Cardiovascular effects of propofol alone and in combination with ketamine for total intravenous anesthesia in cats

Inhalational anaesthetic agent consumption within a multidisciplinary veterinary teaching hospital: an environmental audit

Inhalational anaesthetic agents are routinely used in veterinary anaesthesia practices, yet their consumption contributes significantly to greenhouse gas emissions and environmental impact. We conducted a 55-day observational study at a veterinary teaching hospital in Switzerland, monitoring isoflurane and sevoflurane consumption across small, equine and farm animal clinics and analysed the resulting environmental impact. Results revealed that in total, 9.36 L of isoflurane and 1.27 L of sevoflurane were used to anaesthetise 409 animals across 1,489 h. Consumption rates varied among species, with small and farm animals ranging between 8.7 and 13 mL/h, while equine anaesthesia exhibited a higher rate, 41.2 mL/h. Corresponding to 7.36 tonnes of carbon dioxide equivalent in total environmental emissions or between 2.4 and 31.3 kg of carbon dioxide equivalent per hour. Comparison to human anaesthesia settings showed comparable consumption rates to small animals, suggesting shared environmental implications, albeit on a smaller scale. This research highlights the importance of continued evaluation of veterinary anaesthesia practices to balance patient safety with environmental stewardship; potential mitigation strategies are explored and discussed.

Effects of different rates of propofol with or without S-ketamine on ventricular function in healthy cats - a randomized study

Propofol is used for anesthetic induction in cats and procedural sedation in countries where alfaxalone is not available. Studies have reported propofol-related effects in echocardiography variables in dogs and humans. However, there is a lack of echocardiography studies investigating propofol-related effects on cats. This study aimed to use echocardiography to investigate echocardiographic changes in three protocols using propofol: propofol-slow (2 mg/kg/min, PS); propofol-fast (8 mg/kg/min, PF); propofol-ketamine (S-ketamine 2 mg/kg bolus followed by propofol 2 mg/kg/min; PK) in healthy premedicated (gabapentin-buprenorphine-acepromazine; 200 mg/cat, 0.4, and 0.1 mg/kg, respectively), non-intubated cats. Echocardiographic measurements were obtained at three time points: baseline (before the administration of propofol), end of propofol titration (end-point, T0), and 15 min after T0 (T15). Propofol at a lower rate continued from T0 to T15. Echocardiographic and physiological variables included fractional shortening (FS%), ejection fraction (EF%), HR, BP, and others. Propofol requirements at T0 for PF, PS, and PK groups were 5.0 ± 0.9, 3.8 ± 0.7, and 2.4 ± 0.5 mg/kg, respectively. EF% neither change over time nor between groups. PF and PK showed a reduction in FS% at T0 (47 ± 6 to 34 ± 6 and 42 ± 6 to 36 ± 5, respectively). BP reduced significantly in PF and PS groups (136 ± 26 to 105 ± 13 and 137 ± 22 to 115 ± 15 mmHg, respectively). It is unclear whether changes in echocardiography variables were of clinical relevance related to treatment groups or a result of within-group individual responses.

Use of a propofol infusion for anaesthetic maintenance in Guinea pigs (Cavia porcellus): a retrospective case series

OBJECTIVE

To retrospectively evaluate the feasibility of a propofol infusion for anaesthetic maintenance in guinea pigs.

STUDY DESIGN

Retrospective case series.

ANIMALS

Client-owned guinea pigs undergoing general anaesthesia.

METHODS

Anaesthetic records of guinea pigs anaesthetized between March 2015 and March 2018 were reviewed. Animals administered a propofol infusion for > 20 minutes were identified and evaluated. Procedure performed, pre-anaesthetic medication, preoperative and intraoperative respiratory rate (fR) and heart rates (HRs), total amount of propofol administered, total anaesthesia and recovery times were extracted from the records and analysed using descriptive statistics and Pearson correlation tests. Data are reported as mean (range).

