Comparison of the cardiorespiratory effects of medetomidine-butorphanol-ketamine and medetomidine-butorphanol-midazolam in patas monkeys (Erythrocebus patas).

The cardiorespiratory effects, effectiveness, and reversibility of two injectable anesthetic combinations were compared in captive patas monkeys (Erythrocebus patas). Seven patas monkeys were hand-injected with medetomidine (40 microg/kg, i.m.), butorphanol (0.4 mg/kg. i.m.), and ketamine (3.0 mg/kg. i.m.), and seven were injected with the same dosages of medetomidine and butorphanol plus midazolam (0.3 mg/kg, i.m.). Heart rates decreased in monkeys in both treatment groups and were lower than those previously recorded in patas monkeys anesthetized with either ketamine or ketamine and isoflurane. Mean arterial pressures were highest in ketamine-treated monkeys but remained within normal limits for both groups. End tidal CO2 values increased gradually over time in both groups and were above physiologic norms after 20 min. Respiratory rates were similar between groups and remained constant throughout the procedures. Despite adequate ventilation parameters, initial low percent oxygen-hemoglobin saturation (SpO2) values were suggestive of severe hypoxemia. It was not clear whether these were accurate readings or an artifact of medetomidine-induced peripheral vasoconstriction. Oxygen supplementation restored SpO2 values to normal (>94%) in both groups. Both combinations effectively produced a state of light anesthesia, although spontaneous recoveries occurred after 30 min in three ketamine-treated monkeys. All monkeys were given i.m. atipamezole (0.2 mg/kg) and naloxone (0.02 mg/kg), whereas midazolam-treated monkeys also received flumazenil (0.02 mg/kg, i.v.), which resulted in faster (median recovery time = 5 min) and more complete recoveries in this group. Both combinations are safe to use when supplemented with oxygen, although the midazolam combination provided a longer anesthetic period and was more fully reversible.     

Cardiopulmonary assessment of medetomidine, ketamine, and butorphanol anesthesia in captive Thomson's gazelles (Gazella thomsoni).

This investigation evaluated the cardiopulmonary effects of medetomidine, ketamine, and butorphanol anesthesia in captive juvenile Thomson's gazelles (Gazella thomsoni). Butorphanol was incorporated to reduce the dose of medetomidine necessary for immobilization and minimize medetomidine-induced adverse cardiovascular side effects. Medetomidine 40.1 +/- 3.6 microg/kg, ketamine 4.9 +/- 0.6 mg/kg, and butorphanol 0.40 +/- 0.04 mg/kg were administered intramuscularly by hand injection to nine gazelles. Times to initial effect and recumbency were within 8 min postinjection. Cardiopulmonary status was monitored every 5 min by measuring heart rate, respiratory rate, indirect blood pressure, end-tidal CO2, and indirect oxygen-hemoglobin saturation by pulse oximetry. Venous blood gases were collected every 15 min postinjection. Oxygen saturations less than 90% in three gazelles suggested hypoxemia. Subsequent immobilized gazelles were supplemented with intranasal oxygen throughout the anesthetic period. Sustained bradycardia (<60 beats per minute, as compared with anesthetized domestic calves, sheep, and goats) was noted in eight of nine gazelles. Heart and respiratory rates and rectal temperatures decreased slightly, whereas systolic, mean, and diastolic blood pressure values were consistent over the anesthetic period. Mild elevations in end tidal CO2 and PCO2 suggested hypoventilation. Local lidocaine blocks were necessary to perform castrations in all seven of the gazelles undergoing the procedure. Return to sternal recumbency occurred within 7 min and return to standing occurred within 12 min after reversal with atipamezole (0.2 +/- 0.03 mg/kg) and naloxone (0.02 +/- 0.001 mg/kg). Medetomidine, ketamine, and butorphanol can be used to safely anesthetize Thomson's gazelles for routine, noninvasive procedures. More invasive procedures, such as castration, can be readily performed with the additional use of local anesthetics.     

Romifidine, medetomidine or xylazine before propofol-halothane-N2O anesthesia in dogs.

