- Email: [email protected]
ANAESTHETIC TECHNIQUES IN THE LLAMA
Proceedinns of the 4th International Conmess of Vctennarv Anaesthesia
ANAESTHETIC TECHNIQUES IN THE LLAMA T.W. Riebold, W.B. Schmotzer, MJ.Huber. Veterinary Teaching Hospital, College of Veterinary Mediche, Oregon State University, Corvallis, OR 97331
vertebral transverse processes and superficial to the carotid artery and vagosympathetic trunk within the carotid sheath for most of its length. The jugular bifurcation is separated from the carotid by the omohyoideus and located at the intersection of a line drawn caudally along the ventral aspect of the body of the mandible and another line connecting the base of the ear and the lateral aspect of the cervical transverse processes. Venipuncture or catheterization can be performed at the bifurcation or at any point caudal to it. However, because of the close proximity of the carotid artery to the vein, one must ascertain that the vein has been catheterized and not the artery. After occlusion of the vessel, one will be unable to see the jugular distend; however, the vein can be palpated particularly rostrally and more easily in females and neutered males because their skin is thinner. Sixteen gauge catheters are appropriate for adult llamas and 18 to 20 gauge catheters for smaller llamas. Contact with jugular venous valves may prevent catheterization; a more caudal location should be used. Xylazine is often used to provide sedation or, in higher doses, restraint. Although complete data are not available on the cardiovascular and respiratory effects of xylazine in llamas, the agent causes bradycardia as it does in other species and has little effect on blood pressure early after administration followed by hypotension. The degree of sedation or restraint that results depends on the amount given and the animal's temperament. Low doses (0.14.2 mg/kg IV) provide sedation without recumbency. Butorphanol (0.06 mg/kg IM) can
Increased interest in llamas as pets, breeding, and pack animals has led to increased demand for veterinary services for them. While llamas have some unique species characteristics regarding anaesthesia, many of the principles and techniques used in food animal and equine anaesthesia also apply to llamas. Considerations for preanaesthetic preparation include fasting, assessment of haematologic and blood chemistry values, and venous catheterization. The llama has a stomach divided into three compartments. Therefore, potential complications similar to those of domestic ruminants; tympany, regurgitation, and aspiration pneumonia, exist during anaesthesia. It is recommended that the animals be fasted 12-18 hours and deprived of water for 8-12 hours. In nonelective cases, this is often not possible and precautions should be taken to avoid aspiration of fluid and ingesta. Fasting neonatal llamas is not advisable because hypoglycaemia may result. As in other species, haematologic and blood chemistry values are determined before anaesthesia. Results should be compared to reference values. Venipuncture and venous catheterization are often performed in llamas. Physical restraint during venipuncture or catheterization varies and can consist of a handler holdmg the llama's halter, and if the animal is fractious, grasping an ear; or it can involve use of restraining chutes designed for llamas. Local anaesthesia at the catheterization site is recommended. Llamas do not have a jugular groove. The jugular vein lies deep to the sternomandibularii and brachiocephalicus muscles, ventral to cervical
237
Proceedin= of the 4th International Conmess of Veterinarv Anaesthesia
also be used to provide sedation and analgesia.