RESULTS

Records of 14 animals meeting the criteria were identified. Following drug combinations were administered for premedication: butorphanol 0.43 (0.3-0.5) mg kg-1, medetomidine 0.1 (0.05-0.2) mg kg-1 and midazolam 1 (0.5-2) mg kg-1 (n = 3); methadone 0.33 (0.25-0.5) mg kg-1, medetomidine 0.07 (0.01-0.1) mg kg-1 and midazolam 0.66 (0.5-1) mg kg-1 (n = 3); butorphanol 0.5 mg kg-1, medetomidine 0.05 mg kg-1 and ketamine 5 mg kg-1 (n = 2); buprenorphine 0.01 mg kg-1, medetomidine 0.07 (0.04-1) mg kg-1 and ketamine 4 (3-5) mg kg-1 (n = 3); butorphanol 0.5 mg kg-1, alfaxalone 1 mg kg-1 and midazolam 0.5 mg kg-1 (n = 1); and methadone 0.38 (0.25-0.5) mg kg-1, medetomidine 0.08 (0.06-1) mg kg-1 with midazolam 0.75 (0.5-1) mg kg-1 (n = 2). Preoperative and intraoperative HRs were 240 (160-300) and 170 (140-200) beats minute-1, respectively. Preoperative and intraoperative fR were 63 (50-86) and 37 (18-80) breaths minute-1, respectively. The propofol infusion rate was 0.45 (0.17-0.80) mg kg-1 minute-1. Total anaesthesia and recovery times were 60 (25-145) and 17 (8-60) minutes, respectively. A slight correlation was found between total propofol dose infused and recovery time (r = 0.58).

CONCLUSION AND CLINICAL RELEVANCE

Propofol infusions may be a useful alternative to inhalant anaesthetics.

Feline procedural sedation and analgesia: When, why and how

PRACTICAL RELEVANCE

Procedural sedation and analgesia (PSA) describes the process of depressing a patient's conscious state to perform unpleasant, minimally invasive procedures, and is part of the daily routine in feline medicine. Maintaining cardiopulmonary stability is critical while peforming PSA.

CLINICAL CHALLENGES

Decision-making with respect to drug choice and dosage regimen, taking into consideration the cat's health status, behavior, any concomitant diseases and the need for analgesia, represents an everyday challenge in feline practice. While PSA is commonly perceived to be an uneventful procedure, complications may arise, especially when cats that were meant to be sedated are actually anesthetized.

AIMS

This clinical article reviews key aspects of PSA in cats while exploring the literature and discussing complications and risk factors. Recommendations are given for patient assessment and preparation, clinical monitoring and fasting protocols, and there is discussion of how PSA protocols may change blood results and diagnostic tests. An overview of, and rationale for, building a PSA protocol, and the advantages and disadvantages of different classes of sedatives and anesthetics, is presented in a clinical context. Finally, injectable drug protocols are reported, supported by an evidence-based approach and clinical experience.

Comparison of Infusion of Propofol and Ketamine-Propofol Mixture (Ketofol) as Anesthetic Maintenance Agents on Blood Pressure of Patients Undergoing Orthopedic Leg Surgeries

Background

Some studies have reported the effects of anesthesia induction using a single propofol dose and low ketamine doses in short-term outpatient operations.

Objectives

In this study, we aimed to evaluate the intra and post-operative hemodynamic effects of ketamine-propofol mixture (Ketofol) infusion in comparison with propofol infusion.

Methods

This study was performed on 54 class I and II of the American Society of Anesthesia patients aged 15 to 45 years who were candidates for leg fracture surgery. The patients were randomly assigned to propofol and ketofol groups. In the propofol and ketofol groups, propofol infusion (100 µg/kg/min) and propofol-ketamine infusion (50 µg/kg/min propofol + 25 µg/kg/min ketamine) were used for the maintenance of anesthesia, respectively. Heart rate and systolic, diastolic and mean blood pressure before, immediately after the induction of anesthesia and at 10-minute intervals were measured and recorded. Pain, nausea, and vomiting were recorded immediately after surgery and each 2 hours until 6 hours.

Results

Systolic, diastolic and mean blood pressure were significantly higher in the ketofol group than in the propofol group at 10 - 60 min intervals (P < 0.05). There was no significant difference, however, between the two groups in terms of the severity of nausea and pain and vomiting frequency.

Conclusions

Infusion of hypnotic doses of ketofol leads to increase in diastolic and systolic blood pressure and improves blood pressure stability in addition to inducing more as compared with propofol infusion, but it leads to higher risk of nausea and vomiting.

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.

Pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol following a single induction dose administered intravenously in cats

OBJECTIVE

To compare the pharmacokinetics and pharmacodynamics of propofol with or without 2% benzyl alcohol administered intravenously (IV) as a single induction dose in cats.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Six healthy adult cats, three female intact, three male castrated, weighing 4.8 ± 1.8 kg.

