L'anesthésie intraveineuse chez le cheval: comparaison des combinaisons xylazine-kétamine et xylazine-tilétamine-zolazépam.

Intravenous anesthesia in the horse: Comparison of xylazine-ketamine and xylaxine-tiletamine-zolazepam combinations. Six healthy adult horses were anesthetized twice at random with following intravenous combinations: 1.1 mg/kg of body weight (BW) of xylazine followed by 2.2 mg/kg BW of ketamine (X-K) and 1.1 mg/kg BW of xylazine followed by 1.65 mg/kg BW of tiletamine-zolazepam (X-TZ). The modifications of some cardiorespiratory parameters and the duration of anesthesia were evaluated and compared for the 2 protocols used. Few significant differences were observed between the 2 protocols in regard to the cardiorespiratory parameters measured. The respiratory rate was lower (7 breaths per minute) and the heart rate was higher (34 beats per minute) with the X-TZ combination. The duration of anesthesia with this technique was 33 +/- 3 minutes (X +/- Sx) and longer than with X-K (18 +/- minutes (X +/- Sx)). Superficial analgesia lasted 14,5 +/- 3 minutes with the X-K combination and 31,7 +/- 3,2 minutes for the X-TZ combination. The 2 protocols are associated with a reduction of PaO2.     

Anesthesia in the Richardson's ground squirrel: comparison of ketamine, ketamine and xylazine, droperidol and fentanyl, and sodium pentobarbital

A combination of ketamine and xylazine (88.9 mg of ketamine/ml and 11.1 mg of xylazine/ml) given IM (85.5 +/- 3.4 mg of ketamine/kg of body weight and 10.6 +/- 0.5 mg of xylazine/kg) or subcutaneously (85.6 +/- 4.0 mg of ketamine/kg and 10.7 +/- 0.7 mg of xylazine/kg) induced effective surgical anesthesia for 20 to 30 minutes in Richardson's ground squirrels. Use of ketamine alone (86 +/- 7 mg/kg, IM), a droperidol and fentanyl combination (2.6 +/- 0.4 mg of droperidol/kg and 52 +/- 8 micrograms of fentanyl/kg, IM), or sodium pentobarbital (50 +/- 2 mg/kg, intraperitoneally) did not induce surgical anesthesia, but did induce depressed respiratory rates in the squirrels.     

Effects of xylazine and ketamine on the acoustic reflex and brain stem auditory-evoked response in the cat

The acoustic reflex (AR) and brain stem auditory-evoked response (BAER) were recorded in adult cats 5 minutes after IM administration of xylazine (1 mg/kg) and after IM administration of ketamine (10 mg/kg). Ipsilateral and contralateral AR were recorded at 10 and 20 dB above acoustic reflex threshold 5 minutes after xylazine administration and 5 and 35 minutes after ketamine administration. Monaural BAER were recorded 5 minutes after xylazine and 5 and 35 minutes after ketamine, using stimulus intensities of 90-, 80-, and 70-dB hearing level (HL). Additional BAER were recorded at 10, 15, and 25 minutes after ketamine, using the 90-dB HL stimulus. Pre- and postinjection comparisons were made for threshold, latency, and amplitude of the AR and for latency and amplitude of waves I through VI of the BAER. At both stimulus intensities before and after ketamine administration threshold for the ipsilateral reflex was significantly lower (P greater than 0.05) than for the contralateral reflex. The threshold, latency, and amplitude of the AR were unaffected (P greater than 0.05) by the injection of ketamine after xylazine. The amplitude of BAER waves was not affected (P greater than 0.05) by ketamine after xylazine for each of the 3 stimulus intensities. Latency of the 90-dB HL-evoked response was increased (P less than or equal to 0.05) for waves III/IV at 5 and 35 minutes after ketamine, and for wave V at each of the postinjection times, except at postinjection minute 15.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiopulmonary effects of romifidine/ketamine or xylazine/ketamine when used for short duration anesthesia in the horse

