title: What constitutes an effective but safe initial dose of lidocaine to test a thoracic epidural catheter?
abstract: To investigate the effects of age and dose on the spread of thoracic epidural anesthesia, we placed thoracic epidural catheters in 50 surgical patients divided into groups by age (Group I [young], 18-51 yr; Group II [old], 56-80 yr) and randomly assigned patients to receive either 5 mL (A) or 9 mL (B) of 2% lidocaine (plain) injected via the epidural catheter. Hemodynamic variables were measured (heart rate, mean arterial blood pressure, noninvasive impedance cardiac index) at baseline and every 5 min for 30 min. Detectable blockade occurred within 8 min after injection of 3 + 2 mL or 3 + 6 mL in 48 of 50 patients. Maximum spread of analgesia to pinprick occurred 15-23 min after completion of local anesthetic injection and was significantly different between age and volume groups by two-way analysis of variance (Group IA [young 5], 10.9 +/- 4.0 dermatomes; Group IIB [young 9], 13.9 +/- 4.5 dermatomes; Group IIA [old 5], 14.1 +/- 5.6 dermatomes; and Group IIB [old 9], 17.4 +/- 5.1 dermatomes). Minor decreases in mean arterial blood pressure (8%-17%) and heart rate (4%-11%) were noted. Two patients in the Old 9 group required IV ephedrine or ephedrine/atropine to treat hypotension and bradycardia. We conclude that given the rapid onset (3-8 min), extensive spread (11-14 dermatomal segments), and consistent hemodynamic stability, thoracic epidural anesthesia should be initiated with lidocaine 100 mg (5 mL 2% lidocaine) to establish proper location of the catheter in the epidural space in both younger and older patients.
authors.affiliation: Department of Anesthesiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814-4799, USA. sholman@usuhs.mil
authors.forename: S J
authors.initials: SJ
authors.lastname: Holman
authors.forename: R R
authors.initials: RR
authors.lastname: Bosco
authors.forename: T C
authors.initials: TC
authors.lastname: Kao
authors.forename: M A
authors.initials: MA
authors.lastname: Mazzilli
authors.forename: K J
authors.initials: KJ
authors.lastname: Dietrich
authors.forename: R A
authors.initials: RA
authors.lastname: Rolain
authors.forename: R A
authors.initials: RA
authors.lastname: Stevens
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002302:Cardiac Output / Q000502:physiology; D002307:Cardiography, Impedance; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000187:drug effects
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine