Veterinary Surgery, 20, 2, 143-147, 1991
Induction of Anesthesia with Diazepam-Ketamine and Midazolam-Ketamine in Greyhounds
Anesthesia was induced in 14 greyhounds with a mixture of diazepam or midarolam (0.28 mg/kg) and ketamine (5.5 mg/kg), and maintained with halothane. There were no significant differences in weight, age, or duration of anesthesia between the treatment groups. Time to intubation with diazepam-ketamine (4.07 +- 1.43 min) was significantly longer than with midarolam-ketamine (2.73 f 0.84 min). Heart rate, respiratory rate, Paco,, and arterial pH did not vary significantly during anesthesia in either treatment group. Arterial blood pressures, Pao,, halothane vaporizer setting, and body temperature changed significantly from baseline values in both treatment groups during anesthesia. Times to sternal recumbency and times to standing were not significantly different. These data suggest that both diazepam-ketarnine and midazolam-ketamine are useful anesthetic combinations in greyhounds. In combination with ketamine, midazolam offers little advantage over diazepam.
induced with diazepam and A ketamine in healthy, mixed-breed dogs and in dogs with compromised cardiovascular function.',2 DiazepamNESTHESIA HAS BEEN
ketamine anesthesia is characterized by rapid recovery and is an alternative to barbiturate anesthesia in greyhounds. In nervous or excited dogs, induction of anesthesia with diazepam and ketamine may be prolonged and require repeated dosing. Midazolam maleate is a water-soluble benzodiazepine, approximately three times as potent as d i a ~ e p a m .Mid~.~ azolam maleate compares favorably with diazepam for induction of anesthesia in humans5 The purpose of this clinical study is to compare the anesthetic, respiratory, and cardiovascular effects of diazepam-ketamine and midazolam-ketamine administered intravenously in greyhounds. Materials and Methods Fourteen splenectomized greyhound blood donor dogs from the Ohio State University College of veterinary Medicine were determined to be in good physical condition by physical examination. complete blood cell count, and a negative heartworm test. The dogs were anesthetized
for dental prophylaxis, and two dogs were castrated. Food, but not water. was withheld for 12 hours before anesthesia. A 17-gauge intravenous catheter was placed percutaneously in the cephalic vein. A balanced electrolyte solution* (5-10 mL/kg/hr) was administered to replace insensible fluid losses during anesthesia. The dogs were placed in left-lateral recumbency and were reassured b y their regular handlers' talking and petting during instrumentation and baseline recordings. The dorsomedial aspect of the right tarsus and metatarsus was shaved and prepared aseptically. The dorsal pedal artery was catheterized percutancously with a 22-gauge catheter after a local skin block with 0.5 to 1.0 mL of lidocaine (2% solution). In spite of reassurances from their handlers, the dogs remained nervous throughout instrumentation and collection of baseline data. Arterial pressures were measured with a fluid-filled pressure transducer.? The sternum was taken as the reference point for right atrial pressures. Systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) were determined intermittently from a con-
* Lactated Ringers. Travenol Inc.. Deerfield, IL t Could P23d. Could Statham. Oxnard. CA.
From the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University,Columbus, Ohio. Presented at the Veterinary Midwest Anesthesia Conference, Urbana, Illinois, June 4, 1988 Reprint requests: Peter W. Hellyer, DVM. North Carolina State University,College of Veterinary Medicine, 4700 HillsboroughStreet, Raleigh,
NC 27606.
