20) with 0.25% bupivacaine combined with systemic analgesia. Thirty-eight female cats were selected. All animals assigned to CG and ScEG were premedicated with dexmedetomidine (20 μg kg-1 IM) and methadone (0.2 mg kg-1 IM). General anesthesia was induced with propofol IV ad effectum and maintained with isoflurane in 100% oxygen. Heart rate, non-invasive systolic and median blood pressure, respiratory rate, and instantaneous parasympathetic tone activity were recorded. Compared to systemic analgesia alone (CG), sacrococcygeal epidural (ScEG) reduced the rise of common hemodynamic variables but did not prevent sympathetic nervous system activation.

Comparison of analgesic efficacy of tramadol, morphine and methadone in cats undergoing ovariohysterectomy

OBJECTIVES

The aim of this study was to compare the analgesic efficacy and the effect on physiological variables and behavior of the use of tramadol, methadone and morphine as preoperative analgesia in healthy cats undergoing elective ovariohysterectomy.

METHODS

Cats undergoing ovariohysterectomy were randomly assigned to receive one of the following premedication treatments intramuscularly: methadone (0.2 mg/kg; n = 10); morphine (0.2 mg/kg; n = 10); or tramadol (3 mg/kg; n = 10). Induction of anesthesia was done with propofol, and maintenance of anesthesia was done with isoflurane. Intraoperative heart rate, arterial blood pressure, respiratory rate, end-tidal isoflurane concentration and frequency of rescue analgesia (fentanyl 2.5 µg/kg) were compared between groups. Postoperative analgesia was assessed using the UNESP-Botucatu Multidimensional Composite Pain Scale, and perioperative serum glucose, cortisol concentrations and postoperative rescue analgesia were evaluated.

RESULTS

Intraoperative rescue analgesia was required in 76.5% of cats at some time during surgery, and 27% of cats required postoperative rescue analgesia up to 6 h after extubation. There were no significant differences between groups with respect to intraoperative and postoperative rescue analgesia, pain scale scores and end-tidal isoflurane concentrations. In the immediate postoperative period, after extubation, most of the patients presented with hypothermia; however, 1-6 h postoperatively, hyperthermia was observed in most of the patients, and was most common in the tramadol group.

CONCLUSIONS AND CLINICAL RELEVANCE

Under the conditions of this study, methadone, morphine and tramadol produced satisfactory postoperative analgesia in most of the cats undergoing ovariohysterectomy, and the effects lasted up to 6 h postoperatively. Intraoperative analgesia was not sufficient in most cases. Significant cardiovascular or respiratory effects contraindicating the use of these drugs were not found. Postanesthetic hyperthermia occurred with all opioids studied and was more frequent in the tramadol group.

Robenacoxib versus meloxicam following ovariohysterectomy in cats: A randomised, prospective clinical trial involving owner-based assessment of pain

BACKGROUND

Injectable non-steroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed to queens undergoing ovariohysterectomy (OVH), but the requirement for postoperative administration is unclear and practices vary. Existing studies assessing efficacy rely on pain scoring by experienced clinicians. However, following OVH, most cats are discharged within hours of recovery.

METHODS

Cats undergoing OVH were randomly assigned to two treatment groups: MEL and ROB. Cats in the MEL group (n = 76) received meloxicam (0.2 mg/kg) and those in the ROB group (n = 65) received robenacoxib (2 mg/kg). Owners were contacted by a blinded assessor 3 days postoperatively and asked to identify physical or behavioural changes and to assign pain scores using a numerical rating scale.

RESULTS

More cats in the ROB group displayed abnormal behaviours than cats in the MEL group (p = 0.03). Most owners assigned a pain score of 0 (72%) (n = 101), but pain scores were significantly higher in the ROB group than in the MEL group (p = 0.005).

LIMITATION

Methods of owner assessment of pain in cats have not been validated.

CONCLUSIONS

Both meloxicam and robenacoxib are effective in controlling postoperative pain. Meloxicam may have improved efficacy in certain patient populations. Applying a blanket approach to prescribing NSAIDs to cats undergoing OVH postoperatively may not be necessary. This has safety, environmental and cost implications.

