Letters to the Editor
drugs administered for sedation and not the ones administered epidurally. Systemic absorption of epidural xylazine in the sheep in this study was suggested by subsequent decreases in arterial oxygen tension (PaO2) and hemoglobin oxygen saturation (SpO2). However, the degree of sedation was not as severe as previously described (Kastner 2006). Also, the decrease in Hct was not more severe in this group compared to the others as we expected, suggesting that the systemic absorption of xylazine did not contribute to the Hct decrease. Although a discrepancy has been described between Hct obtained by i-STAT and the Hct obtained by laboratory analyzers (Peir o et al. 2010), our data were collected with only one technology (i-STAT), revealing only differences between treatments and a change in Hct over time. Acepromazine induces relaxation and vasodilation of the splenic capsule promoting sequestration of erythrocytes (Ambr osio et al. 2012). Nevertheless, a study in dogs showed no correlation between splenomegaly and decreased Hct, suggesting that the effect of the drug is not exclusively related to splenic size but also related to vascular smooth muscle within the splanchnic circulation (Wilson et al. 2004). Although the effect is known, there are few reports that objectively assess the magnitude of this reduction, especially in sheep. In horses sedated with acepromazine or xylazine and acepromazine, the Hct decreased 17% and 19%, respectively, and remained decreased for 180 minutes returning to baseline levels only 24 hours later (Ambr osio et al. 2012). The evaluation of the effect of acepromazine on Hct was not the goal of this study. Therefore, it is not known for what period of time the Hct remained low. In healthy animals, a moderate, sedative-induced reduction in Hct does not result in significant clinical effects. The significance of the information in this letter arises from the effects of these sedative drugs in animals with preexisting diseases of oxygen delivery, such as anemia. These patients are at greater risk for significant morbidity following sedation with acepromazine and diazepam. Further studies should be done assessing the effects of acepromazine on Hct in sheep in order to evaluate the onset of this effect, and the degree and duration of reduction. Ceci R Leite*, Fabio O Ascoli†, Juliana de Oliveira‡ & Felipe Z Brand~ao* *Department of Veterinary Pathology and Clinic, Fluminense Federal University, Niter oi, RJ,
Brazil,†Physiology Department, Fluminense Federal University, Niter oi, RJ, Brazil,‡Basic Science Department, Fluminense Federal University, Niter oi, RJ, Brazil E-mail: [email protected] References Ambrosio AM, Ida KK, Souto MTMR et al. (2012) Significant hematocrit decrease in healthy horses during clinical anesthesia. Braz J Vet Res Anim Sci 49, 139–145. Kastner SBR (2006) Alpha2-agonists in sheep: a review. Vet Anaesth Analg 33, 79–96. Leise BS, Fugler LA, Stokes AM et al. (2007) Effects of intramuscular administration of acepromazine on palmar digital blood flow, palmar digital arterial pressure, transverse facial arterial pressure, and packed cell volume in clinically healthy, conscious horses. Vet Surg 36, 717–723. Peir o JR, Borges AS, Goncßalves RC et al. (2010) Evaluation of a portable clinical analyzer for the determination of blood gas partial pressures, electrolyte concentrations, and hematocrit in venous blood samples collected from cattle, horses, and sheep. Am J Vet Res 71, 515–521. Wilson DV, Evans AT, Carpenter RA et al. (2004) The effect of four anesthetic protocols on splenic size in dogs. Vet Anaesth Analg 31, 102–108.
