Preoperative care basics
Preoperative care begins as soon as a patient agrees to undergo an operation. It involves history taking, clinical examination, appropriate investigations, risk assessment and informed consent. The purpose of preoperative assessment is to improve outcomes. A simple set of measures could reduce the number of complications following surgery and reduce the average length of hospital stay. Good preoperative care should reduce costs, increase efﬁciency of operating theatres, reduce the number of patients who do not attend for surgery or who are cancelled on the day for clinical reasons, and provide an opportunity for advising patients on their risk factors, including smoking and weight control. Good preoperative care can beneﬁt the patient, the surgical team and the health service.
Preoperative evaluation should include a general medical and surgical history, a complete physical examination and laboratory tests. The most important laboratory tests are:
• Complete blood count
• Blood typing and Rh-factor determination
• Chest x-ray
Further laboratory tests should be performed only when indicated by the patients’ medical condition or by the type of surgery to be performed.
History of presenting complaint
An emergency presentation may warrant an emergency procedure, so the assessment aims to identify factors that may be a problem during or following surgery. Some problems may be readily identifiable and treated in advance; for example, a history of vomiting or intestinal obstruction would indicate that fluid volume replacement is necessary, and this can be done swiftly prior to surgery. A long history of a condition that is scheduled for elective surgical treatment may afford time in which the patient’s comorbid conditions can be improved before surgery.
Past medical history
• Diabetes – whether controlled by insulin, oral hypoglycemic or diet. Severe diabetes may be complicated by gastroparesis with a risk of aspiration on induction of anaesthesia.
• Respiratory disease – what is the nature of the chest problem, and is the breathing as good as it can be or is the patient in the middle of an acute exacerbation?
• Cardiac disease – has the patient had a recent myocardial infarct, or does he/she have mild stable angina? What is his exercise tolerance?
• Rheumatoid arthritis – may be associated with an unstable cervical spine so a cervical spine X – ray is indicated.
• Rheumatic fever or valve disease or presence of a prosthesis – necessitating prophylactic antibiotics.
• Sickle cell disease – a haemoglobin electrophoresis should be checked in all patients of African – Caribbean descent. Homozygotes are prone to sickle crises under general anaesthetic, and postoperatively if they become hypoxic.
Past surgical history
• Nature of previous operations – what has been done before? What is the current anatomy? What problems were encountered last time? Ensure a copy of the previous operation note is available.
• Complications of previous surgery, e.g. deep vein thrombosis, MRSA wound infection or wound dehiscence.
Past anaesthetic history
• Difficult intubation – usually recorded in the previous anaesthetic note, but the patient may also have been warned of previous problems.
• Aspiration during anaesthesia – may suggest delayed gastric emptying (e.g. owing to diabetes), suggesting that a prolonged fast and airway protection (cricoid pressure) are indicated prior to induction.
• Scoline apnoea – deficiency of pseudocholinesterase resulting in sustained paralysis following the ‘short – acting’ muscle relaxant suxamethonium (Scoline). It is usually inherited (autosomal dominant) and so there may be a family history.
• Malignant hyperpyrexia – a rapid excessive rise in temperature following exposure to anaesthetic drugs due to an uncontrolled increase in skeletal muscle oxidative metabolism and associated with muscular contractions and rigidity, sometimes progressing to rhabdomyolysis; it carries a high mortality (at least 10%). Most of the cases are due to a mutation in the ryanodine receptor on the sarcoplasmic reticulum, and susceptibility is inherited in an autosomal dominant pattern, so a family history should be sought.
• Smoking – ideally patients should stop smoking before any general anaesthetic to improve their respiratory function and reduce their thrombogenic potential.
• Alcohol – a history suggestive of dependency should be sought, and management of the perioperative period instituted using chlordiazepoxide to avoid acute alcohol withdrawal syndrome.
• Substance abuse – in particular a history of intravenous drug usage should be sought and appropriate precautions taken; such patients are a high risk for transmission of hepatitis B, hepatitis C and human immunodeficiency virus (HIV ).
Most drugs should be continued on admission. In particular, drugs acting on the cardiovascular system should usually be continued and given on the day of surgery. The following are examples of drugs that should give cause for concern and prompt discussion with the surgeon and anaesthetist:
• Warfarin – when possible it should be stopped before surgery. If continued anticoagulation is required, then convert to a heparin infusion.
• Aspirin and clopidogrel cause increased bleeding and should also be stopped whenever possible at least 10 days before surgery.
• Oral contraceptive pill is associated with an increased risk of deep vein thrombosis and pulmonary embolism; it should be stopped at least 6 weeks preoperatively. The patient should be counselled on appropriate alternative contraception since an early pregnancy might be damaged by teratogenic effects of some of the drugs used in the perioperative period.
• Steroids – patients who are steroid dependent will need extra glucocorticoid in the form of hydrocortisone injections to tide them over the perioperative stress.
