Why preoperative assessment is important?
Veterinary patients presented for surgical procedures must have a preoperative medical assessment before being taken to surgery. This complete presurgical evaluation of surgical patients is not only for their presenting complaints and diseases or injuries, but also for their suitability as candidates for anesthesia and the proposed surgical procedure. It indicates whether further care is necessary in the perioperative period, underscoring the importance of identifying hidden issues before anesthesia to reduce surgical risk and support a safer, smoother procedure and faster recovery. It helps select the best procedure for the patient. It supports prognostication, giving clients realistic expectations for the outcome of the proposed surgical intervention after a thorough evaluation focused on the pet’s safety. It could highlight other aspects of a patient’s health that may need attention and future management, helping protect the pet’s health and overall well-being. It also allows a comparison of the patient’s status before and after surgery, by establishing a baseline for tracking changes over time.
What are the elements of a preoperative assessment?
Preoperative assessment of surgical patients consists of a variety of elements. These are as follows:
Medical History
This is an often underrated but important part of the presurgical assessment of surgical patients. A complete medical history is essential to assess overall health before anesthesia and surgery. To extract the maximum benefit, the medical history must be complete. A complete history can be organized in the following manner for ease of remembrance: signalment (which also incudes the patient’s age, which helps tailor the evaluation to the pet’s unique profile), chief/presenting complaint, history of present illness, history of past illnesses (e.g., medical, surgical, vaccinations, medications), family history (if known), environmental history, diet history and body systems review. This should be obtained from the owner or primary care giver. In an emergency, an abbreviated history is often necessary to allow emergency care to be given but does not preclude obtaining a complete history as soon as the patient is stabilized.
Physical Examination for Pet's Health
Despite a natural inclination to concentrate on the presenting problem, the veterinarian should focus the physical examination, or physical exam, on assessing the whole pet, not just the presenting problem. Vital parameters and a general patient assessment, including mental status, body condition, and pain scores, are a vital part of the preoperative assessment and should be recorded. Indeed, as with medical history, a systematic approach ensures that all body systems are evaluated.
Various formats have been described for performing a thorough physical examination. A physical examination should include a head-to-tail visual inspection as part of the process. One format divides the evaluation process into examinations of the head and neck (eyes, ears, nose, and throat), forequarters, thorax, abdomen, and hindquarters. Another format emphasizes a body-system approach, with the examination divided into the cardiovascular, respiratory, alimentary, urogenital, lymphatic, endocrine, integumentary, musculoskeletal, and neurologic systems. Note that a rectal examination is a valuable aspect of the examination and should always be performed. Whichever system is used, it is imperative for each clinician to establish his or her own pattern so it becomes routine; haphazard examination will always be deficient in some category, whereas a systematic physical examination can uncover hidden conditions, such as infection, that may affect surgery.
Physical Status
Of the procedures available for preoperative assessment, the history and physical examination described previously are most effective in detecting important abnormalities. Problems missed at this stage are usually overlooked when more invasive or expensive diagnostic tests are performed during the preoperative assessment. They also enable assigning a physical status to each patient, as listed in Table 1, which helps jugde a pet’s overall health before surgery.
Physical status is a major determinant but is not a direct predictor of anesthetic or surgical risk. Rather, the primary purpose of assessing physical status is to compare patients and select tests to guide adjustments that can help minimize complications and reduce risk in pets that appear healthy, as well as in those already considered higher risk. It helps select the most appropriate anesthetic protocol and determine whether a patient’s status can be improved by postponing surgery in elective cases. In emergencies in which a patient’s status mandates an abbreviated examination, the physical status is qualified with an “E.” To clarify, an emergency is defined as existing when a delay in treatment would markedly increase the threat to the patient’s life or body part. In such circumstances, only data for immediate initiation of treatment are collected, and the examination is then completed after the animal is stabilized.
Table 1: Physical status in surgical patients
| Physical Status | Animal Condition | Examples |
|---|---|---|
| I | Healthy with no discernible disease. | Patient came for elective procedure (e.g., ovariohysterectomy, castration) |
| II | Healthy with localized disease or mild systemic disease that may or may not be related to the reason for surgery. | Obese but otherwise healthy patients, Neonate or Geriatric, cruciate ligament rupture, skin lump removal, controlled diabetes mellitus, mild cardiac valve insufficiency |
| III | Severe systemic disease that may or may not be related to the reason for surgery. | Pneumonia, fever, dehydration, heart murmur, anemia |
| IV | Severe systemic disease that is life threatening with or without surgery. | Heart failure, renal failure, severe hypovolemia, severe hemorrhage, sepsis, organ failure, high fever, pulmonary disease, emaciation |
| V | Moribund patient that is not expected to survive without the procedure | Severe trauma or disease that cannot be managed or mitigated prior to anesthesia and surgical procedure, Shock from ongoing severe hemorrhage, multiple organ failure |
Laboratory Data
Once a patient has been clinically evaluated, clinical problems identified, and a physical status assigned, laboratory tests can be selected for further preoperative assessment, with blood work serving as a critical part of pre-surgical testing to assess overall health before anesthesia. Routine testing commonly includes a complete blood count and a serum biochemistry profile. A complete blood count is a simple test of blood cells, including red blood cells, white blood cells, and platelets. Serum biochemistry and urinalysis provide information about organ function, including the liver, kidneys, and the urinary system, and can reveal metabolic disease before anesthesia.