mg/kg IV),5% guaifenesin and 0.2% thiobarbim a t e solution (1.5-2.2 ml/kg IV to effect), xylazine (0.25 mg/kg IV) and ketamine (3-5 mg/kg IV) 5 minutes apart, 0.1% ketamine and 5% guaifenesin solution (15-2.2 ml/kg IV to effect), or halothane or isoflurane by mask in small or debilitated llamas. Guaifenesin (5%) used alone at 2.2 ml/kg IV, provides little, if any, analgesia, and local anaesthesia must be used when painful procedures are performed. Techniques that use guaifenesin provide better muscle relaxation during intubation. Transient apnoea can occur with all the techniques. For convenience, the mixture may be injected with large (140 ml) syringes rather than administered by infusion. Mask induction with halothane or isoflurane as performed in foals or small ruminants can be used in small or debilitated llamas, or llamas restrained with xylazine-ketamine, T e h l , @etc. Mask induction in healthy untranquillized adult llamas is usually not attempted because application of the mask may provoke spitting. After induction, intubation is recommended because it provides a Secure airway and prevents aspiration of salivary secretions and gastric fluids if regurgitation occurs. Oral intubation (cuffed, 6-14 mm i.d., 50 cm tubes) is performed Similar to domestic ruminants. Blind intubation is often unsuccessful and laryngoscopy with a 250 mm laryngoscope is recommended. Visibility of the larynx is improved by hyperextending the head and neck to make the orotracheal axis approach 180" and using gauze on a sponge forceps to swab the pharynx if secretions are a problem. If desired, a guide tube could be passed into the larynx and the endotracheal tube threaded over it. Nasal intubation is also possible although it requires an E/T tube one size smaller. Llamas are prone to epistaxk and use of lubricating compounds that contain phenylephrine are recommended. Attempting intubation
The animals usually remain standing. Poorly trained animals or berserk males tend to be less responsive and ill or debilitated llamas are more responsive to sedative doses of butorphanol and xylazine. Higher doses of xylazine will provide recumbency and light planes of general anaesthesia. Xylazine (0.3-0.4 mg/kg IV) usually produces 20 to 30 minutes of recumbency. Sedation and recumbency can be reversed with 4aminopyridine (0.3 mg/kg IV) and yohimbme (0.12 mg/kg IV), or with tolazoline (2.0 mg/kg IV). Doxapram is not effective. Xylazine (0.2543 mg/kg IM) and ketamine (5.0-8.0 mg/kg IM, 15 minutes later) usually provide 30-60 minutes of restraint. Depth of anaesthesia varies with the llama's temperament but is usually sufficient for minor procedures such as suturing lacerations, draining abscesses, or cast application. When this combination provides insufficient anaesthetic depth, intubation may not be possible and supplemental local anaesthesia may be needed to allow completion of surgery. However, this combination does immobilize the animal, facilitating venipuncture or application of a face mask to increase the depth of anaesthesia. If desired, xylazine (0.25 mg/kg IV) and ketamine (3.0-5.0 mg/kg IV) may be administered 5 minutes apart to obtain a more uniform response and sufficient depth of anaesthesia for intubation. TelazolQ (4.4 mg/kg IM) can provide up to 2 hours of restraint. Llamas tend to recover well from anaesthesia without experiencing emergence delirium and usually are not tranquillized before induction. Atropine (0.02 mg/kg IV) is recommended because llamas are prone to parasympathetic discharge during intubation or painful stimuli. Induction can be accomplished in untranquillized llamas with thiobarbiturate (8.8-11.0
238
Proceedings of the 4th International Congress of Veterinary Anaesthesia
thesia, the rebreathing bag should be compressed (20-30 un H P inspiratory pressure) at 5-10 minute intervals to "sigh" the animal, activating surfactant and preventing atelectasis. During recovery, the llama should remain intubated until able to chew and swallow. Since llamas are obligate nasal breathers, gas exchange must be confiied after extubation; airway obstruction can commonly wur during the transition from oral endotracheal intubation to nasal breathing. The endotracheal tube of nasally intubated llamas can be removed after they stand. If regurgitation has occurred, the endotrachea tube should be withdrawn with the cuff inflated until the cuff reaches the larynx. Any ingesta that may have lodged in the pharynx or buccal cavity must be removed. Although llamas recover well from general anaesthesia with minimal assistance, an attendant should be available.
when the anaesthetic plane is insufficient will often provoke regurgitation when the laryngoscope blade contacts the epiglottis or when the endotracheal tube contacts the larynx. With adequate depth of anaesthesia, this reflex is eliminated. Maintenance of inhalation anaesthesia in llamas can be accomplished with halothane, isoflurane, or methoxyflurane. Halothane and isoflurane are preferred. Methoxyflurane is characterized by longer induction and recovery periods, but could be used, particularly in smaller llamas. Conventional small animal anaesthetic machines can be used on llamas weighing less than 60 kg. When the llama exceeds that size, conventional human anaesthetic machines or small animal machines with expanded soda lime canisters are suitable. Oxygen flow rates of 20 ml/kg/min during induction and 12 ml/kg/min during maintenance with minimal flow rates of 1 l/min are adequate. During induction, halothane or isoflurane is administered at 34% with anaesthesia maintained at 152.5%. During anaes-
Table 1. Doses of commonly used anaesthetic agents in llamas.