The objective of this paper was to evaluate romifidine as a premedicant in dogs prior to propofol-halothane-N2O anesthesia, and to compare it with the other alpha2-agonists (medetomidine and xylazine). For this, ten healthy dogs were anesthetized. Each dog received 3 preanesthetic protocols: atropine (10 microg/kg BW, IM), and as a sedative, romifidine (ROM; 40 microg/kg BW, IM), xylazine (XYL; 1 microg/kg, IM), or medetomidine (MED; 20 microg/kg BW, IM). Induction of anesthesia was delivered with propofol 15 min later and maintained with halothane and N2O for one hour in all cases. The following variables were registered before preanesthesia, 10 min after the administration of preanesthesia, and at 5-minute intervals during maintenance: PR, RR, rectal temperature (RT), MAP, SAP, and DAP. During maintenance, arterial oxygen saturation (SpO2), end-tidal CO2 (EtCO2) and percentage of halothane necessary for maintaining anesthesia (%HAL) were also recorded. Induction dose of propofol (DOSE), time to extubation (TE), time to sternal recumbency (TSR) and time to standing (TS) were also registered. The statistical analysis was carried out during the anesthetic period. ANOVA for repeat measures revealed no differences between the 3 groups for PR and RR; however, MAP, SAP and DAP were higher in the MED group; SpO2 was lower in MED and EtCO2 was lower in ROM; %HAL was higher in XYL. No statistical differences were observed in DOSE, TE, TSR or TS. Percentage of halothane was lower in romifidine and medetomidine than in xylazine premedicated dogs also anesthetized with propofol. All the cardiorespiratory variables measured were within normal limits. The studied combination of romifidine, atropine, propofol, halothane and N2O appears to be a safe and effective drug combination for inducing and maintaining general anesthesia in healthy dogs.     

Comparison of romifidine and medetomidine pre-medication in propofol-isoflurane anaesthetised dogs

The objective of this paper was to evaluate romifidine as a pre-medicant in dogs prior to propofol-isoflurane anaesthesia, and to compare it with medetomidine. For this, eight healthy dogs were anaesthetised. Each dog received three pre-anaesthetic protocols: R40 (romifidine, 40 microg/kg, IV), R80 (romifidine, 80 microg/kg, IV) or MED (medetomidine, 10 microg/kg, IV). Induction of anaesthesia was delivered with propofol and maintained with isoflurane. The following variables were studied before sedative administration and 10 min after sedative administration: heart rate (HR), mean arterial pressure (MAP), systolic arterial pressure (SAP) and diastolic arterial pressure (DAP) and respiratory rate (RR). During maintenance, the following variables were recorded at 5-min intervals: HR, MAP, SAD, DAP, arterial oxygen saturation (SpO(2)), end-tidal CO(2)(EtCO(2)), end-tidal concentration of isoflurane (EtISO) required for maintenance of anaesthesia and tidal volume (TV). Time to extubation, time to sternal recumbency and time to standing were also registered. HR and RR experimented a significantly decreased during sedation in all protocols respect to baseline values. Mean HR, MAP, SAP, DAP, SpO(2), EtCO(2), and TV during anaesthesia were similar for the three protocols. End tidal of isoflurane concentration was statistically similar for all protocols. Recovery time for R40 was significantly shorter than in R80 and MED. The studied combination of romifidine, propofol and isoflurane appears to be an effective drug combination for inducing and maintaining general anaesthesia in healthy dogs.     

Cardiopulmonary and anesthetic effects of medetomidine-ketamine-butorphanol and antagonism with atipamezole in servals (Felis serval).

Seven (three male and four female) 4-7-yr old captive servals (Felis serval) weighing 13.7 +/- 2.3 kg were used to evaluate the cardiopulmonary and anesthetic effects of combined intramuscular injections of medetomidine (47.4 +/- 10.3 microg/kg), ketamine (1.0 +/- 0.2 mg/kg), and butorphanol (0.2 +/- 0.03 mg/kg). Inductions were smooth and rapid (11.7 +/- 4.3 min) and resulted in good muscle relaxation. Significant decreases in heart rate (85 +/- 12 beats/min) at 10 min after injection and respiratory rate (27 +/- 10 breaths/min) at 5 min after injection continued throughout the immobilization period. Rectal temperature and arterial blood pressure did not change significantly. The PaO2 decreased significantly, and PaCO2 increased significantly during immobilization but remained within clinically acceptable limits. Hypoxemia (PaO2 < 60 mm Hg) was not noted, and arterial blood oxygen saturation (SaO2) was greater than 90% at all times. Relative arterial oxygen saturation (SpO2) values, indicated by pulse oximetry, were lower than SaO2 values. All animals could be safely handled while sedated. Administration of atipamezole (236.8 +/- 51.2 microg/kg half i.v. and half s.c.), an alpha2 antagonist, resulted in rapid (4.1 +/- 3 min to standing) and smooth recoveries.     

