Partial intravenous anesthesia with dexmedetomidine-propofol in a 13-year-old Mangalarga horse undergoing herniorrhaphy with polypropylene mesh - case reportABSTRACT
The presented case was performed in a veterinary teaching hospital, observing the hemodynamic stability and recovery score of an adult horse after three hours of herniorrhaphy with polypropylene mesh using propofol. Pre-anesthetic medication was administered with detomidine (15µg/kg), followed by anesthetic induction with ketamine (2mg/kg) and midazolam (0.05mg/kg). General anesthesia was maintained with propofol (0.005-0.1mg/kg/min) and isoflurane (0-0.5%). Analgesic infusions of ketamine (0.6mg/kg/hr), lidocaine (1-3mg/kg/hr), and dexmedetomidine (0.25-0.5µg/kg/hr) were administered. A unilateral transversus abdominis plane (TAP) block was performed using a two-point approach with 2% lidocaine without vasoconstrictor (0.05mL/kg/point) and dexmedetomidine (0.25µg/kg/point). The animal achieved good cardiorespiratory stability during the procedure under spontaneous ventilation and a satisfactory recovery, assuming a quadrupedal position within 58 minutes without the need for external assistance. The use of a multimodal protocol allowed for dose adjustments to avoid significant respiratory depression, although maintenance was primarily performed with propofol.
Keywords:
α2-adrenergic agonists; equine; PIVA; TIVA; TAP block
RESUMO
O presente caso foi realizado dentro de um hospital escola, observando-se a estabilidade hemodinâmica e o escore de recuperação do animal após três horas de procedimento cirúrgico com o uso de propofol. Foi realizada medicação pré-anestésica com detomidina (15µg/kg), indução anestésica com cetamina (2mg/kg) e midazolam (0,05mg/kg), sendo a anestesia geral mantida com propofol (0,005-0,1mg/kg/min) e isoflurano (0-0,5%). Além disso, foram realizadas infusões analgésicas de cetamina (0,6mg/kg/h), lidocaína (1-3mg/kg/h) e dexmedetomidina (0,25-0,5µg/kg/h). Também foi realizado bloqueio do plano transverso do abdômen (TAP block) unilateral, na abordagem de dois pontos, com lidocaína 2% sem vasoconstritor (0,05mL/kg/ponto) e dexmedetomidina (0,25µg/kg/ponto), obtendo-se boa estabilidade cardiorrespiratória durante o procedimento, sob ventilação espontânea, e recuperação considerada satisfatória, com o animal assumindo posição quadrupedal em até 58 minutos, sem necessidade de auxílio externo. O uso de um protocolo multimodal permitiu a adequação das doses, de forma a não promover grandes depressões respiratórias no animal, apesar de a manutenção ser primariamente realizada com propofol.
Palavras-chave:
agonistas α2-adrenérgicos; equinos; PIVA; TIVA; TAP block
INTRODUCTION
Anesthetic maintenance in prolonged surgical procedures in adult horses, especially in cases where laparotomies are necessary, represents a considerable anesthetic challenge (Laurenza et al., 2020). Among intravenous agents, propofol stands out for its reduced context-sensitive half-life and absence of active metabolites, promoting rapid and high-quality anesthetic recovery (Otsuka et al., 2024). However, its isolated use may not be satisfactory during major interventions, such as abdominal herniorrhaphy.
In this context, the association of adjuvant drugs in continuous infusion has been proposed as a strategy to improve the anesthetic-analgesic balance. Protocols that combine α2-adrenergic agonists, ketamine, and lidocaine demonstrate synergistic potential, with benefits that include cardiovascular and respiratory stability. Dexmedetomidine, an α2 adrenergic agonist, contributes to sedation, muscle relaxation, analgesia and a propofol-sparing effect, causing cell hyperpolarization and reducing central nervous system excitability; ketamine, by antagonizing N-methyl-D-aspartate (NMDA) receptors, exhibits sympathetic activity that leads to increased cardiac output, blood pressure, and heart rate (Wong & Jenkins 1974); and lidocaine, in addition to its systemic analgesic properties, can exert prokinetic and anti-inflammatory effects, favoring postoperative recovery (Murrell et al., 2005).