1 Duration 1
Agent
Dose
Xylazine
0.34.4 mg/kg IV
30-45 min
Xylazine
0.4-0.6 mg/kg IM
3045 min
Thiobarbiturate
8.8-11.0mg/kg IV
10-15min
Thiobarbiturate and Guaifenesin
3.3 mg/kg and 80 mg/kg combined IV
15-20 min
Ketamine and Guaifenesin
1.6 mg/kg and 80 mg/kg combined IV
15-20 min
Xylazine and Ketamine
0.25 mg/kg, 3.0-5.0 mg/kg both IV, 5 rnin apart;
30-45 min
Xvlazine and Ketamine
0.35 mg/kg, 5.0-8.0 mg/kg both IM,15 rnin apart.
30-60 rnin
239
Proceedings of the 4th International Congress of Veterinary Anaesthesia
Table 2. Normal Values for Haematology and Blood Chemistry in Llamas at Oregon State University Veterinary Diagnostic.
NORMAL VALUE Albumin Alkaline phosphatase
38.6 f 233 IU/L
Aspartate amhotransferase
113.2 f 41.6 IU/L
Bilirubin
0.2
Blood urea nitrogen
29.0 f 6.1 mg/dl
calcium
9.0 f 0.7.mg/dl
Chloride
115.9 f 4.8 meq/L
Creatinine kinase
81.8 f 110.0 IU/L
Creatinine
25
Gamma glutamyltransferase
19.8 f 4.8 IU/L
Glucose
134.2 f 36.0 mg/d
Magnesium
Potassium
~~
I
0.2 mg/dl
f
0.5 mg/dl
1.9 f 0.3 meq/L
3.8 f 0.9 meq/L
~~
Sodium
149.4 f 5.4 meq/L
Haemoglobm
153 f 1.7 gm/dl
Haematocrit
34 2 4.0%
Erythrocytes
10.88
I
~
2
1.1x 1o6cells/mm3
Leucocytes ~~
Plasma protein
6.5 f 0.4 gm/d
Fibrinogen
300 f 114.0 mg/dl
ANAESTHETIC TECHNIQUES IN THE LLAMA T.W. Riebold, W.B. Schmotzer, MJ.Huber. Veterinary Teaching Hospital, College of Veterinary Mediche, Oregon State University, Corvallis, OR 97331
vertebral transverse processes and superficial to the carotid artery and vagosympathetic trunk within the carotid sheath for most of its length. The jugular bifurcation is separated from the carotid by the omohyoideus and located at the intersection of a line drawn caudally along the ventral aspect of the body of the mandible and another line connecting the base of the ear and the lateral aspect of the cervical transverse processes. Venipuncture or catheterization can be performed at the bifurcation or at any point caudal to it. However, because of the close proximity of the carotid artery to the vein, one must ascertain that the vein has been catheterized and not the artery. After occlusion of the vessel, one will be unable to see the jugular distend; however, the vein can be palpated particularly rostrally and more easily in females and neutered males because their skin is thinner. Sixteen gauge catheters are appropriate for adult llamas and 18 to 20 gauge catheters for smaller llamas. Contact with jugular venous valves may prevent catheterization; a more caudal location should be used. Xylazine is often used to provide sedation or, in higher doses, restraint. Although complete data are not available on the cardiovascular and respiratory effects of xylazine in llamas, the agent causes bradycardia as it does in other species and has little effect on blood pressure early after administration followed by hypotension. The degree of sedation or restraint that results depends on the amount given and the animal's temperament. Low doses (0.14.2 mg/kg IV) provide sedation without recumbency. Butorphanol (0.06 mg/kg IM) can
Increased interest in llamas as pets, breeding, and pack animals has led to increased demand for veterinary services for them. While llamas have some unique species characteristics regarding anaesthesia, many of the principles and techniques used in food animal and equine anaesthesia also apply to llamas. Considerations for preanaesthetic preparation include fasting, assessment of haematologic and blood chemistry values, and venous catheterization. The llama has a stomach divided into three compartments. Therefore, potential complications similar to those of domestic ruminants; tympany, regurgitation, and aspiration pneumonia, exist during anaesthesia. It is recommended that the animals be fasted 12-18 hours and deprived of water for 8-12 hours. In nonelective cases, this is often not possible and precautions should be taken to avoid aspiration of fluid and ingesta. Fasting neonatal llamas is not advisable because hypoglycaemia may result. As in other species, haematologic and blood chemistry values are determined before anaesthesia. Results should be compared to reference values. Venipuncture and venous catheterization are often performed in llamas. Physical restraint during venipuncture or catheterization varies and can consist of a handler holdmg the llama's halter, and if the animal is fractious, grasping an ear; or it can involve use of restraining chutes designed for llamas. Local anaesthesia at the catheterization site is recommended. Llamas do not have a jugular groove. The jugular vein lies deep to the sternomandibularii and brachiocephalicus muscles, ventral to cervical
237
Proceedin= of the 4th International Conmess of Veterinarv Anaesthesia
also be used to provide sedation and analgesia.