143
144
DIAZEPAM-KETAMINE AND MIDAZOLAM-KETAMINE
tinuous pressure waveform display.$ Mean arterial pressure (MAP) was derived electronically. A bipolar electrocardiogram (lead 11) was monitored continuously. Baseline measurements included SAP, MAP, DAP, heart rate (HR), respiratory rate (RR), arterial pH and blood gases (Pa 02,Pa C O ~ ) ,and rectal body temperature. A 50/50 mixture (V/V) of either diazepam$-ketamine 11 or midazolamlT-ketamine at a dose of 1.O mL/9.1 kg ( 1.O mL/20 lbs) IV was selected randomly for each dog after baseline measurements. This drug combination resulted in a dose of 0.28 mg/kg of diazepam (2.5 mg/mL) or midazolam (2.5 mg/mL) and 5.5 mg/kg ketamine (50 mg/mL). Induction, maintenance, and recovery from general anesthesia were evaluated by one person unaware of the drug combination used. Tracheal intubation, also by one person unaware of the drug combination used, was performed when a dog had stopped chewing and licking. If intubation was not achieved within two minutes, the anesthetic drug combination was readministered once at one-fourth the original dose. Induction was classified as good, fair, or poor. A good induction was an easy transition to unconsciousness, with occasional licking and swallowing. A fair induction was characterized by paddling and vocalizing, and a poor induction consisted of paddling, vocalizing, attempts to escape, urination, and defecation. The endotracheal tube was connected to a small animal circle anesthetic system. Halothane in 100%oxygen ( 3 L/min) was delivered from an out-of-the-circle, agent-specific, precision vaporizer. Halothane was administered at a vaporizer setting of 3% and gradually reduced according to subjective signs of anesthetic depth (licking, swallowing, blinking, palpebral reflex, muscle relaxation, and jaw tone). Systolic arterial pressure, MAP, DAP, HR, RR, arterial pH and blood gases, and rectal temperature were recorded 5 , 10, and 15 minutes after the initial drug administration. Ventilation was not assisted during the 15-minute evaluation period. Anesthesia was maintained with halothane in 100% oxygen for the remainder of the procedure. Evaluation of recovery from anesthesia included time from vaporizer off to sternal recumbency, time from vaporizer off to standing, rectal temperature at the end of anesthesia, and character of recovery (good, fair, poor). A good recovery consisted of one or two attempts to stand and no thrashing, paddling, or vocalizing. A fair recovery was characterized by two to five attempts to stand, paddling, ataxia, and vocalizing. A poor recovery consisted of paddling, vocalizing, thrashing, urinating, and defecating. $ Datascope 670, Datascope Corporation, Paramus. NJ. 5 Diazepam, Elkins-Sinn, lnc. Cheny Hill, NJ. 11 Vetalar, Parke-Davis, Moms Plains, NJ. ll Versed, Hoffman-LaRoche, lnc., Nutley, NJ.
Data are expressed as means f SD. Statistical analysis was performed by using a two-way analysis of variance with comparison of multiple means based on Tukey's w procedure. A one-way analysis of variance or an unpaired Student's t Test was used to compare means between groups of dogs. Means were considered significantly different at p
Induction of Anesthesia with Diazepam-Ketamine and Midazolam-Ketamine in Greyhounds
Anesthesia was induced in 14 greyhounds with a mixture of diazepam or midarolam (0.28 mg/kg) and ketamine (5.5 mg/kg), and maintained with halothane. There were no significant differences in weight, age, or duration of anesthesia between the treatment groups. Time to intubation with diazepam-ketamine (4.07 +- 1.43 min) was significantly longer than with midarolam-ketamine (2.73 f 0.84 min). Heart rate, respiratory rate, Paco,, and arterial pH did not vary significantly during anesthesia in either treatment group. Arterial blood pressures, Pao,, halothane vaporizer setting, and body temperature changed significantly from baseline values in both treatment groups during anesthesia. Times to sternal recumbency and times to standing were not significantly different. These data suggest that both diazepam-ketarnine and midazolam-ketamine are useful anesthetic combinations in greyhounds. In combination with ketamine, midazolam offers little advantage over diazepam.
induced with diazepam and A ketamine in healthy, mixed-breed dogs and in dogs with compromised cardiovascular function.',2 DiazepamNESTHESIA HAS BEEN
ketamine anesthesia is characterized by rapid recovery and is an alternative to barbiturate anesthesia in greyhounds. In nervous or excited dogs, induction of anesthesia with diazepam and ketamine may be prolonged and require repeated dosing. Midazolam maleate is a water-soluble benzodiazepine, approximately three times as potent as d i a ~ e p a m .Mid~.~ azolam maleate compares favorably with diazepam for induction of anesthesia in humans5 The purpose of this clinical study is to compare the anesthetic, respiratory, and cardiovascular effects of diazepam-ketamine and midazolam-ketamine administered intravenously in greyhounds. Materials and Methods Fourteen splenectomized greyhound blood donor dogs from the Ohio State University College of veterinary Medicine were determined to be in good physical condition by physical examination. complete blood cell count, and a negative heartworm test. The dogs were anesthetized
for dental prophylaxis, and two dogs were castrated. Food, but not water. was withheld for 12 hours before anesthesia. A 17-gauge intravenous catheter was placed percutaneously in the cephalic vein. A balanced electrolyte solution* (5-10 mL/kg/hr) was administered to replace insensible fluid losses during anesthesia. The dogs were placed in left-lateral recumbency and were reassured b y their regular handlers' talking and petting during instrumentation and baseline recordings. The dorsomedial aspect of the right tarsus and metatarsus was shaved and prepared aseptically. The dorsal pedal artery was catheterized percutancously with a 22-gauge catheter after a local skin block with 0.5 to 1.0 mL of lidocaine (2% solution). In spite of reassurances from their handlers, the dogs remained nervous throughout instrumentation and collection of baseline data. Arterial pressures were measured with a fluid-filled pressure transducer.? The sternum was taken as the reference point for right atrial pressures. Systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) were determined intermittently from a con-
* Lactated Ringers. Travenol Inc.. Deerfield, IL t Could P23d. Could Statham. Oxnard. CA.
