Principles and Practice of Intravenous Sedation
Intravenous sedation is the technique of choice for most adult dental patients requiring conscious sedation. The administration of sedation agents via the intravenous (IV) route normally produces a predictable and reliable pharmacological effect. Intravenous sedation is more potent and quicker‐acting than inhalation or oral sedation and is particularly effective for very anxious or phobic dental patients and for difficult surgical procedures. It produces true pharmacological sedation rather than the psycho‐pharmacological sedation that is achieved with inhalation techniques.
The practice of IV sedation is technique‐sensitive; it requires the ability to perform IV cannulation, which can be a difficult technique to master. The dental clinician also has to be able to determine an appropriate end‐point for sedation and drug administration. The level of sedation needs to be sufficient to enable the patient to accept operative dentistry, but not so great as to present the risk of over‐sedation.
The aim of this chapter is to provide the theoretical basis from which sound clinical principles and skilled practical techniques can be developed in order to ensure the safe practice of IV midazolam sedation. It is essential that supervised hands‐on training and competency is achieved before applying these clinical techniques to patients.
Indications and Contraindications for Intravenous Sedation
- Moderate to severe dental anxiety
- Traumatic surgical procedures
- Gag reflex and swallow reflex are present
- Mild medical conditions which may be aggravated by the stress of dental treatment, for example mild hypertension or asthma
- Mild intellectual or physical disability, for example mild learning disability, cerebral palsy.
Intravenous sedation has an important role in the management of patients with severe systemic disease or moderate to severe disability, especially if it avoids the need for general anaesthesia. However, these patients do present a significant risk and IV sedation should only be undertaken in a specialist hospital environment.
- History of allergy to benzodiazepines
- Impaired renal or hepatic systems
- Pregnancy and breast feeding
- Severe psychiatric disease
- Drug dependency.
For people with severe needle phobia who are unable to accept any type of injection, inhalation, oral sedation or intranasal sedation may be acceptable alternatives. For these patients it is sometimes necessary to combine two techniques. Inhalation sedation (or even hypnosis) may be employed initially to relax the patient enough to allow venous cannulation; once the cannula has been inserted, the inhalation element of the sedation is switched off and the IV sedative can be administered.
The use of IV techniques is also, to some extent, limited in patients with poor veins. This includes patients with excessive sub‐cutaneous fat, whose veins are not visible, and the elderly who frequently have friable veins which are prone to damage during cannulation.
The use of IV sedation in children (under 16 years of age) should be approached with caution. Not only do children dislike needles but IV sedation agents can have an unpredictable effect. Children can lose their controlling inhibitions and become uncooperative so that, in the event of a complication, their condition can deteriorate very rapidly. Even slight over‐sedation can result in significant respiratory depression and airway obstruction. Intravenous sedation in those aged 12‐16 years should be undertaken by those with experience of paediatric sedation.
Drug Choice for Intravenous Sedation
Intravenous sedation agents should not only have the ability to depress the central nervous system to produce a state of conscious sedation, but they should also have a margin of safety wide enough to render the unintended loss of consciousness unlikely.
Modern IV sedation techniques depend almost exclusively on the benzodiazepines. Both midazolam and diazepam are suitable IV sedatives, although the pharmacokinetics of midazolam make this the preferred choice for dental sedation and the recommended drug of choice in the United Kingdom. Midazolam is presented in different concentrations: 5 mg/5 ml in a 5 ml ampoule, 2 mg/ml in a 5 ml ampoule and 5 mg/ml in a 2 ml ampoule. The 5 mg/5 ml formulation should be used for dental sedation as it is less concentrated and safer to titrate. Other IV agents are being used in secondary care settings by appropriately trained personnel. An example of this is propofol, a short‐acting anaesthetic drug administered via a continuous infusion or using patient‐controlled sedation techniques. It has an extremely rapid recovery period which is advantageous for ambulatory patients. Propofol is licensed in the United Kingdom for use as a general anaesthetic agent and is not yet licensed for use in dental sedation; the drug should, therefore, only be administered by an anaesthetist trained in dental sedation.
Clinical Effects of Sedation with Intravenous Midazolam
- Conscious sedation with acute detachment (lack of awareness of one’s surroundings) for a period of 20–30 minutes after administration, followed by a period of relaxation which may last for a further hour or more
- Anterograde amnesia, that is, loss of memory following administration of the drug
- Muscle relaxation (useful for those with cerebral palsy)
- Anticonvulsant action
- Slight cardiovascular and respiratory depression.
Advantages and Disadvantages of Intravenous Midazoalm
- Reasonably wide margin of safety between the end point of sedation and loss of consciousness or anaesthesia (although it is easy to induce sleep with moderate over‐dosage)
- A satisfactory level of sedation is attained pharmacologically rather than psychologically
- Recovery occurs within a reasonable period and the patient can usually be discharged home less than two hours following completion of treatment.