Additionally, locoregional techniques, such as the transverse abdominal plane block (TAP block), are valuable as part of a multimodal protocol, providing sensory blockade of the thoracic and lumbar branches of the spinal nerves that innervate the skin, abdominal wall muscles, and parietal peritoneum (Baldo et al., 2018) and reducing the need to deepen the plane or increase systemic analgesia during surgical manipulation.
This report describes the use of a combined anesthetic protocol, using propofol and isoflurane for maintenance, associated with continuous infusion of dexmedetomidine, ketamine, and lidocaine, in a horse undergoing abdominal herniorrhaphy with polypropylene mesh, focusing on hemodynamic parameters, quality of recovery, and perioperative analgesia.
ETHICAL ASPECTS
This research was not submitted to the Ethics Committee on Animal Use.
CASUISTRY
A thirteen-year-old male Mangalarga horse, weighing 460kg, was treated for an increased volume in the abdominal region of the rectus abdominis muscle, which had been present for a year. The swelling was caused by a cow goring, leaving the muscles weakened. Over the months, the swelling increased and its performance decreased, therefore the animal was taken to the veterinary teaching hospital for treatment. During the consultation, the animal showed no abnormalities on physical examination. Ultrasound examination was performed, which revealed fluid and intestines with normal peristalsis, confirming a hernia, and thus the animal was referred to for surgical procedure. On the surgery day, venous access was performed via jugular vein using a 16-gauge catheter. Preoperative tests showed values of creatinine of 2.07mg/dL (above the normal range of 0.9-1.47mg/dL for adult horses) and gamma-glutamyl transferase (GGT) of 37.4U/L (above reference range for adult horses of 6-30 U/L). Other parameters remained within normal limits (Sommardahl, 2022).
Detomidine 15ug/kg/IV was administered as pre-anesthetic medication given the animal's agitated behavior. When an adequate level of sedation was observed (horses with EquiSed scores>7) (Oliveira et al., 2021), ketamine 2mg/kg/IV was administered in combination with midazolam 0.05mg/kg/IV. After gentle induction, a bolus of propofol at a dose of 0.5mg/kg/IV was administered to facilitate orotracheal intubation using a 22mm tube covered distally with lidocaine gel.
After intubation, the animal was positioned on the surgical table in lateral recumbency and placed on a closed HB® circuit saturated with oxygen 5-8L/min, isoflurane (Isoflurano Syntec®) was used in times at 0.5% in a HB® calibrated vaporizer and propofol at 0.005-0.1mg/kg/min (total volume of 720mL), maintaining spontaneous ventilation. Simultaneously, dexmedetomidine 0.25-0.5ug/kg/hr, lidocaine 1-3mg/kg/hr, and ketamine (Ketalex®) 0.6mg/kg/hr were infused, with doses adjusted as needed to maintain the patient's anesthetic depth, but remaining at minimal doses.
Extensive trichotomy of the surgical region was performed, followed by prior cleaning and antisepsis with 2% chlorhexidine and alcohol. Unilateral two-points approach TAP block was performed using ultrasound guidance, with a combination of lidocaine 0.05mL/kg/point and dexmedetomidine 0.25ug/kg/point seeking to maximize the latency period of lidocaine, due to the absence of bupivacaine or ropivacaine at the time of the procedure.
The procedure lasted three hours, during which the patient remained stable, with a heart rate ranging from 26-38 bpm, respiratory rate of 8-16 rpm, end-tidal carbon dioxide concentration (ETCO2)<60mmHg, sistolic arterial pressure of 100-120 mmHg, temperature of 36.9-37.4°C, capillary refill time of 2 sec, and pink mucous membranes. Surgical access was abdominal, using the open herniorrhaphy technique. An elliptical incision was made around the hernial sac, then the subcutaneous tissue was dissected around the sac and the hernial ring. Finally, the hernial sac was opened, giving access to the abdominal cavity, where the intestines were intact, there was a lot of fat, and the musculature was very thick, which made complete closure difficult. Everything was repositioned and closure was initiated. A polypropylene mesh was placed in the second muscle layer to prevent recurrence, since the muscle and aponeurosis were approximated with sultan using 0.50 nylon and were under a lot of tension, therefore the mesh was fixed with simple interrupted sutures. Then the subcutaneous tissue was closed with Cushing's suture and using 2-0 synthetic absorbable suture. At the end of the procedure, the skin was closed with non-absorbable suture and Wolff stitch.
