Comparison of the anaesthesia combinations racemic-ketamine/medetomidine and S-Ketamine/medetomidine in syrian golden hamsters (mesocricetus auratus)

S-ketamine and intranasal application: alternatives for the castration of male suckling piglets?

Background

The intramuscular injection of ketamine and azaperone was proposed as a suitable anaesthesia for male suckling piglets for surgical castration. However, this can be opposed by massive defensive movements, hypothermia and tachycardia during castration and a long recovery period. The aim of the present study was to test whether the use of S-ketamine and/or a change in the route of application from intramuscular to intranasal could reduce stress responses and the duration of recovery compared to the intramuscular route and the use of racemic ketamine. Seventy-eight healthy, five-day-old male piglets were randomized to six treatment groups in a blinded experimental study, matched by litter and weight. Experimental groups were A (15 mg kg-1 S-ketamine + 2 mg kg-1 azaperone, i.m., surgical castration), B (15 mg kg-1 R/S-ketamine racemate + 2 mg kg-1 azaperone, i.m., surgical castration), C (30 mg kg-1 S-ketamine + 2 mg kg-1 azaperone, i.n., surgical castration), D (15 mg kg-1 R/S-ketamine racemate + 2 mg kg-1 azaperone, i.m.; not castrated), E (positive control group; no anesthesia, surgical castration) and F (negative control group; no anesthesia, not castrated).

Results

S-ketamine reduced the defensive movement score during castration to a similar extent to racemic ketamine when administered intramuscularly but not via the intranasal route. However, the effects of S-ketamine (both routes) on the increase in cortisol levels and decrease in body temperature were similar to those induced by racemic ketamine. A reduction of the long recovery time known for ketamine-azaperone anaesthesia could not be achieved with S-ketamine in the given dosage, regardless of the route of application. The intranasal administration of ketamine was difficult with the available formulation as the necessary amount exceeded the capacity of the nose cavity.

Conclusions

Neither the use of S-ketamine nor intranasal administration can be suitable alternatives for the anaesthesia of male suckling piglets for castration.

Comparison of pre-emptive butorphanol or metamizole with ketamine +medetomidine and s-ketamine + medetomidine anaesthesia in improving intraoperative analgesia in mice

In accordance with the 'refinement' component of the 3Rs, the primary aim of this study was to investigate and compare ketamine + medetomidine (KM) and s-ketamine + medetomidine (SKM) anaesthetic protocols in C57BL/6J mice (both sexes). We sought to determine whether s-ketamine could provide adequate surgical tolerance at a 50% dose relative to that of ketamine racemate and whether antagonism of medetomidine could be initiated 15 min earlier. The second aim was to investigate the potential improvement in analgesia for both anaesthetic protocols by adding butorphanol or metamizole. Analgesia was tested via the pedal withdrawal reaction (PWR) to a painful stimulus. During anaesthesia, respiratory frequency, pulse oximetry, body temperature and PWR were monitored. Among the 16 mice in each group, the PWR was lost in all the KM + metamizole (35:56 ± 6:07 min), KM + butorphanol (43:45 ± 2:14 min) and SKM + butorphanol (24:03 ± 5:50 min) mice, 15 of the non-premedicated KM (37:00 ± 8:11 min) mice, and 9 of the pure SKM (20:00 ± 4:19 min) mice; the latter group increased to 11 mice (17:16 ± 5:10 min) with premedication of metamizole. In contrast to the racemic combination, s-ketamine at the dose used here did not lead to sufficient loss of the PWR. However, earlier partial antagonism of SKM resulted in a slightly shorter and qualitatively better recovery than later partial antagonism of SKM. The addition of metamizole or butorphanol to KM or SKM anaesthesia positively influences the analgesic quality. However, when butorphanol is added, controlled ventilation may be necessary, especially for male mice.

Comparison of S(+)-ketamine and ketamine, with medetomidine, for field anaesthesia in the European brown hare (Lepus europaeus)

OBJECTIVE

To compare anaesthesia and recovery parameters of racemic ketamine or S(+)-ketamine in combination with medetomidine for intramuscular (IM) field anaesthesia in the European brown hare (EBH) (Lepus europaeus).

