Total intravenous anesthesia for laparoscopic portosystemic shunt repair in a dog - case report

[Anestesia total intravenosa para reparação laparoscópica de shunt portossistêmico em cão - relato de caso]

ABSTRACT

An anomalous venous communication between the systemic and portal circulations characterizes a portosystemic shunt. Surgery is the gold standard treatment, and the laparoscopic approach is a growing option for correcting these anomalies. The need for pneumoperitoneum, sometimes associated with controlled ventilation, in patients with altered liver function implies a careful choice of anesthetic techniques. Total intravenous anesthesia has favorable characteristics, including independence from alveolar ventilation for anesthetic effects and the possibility of pharmacological associations with favorable metabolic and analgesic profiles. A 2-year-old Pinscher underwent laparoscopic surgery under total intravenous anesthesia for the occlusion of an extrahepatic portosystemic shunt with an ameroid ring constrictor. The drugs of choice for anesthetic maintenance were propofol, remifentanil, and ketamine administered via continuous infusion. Multimodal analgesia has proven to be efficient in reducing the rate of propofol required, providing satisfactory physiological stability during anesthesia, and smooth recovery, without signs of pain, vocalization, or nausea. In conclusion, total intravenous anesthesia was effective for laparoscopic surgery in the treatment of the dog with portosystemic shunt.

Keywords:
TIVA; video surgery; continuous infusion; pneumoperitoneum; balanced anesthesia

RESUMO

O shunt portossistêmico representa uma comunicação venosa anômala entre a circulação sistémica e a circulação portal. A cirurgia é o tratamento padrão, e a abordagem laparoscópica é uma opção crescente para a correção dessa anomalia. A necessidade de pneumoperitônio, por vezes associado à ventilação controlada, em doentes com função hepática alterada, implica na escolha criteriosa da técnica anestésica. A anestesia total intravenosa tem características favoráveis, notadamente a independência da ventilação alveolar para efeitos anestésicos e a possibilidade de associações farmacológicas com perfis metabólicos e analgésicos favoráveis. Um Pinscher de dois anos de idade foi submetido à cirurgia laparoscópica sob anestesia intravenosa total para a oclusão de um shunt portossistêmico extra-hepático com um anel constritor ameroide. Os fármacos de eleição para a manutenção anestésica foram o propofol, o remifentanil e a cetamina, administrados por infusão contínua. A analgesia multimodal mostrou-se eficiente na redução da taxa de propofol necessária, proporcionando estabilidade fisiológica satisfatória durante a anestesia e recuperação tranquila, sem sinais de dor, vocalização ou náusea. Em conclusão, a anestesia intravenosa total foi eficaz e segura para a cirurgia laparoscópica no tratamento do cão com shunt portossistêmico.

Palavras-chave:
AIVT; videocirurgia; infusão contínua; pneumoperitôneo; anestesia balanceada

INTRODUCTION

A congenital portosystemic shunt (PSS) is characterized by a detour of blood flow from the liver through abnormal venous communication between the portal and systemic circulation. Vessels of this nature allow venous blood drained from the gastrointestinal (GI) tract, pancreas, and spleen to bypass the liver and enter the systemic circulation directly. As a result, various toxins, including ammonia, are not metabolized, and some trophic factors in the GI tract and pancreas do not reach the liver, leading to parenchymal atrophy, decreased liver function and protein synthesis, and eventual liver failure. Extrahepatic PSS (66-75%) is more commonly diagnosed in small and toy-breed dogs and cats, whereas intrahepatic PSS (25-33%) is more widely observed in large-breed dogs (Konstantinidis et al., 2023). Surgical treatment involves shunt occlusion, and the use of an ameroid ring constrictor for gradual attenuation has been shown to be adequate and safe (Brun et al., 2022). Laparoscopic surgery in dogs has advantages over open surgery, including image magnification, reduced postoperative pain, and increased postoperative activity (Poggi et al., 2022). However, it requires the installation of a pneumoperitoneum, which results in physiological repercussions depending on the required intra-abdominal pressure (IAP) (Miller, 2016). General anesthesia is usually recommended for the procedure as it provides a safe airway, allows controlled mechanical ventilation with adequate management of CO₂ absorption induced by the pneumoperitoneum, and facilitates the management of muscle relaxation necessary to optimize surgical vision. Total intravenous anesthesia (TIVA) is a technique in which the induction and maintenance of anesthesia are performed by the intravenous administration of drugs. In human and veterinary anesthesiology, the use of this modality has increased significantly because of its advantages such as rapid onset of action independent of alveolar ventilation, smooth recovery, absence of environmental pollution, and the possibility of a precise combination of drugs with favorable metabolization profiles (Nadri et al., 2021; Sarturi et al., 2021). This study aimed to provide an unprecedented description of the TIVA technique for the laparoscopic correction of a PSS in a Pinscher, considering the peculiarities inherent to the disease and the chosen surgical technique.

