Pharmacology - Chapter 5: Sedation and general anesthesia

•For about 10 minutes after the end of the anesthetic, nitrous oxide seeps out of the blood and enters the lungs. •This nitrous oxide occupies lung space normally available for oxygen, resulting in persistent diffusion hypoxia in the early stages of recovery. •To avoid diffusion hypoxia, give 100% O2 for at least 5 min at the end of the dental visit.

Diffusion hypoxia

Stage I

Stage of surgical anesthesia (Guedel classification) in which: -> Amnesia and analgesia: - Moderation sedation - Nitrous oxide produces stage I - Loss of pain, loss of general sensation, but still awake even though the patient does not know anything is happening: semiconscious - Reflexes intact

Stage II

Stage of surgical anesthesia (Guedel classification) in which: -> Excitement/delirium: - Loss of consciousness - Pt may resist treatment; involuntary muscle movement - Increase in blood pressure - Irregular respirations - IV agents may be used to calm the patient; loss of consciousness to onset of anesthesia - Patient may become incontinent.

+ add do not eat a full meal 3 hours prior to the appointment

Steps on Nitrogen administration

• Benzodiazepines such as diazepam (Valium, generics); midazolam (Versed) for its amnesia effect and reducing apprehension and fear • Narcotic analgesics such as fentanyl (Sublimaze, generics), morphine, and meperidine (Demerol, generics) for analge-sia and euphoria • Sedative/hypnotics: Nonbarbiturates such as propfol (Diprivan) • Sedatives: Barbiturates such as pentobarbital may also be used if the patient cannot take benzodiazepines.

The most common method for achieving anxiety control in dental patients is with a combination of the following

Yes

is nitrous oxyde safe for children?

Nitrous oxide has been reported to be used by medical/den-tal professionals for recreational use. Long-term exposure of nitrous oxide can result in numbness of extremities (neuropa-thy), vitamin B12 deficiency, and reproductive adverse effects.

Abuse of NItrous Oxide

having the patient eating light amount of food before the appointment.

How to minimize nausea and vomiting after Nitrous oxide administration?

Moderate sedation

- a drug-induced state - administered to patients undergoing minor surgical procedures. It is used in the dental office or hospital (AKA conscious sedation) refers to the administration of drugs for the purpose of sedation (sleepiness), lack of awareness of surroundings (nar-cosis), amnesia (loss of memory), or analgesia (increased pain threshold without loss of consciousness), so the patient still responds to verbal (arousable) and physical stimuli during stressful dental/medical procedures. - Administration of drugs to produce sedation, narcosis, amnesia or analgesia • ENTERAL route: Absorption is through the GI tract (e.g., oral, rectal, sublingual), the most common route for moderate sedation. •Pt responds to verbal and tactile stimuli •Pt can maintain airway with spontaneous ventilation and normal cardiovascular function

Minimal sedation

- a drug-induced state •Antianxiety meds can be given prior to dental appt. •Pt responds normally to verbal commands and independently and continuously can maintain airway and respond to tactile sensation. •Mildly Impaired coordination/cognitive function •Normal cardiovascular function

Deep sedation

- a drug-induced state •Performed in hospital/surgical center •Pt cannot be easily aroused but will respond following repeated/painful stimuli •Spontaneous respiration but may need airway assistance

General anesthesia

-> Used on major general surgery, such as stomach, liver, intestines, heart, and eyes. •Induced state of unconsciousness •Partial or complete loss of protective reflexes •Inability to maintain airway independently (may need a ventilator) •Inability to respond to verbal/tactile commands •Often "balanced" anesthesia is used: low doses of several drugs used to minimize adverse events and speed recovery

III, IV

A medical consultation from the patient's physician may be required, especially for ASA ___ OR ____

Sedative/Hypnotics: Barbiturate

Barbiturates are used for anxiety reduction, light sedation, and general anesthesia. Barbiturates used for moderate sedation are classified as sedative hypnotics. Barbiturates produce sleep by depression of central nervous system activity with minimal car-diovascular effects at sedative doses. Their popularity over the years has been reduced by the benzodiazepines; however, they still are being used because of the ease of multiple routes of administration. Several disadvantages include respiratory depression, irritation of rectal mucosa with rectal administration, and slow onset with oral administration. Paradoxical excitement can occur when the barbiturate instead of causing depression causes excitement, especially when used for painful procedures. Barbiturates have primarily been replaced by other drugs that cause fewer adverse effects. For dental situations, it is recommended to use a short-acting barbiturate such as pentobarbital or secobarbital. The duration of action is about 3-4 hours. Longer-acting barbiturates such as phenobarbital are used as anticonvulsant drugs.

