Why do I need bloodwork before anesthesia and surgery?

So you’ve been told your pet needs surgery. For many, hearing those words brings on all kinds of emotions, fears and anxieties. Seems everyone knows someone who knows someone who has an unpleasant story to tell either human or veterinary, with regards to either anesthesia or the surgery itself. There are many kinds of surgery performed in veterinary medicine from the cosmetic bump removal to the most extensive of orthopedic reconstructions. Some veterinarians specialize in only certain surgeries, I.E. veterinary ophthalmologists and eye surgery. Others are limited to only soft tissue surgeries and yet others, only orthopedic surgery. But common to all is the need for anesthesia, a procedure by which our patients are rendered immobilized, unconscious, and free of pain and anxiety before, during, and after the procedure is performed.

Humans come in all sizes and shapes but the variability in size, body conformation, weight, and even species is far greater in the veterinary setting. To compound this even further there are species specific issues and even individual breed variabilities within a species that play a role in deciding what is the best and safest protocol for a given patient. In many instances, particularly the elderly or very sick, or severely injured patient, the anesthesia is the highest risk part of the overall surgical event. Unfortunately, we cannot always wait for the patient to get better to do their surgery as the surgery itself may be the only way to get better.

Every patient undergoing anesthesia at our hospital is given a physical exam prior to administering any anesthetic agents. This is on top of the exams that have been done in establishing the reason for surgery, either by our own doctors or the referring doctors. In addition to physical exams, preoperative bloodwork is routinely done. While the physical exam is very important, many things cannot be determined by the exam alone. Bloodwork is our means of assessing the internal functions of the animal and combined with exam, help us to choose the best, safest means of anesthesia that allows for the procedure to be completed. Like the scan tool used to diagnoses automotive problems, bloodwork can uncover issues before they are even noticed by the owner as an issue, Considering a liver could lose up to 80% of its functional ability before liver disease is seen or it may take up to up to 66-75% loss of kidney function before obvious urinary/kidney disease signs are reported, bloodwork becomes very important to the overall assessment of a patients overall health. Our goal is have the entire surgical experience be successful and this includes being able to wake up from the anesthesia and not suffer from some other disease process that the anesthesia was detrimental to. With all this said there are still some issues that exam and bloodwork are simply incapable of predicting. Allergic /hypersensitivity reactions, blood clots to name just a couple. While adverse reactions under anesthesia are uncommon, we do whatever we can to know the potential for one beforehand AND be prepared for the unknowns during. The placement of IV catheters and fluid administration during surgery is the norm to aid in maintenance of blood pressure, perfusion of vital organs with oxygen carrying blood, aid in elimination of anesthetic drugs afterwards and to provide a port for the immediate administration of emergency drugs should the need arise. In addition to all these measures, monitoring of the anesthetized patient by trained veterinary technicians and is carried out throughout the whole preoperative time.

Thankfully “problems” during anesthesia and surgery are rare thanks to the exams, tests, agents used and monitoring. But, when they do occur, being trained to recognize it early and prepared to respond to it can be the difference between a pet owner still having a successful outcome or having an unpleasant story of their own.