Pre Anesthetic Assessment (History, Physical Examination, Investigations)
Pre Anesthetic Assessment (History, Physical Examination, Investigations)
The role of the anesthetist begins not in the operating theatre but in the ward. The pre-operative assessment is designed to present the patient for surgery in the best possible condition.
Important patient care decisions reflect the preoperative evaluation, creating the anesthesia plan, preparing the operating room, managing the intraoperative-anesthetic, and postoperative care and outcome.
The goals of preoperative evaluation include assessing the risk of coexisting diseases, modifying risks, addressing patient's concerns, and discussing options for anesthesia care. The beginning trainee should learn the types of questions that are the most important to understanding the patient and the proposed surgery.
The purpose of pre operative assessment is to:
- Establish rapport with the patient and care giver
- Offer the anesthetist an opportunity to define the patient's medical and surgical problems,
- Plan the anaesthetic technique.
- Identify further investigation, consultation, and treatment for patients whose condition is not optimal.
- Provide information and reassurance for the patient during this stressful time.
- Review pharmacology of drugs and their anesthetic implication
The overall objective is reduction of perioperative morbidity and mortality
Review of patient chart may help you to know the patient. Any problems encountered during past anesthetics must be fully investigated. Records of previous occasions yield a wealth of information on response to various drugs, intubation difficulties, allergic responses and Post operative problems. Family anesthetic history is also important because certain abnormal and possibly dangerous responses to drugs (e.g. malignant hyperpyrexia, Suxamethonium apnea) tend to run in families.
- Respiratory problems: cough, sputum, smoking, asthma, breathlessness, exercise tolerance, history of previous TB, bronchitis etc
- Cardiovascular disease:
- Difficulty in breathing, palpitation, chest pain, ankle edema
- Previous heart attacks
- Exercise tolerance
- Other illnesses, e.g. diabetes, renal disease, hiatus hernia, epilepsy
- Alcohol and drug intake
- Smoking habits
Past Surgical Procedures as well as that for which the patient is being assessed are important.
Some operations, such as those on the heart, lungs, kidneys and CNS may tend to interfere with vital functions under anesthesia.Drug History
The following drugs, previously or currently being taken may influence present anesthesia.
- Prolonged steroid therapy (> 10mg prednisolone/day) results in atrophy of the adrenal glands so that they cannot secrete extra hormones in time of stress. Collapse, with a fall of blood pressure, may ensue. Many different regimes have been described to provide perioperative steroid cover. Consider a stress dose of hydrocortisone 50-100 before operation and after operation.
- Antihypertensive drugs: These drugs produce their effect by a reduction in peripheral vascular tone. This tends to interfere with circulatory homeostasis under anesthesia. Most patients are left on these tablets until the day of operation. The anesthetist must bear in mind that these patients cannot compensate for such stresses as blood loss, changes in posture, intermittent positive pressure ventilation (IPPV), etc. in the same way as normal patients can. Further, they may react badly to drugs such as thiopentone which can cause a fall in blood pressure. All patients taking anti hypertensive drugs have to be continued till the morning of operation. If heavy bleeding is expected drugs such as enalapril and their group has to be discontinued a day before surgery. Patients on loop diuretics has to have electrolyte determination before operation.
- Monoamine oxidase inhibitors (MAOI): They interact with narcotic analgesics, e.g. pethedine and morphine and result in - severe hypo or hypertension, coma, convulsions, Cheyne Stokes respiration and death. They also react abnormally with presser drugs and potentiate the side effects of barbiturates. The effects of MAOI last from 1 to 2 weeks depending on the drugs. Suspension of MAOI will be necessary for major surgery requiring post-operative analgesia. This must be done 10 to 14 days pre-operatively. Before discontinuation the advantages and disadvantages for the patient has to be considered and consultation with a senior has to be made.
- Beta-blockers: Commonly used for the treatment of hypertension, cardiac arrhythmias, ischemic heart disease etc. In most cases the patients may remain on these drugs but remember that they cannot compensate efficiently, in the face of cardiovascular stress and drugs that decrease blood pressure or heart rate has to be titrated according the patients response.
