Preanesthetic evaluation (Proceedings)
Allen Lakein said "planning is bringing the future into the present so that you can do something about it now". In preparation for an anesthetic procedure, we must know our patients well in order to be successful. We evaluate each patient individually to determine what drugs, dosages, as well as administration routes performed. Developing a plan also helps us anticipate what techniques we need to use and what type of monitoring tools are required to be safe. Knowing the procedure performed on each patient as well as our drug protocol will keep us alerted to anticipated complications such as hypotension, hypothermia, hypoventilation, arrhythmias, etc.
SignalmentThe patient's signalment, which includes the owner's information as well as species, breed, sex and age, will help influence our decisions. The client information, especially emergency phone numbers are helpful in the case of emergency contact. Various species have different metabolic requirements as well as special considerations for each individual species. A cat can develop laryngospasm during intubation. This rarely occurs in the dog. Certain breeds have influencing factors such as the sight hounds group. They may have a lower serum protein, which will reduce your dose of protein binding drugs. They also have very little to no body fat and in sight hounds; there is an alteration of liver enzymes. These things will make the recovery period longer. It is advisable to avoid highly protein bound drugs such as thiobarbiturates. The sex of the animal is particularly important especially during pregnancy. If the patient is a neonate or pediatric, they may have immature liver function as it is not well developed. If the patient is geriatric, one should consider compromised organ function even if not recognizable through neither physical exam nor diagnostic exams. We can not always see aged organs. Brachycephalics often have upper airway obstructive disease. Boxers have been seen to be sensitive to Acepromazine. People call this "boxer-ace syndrome". It has not been documented but there is an increased risk of bradycardia, which may be due to excessive vagal tone. Miniature Schnauzers have been seen developing sick sinus syndrome. They should be evaluated with an electrocardiogram prior to anesthesia. Doberman Pinschers can develop a coagulation disorder called von Willebrand's disease. It is ideal to have the von Willebrand's factor checked before surgery & or do a buccal mucosal bleeding time (normal is less than 3 minutes).
The behavior of the animal can impact your choice of drugs dramatically. A usual attempt to sedate an animal may turn into immobilization due to the fractious nature of the patient. A proper physical exam may be near to impossible until the animal is under the influence of drugs that induce sedative and or tranquillizing effects. A stressed animal will have a catecholamine surge. There will be an increase in heart rate & blood pressure, therefore more of a work load on the heart. This will alter the effects of anesthetic dugs.
History and Client Information
If there is indication of disease prior to anesthesia, the patient may require additional diagnostics.
If a cat has a history of drinking and urinating frequently, one should suspect renal disease. It may also be behavioral but this problem should be evaluated prior to anesthesia. A dog that has exercise intolerance can indicate cardiopulmonary problems or a dog that is painful. A cat that sneezes frequently can reveal upper respiratory disease and or a foreign body. Some owner's may communicate extensively, which can benefit you in developing your anesthetic plan. Current health may reveal that an old problem is now managed such as a diabetic patient that is now under control. It is important to tap into old problems as well as new. If it's a new problem, how long has it been going on and what is the severity? What are the symptoms of the patient? All of this information factors into your plan.