Ultrasound-guided Interscalene Block Versus Infraspinatus-Teres Minor Plane Block in Shoulder Arthroscopy

1. Study design:

Randomized comparative study.

II. Study setting and location:

The study will be conducted at the operative room of Souad Kafafi University Hospital (SKUH), Misr University of science and Technology (MUST).

III. Study population:

Patients aged from 20 to 60 years old scheduled for shoulder surgery will be randomized in a 1:1 ratio after induction of general anesthesia (GA) to either: Group A: Received the ultrasound guided ISB technique with a 15ml solution of 7.5ml lidocaine 2% and 7.5ml bupivacaine 0.5% injected between the anterior and middle scalene muscles.

Group B: Received the ultrasound guided ITM block with the same anesthetic solution injected between the infraspinatus and teres minor muscles.

IV. Study procedures:

1. Randomization Patients will be randomly allocated by a computer-generated table into one of the study groups; the randomization sequence will be concealed in sealed opaque envelopes.
2. Study protocol

• All Patients will have a pre-operative assessment visit, which will include; history taking, complete physical examination and review of all the results of the routine investigations (CBC, Coagulation profile, renal functions, liver functions).
• On Arrival to the preparation room, they will receive the following premedication via intravenous (IV) route: Midazolam 0.03 mg/kg, Ondansetron 4 mg and Omeprazole 40 mg iv infusion.
• Upon Arrival to the operating room, standard monitoring will be applied which include: Pulse Oximeter, Noninvasive Blood Pressure and Six-lead electrocardiogram (ECG).
• General anesthesia will be induced using: Propofol 1-2mg/kg, Fentanyl1-2 μg/kg, Morphine 0.1mg/kg and Atracurium 0.5 mg/kg.
• After endotracheal intubation, side way capnography will be applied to measure end tidal CO2 pressure in the expired air.
• General anesthesia will be maintained using Sevoflurane 1-2 MAC (Mean Alveolar Concentrations) in O2/ Air 50% / 50%, Paracetamol 1gm iv infusion, ketorolac 30 mg iv and incremental doses of Atracurium 0.1mg/kg/30 minutes.

The patients will be randomly allocated into two groups:

Group A:

Ultrasound-guided Interscalene block (ISB) technique.

Group B:

Ultrasound-guided Infraspinatus-teres minor (ITM) interfacial plane block technique

1. Study outcomes:
2. Primary outcome measure:

• Efficacy of analgesia by Pain score; will be measured by Numerical Rating Scale (NRS) score (0-10; 0=no pain,1-3=mild,4-6=moderate,7-9=sever,10=most sever) at postoperative12 hours.

1. Secondary outcome measures:
2. Duration of analgesia, starting from recovery from general anesthesia (GA) to 1st time giving the patient rescue analgesia ( measured by NRS pain score at 0, 6 ,12, 18 and 24 postoperative hours).
3. Risk of complications from techniques.
4. Patient satisfaction after surgery
5. Total intraoperative analgesia dose (fentanyl consumption) and total postoperative analgesia dose (morphine consumption).
6. Hemodynamics monitoring; measurements of heart rate and mean arterial blood pressure before induction of anesthesia and every 15 minutes during surgery till end of surgery

VII. Statistical analysis:

1. Sample size: Sample size calculation was based on pain score after Interscalene block (ISB) in shoulder surgery versus other methods retrieved from previous research (Singelyn et al., 2004) (15). Using G power program version 3.1.9.4 to calculate sample size based on effect size of 0.897 (35 ± 25) versus (13±24), using 2-tailed test, α error =0.05 and power = 80.0%, the total calculated sample size will be 21 in each group at least and by adding 10% to compensate for possible drop out then total sample size per group is 23 cases at least.
2. Statistical analysis:

Data will be analyzed using SPSS (statistical package for social sciences) version 22. Quantitative data will be tested for normality by Kolmogrov-Smironv test then described as mean and standard deviation for normally distributed data, and median and range for non-normally distributed, Qualitative data will be presented as number and percent. The appropriate statistical test will be applied according to data type with the following suggested tests: Student t test and Mann Whitney U test for continuous variables, Chi-Square test for categorical variable.