Antinociceptive Effect of a Sacro-Coccygeal Epidural of Morphine and Lidocaine in Cats Undergoing Ovariohysterectomy

BACKGROUND

A commonly described analgesic protocol for ovariohysterectomy (OHE) combines systemic opioids, sedatives, and non-steroidal anti-inflammatory drugs. However, systemic analgesia does not fully prevent perioperative visceral and somatic pain triggered by the surgical stimulus.

OBJECTIVES

To compare the analgesic effects and quality of recovery of systemic analgesia with those of a sacrococcygeal epidural injection of lidocaine and morphine in cats undergoing elective OHE. Methods: Twenty domestic female cats were premedicated with dexmedetomidine (0.01 mg kg-1 IM) and alfaxalone (1.5 mg kg-1 IM) and randomly assigned to one of two analgesic protocols: methadone (0.2 mg kg-1 IM) in the control group CTR (n = 10) and methadone (0.1 mg kg-1 IM) + epidural (lidocaine 2% (0.3 mL kg-1) + morphine 1% (0.1 mg kg-1) diluted with NaCl 0.9% to a total volume of 1.5 mL in the SCC-E group (n = 10). General anaesthesia was induced with alfaxalone (1 mg kg-1 IV) and maintained with sevoflurane in 100% oxygen. Non-invasive blood arterial pressure and cardiorespiratory variables were recorded. The quality of recovery was assessed using a simple descriptive scale. Before surgery and 1, 2, 3, 4, 6, and 8 h post-op pain was assessed using the UNESP-Botucatu multidimensional composite pain scale (MCPS) and mechanical nociception thresholds (MNT). The repeated measures analysis of variance (ANOVA) was used to compare groups over time. Comparison between groups was performed using independent samples t-test if the assumption of normality was verified, or the Mann-Whitney test. The chi-square test of independence and exact Fisher's test were used to compare groups according to recovery quality.

RESULTS

Heart rate and systolic arterial pressure increased significantly from baseline values in the CTR group and did not change in the SCC-E group. In the CTR group, MNT and UNESP-Botucatu-MCPS scores increased significantly from baseline for all assessment points and the first 3 h, respectively, whereas this did not occur in the SCC-E group.

CONCLUSIONS AND CLINICAL RELEVANCE

Based on our results, the SCC-E administration of lidocaine 2% with morphine 1% is a reasonable option to provide perioperative analgesia in cats submitted to OHE, compared to a systemic protocol alone.

2022 ISFM Consensus Guidelines on the Management of Acute Pain in Cats

PRACTICAL RELEVANCE

Increases in cat ownership worldwide mean more cats are requiring veterinary care. Illness, trauma and surgery can result in acute pain, and effective management of pain is required for optimal feline welfare (ie, physical health and mental wellbeing). Validated pain assessment tools are available and pain management plans for the individual patient should incorporate pharmacological and non-pharmacological therapy. Preventive and multimodal analgesia, including local anaesthesia, are important principles of pain management, and the choice of analgesic drugs should take into account the type, severity and duration of pain, presence of comorbidities and avoidance of adverse effects. Nursing care, environmental modifications and cat friendly handling are likewise pivotal to the pain management plan, as is a team approach, involving the cat carer.

CLINICAL CHALLENGES

Pain has traditionally been under-recognised in cats. Pain assessment tools are not widely implemented, and signs of pain in this species may be subtle. The unique challenges of feline metabolism and comorbidities may lead to undertreatment of pain and the development of peripheral and central sensitisation. Lack of availability or experience with various analgesic drugs may compromise effective pain management.

EVIDENCE BASE

These Guidelines have been created by a panel of experts and the International Society of Feline Medicine (ISFM) based on the available literature and the authors' experience. They are aimed at general practitioners to assist in the assessment, prevention and management of acute pain in feline patients, and to provide a practical guide to selection and dosing of effective analgesic agents.

Ultrasound-guided erector spinae interfascial plane block for spinal surgery in three cats

Case series summary

The erector spinae plane (ESP) block consists of an interfascial injection of local anaesthetic between the erector spinae muscle group and the transverse processes of the thoracic vertebrae. This block targets the dorsal rami of the thoracic spinal nerves to desensitise the cutaneous area near the dorsal midline, the paraspinal muscles, the dorsal vertebral laminae and the facet joints. The purpose of this case series is to describe the perioperative analgesic effect and complications of ultrasound-guided ESP block with bupivacaine in three cats undergoing spinal surgery. Only one cardiovascular response was recorded in this case series. Just one cat received intraoperative rescue analgesia. Cats 1 and 2 recorded just one high pain score in the first 24 h postoperatively, and cat 3 recorded three high pain scores. The total amount of methadone given in the 24 h postoperatively was 0.6 mg/kg in cat 1, 0.9 mg/kg in cat 2 and 0.8 mg/kg in cat 3. All three cats suffered mild and transient intraoperative complications, which were easily addressed. There were no postoperative complications.

