Respiratory system

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Respiratory system

Enquire about symptoms related to :

chronic obstructive lung disease, for example production of sputum (volume and color);
dyspnoea;
asthma, including precipitating factors.

Patients with pre-existing lung disease are more prone to postoperative chest infections, particularly if they are also obese, or undergoing upper abdominal or thoracic surgery. If an acute upper respiratory tract infection (URTI) is present, anesthesia and surgery should be postponed unless it is for a life-threatening condition. A patient’s ability to perform everyday physical activities before having to stop because of symptoms (e.g. chest pain, shortness of breath) fives a very useful indication of both cardiac and respiratory reserve and can be assessed by asking questions such as:

How far can you walk along the flat and uphill?
Are you able to do housework or go shopping?
How many stairs can you climb before stopping?
Could you run for a bus?

Patients with severe musculoskeletal dysfunction (e.g. osteo- or rheumatoid arthritis) may not be able to exercise to the limit if their cardiorespiratory reserve.

Other conditions which are important if identified in the medical history

Indigestion, heartburn and reflux

. These may indicate the possibility of a hiatus hernia, which increases the risk of regurgitation and aspiration.

Rheumatoid disease. Patients are often chronically anemic and have severely limited movement of their joints which makes positioning for surgery and airway maintenance difficult.

Diabetes. Patients have an increased incidence of ischemic heart disease, renal dysfunction, and autonomic and peripheral neuropathy . These increase the incidence of intra- and postoperative complications, particularly infections.

Neuromuscular disorders. Care must be taken when using muscle relaxants in these patients. Coexisting heart disease may be worsened by anesthesia and restrictive pulmonary disease predisposes patient’s postoperative chest infection.

Chronic renal failure. Patients are usually anemic, have electrolyte abnormalities and altered drug excretion, which restricts the choice of anesthetic agents.

Jaundice. This usually indicates infective or obstructive liver disease. Drug metabolism may be altered. The patient’s coagulation must be checked preoperatively.

Epilepsy. If well controlled, epilepsy is not a major problem but it is advisable to avoid anesthetic agents which are potentially epileptogenic (e.g. enflurane, see page 60).

FAMILY HISTORY

All patients should be asked whether there are any known inherited conditions in the family or if any family members have ever experienced problems with anesthesia. A history of prolonged apnea after anesthesia suggests pseudocholinesteraes deficiency (see page 65) and an unexplained death suggests malignant hyperpyrexia (see below). Surgery should be postponed if any conditions are identified and the patient investigated appropriately. In the emergency situation, anesthesia must be adjusted accordingly, for example avoidance of triggering agents in a patient with a family history of malignant hyperpyrexia. DRUG HISTORY AND ALLERGIES Identify all medications, both prescribed and self-administered. Patients will often forget about the oral contraceptive pill (OCP) and hormone replacement therapy (HRT), unless specifically asked. The incidence of use of medications rises with age and many of these drugs have important of interactions with anesthetics. The more common and important ones are listed at the end of this chapter (see Table 1.6). Allergies to drugs, topical preparations (e.g. iodine), adhesive dressings and foodstuffs should be noted. SOCIAL HISTORY

Smoking. Ascertain the number of cigarettes or the amount of tobacco smoked per day. Oxygen carriage is reduced by carboxyhemoglobin and nicotine stimulates the sympathetic nervous system causing tachycardia, hypertension and coronary artery narrowing. Smokers have a significant increase in postoperative chest infections, chronic lung disease and carcinoma. Stopping smoking for 8 weeks improves the airways; for 2 weeks reduces their irritability; and for as little as 24 hours prior to anesthesia decreases carboxyhemoglobin levels.

Alcohol. This is measured as units consumed per week,>50 units /week causes induction of liver enzymes and tolerance to anesthetic drugs. The risk of alcohol withdrawal syndrome postoperatively must be considered.

Drugs. Ask specifically about the use of drugs for recreational purposes; including type, frequency and route of administration. This group of patients is at risk of infection with hepatitis B and human immunodeficiency virus (HIV). There can be difficulty with venous access in those using the intravenous (I.V.) route, due to widespread thrombosis of veins. Withdrawal syndromes can occur postoperatively.

Pregnancy. The date of the last menstrual period should be noted in all women of childbearing age. Anesthesia increases the risk of inducing a spontaneous abortion in early pregnancy. There is an increased risk of regurgitation and aspiration in late pregnancy. Elective surgery is best postponed until after delivery.

MALIGNANT HYPERPYREXIA

This is rare inherited disorder of skeletal muscle metabolism, precipitated by exposure to certain anesthetic drugs. The incidence varies, but may be between 1:10000 and 1:40000 anesthetized patients. As the name suggests, the key feature id excess heats production causing a rise in core temperature of at least 2C per hour. It occurs more commonly in patients undergoing certain operations, for example squint surgery, hernia repair, corrective orthopedic surgery or cleft palate repair (see page 69).

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