Acronym: LAST
Life-threatening adverse reaction to local<unk><unk> .
Incidence = ~0.2% of nerve blocks
Generally occurs within minutes of injection
Injection of local<unk>  into<unk>  circulation
Most common source of<unk> 
Intravascular injection can cause<unk>  below the maximum recommended dose
Exceeding the maximum dose of local<unk>  (see table below)
Absorption of<unk>  into<unk>  circulation by injection into extremely vascular area.
Most common source of<unk> 
Intravascular injection can cause<unk>  below the maximum recommended dose
1% soln contains 10 mg/ml
2% soln contains 20 mg/ml
0.5% soln contains 5 mg/ml
May cause cardiac arrest if injected intravascularly
Do not buffer with bicarbonate
Injectable 1% diphenhydramine (10 mg/mL) can be used as a local<unk>  alternative to ester/amide<unk> s
Sodium channel blocker mechanism
1-2 mL of 1% diphenhydramine at a time, to not exceed excessive sedation dose
Typical vial is 50 mg/mL, so to make 10 mg/mL:
10 mL NS removed from 50 mL vial
Add 10 mL of 50 mg/mL diphenhydramine to 40 mL of NS
Sedation is dose related and is similar to what would be expected for IM doses
Relative contraindications are the same for IM diphenhydramine administration
Sodium channel blocker mechanism
1-2 mL of 1% diphenhydramine at a time, to not exceed excessive sedation dose
Typical vial is 50 mg/mL, so to make 10 mg/mL:
10 mL NS removed from 50 mL vial
Add 10 mL of 50 mg/mL diphenhydramine to 40 mL of NS
Sedation is dose related and is similar to what would be expected for IM doses
Relative contraindications are the same for IM diphenhydramine administration
10 mL NS removed from 50 mL vial
Add 10 mL of 50 mg/mL diphenhydramine to 40 mL of NS
Sedation is dose related and is similar to what would be expected for IM doses
Relative contraindications are the same for IM diphenhydramine administration
Local anesthetic systemic toxicity
Anaphylaxis
Nitrogen narcosis
Anxiety
Calcium channel blocker toxicity
Methemoglobinemia - local anesthestics oxidize Fe2+ to Fe3+ in Hb
Cholinergic crisis
Phenothiazines