Anaesthetics
Anaesthesia is rarely taught during general medical studies and remains 'mysterious' for most doctors. Many have misconceptions about different anaesthesia techniques, their feasibility and their risks. However, the decision to refer a patient for surgery sometimes needs to take into account the specific risks of anaesthesia. Although in most patients the risk of an anaesthesia-related complication is very low, in some cases it might be so high that the benefits of the surgery need to be carefully weighed against the risks of anaesthesia.
It may also happen that a serious condition is discovered during the anaesthetic preassessment and the whole management of the patient needs to be reviewed.
We would be very happy to discuss the case of individual patients with you. Please contact the Anaesthetic Department on 020 8321 5824 to be forwarded to the appropriate anaesthetist.
General Issues about Anaesthesia
Schematically, general or spinal/epidural anaesthesia has a dramatic effect on cardiovascular, respiratory and CNS systems, with a possibility to completely overturn a fragile state of balance in sick patients. These effects persist for some time after the patient has woken up.
Most general anaesthetic techniques have a depressant effect not only on the CNS, but also directly on the cardiovascular and respiratory systems.
Spinal/epidural anaesthesia has mostly a cardiovascular effect, by blocking the sympathetic vascular tone below the block level. They can also affect ventilation by blocking chest and abdominal wall muscles. The opiates often used with the local anaesthetics can also induce sedation in some patients.
Generally, any severe condition affecting the cardiovascular, respiratory or central nervous systems might be worsened by an anaesthetic.
Awareness during General Anaesthesia
General Anaesthesia (GA) is not a natural sleep but a state of medically-induced unconsciousness. However, it seems that auditory signals are still processed unless the EEG is totally isoelectric, in which case the patient is at risk of greater cardiovascular instability. Most patients appear to have some level of implicit auditory memorisation during a general anaesthetic, but do not consciously remember it. Alternatively, some patients experience very vivid dreams which they sometimes remember afterward.
Post GA confusion
Mental performance tests show that normal intellectual performance resume on average only 24-hours after a general anaesthetic. No data exist specifically on sedation. It is therefore recommended that patients rest during those 24-hours and avoid any possibly dangerous activity like driving cars, operating machines, cooking and DIY. Some patients develop a real state of confusion for a few hours or days. Elderly patients, patient taking psychiatric medication, illegal drugs or excessive alcohol are the most at risk of developing post anaesthesia confusion.
General Anaesthesia versus Spinal /Epidural
Although it might seem intuitively that a spinal or epidural anaesthesia is generally safer than a general anaesthesia, it has never been formally established. Therefore spinal/epidurals can be advocated on the ground of safety only in a selected number of patients.
Spinal / Epidural can be challenging or contre-indicated in patients with spine abnormalities or previous spine surgery.
They are contra-indicated in patients with clotting disorders or anticoagulant medication because of the risk of a compressive epidural haematoma and paraplegia.
Their use in patients on apirin or Clopidrogel has to be very carefully assessed.
Regional anaesthesia as the main anaesthetic technique for a procedure
-
Regional blocks need about 10-20 min to set to a surgical level
-
Their success rate depends on the level of experience of the anaesthetist and the equipment available (i.e. ultrasound guidance)
-
They might be technically difficult to perform, especially in obese patients and patients with neuropathies
-
In an anxious or confused patient they might require a level of sedation close to a general anaesthesia, combining the risks of the general anaesthesia with those of the regional block.
-
A spinal or epidural with a high level of block might be poorly tolerated in a severe COPD patient by blocking abdominal and lower thoracic muscles
-
They need specific postoperative monitoring
-
It is difficult to ask a patient to stay in the same position for more than 90min, especially in elderly arthritic patients, therefore only relatively short and predictable procedures can be performed under block only.
Specific Issues with Laparoscopic Surgery
Although laparoscopic surgery has less side effects than a laparotomy it does also affects breathing (because of the abdominal distension with gas) and might require a deeper level of anaesthesia and muscle paralysis. Laparoscopic surgeries tend also to take longer than their open equivalent.
Specific Issues with Some Rare Diseases
Some rare conditions induce very specific issues with general as well as regional anaesthesia.
If you plan to refer a patient with such condition for surgery, please mention it very clearly in your referal letter.
The most common of those conditions are:
- Myopathies (possible risk of Malignant Hyperthermia)
- Porphyria (severe metabolic disturbances)
- Hereditary Angioneurotic Oedema (severe facial oedema with risk of asphyxia)
