Before a patient can be taken up for surgery, he or she is evaluated to know the anesthesia risks or fitness for anesthesia and surgery. Recognition of general medical and specific anesthetic risk factors is very necessary as it facilitates the implementation of preemptive measures and improves patient safety.
The specific level of preanesthetic fitness is dependent on the age of the patient, general health and presence of concomitant medical or surgical conditions.
This fitness is checked before the surgery is done and the approach is different for elective and emergency procedure. For an elective surgery, the patient is evaluated in greater detail so as not miss any risk factor before taking the patient for the surgery.
In case of emergency, the patient is examined but the emergency of the procedure is too kept in mind. Therefore the patient may have to be considered for surgery without completing the full work-up.
The anaesthetist who is to be present during the operation usually assess the patient preoperatively.
Factors that Affect Fitness for Anesthesia
In a truer sense there is nothing like unfit for surgery patient. Only the level of risk keeps increasing and the patients are graded according to the risks.
Preoperative evaluation and management is done as follows.
- General history and clinical signs.
- Routine blood investigations
- Chest x-ray and ECG required in older patients
- Further investigation if required
History of the patient is taken in detail and should include the current and past medical and surgical history, family history and personal history (smoking, alcohol). Other important histories to look for as they are deemed relevant are
- Any allergy
- Dug therapy
- Known reactions to drugs and complications
- Birth history in children
Presence of loose tooth or crowns should be sought, which may require preoperative dental treatment.
General physical examination and relevant examination as guided by history is take, The assessment includes
- Venous and arterial access
- Spine examination
- Vital signs
- Cardioorespiratory status
- Routine laboratory tests based on
- History and physical examination
- Age of the patient
- Planned procedure
- Most of the drugs are continued up to the morning of surgery (antiepileptic)
- Some may require dose adjustments (antihypertensive)
- Some drugs need to be disontinued preoperatively. For example
- Aspirin is generally withdrawn 3-5 days before the surgery [aspirin inhibits platelets]
- Contraceptive pills are discontinued 6 weeks before surgery [Increase risk of venous thrombosis]
- Oral anticoagulants should be stopped 4-5 days prior
Fitness Before Anethesia
American Society has a five-category physical status classification system for assessing the fitness before anesthesia. For emergency surgery, the physical status classification is followed by “E”, which increases risk. Emergency is defined as when delay in treatment would significantly increase the threat to the patient’s life or body part. A sixth category was later added. These are:
Various Risk Factors Affecting Fitness for Anesthesia
Following are common causes for postponement of elective procedures
- Uncontrolled hypertension
- Cardiac failure
Correction of hypertension and ischaemic heart disease is essential and needs to be continued through the operative period.
Fast atrial fibrillation needs to be controlled before anaesthesia.
SA node conduction disorders may require pacemaker insertion before anaesthesia though in emergency, external pacing can be used.
Surgery should ideally delayed until at least 6 months have elapsed in cases of myocardial infarction.
Patients with valvular disease will need corrective treatment of any preoperative infections.
The selected patients may require exercise tolerance test and echocardiography.
Electrolyte abnormality or anemia should be corrected.
Pain, surgical stress and temperature loss put increase in demand during and after surgery and load on cardiac functions. This should be taken into account.
Lung Disease and Other Respiratory diseases
Though most of the surgeries do not require detailed pulmonary function assessment beyond clinical examination, those undergoing thoracic surgical procedures require that.
Asthma, chronic respiratory failure and other affections of the lung may cause decrease in oxygen blood.
A blood gas analysis will show oxygen saturation and blood gas tensions preoperatively.
The need for postoperative ventilatory support should be anticipated.
In case of pulmonary affections, regional anaesthesia, if feasible, is preferable to general anesthesia.
The patient should be empty stomach before surgery as aspiration of gastric contents carries a high risk of acid pneumonitis, pneumonia and death. But that is not always possible in emergency surgeries and therefore higher risk.
H2-receptor blocking agents such as ranitidine are administered if there is an increased risk of regurgitation, about two hours before surgery.
Anesthesia in the presence of jaundice carries a high risk of renal damage.
Hereditary metabolic disorders and familial porphyria are associated with high anesthetic risks.
So is pheochromocytoma.
Diabetes and adrenal suppression from steroid therapy are also common metabolic issues which increase the risk of surgery and anesthesia.
For diabetics, intraoperative sugar level monitoring is required while patient is given intravenous infusion of glucose with soluble insulin. Along with insulin, plasma potassium levels need to be controlled.
Patients who are receiving corticosteroids or who have received them in the past 2 months require supplemention with hydrocortisone during and after surgery to avoid adrenal insufficiency (Addisonian crisis).
Coagulation disorders need careful assessment before surgery with a coagulation screen, or clotting factor and platelet measurements.
Anticoagulant drugs need to be withdrawn before surgery as noted above or dosage need to be adjusted,
In cerebral disease, trauma, hypoxia, hypercarbia and respiratory obstruction raise intracranial pressure and can cause cerebral damage.
Care of the neck during intubation is necessary if a cervical fracture is suspected. Skull traction and awake intubation under local anaesthesia are sometimes used.
Anticonvulsant drugs must be continued during surgery on epileptic patients, and this may necessitate using intravenous administration.
In peripheral neuropathies and myopathies may require prolonged postoperative ventilation.
General anesthesia is preferred. Tricyclic antidepressants and monoamine oxidase inhibitor drugs potentiate sympathomimetic agents so adrenaline and cocaine must be avoided.
Pethidine can also cause hypertension with these drugs.