CASUISTRY

A two-year-old male Pinscher, weighing 2.6kg, was admitted to the Veterinary Teaching Hospital (Federal University of Bahia, Salvador, Brazil). The person responsible reported the onset of neurological symptoms seven months previously (seizures and syncope), as well as frequent vomiting, hyporexia, and progressive weight loss. A physical examination revealed disorientation and ataxia. Laboratory tests revealed the following changes: hypocholesterolemia (88mg/dL), hypoproteinemia (5.2g/dL), hypoalbuminemia (2.4g/dL) with elevated serum alanine aminotransferase (ALT) (190,6IU/L), alkaline phosphatase (ALP) (633.6IU/L), and reduced urea (14.6mg/dL), as well as ammonium biurate crystals in the urine (+++). Abdominal ultrasonography revealed a small mass in the liver, but the diagnosis of extrahepatic PSS was confirmed using computed tomography. After confirmation of PSS, the patient was referred for surgical correction by implantation of an ameroid constrictor ring to occlude the shunt using video-laparoscopy.

The dog was pre-medicated with methadone hydrochloride (0.4mg/kg) (Mytedom®, Cloridrato de metadona®, Cristália, Brazil) intramuscularly (IM). Catheters were implanted in the right and left cephalic veins. To induce anesthesia, midazolam (0.2mg/kg) (Dormonid®, Cloridrato de midazolam, Roche, Brazil) was administered into the right cephalic vein, followed by propofol (3.8mg/kg - total dose) (Propovan®, Propofol Cristália, Brazil) until endotracheal intubation with a polyvinyl chloride probe with a 4 mm cuff was possible after the swallowing reflex was lost. The animal was maintained under TIVA with propofol (0.3mg/kg/min - initial rate), remifentanil hydrochloride (10mcg/kg/h) (Remifas®, Cloridrato de remifentanil, Cristália, Brazil), and ketamine hydrochloride (0.4mg/kg/h) (Ketamin®, Cloridrato de escetamina, Cristália, Brazil) administered using syringe pumps (Injectomat Agilia®, Fresenius Kabi, France). After intubation, mechanical ventilation (DL728®, Deltalife, Brazil) was initiated in assist-control mode with an FiO₂ of 1.0 to maintain end-tidal carbon dioxide (EtCO₂) within the desired range (35-45mmHg). During anesthesia, fluid therapy was administered at a rate of 3mL/kg/h (Solução de Ringer com lactato; Eurofarma, Brazil). Fifteen minutes after anesthesia induction, the video surgical procedure was initiated with CO₂ pneumoperitoneum at a pressure of 8mmHg. Three triangulated trocars (two 10mm and one 5mm) were inserted into the right flank. The extrahepatic shunt was identified and dissected, followed by the fitting of a 0.5mm ameroid ring (Figure 1) and its fixation with polypropylene through two pre-realized perforations (Brun et al., 2022). A liver biopsy was performed, and access incisions to the trocars were occluded. During the procedure, the anesthesia plan was assessed at 10-min intervals and was considered adequate (mild to moderate) when there was no eyelid reflex, slight mandibular tone, and no voluntary movements. The propofol infusion rate was reduced by 20% if the anesthetic plane was considered to be excessive and increased by 20% if anesthetic level was judged insufficient (Bustamante et al., 2020). After adjustment, the infusion rate was maintained for 10 min before any further changes. Physiological parameters were continuously monitored and recorded every five min by using a multiparameter monitor (Dixtal Efficia CM 100®; Philips Dixtal, China). Twenty minutes after the start of the surgical procedure, the animal showed a 55% reduction (93 to 41bpm) in baseline heart rate (HR). The bradycardia was quickly reversed with intravenous atropine (0.044mg/kg) and subsequently, the requirement of propofol decreased. After 30 min of surgery, hypotension was recorded (85mmHg systolic blood pressure (SBP); 52mmHg mean arterial pressure (MAP) and 36mmHg diastolic blood pressure (DBP), which was controlled with continuous infusion of noradrenaline (Epikabi®, hemitartarato de norepinefrina, Fresenius Kabi, Brazil) at a rate of 0.1mcg/kg/h using an infusion pump (ST 680®; Samtronic, São Paulo, Brazil) until end of the procedure. The following mean values were recorded during anesthesia: HR 82±14bpm, respiratory rate (RR) 12±1.8bpm, oxygen saturation (SpO₂) 98±0.8%, EtCO₂ 42±4 mmHg, SBP 102±20.2mmHg, MAP 78±22.4 mmHg, and DBP 61 ± 23.4mmHg, and esophageal temperature (T°C) 37.5±0.6°C. Surgical procedure lasted 65 min when the infusions were stopped. Flumazenil (Flumazil®, Flumazenil, Cristália, Brazil) (0.01mg/kg, IV) and meloxicam (Maxicam 0.2%®, Meloxicam, Ouro fino, Brazil) (0.1mg/kg) were then administered. The mean infusion rate of propofol required for anesthetic maintenance was 0.14±0.07mg/kg/min. Times to extubation and raise the head was 12 and 25 min after the end of anesthesia, respectively. The patient showed consciousness at 80 min without signs of pain, excitement, or discomfort. On returning to the clinic after ten days, the guardian reported normal behavior, adequate food and water intake and denied any neurological signs. On physical examination, the animal was alert and oriented (Glasgow 15), presenting normal physiological parameters.