doi:10.1111/vaa.12222
All in a tangle: a mishap with an oesophagostomy tube in an intubated cat
We would like to report a case of entrapment of the pilot tube of an endotracheal tube (ETT) within an oesophagostomy tube loop. A one-year-old, 3.2 kg, female neutered Domestic Shorthair cat with multiple pelvic fractures post-road traffic accident was anaesthetized for fracture repair and oesophagostomy tube placement. Medetomidine [0.003 mg kg 1 (Sedator, Dechra Veterinary Products Limited, UK)] was administered intravenously (IV) for premedication, followed approximately 5 minutes later by propofol [16 mg IV (PropoFlo Plus, Abbott, UK)]. After endotracheal intubation with a 4 mm internal diameter cuffed
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 42, 226–231
227
Letters to the Editor
polyvinyl chloride endotracheal tube, anaesthesia was maintained with isoflurane (IsoFlo, Abbott, UK) in oxygen (O2) and the cat was allowed to breathe spontaneously throughout the procedure. Analgesia was provided, intraoperatively, with methadone, ketamine and fentanyl. At the end of the orthopaedic surgery, lasting approximately 210 minutes, the cat was taken to radiology, where, prior to taking post-operative radiographs, an oesophagostomy tube was placed. At the end of the procedure, and after the radiographs had been taken, isoflurane was discontinued. The cat was allowed to breathe 100% O2 while re-warming took place and until the palpebral reflex was present. The ETT was then disconnected from the anaesthetic circuit and the cat (still with the ETT in place) moved to the recovery area. When the cat started swallowing, the cuff of the ETT was deflated. An attempt to pull the ETT out from the oral cavity was made, but it could not be withdrawn. A bolus of propofol was administered IV in order to suppress the swallowing reflex and give more time for investigation. The oral cavity was examined using a laryngoscope. The pilot balloon of the ETT could be seen retreating into the oesophagus when any attempt at extubation was made. It was not possible to free the pilot balloon without pushing the ETT deeper through the larynx. Finally, we considered that the ETT pilot tube could have been entrapped in a loop of the oesophagostomy tube during the placement of the latter. Normally, during placement of an oesophagostomy tube, the tube is withdrawn into the mouth from its initial insertion site in the cervical oesophageal region and redirected caudally into the oesophagus. We think this is where the entrapment could have occurred. The pilot tube was cut and the ETT and the pilot balloon were pulled out from the cat’s mouth separately. No signs of O2 desaturation were seen at any point. The cat received oxygen and was kept under a forced air warming blanket throughout recovery, which was uneventful, and supervised until it was normothermic. Oesophagostomy tube placement is a common procedure in small animal practice when nutritional support is needed. It is a cheap and simple procedure carried out under general anaesthesia. The technique is minimally invasive and no specialized equipment is needed. In a retrospective study in cats, Levine et al. (1997) reported that, from a total of 60 cases undergoing oesophagostomy tube placement, the tangling of the oesophagostomy tube around the cuff inflator apparatus of the ETT during 228
the passage of the feeding tube into the oesophagus occurred three times, and was the only complication associated with the procedure. In that study, however, it was not described how the problem was corrected. A prospective study clinically evaluating tube oesophagostomy in dogs and cats also mentions the entrapment of the feeding tube around the ETT during redirection of the former into its final position, but does not specify whether it happened in dogs or cats, nor its incidence (Devitt & Seim 1997). More often, delayed complications of the oesophagostomy are seen which include feeding tube site inflammation, abscessation, clogging of the tube, swelling of the head, scratching at the tube, vomiting and regurgitation (Devitt & Seim 1997; Levine et al. 1997; Von Werthern & Wess 2001). Although the incidence of an ETT pilot tube getting entrapped in the oesophageal feeding tube during its placement is low, this should always be considered as a potential complication of the procedure, and care must be taken during the positioning of the feeding tube, especially in small patients. The size of the patient can be considered a relevant risk factor for this complication, as it has been reported mainly in cats. The use of an uncuffed ETT would prevent the complication described above. Uncuffed ETT in cats may be preferred because cats are prone to tracheal damage either because of over-inflation of the cuff or changes in the patient’s position without disconnecting the ETT from the anaesthetic machine (Mitchell et al. 2000). However, in the authors’ opinion, the benefits of having a cuffed ETT with subsequent increased protection of the airways during a procedure involving the oesophagus outweigh the risk of entrapment of the pilot tube. Visual examination of the oropharynx and careful monitoring of the patient until extubation are therefore suggested in these cases. Sarah Boveri & Jacqueline C Brearley Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, UK E-mail: [email protected] References Devitt CM, Seim HB III (1997) Clinical evaluation of tube esophagostomy in small animals. J Am Anim Hosp Assoc 33, 55–60. Levine PB, Smallwood LJ, Buback JL (1997) Esophagostomy tubes as a method of nutritional
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 42, 226–231
Letters to the Editor
management in cats: a retrospective study. J Am Anim Hosp Assoc 33, 405–410. Mitchell SL, McCarthy R, Rudloff E et al. (2000) Tracheal rupture associated with intubation in cats: 20 cases (1996-1998). JAVMA 216, 1592–1595. Von Werthern CJ, Wess G (2001) A new technique for insertion of esophagostomy tubes in cats. J Am Anim Hosp Assoc 37, 140–143.
