Sat27November0556PM 4

Inadequate reversal of non-depolarising neuromuscular blockade (NMB) can contribute to postoperative respiratory failure.

Which of the following options suggests inadequate reversal?

(Please select 1 option)

Generation of tidal volumes of 15 ml/kg

Ability to hold the head off the pillow for five seconds

Post tetanic count of 5 This is the correct answer

T4:T1 ratio of 0.9 Incorrect answer selected

Four equal twitches on train of four count

Explanation

A post-tetanic count of 5 indicates deep NMB. All the other options suggest adequate reversal.

Post-tetanic counts are used when neuromuscular blockade is so deep that a train-of-four cannot be elicited by a nerve stimulator. T1 is said to disappear at 100% receptor occupancy. However, application of tetanic stimulation at 50Hz for 5s will mobilise enough presynaptic acetylcholine to allow assessment of the degree of intensity of very deep blockade.

The ability to hold the head off the pillow for five seconds and generation of tidal volumes of 15 ml/kg are clinical indicators of recovery from NMB and are incorrect.

A post-tetanic count of >15 approximates two twitches on the train-of-four count. Four equal twitches (that is, no fade) in the context of non-depolarising NMB indicates no blockade present.

A ratio of 0.9 for the twitch height of T4 to T1 indicates successful reversal of, or recovery from NMB.

Answer Statistics

1

3%

2

10%

3

59%

4

24%

5

5%

Times answered: 271