Combined spinal and epidural Anaesthesia (CSEA) using separate interspace technique

Background: The CSEA technique cannot be considered simply as an isolated spinal block followed by an isolated epidural block as combining the techniques may alter the characteristics of each block. This study was made to evaluate the clinical characteristics of CSEA. Methods: The study included 50 patients, undergoing elective lower limb and lower abdominal surgeries. An epidural catheter was secured at L ₂-L ₃ and subarachnoid block was performed at L ₃ - L ₄ interspace with 2ml of bupivacaine heavy 0.5%. Sensory blockade and haemodynamics were monitored at regular intervals. At 30 ^th minute epidural catheter was activated with 10 ml of bupivacaine 0.5% and monitoring was continued till the 60 ^th minute of the study. Results: Maximum levels of sensory blockade in spinal phase were T ₁₀ - 24%; T ₉ - 30%; T ₈ - 24% and in epidural phase were T ₆ - 26%; T ₅ - 34%; T ₄ - 26%. Average onset times were 12.56 and 11.20 minutes in spinal and epidural phases respectively. Segmental increase in epidural phase averaged 3.8 segments. Percentage population with significant (≥3 segments) increment was 78%. Most with a significant segmental increase had a lower level of sensory blockade in the spinal phase (i.e., T ₁₁, T ₁₀ & T ₉). The rate of rise of sensory blockade showed an initial rapid phase followed by a sustenance phase. The magnitude of haemodynamic change from the baseline was computed from the "effect size of Cohen". Pulse rate, systolic, diastolic and mean blood pressure showed a positive effect, peaking twice, once in the spinal and another in the epidural phase. Conclusion: A preexisting subarachnoid block can be rapidly and significantly raised by an epidural injection of the drug, long after the spinal blockade had taken its full effect. In those who develop a lower level of sensory blockade in the spinal phase, the likelihood of significant rise in the epidural phase is high. The rate of rise of fixed sensory blockade in the epidural phase is rapid and predictable, especially in its initial part.