From the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University,Columbus, Ohio. Presented at the Veterinary Midwest Anesthesia Conference, Urbana, Illinois, June 4, 1988 Reprint requests: Peter W. Hellyer, DVM. North Carolina State University,College of Veterinary Medicine, 4700 HillsboroughStreet, Raleigh,
NC 27606.
143
144
DIAZEPAM-KETAMINE AND MIDAZOLAM-KETAMINE
tinuous pressure waveform display.$ Mean arterial pressure (MAP) was derived electronically. A bipolar electrocardiogram (lead 11) was monitored continuously. Baseline measurements included SAP, MAP, DAP, heart rate (HR), respiratory rate (RR), arterial pH and blood gases (Pa 02,Pa C O ~ ) ,and rectal body temperature. A 50/50 mixture (V/V) of either diazepam$-ketamine 11 or midazolamlT-ketamine at a dose of 1.O mL/9.1 kg ( 1.O mL/20 lbs) IV was selected randomly for each dog after baseline measurements. This drug combination resulted in a dose of 0.28 mg/kg of diazepam (2.5 mg/mL) or midazolam (2.5 mg/mL) and 5.5 mg/kg ketamine (50 mg/mL). Induction, maintenance, and recovery from general anesthesia were evaluated by one person unaware of the drug combination used. Tracheal intubation, also by one person unaware of the drug combination used, was performed when a dog had stopped chewing and licking. If intubation was not achieved within two minutes, the anesthetic drug combination was readministered once at one-fourth the original dose. Induction was classified as good, fair, or poor. A good induction was an easy transition to unconsciousness, with occasional licking and swallowing. A fair induction was characterized by paddling and vocalizing, and a poor induction consisted of paddling, vocalizing, attempts to escape, urination, and defecation. The endotracheal tube was connected to a small animal circle anesthetic system. Halothane in 100%oxygen ( 3 L/min) was delivered from an out-of-the-circle, agent-specific, precision vaporizer. Halothane was administered at a vaporizer setting of 3% and gradually reduced according to subjective signs of anesthetic depth (licking, swallowing, blinking, palpebral reflex, muscle relaxation, and jaw tone). Systolic arterial pressure, MAP, DAP, HR, RR, arterial pH and blood gases, and rectal temperature were recorded 5 , 10, and 15 minutes after the initial drug administration. Ventilation was not assisted during the 15-minute evaluation period. Anesthesia was maintained with halothane in 100% oxygen for the remainder of the procedure. Evaluation of recovery from anesthesia included time from vaporizer off to sternal recumbency, time from vaporizer off to standing, rectal temperature at the end of anesthesia, and character of recovery (good, fair, poor). A good recovery consisted of one or two attempts to stand and no thrashing, paddling, or vocalizing. A fair recovery was characterized by two to five attempts to stand, paddling, ataxia, and vocalizing. A poor recovery consisted of paddling, vocalizing, thrashing, urinating, and defecating. $ Datascope 670, Datascope Corporation, Paramus. NJ. 5 Diazepam, Elkins-Sinn, lnc. Cheny Hill, NJ. 11 Vetalar, Parke-Davis, Moms Plains, NJ. ll Versed, Hoffman-LaRoche, lnc., Nutley, NJ.
Data are expressed as means f SD. Statistical analysis was performed by using a two-way analysis of variance with comparison of multiple means based on Tukey's w procedure. A one-way analysis of variance or an unpaired Student's t Test was used to compare means between groups of dogs. Means were considered significantly different at p