Relevance and novel information

This case series documents a novel locoregional anaesthesia technique as an alternative to traditional systemic analgesia. The technique is part of a multimodal analgesia approach for spinal surgery in cats. Perioperative analgesic effect and complications presented in this case series are evaluated and discussed.

The impact of a stress-reducing protocol on the quality of pre-anaesthesia in cats

INTRODUCTION

Transport to the clinic is a major source of stress for cats. The process involves being put into a carrier, driven in a car and handled. Cats are therefore removed from the safe-haven of their territory and experience many stressful stimuli and interactions.

METHODS

In the present study, 31 cats were transported to the clinic following a low-stress transport protocol and compared with a control group of 36 cats whose owners did not follow the protocol. This protocol involved preparing a cat carrier basket with F3 pheromone and keeping it covered and stable during the car journey from the home to the clinic. Pre-anaesthesia information was recorded for cardiac rate, respiratory rate, tolerance to handling, time for sedation to be achieved and dose of propofol required for induction and endotracheal intubation.

RESULTS

The group exposed to the low-stress transport protocol took less time to reach sedation and needed a lower dose of propofol for induction than the control group.

CONCLUSION

These results suggest that, in cats, pre-anaesthetic and induction requirements are influenced by lower-stress transport and handling.

A randomized clinical trial comparing butorphanol and buprenorphine within a multimodal analgesic protocol in cats undergoing orchiectomy

OBJECTIVES

The aim of this study was to compare the effects of butorphanol and buprenorphine, as part of a multimodal analgesic protocol, on recovery and analgesia in cats undergoing orchiectomy.

METHODS

In a prospective, randomized, blind clinical trial, 47 adult male cats were randomly assigned to receive either butorphanol (0.3 mg/kg, n = 24) or buprenorphine (0.02 mg/kg, n = 23) in combination with dexmedetomidine (25 μg/kg) and alfaxalone (2 mg/kg) as a single intramuscular injection for the induction of general anesthesia. Isoflurane carried in oxygen was supplemented as needed during orchiectomy. All cats received lidocaine (2 mg/kg intratesticular), meloxicam (0.3 mg/kg SC) and atipamezole (125 μg/kg IM) postoperatively. Pain and sedation scales were applied at baseline, and 2, 4 and 6 h postoperatively. Time to achieve sternal recumbency and to begin eating were also recorded.

RESULTS

Pain scale scores were low and showed no difference between the treatment groups at all time points (P ⩾0.99, all time points). Four cats exceeded the analgesia intervention threshold for rescue analgesia (butorphanol, n = 3; buprenorphine, n = 1). There was no difference in sedation scores between groups at any time point (P >0.99, all time points). Significantly more cats in the buprenorphine group (n = 12) required isoflurane than in the butorphanol group (n = 2) (P = 0.0013; relative risk 6.3, 95% confidence interval [CI] 1.8-23.5). There was no significant difference in time to achieve sternal recumbency (P = 0.96, 95% CI -20 to 20) between groups or in return to eating (P = 0.48, 95% CI -92.0 to 113.5), with most cats eating within 1 h of surgery (butorphanol, 79%; buprenorphine, 83%).

CONCLUSIONS AND RELEVANCE

There were no significant differences in analgesia or recovery between butorphanol and buprenorphine treatment groups as part of a multimodal injectable anesthetic protocol. Butorphanol is associated with superior depth of anesthesia, facilitating injectable anesthesia.

Comparison of the effects of buprenorphine and methadone in combination with medetomidine followed by intramuscular alfaxalone for anaesthesia of cats undergoing ovariohysterectomy

OBJECTIVES

The aim of this study was to compare the quality of anaesthesia and analgesia between methadone and buprenorphine in combination with medetomidine after induction with intramuscular (IM) alfaxalone in cats undergoing ovariohysterectomy.

