Excessive dose requirements of local anaesthetic for epidural analgesia. How far should an epidural catheter be inserted?

On two separate occasions, a 78-year-old obese man suffering from congestive cardiac failure and peripheral vascular disease, required epidural anaesthesia for surgery to his leg. The dosage requirement on the first occasion was large and much greater than on the second occasion. Reasons for the difference in dosage are discussed. We suggest an epidural catheter should be inserted 3 cm into the epidural space.