The cardiovascular changes associated with anesthesia induced and maintained with romifidine/ketamine versus xylazine/ ketamine were compared using 6 horses in a cross over design. Anesthesia was induced and maintained with romifidine (100 microg/kg, IV)/ketamine (2.0 mg/kg, IV) and ketamine (0.1 mg/kg/min, IV), respectively, in horses assigned to the romifidine/ ketamine group. Horses assigned to the xylazine/ketamine group had anesthesia induced and maintained with xylazine (1.0 mg/kg, IV)/ketamine (2.0 mg/kg, IV) and a combination of xylazine (0.05 mg/kg/min, IV) and ketamine (0.1 mg/kg/min, IV), respectively. Cardiopulmonary variables were measured at intervals up to 40 min after induction. All horses showed effective sedation following intravenous romifidine or xylazine and achieved recumbency after ketamine administration. There were no significant differences between groups in heart rate, arterial oxygen partial pressures, arterial carbon dioxide partial pressures, cardiac index, stroke index, oxygen delivery, oxygen utilization, systemic vascular resistance, left ventricular work, or any of the measured systemic arterial blood pressures. Cardiac index and left ventricular work fell significantly from baseline while systemic vascular resistance increased from baseline in both groups. The oxygen utilization ratio was higher in the xylazine group at 5 and 15 min after induction. In conclusion, the combination of romifidine/ketamine results in similar cardiopulmonary alterations as a xylazine/ketamine regime, and is a suitable alternative for clinical anesthesia of the horse from a cardiopulmonary viewpoint.     

Xylazine-ketamine-induced anesthesia in rats and its antagonism by yohimbine

A combination of xylazine and ketamine was used to anesthetize 60 male rats, and then yohimbine was given to evaluate its reversing effect on xylazine-ketamine-induced anesthesia. In experiment A, xylazine (21 mg/kg of body weight) and ketamine (45 mg/kg) were admixed and administered IM to 12 Sprague-Dawley rats. Anesthesia lasted approximately 70 minutes. The xylazine-ketamine combination also induced polyuria, bradycardia, and bradypnea. When yohimbine (2.1 mg/kg) was given intraperitoneally 20 minutes after the xylazine-ketamine injection, the rats regained consciousness and righting reflexes within approximately 10 minutes. Yohimbine also reversed the bradycardia and bradypnea and appeared to reduce the polyuria induced by the xylazine-ketamine combination. In experiment B, xylazine (15.4 mg/kg) and ketamine (33 mg/kg) were admixed and given IM to 48 Holtzman rats. The combination induced surgical anesthesia for at least 30 minutes, during which a surgical procedure involving grafting a section of the sciatic nerve into the hypothalamus was performed. In rats in which yohimbine (1 mg/kg) was given intraperitoneally 45 to 60 minutes after xylazine-ketamine administration (before natural recovery from the anesthesia), the righting reflex was apparent in less than 10 minutes.     

Analgesic and systemic effects of ketamine,xylazine, and lidocaine after subarachnoid administration in goats

OBJECTIVE: To determine the effects of ketamine hydrochloride, xylazine hydrochloride, and lidocaine hydrochloride after subarachnoid administration in goats. ANIMALS: 6 healthy goats. PROCEDURE: In each goat, ketamine (3 mg/kg), xylazine (0.1 mg/kg), lidocaine (2.5 mg/kg), and saline (0.9% NaCI) solution were injected into the subarachnoid space between the last lumbar vertebra and first sacral vertebra (time 0). Analgesic, ataxic, sedative, cardiovascular, and respiratory effects and rectal temperature were evaluated before (baseline) and 2, 5, 10, 15, and 30 minutes after administration and at 30-minute intervals thereafter as needed. RESULTS: Administration of anesthetics induced varying degrees of analgesia. Onset of the analgesic effect was more delayed for xylazine (mean +/- SD, 9.5 +/- 2.6 minutes) than for ketamine (6.7 +/- 2.6 minutes) or lidocaine (3.5 +/- 1.2 minutes). Duration of analgesia induced by xylazine (88.3 +/- 15 minutes) was twice as long as the duration of analgesia induced by ketamine (48.8 +/- 13.5 minutes) but similar to that induced by lidocaine (66.5 +/- 31 minutes). Xylazine induced bradycardia, whereas ketamine caused a nonsignificant increase in heart rate. Xylazine induced a reduction in arterial pressure, whereas ketamine or lidocaine did not affect arterial pressure. CONCLUSIONS AND CLINICAL RELEVANCE: Subarachnoid administration of xylazine in goats resulted in longer duration of analgesia of the tail, perineum, hind limbs, flanks, and caudodorsal rib areas than administration of ketamine or lidocaine. However, xylazine caused bradycardia and respiratory depression. Additional studies are needed to determine whether the analgesia would be sufficient to allow clinicians to perform surgical procedures.     