Anti-Anxiety Agents: Benzodiazepines

Benzodiazepines are used to treat anxious dental patients. These drugs are sedating, reduce anxiety, induce relaxation, and produce amnesia. Some benzodiazepines used for IV sedation dentistry are diazepam (Valium) and midazolam (Versed). Diazepam, a long-acting benzodiazepine, can be irritating when administered IV and may cause pain at the injection site. On the other hand, midazolam, a short-acting benzodiazepine, causes less pain at the site of injec-tion and is primarily used for preoperative sedation and for proce-dures that do not require a high level of analgesia. Midazolam has greater potential for respiratory depression in older adults than in children, and has a pregnancy category of D (warning for use in pregnant women). For an adult the dosage is IV 1-1.5 mg, which may be repeated in 2 minutes prn or IM 0.07-0.08 mg/kg 30-60 minutes before the dental procedure (Table 5-2). Diazepam oral solution is recommended for children over 6 years. Another ben-zodiazepine, triazolam (Halcion), has a pregnancy category of X, so it is contraindicated in pregnant women. Respiratory status should be monitored in the dental patient taking a benzodiazepine. The effects can be reversed with fluma-zenil (Mazicon, Romazicon). Additionally, the dental hygienist should observe the patient for possible abuse and dependency on the drug. Benzodiazepines are also used for oral minimal/moderate sedation of apprehensive and fearful dental patients. Orally admin-istered benzodiazepines include lorazepam (Ativan), chlorazepate (Tranxene), alprazolam (Xanax), and triazolam (Halcion). The medication can be taken either the night before or one hour before the dental procedure. Oral benzodiazepines have the same drug interactions as injectable benzodiazepines. Flumazenil (Mazicon, Romazicon) is a benzodiazepine antagonist and is given to patients to reverse the action of a benzodiazepine in cases of overdose.

induction (if used alone for moderate sedation) or maintenance (if used after intravenous general anesthetic) of anesthesia.

Nitrous oxide (N2O) is a colorless, sweet-smelling gas used for what?

Nitrous oxide is rapidly absorbed from the pulmonary alveoli into the bloodstream. The higher the concentration of nitrous oxide in the mask, the more rapidly the same concentration will develop in the lungs. When the high concentration of nitrous oxide at the mask is removed, the concentration falls and the nitrous oxide unchanged is removed from the body in the expired air at the same rate.

Nitrous oxide pharmacokinetics

Sedative/Hypnotics: Nonbarbiturates

PROPOFOL Nonbarbiturates are preferred over barbiturates because they have fewer side effects, including less cardiac depression. Propofol (Diprivan) is widely used for conscious sedation because it is associated with rapid recovery without hangover and nausea and vomiting. It has a rapid induction (40 seconds) and short duration of action (5-10 minutes) with a quick recovery. It can be used for lengthy surgical procedures, unlike thiopental, because it is rapidly metabolized by the liver and excreted in the urine. Propofol is usually combined with an analgesic agent or local anesthetic because by itself it provides no analgesia. Adverse effects include twitching, jerking, coughing, and vasodilation, which can result in marked hypotension. It is available as an emulsion, which contains soybean oil and egg phosphatide. NARCOTICS Opioids are used to produce mood changes, pro-vide analgesia, and elevate the pain threshold. Narcotics are also used to reduce the dose of intravenous anesthetic and are usu-ally used with benzodiazepines and as supplements to nitrous oxide. Narcotics commonly used for conscious sedation include fentanyl (Sublimaze) and meperidine (Demerol). For children, intranasal or oral transmucosal routes ("lollipop") for fentanyl (Sublimaze) and sufentanyl (Sufenta) are available and achieve both analgesia and sedation. Narcotics have a direct effect on the gastrointestinal tract, causing constipation. Other side effects include respiratory dif-ficulties, headache, itching, and nausea and vomiting.

I, II

Patients receiving anesthesia should be medi-cally stable with an ASA ___ or ___

The National Institute of Occupational Safety and Health (NIOSH) reported nitrous oxide levels of approximately 50 ppm were achievable in the dental office. To keep occupational expo-sure to a minimum, the procedure time should be short and there should be ventilation and monitoring devices. Faulty equipment can pose hazards for dental/medical clinicians in the room, especially spontaneous abortion and genetic effect

Risks of occupational exposure to Nitrous

-> most common: nausea and vomiting *Caused by very high concentrations, or on an empty or full stomach ** can be minimized by having the patient eat a light amount of food before the appointment (avoid large meals within 3 hours of dental visit to prevent vomiting. -> Chronic abuse is associated with a fall in the white cell count and neuropathy (nerve damage including numbness of limbs). * Megaloblastic anemia can occur with abuse of nitrous oxide. * can also lead to reproductive side effects There may be an added sedative effect when a patient is also taking sedative drugs or St. John's wort.