A comparison of two field chemical immobilization techniques for bobcats (Lynx rufus)

Anesthetic protocols that allow quick induction, short processing time, and rapid reversal are necessary for researchers performing minimally invasive procedures (including morphometric measurements or attachment of radiocollars). The objective of this study was to evaluate the effectiveness of medetomidine and butorphanol as a substitute for xylazine in ketamine-based field immobilization protocols for bobcats (Lynx rufus) to reduce recovery and total field times. During 2008 and 2009, 11 bobcats were immobilized with an intramuscular combination of ketamine (10 mg/kg)-xylazine (0.75 mg/kg) (KX) or ketamine (4 mg/kg)-medetomidine (40 mcg/kg)-butorphanol (0.4 mg/kg) (KMB). Time to initial sedation, recumbency, and full anesthesia were recorded postinjection. Time to head up, sternal, standing, full recovery, and total processing times were recorded post-reversal. Throughout anesthesia, heart rate (HR), respiratory rate (RR), rectal temperature (RT), and noninvasive hemoglobin-oxygen saturation (SpO2) were recorded at 5-min intervals. The KX combination had a median time to full anesthesia of 10 min, a median recovery time of 46 min, and a median total processing time of 83 min. Alternatively, the KMB combination had a median time to full anesthesia of 21 min, a median recovery time of 18 min, and a median total processing time of 64 min. The KX protocol produced a median HR of 129 beats/min, RR of 25 breaths/min, RT of 38.3 degrees C, and SpO2 of 93%. The KMB protocol produced a median HR of 97 beats/min, RR of 33 breaths/min, RT of 38.4 degrees C, and SpO2 of 92%. Though both protocols provided safe and reliable sedation, the benefits of using medetomidine and butorphanol to lower ketamine doses and decrease processing time for brief nonsurgical sedation of bobcats in the field are presented.     

Reversible anesthesia of captive California sea lions (Zalophus californianus) with medetomidine, midazolam, butorphanol, and isoflurane.

Two adult California sea lions (Zalophus californianus) were effectively anesthetized 13 times with medetomidine (0.010-0.013 mg/kg), midazolam (0.2-0.26 mg/kg), and butorphanol (0.2-0.4 mg/kg) by i.m. hand or pole syringe injection. For each anesthetic event, atropine (0.02 mg/kg, i.m.) was administered 6-20 min after initial injections, and oxygen administration via face mask or nasal insufflation began at the same time. Light anesthesia was induced in 8-22 min and lasted 13-78 min. During eight of the procedures, isoflurane (0.5-2.0%) was administered via face mask or endotracheal tube for an additional 30-120 min to facilitate longer procedures or surgery. Anesthesia was antagonized with atipamezole (0.05-0.06 mg/kg) and naltrexone (0.1 mg/kg) in seven events, with the addition of flumazenil (0.0002-0.002 mg/kg) in six events. The antagonists were administered by i.m. injection 42-149 min after administration of the induction agents. All sea lions recovered to mild sedation within 4-17 min after administration of the antagonists.     

Anesthesia of male axis deer (Axis axis): evaluation of thiafentanil, medetomidine, and ketamine versus medetomidine and ketamine.

Thiafentanil oxalate, previously known as A-3080, is a synthetic opioid used for chemical immobilization of a variety of nondomestic hoofstock species. This study compared the combination of thiafentanil oxalate, medetomidine, and ketamine (TMK; 0.09 +/- 0.02 mg/kg, 0.01 +/- 0.003 mg/kg, and 1.36 +/- 0.33 mg/kg, respectively) with the combination of medetomidine and ketamine (MK; 0.09 +/- 0.02 mg/kg and 3.48 +/- 0.55 mg/kg, respectively) for anesthetization of 17 captive male axis deer (Axis axis) for vasectomy. Nine deer received TMK and eight deer received MK via projectile syringe during the months of January and February, 2005. Mean induction and arousal times, vital signs, and arterial blood gas values were monitored and compared. All animals received supplemental oxygen during the surgical procedure. Animals receiving TMK were reversed with naltrexone (100 mg/mg thiafentanil) and atipamazole (5 mg/mg medetomidine). Animals receiving MK were reversed with atipamazole (5 mg/mg medetomidine). Two MK animals and three TMK animals required supplementation with ketamine i.v. immediately upon handling. Six of the nine animals immobilized with TMK required intubation for positive-pressure ventilation. Two of these six animals also required isoflurane to maintain anesthesia. Mean induction time was 3.5 +/- 2.0 min in the TMK group, and 9.8 +/- 6.7 min in the MK group. Despite shorter mean induction times, animals anesthetized with TMK experienced unpredictable inductions, apnea, muscle rigidity, limb movement, and significant respiratory and metabolic lactic acidosis. MK resulted in smoother inductions, better respiratory function, and less adverse metabolic disturbances, and thus was considered superior to TMK for anesthesia in captive axis deer at the dosages tested.     

