After administration of a non-depolarising muscle relaxant, train-of-four stimulation elicits no palpable twitches at all. To quantify the degree of this deep block, which stimulation modality should be used?

• A Double burst stimulation at 0.75 Hz
• B Tetanus at 100 Hz sustained for 10 seconds
• C Post-tetanic count after a 50 Hz tetanus for 5 seconds ✓
• D Single twitch stimulation at 0.1 Hz compared with baseline

Explanation

When all four TOF responses are abolished, the post-tetanic count provides the only quantifiable measure of deep neuromuscular blockade. A 5 second tetanic stimulus at 50 Hz releases acetylcholine transiently and produces post-tetanic potentiation, allowing a variable number of responses to be counted over the following minutes. A higher post-tetanic count predicts earlier return of TOF responses. Double burst stimulation improves clinical detection of residual block but cannot be quantified when responses are absent.

Reference: Miller's Anesthesia, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.