What are the adverse effects of Nitrous oxide?

Oxygen is the green tank and nitrous oxide (N2O) is the blue tank.

What are the colors of the nitrous oxyde and oxygen tanks?

- Chronic obstructive pulmonary disease (COPD; bronchitis, emphysema), - upper respiratory obstruction (e.g., cold, stuffy nose, blocked Eustachian tubes), - epilepsy, - first trimester of pregnancy, - communication difficulty, - fear of sedation/negative past experience

What are the contraindications for Nitrous Oxide?

Nitrous oxide is administered with oxygen by adjusting the con-centration of nitrous oxide to titrate the patient to the desired level of sedation Pure oxygen (100%) is administered with a mask for the first 2-3 minutes, and then nitrous oxide is added to the oxygen in 5-10% (up to about 20-30%) con-centrations until the desired level of sedation is reached. The sug-gested induction dosage for patient comfort is about 50% or less (50/50). For maintenance the dosage should be 30/70. Onset of sedation is usually within 3-5 minutes. When the dental procedure is finished the patient must be administered only 100% oxygen for at least 5 minutes. Diffusion hypoxia (low oxygen levels to the tis-sue; headaches can develop) may result when there is not enough oxygen delivered. To prevent hypoxia, the mask should not be removed until the patient receives enough oxygen.

What are the steps in Nitrous oxide administration?

achieve anxiety reduction, pain control, and amnesia in the dental patient.

What is the goal of moderate sedation?

When used alone, nitrous oxide has a rapid action (2-3 min-utes) and a rapid recovery without loss of consciousness. analgesia is obtained in less than 20 seconds and the patient is relaxed in 30-60 seconds when using the demand-valve positive pressure.

What is the onset for Nitrous oxide?

Watch for respiratory status (adequate airway and gas exchange), state of consciousness, heart rate, and blood pressure. The dental hygienist must also be aware of drug antagonists that are used to reverse the actions of some of these drugs. However, once some of these drugs are injected into the blood, it is not possible to reverse the action

What should the hygienist monitor in order to insure the safety of patients and the recognition and management of adverse reactions and emergencies?

Generally, sedation is restricted to uncooperative children.

When is sedation administered in children?

Chronic obstructive pulmonary disease (e.g., bronchitis or emphysema) because there is damage to the alveoli in the lungs and they do not perform gas exchange as easily or well as someone with healthy lungs would. Also, COPD patients require low oxygen concentrations in the blood as their primary stimulant for respiration. Using high-dose oxygen in these patients can cause respiration to stop. • Respiratory obstructions (e.g., stuffy nose, blocked eus-tachian tubes) because the patient needs to breathe in the nitrous oxide/oxygen mixture. May not be able to breath through the mask. • First-trimester pregnancy. Chronic exposure to pregnant women increases the incidence of miscarriages. Bowel obstructions because nitrous oxide use may contrib-ute to bowel distention. • Cognitive impairment.

Why is Nitrous oxyde contraindicated in some conditions?

t/f Nitrous Oxide is relatively nontoxic, and does not produce respiratory depression (slow breathing), bronchodilation, hypo-tension (low blood pressure), or heart arrhythmias. This makes it an ideal, safe sedative agent in the dental office (Table 5-3).

t

t

t/f N2O It is a weak general anesthetic and is generally not used alone in anesthesia; however, it has marked analgesic and amnesia properties

• Fearful, anxious patient (child/adult) • Cognitively, physically, or medically compromised child or adult • Gag reflex interfering with oral health care • Profound local anesthesia cannot be obtained or tolerated • Cardiac conditions, hypertension, asthma, cerebral palsy

what are the indications for Nitrous oxyde?

Megaloblastic anemia

what disease can be caused by abuse of nitrous oxide?

balanced anesthesia

when Nitrous oxyde is used in combination with other anes-thetic agents or drugs in low doses to reduce the requirements (MAC) of other, more potent agents.

before treatment is started

when should ASA classification be done?

Guedel's stage of anesthesia

•Stage 1: amnesia and analgesia •Stage 2: excitement and delirium •Stage 3: surgical anesthesia Stage 4: medullary paralysis/overdose