Comparison of the efficacy and cardiorespiratory effects of medetomidine-based anesthetic protocols in ring-tailed lemurs (Lemur catta).

The relative efficacies and cardiorespiratory effects of three injectable anesthetic combinations containing medetomidine were evaluated in ring-tailed lemurs (Lemur catta). In addition, the direct effects of medetomidine on heart rate and blood pressure were evaluated in lemurs anesthetized with isoflurane. For injectable anesthesia, captive adult ring-tailed lemurs were anesthetized with medetomidine and ketamine (0.04-0.06 mg/kg, i.m. and 3 mg/kg, i.m., respectively), medetomidine, butorphanol, and ketamine (0.04 mg/kg, i.m., 0.4 mg/kg, i.m., and 3 mg/kg, i.m., respectively), or medetomidine, butorphanol, and midazolam (0.04 mg/kg, i.m., 0.4 mg/kg, i.m., and 0.3 mg/kg, i.m., respectively). For inhalation anesthesia, lemurs were mask-induced and maintained with isoflurane for 30 min before receiving medetomidine (0.04 mg/kg, i.m.). Sedation produced by medetomidine-ketamine was unpredictable and of short duration. Both medetomidine-butorphanol-ketamine (MBK) and medetomidine-butorphanol-midazolam (MBMz) provided adequate anesthesia for routine physical exams; however, the effects of MBMz lasted longer than those of MBK. Heart rates and respiratory rates were within clinically normal ranges for all groups, and lemurs remained normotensive throughout the study. Common side effects such as hypertension and bradycardia associated with the use of alpha2-adrenergic receptor agonist combinations in other species were not observed. Likewise, medetomidine administration had no effect on HR in lemurs receiving isoflurane. Lemurs in all groups were well ventilated and remained well oxygenated throughout the procedures, though arterial partial pressure of O2 was lowest in the MBMz group. All three injectable medetomidine combinations were effective in ring-tailed lemurs but only MBK and MBMz provided adequate depth and duration of anesthesia for use as sole regimes. For many clinical procedures in lemurs, MBMz offers advantages over MBK because of its longer duration of action and its rapid and more complete reversibility with specific antagonists.     

Evaluation of medetomidine, ketamine and buprenorphine for neutering feral cats

A combination of medetomidine (M, 100 μg/kg), ketamine (K, 10 mg/kg) and buprenorphine (B, 10 μg/kg), administered by intramuscular injection, was evaluated for spaying and castration (neutering) of feral cats (n = 101). Eleven animals (11%) required supplemental anesthesia (isoflurane by mask) to maintain an adequate plane of surgical anesthesia. Atipamezole (A, 125 μg/kg) was administered subcutaneously at the completion of surgery. All cats recovered from surgery and were released the following day. A hemoglobin saturation (SpO(2)) value of < 95% was recorded at least once during anesthesia in all cats. This MKB combination can be used in a feral cat sterilization clinic, but isoflurane supplementation may be necessary. Further research is indicated to determine the clinical significance of the low SpO(2) values associated with this anesthetic regimen.     

Medetomidine-ketamine-butorphanol anesthetic combinations in binturongs (Arctictis binturong).

