Conscious sedation (2 hours)

Overview

Sedation in dentistry has been a contentious topic due to concerns about its safety, particularly in the dental chair. Due to the high intensity of pain, dental fear and anxiety are not only common in children but also significantly prevalent in adults. The most difficult challenge is sharing the airway between the anesthesiologist and the dentist. The goal of this review is to look at recent trends in conscious sedation in dentistry from the perspective of an anesthesiologist. It will provide a practical overview of the drugs' or gasses' pharmacokinetics, pharmacodynamics, and routes of administration.

 

What is Conscious Sedation in Dentistry?

Conscious sedation is a procedure in which the administration of a medicine or combination of pharmaceuticals results in a state of central nervous system (CNS) depression that permits the administration of treatment, but during which verbal communication with the patient is maintained throughout the sedation. Conscious sedation for dental procedures should be possible using medications and methods with a margin of safety that makes unconsciousness unlikely. The patient can continue to autonomously maintain a patent airway while under conscious sedation.

When under the effects of a medicine, a person experiences conscious sedation, during which time they are less conscious but nevertheless respond to verbal directions and light tactile stimuli. There is no need for measures to keep the airway open, and spontaneous ventilation is sufficient. Typically, cardiovascular health is preserved.

Presedation evaluation must be done carefully, taking into account the airway, fasting, and knowledge of the pharmacodynamics and pharmacokinetics of the medications. Airway management tools, venous access, suitable intraoperative monitoring, and properly trained workers in the recovery room must all be available.

There are several ways to provide conscious sedation, including orally, intramuscularly, intravenously, and inhalationally.

 

Challenges in Dental Conscious Sedation

The following are the difficulties with dentistry conscious sedation:

• shared airway between the anesthesiologist and the dentist
• Anxiety and phobias
• co-occurring diseases include epilepsy, mental instability, and cardiac abnormalities
• Arrhythmia risks associated with trigeminal nerve stimulation during surgery
• Children with enlarged tonsils and adenoids are more likely to develop respiratory obstruction.
• The possibility of the patient passing out, developing respiratory and cardiovascular depression
• Vasovagal syncope brought on by the legs' reliant posture in the dental chair.

The anesthesiologist should be well-equipped to meet and overcome all of the aforementioned problems. It is necessary to perform a full and in-depth pre-departure checkup that includes an evaluation of the airway, cardiorespiratory system, any congenital anomalies, medication history, and allergies.

In case of an emergency, the operating room should be fully stocked with all necessary resuscitation supplies and tools.

 

Indications for Conscious Sedation

1. Dental anxiety and phobia.
2. Long and traumatic dental procedures.
3. Angina, asthma, and epilepsy are a few health issues that are made worse by stress.
4. Children older than 1-year-old with mental disabilities.
5. Any explanation why local anesthetic wasn't effective?

 

Preparation for Conscious Sedation

Patients must be ready for conscious sedation, and the operating room must be ready to handle any unforeseen difficulties.

Patient preparation

• Consent for treatment: All patients getting dental treatments under conscious sedation must provide valid informed permission, which should be documented in writing. When it comes to youngsters, the legal guardian must sign any legitimate consent.
• Pre-sedation checkup: A thorough history and physical are taken of the patient in order to categorize them using the American Society of Anesthesiologists (ASA) system. For sedation in dental surgery performed outside of a hospital, only patients who meet the requirements of ASA Grade I and II should be taken into consideration.Only ASA Grade I patients should be sedated outside of a hospital setting. For juvenile patients, a thorough airway examination is performed to check for adenotonsillar hypertrophy or any other anatomical airway anomalies. Prior to beginning the patient's dental procedure, the concerned specialist should be consulted for advice in the event of any underlying medical or surgical conditions.
• Fasting instructions: Preoperative fasting for sedation is debatable and is not recommended for conscious sedation, according to certain dental authority. It is believed that both moderate and slight sedation maintains airway reflexes. Where the reflexes start to fail is not quite understood. One cannot completely rule out the possibility of unintentional oversedation and eventual loss of protective airway reflexes.

The 2-4-6 fasting guideline is applicable for elective procedures requiring conscious sedation (that is 2 h for clear fluids, 4 h for breast milk, and 6 h for solids.). The advantages of therapy and the risks of the lightest level of effective sedation might be compared for emergency procedures where fasting cannot be guaranteed. The patient may benefit from postponing the operation.

 

Operating setup

The clinic needs to have monitoring and resuscitation tools, as well as trained personnel, on hand to manage any emergency.

• Monitoring: Accessible and in good working order monitoring tools should include an ECG, a pulse oximeter, an ETCO2, an NIBP, and a defibrillator.
• There should be a crash cart with all the resuscitation tools and medications needed to revive a patient.
• After making sure there is enough supply of oxygen, functional flowmeters and tubing for the patient's oxygen administration, and the proper size airway equipment, every procedure should be carried out.