METHODS

Fifty-one female cats (American Society of Anesthesiologists status I-II), with a median age of 12 months (range 2-60 months), weighing a mean ± SD of 2.5 ± 0.5 kg, were recruited to the study. Cats were randomly allocated to receive medetomidine (600 µg/m2) and buprenorphine (180 µg/m2) (group MB) or medetomidine (500 µg/m2) and methadone (5 mg/m2) (group MM) IM. Anaesthesia was induced 15 mins later using alfaxalone (3 mg/kg) IM. Anaesthesia was maintained with isoflurane in oxygen. All cats received meloxicam preoperatively. Quality of premedication and induction and intraoperative physiological parameters were recorded. Atipamezole (50% of medetomidine dose) was administered at the end of surgery. Cats were assessed postoperatively by the same blinded observer using a simple descriptive scale, numeric rating scale, dynamic interactive visual analogue scale (DIVAS) and UNESP-Botucatu multidimensional composite pain scales, at 10, 20 and 30 mins post-extubation. Parametric and non-parametric data were compared using Student's t-test or Mann-Whitney U-tests, respectively.

RESULTS

Forty-one cats completed the study. No significant differences were detected between groups before or during anaesthesia. No cats required rescue analgesia. DIVAS scores at 10 mins were significantly less in the MM group compared with the MB. No differences between groups at any other time points were detected using the four metrology instruments.

CONCLUSIONS AND RELEVANCE

Both protocols provided good anaesthesia conditions for ovariohysterectomy in the cat.

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.

Multimodal analgesia for treatment of allodynia and hyperalgesia after major trauma in a cat

Case summary

A 2-year-old polytraumatized male cat was admitted to a teaching hospital for correction of a defective inguinal herniorrhaphy. Upon arrival, the cat showed signs of neuropathic pain, including allodynia and hyperalgesia. Analgesic therapy was initiated with methadone and metamizole; however, 24 h later, the signs of pain continued. Reparative surgery was performed, and a multimodal analgesic regimen was administered (methadone, ketamine, wound catheter and epidural anesthesia). Postoperatively, the cat showed signs of severe pain, assessed using the UNESP-Botucatu multidimensional composite pain scale. Rescue analgesia was initiated, which included methadone, bupivacaine (subcutaneous wound-diffusion catheter) and transversus abdominis plane block. Because the response was incomplete, co-adjuvant therapy (pregabalin and electroacupuncture) was then implemented. Fourteen days after admission, the patient was discharged with oral tramadol and pregabalin for at-home treatment.

Relevance and novel information

Neuropathic pain is caused by a primary lesion or dysfunction in the nervous system and is a well-described complication following trauma, surgical procedures such as hernia repair, and inadequate analgesia. The aims of this report are to: (1) describe a presentation of neuropathic pain to highlight the recognition of clinical signs such as allodynia and hyperalgesia in cats; and (2) describe treatment of multi-origin, severe, long-standing, ‘mixed’ pain (acute inflammatory with a neuropathic component). The patient was managed using multiple analgesic strategies (multimodal analgesia), including opioids, non-steroidal anti-inflammatory drugs, locoregional anesthesia, co-adjuvant drugs and non-pharmacological therapy (electroacupuncture).

A comparison between methadone and buprenorphine for perioperative analgesia in dogs undergoing ovariohysterectomy

OBJECTIVE

To investigate whether preoperative methadone provides superior perioperative analgesia compared to buprenorphine in dogs undergoing ovariohysterectomy.

METHODS

Eighty female dogs were recruited to an assessor-blinded, randomised, clinical trial. Dogs received a premedication dose of 0·05 mg/kg acepromazine or 10 μg/kg medetomidine combined with either 0·3 mg/kg methadone or 20 μg/kg buprenorphine intramuscularly. Anaesthesia was induced with propofol and maintained with isoflurane. Pain was assessed using two scoring schemes (a dynamic interactive visual analogue scale and the short form of the Glasgow Composite Pain Scale) before premedication, 30 minutes later and every hour for 8 hours after premedication. If indicated, rescue analgesia was provided with methadone. Meloxicam was administered after the final assessment. The area under the curve for change in pain scores over time and the requirement for rescue analgesia were compared between groups.

RESULTS

Groups premedicated with buprenorphine had significantly higher pain scores than those premedicated with methadone. There was no interaction between opioid and sedative for any outcome measure. Rescue analgesia was required by significantly more dogs premedicated with buprenorphine (45%) than that of methadone (20%).

