Evaluation of Intravenous Lidocaine and Time to Regression of the Sensory Block After Spinal Anesthesia (ELSA Trial)

Hypotheses:

Null hypothesis

H0: The time to T12 regression of the sensory block after administration of isobaric bupivacaine is EQUAL with or without the use of intravenous lidocaine in continuous infusion.

Alternative hypothesis

H1: The time to T12 regression of the sensory block after administration of isobaric bupivacaine is DIFFERENT depending on the use or not of intravenous lidocaine in continuous infusion.

Methods

Study design

It is a randomized, controlled, triple blind clinical trial (patient, assistant team / investigator, and data collection/analysis).

Standard procedures

All patients should undergo an outpatient preoperative evaluation with an anesthesiologist. At that moment, eligibility for the study will be evaluated and the informed consent form will be presented. The preoperative form will also be completed by the investigator of the study who includes the patient of the patient.

Study participants will undergo continuous 5 leads electrocardiographic, automated noninvasive blood pressure and capnography monitoring initiated at the entrance to the operating room. Peripheral venous access will also be obtained. After certification of monitoring and venous access the patient will be positioned in lateral decubitus with the side to be performed the surgery (or the side of higher major surgical trauma in case of bilateral procedures) superiorly (e.g. surgery with right side of the body the puncture will be performed in left lateral decubitus) and then will be initiated the infusion the solutions present in the syringe and in the bag sent by the Division of Pharmacy of the hospital unit according to the protocol. Immediately after the initiation of continuous infusion of the solution the anesthesiologist will begin preparation for performing subarachnoid puncture with a Quinke needle between 22 and 27 Gauge (preferably 26 Gauge) between spaces L4-L5 and L2-L3 (preferably L3-L4) depending on the assessment of the anesthesiologist responsible for the predicted difficulty for the block and the risk of post-dural puncture headache. Conscious sedation with propofol in continuous infusion and local anesthesia with 1% lidocaine solution up to 100 mg will also be initiated. It will be administered in the subarachnoid space 13mg (2.6 ml of solution) of isobaric bupivacaine at 0.5%.

As a multimodal and antiemetic analgesia regimen, the following will be administered:

• dexamethasone 4mg in the operating room;
• ondansetron 4mg in the operating room and in case of postoperative nausea or vomiting;
• dipyrone 20mg.kg-1 every 4 hours or paracetamol 500mg every 4 hours (in case of dipyrone allergy) started before regional anesthesia and kept until discharge;
• tenoxicam 40mg in the OR and 20 mg on the first postoperative day, unless contraindicated by the assistant team;
• tramadol 50mg up to every 4 hours or morphine 4 mg up to every 10 minutes in case of pain assessed by verbal numerical scale greater than or equal to 4 (0-10) or according to evaluation of the assistant team.

After the block, evaluations of the extension of sensory and motor block will be performed at minutes 5, 10, 15 and then every 15 minutes as presented in the data collection form . The sensory block will be evaluated by pinprick sequentially from the most caudal to the most cephalic level, at the midclavicular line, on the opposite side of the surgical procedure (or on the side of minor surgical trauma in case of bilateral procedures) and will be computed as the level of blockade the point at which the patient reports sensitivity similar to reference point (homolateral shoulder) will be computed. Motor block will be initially evaluated for ankle flexion, followed by knee elevation and finally leg elevation with knees extended, and the level of motor block will be recorded according to the modified Bromage scale on the opposite side of the surgical procedure (or on the side of lower surgical trauma in case of bilateral procedures).

The patient will be released for the surgical procedure as soon as he reaches motor block evidenced by a modified Bromage scale equal to 2. During the procedure, only sensory block will be observed so that there is no interference with the surgical procedure. After the end of the procedure, each 15 minutes evaluations of sensory and motor block will be performed. Supplementary sensory and motor status evaluations may be performed in addition to the evaluations every 15 minutes at the discretion of the assistant team. After the end of the surgery. Sensory block and motor block will be evaluated concomitantly until the primary outcome (regression of sensory block up T12 dermatome), regression of motor block to modified Bromage 1 and regression of two dermatomes of the sensory block (secondary outcomes) are achieved.

The patient will be continuously evaluated in the post-anesthetic recovery room until at least the second postoperative hour and until the primary outcome. Twenty-four hours after the end of the procedure, the patient will be reevaluated at the ward, or by phone contact in case of discharge, and the study information and questionnaires will be computed as described in the data collection form.