METHODS

Cats received 8 mg kg(-1) IV of propofol (P) or propofol with 2% benzyl alcohol (P28) using a randomized crossover design. Venous blood samples were collected at predetermined time points to 24 hours after drug administration to determine drug plasma concentrations. Physiologic and behavioral variables were also recorded. Propofol and benzyl alcohol concentrations were determined using high pressure liquid chromatography with fluorescence detection. Pharmacokinetic parameters were described using a 2-compartment model. Pharmacokinetic and pharmacodynamic parameters were analyzed using repeated measures anova (p < 0.05).

RESULTS

Plasma concentrations of benzyl alcohol were below the lower limits of quantification (LLOQ) at all time points for two of the six cats (33%), and by 30 minutes for the remaining four cats. Propofol pharmacokinetics, with or without 2% benzyl alcohol, were characterized by rapid distribution, a long elimination phase, and a large volume of distribution. No differences were noted between treatments with the exception of clearance from the second compartment (CLD2), which was 23.6 and 38.8 mL kg(-1)  minute(-1) in the P and P28 treatments, respectively. Physiologic and behavioral variables were not different between treatments with the exception of heart rate at 4 hours post administration.

CONCLUSIONS AND CLINICAL RELEVANCE

The addition of 2% benzyl alcohol as a preservative minimally altered the pharmacokinetics and pharmacodynamics of propofol 1% emulsion when administered as a single IV bolus in this group of cats. These data support the cautious use of propofol with 2% benzyl alcohol for induction of anesthesia in healthy cats.

Evaluation of a ketamine-propofol drug combination with or without dexmedetomidine for intravenous anesthesia in cats undergoing ovariectomy

OBJECTIVE

To evaluate the use of a ketamine-propofol combination, with or without dexmedetomidine, in cats undergoing ovariectomy and to assess Heinz body formation following administration of these drugs.

DESIGN

Randomized clinical trial.

ANIMALS

15 client-owned female cats.

PROCEDURES

Anesthesia was induced with a ketamine (2.0 mg/kg [0.91 mg/lb])-propofol (2.0 mg/kg) combination with (n = 7) or without (8) dexmedetomidine (0.003 mg/kg [0.0013 mg/lb]) and was maintained via continuous IV infusion of a 1:1 ketamine-propofol combination (administration rate for each drug, 10.0 mg/kg/h [4.54 mg/lb/h]). Cats underwent ovariectomy; duration of infusion was 25 minutes. Physiologic variables were measured at predetermined time points. Heinz bodies were quantified via examination of blood smears. Numeric scales were used to assess quality of recovery, degree of sedation, and signs of pain after surgery.

RESULTS

The ketamine-propofol group had a significantly higher mean heart rate at several time points during drug infusion, a significantly shorter time from the end of infusion to extubation (7 vs 29 minutes), and significantly lower sedation scores for the first hour after surgery than did the ketamine-propofol-dexmedetomidine group. Other variables were similar between groups; recovery was smooth, and anesthesia and postoperative analgesia were deemed adequate for all cats. The number of RBCs with Heinz bodies was not increased after surgery, compared with values immediately after anesthetic induction.

CONCLUSIONS AND CLINICAL RELEVANCE

Total IV anesthesia with a ketamine-propofol combination, with or without dexmedetomidine, appeared to be effective in healthy cats. These short-term infusions produced smooth recovery and adequate analgesia during the postoperative period.

Effects of remifentanil infusion regimens on cardiovascular function and responses to noxious stimulation in propofol-anesthetized cats

OBJECTIVE

To evaluate the effects of 2 remifentanil infusion regimens on cardiovascular function and responses to nociceptive stimulation in propofol-anesthetized cats.

ANIMALS

8 adult cats.

PROCEDURES

On 2 occasions, cats received acepromazine followed by propofol (6 mg/kg then 0.3 mg/kg/min, i.v.) and a constant rate infusion (CRI) of remifentanil (0.2 or 0.3 microg/kg/ min, i.v.) for 90 minutes and underwent mechanical ventilation (phase I). After recording physiologic variables, an electrical stimulus (50 V; 50 Hz; 10 milliseconds) was applied to a forelimb to assess motor responses to nociceptive stimulation. After an interval (> or = 10 days), the same cats were anesthetized via administration of acepromazine and a similar infusion regimen of propofol; the remifentanil infusion rate adjustments that were required to inhibit cardiovascular responses to ovariohysterectomy were recorded (phase II).

