The Importance of Preoperative Evaluation for Non-Cardiac Surgery

The response to surgical stress is activated by the afferent input to the hypothalamus from the area of ​​tissue damage and this produces endocrine, metabolic and inflammatory responses. The endocrine stress response increases concentrations of cortisol, corticotropin, growth hormone, catecholamines, renin, and antidiuretic hormone (ADH).

Metabolic changes such as the catabolism of carbohydrates, fats and proteins provide the increase in energy necessary for the production of glucose and acute phase proteins. Salt and water metabolism is influenced by HAD (which promotes the retention of free water and the production of concentrated urine) and renin/aldosterone (which promotes the reabsorption of sodium and water).

The inflammatory response to surgery is produced mainly by the release of cytokines (interleukin-1, interleukin-6 and tumor necrosis factor alpha) from leukocytes, fibroblasts and endothelial cells in the area of ​​damaged tissue.

These cytokines initiate a local response, but also a more systemic acute phase response, with hepatic production of acute phase proteins. The magnitude of the surgical stress response is proportional to the degree of surgical injury. The effect of HAD lasts 3 to 5 days after the operation, while the effects of cytokines last 48 to 72 hours.

Anesthetics contribute to numerous perioperative physiological changes .

There are two types of anesthesia: general and neuraxial. The choice of the most appropriate one is up to the anesthetist. General anesthesia (GA) is made up of the triad of hypnosis, analgesia and relaxation. During the induction phase, the combination of a sedative-hypnotic (propofol, etomidate or ketamine), an auxiliary (midazolam, opioid or lidocaine) and a neuromuscular blocker (rocuronium, vecuronium or cisatracurium) is used.

An inhalation agent (sevoflurane, desflurane, isoflurane, or nitric oxide) may be added once initial loss of consciousness is achieved. Maintenance of anesthesia is achieved by an inhalation agent, intravenous anesthesia, or, most commonly, a combination of both. GA produces multisystem physiological changes. The most important effects are hypotension and respiratory distress.

Neuraxial anesthesia , such as spinal and epidural, creates distinctive physiological effects due to blockade of the sympathetic nervous system, equivalent to a sympathectomy. This occurs above the sensory level and causes hypotension and bradycardia.

Patients with hypovolemia or preload-dependent heart disease (such as aortic stenosis or hypertrophic cardiomyopathy) are at risk for major complications, including cardiac arrest and death. Respiratory effects are a feeling of dyspnea and a decrease in expiratory effort and cough strength.

There may be paralysis of the accessory muscles and the diaphragm if a high spinal level is reached. Finally, afferent and efferent nerve signals to the bladder are blocked, with the appearance of urinary retention.

In summary, it is essential to keep in mind that the response to surgical stress and anesthesia affects multiple organ systems in order to know how to treat them during the perioperative period.

Preanesthesia medical evaluations should systematically study risk assessment and modification. For this, it is necessary to analyze the surgical urgency, the specific risk of surgery and the status of important comorbidities. With this information, recommendations can be made to modify pre- and postoperative risk.

> Surgical emergency

Surgical urgency is one of the most important determinants of surgical risk and its treatment. Numerous guidelines recommend evaluating surgical urgency as the first step in the medical evaluation prior to anesthesia. Urgency or emergency increases the risk of complications in relation to the same procedures when they are scheduled.

The most recent guidelines from the American College of Cardiology (ACC)/ American Heart Association (AHA) define the types of surgery based on specialist consensus:

(1) emergency surgery: life or limb in danger if not intervened within 6 hours;

(2) emergency surgery: life or limb endangered if not intervened within 24 hours;

(3) surgery needed within 1 to 6 weeks; and

(4) elective surgery: can be postponed up to 1 year.

> Specific risk of surgery

The intrinsic risk of a surgical procedure depends on the amount and site of tissue disruption, hemorrhage, fluid displacement, and hemodynamic effects, among other variables. Assessment of the specific risk of surgery is included in the US, European and Canadian guidelines for preoperative cardiac evaluation.

