- Introduction:
Minimally depressed level of consciousness that retains the patient’s ability to independently and continuously maintain an airway and respond appropriately to physical stimulation or verbal command and that is produced by a pharmacological or non-pharmacological method or a combination.
- 2. Features:
- Retains the patient’s ability to maintain a patent airway independently and continuously
- Permits appropriate response by the patient to physical stimulation or verbal command
- Maintains protective reflexes.
- Different routes of administration:
- IV route: deep conscious sedation
IV sedation are more effective than the same drugs taken orally
Advantage: surgeon or anaesthesiologist has complete control of the entire procedure
Disadvantage: profound amnesia
Entral/oral route: sedation dentistry
- All body functions remain normal and the person is able to breathe on their own.
- The patient will often fall asleep. Some degree of amnesia is common.
- The disadvantage with this method of sedation is that the level of sedation for each person is not predictable
- Inhalation conscious sedation : nitrous oxide/ oxygen sedation also known as ‘laughing gas’
- This is the most frequently used sedation method in dentistry.
- All bodily functions remain normal.
- Clinical effects:
- For 20–30 min acute detachment and later a state of relaxation.
- Anterograde amnesia (loss of memory following administration of the drug) for the same period.
- Cardiovascular depression is minimal (the relative hypotension and bradycardia due to the relief of hypertension and tachycardia caused by anxiety).
- In most cases, minimal respiratory depression is seen. The exception is in patients with impaired respiratory function or in those who have taken other depressants such as opiates, alcohol, where the effect may be more marked. However, excessively rapid intravenous injections have the potential to cause respiratory depression leading to apnoea and respiratory arrest, which is life-threatening if not diagnosed and treated promptly.
- Additional properties of benzodiazepines:
- Muscle relaxant
- Anticonvulsant (used to treat status epilepticus).
- Objectives:
- To allay apprehension, anxiety or fear
- To decrease stress associated with traumatic or prolonged procedures
- To control gagging
- To stabilise the blood pressure for patients with hypertension or history of cardiovascular disease.
- Commonly used pharmacological agents:
Benzodiazepines:
- Antianxiety
- anticonvulsant,
- sedative,
- muscle relaxant
- amnesic properties.
Midazolam and diazepam are the medications used in the dental operating set-up.
Midazolam:
Midazolam is a short acting benzodiazepine CNS depressant.
Indication: short diagnostic and surgical procedure
Properties:
- Water soluble
- Nonirritating to veins
- Faster and shorter acting
- Three times more potent than diazepam
- It may be administered IV, IM, PO, rectally or nasally. The most common route of Midazolam is IV.
- Sedative agent that should be administered slowly over 2 min for a single large bolus dose. Rapid or excessive IV doses may result in respiratory depression or arrest. If not recognised and treated promptly, death or hypoxic encephalopathy may result.
- The initial IV dose may be as little as 0.5–1.0 mg.
- Onset of sedation after IV injection is achieved within 3–5 min.
- The duration of effect ranges from 1 to 6.
- The half-life ranges from 1.2 to 12.3 h.
Adverse effect:
- Hiccups
- Nausea
- Vomiting
- Headache
- coughing and pain at the injection site
Diazepam:
- Indicated for conscious sedation prior to short diagnostic or surgical procedures, either alone or with a narcotic.
- It may be administered IV, IM or PO, although IM administration is very painful and hence not recommended.
- It cannot be mixed with other medications or diluted as it carries the risk of precipitation.
Adverse effect:
- Extremely irritating to the tissues
- Venous thrombosis
- Phlebitis
- Apnoea
- Hypotension
- Diazepam can be given orally as a premedication prior to many nonpainful surgical procedures.
- Effective anxiolytic.
Fentanyl:
- Fentanyl is a synthetic opioid. It is indicated for analgesic action short duration procedures.
- If given alone, dosage should begin at 1–2 μg/kg, which is about 75–150 μg for an average size adult.
- Fentanyl has an immediate response and effective excellent analgesia.
- It has a half-life of 2–4 h .
- Rapid IV administration can lead to a rigid chest wall and difficulty in
breathing. This effect may be reversed with naloxone (Narcan)
Dose: 2-4mg/kg
- Fentanyl is used effectively as sedation, adjunct to regional/local
anaesthetics.
- Combined with benzodiazepines, it can obviate the need for inhaled anaesthetics for diagnostic, endoscopic, angiographic and other minor procedures in poor risk patients, as well as for burn dressing.
Ketamine: Dissociative anasthesia
- Ketamine is a nonbarbiturate hypnotic with very high margin of safety. It has good tissue compatibility (no irritation to veins).
- Profound analgesia, immobility, amnesia with light sleep and feelings of dissociation from one’s own body.
DOSE: A dose of 1–3 mg/kg IV (average 1.5 mg/kg) or 6.5–13 mg/kg IM (average 10 mg/kg).
- Ketamine produces the above effects within a minute and recovery start after 10–15 min, but patient remains amnesic for 1–2 h.
- Ketamine is effective for short procedures as operations on head and neck especially in asthmatics.
- It is also useful for repeated use particularly for burn dressings
- Combined with diazepam, it is useful in angiography, cardiac catheterisation and trauma surgery.
Disadvantage:
- Increased intracranial and intraocular pressure with increased occurrence of nausea and vomiting.
Propofol:
- It is the recent IV anaesthetic agent, used for induction/maintenance of anaesthesia.
- Major advantage of propofol is rapid recovery irrespective of the duration of infusion.
Dose
1–2 mg/kg/min (for sedation)
• Possess significant antiemetic property at low doses
• Rapid recovery without hangover effect
• Full orientation returns within 5–10 min
