The older cancer patient who requires operative intervention poses several specific problems to the anaesthetist. While age in and of itself is not a predictor of long-term survival in the critically unwell older person,1 the higher incidence of comorbidities coupled with the pathophysiological effects of the malignant process and its treatment often render older people at higher risk of morbidity and mortality in the perioperative period. A careful assessment of functional reserve should be undertaken by the anaesthetist to ascertain whether the patient is able to cope with the stress of radical surgery, to plan postoperative care and to allow for informed discussion preoperatively.
Assessment and anaesthetic approach to the older cancer patient
Assessment of cardiorespiratory functional reserve
One of the cornerstones of predicting perioperative risk is the assessment of cardiorespiratory functional reserve. Cardiovascular comorbidities and obesity may cause further respiratory compromise as well as physical deconditioning.
A simple and practical tool to assess a patient's ability to meet the cardiorespiratory demands of the stress of surgery is the concept of metabolic equivalents of task (METs). One MET equates to the oxygen consumption of a 70 kg 40-year-old male in the resting state, and activities which require higher oxygen consumption are described as multiples of this baseline2 (Table 16.1). Studies have suggested that if patients are unable to participate in activities requiring approximately 4 METs they are more likely to experience perioperative cardiovascular complications,3 an increased length of hospital stay, and mortality.4 Such patients should undergo more formal cardiovascular assessment, e.g. cardiopulmonary exercise testing. This is particularly important for high-risk invasive surgery, e.g. intrathoracic and intraperitoneal procedures or operations where anticipated blood loss may exceed 1500 ml. Cardiopulmonary exercise testing calculates several variables including the level of exertion beyond which oxygen supply is limited and therefore anaerobic metabolism becomes significant. This is termed the anaerobic threshold. An anaerobic threshold below 11 ml/min/kg has been shown to be predictive of cardiac morbidity and mortality5 and to correlate well with a MET level <4. It should prompt more intense perioperative monitoring and support, e.g. intraoperative inotropes, postoperative HDU or ITU care and 24-48 h postoperative ventilation to reduce the work of breathing and the burden on the myocardium. Older patients unable to be tested on a bicycle ergometer or a treadmill because of lower limb arthritis or peripheral vascular disease may require other specialist dynamic testing, e.g. dobutamine stress echocardiography.
Table 16.1METs (adapted from Jetté et al.2). |Favorite Table|Download (.pdf) Table 16.1 METs (adapted from Jetté et al.2).
|MET score ||Example activities |
|1 ||Eat and dress, walk indoors around the house |
|2 ||Walk a block on the level, do light work around the house |
|4 ||Climb a flight of stairs or walk uphill, heavy domestic work, run ...|