The risk of major adverse cardiac events was historically divided into low (<1%), intermediate (1% to 5%), and high (>5%) risk.

More recent guidelines recommend a binary approach and use low risk (<1%) and high risk (≥1%) for better integration with clinical decision making.

> Patient-specific risk

Patient-specific risk is attributed to comorbidities that impact the overall risk of a surgical procedure. History and physical examination are essential to identify these risk factors.

A limitation of many risk assessment tools is the assumption that patients are medically stable and therefore these tools are not accurate in patients with acute or progressive symptoms. When these symptoms are identified, they should be evaluated as would be done in the non-perioperative setting.

Furthermore, perioperative assessment tools come from populations where high-risk diseases with low prevalence, such as pulmonary hypertension and cirrhosis, are often not taken into account in the models.

The risk in patients with these diseases is thus underestimated. There is also the possibility that absolute risk estimates may not be accurate. It is essential to know the strengths and limitations of the tools used.

The authors of this article recommend evaluating risk according to each organic system and outlining a structured approach. Surgical urgency, surgical risk, and patient-specific risk factors are necessary data for clinical decision algorithms and guidelines from scientific societies.

The combined clinical and surgical risk of cardiac and pulmonary complications, venous thromboembolism, postoperative nausea and vomiting, and disturbances of consciousness should be evaluated in all patients.

> Cardiac evaluation

The 2014 ACC/AHA guidelines for perioperative cardiac evaluation created an algorithm to identify patients in whom stress testing may be considered.

It is essential to identify patients with acute coronary syndrome , high perioperative risk of major adverse cardiac events based on validated risk assessment, and poor functional capacity. (< 4 METS Measurement of exercise tolerance before surgery).  

The Canadian Cardiovascular Society recommends formally evaluating only patients with already diagnosed cardiovascular disease or who are 45 years or older who will undergo surgery requiring at least one night of hospitalization. Instead of stress tests, they prefer postoperative monitoring of troponin guided by B natriuretic peptide values.

In patients requiring emergency surgery, clinical risk stratification and intra- and postoperative monitoring should be performed. Those who do not need emergency surgery will be evaluated for signs and symptoms of acute coronary syndrome.

Although not specifically mentioned in the guideline, it is advisable to do this in patients with other acute or unstable cardiac conditions. For patients who are stable, the next step is to assess the risk of major adverse cardiac events by combining clinical and surgical risk.

For patients with a risk of less than 1%, no other studies are necessary and surgery can be performed. For those with risk > 1%, it will be advisable to evaluate functional capacity. If this is ≥ 4 MET, surgery can be performed. If it is < 4 MET, a pharmacological stress test can be performed if it is believed that the results could affect treatment.

The guidelines recommend evaluating patients for clinical evidence of heart failure, valvular disease, arrhythmia, or other cardiac disorders.

Patients with established cardiovascular disease also need other considerations. Those with a history of myocardial infarction or stroke within the past year should be carefully studied due to numerous factors, including antiplatelet medications and the risk of subsequent events.

> Pulmonary evaluation

Pulmonary complications contribute to perioperative morbidity and mortality to the same extent as cardiac complications. Pulmonary complication rates are higher in upper abdominal, thoracic, and head and neck surgery due to their impacts on respiratory mechanics.

Patients should be evaluated for the presence of new or progressive pulmonary disorders, as well as their impact on functional status. This includes evaluating obstructive sleep apnea (OSA) and hypoventilation syndromes using a validated screening instrument.

> Venous thromboembolism and hemorrhage

The risk of venous thromboembolism (VTE) and bleeding should be evaluated in all surgical patients. Tissue damage, proinflammatory states such as cancer, location and duration of the procedure, and immobilization contribute to the increased risk of VTE. There are specific guidelines from the American College of Chest Physicians for total joint arthroplasty, hip fracture, spine surgery, and outpatient surgery.

Bleeding risk assessment includes procedural bleeding, consequences of bleeding (such as the potentially devastating consequences of neurosurgical or reconstructive procedures), and patient factors, such as medications or comorbidities.