A comparative study of medetomidine/ketamine and xylazine/ketamine anaesthesia in dogs

The anaesthetic and physiological effects of a combination of 40 micrograms medetomidine with 2.5 ketamine, 5.0 or 7.5 mg/kg administered intramuscularly were compared with the effects of a combination of 1 mg/kg xylazine and 15 mg/kg ketamine. All the combinations rapidly induced an anaesthetic state that permitted endotracheal intubation, with the absence of the pedal reflex and with good muscle relaxation, and induced bradycardia that was less pronounced as the dose of ketamine was increased. All the combinations produced a decrease in respiratory rate. Increasing the dose of ketamine combined with medetomidine resulted in a very significant prolongation of the duration of anaesthesia, the duration of muscle relaxation and the arousal time. The duration of the anaesthetic effects of 40 micrograms/kg medetomidine with 5 mg/kg ketamine was comparable to that provided by the recommended xylazine/ketamine combination but the period of muscle relaxation was significantly longer. The recovery from medetomidine/ketamine took longer than recovery from xylazine/ketamine but there were fewer side effects.     

The parasympatholytic effects of atropine sulfate and glycopyrrolate in rats and rabbits.

Nine groups of rats (n = 5 per group) received an intramuscular (IM) injection of one of the following drugs or drug combinations: saline, atropine (0.05 mg/kg), glycopyrrolate (0.5 mg/kg), ketamine:xylazine (85:15 mg/kg), ketamine:detomidine (60:10 mg/kg), atropine:ketamine:xylazine (0.05: 85:15 mg/kg), glycopyrrolate: ketamine:xylazine (0.5:85:15 mg/kg), atropine:ketamine:detomidine (0.05: 60:10 mg/kg) or glycopyrrolate: ketamine:detomidine (0.5:60:10). Similarly six groups of rabbits (n = 5) received an IM injection of either saline, atropine (0.2 mg/kg), atropine (2 mg/kg), glycopyrrolate (0.1 mg/kg), ketamine:xylazine (35:10 mg/kg) or glycopyrrolate:ketamine:xylazine (0.1:35:10 mg/kg). In rats, atropine sulfate (0.05 mg/kg) and glycopyrrolate (0.5 mg/kg) produced an increase in heart rate for 30 and 240 min, respectively. In rabbits atropine sulfate at either 0.2 or 2.0 mg/kg did not induce a significant increase in heart rate, but glycopyrrolate (0.1 mg/kg) elevated the heart rate above saline treated animals for over 50 min. Both atropine and glycopyrrolate provided protection against a decrease in heart rate in rats anesthetized with ketamine: xylazine (85:15 mg/kg) or ketamine: detomidine (60:10 mg/kg); however, glycopyrrolate was significantly more effective in maintaining the heart rate within the normal range. Glycopprrolate also prevented a decrease in heart rate in rabbits anesthetized with ketamine:xylazine (35:5 mg/kg). Neither glycopyrrolate nor atropine influenced respiration rate, core body temperature or systolic blood pressure when used alone or when combined with the injectable anesthetic. Glycopyrrolate is an effective anticholinergic agent in rabbits and rodents and more useful as a preanesthetic agent than atropine sulfate in these animals.     