Figure 1
Occlusion of the extrahepatic systemic port shunt with an ameroid ring constrictor in a Pinscher dog under total intravenous anesthesia.

DISCUSSION

Surgical occlusion of PSS is considered the definitive treatment for dogs and cats, and in veterinary medicine, open techniques are primarily used in which the abdomen is explored using a ventral midline celiotomy. Minimally invasive techniques have advantages, such as image magnification and faster recovery associated with less pain (Poggi et al., 2022). However, to our knowledge, few reports have described laparoscopic approaches to congenital extrahepatic PSS in dogs, and all under general inhalation anesthesia (Miller and Fowler, 2006; Brun et al., 2022; Park et al., 2022; Poggi et al., 2022). An important feature of laparoscopic techniques is the need to establish pneumoperitoneum with carbon dioxide (CO₂) to obtain the operative tent, which can result in significant cardiorespiratory changes depending on certain factors, such as the required IAP.

In dogs with liver disease, signs of hepatic encephalopathy and alterations such as hyperbilirubinemia, hypoalbuminemia and coagulopathies are associated with greater severity (Konstantinidis et al., 2023). In this report, hyperbilirubinemia and hypoalbuminemia were found, as well as hypercholesterolemia, high serum ALT and AF concentrations, low urea concentrations, and the presence of ammonium biurate crystals in the urine. Based on the above, the choice of anesthetic modality for the case presented here was considered, especially because of the hepatopathy and possible cardiorespiratory repercussions of pneumoperitoneum linked to the video-assisted approach. The independence of alveolar ventilation for anesthetic titration and the favorable pharmacokinetic characteristics of propofol make TIVA a growing option in laparoscopic procedures (Nadri et al., 2021; Sarturi et al., 2021). Propofol has a similar half-life in cirrhotic patients, but its dosage should be titrated due to increased sensitivity to its cardiorespiratory depressant effect (Chan et al., 2020).

For premedication, methadone was chosen because of its sedative and analgesic properties. In humans, a study found no effect of the degree of liver fibrosis on serum methadone concentrations (Chalabianloo et al., 2023). In addition, methadone was used before and after surgical occlusion of the PSS in 34 dogs of various breeds with no reported adverse effects (Kummeling et al., 2006).

