Principles of Preoperative & Operative Surgery (Part I)

Preoperative Evaluation-
Aim is not to screen broadly for undiagnosed disease but rather to identify and quantify any comorbidity that may have an impact on the operative outcome. Used to identify risk factors for postoperative morbidity and mortality. Communication between the surgeon and consultants is essential to define realistic goals and to expedite surgical management.


Cardiovascular:
ASA Classification for anesthetic risk has 5 strata:

I- Normal healthy patient
II- Patient with mild systemic disease
III- Patient with severe systemic disease that limits activity but is not incapacitating
IV- Patient who has incapacitating disease that is a constant threat to life
V- Moribund patient not expected to survive 24 hours with or without an operation

Cardiac Risk Indices-
Goldman Cardiac risk Index (1977), Detsky Modified Multifactorial Index (1986), Eagle’s Criteria for Cardiac Risk Assessment (1989), & Revised Cardiac Risk Index.

The current AHA/ACC recommendations are to start Beta-blockers therapy in the medium to high risk patients undergoing major to intermediate risk surgery as early as possible preoperatively and titrate to a heart rate of 60 beats/min.

An easy, inexpensive method to determine cardiopulmonary functional status for noncardiac surgery is the patient’s ability or inability to climb two flights of stairs. Two flights of stairs are needed because it requires greater than 4 metabolic equivalents (METs).


Pulmonary:

Preoperative evaluation of pulmonary function may be necessary for either thoracic or general surgical procedures.

Necessary tests include FEV1, FVC, and the diffusing capacity of carbon monoxide. Adults with an FEV1 of less than 0.8 L/sec, or 30% of predicted, have a high risk for complications and postoperative pulmonary insufficiency.

Preoperative interventions that decrease postoperative pulmonary complications include smoking cessation (>2 months before planned procedure), bronchodilator therapy, antibiotic therapy for preexisting infection, and pretreatment of asthmatic patients with steroids.
Perioperative strategies include the use of epidural anesthesia, vigorous pulmonary toilet and rehabilitation, and continued bronchodilator therapy.


Hepatobiliary:

Evidence of hepatic dysfunction may be seen on physical examination. Jaundice and sclera icterus may be evident with a serum bilirubin level greater than 3 mg/dL. Skin changes include spider angiomas, caput medusa, palmar erythema, and clubbing of the fingertips. Abdominal examination may reveal abdominal distention, evidence of fluid shift, and hepatomegaly. Encephalopathy or asterixis may be evident. Muscle wasting or cachexia can be prominent.

Here are ways to approach a patient with liver disease in selected cases:

Acute Hepatitis-
Postpone elective surgery at least until liver function tests have normalized.

Chronic Hepatitis-
Surgery is generally considered safe in these patients.

Obstructive Jaundice-
1) Perioperative fluid management to prevent renal dysfunction
2) No dopamine or mannitol
3) Lactulose may be helpful
4) Antibiotic prophylaxis
5) No routine preoperative biliary drainage
6) Check for abnormal coagulation parameters

Cirrhosis-
Child’s A and B- Treat ascites, coagulopathy and proceed to surgery
Child’s C- Postpone until the patient’s Child’s class could be improved or cancel surgery for conservative management

Coagulopathy- Target PT to be no more than 2 seconds above normal
1) Vitamin K- 10 mg subcutaneous
2) FFP if no improvement with Vit K
3) Give cryoprecipitate as needed

Ascites-
1) Fluid restriction
2) Diuretics- Furosemide and/or Spironolactone
3) Paracentesis- may be diagnostic or therapeutic with simultaneous administration of albumin

Encephalopathy-
1) Treat with lactulose
2) Prevent by treating precipitating conditions such as GI bleeding, alkalosis, uremia, avoidance of sedatives

Patients with cirrhosis may be assessed with the Child-Pugh classification, which stratifies operative risk according to a score based on several variables. Child’s class A, B, and C have mortality rates of 10%, 31%, and 76% respectfully during abdominal examinations.

Malnutrition is common in cirrhotic patients and is associated with reduction in hepatic glycogen stores and reduced hepatic protein synthesis.


References:
"Sabiston: Textbook of Surgery" Townsend, Elsevier. 2008

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