Failure to Obtain Anesthesia in Dentistry

Failure to Obtain Anesthesia

• Failure to obtain anesthesia is the most common problem seen during the use of local anesthesia, especially with block anesthesia in the lower jaw.
• Causes of failure to obtain anesthesia: • Poor technique: injecting anesthesia too soon on the anterior ascending ramus, giving the solution inferior to the mandibular foramen. • Anatomical causes: accessory nerve supply, abnormal course of the nerve, variation in the foramen location, and innervation of the tooth by more than one nerve. • Pathological causes: trismus, infection, and inflammation affecting the pulp and nerve. • Psychological causes: fear and anxiety, requiring relaxation of the patient and sometimes the use of a sedative like benzodiazepine.

Persistent Anesthesia or Paraesthesia

• Defined as altered sensation beyond the expected duration of anesthesia or prolonged loss of sensation.
• Common in dental practice, with potential for self-inflicted injury, biting, thermal, or chemical trauma.
• Patients should remove contact lenses until muscular movement returns.

Trismus

• Defined as a prolonged spasm of the jaw muscles, restricting normal mouth opening.
• Causes: • Trauma to the muscles due to local anesthetic injection. • Muscle irritation by local anesthetic solution contaminated with alcohol. • Hematoma in or around the muscles. • Infection after injection. • Excessive volume of local anesthetic solution deposited into a restricted area.
• Prevention: • Use sharp, sterile, disposable needles. • Practice atraumatic insertion and injection technique. • Avoid repeated injections and multiple insertions into the same area. • Use the minimum effective volume of local anesthetic solution.
• Management: • Heat therapy. • Analgesic and muscle relaxant. • Physiotherapy: opening and closing the mouth, lateral excursions of the mandible, and chewing gum.

Soft Tissue Injury

• Soft tissue anesthesia lasts longer than pulpal anesthesia.
• Trauma to anesthetized soft tissue can lead to swelling, pain, and infection.
• Causes: Self-inflicted trauma to the lips and tongue when the patient bites or chews these tissues while still anesthetized.
• Management: • First aid treatment should be started immediately. • Spontaneous recovery is usual, and it is often possible to complete the treatment at the same visit.

Cardiopulmonary Resuscitation (CPR)

• An emergency procedure combining chest compressions with artificial ventilation to manually preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person who is in cardiac arrest.
• Recommended in those who are unresponsive with no breathing or abnormal breathing.
• CPR involves chest compressions for adults of about 5 cm deep and at a rate of at least 100 per minute with a universal compression-to-ventilation ratio of 30:2.

Hypersensitivity or Allergy to Local Anesthesia

• More commonly seen with ester-type agents than amide-type agents.
• Causes: • Local anesthetic agent. • Vasoconstrictor. • Additives like bisulfite used as a preservative.
• Prevention: • Proper pre-anesthetic evaluation, including a personal history and past dental history, particularly history of allergy to the local anesthetic agent or any other drug.
• Management: • Antihistamine injection. • Epinephrine 0.5 ml of 1:1000 IM. • Administer O2 if necessary. • Substitution of the local anesthetic agent.

Anaphylactic Shock

• A rare, life-threatening hypersensitivity reaction to an antigen, developing fast and causing death within a few minutes.
• Characterized by: • Profound fall in blood pressure. • Dyspnea and respiratory embarrassment. • Facial and laryngeal edema. • Loss of consciousness.
• Management: • Epinephrine is the most important medication. • Oxygen should be given to improve breathing. • Intravascular (IV) fluid may be necessary to restore adequate blood pressure. • Antihistamine should be given to contract the effect of histamine. • If the patient stops breathing, start CPR immediately.

Overdosage and Toxicity

• Relatively rare, occurring when the concentration of local anesthesia in circulation increases too rapidly within a short period of time.
• The toxic effect is primarily directed to the CNS and CVS.
• Signs and symptoms: • Restlessness, agitation, convulsion. • Increased blood pressure, heart rate, and respiratory rate.
• Prevention: • Use the smallest possible volume and lowest effective concentration. • The local anesthetic solution should be injected slowly. • Avoid intravascular administration by using an aspirating syringe.
• Management: • Stop the dental procedure. • Position the patient supine with legs elevated. • Reassurance of the patient. • Administer O2, IV anticonvulsant, and monitor vital signs.