In patients with liver disease, propofol is the anesthetic agent of choice because of its favorable pharmacokinetic profile, which includes rapid redistribution and multiple sites of metabolization. However, it is associated with dose-dependent cardiorespiratory depression and vasodilator action, which can reduce liver perfusion (Starczewska et al., 2017). To reduce the total dose of propofol and ensure greater cardiorespiratory stability, midazolam was administered before propofol. Despite its primary hepatic metabolism, midazolam has a shorter action time than diazepam and a lower cumulative effect. Based on the literature, it can be said that in this case it was possible to induce anesthesia with a low dose of propofol (3.8mg/kg), excluding immediate depressant effects on respiratory rate, EtCO₂ and SpO₂ (Aguilera et al., 2020). Owing to the relevant pharmacological characteristics of propofol, it was used as a maintenance anesthetic in continuous infusion. Studies have reported the superiority of intravenous anesthesia over inhalation techniques in human patients undergoing laparoscopic procedures. During laparoscopic cholecystectomy, propofol causes fewer hemodynamic changes than isoflurane, providing greater stability during anesthesia (Nadri et al., 2021). For the same surgical procedure, TIVA with propofol and alfentanil was associated with a significantly reduced rate of postoperative nausea and vomiting, consumption of analgesics, shorter recovery time and length of hospital stay, accelerated onset of bowel movements, and greater patient satisfaction than desflurane and alfentanil (Akkurt et al., 2009). In this report, remifentanil and ketamine were used concurrently in continuous infusion to reduce the propofol requirements and to provide analgesia with greater cardiorespiratory stability. Remifentanil has an ester bond that allows its degradation by plasma cholinesterases, resulting in reasonably predictable pharmacokinetics that do not depend on liver or kidney function for its elimination. It has a significant volatile anesthetic-sparing effect; however, it is a potent respiratory depressant (Allweiler et al., 2007). Ketamine, an NMDA antagonist, reduces central pain sensitivity at sub-anesthetic doses with minimal physiological impact. In humans undergoing elective laparoscopic surgery, the combination of ketamine-propofol for induction of anesthesia promoted better hemodynamic stability compared to the use of propofol alone, but resulted in increased recovery time (Raman et al., 2022). In female dogs undergoing laparoscopic ovariectomy, the effects of TIVA with propofol (0.4mg/kg/min) associated with ketamine (2mg/kg followed by 6mg/kg/h), S-ketamine (1mg/kg followed by 3mg/kg/h), or remifentanil (1mcg/kg followed by 12mcg/kg/h) were evaluated. In all treatments, a continuous increase in EtCO₂ was detected despite maintaining the animals on volume-controlled ventilation. There was an increase and decrease in HR in the groups treated with ketamine and remifentanil, respectively, but there were no repercussions on cardiac output. The authors concluded that the tested protocols showed satisfactory results and hemodynamic stability (Sarturi et al., 2021).

In this case, cardiorespiratory monitoring revealed bradycardia occurring 20 min after the initiation of the surgical procedure. As reported by Schug et al. (1992), a combination of drugs may potentiate the vagotonic effects of methadone and remifentanil. In addition to atropine treatment, sequential reduction in the rate of propofol administration ensured variable stability. However, despite maintaining an adequate anesthetic plan, hypotension was detected 30 min after surgery. In addition to the drugs propofol, methadone, and remifentanil that reduce peripheral vascular resistance (Aguilera et al., 2020; Schug et al., 1992), pneumoperitoneum (Miller, 2016) and mechanical ventilation (Luecke et al., 2007) stand out among the factors that depress cardiovascular function. Since the magnitude of cardiorespiratory changes associated with CO₂ pneumoperitoneum is directly related to high IAP (> 12 mmHg) and consequent hypercarbia (Miller, 2016), the use of an IAP of 8 mmHg in the proposed innovative technique certainly resulted in milder physiological repercussions. Mechanical ventilation in the assist-control mode has made it possible to maintain acceptable levels of exhaled CO₂ without using neuromuscular blockers. The ventilator’s low sensitivity permits patient-initiated breaths, facilitating interaction. Assist-control modes are generally associated with fewer cardiovascular effects than controlled mechanical ventilation modes (Luecke et al., 2007). Hypotension was treated with norepinephrine, which has favorable metabolic characteristics.

Following these considerations, the animal remained stable throughout the laparoscopic procedure, ruling out any relevant physiological changes. The low mean infusion rate of propofol required to maintain the anesthetic plan demonstrates the significant sedative and analgesic contributions of remifentanil and ketamine infusions. It is worth noting that, given the metabolic profile of ketamine, a lower rate was administered (Sarturi et al., 2021), so as not to significantly increase the recovery period time (Raman et al., 2022). Since the animal raised its head approximately 25 min after the end of anesthesia and showed consciousness at 80 min without signs of pain, excitement, or discomfort, the recovery characteristics confirmed the success of the proposed protocol.

CONCLUSION

To our knowledge, this is the first report of total intravenous anesthesia in a dog undergoing the correction of a congenital extrahepatic portosystemic shunt. Considering the particularities inherent to hepatopathy and video-laparoscopic surgery, and despite the minor complications during anesthesia, it can be concluded that total intravenous anesthesia with propofol, remifentanil, and ketamine was effective. This pioneering report may contribute to future studies on the use of this anesthetic modality in laparoscopic surgery for dogs with portosystemic shunts.

