LA complications and rescue - test 4 Flashcards
What is the percentage of LA allergic reactions?
Rare: 1%
- mild to IgE anaphylaxis
Are esters or amides more prone to cause allergic reactions?
Esters > Amides because of the PABA
What is the preservative in both esters and amides that can cause an allergic reaction?
Methylparaben - similar in structure to PABA
Is there cross sensitivity between esters and amides?
No
Clinical manifestations of LA allergic reaction:
- Rash
- Urticaria
- Laryngeal edema w/ or w/o hypotension
- Bronchospasm
Steps in managing an LA allergic reaction:
- Stop admininstration
- Supportive care (airway, O2, fluids)
- Epi, antihistamine, corticosteroid
- Allergy testing: skin test with preservative-free LA
What is LAST and what causes it?
Local Anesthetic Systemic Toxicity
- d/t excess plasma concentration of the drug
- entrance into the systemic circulation from inactive tissue redistribution and clearance metabolism (can be from accidental direct IV injection)
Magnitude of systemic absorption of LAST depends on:
- Dose
- Vascularity of size
- Epinephrine use
- Physicochemical properties
What are the CNS effects of LAST?
- Early agitation at 1-10 mcg/mL
- Drowsiness
- Facial twitch prior to seizure
- Hyperkalemia promotes seizures with LAs
Monitor plasma levels of lidocaine epidural > ____?
900 mgs
Plasma lidocaine concentration of 5-10 mcg/ml causes what effects?
- Circumoral numbness
- Tinnitus
- Skeletal muscle twitching
- Systemic hypotension
- Myocardial depression
Predisposing factors for CV system effects with LAST:
- Pregnancy (low plasmacholinesterase)
- Hepatic and renal disease
- Arterial hypoxemia, acidosis, hypercarbia (animals)
- Beta blockers, digitalis preparations, Ca channel blockers
- Epi and phenylephrine use
Which LAs are more likely to cause CV system effects with LAST?
Bupivacaine > Ropivacaine > Lidocaine
What two factors predispose our OB population to LAST?
- Decreased plasma esterases
- Decreased plasma proteins
Lidocaine at ________ mcg/mL will promote circumoral numbness but no CV effects.
However, high plasma concentrations of LA will block what?
5 mcg/mL
Block cardiac Na+ channels
What happens with conduction delays in cardiac impulses?
- Negative inotropy
- Prolonged PR interval and QRS widening
What can happen if you accidentally give IV bupivacaine?
- Precipitous hypotension,
- AV block
- Cardiac dysrhythmias: SVTs, ST-T wave changes, PVCs, widening of QRS, v-tach, cardiac arrest
What are the goals of treatment of systemic toxicity?
- Prompt airway
- Circulatory support
- Removal of LA from receptor sites
Steps of LAST treatment:
- Stop LA immediately
- Call for help
- 100% O2 - inhibit hypoxemia and metabolic acidosis
- Hyperventilation
- Sedation: barbiturates or propofol (if stable)
- Epi as an additive
Treatment for LAST induced seizures:
- Supplemental oxygen
- Benzodiazepine (midazolam or diazepam)
- Propofol if HD stable
- Muscle relaxant (sux or NMDA)
- Intralipid: lipid emulsion
What is the MOA for intralipids?
Creates lipid compartment, provides for fat for myocardial metabolism
What is the dosing for lipid emulsion?
Bolus:
Infusion:
1st 30 minutes:
Bolus = 1.5 mL/kg of 20% lipid emulsion
Infusion = 0.25 mL/kg/minute for at least 10 minutes
1st 30 minutes: 10 mL/kg (1.2-6 mL/kg)
Epi dose for LAST:
What if you have no response?
10 to 100 mcg
No response = cardiopulmonary bypass
A 60 yo, 120 lbs. female has the following vital signs following the administration of Bupivacaine 0.5% 20 mls. through the epidural catheter: 38 (HR), 70/35 (NIBP), 40 (RR) and 92% (Sa02).
How much intra-lipid in mgs would you bolus?
16,200 mgs
