Sequential combined spinal epidural block.

Sir,

We would like to congratulate Dr. Pandya for his timely review on recent advancements in the field of labor analgesia. The newer refinements and developments in the field of central neuraxial blockade are indeed “exciting” as pointed out by the author.[1] However, we wish to differ from the author regarding the concept of “sequential” combined spinal epidural (CSE) block as a technique, whether used for labor analgesia or as an anaesthetic technique.

The author states that a CSE is a “sequential” “needle through needle” technique that utilizes the advantage of a rapid and profound intrathecal block along with the flexibility and longer duration of an epidural block. It appears from these statements that the “sequential” nature of the block is deemed to be due to the sequence of the initial intrathecal injection followed by the epidural one. However, a sequential CSE is a refinement and advancement of the CSE, whether used as needle through needle or separate injections. It does not merely refer to the sequence of intrathecal and epidural injections one after the other. It implies the deliberate intrathecal injection of a dose of local anaesthetic that is inadequate for the planned surgery. It is then supplemented with small volumes of epidural injections, aiming to achieve the desired block level.[23] This intentional intrathecal underdosing followed by smaller than usual epidural injectate volumes has been shown to be of utility in several patients with compromised cardiorespiratory condition, helping to maintain cardiovascular stability.[4] How the small volumes of epidurally injected local anaesthetic help in augmenting the inadequate spinal block, have been a matter of several observations and trials. The epidurally injected small volumes result in augmenting the spinal block to a larger extent than expected with usage of plain epidural, by causing a thecal compression,[5] as well as by converting pre-existing areas of subclinical analgesia to complete analgesia.[6]