doi:10.1111/vaa.12227
Opioid-induced adverse effects in a Holstein calf
This is a report of an opioid-induced adverse effect in a 2-month old 70 kg female Holstein calf that was referred to our veterinary teaching hospital (VTH) with persistent left hind limb lameness. Two weeks before presentation, an arthrotomy was performed due to septic arthritis of the left stifle. An arthroscopy was then repeated at our institution but lameness and severe pain continued for 72 hours after surgery even after intravenous (IV) administration of meloxicam (0.5 mg kg 1 every 48 hours) (Anderson & Edmondson 2013). Further analgesia was required. Under aseptic conditions, an epidural injection of preservative-free morphine (0.1 mg kg 1; Morphine, 10 mg mL 1; Sandoz, QC, Canada) with sterile saline 0.9% (total of 10 mL) was performed between the first and second intercoccygeal intervertebral space using a 20 gauge 3.8 cm Tuohy needle. In addition, a 100 lg hour 1 fentanyl patch (1.43 lg kg hour 1; Fentanyl patch; Sandoz) was applied at the cranial aspect of the left tibia immediately after the epidural injection. The skin was prepared by clipping the hair, gentle wash with warm water, and then air-drying. A light bandage was applied to cover the patch. Approximately 2 hours later, the calf became agitated with an altered state of consciousness. Mydriasis, nystagmus, increased locomotor activity, vocalization, myoclonus of the tail, hyperesponsiveness to external stimuli and hyperthermia (40.7°C) were observed. Thoracic auscultation revealed tachycardia (>200 beats minute 1) and tachypnea (>100 breaths minute 1) without change in mucous membrane color. A possible opioid-induced
dysphoria due to overdosing was suspected. The fentanyl patch was removed immediately and diazepam (0.07 mg kg 1) was administered IV. Approximately 5 minutes later, acepromazine (0.015 mg kg 1) IV was also administered since clinical signs had not ceased. Ice packing and a fan were used for cooling of the calf. Lactated Ringer’s solution (4 mL kg hour 1) was administered IV. Five minutes later naloxone (5 lg kg 1) was diluted into 5 mL of sterile saline and given IV over 3 minutes. The calf returned to normal behavior in approximately 2 minutes later. Sedation was observed followed by sternal recumbency. Temperature, heart and respiratory rate returned to their normal limits within the following hours without renarcotization. Drug concentrations and volumes were reviewed and deemed to be correct. The analgesic and adverse effects of opioids have not been well studied in cattle (Machado Filho et al. 1998). Opioids are not commonly used for pain management in farm animals because of their withdrawal times, economic constraint, and need for record keeping of controlled substances. However, epidural administration of morphine and the application of transdermal fentanyl patches have been used in clinical practice. These techniques provide long-sustained analgesia but changes in behavior, increased locomotor activity, dysphoria, and hyperthermia have been observed in other species after opioid administration. We are unaware of a case report in calves. Substantial variations in plasma drug concentrations, onset of action and analgesic effectiveness have been documented after fentanyl patch placement in different species. Changes in skin temperature, preparation and permeability, and location of the patch may affect absorption and efficacy of fentanyl. However, to our knowledge, there are no published data on the pharmacokinetics and pharmacodynamics of fentanyl in cattle. In foals, plasma concentrations of fentanyl were detected as early as 20 minutes after patch placement (Ebersp€ acher et al. 2008). Rapid absorption of fentanyl could explain the observed behavioral changes after drug administration in this case. Central nervous system (CNS) excitation after opioid administration has been linked to the distribution of opioid receptors in the brain, release of excitatory neurotransmitters or decreased activity of inhibitory neurotransmitters. Furthermore, opioids may also affect the thermoregulatory center in the hypothalamus inducing hyperthermia (Kukanich & Papich 2009).