Comparative study of three intramuscular anaesthetic combinations (medetomidine/ketamine, medetomidine/fentanyl/midazolam and xylazine/ketamine) in rabbits

OBJECTIVE: To compare the quality of surgical anaesthesia and cardiorespiratory effects of three intramuscular (IM) anaesthetic combinations in rabbits. STUDY DESIGN: Prospective randomized cross-over experimental study. ANIMALS: Nineteen adult female chinchilla mixed-bred rabbits weighing 3.9 +/- 0.8 kg. METHODS: Rabbits were given one of three IM anaesthetic combinations: 0.25 mg kg(-1) medetomidine and 35.0 mg kg(-1) ketamine (M-K), 0.20 mg kg(-1) medetomidine and 0.02 mg kg(-1) fentanyl and 1.0 mg kg(-1) midazolam (M-F-Mz) and 4.0 mg kg(-1) xylazine and 50 mg kg(-1) ketamine (X-K). The effects of anaesthesia on nociceptive reflexes, circulatory and respiratory function were recorded. Statistical analyses involved repeated measures anova with paired Student's t-test applied post hoc. P-values <0.05 were considered as significant. RESULTS: Reflex loss was most rapid and complete in M-K recipients, whereas animals receiving M-F-Mz showed the longest tolerance of endotracheal intubation (78.1 +/- 36.5 minutes). Loss of righting reflex was significantly most rapid (p < 0.05) in the X-K group (114.7 +/- 24.0 minutes). Surgical anaesthesia was achieved in 16 of 19 animals receiving M-K, in 14 animals receiving M-F-Mz, and in seven animals with X-K, but only for a short period (7.1 +/- 11.6 minutes). This was significantly (p < 0.001) shorter than with M-K (38.7 +/- 30.0 minutes) and M-F-Mz (31.6 +/- 26.6 minutes). Heart rates were greatest in X-K recipients; lowest HR were seen in animals receiving M-F-Mz. Mean arterial blood pressure was significantly higher (about 88 mmHg) during the first hour in the M-K group. During recovery, the greatest hypotension was encountered in the X-K group; minimum values were 53 +/- 12 mmHg. Six of 19 animals in the M-F-Mz group showed a short period of apnoea (30 seconds) immediately after endotracheal intubation. Respiratory frequency was significantly lower in this group (p < 0.001). Highest values for arterial carbon dioxide partial pressures (PaCO(2)) (6.90 +/- 0.87 kPa; 52.5 +/- 6.5 mmHg) occurred after induction of anaesthesia in group M-F-Mz animals. There was a marked decrease in PaO(2) in all three groups (the minimum value 5.28 +/- 0.65 kPa [39.7 +/- 4.9 mmHg] was observed with M-K immediately after injection). Arterial PO(2) was between 26.0 and 43.0 kPa (196 and 324 mmHg) in all groups during O(2) delivery and decreased - but not <7.98 kPa - on its withdrawal. Immediately after drug injection, pH(a) values fell in all groups, with lowest values after 30 minutes (7.23 +/- 0.03 with M-K, 7.28 +/- 0.05 with M-F-Mz, and 7.36 +/- 0.04 with X-K). The X-K animals showed significantly (p < 0.001) higher pH values than medetomidine recipients. During 1 hour of anaesthesia pH values in the medetomidine groups remained below those of the X-K group. CONCLUSIONS: Surgical anaesthesia was induced in most animals receiving medetomidine-based combinations. Arterial blood pressure was maintained at baseline values for about 1 hour after M-K. Transient apnoea occurred with M-F-Mz and mandates respiratory function monitoring. Oxygen enrichment of inspired gases is necessary with all three combinations. Endotracheal intubation is essential in rabbits receiving M-F-Mz. CLINICAL RELEVANCE: The quality of surgical anaesthesia was greatest with M-K. All combinations allowed recoveries of similar duration. It is theoretically possible to antagonize each component of the M-F-Mz combination.     

Alterations in epinephrine-induced arrhythmogenesis after xylazine and subsequent yohimbine administration in isoflurane-anesthetized dogs

