Local Anesthetics
| Medication | Onset | Duration (Epidural) | Duration (Spinal) | Max dose |
|---|---|---|---|---|
| Bupivacaine: 0.125%-0.75% | Moderate | 2-5 h | 1-4 h | 2.5 mg/kg plain; 3 mg/kg with epi |
| Lidocaine: 1%-2% | Fast | 1-2 h | 0.5-1 h | 4.5 mg/kg plain; 7 mg/kg with epi |
- Lumbar Epidural Bolus: 5-10 cc bupivacaine 0.125%, or 1% lidocaine for more rapid onset
- Thoracic Epidural Bolus: 3-5 cc bupivacaine 0.125%, or 1% lidocaine for more rapid onset
- Epidural for C-Sections: 10-15 cc 2% lidocaine with Epi + 1 cc bicarb for faster onset of surgical block
- Spinal for C-Section: 10 mg bupivacaine 0.5% with 8% dextrose
- +/- 15-20 mcg fentanyl or 150 mcg IT morphine
- +/- 10-30 mcg clonidine
- IT morphine: 2-3 mg Epidural or 150 mcg Spinal
- Spinal for Ortho: 15 mg bupivacaine 0.5% (PF)
Calculating mg dose:
- Every LA comes in a % concentration. Move the decimal 1 place to the right to calculate mg/cc:
- 2% lidocaine = 20mg/cc | 0.25% bupivacaine = 2.5mg/cc | 0.1% ropivacaine = 10mg/cc
“3 – 5 – 7” rule for maximal toxic dose:
- 3mg/kg = bupivacaine, ropivacaine
- 5mg/kg = lidocaine
- 7mg/kg = lidocaine with epinephrine
Systemic absorption:
- “IT ICEBALLS” IV > Tracheal > Intercostal > Caudal > Epidural > Brachial plexus > Axillary > Lower Limb (sciatic/femoral) > SubQ
Local Anesthetic Toxicity (LAST)
- Symptoms: oral numbness/ear ringing → CNS agitation/sz → cardiac arrest
- ACLS with decreased epinephrine dose (1mcg/kg)
- Intralipid 1.5 cc/kg bolus, then infusion 0.25 cc/kg/min. Acts as a “sink” to soak up the LA
Calculating Adrenalin in mcg/cc
- “Rule of a million” for epinephrine:
- Epi can both prolong and deepen the block. Can also act as an intravascular marker.
- Divide 1,000,000 by the number to the right of the semicolon = epi in mcg/cc
- i.e. Lido with epi 1:200,000 → 1,000,000/200,000 = 5 mcg of epi/cc