The infusions were discontinued with proper weaning at the beginning of the dermorrhaphy, a bolus of 2% xylazine was given at a dose of 0.2mg/kg/IV and the animal was taken to the anesthetic recovery room. It showed a swallowing reflex and was extubated after 10 minutes, assumed sternal recumbency in 22 minutes and quadrupedal position in 58 minutes, without any external assistance. Recovery was considered satisfactory (Valverde et al., 2013).
The animal returned to grazing 30 minutes after anesthetic recovery, showing no signs of pain. Gentopen® BID (every twelve hours), for five days (gentamicin 3.3mg/kg and potassium benzylpenicillin 30.000 IU/kg/IV) and flunixin meglumine SID (every twenty-four hours), for three days (Flumax®, 1.1mg/kg) were administered post-operatively, as well as daily wound cleaning with chlorhexidine and saline solution. The animal used compression bandage post operative, being discharged from the hospital in two weeks.
DISCUSSION
Although propofol is known for its respiratory depression, no episodes of apnea or bradypnea occurred during induction or maintenance of the animal, maintaining normal respiratory rate, adequate chest expansion and ETCO2 < 60 mmHg during the procedure, nor was it necessary to substantially increase doses to keep the animal in the surgical plane, as no positive response to painful stimuli was assessed at any point during or after the herniorrhaphy.
A combination of dexmedetomidine, ketamine, and lidocaine infusions, along with maintenance of the anesthetic plane using propofol and isoflurane together, proved satisfactory for a horse undergoing abdominal open herniorrhaphy technique when dosed right. Similarly, the TAP block with lidocaine and dexmedetomidine promoted adequate desensitization of the abdominal wall during the procedure, complementing the stability of the protocol without significant parameter alterations. This was possibly also due to the pharmacological combination allowing for a reduction in doses and adverse effects of each drug. Proper weaning from the infusions was also ideal for recovery with minimal ataxia.
REFERENCES
- BALDO, C.F.; ALMEIDA, D.; WENDT-HORNICKLE, E.; GUEDES, A. Transversus abdominis plane block in ponies: a preliminary anatomical study. Vet. Anaesth. Analg, v.45, p.392-396, 2018.
- LAURENZA, C.; ANSART, L.; PORTIER, K. Risk factors of anesthesia-related mortality and morbidity in one equine hospital: a retrospective study on 1,161 cases undergoing elective or emergency surgeries. Front. Vet. Sci, v.6, p.514, 2020.
- MURRELL, J.C.; WHITE, K.L.; JOHNSON, C.B. et al Investigation of the EEG of intravenous lidocaine during halothane anaesthesia in ponies. Vet. Anaesth. Analg, v.32, p.212-221, 2005.
- OLIVEIRA, A.R.D.; GOZALO-MARCILLA, M.; RINGER, S.K. et al Development, validation, and reliability of a sedation scale in horses (EquiSed). Front. Vet. Sci, v.8, p.611729, 2021.
- OTSUKA, T.; ARAKI, M.; MITA, H. et al Total intravenous anesthesia with propofol-ketamine-xylazine with or without remifentanil in thoroughbred horses undergoing castration. J. Equine Sci, v.35, p.35-41, 2024.
- SOMMARDAHL, C. Manual of equine anesthesia and analgesia Oxford, UK: Blackwell Publishing, 2022. p.8-18.
- VALVERDE, A.; BLACK, B.; CRIBB, N.C. et al Assessment of unassisted recovery from repeated general isoflurane anesthesia in horses following post-anesthetic administration of xylazine or acepromazine or a combination of xylazine and ketamine. Vet. Anaesth. Analg, v.40, p.3-12, 2013.
- WONG, D.H.; JENKINS, L.C. An experimental study of the mechanism of action of ketamine on the central nervous system. Can. Anaesth. Soc. J, v.21, p.57-67, 1974.
The research data are available within the article itself.