The chosen tests should be the minimum necessary to evaluate the presenting problem and its systemic manifestations and determine the significance of concurrent disease conditions detected during the initial examination. Test information supports safer planning and may also highlight issues that could affect wound healing. Minimum recommendations for laboratory testing, based on a patient’s physical status, expected duration of surgery, and the invasiveness of the planned procedure, are listed in Table 2.
Table 2: Minimum recommendations for laboratory testing.
| Physical Status | Minor Procedure (Duration <60 minutes) | Major Procedure (Duration >60 minutes or patients >7 years) |
|---|---|---|
| I | PCV, total protein, urine specific gravity. | Complete Blood Cell Count, Urinalysis, Surgical Panel (BUN, Creatinine, Alanine Aminotransferase, Alkaline Phosphatase). |
| II | PCV, total protein, urine specific gravity. | Complete Blood Cell Count, Urinalysis, Surgical Panel (BUN, Creatinine, Alanine Aminotransferase, Alkaline Phosphatase). |
| III | Complete Blood Cell Count, Urinalysis, Surgical Panel (BUN, Creatinine, Alanine Aminotransferase, Alkaline Phosphatase). | Complete Blood Cell Count, Full Biochemical Panel, Electrolyte Panel, Urinalysis |
| IV and V | Complete Blood Cell Count, Full Biochemical Panel, Electrolyte Panel, Urinalysis | Complete Blood Cell Count, Full Biochemical Panel, Electrolyte Panel, Urinalysis |
Other Diagnostic Tests
These tests can further characterize and investigate abnormalities detected during the preoperative assessment of a surgical patient. Some of these tests also can help when planning surgical procedures. (When such investigations are considered essential, but facilities do not exist, consider referring the patient.) Such tests will include some of the following:
- Coagulation studies
- Acid-base and electrolyte tests
- Organ function tests
- Hormone assays, including thyroid testing prior to surgery
- Plain and contrast radiography
- Electrocardiography (EKGs) to identify arrhythmias or other abnormaliteis that may affect anesthesia safety
- Ultrasonography
- Magnetic resonance imaging
- Computed tomography
- Scintigraphy.
Thyroid testing may be recommended in dogs and cats for different reasons, including suspected hypothyroidism in dogs and hyperthyroidism in cats, as thyroid function can affect anesthesia and recovery. Disease-specific screening may also include heartworm tests for dogs and FIV/FeLV tests for cats before surgery.
Radiography and ultrasonography may also be used to evaluate internal tumors or organ abnormalities when planning surgery.
Echocardiography can be used to provide detailed images of the hear’s structure and function, helping to identify cardica conditions that could affect surgical risk.
The essential factor in selecting tests to evaluate surgical patients is a sound understanding of the disease, its systemic effects, and the planned procedure, underscoring the importance of choosing diagnostics accordingly.
Determination of Surgical Risk
Most people know that surgical risk is a concept that weighs the relative benefits of surgery against the potential for harm. However, a much broader definition also considers the surgeon’s experience, procedure’s invasiveness, the potential for complications, and quality of the patient’s life, both with and without the recommended procedure. The overall risk is assigned once the patient has been thoroughly evaluated, and this is used in decisions about when, where, and how to proceed with surgery and other treatment plans. Occasionally, the risk of the surgical procedure may outweigh its potential benefit.
Surgical risk can determine prognosis as follows :
- Excellent: Little effect on the patient, there is minimal potential for complications, and a high probability the patient will return to normal after surgery.
- Good: High probability of a successful outcome, but the potential for complications resulting from the procedure is slightly higher than the previous category.
- Fair: One or more severe problems detected or serious complications are possible but uncommon; recovery may be prolonged, or the animal may or may not return to its presurgical function.
- Guarded: The outcome is uncertain.
- Poor: The underlying disease or surgical procedure is associated with many or severe complications; there is a significant chance of major complications, with permanent changes in general health; recovery is expected to be prolonged, and the likelihood of death during or after the procedure is high; surgery is undertaken only if a higher risk is expected if surgery is not performed (i.e., surgery is necessary to preserve life).
Client Communication
The purpose of the preoperative assessment is to enable pet owners and the surgeon to make informed decisions and recognize potential complications in the patient’s care. A thorough patient evaluation will facilitate discussions related to:
- The disease
- Its course and prognosis both with and without treatment
- Options for treatment
- Recommended procedures
- Potential complications
- Aftercare
- An estimate of the immediate and follow-up costs.
The veterinarian should discuss pre-surgical preparation instructions, including that no food should be given for 8–12 hours before surgery unless told otherwise. Water may be allowed until a few hours before surgery, depending on instructions. Pet owners should keep their beloved pet calm to reduce stress and bring the pet safely in a secure carrier or on a leash.
Understanding preoperative assessment of pets before surgery is not only good for the surgeon-client relationship but also enhances clients’ compliance with aftercare recommendations.
