Back in December I talked about changes in anesthesia protocols, emphasizing how new research and technology allows us to evolve and adapt to make procedures safer. Yesterday I discussed one monitoring parameter, and unexpectedly started a bit of a debate on the usefulness of electrocardiograms (ECGs). Since I believe that open and honest debate is how we learn from each other, I thought that I'd clarify the things that I feel are essential to safe anesthetic events. Personally I don't think that general anesthesia should be performed without the following things, and I know that my views mirror those of anesthesia specialists.
Pre-Anesthesia Blood Tests
Just because a pet looks healthy on the outside doesn't mean that everything is normal. Low-grade anemia can be a sign of other problems and won't be obvious on a physical exam. Early liver and kidney disorders also can't be detected on an exam, but could be found with simple blood tests. If these tests aren't performed, there are many problems that can be missed and could lead to problems with the safety of anesthesia.
As much as we don't want them to, things can wrong during anesthesia. If this happens, the quickest way to put corrective drugs into the system is through the veins. When a pet is "crashing", seconds matter and you don't want to have to struggle to put in a catheter. If one is already in place you can have a better chance of saving a pet if anything adverse ever happens.
Intravenous fluids during surgery aren't about correcting dehydration. They are about maintaining blood pressure and circulation. When you anesthetize a pet it affects their cardiovascular system which can cause blood pressure to lower and can affect perfusion (how much blood ends up into tissues). When you have fluids entering the veins you can help keep pressure and circulation at appropriate levels.
Despite the debate after yesterday's entry, I feel that this is an important and essential part of monitoring. There are patterns on the ECG that can indicate problems with the function of the heart that you can't detect any other way. Simply put I feel that no anesthesia should be performed without this.
This piece of equipment measures the oxygen content of the blood. Obviously this is very important because even if you have adequate fluid volume and blood cells, if they aren't carrying oxygen through the body you could have a critical state. Low blood oxygen can lead to permanent tissue damage, including the brain. Honestly, though, this is the piece of equipment I would be willing to live without. I have had problems with pulse oximeters not reading properly even if the patient was otherwise normal. At the same time, if there is a documented decrease in blood oxygen, you need to intervene right away.
There are several ways to measure this and I'm not going to debate one method versus another. If blood pressure drops too much it can affect how much blood reaches tissues as well as how well the heart pumps. Conversely a case of hypertension can lead to a different set of problems, or even indicate an abnormality with the kidneys.
Monitoring equipment is great and can tell us things that our eyes, ears, and hands can't detect. But they can't replace a skilled technician watching the patient. No computer or electronic device can have better judgment than someone standing there keeping track of the patient's vitals. I have my staff record information from the above monitors every five minutes. But I also train them that this doesn't take the place of listening to the heart with a stethoscope, feeling the pulse with their fingers, and looking at the color of the gums. Equipment can fail, malfunction, or misread, so as important as the are, the SINGLE MOST important part of anesthesia monitoring is an actual person watching the patient.
My colleagues who read this entry will surely have their own strong opinions. I also deliberately have avoided getting too deep into the science of anesthesia monitoring since I don't want to write a textbook on the subject and I have many readers who aren't medical professionals. I want to present this subject in a way that everyone can understand the discussion.
The important take-home message is that anesthesia is a very serious procedure with lots of potential for things going wrong and leading to death. The best way to avoid problems is to be watching the patient's vital signs in several different ways so that if an abnormality is noted something can be done quickly to correct the problem.