The efficacy, safety, and reliability of two ketamine-medetomidine-butorphanol anesthetic combinations were evaluated in 34 adult binturongs (Arctictis binturong). The animals were randomly assigned to one of the two groups. On the basis of estimated body weights, group high ketamine (HK) received ketamine (8 mg/kg, i.m.), medetomidine (0.02 mg/kg, i.m.), and butorphanol (0.2 mg/kg, i.m.) combined in a single injection, and group low ketamine (LK) received ketamine (2 mg/kg, i.m.), medetomidine (0.04 mg/kg, i.m.), and butorphanol (0.2 mg/kg, i.m.). Cardiopulmonary parameters were measured for approximately 45 min; the animals were then administered atipamezole (5 mg/mg medetomidine, i.m.). Individual responses varied greatly to the anesthetic combinations, but similar numbers of animals in each group needed supplemental anesthetic agents (seven in group HK and six in group LK). Mean heart rates were higher in the LK group throughout anesthesia. Animals in both groups were mildly to moderately hypoxemic, but oxygenation improved in both groups following supplemental oxygen administration. Respiratory rates, arterial blood pressures, body temperatures, and end-tidal CO2 values were similar in both groups. Both protocols were effective; however, the LK combination is preferable because the mean recovery time was shorter.     

Field anesthesia of wild arctic fox (Alopex lagopus) cubs in the Swedish lapland using medetomidine-ketamine-atipamezole.

A safe and effective anesthetic regime for use in arctic fox (Alopex lagopus) cubs was developed. During July 1996, six free-ranging 6-8-wk-old cubs were captured near their den in Vindelfjallen Nature Reserve, Sweden. Medetomidine and ketamine HCI, followed by atipamezole, were selected for the anesthetic trial because of the well-documented safety and efficacy of this drug combination in a broad range of species. The dosage regimen used was 50 microg/kg medetomidine combined with 2.5 mg/kg ketamine followed by reversal with 250 microg/kg atipamezole. Induction was rapid, with a mean induction time of 1 min and 32 sec (range: 58-150 sec). The cubs were anesthetized for a mean time of 18 +/- 5 min (range: 13-25 min). Serially recorded heart rate, respiratory rate, temperature, and pulse oximetry were stable throughout the anesthetic period for all cubs. Anesthetic depth was suitable for safe handling and minor clinical procedures, including venipuncture. Following atipamezole, all cubs were standing within 12 +/- 7 min (range: 5-24 min) and fully recovered at 27 +/- 5 min (range: 19-36 min). This information will be useful for future captive breeding and management programs involving the endangered arctic fox.     

Anesthetic effects of ketamine or isoflurane induction prior to isoflurane anesthesia in medetomidine-premedicated dogs

Dogs were given medetomidine (10 microg/kg body weight, intramuscularly) followed in 10 minutes by either ketamine (4 mg/kg body weight, intravenously) or isoflurane mask induction and maintained on isoflurane for 30 minutes. Medetomidine induced lateral recumbency in all dogs. Endotracheal intubation was faster and smoother when dogs were given ketamine than when induced with isoflurane. Analgesia was excellent in all groups. Respiratory depression was more profound when dogs were given ketamine. Recovery quality was smooth and similar among all groups. Medetomidine-premedicated dogs could be induced with either ketamine or isoflurane and maintained on 1.3% isoflurane to achieve good analgesia with smooth recovery from anesthesia.     

Anesthetic and cardiopulmonary effects of total intravenous anesthesia using a midazolam, ketamine and medetomidine drug combination in horses

The anesthetic and cardiopulmonary effects of midazolam, ketamine and medetomidine for total intravenous anesthesia (MKM-TIVA) were evaluated in 14 horses. Horses were administered medetomidine 5 microg/kg intravenously as pre-anesthetic medication and anesthetized with an intravenous injection of ketamine 2.5 mg/kg and midazolam 0.04 mg/kg followed by the infusion of MKM-drug combination (midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.1 mg/ml). Nine stallions (3 thoroughbred and 6 draft horses) were castrated during infusion of MKM-drug combination. The average duration of anesthesia was 38 +/- 8 min and infusion rate of MKM-drug combination was 0.091 +/- 0.021 ml/kg/hr. Time to standing after discontinuing MKM-TIVA was 33 +/- 13 min. The quality of recovery from anesthesia was satisfactory in 3 horses and good in 6 horses. An additional 5 healthy thoroughbred horses were anesthetized with MKM- TIVA in order to assess cardiopulmonary effects. These 5 horses were anesthetized for 60 min and administered MKM-drug combination at 0.1 ml/kg/hr. Cardiac output and cardiac index decreased to 70-80%, stroke volume increased to 110% and systemic vascular resistance increased to 130% of baseline value. The partial pressure of arterial blood carbon dioxide was maintained at approximately 50 mmHg while the arterial partial pressure of oxygen pressure decreased to 50-60 mmHg. MKM-TIVA provides clinically acceptable general anesthesia with mild cardiopulmonary depression in horses. Inspired air should be supplemented with oxygen to prevent hypoxemia during MKM-TIVA.     

