Local anesthesia: Uses, types, and risks

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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.


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.


  • 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 :
    • 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.

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
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  • Aayushi

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