Mechanism of the extension of spinal block in combined spinal-epidural anaesthesia: effect of volume or dose?

Marinela-Valerica Haţegan¹, I. Acalovschi²
1) Secţia ATI, Spitalul Judeţean Deva. 2) Clinica ATI, Spitalul Clinic de Adulţi, Cluj-Napoca

Abstract

Aim. To determine the mechanism by which the spinal block is extended as a consequence of an epidural “top-up” in combined spinal-epidural anaesthesia.

Material and method. Thirty patients, scheduled for lower limb orthopedic surgery under combined spinal-epidural anaesthesia were randomly allocated to one of three groups of 10 patients each. Using a needle-through-needle technique, all patients received 8 mg of 0.5 % bupivacaine and 20 µg fentanyl. The maximum level of the spinal sensory block was assessed. Then, through the epidural catheter, patients in group 1 received 10 ml of 0.5 % bupivacaine, patients in group 2 - 10 ml of saline and patients in group 3 - 10 ml of air. The extension and regression of the sensory and motor blocks were assessed every 5 minutes for one hour, then every 10 minutes until the regression of sensory and motor blocks.

Results. The maximal level of sensory blockade during the spinal phase was similar in the three groups: T 6.6 for groups 1 and 3, and T 5.5 for group 2. The epidural “top-up” resulted in a similar increase of the maximal level of sensory blockade in all three groups: by 1.7 segments in group 1, by 1.2 segments in group 2, and by 1.3 segments in group 3 (p>0.05). There were no differences between groups concerning the regression of the sensory and motor blocks.

Conclusions. In combined spinal-epidural anaesthesia, the epidural “top-ups” of equal volumes of 0.5 % bupivacaine, saline and air determined a similar extension of the spinal sensory blockade, suggesting that the mechanism of extension was the volume effect by compression of the dural sac.

Key words: combined spinal-epidural anaesthesia, extension by epidural “top-ups”, bupivacaine, saline, air

Mecanismul extensiei blocului subarahnoidian în anestezia combinată spinal­epidurală: efect prin volum sau prin doză?

Jurnalul Român de Anestezie Terapie intensivă 2005 Vol.12 Nr.1, 39-45