mg/kg IV),5% guaifenesin and 0.2% thiobarbim a t e solution (1.5-2.2 ml/kg IV to effect), xylazine (0.25 mg/kg IV) and ketamine (3-5 mg/kg IV) 5 minutes apart, 0.1% ketamine and 5% guaifenesin solution (15-2.2 ml/kg IV to effect), or halothane or isoflurane by mask in small or debilitated llamas. Guaifenesin (5%) used alone at 2.2 ml/kg IV, provides little, if any, analgesia, and local anaesthesia must be used when painful procedures are performed. Techniques that use guaifenesin provide better muscle relaxation during intubation. Transient apnoea can occur with all the techniques. For convenience, the mixture may be injected with large (140 ml) syringes rather than administered by infusion. Mask induction with halothane or isoflurane as performed in foals or small ruminants can be used in small or debilitated llamas, or llamas restrained with xylazine-ketamine, T e h l , @etc. Mask induction in healthy untranquillized adult llamas is usually not attempted because application of the mask may provoke spitting. After induction, intubation is recommended because it provides a Secure airway and prevents aspiration of salivary secretions and gastric fluids if regurgitation occurs. Oral intubation (cuffed, 6-14 mm i.d., 50 cm tubes) is performed Similar to domestic ruminants. Blind intubation is often unsuccessful and laryngoscopy with a 250 mm laryngoscope is recommended. Visibility of the larynx is improved by hyperextending the head and neck to make the orotracheal axis approach 180" and using gauze on a sponge forceps to swab the pharynx if secretions are a problem. If desired, a guide tube could be passed into the larynx and the endotracheal tube threaded over it. Nasal intubation is also possible although it requires an E/T tube one size smaller. Llamas are prone to epistaxk and use of lubricating compounds that contain phenylephrine are recommended. Attempting intubation
The animals usually remain standing. Poorly trained animals or berserk males tend to be less responsive and ill or debilitated llamas are more responsive to sedative doses of butorphanol and xylazine. Higher doses of xylazine will provide recumbency and light planes of general anaesthesia. Xylazine (0.3-0.4 mg/kg IV) usually produces 20 to 30 minutes of recumbency. Sedation and recumbency can be reversed with 4aminopyridine (0.3 mg/kg IV) and yohimbme (0.12 mg/kg IV), or with tolazoline (2.0 mg/kg IV). Doxapram is not effective. Xylazine (0.2543 mg/kg IM) and ketamine (5.0-8.0 mg/kg IM, 15 minutes later) usually provide 30-60 minutes of restraint. Depth of anaesthesia varies with the llama's temperament but is usually sufficient for minor procedures such as suturing lacerations, draining abscesses, or cast application. When this combination provides insufficient anaesthetic depth, intubation may not be possible and supplemental local anaesthesia may be needed to allow completion of surgery. However, this combination does immobilize the animal, facilitating venipuncture or application of a face mask to increase the depth of anaesthesia. If desired, xylazine (0.25 mg/kg IV) and ketamine (3.0-5.0 mg/kg IV) may be administered 5 minutes apart to obtain a more uniform response and sufficient depth of anaesthesia for intubation. TelazolQ (4.4 mg/kg IM) can provide up to 2 hours of restraint. Llamas tend to recover well from anaesthesia without experiencing emergence delirium and usually are not tranquillized before induction. Atropine (0.02 mg/kg IV) is recommended because llamas are prone to parasympathetic discharge during intubation or painful stimuli. Induction can be accomplished in untranquillized llamas with thiobarbiturate (8.8-11.0
238
Proceedings of the 4th International Congress of Veterinary Anaesthesia
thesia, the rebreathing bag should be compressed (20-30 un H P inspiratory pressure) at 5-10 minute intervals to "sigh" the animal, activating surfactant and preventing atelectasis. During recovery, the llama should remain intubated until able to chew and swallow. Since llamas are obligate nasal breathers, gas exchange must be confiied after extubation; airway obstruction can commonly wur during the transition from oral endotracheal intubation to nasal breathing. The endotracheal tube of nasally intubated llamas can be removed after they stand. If regurgitation has occurred, the endotrachea tube should be withdrawn with the cuff inflated until the cuff reaches the larynx. Any ingesta that may have lodged in the pharynx or buccal cavity must be removed. Although llamas recover well from general anaesthesia with minimal assistance, an attendant should be available.
