Back to resultsInterscalene Block Versus Combined Infraclavicular-Anterior Suprascapular Blocks for Shoulder Surgery
Primary Purpose
Pain, Postoperative, Shoulder Pain, Surgical Procedure, Unspecified
Status
Not yet recruiting
Phase
Not Applicable
Locations
Chile
Study Type
Interventional
Intervention
Interscalene Block
Infraclavicular - Anterior Supraescapular Nerve Blocks
Sponsored by
About this trial
This is an interventional supportive care trial for Pain, Postoperative focused on measuring Postoperative Shoulder Analgesia, Diaphragmatic Paralysis, Alternative Blocks
Eligibility Criteria
Inclusion Criteria:
- Patients undergoing arthroscopic shoulder surgery
- American Society of Anesthesiologists classification 1-3
- Body mass index between 20 and 35 kg/mt2
Exclusion Criteria:
- Adults who are unable to give their own consent
- Pre-existing neuropathy (assessed by history and physical examination)
- Coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. platelets ≤ 100, International Normalized Ratio ≥ 1.4 or prothrombin time ≥ 50)
- Obstructive or restrictive pulmonary disease (assessed by history and physical examination)
- Renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. creatinine ≥ 100)
- Hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. transaminases ≥ 100)
- Allergy to local anesthetics (LAs)
- Pregnancy
- Prior surgery in the neck or infraclavicular region
- Chronic pain syndromes requiring opioid intake at home
Sites / Locations
- Hospital Clínico Universidad de Chile
Arms of the Study
Arm 1
Arm 2
Arm Type
Active Comparator
Experimental
Arm Label
Interscalene Block
Infraclavicular-Anterior Supraescapular Nerve Blocks
Arm Description
Patients randomized to receive an interscalene block.
Patients randomized to receive a combined infraclavicular plus anterior suprascapular nerve blocks.
Outcomes
Primary Outcome Measures
Static pain 30 minutes after arrival in the post anesthesia care unit (PACU)
Pain intensity at rest using a numeric rating score (NRS) ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Secondary Outcome Measures
Static pain 1 hour after arrival in the PACU
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Static pain 3 hours after arrival in the PACU
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Static pain 6 hours after arrival in the PACU
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Static pain 12 hours after arrival in the PACU
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Static pain 24 hours after arrival in the PACU
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Static pain 36 hours after arrival in the PACU
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Static pain 48 hours after arrival in the PACU
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Block performance time
Time from skin disinfection until the end of local anesthetic injection
Intensity of pain during block procedure
Evaluated with the Numeric Rating Scale for Pain. This scale is graduated from 0 to 10 points. A 0-point score represents the absence of pain, and a 10-points score represents the worst imaginable pain. Patients will be asked to rate their pain verbally with this scale. The blinded assessor will register the score reported.
Incidence of nerve block side effects
Determined by the presence of paresthesia, local anesthetic systemic toxicity, vascular puncture, Horner syndrome, or hoarseness after the block.
Sensory and motor block score
The sensorimotor block will be assessed every 5 minutes until 30 minutes after the end of local anesthetic injection using a 14-point composite score that encompasses the sensory functions of the axillary and supraclavicular nerves as well as the motor functions of the axillary, suprascapular, subscapular and lateral pectoral nerves
Sensation will be assessed with ice in each nerve territory with a 0 to 2 point scale. 0= no block, patients can feel cold; 1= analgesic block, the patient can feel touch but not cold; 2= anesthetic block, the patient cannot feel cold or touch.
The motor function will be assessed for each nerve with a 0 to 2 points scale where 0= no motor block; 1= paresis; 2= paralysis.
Successful blocks at 30 minutes correlate with a final score ( sum of all individual sensory and motor scores) of at least 12 points out of 14, with a sensory score of at least 3 points (out of 4 points).
Block onset time
Time required to reach a minimal sensorimotor composite score of 12 points out of a maximum of 14 points. The sensorimotor score is described in outcome 12.
