Managing the high-risk surgical patient

A high-risk surgical procedure can be considered as one in which there is an accepted postoperative mortality rate of more than 1%. Whether a procedure for a given patient is high risk depends on consideration of the technical hazards of the surgical procedure itself – for example, the construction of a gastrointestinal tract anastomosis and the potential for it to break down – and, secondly, the presence of pre-existing disease in the patient of sufficient severity to significantly affect the patient's response to surgery, particularly when poorly managed.

In most cases poor outcome from major surgery arises from a combination of both of these factors, in which the patient with impaired functional reserve is unable to cope with either the physiological demands of the procedure or the stress of complications. An unrecognised and unchecked sequence of adverse events will lead to multiorgan dysfunction syndrome (MODS), multiorgan failure (MOF), and death in the worst cases.

Emergency anaesthesia and cardiothoracic anaesthesia are considered elsewhere ( Chapter 41, Chapter 42, Chapter 44 ), so this chapter will concentrate on the patient undergoing scheduled major non-cardiac surgery. However, the principles of treatment, particularly haemodynamic management, also apply to the patient undergoing an emergency procedure.

What makes an operation high risk?

Major surgery generates a systemic inflammatory response. The magnitude of the inflammatory response, as judged by circulating proinflammatory cytokines, is directly associated with postoperative outcome: higher concentrations of cytokines or other inflammatory markers such as C-reactive protein (CRP) are associated with an increased incidence of postoperative complications. Factors that increase the inflammatory response include surgery involving the gastrointestinal tract, major vascular surgery or cardiac surgery, the need for major blood transfusion, emergency surgery and the presence of decreased tissue perfusion, particularly in the gastrointestinal tract.

The inflammatory response increases oxygen consumption, requiring increases in cardiac output and tissue oxygen extraction. Some patients may not have the physiological reserve to increase cardiac output to the required level, and this group of patients are at higher risk of complications after surgery. Treatment strategies are aimed at identifying high-risk patients early and optimising various aspects of patient care in order to reduce risk and improve outcome.

What makes a patient high risk?

High-risk patients may be elderly with established cardiorespiratory disease, but a significant proportion will not have any documented history of significant comorbidities.

From the 2011 National Confidential Enquiry into Perioperative Deaths (NCEPOD) report ‘Knowing the Risk’, the approximate increased risk of death after surgery compared with no disease present is:

twofold for respiratory disease, ischaemic heart disease, non–insulin-dependent diabetes and cancer;
threefold for cerebrovascular disease, insulin-dependent diabetes, and dysrhythmia; and
fivefold for congestive cardiac failure and documented cirrhosis.

The list of comorbidities is not exclusive, and other conditions such as renal disease, rheumatoid arthritis, obesity and neurological conditions may adversely affect outcome.

The anaesthetist should be aware that the absence of a recognised chronic disease is no guarantee of a good outcome in the older patient undergoing major surgery, but abnormal cardiorespiratory physiology per se generates a high risk.

General risk prediction scoring systems

General (ASA, Surgical Outcome Risk Tool (SORT), and POSSUM) and system-specific (Revised Cardiac Risk Index (RCRI), ARISCAT, PERISCOPE) risk prediction tools are discussed in Chapter 19 . Frailty is increasingly recognised as a risk factor for poor surgical outcome (see Chapter 31 ).

Further investigations for risk assessment

Routine and special investigations

In patients undergoing elective surgery, investigations such as full blood count or urea and electrolytes will not in general be of any significant value in predicting risk, although they may be useful as components of scoring systems such as POSSUM (see earlier) and they may highlight specific abnormalities, such as anaemia, which should be corrected before surgery.

Specialised investigations, including cardiopulmonary exercise testing, are discussed in Chapter 19 .