 

Drug Pharmacology for Conscious Sedation

Prior to giving any medication or inhalational anesthesia, an intravenous (IV) line must be established using an IV cannula of the proper size. Often, a mild anxiety medication combined with local anesthetic is enough to calm the patient's fears and anxieties.

 

Nitrous oxide

As a sedative, nitrous oxide (N2O) and oxygen are combined. A colorless gas called N2O is utilized as an anesthetic for inhalation. It is a combination analgesic/anxiolytic that has little to no impact on the respiratory system but depresses the central nervous system and generates different degrees of muscle relaxation and pleasure.

According to recent studies, the analgesic effects of N2O are first triggered by neuronal production of endogenous opioid peptides, which then activate opioid receptors, descending GABA and noradrenergic pathways, and spinal nociceptive processing. The stimulation of the GABAA receptor via the benzodiazepine-binding site has an anxiolytic effect. The inhibition of N-methyl-D-aspartate (NMDA) glutamate receptors, which eliminates their excitatory effect on the nervous system, is thought to be the mechanism behind the anesthetic effect.

The method uses nasal mask delivery of subanesthetic doses of N2O and oxygen through specialized equipment. When oxygen flow is interrupted, oxygen fail-safe devices included into the N2O/oxygen delivery systems cease the flow of N2O. The safety mechanism makes sure that there is always at least 30% oxygen delivered. Because N2O has a high minimum alveolar concentration and a low tissue solubility, it can act quickly and recover quickly, ensuring regulated sedation and a prompt return to daily activities. Due to the patient's continued awareness, responsiveness, and retention of reflexes, it is quite safe. Patients with the common cold, porphyria, and COPD should not take N2O.

 

Sevoflurane

Sevoflurane is a low-pungency, non-irritating odor, low blood-gas partition coefficient ether inhalation anesthetic. Due to its low solubility, it allows for fine control over sedation depth as well as quick and painless induction and recovery from sedation.

Therefore, to maintain sedation before beginning an IV complete anesthetic infusion such as propofol, sevoflurane continues to be a perfect induction agent.

Benzodiazepines

Benzodiazepines such as diazepam and midazolam have been shown to be both safe and effective for IV conscious sedation. Their sedative and selective anxiolytic effects, as well as their broad margin of safety, contribute to their widespread use in dentistry. Benzodiazepines are known to have skeletal muscle relaxation and anticonvulsant action in addition to anxiolysis and amnesia; nevertheless, these medications have no analgesic characteristics.

GABA-mediated chloride channel opening is the mechanism of action. They have a high lipid solubility, which results in a quick commencement of action. They are typically used with N2O/oxygen for conscious sedation because N2O generates analgesic effects.

Midazolam is the most often used benzodiazepine. Because of its high first-pass metabolism, it is a short-acting one. It is used in pediatric dentistry for conscious sedation. It is combined with a sweet carrier, such as simple syrup, and administered orally by drinking cup or needle-free syringe and deposited in the retromolar region. Syrup can be administered 20 minutes before the surgery. Adult dose under 25 kg is 0.3-0.5 mg/kg, but should only be provided in a hospital setting. It can be administered intramuscularly, intravenously, rectally, or nasally. Opioids, clonidine, antidepressants, antipsychotics, erythromycin, antihistaminic, alcohol, and antiepileptics all enhance its effects and should be avoided or taken with caution.

Flumazenil, the particular benzodiazepine receptor antagonist, must be one of the emergency medications available to all practitioners who use these treatments. All benzodiazepines are rapidly reversed by flumazenil. It is, however, contraindicated in people who are taking benzodiazepines for seizures or large doses of tricyclic antidepressants.

 

Ketamine

Ketamine, a phencyclidine derivative, is an NMDA receptor antagonist. It is a unique drug giving complete anesthesia and analgesia with preservation of vital brain stem functions. The term "dissociative" refers to a "functional and neurophysiological detachment between the neocortical and limbic systems." Dissociation, often known as "Catalepsy," is characterized by a lack of responsiveness to pain while maintaining circulatory and respiratory functioning despite extreme amnesia and analgesia. This trance-like sensory isolation condition gives a one-of-a-kind mix of forgetfulness, drowsiness, and analgesia.

