Succinylcholine is a medication (depolarizing muscle relaxant) that is used as part of an anesthetic (going to sleep for surgery). This medication can cause significant muscle soreness. Rocuronium is a medication (non-depolarizing muscle relaxant) that some anesthesia providers believe may reduce muscle soreness caused by succinylcholine if given prior, but this has been controversial. Some anesthesiologists pretreat patients with rocuronium before giving patients succinylcholine, and some do not. The purpose of this study is to examine the effect of pretreatment with rocuronium on muscle soreness associated with succinylcholine administration.

After IRB approval from Indiana University Hospital and with written and verbal informed consent from each patient, 300 ASA I, II and III outpatients scheduled for elective Endoscopic Retrograde Cholangiopancreatography (ERCP) under general anesthesia will be enrolled in this randomized-controlled study. The participants and the study personnel performing post-op assessments will be blinded. Anesthesia providers cannot be blinded during this study since anesthesia providers will be required to draw up the study drugs as well as managing the wait time between rocuronium and succinylcholine. Patients are assigned to one of three groups (n = 100 each group). Each participant will undergo a standard IV induction of anesthesia (Lidocaine 1mg/kg, propofol 1-2 mg/kg titrated to effect, and succinylcholine (administered as indicated by study group assignment). Study group details are as follows: Group 1 (Control) to receive no rocuronium pretreatment and 1 mg/kg of succinylcholine. Groups 2 and 3 to receive 0.05 mg/kg up to 5 mg of rocuronium; patients ranged from 50-120 kg. In Group 2, succinylcholine administration will occur at 1.0 mg/kg at t = 1 minute after pretreatment with rocuronium. In Group 3, succinylcholine will be administered (1.0 mg/kg) at t = 2 minutes after pretreatment. The Succinylcholine-induced fasciculations will be noted on study assessment data sheet as either present or absent. . Myalgia assessment is to occur post-succinylcholine administration at t =3 hours and t = 24 hours and will be rated as described below.

Myalgia assessment:

Participants will by queried at the above time points about muscle pain and scored based on their answers as follows.

0 - no pain /no muscle stiffness

1. - mild muscle pain and/or stiffness at 1 or more sites that does not limit daily activity
2. - Moderate muscle pain and/or stiffness at 1 or more sites that does not limit daily activity
3. - Moderate generalized muscle pain and/or stiffness limiting daily activity
4. - Severe muscle pain and/or stiffness at 1 or more sites limiting movement and preventing daily activity

Inclusion Criteria:

• Undergoing elective Endoscopic Retrograde Cholangiopancreatography (ERCP) under general anesthesia
• Have been informed of the nature of the study and informed consent has been obtained

Exclusion Criteria:

• Patients will be excluded if they have chronic pain requiring daily opioid use greater than 30 mg PO morphine equivalent.
• Patients will also be excluded if their comorbid medical conditions require a true rapid sequence induction as precurarization with rocuronium increases the time to intubation which is undesirable in a patient who is at high risk for aspiration.
• Patients taking muscle relaxants at home for spasticity.
• Patients under the age of 18 years old.
• Any contraindication for using succinylcholine or rocuronium.

There is a total of 290 participants, randomized to a control arm and 2 experimental arms.

24 hours post succinylcholine administration

Randomization will be performed using Research Randomizer in blocks of 30. The primary investigator will inform the person doing the case as to what group the participants are randomized. Both the participants and the research staff doing assessments will be blinded.