How much local anesthetic is too much

In short

There are two ceilings, not one: how much local anesthetic drug the patient can absorb, and how much epinephrine they can tolerate — and which one you hit first depends on the drug, the concentration, and which published standard you use. My office rule of 7 carpules of 2% lidocaine holds under both standards for most adult weights, but a conservative textbook 300 mg absolute cap (not weight-based) makes the anesthetic ceiling bind first at nearly every adult weight when that cap is carried, and the order only flips without it, around 91 kg. My cardiac cap of 18 mcg of epinephrine (about two cartridges at 1:200,000) is roughly half the commonly quoted 0.04 mg figure — stricter, not looser — and bupivacaine has the narrowest safety margin of the drugs discussed here, the hardest systemic toxicity to resuscitate, and is off-label under age 12.