Basal diaphragmatic function
Diaphragmatic function evaluated before the nerve block
Incidence of hemidiaphragmatic paralysis (HDP) at 30 minutes after interscalene or infraclavicular-suprascapular block
HDP will be defined as the absence of diaphragmatic motion during normal respiration coupled with absent or (paradoxical) cranial diaphragmatic movement when the patient forcefully sniffs
Incidence of HDP 30 minutes after PACU arrival
HDP will be defined as the absence of diaphragmatic motion during normal respiration coupled with absent or (paradoxical) cranial diaphragmatic movement when the patient forcefully sniffs
Duration of surgery
Time between skin incision and closure (min)
Postoperative opioid related side effects
Presence of postoperative nausea, vomiting, pruritus, urinary retention, respiratory depression.
Intraoperative opioid requirements
Total amount of fentanyl required during general anesthesia
Postoperative opioid consumption
Total amount of morphine required during the first 48 hours after surgery
Patient satisfaction
Patient satisfaction at 24 hours using a 0-10 scale (0 = not satisfied; 10 = very satisfied)
Persistent neurologic deficit
Presence of persistent sensory or motor postoperative deficit. The patients will be contacted by telephone and inquired about any sensory or motor deficit in the operated extremity.
Full Information
1. Study Identification
Unique Protocol Identification Number
NCT05444517
Brief Title
Interscalene Block Versus Combined Infraclavicular-Anterior Suprascapular Blocks for Shoulder Surgery
Official Title
A Randomized Comparison Between Interscalene And Combined Infraclavicular-Anterior Suprascapular Nerve Blocks For Arthroscopic Shoulder Surgery
Study Type
Interventional
2. Study Status
Record Verification Date
May 2023
Overall Recruitment Status
Not yet recruiting
Study Start Date
May 2023 (Anticipated)
Primary Completion Date
December 2023 (Anticipated)
Study Completion Date
December 2023 (Anticipated)
3. Sponsor/Collaborators
Responsible Party, by Official Title
Principal Investigator
Name of the Sponsor
University of Chile
4. Oversight
Studies a U.S. FDA-regulated Drug Product
No
Studies a U.S. FDA-regulated Device Product
No
Data Monitoring Committee
Yes
5. Study Description
Brief Summary
Postoperative analgesia after shoulder surgery remains a challenge in patients with preexisting pulmonary pathology, as interscalene brachial plexus block (ISB), the standard nerve block for shoulder surgery, carries a prohibitive risk of hemidiaphragmatic paralysis (HDP). Although several diaphragm-sparing nerve blocks have been proposed, none seems to offer equivalent analgesia to ISB while avoiding HDP altogether. For instance, even costoclavicular blocks, which initially fulfilled both requirements, were subsequently found to result in a non-negligible 5%-incidence of HDP.
In this randomized trial, the authors set out to compare ISB and combined infraclavicular block-anterior suprascapular nerve blocks (ICB-ASSNB) for patients undergoing arthroscopic shoulder surgery. The authors hypothesized that ICB-ASSNB would provide equivalent postoperative analgesia to ISB 30 minutes after shoulder surgery and therefore designed the current study as an equivalence trial.
6. Conditions and Keywords
Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study
Pain, Postoperative, Shoulder Pain, Surgical Procedure, Unspecified, Diaphragmatic Paralysis
Keywords
Postoperative Shoulder Analgesia, Diaphragmatic Paralysis, Alternative Blocks
7. Study Design
Primary Purpose
Supportive Care
Study Phase
Not Applicable
Interventional Study Model
Parallel Assignment
Masking
Outcomes Assessor
Allocation
Randomized
Enrollment
50 (Anticipated)
8. Arms, Groups, and Interventions
Arm Title
Interscalene Block
Arm Type
Active Comparator
Arm Description
Patients randomized to receive an interscalene block.