- Diuretics: Prolonged diuretic therapy interferes with electrolyte balance. This must be checked pre-operatively (especially potassium).
- Insulin and other oral glycemic control drugs: Patients on such treatment must be carefully assessed by the anesthetist and the treating physician for pre and post-operative care. They have to be scheduled as a first case and they have to be put on sliding scale or modified sliding scale according the treating physicians experience or health institution guideline/protocol. There should be a possibility to have regular insulin and dextro stick intra operatively. For detail see the module on coexisting diseases
- Antibiotics: Large parenteral doses of antibiotics - neomycin, streptomycin and others - have been known to potentiate the action of non-depolarizing relaxants.
- Phenothiazines: These cause peripheral vasodilatation and result in a fall in blood pressure under anesthesia. They also potentiate the action of narcotics and barbiturates and these drugs must be used in smaller doses.
- General appearance of the patient in bed including age and approximate weight. For instance, is the patient dysphonic? Nervous? Sweating? Or suffering from anemia, cyanosis, jaundice, edema, dehydration (any evidence of early dehydration must be detected. Note: temperature, skin turgor, tongue, urine output, pulse, superficial veins etc)
- Pathological problems: difficulty in opening the jaws, difficulty in extending the neck, tumors or inflammation of the neck, burns, contractures of the neck. Finally, assess the psychological state of the patient. This will influence the choice between regional or general anesthesia and also the premedication required.
Airway Examination: as explained in module 1 sessions 3
Note any anatomical features that would hinder the maintenance of a clear airway or interference.
1. Respiratory System
- Note rate and type of breathing is it noisy, labored, and obstructed.
- Shape of chest and movement of the chest.
- Deformities of the spine.
- Sputum color, quantity (if any) of nasal discharge.
- Cyanosis central or peripheral.
- Clubbing of fingers.
- Confirm chest movement.
- Note the position of the trachea.
- Check for the presence of enlarged supraclavicular lymph nodes.
Percussion: Compare the percussion notes at equivalent positions on both sides of the chest.
- Breath sounds.
- Accompaniments: crepitations, rhonchi.
- Vocal resonance.
2. Cardiovascular System
- The pulse Note the rate, rhythm, volume and character of the pulse wave and vessel wall. Check the peripheral pulses, including arterial pulsations in the neck.
- Jugular venous pressure
- Blood pressure
- Color of mucous membrane: cyanosed or anemic
- edema (especially dependent)
Examination of the Heart
- Inspection and palpation To detect and confirm the position and quality of the apex beat. Displacement of the apex beat may suggest cardiac enlargement. Confirm also the presence of any thrills over the pericardium.
- Auscultation: Listen to the heart sounds and identify murmurs.
3. Other System
Depending on the patient it may be necessary to examine the other systems e.g. the central nervous system.
Investigations depend on the operation type, underline coexisting diseases, age of the patient and facilities available.
- Complete Blood Count( CBC) or at least hemoglobin, blood group and RH
- Chest x-ray where indicated for aged and patients with respiratory problems
- ECG in patients with a history of cardiac disease
- BUN/creatinine and serum electrolytes for patients age of greater than 60 years, renal problems, on diuretics
If there is liver disease:
- Liver function tests
- Prothrombin index
If there is diabetes:
- Fasting blood sugar
Guidelines for Pre Operative Investigations
- All patients: for sugar, blood, and protein
- ECG => Age > 50 years - History of heart disease, hypertension or chronic lung disease -A normal previous trace within 1 year is acceptable unless there is a recent cardiac history
- Males with advanced age
- All females
- All major surgery
- Whenever anemia is suspected
- Creatinine and electrolytes
- Age > 60 years
- All major surgery
- Diuretic drugs
- Suspected renal disease
- Blood glucose
- Diabetic patients
- Coagulation screen => History of bleeding tendency
- Pregnancy test => Whenever there is any chance of pregnancy
- Chest radiograph
- Not routine
- Acute cardiac or chest disease
- Chronic cardiac or chest disease that has worsened in the last year
- Risk of pulmonary TB
- Malignant disease