anyone remember how fast uptake of lidocaine from epidural space ? yes its definitely over the 'recommended amount' but at the same time, the recommended amount (like others above said) is bogus and based on pretty much not much of anything. these days people are sometimes recommending 2mg/kg/hr of lidocaine IV . do it for 6 hours and its way over the recommended amount. but the recommendations doesnt even say over what period of time it applies for
For what it’s worth, the article below used doses below 2mg/kg/hour in 32 patients and reached plasma levels higher than what is apparently considered safe in a few of their patients. In the actual article, they review old papers in humans where lidocaine boluses were given, blood levels sampled, and symptoms recorded. Sample sizes were small but there was apparently some evidence of cardiovascular instability at the plasma level defined as the cutoff for toxicity in the current study.
Background Growing evidence suggests that intravenous lidocaine as a component of multimodal analgesia improves recovery after major colorectal surgery. There is little published data regarding ideal dosing and target plasma concentration in this context, and we wanted to establish our dosing...
perioperativemedicinejournal.biomedcentral.com
Background
Growing evidence suggests that intravenous lidocaine as a component of multimodal analgesia improves recovery after major colorectal surgery. There is little published data regarding ideal dosing and target plasma concentration in this context, and we wanted to establish our dosing schedule was safe by measuring blood levels of lidocaine.
Methods
We measured the plasma lidocaine concentration of 32 patients at 30 min, 6 h and 12 h after starting intravenous lidocaine infusion for analgesia after major colorectal surgery. Patients received a bolus of 1.5 mg kg−1 over 20 min at the time of induction of anaesthesia. This was followed by a continuous infusion of 2%
w/
v lidocaine at 3 ml hr−1 (60 mg hr−1) for patients weighing up to 70 kg and 6 ml hr−1(120 mg hr−1) for patients weighing over 70 kg, using actual body weight.
Results
The overall mean plasma lidocaine concentration was 4.0 μg ml−1 (range 0.6–12.3
μg ml−1). In patients treated with the higher infusion dose, the mean concentration was 4.6 μg ml−1 compared to 3.2
μg ml−1 in those patients on the lower dose. Mean levels were higher at 6 h than 30 min and higher again at 12 h. There were no adverse events or reports of symptoms of local anaesthetic toxicity.
Conclusions
Whilst there were no signs or symptoms of lidocaine toxicity in our patients, there was a wide range of plasma concentrations including some over 10
μg ml−1; a level above which symptoms of toxicity may be expected. We have changed our dosing protocol to using ideal rather than actual body weight based on these results.
Fig 1. Plasma lidocaine levels in patients on the 60 mg hr−1 protocol in whom all three levels were obtained (8 patients)
Fig 2. Plasma lidocaine levels in patients on the 120 mg hr−1 protocol in whom all three levels were obtained (15 patients)
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