CLINICAL SIGNIFICANCE

At the doses investigated, methadone produced superior postoperative analgesia compared to buprenorphine in dogs undergoing ovariohysterectomy.

Comparison of intramuscular butorphanol and buprenorphine combined with dexmedetomidine for sedation in cats

Objectives The objective of this study was to compare the sedative effect of butorphanol-dexmedetomidine with buprenorphine-dexmedetomidine following intramuscular (IM) administration in cats. Methods Using a prospective, randomised, blinded design, 40 client-owned adult cats were assigned to receive IM dexmedetomidine (10 µg/kg) combined with either butorphanol (0.4 mg/kg) ('BUT' group) or buprenorphine (20 µg/kg) ('BUP' group). Sedation was scored using a previously published multidimensional composite scale before administration (T0) and 5, 10, 15 and 20 mins afterwards (T5, T10, T15 and T20, respectively). Alfaxalone (1.5 mg/kg) was administered IM at T20 if the cat was not deemed adequately sedated to place an intravenous catheter. Adverse events were recorded. Friedman two-way ANOVA analysed sedation scores within groups. Mann-Whitney Rank Sum test compared sedation scores between groups; Fisher's exact test analysed the frequency of alfaxalone administration and adverse events. P <0.05 was considered statistically significant. Results Sedation scores between groups were similar at baseline, but at T5, T10, T15 and T20 scores were higher in the BUT group ( P <0.01). Within both groups, sedation scores changed over time and the highest sedation scores were reached at T10. Requirement for additional sedation was similar between groups: two cats in the BUT group and five cats in the BUP group. One cat and 11 cats vomited ( P = 0.002) in the BUT and BUP groups, respectively. No other adverse events were recorded. Conclusions and relevance At these doses, IM buprenorphine-dexmedetomidine provides inferior sedation and a higher incidence of vomiting than butorphanol-dexmedetomidine in cats. Butorphanol-dexmedetomidine may be preferred for feline sedation, especially where vomiting is contraindicated.

Dexmedetomidine-methadone-ketamine versus dexmedetomidine-methadone-alfaxalone for cats undergoing ovariectomy

OBJECTIVE

To compare the duration, quality of anaesthesia and analgesia, and quality of recovery of dexmedetomidine and methadone combined with either ketamine or alfaxalone.

STUDY DESIGN

Randomized, prospective clinical trial.

ANIMALS

A group of 44 healthy client-owned cats presenting for ovariectomy.

METHODS

Cats were randomly assigned to one of the two treatment groups: DAM (n=22), which was administered intramuscularly (IM) dexmedetomidine (15 μg kg^-1), methadone (0.3 mg kg^-1) and alfaxalone (3 mg kg^-1), and DKM (n=22), which was administered IM dexmedetomidine (15 μg kg^-1), methadone (0.3 mg kg^-1) and ketamine (3 mg kg^-1). During anaesthesia, heart rate, respiratory rate and systolic arterial pressure were measured every 5 minutes. Cats that moved or had poor muscle relaxation were administered an additional 1 mg kg^-1 of either alfaxalone (DAM) or ketamine (DKM) intravenously (IV). In cases of increased autonomic responses to surgical stimulation, fentanyl (2 μg kg^-1) was administered IV. At the end of the surgery, atipamezole (75 μg kg^-1) was administered IM, and the times to both sternal recumbency and active interaction were recorded. Quality of recovery was evaluated with a simple descriptive scale. The UNESP-Botucatu multidimensional composite pain scale and a visual analogue scale were used to evaluate postoperative analgesia at the return of active interaction and 1, 2 and 3 hours later.

RESULTS

The additional anaesthesia and rescue fentanyl requirements were similar between groups. The quality of recovery was better in the DAM group than in the DKM group [simple descriptive scale scores: 0 (0-1) and 1 (0-3), respectively; p=0.002]. Postoperative pain scores decreased progressively over time in both groups, with no significant differences (p=0.08) between them.

CONCLUSIONS AND CLINICAL RELEVANCE

Both protocols provided comparable quality of anaesthesia and analgesia and were suitable for cats undergoing ovariectomy. In combination with methadone and dexmedetomidine, alfaxalone and ketamine showed comfortable and reliable recoveries.

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.