RESULTS

In phase I, heart rate and arterial pressure did not differ between remifentanil-treated groups. From 30 to 90 minutes, cats receiving 0.3 microg of remifentanil/kg/min had no response to noxious stimulation. Purposeful movement was detected more frequently in cats receiving 0.2 microg of remifentanil/kg/min. In phase II, the highest dosage (mean +/- SEM) of remifentanil that prevented cardiovascular responses was 0.23 +/- 0.01 microg/kg/min. For all experiments, mean time from infusion cessation until standing ranged from 115 to 140 minutes.

CONCLUSIONS AND CLINICAL RELEVANCE

Although the lower infusion rate of remifentanil allowed ovariohysterectomy to be performed, a CRI of 0.3 microg/kg/min was necessary to prevent motor response to electrical stimulation in propofol-anesthetized cats. Recovery from anesthesia was prolonged with this technique.

Comparison of the cardiopulmonary effects of anesthesia maintained by continuous infusion of ketamine and propofol with anesthesia maintained by inhalation of sevoflurane in goats undergoing magnetic resonance imaging

OBJECTIVE

To compare the cardiopulmonary effects of anesthesia maintained by continuous infusion of ketamine and propofol with anesthesia maintained by inhalation of sevoflurane in goats undergoing magnetic resonance imaging.

ANIMALS

8 Saanen goats.

PROCEDURES

Goats were anesthetized twice (1-month interval) following sedation with midazolam (0.4 mg/kg, IV). Anesthesia was induced via IV administration of ketamine (3 mg/kg) and propofol (1 mg/kg) and maintained with an IV infusion of ketamine (0.03 mg/kg/min) and propofol (0.3 mg/kg/min) and 100% inspired oxygen (K-P treatment) or induced via IV administration of propofol (4 mg/kg) and maintained via inhalation of sevoflurane in oxygen (end-expired concentration, 2.3%; 1X minimum alveolar concentration; SEVO treatment). Cardiopulmonary and blood gas variables were assessed at intervals after induction of anesthesia.

RESULTS

Mean +/- SD end-expired sevoflurane was 2.24 +/- 0.2%; ketamine and propofol were infused at rates of 0.03 +/- 0.002 mg/kg/min and 0.29 +/- 0.02 mg/kg/min, respectively. Overall, administration of ketamine and propofol for total IV anesthesia was associated with a degree of immobility and effects on cardiopulmonary parameters that were comparable to those associated with anesthesia maintained by inhalation of sevoflurane. Compared with the K-P treatment group, mean and diastolic blood pressure values in the SEVO treatment group were significantly lower at most or all time points after induction of anesthesia. After both treatments, recovery from anesthesia was good or excellent.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that ketamine-propofol total IV anesthesia in goats breathing 100% oxygen is practical and safe for performance of magnetic resonance imaging procedures.

Infusão contínua de propofol em gatos pré-medicados com cetamina-midazolam

Estudaram-se os efeitos anestésicos e cardiorrespiratórios produzidos pela infusão contínua de propofol em gatos pré-medicados com a associação cetamina-midazolam. Catorze gatos adultos foram igualmente distribuídos em dois grupos (TX1 e TX3) aos quais administraram-se, pela via intramuscular, cetamina (3,0mg/kg) e midazolam (0,3mg/kg). Decorridos cinco minutos procedeu-se a indução anestésica pela administração intravenosa de propofol (5,0mg/kg), imediatamente seguida pela infusão contínua do agente hipnótico nas doses de 0,1 ou 0,3mg/kg/min, aos animais de TX1 e TX3, respectivamente. Foram mensuradas as freqüências cardíaca e respiratória, temperatura retal, saturação de oxihemoglobina, concentração exalada de dióxido de carbono e pressão arterial. Em TX3 observou-se manutenção de adequado plano anestésico, enquanto que os animais do TX1 apresentaram-se sedados. Houve decréscimo acentuado da freqüência cardíaca, pressão arterial e elevação da concentração de dióxido de carbono exalado no TX3. Conclui-se que o emprego de propofol na dose de infusão de 0,3mg/kg/min em gatos pré-medicados com cetamina-midazolam produz anestesia satisfatória, bradicardia, depressão da função respiratória e pressão arterial.