Arm Title
Infraclavicular-Anterior Supraescapular Nerve Blocks
Arm Type
Experimental
Arm Description
Patients randomized to receive a combined infraclavicular plus anterior suprascapular nerve blocks.
Intervention Type
Procedure
Intervention Name(s)
Interscalene Block
Other Intervention Name(s)
Peripheral Nerve Block
Intervention Description
Ultrasound-guided brachial plexus block injecting 20 ml of bupivacaine 0.5% plus epinephrine 5 micrograms per ml in the Interscalene groove.
Patients will receive dexamethasone 4 mg intravenously and an ultrasound-guided intermediate cervical plexus block (5 ml of bupivacaine 0.5% plus epinephrine 5 micrograms per ml).
Intervention Type
Procedure
Intervention Name(s)
Infraclavicular - Anterior Supraescapular Nerve Blocks
Other Intervention Name(s)
Peripheral Nerve Block
Intervention Description
Ultrasound-guided combined infraclavicular-anterior suprascapular block of the brachial plexus, injecting 20 ml of bupivacaine 0.5% plus epinephrine 5 micrograms per ml dorsal to the axillary artery in the infraclavicular fossa plus an ultrasound-guided injection of 3 ml of bupivacaine 0.5% plus epinephrine 5 micrograms per ml under the omohyoid muscle. If the anterior suprascapular nerve could not be identified after five minutes of insonation time, an upper trunk block will be carried out with the same amount of local anesthetic.
Patients will receive dexamethasone 4 mg intravenously and an ultrasound-guided intermediate cervical plexus block (5 ml of bupivacaine 0.5% plus epinephrine 5 micrograms per ml).
Primary Outcome Measure Information:
Title
Static pain 30 minutes after arrival in the post anesthesia care unit (PACU)
Description
Pain intensity at rest using a numeric rating score (NRS) ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
30 minutes after PACU arrival
Secondary Outcome Measure Information:
Title
Static pain 1 hour after arrival in the PACU
Description
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
1 hour after PACU arrival
Title
Static pain 3 hours after arrival in the PACU
Description
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
3 hours after PACU arrival
Title
Static pain 6 hours after arrival in the PACU
Description
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
6 hours after PACU arrival
Title
Static pain 12 hours after arrival in the PACU
Description
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
12 hours after PACU arrival
Title
Static pain 24 hours after arrival in the PACU
Description
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
24 hours after PACU arrival
Title
Static pain 36 hours after arrival in the PACU
Description
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
36 hours after PACU arrival
Title
Static pain 48 hours after arrival in the PACU
Description
Pain intensity at rest using a NRS ranged from 0 to 10 (0 = no pain and 10 = worst imaginable pain)
Time Frame
48 hours after PACU arrival
Title
Block performance time
Description
Time from skin disinfection until the end of local anesthetic injection
Time Frame
1 hour before surgery
Title
Intensity of pain during block procedure
Description
Evaluated with the Numeric Rating Scale for Pain. This scale is graduated from 0 to 10 points. A 0-point score represents the absence of pain, and a 10-points score represents the worst imaginable pain. Patients will be asked to rate their pain verbally with this scale. The blinded assessor will register the score reported.
Time Frame
1 hour before surgery
Title
Incidence of nerve block side effects
Description
Determined by the presence of paresthesia, local anesthetic systemic toxicity, vascular puncture, Horner syndrome, or hoarseness after the block.
Time Frame
0 minutes after skin disinfection to 30 minutes after the nerve block
Title
Sensory and motor block score
Description
The sensorimotor block will be assessed every 5 minutes until 30 minutes after the end of local anesthetic injection using a 14-point composite score that encompasses the sensory functions of the axillary and supraclavicular nerves as well as the motor functions of the axillary, suprascapular, subscapular and lateral pectoral nerves
Sensation will be assessed with ice in each nerve territory with a 0 to 2 point scale. 0= no block, patients can feel cold; 1= analgesic block, the patient can feel touch but not cold; 2= anesthetic block, the patient cannot feel cold or touch.
