Page 18 - Medicine and Surgery

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14 Chapter 1: Principles and practice of medicine and surgery

Respiratory disease Coagulation disorders
The preoperative assessment should identify coexist- Deep vein thrombosis, which may be complicated by

ing respiratory conditions. Patients must be asked pulmonary embolism, is a significant postoperative
about smoking and where possible should be encour- risk. Risk factors include previous history of throm-
aged to stop smoking at least 6 weeks prior to surgery. boembolic disease, specific thrombophilic disorders
Although chest X-rays are often performed as part of (protein C deficiency, protein S deficiency, factor V
the routine assessment of preoperative patients, they Leiden mutations), smoking, obesity, prolonged post-
should not be relied on to identify underlying respi- operative immobility, malignancy and drugs such as
ratory diseases. In general, a chest x-ray is not indi- the combined oral contraceptive pill. Wherever possi-
cated unless there are acute respiratory signs or severe ble, risk factors should be identified and modified (in-
chronic respiratory disease with no film in the last cluding stopping the combined oral contraceptive pill
12 months. 4weeks prior to major surgery). Specific prophylaxis
Patients with chronic obstructive pulmonary disease includessubcutaneouslow-molecular-weightheparin

(COPD) are at significant risk of postoperative res- injections and compression stockings, which should
piratory complications. Patients with severe disease be considered for at-risk patients.
may benefit from a preoperative respiratory opin- Bleeding disorders such as haemophilia, use of anti-
ion and formal respiratory function testing. Preop- coagulant or antiplatelet medication and chronic liver
eratively all therapy should be optimised; pre- and disease may cause perioperative bleeding. Patients
postoperative physiotherapy is essential. Postopera- with known coagulation factor or vitamin K deficien-
tive analgesia should allow pain free ventilation and cies may require perioperative replacement therapy.
coughing, to maximise ventilation and reduce the risk Anti-coagulant medication may be reduced, changed
of postoperative pneumonia. or stopped depending on the underlying indication
for anticoagulation.
Diabetes mellitus
Patients with diabetes are at increased risk periopera- Liver disease
tively both from the diabetes itself (hypoglycaemia and Patients with chronic liver disease may have im-
ketoacidosis) and from the complications of diabetes (is- paired coagulation (vitamin K and coagulation factor
chaemic heart disease, vascular insufficiency, renal fail- deficiencies), altered metabolism of drugs, increased
ure and increased risk of infection). susceptibility to infection and hypoalbuminaemic
Diet-controlled diabetics often require no specific in- oedema. Coagulation deficiencies should be corrected

tervention, but should have perioperative blood glu- prior to surgery and careful fluid balance is essential.
cose monitoring. The patient’s alcohol intake should be elicited; symp-
Patients on oral hypoglycaemic agents should omit toms of withdrawal from alcohol may occur during a

their drugs on the morning of surgery (unless under- hospital admission.
going a short day case procedure) and restart when
oral diet recommences. Perioperative blood sugar lev- Renal disease
els should be monitored. In more major surgery, or Pre-existing renal impairment predisposes to the devel-
when patients are to remain nil by mouth for a pro- opment of acute tubular necrosis. Hypotension should
longed period, intravenous dextrose and variable dose be avoided and urinary output should be monitored so
intravenousshortactinginsulinshouldbeconsidered. that oliguria can be recognised early and treated.
Insulin-controlled diabetics normally require conver-

sion to intravenous dextrose and variable dose intra- Emergency surgery
venous short acting insulin prior to surgery. Close In patients requiring emergency surgery there may not
monitoring of blood sugar and urine for ketones is be enough time to identify and correct all coexistent
essential. Once oral diet is recommenced the patient diseases. It is however essential to identify any cardiac,
should convert back to regular subcutaneous insulin respiratory, metabolic or endocrine disease, which may
therapy. affect anaesthesia. An ECG, chest X-ray and where