Injectable anesthetic combinations can provide an alternative to inhalation anesthesia for surgical procedures in dogs. Agents that can be administered IM may be particularly useful when the anesthetist encounters an excited, nervous, or aggressive dog that does not allow restraint for placement of an IV catheter for anesthetic administration or placement of a face mask for inhalation anesthesia induction. The IM administration of injectable anesthetic combinations at various dosages as premedication in dogs is a common practice in modern veterinary anesthesia that can smooth the transition to IV anesthetic induction and maintenance with inhalation anesthesia. Results of a previous study1 comparing the effects of butorphanol–tiletamine-zolazepam combinations with and without medetomidine in dogs indicated that adding medetomidine (15 μg/kg) to a lower dose of butorphanol–tiletamine-zolazepam (0.15 mg of butorphanol/kg and 3 mg of tiletamine-zolazepam/kg) induced better sedative and analgesic effects with a smoother recovery, compared with administration of a higher dose of butorphanol–tiletamine-zolazepam (0.2 mg of butorphanol/kg and 5 mg of tiletamine-zolazepam/kg) alone. In that study,1 the addition of an α2–adrenoceptor agonist, medetomidine, to the protocol enhanced the sedative effects of butorphanol–tiletamine-zolazepam, allowing smaller doses of these drugs to be used and significantly improving the quality of muscle relaxation and analgesia. Results of another study2 evaluating dexmedetomidine (15 μg/kg)-ketamine (3.0 mg/kg) in combination with various opioids (hydromorphone [0.05 mg/kg], buprenorphine [40 μg/kg], and butorphanol [0.2 mg/kg]) in dogs undergoing castration showed that all 3 anesthetic combinations provided suitable anesthesia for completion of the surgical procedure in most patients. A hemodynamic study3 comparing dexmedetomidine-butorphanol-ketamine with DBTZ in dogs found that DBTZ and dexmedetomidine-butorphanol-ketamine had similar hemodynamic profiles characterized by increased MAP, increased systemic vascular resistance, and reflex bradycardia. That study3 also revealed that the oxygen extraction ratio was significantly higher in dogs that received dexmedetomidine-butorphanol-ketamine than in DBTZ-treated dogs.
Tramadol is a centrally acting, synthetic opioid with a molecular structure similar to that of codeine.4 Tramadol induces analgesia through 2 mechanisms; tramadol and its metabolite O-desmethyl-tramadol (M1) act on μ-opioid receptors, and tramadol also inhibits serotonin and norepinephrine reuptake, enhancing inhibition of pain transmission in the spinal cord.4 Tramadol has been shown to significantly reduce the minimum alveolar concentration of sevoflurane in dogs.5 The IV administration of 2.0 mg of tramadol/kg shortly after anesthetic induction but before surgery produced comparable postoperative analgesia with less respiratory depression in dogs undergoing ovariohysterectomy, compared with morphine (0.2 mg/kg, IV) administered in the same manner.6 In a comparative study7 in dogs, when various opioids were given after administration of acepromazine (0.05 mg/kg, IV), the sedative effects of tramadol (2.0 mg/kg, IV) were similar to those of morphine (0.5 mg/kg, IV) or butorphanol (0.15 mg/kg, IV) but were less intense than those of methadone (0.5 mg/kg, IV).
In many countries, an injectable formulation of tramadol is readily available and is not considered a controlled substance; this makes it attractive as part of an anesthetic-analgesic combination. The use of this formulation of tramadol (not currently commercially available in the United States) as a component of an injectable anesthetic protocol is novel. The sedative and analgesic properties of tramadol in combination with sedatives such as dexmedetomidine and dissociatives such as ketamine or tiletamine have not been explored. Furthermore, the cardiorespiratory effects of tramadol may be less profound than that of other opioids, providing an advantage when used as part of an anesthetic combination.
The purpose of the study reported here was to compare anesthetic, analgesic, and cardiorespiratory effects in dogs after IM administration of DBTZ or DTrK. The DBTZ protocol has been previously described3; the doses of dexmedetomidine and ketamine for use with tramadol were selected on the basis of doses used to induce a surgical plane of anesthesia in combination with various opioids in a previous study,2 and the tramadol dose was chosen on the basis of results of a pilot study. Furthermore, results from a pilot study in our laboratory indicated that a dose of dexmedetomidine < 15 μg/kg in combination with ketamine (3.0 mg/kg) would not produce a surgical plane of anesthesia in dogs and resulted in a poorer overall quality of anesthesia, compared with DBTZ.
End-tidal carbon dioxide concentration
Mean arterial blood pressure
Oxygen saturation as measured by pulse oximetry
Dexdomitor, Pfizer Animal Health, New York, NY.
Torbugesic, Pfizer Animal Health, New York, NY.
Telazol, Pfizer Animal Health, New York, NY.
Tramadol Hcl injection, Huons Co Ltd, Hwaseong City, Kyunggi-do, Korea.
Ketaset, Pfizer Animal Health, New York, NY.
Somedic algometer type II, Somedic Production AB, Stockholm, Sweden.
Life-Tech Inc, Staffor, Tex.
Lactate Pro Meter, Quesnel, BC, Canada.
Gaymar TP Professional, Gaymar Industries Inc, Orchard Park, NY.
Gaymar Hot Air Hugger, Gaymar Industries Inc, Orchard Park, NY.
PC-VetGard+, Mill Creek, Wash.