Evaluation of total intravenous anesthesia with propofol or ketamine-medetomidine-propofol combination in horses

Objective-To compare the anesthetic and cardiorespiratory effects of total IV anesthesia with propofol (P-TIVA) or a ketamine-medetomidine-propofol combination (KMP-TIVA) in horses. Design-Randomized experimental trial. Animals-12 horses. Procedure-Horses received medetomidine (0.005 mg/kg [0.002 mg/lb], IV). Anesthesia was induced with midazolam (0.04 mg/kg [0.018 mg/lb], IV) and ketamine (2.5 mg/kg [1.14 mg/lb], IV). All horses received a loading dose of propofol (0.5 mg/kg [0.23 mg/lb], IV), and 6 horses underwent P-TIVA (propofol infusion). Six horses underwent KMP-TIVA (ketamine [1 mg/kg/h {0.45 mg/lb/h}] and medetomidine [0.00125 mg/kg/h {0.0006 mg/lb/h}] infusion; the rate of propofol infusion was adjusted to maintain anesthesia). Arterial blood pressure and heart rate were monitored. Qualities of anesthetic induction, transition to TIVA, and maintenance of and recovery from anesthesia were evaluated. Results-Administration of KMP IV provided satisfactory anesthesia in horses. Compared with the P-TIVA group, the propofol infusion rate was significantly less in horses undergoing KMP-TIVA (0.14 +/- 0.02 mg/kg/min [0.064 +/- 0.009 mg/lb/min] vs 0.22 +/- 0.03 mg/kg/min [0.1 +/- 0.014 mg/lb/min]). In the KMP-TIVA and P-TIVA groups, anesthesia time was 115 +/- 17 minutes and 112 +/- 11 minutes, respectively, and heart rate and arterial blood pressure were maintained within acceptable limits. There was no significant difference in time to standing after cessation of anesthesia between groups. Recovery from KMP-TIVA and P-TIVA was considered good and satisfactory, respectively. Conclusions and Clinical Relevance-In horses, KMP-TIVA and P-TIVA provided clinically useful anesthesia; the ketamine-medetomidine infusion provided a sparing effect on propofol requirement for maintaining anesthesia.     

Effect of medetomidine administration on bispectral index measurements in dogs during anesthesia with isoflurane

OBJECTIVE: To determine the relationship between bispectral index (BIS) and minimum alveolar concentration (MAC) multiples of isoflurane after IM injection of medetomidine or saline (0.9% NaCl) solution in anesthetized dogs. ANIMALS: 6 dogs. PROCEDURE: Each dog was anesthetized 3 times with isoflurane. First, the MAC of isoflurane for each dog was determined by use of the tail clamp method. Second, anesthetized dogs were randomly assigned to receive an IM injection of medetomidine (8 microg x kg(-1)) or an equal volume of isotonic saline (0.9% NaCl) solution 30 minutes prior to beginning BIS measurements. Last, anesthetized dogs received the remaining treatment (medetomidine or isotonic saline solution). Dogs were anesthetized at each of 4 MAC multiples of isoflurane. Ventilation was controlled and atracurium (0.2 mg/kg followed by 6 microg/kg/min as a continuous infusion, IV) administered. After a 20-minute equilibration period at each MAC multiple of isoflurane, BIS data were collected for 5 minutes and median values of BIS calculated. RESULTS: BIS significantly decreased with increasing MAC multiples of isoflurane over the range of 0.8 to 2.0 MAC. Mean (+/- SD) MAC of isoflurane was 1.3 +/- 0.2%. During isoflurane-saline anesthesia, mean BIS measurements at 0.8, 1.0, 1.5, and 2.0 MAC were 65 +/- 8, 60 +/- 7 52 +/- 3, and 31 +/- 28, respectively. During isoflurane-medetomidine anesthesia, mean BIS measurements at 0.8, 1.0, 1.5, and 2.0 MAC were 77 +/- 4, 53 +/- 7, 31 +/- 24, and 9 +/- 20, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: BIS monitoring in dogs anesthetized with isoflurane has a predictive value in regard to degree of CNS depression. During isoflurane anesthesia, our results support a MAC-reducing effect of medetomidine.     