The motor function will be assessed for each nerve with a 0 to 2 points scale where 0= no motor block; 1= paresis; 2= paralysis.
Successful blocks at 30 minutes correlate with a final score ( sum of all individual sensory and motor scores) of at least 12 points out of 14, with a sensory score of at least 3 points (out of 4 points).
Time Frame
30 minutes after the ending time of local anesthetic injection
Title
Block onset time
Description
Time required to reach a minimal sensorimotor composite score of 12 points out of a maximum of 14 points. The sensorimotor score is described in outcome 12.
Time Frame
1 hour before surgery
Title
Basal diaphragmatic function
Description
Diaphragmatic function evaluated before the nerve block
Time Frame
1 hour before surgery
Title
Incidence of hemidiaphragmatic paralysis (HDP) at 30 minutes after interscalene or infraclavicular-suprascapular block
Description
HDP will be defined as the absence of diaphragmatic motion during normal respiration coupled with absent or (paradoxical) cranial diaphragmatic movement when the patient forcefully sniffs
Time Frame
30 minutes after the ending time of local anesthetic injection
Title
Incidence of HDP 30 minutes after PACU arrival
Description
HDP will be defined as the absence of diaphragmatic motion during normal respiration coupled with absent or (paradoxical) cranial diaphragmatic movement when the patient forcefully sniffs
Time Frame
30 minutes after PACU arrival
Title
Duration of surgery
Description
Time between skin incision and closure (min)
Time Frame
4 hours after skin incision
Title
Postoperative opioid related side effects
Description
Presence of postoperative nausea, vomiting, pruritus, urinary retention, respiratory depression.
Time Frame
48 hours after PACU arrival
Title
Intraoperative opioid requirements
Description
Total amount of fentanyl required during general anesthesia
Time Frame
Intraoperative period
Title
Postoperative opioid consumption
Description
Total amount of morphine required during the first 48 hours after surgery
Time Frame
48 hours after PACU arrival
Title
Patient satisfaction
Description
Patient satisfaction at 24 hours using a 0-10 scale (0 = not satisfied; 10 = very satisfied)
Time Frame
24 hours after PACU arrival
Title
Persistent neurologic deficit
Description
Presence of persistent sensory or motor postoperative deficit. The patients will be contacted by telephone and inquired about any sensory or motor deficit in the operated extremity.
Time Frame
7 days after surgery
10. Eligibility
Sex
All
Minimum Age & Unit of Time
18 Years
Maximum Age & Unit of Time
80 Years
Accepts Healthy Volunteers
No
Eligibility Criteria
Inclusion Criteria:
Patients undergoing arthroscopic shoulder surgery
American Society of Anesthesiologists classification 1-3
Body mass index between 20 and 35 kg/mt2
Exclusion Criteria:
Adults who are unable to give their own consent
Pre-existing neuropathy (assessed by history and physical examination)
Coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. platelets ≤ 100, International Normalized Ratio ≥ 1.4 or prothrombin time ≥ 50)
Obstructive or restrictive pulmonary disease (assessed by history and physical examination)
Renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. creatinine ≥ 100)
Hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. transaminases ≥ 100)
Allergy to local anesthetics (LAs)
Pregnancy
Prior surgery in the neck or infraclavicular region
Chronic pain syndromes requiring opioid intake at home
Central Contact Person:
First Name & Middle Initial & Last Name or Official Title & Degree
Julián Aliste, MD
Phone
+56229788221
Email
julian.aliste@uchile.cl
Overall Study Officials:
First Name & Middle Initial & Last Name & Degree
Julián Aliste, MD
Organizational Affiliation
University of Chile
Official's Role
Principal Investigator
Facility Information:
Facility Name
Hospital Clínico Universidad de Chile
City
Santiago
State/Province
Metropolitana
Country
Chile
Facility Contact:
First Name & Middle Initial & Last Name & Degree
Julián Aliste, MD
12. IPD Sharing Statement
Citations:
PubMed Identifier
27941477
Citation
Tran DQ, Elgueta MF, Aliste J, Finlayson RJ. Diaphragm-Sparing Nerve Blocks for Shoulder Surgery. Reg Anesth Pain Med. 2017 Jan/Feb;42(1):32-38. doi: 10.1097/AAP.0000000000000529.