STUDY DESIGN

Randomized, prospective, blinded clinical trial.

ANIMALS

20 adult EBH (eight male, 12 female), mean ± SD weight 3360 341).

METHODS

Medetomidine (0.2 mg kg(-1) ) and ketamine (30 mg kg(-1) ) (K-M group) or S(+)-ketamine (15 mg kg(-1) ) (S-M group) were administered by IM injection. Time until first effect and loss of righting reflex were recorded. During sedation and anaesthesia heart rate, saturation of arterial haemoglobin, respiratory rate, side stream end tidal CO(2) (Pe'CO(2) ), non invasive blood pressure, body temperature, cardiorespiratory parameters, palpebral reflex, jaw tone and nociception were recorded every 5 minutes. Medetomidine was antagonized with IM atipamezole (1 mg kg(-1) ) 45 minutes after treatment injection. Time until first head lift, standing and total recovery time (T-Recov) were recorded. Incidences of falling and involuntary movements during recovery were counted. Recovery quality was scored by visual analogue scale. Descriptive statistics were used to visualize maintenance data. All other data were included in multiple linear regression models.

RESULTS

Surgical anesthesia was not produced reliably with either protocol. Hypoxaemia occurred in both groups (SpO(2) < 90%). During recovery, falling was noted significantly less often (p < 0.001) in the S-M group (13 ± 7) versus the K-M group (27 ± 13). T-Recov was long, lasting for more than 3 hours in individuals with no significant differences between groups.

CONCLUSION AND CLINICAL RELEVANCE

S(+)-ketamine showed only minor advantages over racemic ketamine. Surgical anaesthesia was not achieved reliably with either protocol. Oxygen supplementation should be considered to prevent hypoxaemia. Further research is needed to develop an injectable field protocol adequate for surgical procedures, but with a rapid smooth recovery.

Anaesthesia with Midazolam/Medetomidine/Fentanyl in Chinchillas (Chinchilla lanigera) Compared to Anaesthesia with Xylazine/Ketamine and Medetomidine/Ketamine

We studied four different drug regimes for anaesthetic management in chinchillas and evaluated and compared their cardiovascular and respiratory effects. In this randomized, cross-over experimental study, seven adult chinchillas, five females, two males [515 +/- 70 (SD) g] were randomly assigned to one of the following groups: group 1 [midazolam, medetomidine and fentanyl (MMF), flumazenil, atipamezole and naloxone (FAN); MMF-FAN] received 1.0 mg/kg midazolam, 0.05 mg/kg medetomidine and 0.02 mg/kg fentanyl i.m., and for reversal 0.1 mg/kg flumazenil, 0.5 mg/kg atipamezole and 0.05 mg/kg naloxone s.c. after 45 min; group 2 (MMF) 1.0 mg/kg midazolam, 0.05 mg/kg medetomidine and 0.02 mg/kg fentanyl i.m.; group 3 [xylazine/ketamine (X/K)] 2.0 mg/kg xylazine and 40.0 mg/kg ketamine i.m.; and group 4 [medetomidine/ketamine (M/K)] 0.06 mg/kg medetomidine and 5.0 mg/kg ketamine i.m. Reflexes were judged to determine anaesthetic stages and planes. Anaesthesia with X/K and M/K was associated with a prolonged surgical tolerance and recovery period. By reversing MMF, recovery period was significantly shortened (5 +/- 1.3 min versus 40 +/- 10.3 min in MMF without FAN, 73 +/- 15.0 min in X/K, and 31 +/- 8.5 min in M/K). Without reversal, MMF produced anaesthesia lasting 109 +/- 16.3 min. All combinations decreased respiratory and heart rate but compared with X/K and M/K, respiratory and cardiovascular complications were less in the MMF groups. Focussing on the clinical relevance of the tested combinations, completely reversible anaesthesia showed two major advantages: anaesthesia can be antagonized in case of emergency and routinely shortens recovery. In small animals particularly these advantages lead to less complications and discomfort and thus often can be lifesaving. As all analgesic components (medetomidine and fentanyl) are reversed, postoperative analgesia should be provided before reversal of anaesthesia.