Why is a Pre-Operative Assessment Important?

Introduction

   You have decided it is time to consider surgery to find relief to your problems. Before going under the knife your surgeon may want to ensure if you are healthy enough to go through with the procedure. Most operations often require some form of general anesthesia and your body goes under stress. This stress may affect the function of vital organs that if not in top shape, may not withstand the whole procedure. To ensure the safety of patients, especially with elective operations, surgeons will often require patients to have some preliminary tests done to have an idea on how some vital organs are functioning depending on their current state of health. This is referred to as as pre-operative assessment. The main goal of this assessment is to identify patient co-morbidities that have the potential to become complications during the peri-operative and post-operative setting. Not all patients require pre-operative assessments. Ultimately, a pre-operative assessment will allow physicians to assess and reduce possible risks that may occur during surgery.

Who requires a pre-operative assessment?

  The American Society of Anesthesiologist (ASA) has developed a Physical Status Classification System (ASAPS) where patients are categorized according to their physiological status that can be helpful in predicting operative risk. The ASAPS is categorized as followed:

• ASA 1: Normal healthy patient, BMI less than 30, non-smoker with good exercise
  tolerance. (Absolute Mortality – 0.1%)
• ASA 2: Patient with mild systemic disease, no functional limitations and well-controlled disease. (Absolute Mortality – 0.2%)
• ASA 3: Patient with severe systemic disease, not life-threatening, with some functional limitation as a result of disease. (Absolute Mortality – 1.8%)
• ASA 4: Patient with severe systemic disease that is a constant threat to life, with
  functional limitation from severe, life-threatening disease. (Absolute Mortality – 7.8%)
• ASA 5: Moribund patient who is not expected to survive in the next 24 hours without the operation. (Absolute Mortality – 9.4%)

   Patients with an ASAPS classification of ASA 1 or ASA 2 – generally don’t require a pre-operative evaluation, but it is subject to discretion of the surgeon or primary care physician. For patients with ASAPS classification of ASA 3 and above, the surgeon will refer these patients for a pre-op medical consultation with their PCP.

The Pre-Operative Assessment 

  The pre-operative assessment entails three categories: pre-op history, pre-op examination, and pre-op testing. Usually, a patient undergoing an elective surgery will be scheduled for a pre-operative assessment 2-4 weeks prior to the day of surgery. Also, during this period of pre-op evaluation some patients may require evaluations from more than one physician depending on the different chronic conditions they may have. Besides visiting your PCP for surgical clearance, some patients may need to visit a heart doctor, a lung doctor, among others for a full and focused evaluation.

Pre-Op History

History of Presenting Complaint: a brief history of why the patient has presented to clinic and what procedure the patient has been scheduled for.

Past Medical History: a patient's past medical history is focused and important for specific reasons: 

• Cardiovascular disease (includes hypertension and exercise intolerance) – the reason why? – chances of an acute cardiac event increase during anesthesia. Patients with history of recent heart attack less than 6 months are not fit for surgery.
• Respiratory disease – adequate oxygenation and ventilation reduce risks of acute ischemic events during the operation. Smokers and patients with COPD or sleep apnea, for example, need to be assessed for their lung function and capacity.
• Kidney disease – features of renal problems such as anemia, coagulation problems, and electrolyte imbalances increase the risk of complications during surgery.
• Endocrine disease – diabetes mellitus and thyroid conditions, where certain medications such as insulin may require adjustments to dose and routes of administration during the peri-operative period.
• Other factors to consider – pregnancy in the female patient of reproductive age or ethnic descent to identify possible sickle cell patient.

Past Surgical History: knowledge of prior surgeries, response to anesthetics in the past, if there were adverse responses – were they peri-operative or post-op – are very important to know.

Drug History: full drug history is required to identify medications that require stopping or alteration before the procedure. Also, it is important to know about drug allergies or adverse responses.

Family History: any adverse reactions in surgery of immediate family should be documented, since there are genetic traits that pre-dispose patients to have adverse response to anesthetics such as malignant hyperthermia, a life-threatening condition.

Social history: smoking history and alcohol intake, may clue in how a patient may respond during the post-op period and how well will they heal afterwards. For example, smokers are recommended to discontinue smoking 8 weeks prior to surgery since it's been shown to delay the healing process.

Pre-Op Examination

In the pre-op examination, two types of examinations are performed:

• General examination: to identify any underlying undiagnosed condition that may be present.
• Airway examination: where the anesthesiologist evaluates the patient’s neck and degree of mouth opening and determines a score according to a Mallampati classification (scored from grade I-fully open up to grade IV-fully crowded). This helps to assess the difficulty of intubation and it is usually done on the day of surgery.

Pre-Op Testing

  Pre-operative testing depends on multiple factors such as age, co-morbidities, and type of procedure. Minor surgery (i.e. draining an abscess) rarely need further testing. Intermediate surgery (i.e. knee arthroscopy) may only require some testing, especially in those patients with kidney and/or heart problems. Major surgery (i.e. total joint replacement) requires at least some testing even with normal healthy patients (ASA 1). The National Institute for Health and Care Excellence (NICE) guidelines provide recommendations for specific surgery and ASA grades.

(Link: https://www.nice.org.uk/guidance/ng45/resources/colour-poster-2423836189)

Below are mentioned tests and imaging that can be done prior to a surgical procedure.

• Complete blood count (CBC): to assess for anemia or thrombocytopenia that may require correction to reduce the risk of cardiovascular events.
• Complete Metabolic Panel (CMP): to assess the metabolic status of a patient, provides information on blood glucose levels, electrolyte and fluid balance, as well as your kidney and liver function. From a kidney stand point, baseline renal function, helps determine IV fluid management during and after surgery. Liver function is important in the peri-operative setting because it will help direct medication choice and dosing.
• Clotting Screen: helps identify any bleeding or coagulation problems that may complicate surgery, helps reduce risk of excessive bleeding or development of blood clots.
• Blood typing: determining blood type compatibility is important to know especially in cases where there is greater blood loss than expected that warrants a blood transfusion.
• Electrocardiogram (ECG): performed in patients with history of cardiovascular disease or those undergoing major surgery and provides a baseline if there are post-op signs of cardiac ischemia.
• Echocardiogram (Echo): considered if the patient has a murmur, cardiac symptoms, or signs and symptoms of heart failure. Patients with and ejection fraction less than 35% are not eligible for elective surgery.
• Chest X-ray (CXR): done only when necessary and is not routinely performed. Indicated for patients with respiratory illness who do not have a recent CXR within 12 months, onset of new cardiorespiratory symptoms, recent travel to endemic tuberculosis regions, or significant smoking history.
• Pulmonary Function Tests (PFTs) or Spirometry: may be required for patients with chronic lung disease to assess current baseline and predict post-op pulmonary complications, especially under general anesthesia.
• Other tests: pregnancy test in all women of reproductive age, sickle cell test if patient has family members with sickle cell disease or is of African or Afro-Caribbean descent, urinalysis if there is suspicion of glycosuria or urinary tract infection.

Conclusion

   Pre-operative assessments, besides providing safety to patients undergoing surgery, are an excellent opportunity for patients to gather more information about their state of health and to obtain recommendations to improve their quality of life. Although the surgeon and evaluating physicians work together to determine if a patient is fit for surgery, after everything is assessed and possible risks are outlined and discussed, the final decision to proceed with surgery belongs to the surgeon and the patient.

Author

Ernesto P. Quinones Gonzalez MS3 Third year Medical Student at University of Medicine and Health Sciences (UMHS)