Results Reference
background
PubMed Identifier
31541010
Citation
Tran DQ, Layera S, Bravo D, Cristi-Sanchez I, Bermudez L, Aliste J. Diaphragm-sparing nerve blocks for shoulder surgery, revisited. Reg Anesth Pain Med. 2019 Sep 20:rapm-2019-100908. doi: 10.1136/rapm-2019-100908. Online ahead of print.
Results Reference
background
PubMed Identifier
30635497
Citation
Aliste J, Bravo D, Layera S, Fernandez D, Jara A, Maccioni C, Infante C, Finlayson RJ, Tran DQ. Randomized comparison between interscalene and costoclavicular blocks for arthroscopic shoulder surgery. Reg Anesth Pain Med. 2019 Jan 11:rapm-2018-100055. doi: 10.1136/rapm-2018-100055. Online ahead of print.
Results Reference
background
PubMed Identifier
31397702
Citation
Sivashanmugam T, Maurya I, Kumar N, Karmakar MK. Ipsilateral hemidiaphragmatic paresis after a supraclavicular and costoclavicular brachial plexus block: A randomised observer blinded study. Eur J Anaesthesiol. 2019 Oct;36(10):787-795. doi: 10.1097/EJA.0000000000001069.
Results Reference
background
PubMed Identifier
12606927
Citation
Martinez J, Sala-Blanch X, Ramos I, Gomar C. Combined infraclavicular plexus block with suprascapular nerve block for humeral head surgery in a patient with respiratory failure: an alternative approach. Anesthesiology. 2003 Mar;98(3):784-5. doi: 10.1097/00000542-200303000-00031. No abstract available.
Results Reference
background
PubMed Identifier
29270914
Citation
Aliste J, Bravo D, Finlayson RJ, Tran DQ. A randomized comparison between interscalene and combined infraclavicular-suprascapular blocks for arthroscopic shoulder surgery. Can J Anaesth. 2018 Mar;65(3):280-287. doi: 10.1007/s12630-017-1048-0. Epub 2017 Dec 19.
Results Reference
background
PubMed Identifier
18262803
Citation
Vorster W, Lange CP, Briet RJ, Labuschagne BC, du Toit DF, Muller CJ, de Beer JF. The sensory branch distribution of the suprascapular nerve: an anatomic study. J Shoulder Elbow Surg. 2008 May-Jun;17(3):500-2. doi: 10.1016/j.jse.2007.10.008. Epub 2008 Feb 11.
Results Reference
background
PubMed Identifier
21194975
Citation
Ebraheim NA, Whitehead JL, Alla SR, Moral MZ, Castillo S, McCollough AL, Yeasting RA, Liu J. The suprascapular nerve and its articular branch to the acromioclavicular joint: an anatomic study. J Shoulder Elbow Surg. 2011 Mar;20(2):e13-7. doi: 10.1016/j.jse.2010.09.004. Epub 2010 Dec 30.
Results Reference
background
PubMed Identifier
28776638
Citation
Musso D, Flohr-Madsen S, Meknas K, Wilsgaard T, Ytrebo LM, Klaastad O. A novel combination of peripheral nerve blocks for arthroscopic shoulder surgery. Acta Anaesthesiol Scand. 2017 Oct;61(9):1192-1202. doi: 10.1111/aas.12948. Epub 2017 Aug 4.
