Neuromuscular blocking agents (NBAs) are widely used in health care settings around the world. They are used for general anesthesia, facilitation of orotracheal intubation, and maintenance of controlled mechanical ventilation in intensive care and anesthesia.
Objective monitoring of neuromuscular blockade (NB) is the only reliable way to ensure the degree of NB and its reversal, avoiding complications and reducing hospital costs, and should therefore be used routinely, as part of the safe surgery protocol. In clinical practice, the most commonly used stimulation pattern is the four-stimulus sequence, commonly known as Train-of-Four (TOF) by acceleromyography, which assesses the degree of muscle strength by the ratio of the last muscle contraction over the first contraction (T4/T1).
In the latest guideline for good practice for clinical research in pharmacodynamic studies for NBA II, it is recommended that before its injection, calibration (obtaining the T1 height of 100%) and stabilization of the muscle response to electrical stimulation must be performed, for a reliable and accurate interpretation of the data. Stabilization represents a maximum variation of 5% of T1 high maintained for a minimum period of 2 minutes before the injection of NBA. This time can take up to 20 minutes to occur, too long a time in clinical studies. To decrease the settling time, a 50 Hz tetanic stimulus should then be applied for 5s before calibration.
The pharmacokinetics and pharmacodynamics of NBAs are altered with aging, but studies in this age group become difficult to perform due to multiple comorbidities. No pharmacodynamic studies of their using tetanic stimulation in patients over 60 years of age have been found in the databases up to the present moment.
In this regard, the primary objective of this study was to determine the time to stabilization of the muscle response with the use of tetanic stimulation prior to TOF monitoring in patients over 60 years of age. Secondary objectives are to determine the onset of action of NBA, clinical duration, pharmacological duration, initial and final T1 height, and recovery from NB.