when the anaesthetic plane is insufficient will often provoke regurgitation when the laryngoscope blade contacts the epiglottis or when the endotracheal tube contacts the larynx. With adequate depth of anaesthesia, this reflex is eliminated. Maintenance of inhalation anaesthesia in llamas can be accomplished with halothane, isoflurane, or methoxyflurane. Halothane and isoflurane are preferred. Methoxyflurane is characterized by longer induction and recovery periods, but could be used, particularly in smaller llamas. Conventional small animal anaesthetic machines can be used on llamas weighing less than 60 kg. When the llama exceeds that size, conventional human anaesthetic machines or small animal machines with expanded soda lime canisters are suitable. Oxygen flow rates of 20 ml/kg/min during induction and 12 ml/kg/min during maintenance with minimal flow rates of 1 l/min are adequate. During induction, halothane or isoflurane is administered at 34% with anaesthesia maintained at 152.5%. During anaes-
Table 1. Doses of commonly used anaesthetic agents in llamas.
1 Duration 1
Agent
Dose
Xylazine
0.34.4 mg/kg IV
30-45 min
Xylazine
0.4-0.6 mg/kg IM
3045 min
Thiobarbiturate
8.8-11.0mg/kg IV
10-15min
Thiobarbiturate and Guaifenesin
3.3 mg/kg and 80 mg/kg combined IV
15-20 min
Ketamine and Guaifenesin
1.6 mg/kg and 80 mg/kg combined IV
15-20 min
Xylazine and Ketamine
0.25 mg/kg, 3.0-5.0 mg/kg both IV, 5 rnin apart;
30-45 min
Xvlazine and Ketamine
0.35 mg/kg, 5.0-8.0 mg/kg both IM,15 rnin apart.
30-60 rnin
239
Proceedings of the 4th International Congress of Veterinary Anaesthesia
Table 2. Normal Values for Haematology and Blood Chemistry in Llamas at Oregon State University Veterinary Diagnostic.
NORMAL VALUE Albumin Alkaline phosphatase
38.6 f 233 IU/L
Aspartate amhotransferase
113.2 f 41.6 IU/L
Bilirubin
0.2
Blood urea nitrogen
29.0 f 6.1 mg/dl
calcium
9.0 f 0.7.mg/dl
Chloride
115.9 f 4.8 meq/L
Creatinine kinase
81.8 f 110.0 IU/L
Creatinine
25
Gamma glutamyltransferase
19.8 f 4.8 IU/L
Glucose
134.2 f 36.0 mg/d
Magnesium
Potassium
~~
I
0.2 mg/dl
f
0.5 mg/dl
1.9 f 0.3 meq/L
3.8 f 0.9 meq/L
~~
Sodium
149.4 f 5.4 meq/L
Haemoglobm
153 f 1.7 gm/dl
Haematocrit
34 2 4.0%
Erythrocytes
10.88
I
~
2
1.1x 1o6cells/mm3
Leucocytes ~~
Plasma protein
6.5 f 0.4 gm/d
Fibrinogen
300 f 114.0 mg/dl