Reducing risk before surgery

Information from preoperative assessment and investigations, particularly cardiopulmonary exercise testing, can help the clinician answer three important questions relevant to an individual patient's perioperative risk:

1.
Is the patient fit enough for the proposed surgery, or would a less invasive procedure, or even postponement of surgery, be more suitable?
2.
Can the patient's medical condition be improved before surgery, with consequent risk reduction?
3.
Does the patient need high-dependency unit (HDU) or ICU care after surgery, or are they fit enough to return directly to the general ward?

Alternatives to major surgery

The availability of different treatment options will depend on the surgical condition. For instance, surgery for an abdominal aortic aneurysm can be performed by open or endovascular repair; alternatively it may be deferred for investigation and optimisation of medical conditions, or surgery may be inappropriate for a particularly high-risk patient where the risks outweigh the benefits. For colorectal cancer disease, the alternatives to curative-intent surgery are limited, but the risks can still be modified – for instance, by choosing to perform a Hartmann's procedure in a very high-risk patient with a rectal tumour rather than risking an anastomotic leak in a patient with limited reserve. Such decisions have to be taken in conjunction with the patient on a case-by-case basis and with all factors considered.

Fig. 30.1 is an example of a risk assessment and management plan for colorectal cancer surgery patients, based on clinical findings and cardiopulmonary exercise testing (CPET) results. Plans may vary according to local resources.

Fig. 30.1, A typical cardiopulmonary exercise testing (CPET)–based management plan for elective colorectal surgery. Example of how data from CPET as well as clinical information can lead to a rational approach to allocation of postoperative critical care. rCRI, Revised Cardiac Risk Index.

Preoperative interventions to reduce risk

Beta-blockade

The purpose of cardioselective β-blockade is to reduce risk of myocardial ischaemia after surgery through the prevention of tachycardia and the consequent decrease in myocardial oxygen demand and improvement in myocardial perfusion time.

Retrospective studies have found that the protective effect of β-blockade is greater in those patients who have an increased number of RCRI cardiac risk factors, and there is a suggestion that β-blockade in patients with no cardiac risk factors may be harmful.

Beta-blockers are now also widely used in the treatment of heart failure but have to be established over time for full effect, starting with a low dose. For patients established on long-term β-blockade, it is important that this is continued around the time of surgery as sudden cessation is definitely associated with a worse outcome. Parenteral preparations of atenolol or metoprolol are available for the patient who is nil by mouth; there is some suggestion that the longer-acting atenolol may be more beneficial.

Statin therapy

Many patients are established on long-term statin therapy as part of secondary prevention of cardiovascular disease. If so, it is important that this treatment is continued around the time of surgery as withdrawal can cause a rebound effect.

Long-term statin use has been found to reduce mortality risk after surgery in patients undergoing aortic surgery. Although more evidence is required, introducing statins before surgery may have some beneficial effect, possibly through their anti-inflammatory actions, and is unlikely to cause harm as side effects are rare. There are no parenteral preparations for statins, but it may be useful to use a longer-acting preparation such as fluvastatin, taken on the morning of surgery.

Coronary revascularisation

For patients with new-onset or unstable angina, or severe exercise limitation accompanied with ischaemia, evaluation by a cardiologist is required. These patients are at risk of major adverse cardiac events (see Chapter 20 ) irrespective of their surgical disease but in practice constitute a small proportion of patients presenting for surgery.

A much larger number of patients are asymptomatic but have cardiac risk factors, in whom coronary lesions can be identified on angiography. Prophylactic revascularisation of such lesions before non-cardiac surgery has no benefit in terms of overall outcome when the morbidity associated with the revascularisation is included.

Surgery may be complicated further in patients who have undergone percutaneous coronary intervention (PCI) with stenting as they will need to be taking dual antiplatelet therapy for a minimum of 6 weeks in the case of bare metal stents and 12 months for drug-eluting stents. In the case of patients who are known to require surgery after their PCI, a bare metal stent should be used to minimise the duration of dual antiplatelet therapy (see Chapter 20 ).

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