7 Reasons Why Conscious Sedation with Midazolam is Sometimes Unsuccessful

While Midazolam sedation is on the whole, a very successful and safe technique for the majority of patients, there are a small minority of cases where either the technique is either unsuitable or unsuccessful...

Midazolam has been the drug of choice in dentistry when providing sedation since it was introduced in 1983. It is a water soluble benzodiazepine that produces amnesia, sedation and muscle relaxation. It has a rapid action and short half life, with recovery usually being within 8 hours. 

IV midazolam is a basic sedation technique. Dentists who have been trained and signed off on an accredited course can provide this technique in managing patients (IACSD 2015). There are several indications this technique can be used for patients, such as:

  • Dental anxiety
  • Unpleasant dental procedures
  • Hypersensitive gag reflexes
  • For muscle relaxation e.g. patients with movement disorders, limited mouth opening 
  • Co-operation e.g. learning disabilities, cognitive disorders 
In a large number of patients, this form of sedation can be a very effective way of managing dental treatment, but in some cases, it can be unsuccessful. 

Causes of Unsuccessful Midazolam Sedation

1. Oversedation

Midazolam is a respiratory depressant. If too much is delivered, or a patient is particularly sensitive to the drug, then oversedation can occur. 

Conscious sedation is defined as... 'a technique in which the use of a drug(s) produces a state of depression of the central nervous system enabling treatment to be carried out, but during which verbal contact with the patient is maintained throughout the period of sedation'

If this contact is lost, this can be dangerous as the airway may not be maintained and will result in a drop in oxygen saturations. If these are consistently below 90% and do not respond to rousing the patient, airway manoeuvres or supplemental oxygen, then the patient should be reversed with flumazenil

Patients who are susceptible to this are patients with existing comorbidities e.g. respiratory conditions such as asthma or COPD, or older patients. Thorough pre-assessment should identify these patients and either alternative methods explored, or a reduced titration regime, for example: 

  1. 1mg is injected over 30 seconds.
  2. Pause for four minutes. 
  3. Additional 0.5mg increments are given every two minutes until sedation is adequate.

2. Undersedation

Sedation can fail if the patient is under sedated and they remain too anxious or cooperative for treatment to commence. This could be because not enough midazolam is delivered, or patients do not react well to the sedation or ‘fight it’. 

3. Paradoxical Effects

Instead of the patient becoming sedated when midazolam is delivered, a patient can become disinhibited instead, become disruptive or aggressive. 

4. Lack of a Sufficient Window

Usually, a typical ‘window’ of optimum time for dental treatment under midazolam is 30-40 minutes, but this varies per person. In some patients, treatment windows are too short to be able to provide sufficient dental treatment before the sedation wears off, or the dentist is not efficient enough to provide the treatment required. 

5. Allergy to Midazolam

True allergy to midazolam is very rare. Any alleged allergy should be confirmed patch testing. An allergic reaction with midazolam should not be reversed with flumazenil which is another benzodiazepine, but treated with emergency adrenaline and immediate call for help from a crash team or ambulance. 

6. Lack of a Suitable Escort

When providing IV sedation, the patient must arrive with their suitable escort. If there isn’t a suitable escort, then IV sedation cannot be carried out. 

7. Lack of Cooperation

IV midazolam can fail as a result of lack of cooperation from a patient to be able to achieve cannulation. Although oral or intra-nasal sedation can be used to help relax a patient to allow for cannulation, sometimes even with clinical holding this fails especially if the patient has particularly challenging behaviour.

If any of these reasons occur, we need to consider other modalities of treatment, for example Local anaesthetic, Inhalation Sedation, Advanced Sedation Techniques or even General Anaesthesia. 

Have any of these reasons happened with your patients? Please leave your experiences in the comments below

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