Local anesthetic works immediately but vasoconstriction takes 7-10 minutes
Maximum amount = (Weight in kg/10) * (max dose in mg/kg / concentration of solution)
(Weight in kg * max dose) / (concentration%x10)
- Lido 3mg/kg
- Lido + epi 7 mg/kg
- Bupiv 2 mg/kg
- Bupiv + epi 3 mg/kg
- Marcaine 0.25% 2mg/kg
Lidocaine is most common local anesthetic option. Marcaine is longest acting and should not be used in kids, bupivicaine is also commonly found in emergency departments and is long acting.
- Radial – because of the branching and variable anatomy, this requires more of a field block. inject 5-10cc subcutaneously just above the radial styloid and injecting slightly medially. get the dorsal radial cutaneous branch (which comes out superficially 5-8cm proximal to the radial styloid) by inserting the needle 1cm proximal to the radial styloid and aiming dorsally in the direction of listers tubercle for injection.
- Median – 5cc lidocaine injected between PL and FCR deep in carpal tunnel. You should feel a slight pop as you enter the tunnel. Ask the patient if they feel electric shocks which would indicate you are in the nerve, and if so, pull back before injecting.
- Ulnar – 5cc lidocaine injected above ulnar styloid, immediately radial to FCU (between FCU and ulnar artery – so always draw back before injecting)
- Dorsal wrist/hand – 10cc lidocaine injected in a superficial transverse line across the dorsal wrist.
- Digital – inject 1-3cc lidocaine on either side of the desired digit. Injection points are around 1cm proximal from the end of the web space on the palmar hand, entering about 0.5cm deep. The thumb has a more centrally located nerve you must anesthetize as well.
- Bier block – good for fractures of the arm below the elbow. place an IV in distal extremity, exsanguinate the arm by elevation, apply tourniquet, infuse 1.5-3mg/kg lidocaine through the IV. Tourniquet must stay in place for 30-45 minutes to avoid systemic lidocaine toxicity if it is released before the lidocaine binds to local tissues.
- Interscalene – anesthetizes shoulder and prox UE. Complication: horner syndrome (due to the stellate gangion), hoarseness (paralysis of recurrent laryngeal nerve)
- Supraclavicular – anesthetizes distal UE. Complications: pneumothorax, horner syndrome, paralysis of phrenic nerve
- Infraclavicular – anesthetizes distal UE, axillary, musculocutaneous nerves
- Axillary – anesthetizes median, radia, ulna, musculocutaneous. The musculocutaneous nerve is not in the sheath
- Intercostobrachial – anesthetizes medial upper arm
- Psoas – anesthetizes the femoral, lateral femoralc cutaneous, and obturator nerves
- Femoral – anesthetizes anterior thigh/knee
- Lateral femoral cutaneous nerve – anesthetizes lateral thigh
- Obturator – anesthetizes medial distal thigh
- Sciatic – anesthetizes leg below knee except the medial saphenous distribution
- Popliteal – anesthetizes posterior knee, lateral ankle, foot
- Adductor canal – anesthetizes superficial, medial lower leg and medial ankle/foot
- Saphenous – anesthetizes lower leg/ankle
- Deep peroneal – anesthetizes first webspace of foot
- Superficial peroneal – anesthetizes dorsal foot
- Tibial – anesthetizes calcaneus and plantar foot
- Sural – anesthetizes medial ankle & foot
- TAP – inject between internal oblique and transversus abdominis. Inject in the Triangle of petit (iliac crest, latissimus, external oblique)
Malignant hyperthermia –
- Symptoms: increased ETCO2, tachycardia, muscle rigidity; signs include hyperkalemia, hyperphosphatemia, metabolic acidosis. Caused by -fluranes + succinylcholine à give dantrolene
Lidocaine toxicity –
- Symptoms: dizziness, tinnitus, metallic taste, perioral paresthesia, hypotension, bradycardia à give lipid emulsion
- Need to reverse local anesthetic effects –> give phentolamine (alpha adrenergic blocker)
PABA allergy – Esters are broken down into the metabolite PABA and have only one “i” in their name. If someone has an allergy to PABA, avoid all others with one “I” in the name. The other category of local anesthetics are amides, which have two “i”s in their names.
Salgado, C. J. (2018). Plastic Surgery Emergencies: Principles and Techniques. Plastic and Reconstructive Surgery, 141(5), 1311.