TOF

 Q: 72 years old male with previous history of HTN, DM, CAD, previous CABG, alcoholism, and stroke (with some residual hemiplegia on the left side) is admitted with ARDS secondary to severe pancreatitis. Dure to high asynchrony with ventilator, patient required neuromuscular blockade (NMB) along with sedation and analgesia. Which one precaution is required during the application of Train of Four (TOF)?

Answer: Train of Four (TOF) should be avoided on the paralyzed extremity. 

The train of four (TOF) responses, described as T4/T1 ratio are usually exaggerated in paralyzed extremities. In patients who have a previous history of stroke, there is an upregulation of acetylcholine receptors after denervation on the paralyzed limbs. This results in resistance to nondepolarizing NMB agents. The application of TOF gives variable exaggeration of its ratio. This leads to an underestimation of the degree of systemic neuromuscular blocker.

#neurology

References:

1. Moningi, Srilata MD; Durga, Padmaja MD, DNB, PDCC; Mantha, Srinivas MD; Ramachandra, Gopinath MD, FFARCSI, DA Train of Four Responses in Paretic Limbs, Journal of Neurosurgical Anesthesiology: October 2009 - Volume 21 - Issue 4 - p 334-338 doi: 10.1097/ANA.0b013e3181ad4b37 

2. Iwasaki H, Namiki A, Omote K, et al. Response differences of paretic and healthy extremities to pancuronium and neostigmine in hemiplegic patients. Anesth Analg 1985; 64:864.