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Types of Anaesthesia

There's a downloadable resource for this week (the link is below)

Last week, we learnt that anaesthesia referred to the loss of sensations in a part of or the whole body. This week, we’re looking at the different types of anaesthesia. The type of anaesthesia will be chosen based on the patient’s needs, the procedure being performed, the positioning required & the anaesthetist’s preferences or skill level.

 

Local Anaesthesia

This type of anaesthesia when administered alone will render a particular area of the body anaesthetised such as a part of a finger or toe. The patient will not require an airway to maintain their breathing & may not even require any patient monitoring depending on your organisation’s policy.


Patients requiring local anaesthesia may not be required to attend an operating suite which saves the patient time, money &, to a certain extent, anxiety. Patients can also return to normal activities immediately following the procedure.


When local anaesthesia is combined with general anaesthesia, it allows for enhanced pain relief following the procedure. This generally means that the patient will not require large doses of analgesia intraoperatively & could lead to additional pain relief not being required in recovery &/or only a small amount on discharge.


There are also limited side effects noted making it quite safe for all patients. If there were an inadvertent venous administration of local anaesthesia, the biggest risk for patients is called local anaesthetic systemic toxicity [LAST].

 

Regional Anaesthesia

Regional anaesthesia involves a higher dose of local anaesthetic to a larger area of the body such as an entire limb. Epidurals & spinal anaesthetics are also included in this type of anaesthesia. They are also known as central neuraxial blockades, major regional anaesthetics & you will also hear this type of anaesthetic referred to as ‘blocks.’


You may have heard different names of blocks & the names are in relation to what area is being blocked. You may have heard of periorbital, TAP, interscalene, femoral nerve or caudal blocks (or maybe you haven’t so some further reading might be needed!). Ultrasound is commonly used to place these blocks to ensure correct placement.


Regional anaesthesia can be combined with general anaesthesia to provide superior pain relief postoperatively. As with local anaesthesia administration, the patient usually requires less additional analgesia postoperatively leading to earlier ambulation & general comfort for the patient.


The risk of local anaesthetic systemic toxicity [LAST] is much higher with this type of anaesthesia due to the increased amount of local anaesthesia administered. Epidurals & spinal blocks carry their own complications as well given the location of the drugs to the spinal column & major nerves. All major regional anaesthetics can cause short or long-term nerve damage however this risk is quite low.

 

Sedation


Sedation can be used alone & usually involves the administration of agents such as midazolam &/or propofol to calm the patient. The patient is generally still able to obey commands to a degree & may be administered in conjunction with a regional anaesthetic block such as during a knee replacement. Monitoring is required & at times supplemental oxygen may be required due to the respiratory depression caused by these medications. Patients will need time to recover from this anaesthetic.



As mentioned above, the agents administered during sedation cases cause respiratory depression. This type of anaesthesia carries airway risks as a result if dosing & monitoring is not assessed accurately. For some patients, there is a fine line between a case being a sedation anaesthetic & a general anaesthetic as dosing can be delicate.


This is the type of anaesthesia that Nurse Sedationists here in Australia are accredited to administer. You may be asked by the Proceduralist as a Registered (Div 1) or Medication Endorsed Enrolled Nurse (Div 2) to administer sedative agents intravenously in Interventional Radiology or Cardiac Catheterisation Labs.

 

General Anaesthesia

General anaesthesia [also known as a GA] renders the patient unconscious. This is where the whole body is anaesthetised & as a result, the patient may not be able to maintain their own airway. This means the patient will require an artificial airway in order to maintain gas exchange. The medications administered can also cause decreases in blood pressure which can compromise patients. As a result of the compromises caused by a GA, the patient must recover for a minimum period of time (usually 30mins) to ensure there are no immediate complications present.


This type of anaesthesia can be requested by the patient or surgeon or as suggested by the anaesthetist given the type of procedure. The medications required to administer a GA include inhalational or intravenous induction agents, maintenance agents (which are usually the same as induction), analgesia & antiemetics. Each anaesthetist will have their own preference as to which agents to administer (or their fave cocktail) however it is also patient based. We will explore some of the patient related factors next week.


Seemingly, the more agents you administer, the higher the risk would be. The risks associated with a GA include cardiovascular & respiratory compromise along with anaphylaxis.

 

Muscle Relaxant General Anaesthesia

This type of anaesthesia involves the administration of a muscle relaxant which renders the patient unconscious & absolutely unable to maintain their own airway & breathing. This is required for the procedure to be performed such as spinal or heart surgery. The positioning required for the procedure can also lead to the need for this type of anaesthesia. As with a standard GA, the patient will require a stay in the post anaesthetic care unit to monitor & assess for any potential complications.


Muscle relaxant GA’s carry the most risk as they have the highest chance of the airway emergency – can’t intubate, can’t oxygenate along with anaphylaxis. The most commonly used muscle relaxant, Rocuronium, produces the highest incidence of anaphylaxis cases in the perioperative setting in most countries (Volcheck & Hepner, 2019).


 

Over the next 2 weeks, we will explore the patient factors that can impact anaesthesia via preoperative assessment. The importance of & opportunities created by preop assessment will be reviewed along with the assessment tools used.


I promised a downloadable resource for you to extend your learning & as something tangible for your CPD record - you can find it here (http://bit.ly/388Xy25)

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