I am not surprised the oxytocin didn't work. As I said, I have never heard it working in snakes, and herp vets have told me that they don't use it for snakes. That seems like a lack of research on the part of your vet. However, since I am not a vet myself, I am giving him / her the benefit of the doubt, assuming that it has probably worked with snakes at one time or another.
I am going to post an email that Don Soderberg sent me about how he uses calcium to sometimes solve the problem (in reference to a particular person who asked about the subject). He gave me permission ( a long time ago) to pass the info on to other people, with the disclaimer that is he also not a vet, but it works for him. I have not used this technique myself, but maybe your vet could try it before surgery. Good luck!
Email from Don S. (5/20/07):
...Keep in mind that letting lubricant contact the egg will kill it. No matter how little you try to put on it, it will suffocate the embryo in the egg. If you're okay with that, go ahead. Actually, if you're pushing the egg slightly with your thumb while you're maneuvering the probe around the egg (be careful not to perforate the oviduct that is sheathing the egg), it will likely come out very quickly. Be careful. They can actually shoot out. Once you see the egg crowned to the half way point, greatly reduce the pressure you're applying with your thumb.
Calcium sandoz contains glubionate so while it may not help, it won't hurt to use it. A vet told me that calcium gluconate increases posterior muscle action. I have read that calcium glubionate has a similar affect. I know nothing about it having an egg softening stimulus and I don't see how any mineral could have an immediate effect on the composition of the eggs. I have read that it also helps control muscle spasms and contractions. In mammals, it is usually recommended in conjunction with one of the acid peptides like oxytocin. I have used oxytocin and calcium gluconate together, but with only 10-15% efficacy. I don't recommend using oxytocin, but my efficacy rate for using only the calcium glubionate is above 50%. I give the snake an intramuscular injection of 40 milligrams per kilogram of body weight. Some vet guides prescribe 10-50 mg/kg. I've had satisfactory success with 40 mg/kg. I administer it IM (intramuscular) to the dorso-lateral muscle group in the middle body area. NOTE: It seems to me that the prescribed dose may not be allowing for the extra body weight of the eggs. Therefore, I have always been nervous about using too much. I have never used the maximum recommended dose of 50 mg/kg, but have never had any complications with 40 mg/kg (with the possible exception of the spinal damage).
If you don't see results in four to six hours, I presume failure and move on to plan B.
Precautions/disclaimers:
I am NOT a vet. I am not giving you advice nor am I suggesting you do any of this. I merely conveyed my experiences with these medications.
If the obstacle that is precluding oviposition is not associated with muscles and/or the calcium does not result in sufficient muscle performance to move the egg, the snake could experience severe spinal trauma. I have one snake here that pushed so hard to lay the eggs that she damaged many of her vertebrae. It was l like a train wreck. The connective tissues around the vertebra were not strong enough to withstand the excessive pushing of the muscles and they were damaged. I've seen this many times, but this particular snake now that has a severe spinal deformity as a result of me administering calcium gluconate. It's possible it would have suffered the damage without the calcium injection, but I'm forced to consider my role in the damage.
Sorry I can't help you more. If you don't care about the egg, I believe that the manipulation that Kathy suggested is your best route. You're running out of time. Not to save the egg, but your snake is preparing to shed again and your window of opportunity to manipulate is shrinking. Honestly, I firmly believe that if you do nothing, the snake will pass the egg as soon as it sheds. If this were my snake, I would have fed it a medium adult mouse the day after she laid the other eggs. Then, when she sheds, her renewed strength from rest and the extra nutrition, along with digestive movement, will help move the egg out. I give you a 60-75% chance that the egg will pass naturally as soon as she sheds. If it doesn't, you can try Kathy's suggestion at that time. No matter what you do, I find that eggs that were retained for 48-72 hours after the first ones laid, die of suffocation in the oviduct. Therefore, if that amount of time has elapsed, it's probably a dead embryo anyway.
Good luck and write if you have more questions.
To Don, from me (5/20/07):
If you don’t mind, I will keep your email handy, and send part of it (as a quote by you) to people who ask about methods of removing eggs. Or I could put part of the quote (along with your disclaimer about not being a vet – I often use one like that too) as part of my FAQ on egg binding. If so, I can send you a copy when I eventually finish it to make sure that it represents you accurately.
To me, from Don (5/20/07):
No problem. I stick to all those as being factual and rely on those methods and meds annually in our ongoing battle against dystocia. Use that in any way you wish. My book goes into much more detail.
Hope this may help. You can always check with Don for more info or update, since this email is 2 years old.