Andreas Gaugler, [13 Nov 2023 at 20:49:48]: I darted a wild horse today for castration, using 4 mg etorphine, 8 mg medetomidine, 100 mg ketamine and 10 mg water-based perphenazine. During the operation, he shivered really a lot, but awoke very well with atipamezole + yohimbine and naltrexone. What do I change to reduce the severe shivering? Hendrik Hansen, [14 Nov 2023 at 06:56:48]: Andreas, I think lower the etorphine to 1 mg – the shivering is usually due to hypoxia. Andreas Gaugler, [14 Nov 2023 at 07:40:31]: Thanks Hendrik Andreas Gaugler, [14 Nov 2023 at 07:53:47]: Maybe I should also have included butorphanol in the mix but I will lower etorphine in future. Fortunately, the whole operation was fast enough to get horse up quickly. Leith Meyer, [14 Nov 2023 at 07:57:06]: There’s a bit more to tremors than just hypoxia, see our previous work on rhino. Our recent work is pointing us more towards the direct activation of the sympathetic nervous system by the potent opioids, which causes the release of adrenaline and noradrenaline resulting in tremors, particularly in Perissodactyla. Reducing etorphine may help, but so will butorphanol IV as it reduces the effects of etorphine. Adding oxygen after butorphanol is probably first prize. Bart Gazendam, [14 Nov 2023 at 07:57:56]: A question for those darting rhino (black or white) with high dosages medetomidine and a potent opioid in the dart combination: do you still administer butorphanol once recumbent? (Just wondering for thesis purposes, keeping in mind the synergism of alpha-2 agonists and opioids) Gary Bauer, [14 Nov 2023 at 08:01:23]: no Andreas Gaugler, [14 Nov 2023 at 08:35:14]: Thanks Leith, that makes sense and oxygen would help especially if you need to keep animal down longer. I probably should have included butorphanol. But as soon as I administered the atipamezole/yohimbine combination, the tremors subsided. Leith Meyer, [14 Nov 2023 at 08:51:09]: Interesting that the tremors subsided after the alpha-2 antagonists were given, as medetomidine usually causes muscle relaxation. Maybe the tremors were more related to severe hypoxaemia and when you antagonized medetomidine the improved pulmonary gas exchange corrected this severe hypoxaemia. Andreas Gaugler, [14 Nov 2023 at 10:56:16]: Unfortunately, I did not do O2 levels in this instance and that may well be the case. But the end of tremors was immediate. I appreciate everyone’s input Gernot Redeker, [14 Nov 2023 at 11:51:31]: For me, when I give butorphanol, the respiration goes up from 7-8 to 13-15 per minute. It makes a huge difference.... Pierre Nel, [14 Nov 2023 at 13:36:20]: Andreas, was there quite a time lapse between the alpha-2 antagonist (iv ?) and naltrexone? The opioid excitation seems to be much worse in domestic horses than about any other animal commonly immobilized. Andreas Gaugler, [14 Nov 2023 at 13:56:18]: Pierre both iv and more or less 1 min time between HO Reuter, [14 Nov 2023 at 19:38:10 (14 Nov 2023 at 19:56:38)]: I recently have given butorphanol at 15-20x opioid dose as well as atipamezole/yohimbine after they become recumbent or even before they go down. e.g. mature cow darted with 2mg Thianil, 10 mg medetomidine, 20 mg azaperone or 7.5mg Dormicum and 2500 IU Hyalase, as I get to them I gave 25 mg butorphanol, 4 mg atipamezole and 12.5 mg yohimbine, blindfolded and ears plugged. Some keep standing /walking, others get up to walk easily with just a little prodding once crates ready. Previously, I only gave reversal shortly before walking them and some needed extra dose and prodding to get them up. Hendrik Hansen, [15 Nov 2023 at 04:55:00]: Bart, mostly not - but you can use butorphanol at 40mg per mg potent opioid to partially antagonise the potent opioid and have the butorphanol taking up the primary opioid effect in the combination if needed for better parameters Leith, I found that higher potent opioid with constant alpha-2 agonists can give longer downtime than lower opioid to a reasonable point. Can this also be because of this activation of the sympathetic nervous system that is dose dependant? Henry Labuschagne, [15 Nov 2023 at 06:00:10]: Why not dart with BAM if the aim is to get butorphanol to take over the primary opioid effect? Leith Meyer, [15 Nov 2023 at 08:04:53]: Hendrik, I think the immobilizing (catatonic) effects of the potent opioids are independent of the sympathetic effects, but they are also dose dependent i.e. the higher the dose, the longer the immobilization. I’m assuming you have noticed these effects when you are doing long duration immobilizations for the OPUs? Pierre Nel, [15 Nov 2023 at 14:27:09]: Am I understanding correct, the shivering stopped in the minute between yohimbine/atipamezole & naltrexone? Still curious why alpha-2 reversal would stop shivering. Andreas Gaugler, [15 Nov 2023 at 15:10:09]: Correct Hendrik Hansen, [15 Nov 2023 at 22:07:53]: Exactly Henry. That is why I am using butorphanol + medetomidine in all rhino anaesthesia’s, but the problem remains the volume. Kyron just compounded a 100mg/ml butorphanol that is very handy to reduce the volume. Why would 3 mg Thianil + 3mg medetomidine then have a longer knockdown than 1 mg Thianil + 3 mg medetomidine in adult buffalo cows? Given that after 25 minutes, the 3 mg Thianil + 3 mg medetomidine cows are going into severe hypoxia and mostly need emergency treatment. I always thought it was due to the dose and level of sympathetic excitatory effect with the higher potent opioid. Leith Meyer, [16 Nov 2023 at 07:01:40]: Hi Hendrik. I’m not sure if I’m following you, but based on what you are saying with the higher Thianil dose, you would expect a longer immobilization as the catatonic effects of Thianil will be longer at a higher dose. You would also expect greater hypoxaemia, possibly both from greater respiratory depression, and worse pulmonary gas exchange which is most likely as a result of greater sympathetic effects from Thianil. As you know, gas exchange is pretty bad in ruminants receiving alpha-2 agonists, but likely made worse by the opioids. If the hypoxaemia is really severe over 25 mins, the animals likely will be in trouble and possibly less responsive, which could look like the immobilization is becoming deeper and lasting longer. One would really have to look at blood gases and other physiological measures to really understand why you are seeing these differences. I hope my musings help, but happy to chat about this further if you wish. https://www.jsava.co.za/index.php/jsava/article/download/567/512/3489 I’ve added this paper in case anyone is interested to see the interesting physiological effects and differences when different combinations and doses of Thianil, azaperone and medetomidine are used in blesbok.
