What Is the Difference Between Sedation and General Anesthesia?

Sedation is medically induced temporary depression of consciousness prior to procedures that cause pain or discomfort to patients. Pain relieving medications (analgesics) are also usually administered as an adjunct to sedation.

Sedation and general anesthesia are different levels in a spectrum of consciousness. A person is fully conscious at one end of the spectrum where there is no sedation, and totally unconscious with general anesthesia. In between, the patient experiences various levels of consciousness based on the medication dosage.

Following are the different levels of sedation:

• Minimal sedation: The patient feels drowsy and relaxed, with minimal effects on bodily sensations.
• Moderate sedation: Moderate sedation is also known as conscious sedation and/or procedural sedation. The patient is semi-conscious, can breathe on their own and respond to stimulation.
• Dissociation: A type of moderate sedation with similar effects, produced by certain drugs which prevent the brain’s higher centers from receiving the sensory stimuli. The patient is dissociated from the surroundings but responds to stimulation.
• Deep sedation: The patient is nearly unconscious and only has purposeful response to repeated and painful stimulation. The patient may need assistance with breathing, but cardiovascular function is usually unimpaired.
• General anesthesia: The patient is completely unconscious and does not respond to any level of pain. The patient will require breathing assistance and cardiovascular function may be impaired.

Commonly used sedative and analgesic medication include the following:

Benzodiazepines

Benzodiazepines have an inhibitory effect on the central nervous system and produces sedation and relieves anxiety (anxiolysis). Benzodiazepines also have anticonvulsant and amnesic properties, but lack analgesic effects.

Benzodiazepines include:

• Midazolam: Rapid onset and short-acting, ideal for minimal and moderate sedation.
• Lorazepam: Can be used as continuous drip for longer duration of sedation. Useful for patients with kidney or liver problems.
• Diazepam: Long-acting and used for longer procedures. Not recommended for use in patients with liver cirrhosis.

Side effects include:

• Respiratory depression leading to low oxygen saturation
• Cardiovascular depression leading to low blood pressure (hypotension) and an increase in heart rate in response (reflex tachycardia)

Barbiturates

Barbiturates are potent sedatives with rapid onset and short duration of effects. Barbiturates are commonly used for endotracheal intubation and emergency sedation. Barbiturates are used along with an analgesic medication because they do not have analgesic effects.

Commonly used barbiturates are:

• Methohexital
• Thiopental

Side effects include:

• Respiratory depression
• Hypotension
• Reflex tachycardia

Nonbarbiturate sedatives

Nonbarbiturate sedatives are medications derived from certain other compounds which have potent sedative properties like barbiturates. These sedatives have a rapid onset and very short duration of action, ideal for deep sedation during short procedures, in combination with analgesics.

Nonbarbiturate sedatives include:

• Propofol: Causes hypotension and low heart rate. Contraindicated in patients with soybean or egg allergies.
• Etomidate: May cause involuntary muscle twitch (myoclonus) and brief adrenal gland suppression, but negligible cardiovascular effects.

Opioids

Opioids are primarily analgesic medications that also produce anxiolysis and mild sedation, but no amnesia. They are usually administered in combination with benzodiazepines.

Opioids include:

• Morphine: Rapid onset and long duration of action. Can cause hypotension and respiratory depression.
• Fentanyl: Rapid onset and short duration of effects. Can cause respiratory depression.
• Meperidine: Has intermediate duration of effects and rarely used for procedural sedation. Can lower seizure threshold.

Nonopioid analgesic

The nonopioid analgesic commonly used is a dissociative anesthetic with a short duration of action:

Ketamine: Ketamine makes the patient unaware of the surroundings but does not affect breathing. Ketamine with propofol, known as ‘ketofol’ is favored combination for procedural sedation.

Side effects include:

• Laryngeal spasms
• Delirium and hallucinations in patients older than 15
• Excessive bronchial secretions and salivation
• Hypertension and increased heart rate (tachycardia)
• Increased intracranial pressure

Inhalation agents

The inhalation agent that has been commonly used for years, for sedation and analgesia, especially in pediatric dentistry is:

• Nitrous oxide: Rapid onset and short duration of action. Useful for minor procedures. May cause nausea and vomiting.

Dexmedetomidine

Dexmedetomidine is a hypnotic sedative that acts on the central nervous system, producing sedation, anxiolysis, hypnosis and analgesia. It reduces the requirement for opioids. It has a rapid onset and ultra-short duration of action. It has light sedative effects and does not depress respiration. It is used in:

• ICU sedation: For patients under mechanical ventilation, with continuous infusion until they come off the ventilator.
• Procedural sedation: For minor procedures that require patient response to verbal or physical stimuli.

Side effects include:

• Hypotension
• Slow heartbeat (bradycardia)

Reverse sedation is the reversal of the effects of anesthetic drugs after completion of the procedure. Reversal of sedation may also be required if a patient has adverse reactions to the sedative agent or if the level of anesthesia gets deeper than intended due to some reason.

The two reversal agents available are:

Naloxone

Naloxone reverses the effects of opioid anesthetic agents.

Risks include:

• Rebound sedation
• Withdrawal symptoms in patients with chronic opioid use

Flumazenil

Flumazenil reverses the effects of benzodiazepines.

Risks include

• Rebound sedation
• Withdrawal symptoms in patients with chronic benzodiazepine use
• Precipitation of seizures that do not respond to benzodiazepines