> Alteration of consciousness

Impaired consciousness contributes greatly to morbidity and mortality in elderly patients. Although risk should be assessed in everyone, special attention is necessary for those with or suspected cognitive dysfunction. It is recommended to evaluate cognitive function , document risk factors, and identify contraindicated medications for high-risk patients.

> Postoperative nausea and vomiting

Postoperative nausea and vomiting are a common complication that, in addition to affecting the patient’s well-being, increases the risk of pulmonary complications. Numerous risk factors have been identified and several models exist to predict these symptoms within 24 hours.

> Other risks

Many disorders that can be identified with a thorough evaluation require further consideration. Special attention should be paid to diseases that affect hemodynamics, fluid balance, healing, infection and bleeding.

The goal of the preoperative history and physical examination is to identify elements necessary for preoperative risk assessment and reduction, anesthesia management, and optimization of medical comorbidities.

Medical, surgical, family, and social history should be obtained. It is also important to document the severity and stability of chronic diseases. The preoperative history should evaluate functional capacity in metabolic equivalents (METs), including whether the patient can meet 4 METs regularly and without significant symptoms.

Examples of 4 METs of activity are walking on a flat surface at 6 km per hour, climbing a staircase without stopping, or doing heavy household work such as vacuuming. Patients often do not report METs accurately. When the evaluation of the MET was compared with other preoperative markers of physical fitness such as the DASI ( Duke Activity Status Index) questionnaire, it was found that this is superior to the subjective evaluation of the MET.

Several risk calculators require knowledge of the patient’s preoperative functional status as defined by the NSQIP, which classifies the patient as independent, partially dependent, or dependent based on the degree of assistance from another person or devices needed to carry out surgery activities. daily life.

For the majority of patients who will undergo surgery, very few studies are indicated.

> Cardiovascular

Routine electrocardiogram (ECG) is not indicated for asymptomatic patients undergoing low-risk surgeries. The ECG is recommended for patients who will undergo high-risk surgery or for patients with known cardiovascular disease.

It is reasonable to obtain a preoperative ECG in patients who are very obese (body mass index [BMI] >40 kg/m2) or who have at least one risk factor for cardiovascular disease, such as diabetes, hypertension, hyperlipidemia, smoking, or low tolerance to alcohol. exercise.

Stress testing may be considered in specific situations, such as high-risk patients with poor functional capacity (40 kg/m2).

> Pulmonary

Pulmonary functional examination is not routinely recommended since clinical evaluation better predicts postsurgical pulmonary complications.

OSA risk screening is carried out with a validated tool such as the score obtained for snoring, fatigue, observed apnea, hypertension, BMI, age, neck circumference and male sex (STOPBang Score).

> Hematological

The study of hemoglobin and hematocrit is not indicated preoperatively for the majority of patients without a prior diagnosis of anemia. The American Society of Anesthesiologists recommends these tests in certain elderly patients and in those who will undergo surgeries that may cause significant bleeding. Platelet counting would be indicated in patients suffering from hematological or liver disease.

Coagulation studies are also not recommended since coagulopathies are rare in asymptomatic people and most those with hemostasis problems will have symptoms before being evaluated for a preoperative examination. Regarding perioperative management of patients receiving anticoagulants, warfarin can be monitored with prothrombin time (PT) and this should be monitored preoperatively in patients receiving warfarin.

With the new anticoagulants, routine testing is not necessary, but it may be necessary to monitor residual activity preoperatively. Dabigatran is monitored by ecarin time, but significant activity is unlikely if the dilute thrombin time or activated partial thromboplastin time is normal. Apixaban, edoxaban, and rivaroxaban are factor Xa inhibitors that are monitored with a specific anti-Xa inhibitor assay.

> Biochemical analysis

The American Geriatrics Society recommends testing creatinine before surgery. The same is recommended in patients with kidney disease, or who take medications that alter electrolytes, are exposed to nephrotoxic agents or need cardiac risk stratification, since several risk indices use creatinine as one of the risk factors.