Effects of xylazine (1.1 mg/kg of body weight, IV bolus, plus 1.1 mg/kg/h infusion) and subsequent yohimbine (0.125 mg/kg, IV bolus) administration on the arrhythmogenic dose of epinephrine (ADE) in isoflurane (1.8% end-tidal)-anesthetized dogs were evaluated. The ADE was defined as the total dose of epinephrine that induced greater than or equal to 4 premature ventricular contractions within 15 seconds during a 3-minute infusion period or within 1 minute after the end of infusion. Total ADE values during isoflurane anesthesia, after xylazine administration, and after yohimbine injection were 36.6 +/- 8.45 micrograms/kg, 24.1 +/- 6.10 micrograms/kg, and 45.7 +/- 6.19 micrograms/kg, respectively. Intravenous xylazine administration significantly (P less than 0.05) increased blood pressure and decreased heart rate, whereas yohimbine administration induced a significant (P less than 0.05) decrease in blood pressure. induced a significant (P less than 0.05) decrease in blood pressure. After yohimbine administration, the ADE significantly (P less than 0.05) increased above that after isoflurane plus xylazine administration. After yohimbine administration, blood pressure measured immediately before epinephrine-induced arrhythmia was significantly (P less than 0.05) less than the value recorded during isoflurane plus xylazine anesthesia. Heart rate was unchanged among treatments immediately before epinephrine-induced arrhythmia. Seemingly, yohimbine possessed a protective action against catecholamine-induced arrhythmias in dogs anesthetized with isoflurane and xylazine.     

Xylazine-Ketamine and Detomidine-Tiletamine-Zolazepam Anesthesia in Horses

Eight horses were anesthetized three times, by intravenous administration of xylazine (1.1 mg/kg) and ketamine (2.2 mg/kg), detomidine (0.02 mg/kg) and tiletamine-zolazepam (1.1 mg/kg), or detomidine (0.04 mg/kg) and tiletamine-zolazepam (1.4 mg/kg). The sequences were randomized. The duration of analgesia and the times to sternal and standing positions were recorded. Heart rate, arterial pressure, pHa, PaCO2, and PaO2 were measured before and during anesthesia. The duration of analgesia with the two doses of detomidine-tiletamine-zolazepam, 26 +/- 4 minutes and 39 +/- 11 minutes, respectively, was significantly longer than the 13 +/- 6 minutes obtained with xylazine-ketamine. Bradycardia occurred after administration of detomidine, but heart rates returned to baseline values 5 minutes after administration of tiletamine and zolazepam. Arterial pressure was significantly higher and PaO2 significantly lower during anesthesia with detomidine-tiletamine-zolazepam than with xylazine-ketamine. Some respiratory acidosis developed with all anesthetic combinations. The authors conclude that detomidine-tiletamine-zolazepam can provide comparable anesthesia of a longer duration than xylazine and ketamine, but hypoxemia will develop in some horses.     

Effect of tolazoline on xylazine-ketamine-induced anesthesia in turkey vultures

Fifteen turkey vultures were each given xylazine (1 mg/kg of body weight, IM) and ketamine (10 mg/kg, IM). In 5 of the birds (controls), the mean (+/- SD) induction time was 5.4 +/- 1.0 minutes and the mean duration of anesthesia was 109.8 +/- 25.4 minutes. The remaining 10 vultures (test birds) were given tolazoline (15 mg/kg, IV) 45 minutes after administration of xylazine and ketamine. In the test birds, the mean induction time was 4.5 +/- 1.6 minutes and the mean duration of anesthesia was 49 +/- 2.1 minutes. After administration of tolazoline, the birds regained consciousness in 3.7 +/- 1.9 minutes and were standing with normal posture in 14.2 +/- 5.4 minutes. All birds remained moderately sedated yet ambulatory and responsive to stimuli for 30 to 60 minutes after tolazoline administration. Results indicated that tolazoline was useful in controlling the duration of xylazine-ketamine-induced anesthesia in turkey vultures.     

Pre-emptive epidural ketamine or S(+)-ketamine in post-incisional pain in dogs: a comparative study