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 42, 226–231
229
drugs administered for sedation and not the ones administered epidurally. Systemic absorption of epidural xylazine in the sheep in this study was suggested by subsequent decreases in arterial oxygen tension (PaO2) and hemoglobin oxygen saturation (SpO2). However, the degree of sedation was not as severe as previously described (Kastner 2006). Also, the decrease in Hct was not more severe in this group compared to the others as we expected, suggesting that the systemic absorption of xylazine did not contribute to the Hct decrease. Although a discrepancy has been described between Hct obtained by i-STAT and the Hct obtained by laboratory analyzers (Peir o et al. 2010), our data were collected with only one technology (i-STAT), revealing only differences between treatments and a change in Hct over time. Acepromazine induces relaxation and vasodilation of the splenic capsule promoting sequestration of erythrocytes (Ambr osio et al. 2012). Nevertheless, a study in dogs showed no correlation between splenomegaly and decreased Hct, suggesting that the effect of the drug is not exclusively related to splenic size but also related to vascular smooth muscle within the splanchnic circulation (Wilson et al. 2004). Although the effect is known, there are few reports that objectively assess the magnitude of this reduction, especially in sheep. In horses sedated with acepromazine or xylazine and acepromazine, the Hct decreased 17% and 19%, respectively, and remained decreased for 180 minutes returning to baseline levels only 24 hours later (Ambr osio et al. 2012). The evaluation of the effect of acepromazine on Hct was not the goal of this study. Therefore, it is not known for what period of time the Hct remained low. In healthy animals, a moderate, sedative-induced reduction in Hct does not result in significant clinical effects. The significance of the information in this letter arises from the effects of these sedative drugs in animals with preexisting diseases of oxygen delivery, such as anemia. These patients are at greater risk for significant morbidity following sedation with acepromazine and diazepam. Further studies should be done assessing the effects of acepromazine on Hct in sheep in order to evaluate the onset of this effect, and the degree and duration of reduction. Ceci R Leite*, Fabio O Ascoli†, Juliana de Oliveira‡ & Felipe Z Brand~ao* *Department of Veterinary Pathology and Clinic, Fluminense Federal University, Niter oi, RJ,
Brazil,†Physiology Department, Fluminense Federal University, Niter oi, RJ, Brazil,‡Basic Science Department, Fluminense Federal University, Niter oi, RJ, Brazil E-mail: [email protected] References Ambrosio AM, Ida KK, Souto MTMR et al. (2012) Significant hematocrit decrease in healthy horses during clinical anesthesia. Braz J Vet Res Anim Sci 49, 139–145. Kastner SBR (2006) Alpha2-agonists in sheep: a review. Vet Anaesth Analg 33, 79–96. Leise BS, Fugler LA, Stokes AM et al. (2007) Effects of intramuscular administration of acepromazine on palmar digital blood flow, palmar digital arterial pressure, transverse facial arterial pressure, and packed cell volume in clinically healthy, conscious horses. Vet Surg 36, 717–723. Peir o JR, Borges AS, Goncßalves RC et al. (2010) Evaluation of a portable clinical analyzer for the determination of blood gas partial pressures, electrolyte concentrations, and hematocrit in venous blood samples collected from cattle, horses, and sheep. Am J Vet Res 71, 515–521. Wilson DV, Evans AT, Carpenter RA et al. (2004) The effect of four anesthetic protocols on splenic size in dogs. Vet Anaesth Analg 31, 102–108.