Intramuscular anesthesia of bonito and Pacific mackerel with ketamine and medetomidine and reversal of anesthesia with atipamezole

OBJECTIVE: To determine anesthetic effects of ketamine and medetomidine in bonitos and mackerels and whether anesthesia could be reversed with atipamezole. DESIGN: Clinical trial. ANIMALS: 43 bonitos (Sarda chiliensis) and 47 Pacific mackerels (Scomber japonica). PROCEDURE: 28 bonitos were given doses of ketamine ranging from 1 to 8 mg/kg (0.5 to 3.6 mg/lb), i.m., and doses of medetomidine ranging from 0.2 to 1.6 mg/kg (0.1 to 0.7 mg/lb), i.m. (ratio of ketamine to medetomidine, 2.5:1 to 20:1). Doses of atipamezole equal to 1 or 5 times the dose of medetomidine were used. The remaining 15 bonitos were used to determine the anesthetic effects of ketamine at a dose of 4 mg/kg (1.8 mg/lb) and medetomidine at a dose of 0.4 mg/kg (0.2 mg/lb). The mackerels were given ketamine at doses ranging from 11 to 533 mg/kg (5 to 242 mg/lb) and medetomidine at doses ranging from 0.3 to 9.1 mg/kg (0.1 to 4.1 mg/lb; ratio of ketamine to medetomidine, 3:1 to 800:1). Doses of atipamezole equal to 5 times the dose of medetomidine were used. RESULTS: I.m. administration of ketamine at a dose of 4 mg/kg and medetomidine at a dose of 0.4 mg/kg in bonitos and ketamine at a dose of 53 to 228 mg/kg (24 to 104 mg/lb) and medetomidine at a dose of 0.6 to 4.2 mg/kg (0.3 to 1.9 mg/lb) in mackerels was safe and effective. For both species, administration of atipamezole at a dose 5 times the dose of medetomidine reversed the anesthetic effects. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that a combination of ketamine and medetomidine can safely be used for anesthesia of bonitos and mackerels and that anesthetic effects can be reversed with atipamezole.     

Dexmedetomidine or medetomidine premedication before propofol-desflurane anaesthesia in dogs

The objective of this study was to evaluate dexmedetomidine as a premedicant in dogs prior to propofol-desflurane anaesthesia, and to compare it with medetomidine. Six healthy dogs were anaesthetized. Each dog received intravenously (i.v.) five preanaesthetic protocols: D1 (dexmedetomidine, 1 microg/kg, i.v.), D2 (dexmedetomidine, 2 microg/kg, i.v.), M1 (medetomidine, 1 microg/kg, i.v.), M2 (medetomidine, 2 microg/kg, i.v.), or M4 (medetomidine, 4 microg/kg, i.v.). Anaesthesia was induced with propofol (2.3-3.3 mg/kg) and maintained with desflurane. The following variables were studied: heart rate (HR), mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate (RR), arterial oxygen saturation, end-tidal CO2, end-tidal concentration of desflurane (EtDES) required for maintenance of anaesthesia and tidal volume. Arterial blood pH (pHa) and arterial blood gas tensions (PaO2, PaCO2) were measured during anaesthesia. Time to extubation, time to sternal recumbency and time to standing were also recorded. HR and RR decreased significantly during sedation in all protocols. Cardiorespiratory variables during anaesthesia were statistically similar for all protocols. EtDES was significantly different between D1 (8.1%) and D2 (7.5%), and between all doses of medetomidine. Desflurane requirements were similar for D1 and M2, and for D2 and M4 protocols. No statistical differences were observed in recovery times. The combination of dexmedetomidine, propofol and desflurane appears to be effective for induction and maintenance of general anaesthesia in healthy dogs.     