OBJECTIVE: To compare the pre-emptive analgesic effects of epidural ketamine or S(+)-ketamine on post-incisional hyperalgesia. STUDY DESIGN: Prospective randomized study. ANIMALS: Twenty-four mongrel dogs (1-5 years, weighing 11.9+/-1.8 kg). METHODS: Dogs were anesthetized with propofol (5 mg/kg intravenously) and a lumbosacral epidural catheter was placed. Dogs were randomly allocated to 3 groups, each with 8 dogs. The control group (CG) was administered saline solution (0.3 mL/kg); the ketamine group (KG) ketamine (0.6 mg/kg); and the S(+)-ketamine group (SG) S(+)-ketamine (0.6 mg/kg). The final volume was adjusted to 0.3 mL/kg in all groups. Five minutes after the epidural injection a surgical incision was made in the common pad of the right hind limb and was immediately closed with simple interrupted nylon suture. Respiratory (RR) and heart (HR) rates, rectal temperature (T), sedation (S), lameness score, and mechanical nociceptive threshold by von Frey filaments were evaluated before the propofol anesthesia and at 15, 30, 45, 60, 75, and 90 minutes and then at 2, 4, 6, 8, 12, and 24 hours after epidural injection. RESULTS: There were no differences in RR, HR, T, or S between groups. Motor blockade of the hind limbs was observed during 20+/-3.6 minutes in KG and during 30.6+/-7.5 minutes in SG (mean+/-SD). Mechanical force applied to obtain an aversive response was higher from 45 minutes to 12 hours in KG and from 60 to 90 minutes in SG, when compared with CG. CONCLUSIONS: Pre-emptive epidural ketamine induced no alterations in RR and HR, and reduced post-incisional hyperalgesia for a longer time than did S(+) ketamine. CLINICAL RELEVANCE: Although anesthetic and analgesic potency of S(+) ketamine is twice that of ketamine, the racemic form is seemingly better for post-incisional hyperalgesia.     

Hemodynamics in the guinea pig after anesthetization with ketamine/xylazine

The resting hemodynamics were determined in 8 guinea pigs after they were anesthetized with ketamine/xylazine. Measurements were made of blood pressure, heart rate, cardiac output, arterial blood gases, and pH. These measurements were obtained initially at 4 to 5 hours after an injection (IM) of ketamine HCl (25 mg) and xylazine (0.15 mg) was given to anesthetize the animals for catheterization (period 1), again 5 days after the operation (period 2), and finally 4 to 5 hours after a 2nd injection of ketamine/xylazine (period 3). There were no differences in heart rates, respiratory rates, or cardiac outputs among the 3 study periods. However, arterial blood pressure was slightly, but significantly, lowered after, and presumably due to, instrumentation (62 +/- 4 mm of Hg, P less than 0.05) when compared with the 5-day postoperative period (67 +/- 7 mm of Hg) or after the readministration of anesthetics (66 +/- 7 mm of Hg). The partial pressure of carbon dioxide in the arterial blood was slightly lower (4 mm of Hg, P less than 0.05) in both acutely postanesthetic periods (period 1 and period 3) than in the same animals at postoperative day 5 (period 2). This study has demonstrated that resting hemodynamics measured shortly after this anesthesia with ketamine/xylazine are not largely different from those in chronically instrumented animals.     

Effect of yohimbine on xylazine-ketamine anesthesia in cats

Xylazine and ketamine are an anesthetic combination used in feline practice for routine surgical procedures. In a controlled study, we evaluated the effects of yohimbine, an antagonist of xylazine, on the anesthesia induced by this anesthetic combination in cats. Two intramuscular doses of xylazine and ketamine (2.2 mg of xylazine/kg plus 6.6 mg of ketamine/kg and 4.4 mg of xylazine/kg plus 6.6 mg of ketamine/kg) caused approximately 60 and 100 minutes of anesthesia, respectively, in control cats. When yohimbine (0.1 mg/kg) was given intravenously 45 minutes after ketamine administration, the cats regained consciousness within 3 minutes. They were ambulatory 1 to 2 minutes after regaining consciousness. Yohimbine also reversed the bradycardia and respiratory depression elicited by xylazine-ketamine. The results indicated that yohimbine may be useful for controlling the duration of xylazine-ketamine anesthesia in cats.     