Wright/Haloscale respirometer, Ferraris Respiratory, Louisville, Colo.
Blank clicker, The Clicker Co, Payson, Ariz.
SAS, version 9.1, SAS Institute Inc, Cary, NC.
Proc Mixed, SAS, version 9.1, SAS Institute Inc, Cary, NC.
1. Ko JC, Payton M & Weil AB et alComparison of anesthetic and cardiorespiratory effects of tiletamine-zolazepam-butorphanol and tiletamine-zolazepam-butorphanol-medetomidine in dogs. Vet Ther 2007; 8: 113–126.
2. Barletta M, Austin BR & Ko JC et alEvaluation of dexmedetomidine and ketamine in combination with opioids as injectable anesthesia for castration in dogs. J Am Vet Med Assoc 2011; 238: 1159–1167.
3. Krimins RA, Ko JC & Weil AB et alHemodynamic effects in dogs after intramuscular administration of a combination of dexmedetomidine-butorphanol-tiletamine-zolazepam or dexmedetomidine-butorphanol-ketamine. Am J Vet Res 2012; 73: 1363–1370.
5. Seddighi MR, Egger CM & Rohrbach BW et alEffects of tramadol on the minimum alveolar concentration of sevoflurane in dogs. Vet Anaesth Analg 2009; 36: 334–340.
6. Mastrocinque S, Fantoni DT. A comparison of preoperative tramadol and morphine for the control of early postoperative pain in canine ovariohysterectomy. Vet Anaesth Analg 2003; 30: 220–228.
7. Monteiro ER, Junior AR & Assis HM et alComparative study on the sedative effects of morphine, methadone, butorphanol or tramadol, in combination with acepromazine, in dogs. Vet Anaesth Analg 2009; 36: 25–33.
8. Tas O, De Rooster H & Baert E et alThe accuracy of the Lactate Pro hand-held analyser to determine blood lactate in healthy dogs. J Small Anim Pract 2008; 49: 504–508.
9. Bernhardt O, Schiffman EL, Look JO. Reliability and validity of a new fingertip-shaped pressure algometer for assessing pressure pain thresholds in the temporomandibular joint and masticatory muscles. J Orofac Pain 2007; 21: 29–38.
10. Varcoe-Cocks K, Sagar KN & Jeffcott LB et alPressure algometry to quantify muscle pain in racehorses with suspected sacroiliac dysfunction. Equine Vet J 2006; 38: 558–562.
14. Gray CW, Bush M, Beck CC. Clinical experience using CI-744 in chemical restraint and anesthesia of exotic animals. J Zoo Wildl Med 1974; 5: 12–21.
15. Ko JC, Knesl O & Weil AB et alFAQs—analgesia, sedation, and anesthesia: making the switch from medetomidine to dexmedetomidine. Compend Contin Educ Pract Vet 2009; 31(suppl 1A): 1–24.
17. Itami T, Tamaru N & Kawase K et alCardiovascular effects of tramadol in dogs anesthetized with sevoflurane. J Vet Med Sci 2011; 73: 1603–1609.
Scoring system1,2 used to evaluate sedation via response to auditory stimulation (noise made with a clicker held close to the dog's ear) in 6 healthy dogs at predetermined time points before and after a single IM injection of DBTZ or DTrK.
|1||Total response to the clicker noise with head turning, ear twitchings, and looking toward direction of clicker; aware of surroundings; minimal sedation|
|2||Moderate response to the clicker noise; head and neck move slightly and ears twitch in response to the noise; dog is unsure where noise is originating; moderate sedation|
|3||No head movement in response to the clicker noise; minimal eye movement or blinking, with or without ear twitching; moderately heavy sedation|
|4||Blinking response only to the clicker noise (no other body movement); profound sedation|
|5||No response to the clicker noise; no purposeful movements; no blinking reponse; all clinical signs consistent with general anesthesia|
Criteria1 used to score quality of intubation in dogs.
|1||Difficult intubation; tube cannot be retained; tight jaw tone accompanied by chewing motion; strong tongue withdrawal|
|2||Easy intubation with slight coughing or swallowing reflex following intubation but no gagging reflex; relaxed jaw tone; no chewing motions; slight tongue withdrawal|
|3||Intubation easily achieved; animal becomes rapidly unconscious; good muscle relaxation|
Criteria1,2 used to score quality of anesthesia in dogs.
|0||Active; aware of the surrounding environment; minimal sedation|
|1||Mild to moderate sedation with reduced activity; does not assume sternal or lateral recumbency|
|2||Moderate sedation; mildly aware of the surrounding environment; sternal recumbency only|
|3||Profound sedation; eyes droopy; head down; inactive; assumes sternal or lateral recumbency; tight jaw tone; unable to be intubated|
|4||Rapid smooth induction of anesthesia; no movement; rapidly assumes lateral recumbency with excellent muscle relaxation; loose jaw tone and easy intubation|
Criteria2 used to score quality of recovery in dogs.
|1||Prolonged struggling; unable to stand without assistance; hyperkinesia in response to manual assistance|
|2||Some struggling; repeated attempts to stand and requires assistance to stand; very unstable while walking and unable to maintain balance; some signs of residual anesthetic effects|
|3||Some struggling; requires some assistance to stand; able to maintain balance once standing; minimal signs of residual anesthetic effects|
|4||Dog assumes sternal recumbency with little or minimal struggling; stands and walks with minimal effort; no signs of anesthetic effects|