Association between residual neuromuscular blockade and critical respiratory events in post anesthesia care unit -An prospective observation study

Neuromuscular blocking agents (NMBA) are used to facilitate airway management and ensure immobility during surgery thus improving operating conditions.

Complications associated with their use most commonly arise when their paralytic effects have not disappeared or have not been adequately antagonized at the end of surgery

This is called Residual neuromuscular blockade (RNMB) and is associated with adverse outcomes such as upper airway obstruction, reintubation, atelectasis, pneumonia, prolong stay in post anesthesia care unit (PACU) and decreased patient satisfaction

Quantitatively RNMB is defined as a train of four ratio (TOFR) <0.9 in post anesthesia care unit (PACU) secondary to nondepolarizing muscle relaxant (NDMR) administration

The frequency of RNMB ranges between 4 and 50 % depending on diagnostic criteria and type of NMBA drug used, administration of reversal agents and to a lesser extent the use of neuromuscular monitoring (NMM)

Incidence of RNMB has seen a steady decline with the use of perioperative neuromuscular monitoring(NMM)It was estimated to be around 42% in 1979 in a cohort of 72 patients in a seminal report.

This was due to the fact that RNMB was defined as TOFR <0.7 . Subsequently now a broad consensus has been arrived at, and TOFR more than or equal to 0.9 is confirmed to be adequate recovery of neuromuscular function. Despite this RNMB remains a frequent occurrence with incidence as high as 64 %

It has been difficult to prove that RNMB is associated with significant mortality and morbidity due to the relatively low incidence of major adverse outcomes . This is because most patients tolerate RNMB of moderate depth but it is deleterious in patients with limited physiological reserve.

The purpose of the study is to evaluate the occurrence of RNMB and to ascertain its association with critical respiratory events if any.

After approval from institutional ethics committee, patients satisfying the inclusion criteria will be enrolled in the study, thorough preanesthetic evaluation will be conducted according to institutional protocol. General anesthesia will be given according to institutional protocol.

In the PACU, baseline Ramsay’s sedation score will be noted. The patient’s arrival time at the PACU will be designated as point zero (T0). Acceleromyograph (TOF-Watch® stim pod) of the patient’s adductor pollicis muscle will be monitored in the form of TOFR.

The stimulation current will be set at 25 to 30 mA to avoid patient discomfort. The average of two consecutive measurements will be made at a frequency of 2 Hz, with four pulses of 0.2 M s duration separated by 15 s

TOFR values will be recorded at 0, 10, 20, and 30 min (T0, T1, T2, and T3, respectively).The patient’s arterial oxygen saturation (SpO2), Heart rate (HR), systolic and diastolic blood pressure (SBP &DBP) will be noted at 0,10,20,30 min

In the presence of RNMB, additional reversal agents and their doses, as considered necessary will be administered.

If any critical respiratory events are identified in PACU during the study, they will be appropriately managed as per institution protocol