- May alter a patient’s perception and response to pain but it does not produce any clinically useful analgesia.
- For a short period after injection the laryngeal reflexes may be obtunded. Over‐dosage may result in profound respiratory depression, particularly in patients with impaired respiratory function or in those who have taken other depressants, such as alcohol.
- Excessively rapid IV injection can also cause significant respiratory depression and even apnoea.
- May occasionally produce disinhibition, so instead of becoming more relaxed, the patient becomes more anxious and difficult to manage.
Planning for Intravenous Sedation
Careful planning is essential before undertaking IV sedation in dental practice. Chapter 3 has already dealt with the selection and assessment of patients for sedation. The following section will specify the personnel and equipment required to practise IV sedation both safely and effectively.
Dental clinicians should not undertake sedation unless they have been appropriately trained. In the United Kingdom, this means that dentists should have received relevant postgraduate training. This involves completing a programme that provides both didactic and clinical training in recognised conscious sedation techniques. It is acceptable for an appropriately trained dental clinician to sedate the patient and provide dental treatment simultaneously. The dental clinician must be assisted by a dental nurse or other person who is appropriately trained in the field of conscious sedation. They must have knowledge of the sedation drugs and specialised equipment being used, be capable of monitoring the clinical condition of the patient and understand the relevance of blood pressure and oxygen saturation readings. It is also essential that all staff are trained to assist in the event of an emergency. The assisting dental nurse must be specifically trained in sedation and resuscitation techniques, as this is not part of the core training for dental nurses. For the assistant, the gold standard for training in the United Kingdom is the Certificate in Dental Sedation Nursing.
Equipment and Premises
The suitability of the dental surgery where sedation is provided needs to be assessed. Easy access and space for patients, staff and for the management of emergencies is required. There should be the facility to store sedation agents and other drugs in a locked drugs cupboard. The dental chair must have a fast‐recline mechanism so that in an emergency the patient can be quickly laid supine. There should be a high‐volume aspirator available (with emergency back‐up) which can be used to clear the oropharynx.
It is essential to monitor the patient’s clinical condition during sedation. The following equipment is required:
- Pulse oximeter: it is mandatory to continuously measure oxygen saturation and heart rate throughout the sedation procedure.
- Manual or automatic sphygmomanometer to monitor baseline blood pressure before sedation, at appropriate intervals during sedation and prior to the patient being discharged.
Emergency Equipment and Drugs:
Appropriate emergency equipment and drugs must also be available (detailed in Chapter 8). It is particularly important to have the facility to provide supplemental oxygen via a nasal cannula or a face‐mask and an additional device with which to give positive pressure ventilation. The emergency equipment required for sedation is identical to that which should be stocked in any dental practice; the only additional item required for undertaking benzodiazepine sedation is the reversal agent, flumazenil. This is presented as a clear liquid in 500 mcg ampoules.
Ideally there should be a separate recovery area where the patient can sit quietly and privately following sedation. A pulse oximeter and blood pressure monitor must be available as well as oxygen and suction apparatus. An alternative is to allow the patient to recover in the dental chair but this potentially utilises the chair for several hours and may not be possible in a busy dental practice.
Specific Sedation Equipment:
To administer IV sedation, the following equipment is required (Figure 7.1):
- 2 × disposable 5 ml graduated syringes
- 2 × 21 gauge hypodermic needles (preferably blunt)
- Surgical wipes
- Adhesive tape (or proprietary dressings)
- Indwelling teflonated 22‐gauge safety cannula.
A Teflon coated cannula provides more secure access and is unlikely to become dislodged or blocked during limb movement. A 22‐gauge safety cannula is the ideal size for administering IV sedatives. It readily allows the administration of modest volumes of drugs but is small enough not to cause too much discomfort on insertion.
Technique of Intravenous Sedation
The patient scheduled for IV sedation should have undergone a thorough pre‐operative assessment as described in Chapter 3. The availability of appropriate personnel and equipment should be checked before the start of each sedation session. It is helpful to use a pre‐procedural checklist, such as that illustrated in Figure 7.2, to ensure that all the necessary criteria required to practise sedation safely are confirmed before the start of the session.
Each item on the list should be checked and the appropriate box ticked. Equipment should not only be available but also in good working order. Gas cylinders, and particularly oxygen supplies, must be checked to ensure that they contain a sufficient volume of gas and are not low or empty. The expiry date on all drugs should be checked to ensure that they are still valid. All the equipment required for the session should be prepared and placed discreetly out of the patient’s line of vision.
Before the patient is brought into the surgery, the following information should be confirmed:
- Presence of suitable escort
- Appropriate transport home (car/taxi)
- Written consent obtained
- Medical history updated
- Routine medication taken
- Time of last meal and drink (minimum fasting time 2 hours)
- If alcohol has been taken (if consumed within the previous 24 hours, then treatment should be postponed)
- No use of recreational drugs in the last 48 hours
- Female of child bearing age is not pregnant.