Maximal haemostatic effect is attained in porcine skin within 7 min of the administration of a local anaesthetic together with epinephrine, refuting the need for a 30 min waiting time

OBJECTIVE: Based on clinical experience gained over many years, the maximal haemostatic effect following administration of local anaesthetics containing epinephrine is generally believed to occur within 10 min. Surprisingly, it was found in a recent study, in which bleeding was quantified intraoperatively, that maximal haemostasis did not occur until 30 min. If this is indeed the case, then it would be necessary to extend the preoperative waiting time to minimize perioperative bleeding. We have carried out a carefully controlled study on the time delay between administration of a local anaesthetic containing epinephrine and maximal haemostasis in a surgical setting. METHODS: Lidocaine 20 mg/ml (2%) or lidocaine + epinephrine 12.5 µg/ml (1:80,000) was injected into the skin of eight pig flanks. Bleeding was induced after 3, 5, 7, 15 and 30 min by making a 10 mm incision at each injection site. Blood was collected for 1 min and weighed. RESULTS: A gradual reduction in bleeding was observed, with maximal reduction after only 7 min (54%, p < 0.05, 95% CI: 44–64%). No further significant reduction in bleeding was observed (62% at 15 and 66% at 30 min, p = n.s. compared to 7 min). CONCLUSIONS: Maximal haemostatic effect in the current setting was observed within 7 min of injection of lidocaine with epinephrine. This is in good agreement with previous empirical findings, and we see no reason to prolong the preoperative waiting time.