Routine analysis of electrolytes and blood glucose is not indicated in asymptomatic patients. For patients undergoing vascular or orthopedic surgery, it is reasonable to use hemoglobin A1c as a screening tool. In patients with diabetes, hemoglobin A1c values ​​should be studied in order to control their diabetes treatment before surgery.

Analysis of liver enzymes is also not recommended in asymptomatic patients. For patients with liver disease, testing should be performed to calculate a score with the Model for End-stage Liver Disease (MELD) or the Child-Pugh score (creatinine, bilirubin, prothrombin time, and albumin).

Analysis of albumin, prealbumin and transferrin values ​​is not recommended for asymptomatic patients, with the possible exception of geriatric patients. These are reasonable tests when nutritional status is concerning or there are underlying medical problems.

Low albumin values ​​(<22g/dl) suggest malnutrition and are related to poor surgical results. Additionally, other problems such as nephropathy and liver disease can affect albumin values. Transferrin also indicates the patient’s iron status and therefore should be interpreted in conjunction with iron values.

Urine analysis and culture are not recommended for screening for asymptomatic bacteriuria. An exception would be high-risk surgeries, such as urological and gynecological.

Methicillin-resistant Staphylococcus aureus (MRSA) infections are a risk for the hospitalized patient and an even greater risk for the surgical patient. A 2010 meta-analysis concluded that the evidence is not conclusive to recommend routine screening for staphylococcal colonization.

Pregnancy cannot be ruled out based on history alone, and knowing that the patient is pregnant can change the surgical plan. Pregnancy testing is recommended for all women of childbearing age.

> Geriatric

Geriatric patients have a greater number of comorbidities, including cardiovascular disease, cerebrovascular disease, chronic kidney disease, hypertension and diabetes. Cognitive deficiencies and disorders of consciousness, malnutrition, frailty and falls are specific problems of the geriatric population.

Current guidelines recommend screening for cognitive deficiencies, which are a risk factor for altered consciousness postoperatively, and a history of falls. Frailty and malnutrition should be evaluated in geriatric patients. Recent studies suggest that diagnosing and treating both preoperatively with a “prehabilitation” program improves postoperative outcomes.

In the case of urgent surgery, it is beneficial to pay attention to postoperative rehabilitation and nutrition. The patient’s wishes regarding advance directives, especially regarding intraoperative resuscitation, should be taken into account.

> Pregnancy

Nonobstetric disorders requiring surgery during pregnancy include appendicitis, gallstones, ovarian torsion or neoplasia, and trauma. Preanesthesia medical evaluation should include an obstetrician and care should be taken to ensure that medications are not teratogenic.

It is recommended to postpone scheduled surgeries until after childbirth and perform surgery with a defined period during the second trimester, since the risk of spontaneous abortion is lower.

Urgent surgery is generally safe, although the risks may be higher than in non-pregnant patients. The mechanical effects of pregnancy in the third trimester may have perioperative consequences. Postponing urgent surgery is associated with more complications and patients should not be deprived of indicated surgery solely because of pregnancy.

> Human immunodeficiency virus (HIV)

The evaluation of these patients is similar to that of those without HIV, with special attention to the most common disorders of patients with HIV. These are liver and kidney dysfunction, coronary heart disease, coagulopathy, thrombocytopenia, neutropenia, substance use disorders, and MRSA infection/colonization.

Organ dysfunction and nutritional status are the best risk predictors. It is recommended to optimize antiretroviral treatment (ART) before elective surgery, as well as monitor the possible interaction of antiretrovirals with other medications. ART will be continued postoperatively with as little interruption as possible.

If interruption is necessary, the ART specialist should be consulted. Patients with a history of P. jirovecii are are at increased risk of spontaneous pneumothorax, which may manifest as postoperative dyspnea.

> Chronic liver disease

Patients with cirrhosis have a higher risk of surgical and anesthesia complications. MELD and Child-Pugh scores predict postoperative risk in patients with cirrhosis. Those with MELD score <10 are low risk, while those with score >10 are high risk. This risk increases with increasing MELD. The 90-day postoperative mortality in patients with MELD scores of 15 or more is greater than 50%, and is greater than 85% for patients with MELD score > 25.

