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Clinical signs

Created: 18/7/2005
 
The most commonly used scoring system incorporates the PRST or Evan’s score.

This assesses autonomic activity related to P (systolic blood pressure), R (heart rate), S (sweating) and T (tears). Each parameter is given a score from 0 to 2, and these are totalled. This system has the advantages of being simple and not requiring any specialised equipment, but the parameters are not specific for the effects of anaesthesia and the values can vary widely among individuals. The scores range from 0 to 8, but the midpoint is seldom exceeded, reflecting the inadequacy of this scoring system.

In the spontaneously breathing patient who is not paralysed, awareness may be manifest by purposeful movement. Movement is a reliable indicator of light anaesthesia, although the patient may have no recall.

It is vital to continuously monitor patients' autonomic and respiratory parameters during anaesthesia. Measurement of heart rate and blood pressure while regularly assessing pupil size, and the presence of sweating and lacrimation, provide useful information regarding the adequacy of analgesia and depth of anaesthesia. However, they must be taken into context with the surgical procedure and the anaesthetic technique, as cardiovascular parameters alone are poor predictors of the hypnotic state. Tachycardia secondary to anticholinergic drugs such as atropine make the heart rate uninterpretable, and beta-adrenergic blocking drugs, opiates and regional anaesthetic techniques will obtund the sympathetic nervous system response to pain. Case reports have described cases of explicit awareness during anaesthesia, evident on electroencephalographic monitoring minutes before any significant cardiovascular changes have occurred.

ArticleDate:20050718
SiteSection: Article
 
   
    
                                            
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