Incidence of residual neuromuscular blockade In post anaesthesia care unit after elective onco-surgeries: a prospective observational study.

Muscle relaxants are used during general anesthesia to facilitate airway instrumentation and to provide optimal muscle relaxation during surgery. It is a routine practice to use non depolarizing muscle relaxants for providing this muscle relaxation. At the end of surgery, the residual effect of muscle relaxants is assessed and reversed if needed before extubating the patient. Absence of residual neuromuscular blockade (RNMB) is essential as it is one of the major contributors of anaesthesia related morbidity and mortality in the post anaesthesia care unit.

Presence or absence of this residual block before extubation has been traditionally assessed by clinicians using clinical criteria and tests. However, many studies performed in awake and anaesthetized patients have now shown that these clinical tests can be performed even in the presence of significant degree of residual neuromuscular blockade. Therefore, objective and quantitative monitoring of neuromuscular recovery by using a peripheral nerve stimulator has been recommended in various anesthesia guidelines. A train of four ratio (TOF ratio) obtained using nerve stimulator by stimulating a peripheral nerve provides an objective assessment of residual blockade. Traditionally, a TOF ratio of less than 0.7 has been used to define inadequate neuromuscular recovery. However, recent guidelines recommend a TOF ratio of more than 0.9 as adequate recovery from neuromuscular blockade. Currently, quantitative neuromuscular monitoring in the form of TOF ratio more than 0.9 is considered as the gold standard for neuromuscular recovery whenever non depolarizing muscle relaxants are used.

Studies done in past have demonstrated very high incidence of residual neuromuscular blockade in the range of 40-50 percent. Although use of intermediate and short acting muscle relaxants and use of novel reversal agents like Sugammadex has helped to reduce its incidence, it is often unrecognized and remains a significant clinical problem. The incidence reported by recent trials is still as high as 40 percent.

Currently, in our institute, intraoperative neuromuscular blockade is assessed by clinical criteria and by qualitative or quantitative neuromusclular monitoring depending on the availability of monitor, type of surgery, feasibility of its application and at the discretion of the anesthesiologist.

This study aims to find the current incidence of residual neuromuscular blockade in the PACU after elective onco surgeries as defined by TOF ratio less than 0.9.

Additionally, we would also like to document the factors affecting it to identify the risk factors for RNMB. We will also observe the need for airway support, the incidence of desaturation in patients with and without RNMB.

This will be a prospective observational study involving adult patients undergoing elective oncosurgical procedures requiring general anesthesia and non depolarizing muscle relaxant agents. The intraoperative administration of anesthesia, neuromuscular monitoring, reversal of muscle relaxants and extubation will be carried as per the institutional standard practice and at the discretion of anesthesiologist in charge.

On arrival of these patients to post anaesthesia care unit (PACU), standard routine monitors will be attached by PACU team. The study team member or the PACU anaesthesia resident on duty will record the TOF ratio within 15 minutes of arrival to PACU. For assessing TOF ratio, patients forearm will be supported on a cushioned arm rest and free mobility of the thumb will be ensured. 2 surface electrodes (ECG leads) will be applied on the volar aspect of the forearm at the level of wrist separated from each other by 3 to 6 cms. These surface electrodes will be connected to the neuromuscular monitor and TOF stimuli will be delivered to the ulnar nerve. The stimulus strength will be set at 40mA. Three consecutive readings of TOF ratio will be obtained at 1 minute interval and two closest readings will be selected. An average of these two readings will be recorded as the TOF ratio of patient. If the TOF ratio is less than 0.9, it will be informed to the PACU team. Further monitoring and management of patient will be at the discretion of PACU team. In addition to TOF ratio, adverse respiratory events will be noted within first 1 hour of PACU admission by the study team member or the attending nurse or the PACU doctor. We will also record intraoperative details from the anaesthesia record form and electronic medical records.

The study will be carried in the main OT complex over a period of three months or in 300 patients whichever is earlier. Incidence of TOF ratio  less than 0.9 will be calculated to determine the incidence of residual neuromuscular blockade.

Patients will be divided into 2 groups based on TOF ratio (less than 0.9 or more 0.9). Secondary outcomes and demographic variables will be compared in the two groups. Continuous variables will be expressed in terms of mean and standard deviation if. All categorical variables will be reported using frequencies and percentages. For comparisons of two groups, independent sample t test or Mann Whitney U test as per the distribution of data for continuous variables and chi-square or Fisher’s exact tests for categorical variables. The relationship between RNMB and risk factors will be determined using a logistic regression model.