Local anesthesia: Uses, types, and risks

Local Complications of Local Anesthesia – Cause, Management, and Prevention of these Complications.

1. Infection
2. Injury to nerves
3. Injury to vessels
4. Trauma to muscles
5. Needle breakage
6. Intraglandular injections and their sequel

1. Infection

• ‘Needle track’ infection – contaminated needle or injection. Through contaminated tissue
• Contaminated solution-especially due to vials
• Break of aseptic technique
• Injecting LA into an area of infection by force or transfer bacteria into adjacent healthy tissue spreading infection.

2. Injury to nerves

• Even 25-30 gauge can cause paraesthesia by mere touching of nerve (neuropraxia).
• Hitting bone may ‘barb’ the tip & cause nerve damage on withdrawal (neurotmesis).
• Paresthesia -persistent anesthesia (anesthesia well beyond the expected duration), or altered sensation (tingling or itching) well beyond the expected duration of anesthesia.
• Hyperesthesia -increased sensitivity to noxious stimuli.
• Dysesthesia – painful sensation to non-noxious stimuli.

Paraesthesia

Neurovascular bundle can be traumatized by

• the sharp needle-tip, movement of the needle tip.
• extraneural or intraneural hemorrhage from trauma to the blood vessels.
• neurotoxic effects of the local anesthesia solution.
• Self-inflicted injury to oral tissues.
• Rx – reassure the patient.
• most cases resolve within eight weeks (Malamed1997).
• Oral B-complex with B12 and B6.

Pain

• Rapid injection insufficient time for diffusion pressure on nerve endings PAIN.
• Improper temp/pH of a solution.
• Contamination with sterilant/alcohol.

Failure to achieve profound local anesthesia:

• Improper technique – too low or too anterior
• Insufficient volume
• Local infection
• Other neurological complications

Diffusion into orbit: ocular and extraocular symptoms

• regional sixth nerve block-paralysis of extraocular muscles-temporary diplopia.
• retrobulbar block (rare).
• optic nerve block, which can result in temporary blindness (amaurosis).
• Horner’s syndrome-like manifestations can occur, including enophthalmos, miosis, and palpebral ptosis.

3. Injury to vessels

• Nick of vessels – hematoma
• Arterial damage – rapidly expanding hematoma
• Prevention:
  • Knowledge of anatomy
  • Modify the tech. as dictated by patients anatomy
  • Minimize the no. of needle penetration into tissues
  • Never use a needle as a probe in the tissues
• Management:
  • Direct pressure-intra/extra oral
  • Usually self-limiting-observe over 48 hours
  • Injection Tranexamic acid iv
  • Arterial bleeds may require ligation
• Epithelial desquamation:
  • Prolonged use of topical anesthetics
  • High concentration of vasoconstrictors
  • Most common on palatal mucosa
• Management
  • Resolves in 7-10 days
  • Mild NSAIDS
  • Na bicarbonate, saline or Peridex mouth rinse
• Maybe a sequel of paraesthesia

4.Trauma to muscles

• Trismus – difficulty/inability to open the mouth
• Various mechanisms:
  • Direct injury of temporalis and medial pterygoid muscle fibers by needle
  • Intramuscular injection
  • Rapid rate on injection
  • Contaminated solution
  • Wrong temperature/pH of the solution
• Prevention :
  • Use a sharp, sterile, disposable needle
  • Proper handling of local anesthetic solution.
  • Not to contaminated needles
  • Practice atraumatic technique
  • Avoid repeat injection. And multiple injections.
  • Use minimum effective volumes of LA.
• Management :
  • Heat therapy ( after 2 days )
  • Warm saline rinses.
  • Analgesics, muscle relaxants.
  • If it does not improve within 48-72 hrs, – infection must be considered — treat with antibiotics.

5. Needle breakage

• Causes :
  • The weakening of dental needles by bending
  • Sudden unexpected movements of the patient
  • Inserting needle up to the hub
  • Smaller gauge needles ( 30 gauge)
  • Defective manufacturing
• Prevention :
  • Use larger gauge needles
  • Do not insert the needle into the tissue till the hub
  • Do not redirect the needle once inserted into the tissue
  • Excessive lateral force on the needle
• Management :
  • DO NOT PANIC
  • Ask the patient not to move or bite
  • If the fragment is visible, try to remove it with a hemostat
  • If the needle is not visible, do not proceed with incision or probing
  • It can be removed immediately. only if it is superficial and easily located through radiological and clinical
• Examination.
  • IN MANY INSTANCES IT IS REMOVED UNDER GA

6. Intraglandular injection

• IANB too posterior – injection within the parotid gland
• Block of CN7-Transient Facial nerve palsy
• Inability to blink/close eye
• Feeling of facial paralysis
• Rx-
  • Reassure patient it is transient
  • protect the cornea