Prolonging dissociative anaesthesia in horses with a repeated bolus injection

The effects of prolonging romifidine/ketamine anaesthesia in horses with a second injection of ketamine alone or both romifidine/ketamine compared with only induction injection of romifidine and tiletamine/zolazepam were studied in 6 horses anaesthetised in lateral recumbency on 3 random occasions. All horses were sedated with romifidine 0.1 mg/kg bwt iv and, on 2 occasions, anaesthesia was induced by iv injection of ketamine 2.2 mg/kg bwt. To prolong the ketamine-induced anaesthesia, either ketamine (I.1 mg/kg bwt iv) or ketamine and romifidine (I.1 mg/kg bwt and 0.04 mg/kg bwt iv, respectively) were given 18–20 min after the start of the ketamine injection for induction. On the third occasion, anaesthesia was induced by iv injection of 1.4 mg/kg bwt Zoletil (0.7 mg/kg bwt tiletamhe + 0.7 mg/kg bwt zolazepam). No statistically significant differences in the measured cardiorespiratory function were found between the 3 groups. Heart rate was decreased significantly after sedation but increased during anaesthesia. Arterial blood pressure increased after sedation and remained high during anaesthesia. A significant decrease in arterial oxygen tension was observed in all groups during anaesthesia. The muscle relaxation induced by romifidine was, in most cases, not sufficient to abolish the catalepsy following a repeated injection of ketamine alone. Zoletil or a repeated injection of ketaminehornifidine resulted in smoother anaesthesia. When additional time is required to complete surgery during field anaesthesia, it is advisable to prolong romifidine/ketamine anaesthesia with an injection of both romifidine and ketamine in healthy horses. When a longer procedure is anticipated from the start Zoletil is an alternative for induction of anaesthesia. The mean time to response to noxious stimuli and mean time spent in lateral recumbency was 28 and 38 min for the anaesthesia prolonged with ketamine, 3.5 and 43 rnin for the anaesthesia prolonged with ketaminehornifidine and 33 and 45 min for the anaesthesia with Zoletil. All horses reached a standing position at the first attempt.     

Bovine Chlamydophila spp. infection: Do we underestimate the impact on fertility?

The efficacy of ketamine and bupivacaine in enhancing the epidural analgesia induced by medetomidine was evaluated in 10 buffalo calves utilized repeatedly after a gap of 10 days so that each drug combination was tested in 4 randomly selected animals. In group A, medetomidine (15 microg/kg), in group B ketamine (2.0 mg/kg), in group C bupivacaine (0.125 mg/kg), in group D medetomidine and ketamine (15 microg/kg and 2.0 mg/kg), and in group E medetomidine and bupivacaine (15 microg/kg and 0.125 mg/kg) was administered epidurally. Onset of analgesia was significantly earlier in animals of groups B and D compared to the animals of groups A, C and E. Medetomidine alone or in combination with ketamine/bupivacaine produced complete analgesia of the tail, perineum, inguinal region and upper parts of hind limbs. Ketamine produced a very short duration of complete analgesia at the tail and perineum. Bupivacaine alone produced only mild to moderate analgesia. Both ketamine and bupivacaine prolonged the duration of analgesia. Motor incoordination was mild to moderate in animals of all the groups, but animals remained standing throughout the period of observation. Animals of groups A, D and E showed mild to moderate sedation during the observation period. Ruminal movements decreased nonsignificantly in animals of groups A and E. Mild salivation was observed in animals of all the groups except group C. Significant decrease in heart rate (HR) was recorded after epidural administration of medetomidine or bupivacaine; however, ketamine caused short duration of tachycardia. The administration of ketamine with medetomidine caused lesser decrease in HR compared to medetomidine alone or in combination with bupivacaine. Significant fall in respiratory rate (RR) was recorded after epidural administration of medetomidine or bupivacaine alone, but an increase in RR was recorded after ketamine administration. The fall in RR was less pronounced in animals in which medetomidine was used with ketamine compared to the animals in which medetomidine was used alone or in combination with bupivacaine. Mean arterial pressure (MAP) decreased and central venous pressure (CVP) increased significantly after epidural administration of medetomidine in combination with ketamine or bupivacaine. The ECG changes included tall T wave, QS pattern, RS pattern and ST elevation and heart blocks at different intervals, which were more frequent and pronounced in animals given bupivacaine with medetomidine. It can be concluded that epidural administration of medetomidine can produce complete analgesia of the tail, perineum, inguinal region and upper hind limbs in buffaloes. However, significant depression of cardiovascular parameters was recorded. Administration of ketamine along with medetomidine resulted in significantly early onset and slightly longer duration of analgesia with lesser cardiopulmonary side-effects compared to medetomidine alone or medetomidine with bupivacaine. Addition of ketamine to medetomidine thus seems to be useful for producing epidural analgesia; however, addition of bupivacaine failed to provide any advantage over medetomidine alone.