Results Reference
background
PubMed Identifier
20975470
Citation
Tran DQ, Dugani S, Finlayson RJ. A randomized comparison between ultrasound-guided and landmark-based superficial cervical plexus block. Reg Anesth Pain Med. 2010 Nov-Dec;35(6):539-43. doi: 10.1097/AAP.0b013e3181faa11c.
Results Reference
background
PubMed Identifier
29630033
Citation
Aliste J, Bravo D, Fernandez D, Layera S, Finlayson RJ, Tran DQ. A Randomized Comparison Between Interscalene and Small-Volume Supraclavicular Blocks for Arthroscopic Shoulder Surgery. Reg Anesth Pain Med. 2018 Aug;43(6):590-595. doi: 10.1097/AAP.0000000000000767.
Results Reference
background
PubMed Identifier
21568985
Citation
Spence BC, Beach ML, Gallagher JD, Sites BD. Ultrasound-guided interscalene blocks: understanding where to inject the local anaesthetic. Anaesthesia. 2011 Jun;66(6):509-14. doi: 10.1111/j.1365-2044.2011.06712.x.
Results Reference
background
PubMed Identifier
27203394
Citation
Franco CD, Williams JM. Ultrasound-Guided Interscalene Block: Reevaluation of the "Stoplight" Sign and Clinical Implications. Reg Anesth Pain Med. 2016 Jul-Aug;41(4):452-9. doi: 10.1097/AAP.0000000000000407.
Results Reference
background
PubMed Identifier
20048654
Citation
Tran DQ, Bertini P, Zaouter C, Munoz L, Finlayson RJ. A prospective, randomized comparison between single- and double-injection ultrasound-guided infraclavicular brachial plexus block. Reg Anesth Pain Med. 2010 Jan-Feb;35(1):16-21. doi: 10.1097/AAP.0b013e3181c7717c.
Results Reference
background
PubMed Identifier
34083356
Citation
Maikong N, Kantakam P, Sinthubua A, Mahakkanukrauh P, Tran Q, Leurcharusmee P. Cadaveric study investigating the phrenic-sparing volume for anterior suprascapular nerve block. Reg Anesth Pain Med. 2021 Sep;46(9):769-772. doi: 10.1136/rapm-2021-102803. Epub 2021 Jun 3.
Results Reference
background
PubMed Identifier
27956682
Citation
Aguirre O, Tobos L, Reina MA, Sala-Blanch X. Upper trunk block: description of a supraclavicular approach of upper trunk at the points of its division. Br J Anaesth. 2016 Dec;117(6):823-824. doi: 10.1093/bja/aew366. No abstract available.
Results Reference
background
PubMed Identifier
31892544
Citation
Aliste J, Cristi-Sanchez I, Bermudez L, Layera S, Bravo D, Tran Q. Assessing surgical anesthesia for shoulder surgery. Reg Anesth Pain Med. 2020 Aug;45(8):675-676. doi: 10.1136/rapm-2019-100981. Epub 2019 Dec 31. No abstract available.
Results Reference
background
PubMed Identifier
16331304
Citation
Lloyd T, Tang YM, Benson MD, King S. Diaphragmatic paralysis: the use of M mode ultrasound for diagnosis in adults. Spinal Cord. 2006 Aug;44(8):505-8. doi: 10.1038/sj.sc.3101889. Epub 2005 Dec 6.
Results Reference
background
PubMed Identifier
19535272
Citation
Tashjian RZ, Deloach J, Porucznik CA, Powell AP. Minimal clinically important differences (MCID) and patient acceptable symptomatic state (PASS) for visual analog scales (VAS) measuring pain in patients treated for rotator cuff disease. J Shoulder Elbow Surg. 2009 Nov-Dec;18(6):927-32. doi: 10.1016/j.jse.2009.03.021. Epub 2009 Jun 16.
Results Reference
background
Learn more about this trial
Interscalene Block Versus Combined Infraclavicular-Anterior Suprascapular Blocks for Shoulder Surgery
We'll reach out to this number within 24 hrs