Right, so from what I've gathered, IV needles come in various gauges. If you're going to put a saline drip on someone (isn't that what patients are often given during and after surgery? If not, what is the clear liquid in the bag?), what gauge should you use and why? How do you know whether to go for 18 or 20, for instance? A couple of questions about anesthesia when a patient requires major brain surgery, gastrointestinal surgery (upper and lower GI), and amputation of an arm (including the shoulder) and both legs (including thighs): How long is it safe to keep a person under? For longer surgeries, is there a preference between inhalation and IV? If it's the IV option, is it one shot per every so and so many minutes / hours or do they use a constant, slower, well, drip or some such? Does the method of anesthesia (and its duration) differ if -it's one big, long process that takes hours upon hours from start to finish (do they ever change surgeons mid-surgery if it takes very long? Or would several surgeons work on the same patient at the same time to speed things up?) -the patient requires several surgeries done as soon as humanely possible to save their lives (is it common practice to allow the patient to wake up in the middle of the surgeries and recuperate a bit or do they just start the next one immediately after finishing the previous one?) What's the longest it's safe to keep a person under? I mean totally out, asleep. When do they opt for a medically induced coma? How safe / controllable is a barb coma? Are there other ways to pull it off besides barbs? And I'd also need to know how much carfentanil would it take to make a large grizzly (around 1100lbs) fall asleep / go unconscious (so it can be operated on)? How much saline should be used in the mix? Can it all fit in one dart syringe? In the scenario, carfentanil and saline are all the vet has at hand (a bit of an improv situation). How long would it be safe to keep the bear sedated? It seems carfentanil has a half-life of around 7,7hrs, but how soon would the bear start to wake up? Does the risk of complications like breathing problems rise the longer the animal is out? I know I'm asking for everything but the damn Moon from the sky but I'd really appreciate any input from those in the know Ball-park estimates are also ok if nobody knows the exact answers (thinking about the grizzly case since I don't know how many vets are here). ETA: Sorry, just one more question: why is it called a "peripheral" IV?
Let me take those questions a few at a time. An IV for OR is rarely just saline. Ringer's Lactate is more common as it adds a few more electrolytes. The size of the needle is not dependent on the fluid you are going to run as much as it's dependent on the size of line the surgeon or anesthesiologist wants in for an emergency. You might see a 20g for a quick, low risk surgery, most of the time you will see a 16g or 14g. The smallest needle blood cells can go through without hemolyzing the red cells is a 23g but if you need to infuse blood in a hurry you'd never use a needle that small. For any surgery that risks any significant blood loss you'd see 16g or larger.
Thanks for the info. So, what would you call the needle stuck in your hand when you wake up: is it a peripheral IV needle or a hypodermic needle or a peripheral venous catheter? Or something else entirely?
Some extensive surgeries can last 15-20 hours. For example separating conjoined twins that involves major organs can last that long. You could easily Google that for specifics related to the surgery you have in mind. I've not heard of waking a patient up to let them rest. You would stop the surgery if the patients blood pressure or oxygenation couldn't be maintained. And sometimes surgeries are done in parts because the procedure is so complex. You should look up general anesthesia to get your answers on the most common drugs used. Sometimes it's a combination of anesthetic gas and IV drugs. I'll let someone else answer the vet question. Peripheral refers to the limbs, the outer edges so to speak, just like the periphery of other things. IV's are either put in the limbs, aka a peripheral line; or into the larger chest veins, a central line.
Thanks a bunch, that answered a lot of my questions. A quick search didn't really yield any maximum time for general anesthesia, so apparently 20+ hours wouldn't be a problem if everything goes without complications. Also found the amount of carfentanil (and later naloxone) to be used, but I might have to pester an actual vet about the rest of the details...
It's more like "possible" than, "wouldn't be a problem." The longer one is under anesthesia the higher the rate of post op complications but it's difficult to sort out because a long surgery means a sicker patient as well. The "longest surgery" Wiki answer sounds plausible: But I see what you mean about not being easy to find.
Well, it depends on the fluid you anticipate using and clinical situation. If you have a patient who vomited blood, and they might crash at some point, you'll be putting in two large bore IV lines, 14 if you can get it in, or 16 gauge. It's so that you can infuse fluid or blood faster in a resuscitation situation. Most adults who aren't severely compromised and need Iv access for some slow infusion fluids, antibiotics and the like, do well with 18 gauge. 20 gauge is only used for very fine and frail veins that won't accept anything larger. Babies and small children obviously need even smaller gauge, but again, if you anticipate haemodynamic compromise, you try the biggest gauge you can get in. As far as fluids go, most common one is normal saline, but you also have dextrose solutions of varying concentrations, as well as hypertonic saline (although it's uses are very limited), Hartmann's (used a lot in surgery and obstetrics) and Ringer's. And then you have blood based products like blood and fresh frozen plasma, which have their uses in variety of situations where crystalloid solutions won't do the trick. In long surgeries, the staff indeed changes, usually people don't do more than 4 hours in a row, but there isn't a hard and fast rule, especially for surgeons, who sometimes stay upwards of seven hours. How long is safe to stay under? The shorter the better, and all surgeries that are expected to last longer than 4 hours are carefully planned, and if possible, are done in stages. Longer the surgery, higher the risk of complications. Anaesthetist carefully monitors the depth of anaesthesia throughout the procedure, and they can keep a person under for much longer than any surgery requires. They do top up the anaesthetic as they go. So anaesthesia isn't a limiting factor. Even though the drugs are different, people can be put in medically induced coma for up to a month, but only a few conditions benefit from that procedure, and it isn't done often. Can't help with a bear, you'd have to ask a vet
Thanks for the info, jazz, I'm starting to have a pretty good idea which gauges would be suitable in the context of the scene I'm working on as well as its timeline.