doi:10.1111/vaa.12222
All in a tangle: a mishap with an oesophagostomy tube in an intubated cat
We would like to report a case of entrapment of the pilot tube of an endotracheal tube (ETT) within an oesophagostomy tube loop. A one-year-old, 3.2 kg, female neutered Domestic Shorthair cat with multiple pelvic fractures post-road traffic accident was anaesthetized for fracture repair and oesophagostomy tube placement. Medetomidine [0.003 mg kg 1 (Sedator, Dechra Veterinary Products Limited, UK)] was administered intravenously (IV) for premedication, followed approximately 5 minutes later by propofol [16 mg IV (PropoFlo Plus, Abbott, UK)]. After endotracheal intubation with a 4 mm internal diameter cuffed
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 42, 226–231
227
Letters to the Editor
polyvinyl chloride endotracheal tube, anaesthesia was maintained with isoflurane (IsoFlo, Abbott, UK) in oxygen (O2) and the cat was allowed to breathe spontaneously throughout the procedure. Analgesia was provided, intraoperatively, with methadone, ketamine and fentanyl. At the end of the orthopaedic surgery, lasting approximately 210 minutes, the cat was taken to radiology, where, prior to taking post-operative radiographs, an oesophagostomy tube was placed. At the end of the procedure, and after the radiographs had been taken, isoflurane was discontinued. The cat was allowed to breathe 100% O2 while re-warming took place and until the palpebral reflex was present. The ETT was then disconnected from the anaesthetic circuit and the cat (still with the ETT in place) moved to the recovery area. When the cat started swallowing, the cuff of the ETT was deflated. An attempt to pull the ETT out from the oral cavity was made, but it could not be withdrawn. A bolus of propofol was administered IV in order to suppress the swallowing reflex and give more time for investigation. The oral cavity was examined using a laryngoscope. The pilot balloon of the ETT could be seen retreating into the oesophagus when any attempt at extubation was made. It was not possible to free the pilot balloon without pushing the ETT deeper through the larynx. Finally, we considered that the ETT pilot tube could have been entrapped in a loop of the oesophagostomy tube during the placement of the latter. Normally, during placement of an oesophagostomy tube, the tube is withdrawn into the mouth from its initial insertion site in the cervical oesophageal region and redirected caudally into the oesophagus. We think this is where the entrapment could have occurred. The pilot tube was cut and the ETT and the pilot balloon were pulled out from the cat’s mouth separately. No signs of O2 desaturation were seen at any point. The cat received oxygen and was kept under a forced air warming blanket throughout recovery, which was uneventful, and supervised until it was normothermic. Oesophagostomy tube placement is a common procedure in small animal practice when nutritional support is needed. It is a cheap and simple procedure carried out under general anaesthesia. The technique is minimally invasive and no specialized equipment is needed. In a retrospective study in cats, Levine et al. (1997) reported that, from a total of 60 cases undergoing oesophagostomy tube placement, the tangling of the oesophagostomy tube around the cuff inflator apparatus of the ETT during 228
the passage of the feeding tube into the oesophagus occurred three times, and was the only complication associated with the procedure. In that study, however, it was not described how the problem was corrected. A prospective study clinically evaluating tube oesophagostomy in dogs and cats also mentions the entrapment of the feeding tube around the ETT during redirection of the former into its final position, but does not specify whether it happened in dogs or cats, nor its incidence (Devitt & Seim 1997). More often, delayed complications of the oesophagostomy are seen which include feeding tube site inflammation, abscessation, clogging of the tube, swelling of the head, scratching at the tube, vomiting and regurgitation (Devitt & Seim 1997; Levine et al. 1997; Von Werthern & Wess 2001). Although the incidence of an ETT pilot tube getting entrapped in the oesophageal feeding tube during its placement is low, this should always be considered as a potential complication of the procedure, and care must be taken during the positioning of the feeding tube, especially in small patients. The size of the patient can be considered a relevant risk factor for this complication, as it has been reported mainly in cats. The use of an uncuffed ETT would prevent the complication described above. Uncuffed ETT in cats may be preferred because cats are prone to tracheal damage either because of over-inflation of the cuff or changes in the patient’s position without disconnecting the ETT from the anaesthetic machine (Mitchell et al. 2000). However, in the authors’ opinion, the benefits of having a cuffed ETT with subsequent increased protection of the airways during a procedure involving the oesophagus outweigh the risk of entrapment of the pilot tube. Visual examination of the oropharynx and careful monitoring of the patient until extubation are therefore suggested in these cases. Sarah Boveri & Jacqueline C Brearley Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, UK E-mail: [email protected] References Devitt CM, Seim HB III (1997) Clinical evaluation of tube esophagostomy in small animals. J Am Anim Hosp Assoc 33, 55–60. Levine PB, Smallwood LJ, Buback JL (1997) Esophagostomy tubes as a method of nutritional
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 42, 226–231
Letters to the Editor
management in cats: a retrospective study. J Am Anim Hosp Assoc 33, 405–410. Mitchell SL, McCarthy R, Rudloff E et al. (2000) Tracheal rupture associated with intubation in cats: 20 cases (1996-1998). JAVMA 216, 1592–1595. Von Werthern CJ, Wess G (2001) A new technique for insertion of esophagostomy tubes in cats. J Am Anim Hosp Assoc 37, 140–143.