Influence of three anesthetic protocols on glomerular filtration rate in dogs

OBJECTIVE: To investigate renal function in clinically normal dogs when awake and during anesthesia with medetomidine; xylazine, ketamine, and halothane (XKH) combination; or propofol. ANIMALS: 10 adult female Beagles. PROCEDURES: At intervals of 15 days, dogs were administered medetomidine (0.05 mg/kg, IV); XKH combination (xylazine [1 mg/kg, IV], ketamine [5 mg/kg, IV], and halothane [1% end-tidal concentration]); or propofol (6 mg/kg, IV) to induce anesthesia or no treatment. Glomerular filtration rate was assessed on the basis of renal uptake (RU; determined via renal scintigraphy) and plasma clearance (CL) of technetium 99m-labeled diethylenetriamine pentaacetic acid ((99m)Tc-DTPA). RESULTS: In awake dogs, mean +/- SEM RU was 9.7 +/- 0.4% and CL was 3.86 +/- 0.23 mL/min/ kg. Renal uptake and CL of (99m)Tc-DTPA were not significantly modified by administration of XKH (RU, 11.4 +/- 0.9%; CL, 4.6 +/- 0.32 mL/min/kg) or propofol (RU, 9.7 +/- 0.3%; CL, 3.78 +/- 0.37 mL/min/kg). Half-life elimination time of plasma (99m)Tc-DTPA decreased significantly in XKH-anesthetized dogs, compared with the value in awake dogs (14.4 minutes and 28.9 minutes, respectively). However, glomerular filtration rate was significantly decreased by administration of medetomidine (RU, 3.9 +/- 0.1%), and the time to maximum kidney activity was significantly increased (867 +/- 56 seconds vs 181 +/- 11 seconds without anesthesia). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that anesthesia with propofol or an XKH combination did not alter renal function in healthy Beagles, but anesthesia with medetomidine decreased early RU of (99m)Tc-DTPA.     

Antagonism of ketamine-xylazine anesthesia in rats by administration of yohimbine, tolazoline, or 4-aminopyridine

Antagonism of ketamine-xylazine (85 mg of ketamine/kg of body weight and 15 mg of xylazine/kg, IM) anesthesia in rats by yohimbine (YOH; 1, 5, 10, and 20 mg/kg, IP), tolazoline (TOL; 10, 20, or 50 mg/kg, IP), 4-aminopyridine (4-AP; 1 or 5 mg/kg, IP), or a combination of yohimbine and 4-aminopyridine (YOH:4-AP, 1 mg/kg:1 mg/kg or 5 mg/kg:1 mg/kg, IP) was studied. All dosages of YOH, TOL, 4-AP, and YOH:4-AP reduced the time to appearance of corneal and pedal reflexes. Only TOL was effective in reducing time to appearance of the crawl reflex and recovery time. Yohimbine, 4-AP, YOH:4-AP, and TOL were effective in reversing respiratory depression caused by ketamine-xylazine anesthesia, but anesthetic-induced hypothermia was not antagonized. When given to non-anesthetized rats, the antagonists had little influence on respiratory rate, but all antagonists caused significant (P less than 0.05) reduction in core body temperature for at least 90 minutes. When YOH was used as an anesthetic antagonist at dosage of 20 mg/kg, 20% mortality was observed and was attributable to acute respiratory arrest. The use of 4-AP and YOH:4-AP at the dosages studied induced moderate to severe muscular tremors. In conclusion, TOL at dosage of 20 mg/kg given IP, appears to be an appropriate antagonist for ketamine-xylazine anesthesia in rats.     

Effects of ketamine, xylazine, and a combination of ketamine and xylazine in Pekin ducks

Effects of ketamine, xylazine, and a combination of ketamine and xylazine were studied in 12 male Pekin ducks (7 to 12 weeks old; mean [+/- SD] body weight, 3.1 +/- 0.3 kg). After venous and arterial catheterization and fixation of a temperature probe in the cloaca, each awake duck was confined, but not restrained, in an open box in a dimly lit room. Blood pressure and lead-II ECG were recorded. Three arterial blood samples were collected every 15 minutes over a 45-minute period (control period) and were analyzed for pHa, PaCO2 and PaO2. After the control period, each duck was assigned at random to 1 of 3 drug groups: (1) ketamine (KET; 20 mg/kg of body weight, IV), (2) xylazine (XYL; 1 mg/kg, IV), and (3) KET + XYL (KET 20 mg/kg and XYL, 1 mg/kg; IV). Measurements were made at 1, 5, 10, 15, 30, 45, 60, and 90 minutes after drug administration. All ducks survived the drug study. Cloacal temperature was significantly (P less than or equal to 0.05) increased above control cloacal temperature at 90 minutes after the administration of ketamine, and from 10 through 90 minutes after administration of ketamine plus xylazine. In ducks of the KET group, pHa, PaCO2, and PaO2, remained unchanged after administration of the drug. In ducks of the XYL group, pHa and PaO2 decreased significantly (P less than or equal to 0.05) from control values for all time points up to and including 15 minutes after drug administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relative potency of ketamine and S(+)-ketamine in dogs

