Sedation and pain relief

Sedation and powerful painkillers can be used with or without local anaesthetic to make procedures more comfortable. 

In general terms there are three forms of sedation which are commonly used.  Pre-meds, sedation by injection and Entonox.


Pre-medication may be advised by your anaesthetist prior to your surgery.  Drugs given before your operation and reduce your bodies reaction to surgery by reducing your bodies sense of pain.  Even if you have had a general anaesthetic and so you are un-aware of your surgery your body can still register the pain of surgery.  This can be reduced by using Local Anaesthetic and pre-operative pain killers usually given by mouth.  Your pre-medication might also include some light sedative to reduce your anxiety prior to your operation.

Sedation by Injection

Sedation by injection is commonly used during Endoscopy along with local-anaesthetic throat spray.  This allows the examination to be perfomed without distress and often with little recollection of the examinaiton.  The common side effects of sedation are amnesia, drowsyness for up to 24 hours and occasionally patients report a feeling of depression and lethergy for the 24 hours after the procedure.  Many patients however, who may have had many procedures report that the sedation by injuction leaves them with very little by way of side effects, makes the procedure quite acceptable and they are happy to have further procedures under the same sedation.

The most common side effects of sedation by injection are related to a sudden fall in blood pressure and a reduction rate of breathing.  Because of this patients having sedation by injection have constant measurement of the saturation of oxygen in their blood, their blood pressure and their ECG.  Over sedation is now a very rare occurance however should it occur drugs are administered to revers the effect of the sedation and analgesia.  


Entonox is a mixture of Nitrous Oxide and Oxygen which is inhaled to to produce sedation.  It is very effective being most commonly used during childbirth.  In recent years Entonox has been used much more commonly during Colonoscopy.  I began asking my patients to try using Entonox during colonoscopy having read a number of publications reporting that many patietns preferred this to Sedation by Injection.  The Entonox is self administered by the patient using a mouthpiece very like a Scuba Divers mouthpiece.  It takes about 2 minutes of inhalation to begin to work and the patietn continues to inhale the gas, as much or as little as they feel they need throughout the investigation.  Entonox gives very good pain relief and is a mild sedative, however if patients use the gas properly for long enough they can make themselves quite sleepy.  Over breathing the gas does not deepen the sedation but can cause cramps in the fingers and hands because of Hyperventilation.  Entonox is very very safe and does not cause problems with low blood pressure and slow breating which can occur with Sedation by Injection.  Many patients who have used Entonox tell me that they found the procedure more satisfactory, felt more in control and could remember much more of what we discussed following the procedure.  For these reason most patients now choose Entonox for their sedation.

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