REFERENCES

• AGUILERA, R.; SINCLAIR, M.; VALVERDE, A. et al. Dose and cardiopulmonary effects of propofol alone or with midazolam for induction of anesthesia in critically ill dogs. Vet. Anaesth. Analg., v.47, p.472-480, 2020.
• AKKURT, B.C.O.; TEMIZ, M.; INANOGLU, K. et al. Comparison of recovery characteristics, postoperative nausea and vomiting, and gastrointestinal motility with total intravenous anesthesia with propofol versus inhalation anesthesia with desflurane for laparoscopic cholecystectomy: a randomized controlled study. Curr. Ther. Res., v.70, p.94-103, 2009.
• ALLWEILER, S.; BRODBELT, D.C.; BORER, K. et al. The isoflurane-sparing and clinical effects of a constant rate infusion of remifentanil in dogs. Vet. Anaesth. Analg., v.34, p.388-393, 2007.
• BRUN, M.V.; PASQUALE, R.; ANTUNES, B.N. et al. Totally laparoscopic treatment of a single extrahepatic portosystemic shunt in dogs with an ameroid constrictor. Vet. Surg., v.51, p.12-24, 2022.
• BUSTAMANTE, R.; SEGURA, I.A.G.; CANFRÁN, S.; AGUADO, D. Effects of ketamine or midazolam continuous rate infusions on alfaxalone total intravenous anaesthesia requirements and recovery quality in healthy dogs: a randomized clinical trial. Vet. Anaesth. Analg., v.47, p.437-446, 2020.
• CHALABIANLOO, F.; HØISETH, G.; VOLD, J.H. et al. Impact of liver fibrosis and clinical characteristics on dose-adjusted serum methadone concentrations. J. Addict. Dis., v.41, p.53-63, 2023.
• CHAN, M.; SO, V.; IRWIN, M.G. Clinical aspects of hepatic disease. Anaesth. Intens. Care Med., v.21, p.498-502, 2020.
• KONSTANTINIDIS, A.O.; PATSIKAS, M.N.; PAPAZOGLOU, L.G. et al. Congenital portosystemic shunts in dogs and cats: classification, pathophysiology, clinical presentation and diagnosis. Vet. Sci., v.10, p.160, 2023.
• KUMMELING, A.; TESKE, E.; ROTHUIZEN, J. et al. Coagulation profiles in dogs with congenital portosystemic shunts before and after surgical attenuation. J. Vet. Intern. Med., v.20, p.1319-1326, 2006.
• LUECKE, T.; PELOSI, P.; QUINTEL, M. Haemodynamic effects of mechanical ventilation. Anaesthesist, v.56, p.1242-1251, 2007.
• MILLER, C. Anaesthetic considerations for laparoscopic surgery in canines. Vet. Times, p.1-6, 2016.
• MILLER, J.M.; FOWLER, J.D. Laparoscopic portosystemic shunt attenuation in two dogs. JAAHA., v.42, p.160-164, 2006.
• NADRI, S.; KARIMI, A.; MOHAMMADI, F. et al. A randomized controlled trial evaluating inhalation and intravenous anesthesia for laparoscopic cholecystectomy. Int. J. Surg. Open., v.28, p.1-7, 2021.
• PARK, J.; JANG, K.; JO, H. et al. Laparoscopic attenuation of a congenital extrahepatic portosystemic shunt in a dog-a thin-film banding for splenophrenic shunt: a case report. Front. Vet. Sci., v.9, p.918153, 2022.
• POGGI, E.; RUBIO, D.G.; PÉREZ DUARTE, F.J. et al. Laparoscopic portosystemic shunt attenuation in 20 dogs (2018‐2021). Vet. Sur., v.51, p.O138-O149, 2022.
• RAMAN, V.; SEGARAN, S.; RAMYAVEL, T. et al. Comparison of haemodynamic changes between propofol and ketofol as induction agents in patients undergoing laparoscopic surgeries under general anaesthesia. J. Anaesthesiol. Clin. Pharmacol., v.38, p.215-220, 2022.
• SARTURI, V.Z.; TEIXEIRA, L.G.; CORADINI, G.P. et al. Total intravenous anesthesia with propofol associated or not with remifentanil, ketamine, or S-ketamine for lapa-roscopic ovariectomy in female dogs. Top. Comp., v.45, p.100575, 2021.
• SCHUG, S.A.; ZECH, D.; GROND, S. Adverse effects of systemic opioid analgesics. Drug Saf., v.7, p.200-213, 1992.
• STARCZEWSKA, M.H.; MON, W.; SHIRLEY, P. Anaesthesia in patients with liver disease. Curr. Opin. Anesthesiol., v.30, p.392-398, 2017.

Publication Dates

• Publication in this collection
  14 July 2025
• Date of issue
  Jul-Aug 2025

History

• Received
  30 Sept 2024
• Accepted
  19 Dec 2024