Cardiovascular
Hypertension needs to be controlled, ideally for 2 months before an anaesthetic. General or spinal/epidural anaesthesia in a patient with untreated hypertension can lead to very unstable blood pressure, very low as well as very high with a risk of intracerebral ischaemia, bleeding as well as myocardial infarction in patients with coronaropathy.
Patients with a recent Myocardial Infarction (less than 6 months) have a high risk (up to 25%) of having a secondary MI during or in the days following a surgery. Therefore only lifesaving surgery can be performed during that period.
Patients with coronary stents and on Clopidrogel: There are no clear consensus guidelines on the management of those patients. The main issue is the risk of severe bleeding if the medication is left, versus the risk of stent occlusion if the medication is discontinued. The current protocol is:
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to avoid any non-lifesaving surgery within 6 weeks of the stent insertion
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to stop Clopidrogel for the surgery if the patient has a bare metal stent
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to proceed with surgery under Clopidrogel in the patients with the new, drug-eluting stent
Pace makers: they might develop a malfunction by electrical interference with the theatre equipment. It is therefore important for the anaesthetist to know what model it is, the programmed mode and the cause of insertion.
They also need to be checked postoperatively.
Patients with cardiac valvulopathies pose complex problems. Especially, we see many elderly patients for emergency procedures with a murmur suggesting an aortic stenosis. Spinal/epidural anaesthesia are not recommended in those patients as they often induce deep hypotension. Safe general anaesthesia is difficult to achieve for the same reason.
Some cardiovascular medications have significant interactions with anaesthetics.
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ACE inhibitors often induce a deep hypotension under general anaesthesia. However, the decision to stop preoperatively them depends on the patient’s condition
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Diuretics often make patients slightly hypovolaemic, which also induces perioperative hypotension
Ventilation
In the immediate postoperative period, patient’s ventilation is impaired by:
This state is worsened by abdominal surgery and morbid obesity.
Therefore a patient with a “borderline” respiratory function can develop a full-blown decompensation postoperatively. It is not always predictable which patient will decompensate, especially among obese patients.
Spinal/Epidural anesthesia can also alter ventilation if the patient relies heavily on his intercostals and abdominal muscles for breathing.
Bronchospasm/Laryngospasm
They typically occur in patients with recent ENT infection, especially children. In adults, asthmatics and smokers are especially prone to those accidents.
Neck problems
Patients with neck abnormality (previous surgery, arthritis, radiotherapy, goiter etc) can be very difficult to intubate or even ventilate with a facemask with a risk of hypoxia.
Patients with neck instability like some patients with rheumatoid arthritis have a risk of spinal cord compression during the laryngoscopy and the positioning on the operating table.
Reflux/Hiatus Hernia
The risk is a pulmonary aspiration during a general anaesthetic.
Fasting
The risk is a pulmonary aspiration of the gastric content during a general anaesthetic, with a possibly fatal acute respiratory distress. It is usually admitted that solid food and opaque, particulated fluids clear the stomach after 6h, while clear fluids clear the stomach only after 2h. Hence the rules for preoperative fasting:
In pregnant women, the gastric emptying is delayed in an impredictable way, hence pregnant >3months patients are always considered as having a “full stomach”. In emergency situations, special techniques are used to minimise that risk.
Diabetes
Patient with diabetic disautonomy are especially prone to cardiovascular instability during anaesthesia. They might also be difficult to intubate, have an undiagnosed reflux and delayed gastric emptying. They are also at risk of having an undiagnosed myocardial ischaemia.
Preoperative fasting in a patient with type 1 diabetes is typically managed with an infusion of glucose and insulin with careful monitoring.
Glucose control might be difficult in the pre-per and postoperative period.
Morbid Obesity (BMI>30)
Those patients might pose technical problems for positioning on the operative table and in the trolleys/beds, as well as IV cannulation and spinal/epidural/regional blocks. The are especially prone to ventilation and airway control problems not only during the general anaesthetic, but also during the recovery period.
Drug Interactions
Apart from the cardiovascular medication cited earlier, the most common drugs interacting with general anaesthetics are:
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All sedative drugs (delayed recovery)
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Monoamine oxydase inhibitors (severe hypertension)
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Amphetamines (severe hypertension, seizures)
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Serotonine reuptake inhibitors (severe hypotension)