• Immunosuppression – patients are more prone to postoperative infection.
• Diuretics – both thiazide and loop diuretics cause hypokalaemia. It is important to measure the serum potassium in such patients and restore it to the normal range prior to surgery.
• Monoamine oxidase inhibitors are not widely used nowadays, but do have important side – effects such as hypotension when combined with general anaesthesia.
Assessment and Minimization of Surgical Risks
The preoperative period is associated with significant cardiovascular stress. Patients with heart disease should be considered high-risk surgical candidates and must be fully evaluated.
• Patients with symptoms of previously undiagnosed heart disease (E.g. Chest pain, dyspnea, pretibial edema or orthopnea)
• Recent history of congestive heart failure
• Recent myocardial infarction
• Severe hypertension
• Varicose vein and deep venous thrombosis
Such patients should be evaluated with the assistance of medical or cardiology consultation. The perioperative monitoring, induction, and maintenance techniques of anesthesia, and post – operative care can be tailored to the specific cardiovascular diseases.
The following respiratory tract problems make patients high risk for surgery;
• Upper airway infections
• Pulmonary infections
• Chronic obstructive pulmonary diseases: chronic bronchitis, emphysema, asthma
Elective surgery should be postponed if acute upper or lower respiratory tract infection is present. Pulmonary infections also predispose to postoperative bronchitis and pneumonia. If emergency surgery is necessary in the presence of respiratory tract infection, regional anesthesia should be used if possible and aggressive measures should be taken to avoid postoperative atelectasis or pneumonia.
Renal function should be appraised
• If there is a history of kidney disease, diabetes mellitus and hypertension
• If the patient is over 60 years of age
• If the routine urinalysis reveals proteinuria, casts or red cells
It may be necessary to further evaluate renal function by measuring creatinine clearance, blood urea nitrogen and plasma electrolyte determination.
Anemia affects the oxygen carrying capacity of the blood, which can complicate the stress of surgery. Anemia in pre-operative patients is of iron deficiency type caused by inadequate diet, chronic blood loss or chronic disease. Care must be taken to differentiate iron deficiency anemia from other anemias.
Iron deficiency anemia is the only type of anemia in which stained iron deposit cannot be identified in the bone marrow.
Megaloblastic, hemolytic and aplastic anemia usually are easily differentiated from iron deficiency anemia on the basis of history and simple laboratory examinations. Patients with iron deficiency anemia respond to oral or parenteral iron therapy. In emergency or urgent cases, a preoperative blood transfusion preferably with packed red cells may be given.
The normal platelet count ranges from 150,000 to 350,000/ml. In the patient with thrombocytopenia but normal capillary function, platelet deficiency begins to manifest itself clinically as the count falls below 100,000/ml. typical manifestations include
• Epistaxis in both sexes and
• Menorhagia in females of reproductive age
• Uncontrolled bleeding which could be intra or post-operative.
Treatment – treat the underlying cause and support with platelet transfusions and clotting factors as necessary.
Diabetics with poor control are especially susceptible to post-operative sepsis. Preoperative consultation with an internist may be considered to ensure control of diabetes before, during and after surgery.
In type – II patients, avoid hypoglycemia by closely monitoring blood sugar on the day of surgery, and possibly by not using the longer acting oral hypoglycemic agents -2 days before operation. Insulin dependent diabetics with good control should be given half of their total morning dose as regular insulin on the morning of surgery. This is preceded or immediately followed by 5% dextrose solution intravenously to prevent hypoglycemia. Regular insulin should then be given every 6 hrs based on plasma glucose level. Chronic medical conditions associated with diabetes may also complicate the preoperative period, e.g. Hypertension, myocardial ischemia which may be silent. These patients should have an extended cardiac work up and receive metoclopramide as well as a non-particulate antacid before surgery.
Elective surgery should be postponed when thyroid function is suspected of being either excessive or inadequate. In Hyperthyroidism, The patient should be rendered euthyroid before surgery if possible. This may take up to 2 months with anti-thyroid medications.
In hypothyroidism, thyroxin should be started before surgery if possible. In all cases, treatment should be started with a very low dose of thyroid replacement to avoid sudden and large workload on the myocardium. The usual tests of thyroid function include T3, T4, and TSH levels.
In addition to the above discussed factors, there are issues which might need special consideration in preoperative patients. The diagnosis of early pregnancy must be considered in the decision to do elective major surgery in reproductive age female.
History of serious reactions or sickness after injections, oral administration or other uses of substances like narcotics, anesthetics, analgesics, sedatives, antitoxins or antisera should be sought.
The patients’ general hydration status should be assessed and made optimal. Nutritional status of the patient also needs evaluation and correction.
After all this, prior to the operation, it is important to have an empty stomach because full stomach can result in reflux of gastric contents and aspiration pneumonitis. In elective surgery, patients should not eat or drink anything after midnight on the day before surgery.