The aim of this study was to determine the relative potency of racemic ketamine and S(+)-ketamine for the hypnotic effect and to evaluate the clinical anesthesia produced by equianesthetic doses of these two substances in dogs. One hundred and eight dogs were allocated in groups R2, R2.5, R3, R6, R9, R12, S2, S2.5, S3, S6, S9, and S12, to receive by intravenous route 2, 2.5, 3, 6, 9, and 12 mg/kg of ketamine or S(+)-ketamine, respectively. A dose-effect curve was drawn with the dose logarithm and the percentage of dogs that presented hypnosis in each group. The curve was used to obtain a linear regression, to determine the effective doses 100 and the potency relationship. In another experimental phase, eight groups of five dogs received 3, 6, 9 and 12 mg/kg of ketamine or S(+)-ketamine to evaluate the periods of latency, hypnosis, and total recovery. The times in which the dogs reached the sternal position, attempted to stand up for the first time, recovered the standing position, and started to walk were also recorded. The hypnotic dose for ketamine was 9.82 +/- 3.02 (6.86-16.5) mg/kg and for S(+)-ketamine was 7.76 +/- 2.17 (5.86-11.5) mg/kg. The time of hypnosis was longer in R3 and the first attempt to stand up occurred early in R6 when compared with S3 and S6 respectively. When R9 (100% of hypnosis with ketamine) and S6 [100% of hypnosis with S(+)-ketamine] were compared (1:1.5 ratio), the time to sternal position (12 +/- 2.5 and 20.2 +/- 5.6 min respectively) and the total recovery time (45 +/- 5.5 and 60.2 +/- 5.2 min respectively) were significantly shorter with S(+)-ketamine. It was concluded that the potency ratio between ketamine and S(+)-ketamine in dogs is smaller than the one reported in other species, and that the dose obtained after a reduction of 50%, as usually performed in humans, would not be enough to obtain equianesthetic effects in dogs.     

Use of ketamine, xylazine, and diazepam anesthesia with retrobulbar block for phacoemulsification in dogs

Objective  The study was undertaken to evaluate the use of ketamine, xylazine, and diazepam along with a local retrobulbar nerve block for routine phacoemulsification in the dog.
Animals  Ten clinically healthy mixed-breed dogs of either sex, weighing between 10 and 15 kg.
Procedures  Ten mixed-breed dogs were selected for unilateral cataract removal by phacoemulsification. Standard preoperative preparations for cataract surgery were followed. Pre-anesthetic medication consisted of atropine sulfate (0.02 mg/kg, SC). Anesthesia was induced by xylazine HCl (1.0 mg/kg, IM) followed by ketamine (5.0 mg/kg, IM). Anesthesia was maintained subsequently with IV ketamine and diazepam to effect and depth of anesthesia was assessed clinically by pedal reflex and jaw reflex. After induction of anesthesia, a retrobulbar nerve block was performed using 2 mL of 2% lignocaine. Eye position was graded after retrobulbar block and IOP was examined preoperative, post-anesthetic, 6 h postoperative and 24 h after surgery. Phacoemulsification was performed using the phaco-chop technique and an intraocular lens was placed. Anesthetic recovery and postoperative recovery following surgery was recorded.
Result  The exposure of the globe in all the dogs was adequate; the desired central fixation of the eye was obtained and surgery could be performed uneventfully. The mean IOP recorded after induction of anesthesia was 15.75 ± 0.82, which was not significantly ( P  > 0.01) different from pre-anesthetic values (14.85 ± 0.85).
Conclusion  Phacoemulsification was successfully performed with this anesthetic regimen without encountering major intraoperative or anesthetic complications.