Patients with non-alcoholic steatohepatitis are at increased risk of coronary heart disease due to the likelihood of dyslipidemia.

For patients with hemochromatosis, screening for cardiomyopathy should be considered. Patients with ascites are at increased risk of dehiscence and hernia at the incision site; They should be treated with diuretics and sodium restriction to reduce the ascites burden preoperatively. Hepatic encephalopathy may develop or worsen due to narcotic-induced constipation and the use of benzodiazepine medications. The use of these drugs should be reduced as much as possible.

> Refusal to receive blood or blood products

The best-known rejection of blood products comes from the religious group of Jehovah’s Witnesses, who believe that accepting blood transfusions can affect their eternal salvation. Within this group, some accept albumin or coagulation factor concentrates.

Perioperative evaluation should focus on carefully specifying the patient’s wishes, especially in life-threatening situations. Correct a coagulopathy with factors that are acceptable to the patient and optimize the production of erythrocytes with iron. Vitamin B12 and folates as appropriate may improve results.

> Obesity

The overweight (BMI, 25 - 30 kg/m2) but otherwise healthy patient or the patient with class 1 obesity (BMI, 30 - 35 kg/m2) has no increased risk of adverse outcomes after noncardiac surgery.

However, there is an increased risk of comorbidities that adversely affect postoperative outcomes, including OSA, hypoventilation syndrome, hypertension, heart disease, diabetes mellitus, metabolic syndrome, and chronic kidney disease. Perioperative evaluation should be performed and the possibility that the diagnosis of these diseases may be missed should be taken into account.

Obesity class 2 and 3 (BMI, 35 kg/m2), even in otherwise healthy people, is an independent risk factor for adverse perioperative outcomes, such as pneumonia, respiratory failure, and postoperative wound infections. The perioperative treatment of these diseases does not differ in obese or non-obese patients.

The postponement or cancellation of a surgical intervention should be considered when the risk outweighs the expected benefit. Although risk assessment tools can be helpful, this is ultimately a clinical decision that must incorporate the surgical team, the medical team, and the patient’s values.

Preoperative medical optimization should focus on significantly reducing modifiable perioperative risk. Unchangeable risk is managed with increased monitoring or postoperative preventive strategies. According to studies, postoperative mortality is more related to the way complications are treated than to their incidence.

It is rarely appropriate to delay emergency surgery.

However, unstable or progressive symptoms, especially those affecting the cardiac or respiratory systems, should be evaluated even in urgent surgeries. Interventions that are scheduled or have a defined time frame should only be postponed for studies that could alter treatment. If confirmatory studies cannot be performed preoperatively, patients should be treated as if they had the suspected problem.

Perioperative hypertension is common, but does not influence complication rates when it is less than 180/110 mm Hg. Patients requiring emergency surgery with blood pressure higher than this may require parenteral antihypertensive treatment. Upper respiratory tract infections are not associated with major complications in adults.

Smoking and substance use increase complications directly through their effects and indirectly through increased risk of diseases such as coronary artery disease .

Stopping smoking can be beneficial for as little as 2 weeks, although the greatest effect is obtained after at least 8 weeks.

Preoperative anemia is associated with numerous complications. It is reasonable to delay elective surgery to correct significant anemia that has a treatable cause.

Communication and documentation are key in preoperative risk assessment. The standardized approach to this documentation ensures that all important perioperative risks and disease management issues are addressed.

This will reduce unnecessary delays and complications in high-risk patients. Risk assessment in each body system along with disease-specific recommendations can be very helpful in achieving this goal.

• Preanesthesia medical evaluations should be thorough to provide both risk stratification and appropriate modification for medical and surgical risk.
   
• Equal importance should be given to preoperative interventions and postoperative monitoring.
   
• The structured, cooperative approach is beneficial for both medical and surgical teams.