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

I. 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:

• 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.
• 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

V. Study outcomes:

• 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.
• Secondary outcome measures:

• 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).
• Risk of complications from techniques.
• Patient satisfaction after surgery
• Total intraoperative analgesia dose (fentanyl consumption) and total postoperative analgesia dose (morphine consumption).
• 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:

• 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.

• 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.

Inclusion criteria

• Patients aged 20 to 60,
• ASA classification I or II,
• scheduled for arthroscopic shoulder surgery,
• will be randomized 1:1 into two groups before the induction of general anesthesia (GA)

Exclusion criteria

• Patients who refuse participation.
• Have allergies to local anesthetics.
• Phrenic nerve dysfunction.
• Chronic opioid use.
• ASA III or higher classification.
• Coagulopathy.
• Severe chronic obstructive pulmonary disease.
• Local infection at the injection site