doi:10.1111/vaa.12227
Opioid-induced adverse effects in a Holstein calf
This is a report of an opioid-induced adverse effect in a 2-month old 70 kg female Holstein calf that was referred to our veterinary teaching hospital (VTH) with persistent left hind limb lameness. Two weeks before presentation, an arthrotomy was performed due to septic arthritis of the left stifle. An arthroscopy was then repeated at our institution but lameness and severe pain continued for 72 hours after surgery even after intravenous (IV) administration of meloxicam (0.5 mg kg 1 every 48 hours) (Anderson & Edmondson 2013). Further analgesia was required. Under aseptic conditions, an epidural injection of preservative-free morphine (0.1 mg kg 1; Morphine, 10 mg mL 1; Sandoz, QC, Canada) with sterile saline 0.9% (total of 10 mL) was performed between the first and second intercoccygeal intervertebral space using a 20 gauge 3.8 cm Tuohy needle. In addition, a 100 lg hour 1 fentanyl patch (1.43 lg kg hour 1; Fentanyl patch; Sandoz) was applied at the cranial aspect of the left tibia immediately after the epidural injection. The skin was prepared by clipping the hair, gentle wash with warm water, and then air-drying. A light bandage was applied to cover the patch. Approximately 2 hours later, the calf became agitated with an altered state of consciousness. Mydriasis, nystagmus, increased locomotor activity, vocalization, myoclonus of the tail, hyperesponsiveness to external stimuli and hyperthermia (40.7°C) were observed. Thoracic auscultation revealed tachycardia (>200 beats minute 1) and tachypnea (>100 breaths minute 1) without change in mucous membrane color. A possible opioid-induced
dysphoria due to overdosing was suspected. The fentanyl patch was removed immediately and diazepam (0.07 mg kg 1) was administered IV. Approximately 5 minutes later, acepromazine (0.015 mg kg 1) IV was also administered since clinical signs had not ceased. Ice packing and a fan were used for cooling of the calf. Lactated Ringer’s solution (4 mL kg hour 1) was administered IV. Five minutes later naloxone (5 lg kg 1) was diluted into 5 mL of sterile saline and given IV over 3 minutes. The calf returned to normal behavior in approximately 2 minutes later. Sedation was observed followed by sternal recumbency. Temperature, heart and respiratory rate returned to their normal limits within the following hours without renarcotization. Drug concentrations and volumes were reviewed and deemed to be correct. The analgesic and adverse effects of opioids have not been well studied in cattle (Machado Filho et al. 1998). Opioids are not commonly used for pain management in farm animals because of their withdrawal times, economic constraint, and need for record keeping of controlled substances. However, epidural administration of morphine and the application of transdermal fentanyl patches have been used in clinical practice. These techniques provide long-sustained analgesia but changes in behavior, increased locomotor activity, dysphoria, and hyperthermia have been observed in other species after opioid administration. We are unaware of a case report in calves. Substantial variations in plasma drug concentrations, onset of action and analgesic effectiveness have been documented after fentanyl patch placement in different species. Changes in skin temperature, preparation and permeability, and location of the patch may affect absorption and efficacy of fentanyl. However, to our knowledge, there are no published data on the pharmacokinetics and pharmacodynamics of fentanyl in cattle. In foals, plasma concentrations of fentanyl were detected as early as 20 minutes after patch placement (Ebersp€ acher et al. 2008). Rapid absorption of fentanyl could explain the observed behavioral changes after drug administration in this case. Central nervous system (CNS) excitation after opioid administration has been linked to the distribution of opioid receptors in the brain, release of excitatory neurotransmitters or decreased activity of inhibitory neurotransmitters. Furthermore, opioids may also affect the thermoregulatory center in the hypothalamus inducing hyperthermia (Kukanich & Papich 2009).
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 42, 226–231
229