Intervention

The bolus and infusion of the solution referring to the allocated group will be made:

• After monitoring and obtaining venous access
• Prior to the initiation of continuous propofol infusion and spinal puncture

Group L (Lidocaine):

Lidocaine bolus 1.5 mg.kg-1 intravenous before the onset of lidocaine infusion.

Lidocaine 2mg.kg-1.h-1.

Group S (saline solution):

Lidocaine bolus 0.75 mg.kg-1 intravenous before the onset of saline infusion.

Saline solution.

Group L will be sent a 20 ml syringe of 2% lidocaine and 200 ml of lidocaine solution at 8mg.ml-1 (80ml of 2% lidocaine associated with 120ml 0.9% sodium chloride) Group S will be sent a 20 ml syringe of 1% lidocaine and 200 ml of saline solution (0.9% sodium chloride)

A syringe with 20 ml of solution and a bag with 200 ml of solution indistinguishable between the groups, with the identification of the patient by label prepared specifically for the study will be prepared by the Pharmacy personal. The bag and the solution will be sealed in a waterproof and opaque envelope and sent to the Operating Theatre (OT). The envelope will be stored in the refrigerator of the sector between 3º C and 8º C until the patient is sent to the operating room, when the drugs will be sent to the operating room. At the time designated for the start of the intervention, a bolus of 0.075 ml.kg-1 of the syringe solution, followed by 0.25 ml.kg-1.h-1 in the infusion pump of the solution in the bag will be administered.

Continuous infusion of lidocaine (group L) or saline solution (group S) will be maintained until the sensory block regresses to the T12 level, until the regression of 2 dermatomes of the sensory block and until the motor block reaches the score on the modified Bromage scale 1.

The infusion will be interrupted and the masking will be broken in case of:

• severe neurological disorders (e.g. seizure, respiratory depression);
• cardiac (e.g. atrioventricular block greater than second degree, bradycardia with HR less than 40 bpm not responsive to atropine, refractory hypotension);
• other unforeseen clinical changes that pose a risk to the patient.

The infusion will be maintained until the end of anesthesia and masking in case of need for conversion to general anesthesia (e.g., insufficient block, psychomotor agitation) and the patient will be (1) censored for the outcomes related to the extension of the blockade and (2) will continue contributing to the other outcomes.

Collected variables

The variables evaluated in the study will be collected preoperatively, at the operating room, at the PACU, in the first 24 postoperative hours, and in 30 days and recorded in the RedCap database. All data collected in the study is available at the data collection sheets.

Statistical analysis

Medical records numbers and names will be included in the data collection but will not be imputed in RedCap. Therefore, the participants' data will not be revealed at the time of data extraction and analysis, preserving the anonymity of the research individuals.

The data extracted from RedCap will be analyzed in software R. The groups will be separated by intervention group, but the researcher responsible for the analysis will only have access to the groups after the end of the analysis of the results.

Continuous variables will be presented as mean and standard deviation or median and interquartile range depending on their distribution. To check the comparability between the groups and study, the basal covariates will be presented by intervention group. Bivariate statistical tests will be performed bicaudal chi-squared test, t-test, nonparametric Mann-Whitney test and log rank test depending on the characteristics of the variable. In the outcome "most rostral dermatome achieved by sensory block" each dermatome will be numbered for statistical analysis from S5 to C6 according to the following examples: S5=1, S4=2, S3=3, C8=23, C7=24 and C6=25 and will be analyzed according to its distribution. The primary outcome will be presented graphically by the Kaplan Meier curve. The value of α was set at 0.05. For the primary outcome, the p-value will be analyzed without adjustment for multiple tests. Secondary outcomes will be evaluated without adjustment for multiple comparisons because it is an exploratory analysis.

The sample size was calculation was performed with the software R, package 'WMWssp', command 'WMWssp'. Based on previous studies, the mean time for regression was estimated at 120 minutes standard deviation for sensory block regression after subarachnoid anesthesia with bupivacaine in 20 minutes. Adopting the α value of 0.05, the power of 80%, and a 10% drop out rate, the estimated sample size to demonstrate the difference of 15 minutes in the primary outcome was 66 patients (R software input: 'WMWssp(round(rnorm(1000000, 120, 20)), rnorm(1000000, 135, 20), alpha = 0.05, power = 0.8, t = 1/2, simulation = FALSE, nsim = 10^4)').