Though nystagmus is widespread, the eyes frequently remain open. Heart rate and blood pressure stay steady and are often raised, probably via sympathomimetic effects. With bronchial smooth muscle relaxation and the preservation of airway patency and breathing, functional residual capacity and tidal volume are retained. The most prevalent side effect of ketamine is emergence, which happens in 5%-50% of adults and 0%-5% of children. Because ketamine increases salivary and tracheobronchial mucus gland secretions, it is best to utilize an ant sialagogue before taking it. The emetic adverse effect of ketamine, which causes vomiting in 10% of children, can be reduced by providing atropine, which decreases salivary flow. Positive pressure ventilation with 100% oxygen can be used to treat laryngospasm, which occurs in 0.4% of cases.

According to Green et al., ketamine can be administered intramuscularly at a dosage of 3-4 mg/kg or intravenously at a dose of 1-2 mg/kg. However, because to the risk of severe respiratory depression, taking a lower dose of the medicine may be safer in order to produce acceptable levels of sedation in youngsters.

 

Propofol

Propofol's chemical name is 2,6-diisopropylphenol. Because it is insoluble in water, it is available in a white, oil-in-water emulsion for IV administration of this fat-soluble substance. Propofol is easily oxidized to quinine, which makes the solution yellow after about 6 hours of air exposure. Propofol induces hypnosis by activating the central inhibitory neurotransmitter GABA. High lipophilicity provides an early initiation of action in the brain, and rapid redistribution from the central to the peripheral compartment results in a rapid offset of anesthetic activity.

The half-life of elimination is 2-24 hours. The greatest hemodynamic impact is a reduction in arterial blood pressure and heart rate. Sedatives have little or no effect on the respiratory system.

Apfel et al. investigated six strategies for the prevention of postoperative nausea and vomiting (PONV) and discovered that propofol usage decreased the risk of PONV by 19%. Sedative levels are not analgesic, and many patients suffer discomfort during injection. To avoid discomfort while administering propofol through an antecubital vein rather than a hand vein, lidocaine admixture is a simple and efficient method. To prevent the fight to establish IV access before the infant falls asleep, volatile anesthetic drugs are utilized to induce anesthesia. Propofol is commonly administered at a dosage of 1 mg/kg body weight with sevoflurane, followed by a maintenance dose ranging from 0.3 to 4 mg/kg/h.

 

Opioids

Except for ketamine, none of the medications listed above have analgesic properties. As a result, opioid analgesics must be supplemented. Fentanyl is a short-acting opioid that is 60-80 times more powerful than morphine and produces analgesia and drowsiness quickly.  The activity lasts 30-60 minutes. Fentanyl can be delivered intravenously, transdermally, nasally, or orally. A "lollipop" delivery strategy is preferred by youngsters over any other method. As a lipophilic medication, fentanyl is absorbed by the buccal mucosa, processed in the liver, and excreted in the urine. The recommended dose is 1 g/kg IV, which can be repeated in 1 g/kg increments if necessary. Common adverse effects include constipation, nausea, and vomiting. Rapid IV infusion is linked with dose-dependent respiratory depression, as well as bradycardia and chest wall stiffness.

 

Sufentanil

Sufentanil is a synthetic opioid analgesic that is 5-10 times more powerful than fentanyl and 500 times more potent than morphine. It has shorter half-lives in distribution and elimination. For outpatient surgery, IV sufentanil gives anesthesia comparable to isoflurane or fentanyl. Recovery is quick, and postoperative analgesia is not required. However, as compared to midazolam, it has less chest wall compliance, a higher incidence of nausea and vomiting, and a longer discharge time, making it an unattractive option for premedication.

 

Are there any side effects?

The following are some frequent adverse effects of conscious sedation that may linger for a few hours after the procedure:

• Drowsiness
• A sense of heaviness or sluggishness
• Memory loss of what occurred during the operation (amnesia)
• Sluggish reactions
• Blood pressure is too low
• Headache and nausea

 

What’s recovery like?

Conscious sedation recovery is rather rapid.

Here's what you may expect:

• It is possible that you will need to be in the procedure or operating room for up to an hour, if not longer. Typically, your doctor or dentist will monitor your heart rate, respiration, and blood pressure until they return to normal.
• Bring a family member or a friend who can drive you or pick you up. After some kinds of sedation, such as nitrous oxide, wear off, you should be able to drive. This isn't always the case with other varieties.
• Some adverse effects may linger throughout the day. Drowsiness, headaches, nausea, and sluggishness are some of the symptoms.
• Take a day off from work and avoid strenuous physical activity until the negative effects subside. This is especially important if you want to perform manual jobs requiring accuracy or handle heavy machines.

 

Conclusion

Conscious sedation is a treatment used to treat dental phobias and should not be used in place of appropriate local anesthetic or competent behavioral management. The route of administration and the medicine should be determined for each individual patient. The necessity of appropriately educated employees in an area well-equipped with surveillance instruments, as well as rigorous predation assessment, cannot be overstated. When using sedation in a dental context, it is important to be conscious of your restrictions.