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Magnesium Sulfate in Adductor Canal Blocks

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT02581683
Recruitment Status : Completed
First Posted : October 21, 2015
Last Update Posted : July 8, 2019
Information provided by (Responsible Party):
Dr. Vidur Shyam, Queen's University

Brief Summary:
Proper analgesia after total knee arthroplasty (TKA) is important for encouraging early ambulation, which can facilitate improved patient outcomes and early hospital discharge. For pain control after TKA, adductor canal blocks (ACBs) improve upon the gold standard femoral nerve blocks (FNBs) since they do not cause as much quadriceps muscle weakening, while providing equivalent analgesia. Multimodal analgesia has become commonplace as a method of superior pain control with fewer side effects. Magnesium sulfate as an adjuvant to FNB local anesthetics can improve pain control after surgery; however, it also prolongs time to ambulation. There are no reports on the effect of magnesium sulfate in ACBs on analgesia after TKA. Thus the purpose of this randomized, double-blind, controlled trial is to determine whether magnesium sulfate given with local anesthetics via ACB can prolong analgesia, reduce pain scores and opioid consumption, and increase mobilization in TKA patients.

Condition or disease Intervention/treatment Phase
Knee Arthroplasty Drug: Magnesium Sulfate Drug: Ropivacaine Other: Sham Phase 4

Detailed Description:

Adequate analgesia after surgery is important for patient well-being, satisfaction, rapid recovery, and timely discharge. Due to our aging population, total knee arthroplasties (TKAs) are an increasingly common surgical procedure in Canada, with 57,718 performed in 2012-2013 alone. Improved functional outcomes and early hospital discharge are facilitated when patients ambulate within several hours of surgery. Early ambulation is enabled by good analgesia without concomitant muscle weakness or debilitating side effects associated with opioid consumption. Given the high volume of knee replacements, the need to ambulate early, and the importance of effective pain management, the development of new analgesia techniques for TKAs is an important endeavor to reduce hospital costs and improve the quality of life of a substantial number of patients.

In order to minimize adverse side effects while still providing adequate postoperative analgesia, many anesthesiologists now co-administer smaller doses of several different medications, which act additively or synergistically depending on their combined and varied mechanisms of action. Often these medications are given locally, either directly into the knee (periarticularly) or near the nerves innervating the knee, for example the femoral nerve block (FNB) or the adductor canal block (ACB).

FNBs, wherein local anesthetic medications are injected around the femoral nerve, are commonly used to manage pain following TKA. Although they assist in providing quality postoperative pain relief, FNBs are also associated with weakening of the quadriceps muscle, and an increased risk of falls. The ACB involves an injection of local anesthetics such as ropivacaine or bupivacaine into the adductor canal in the middle third of the thigh, which contains the sensory saphenous nerve. ACB is as effective as FNB at reducing postoperative pain in TKA patients. However, ACBs do not cause quadriceps weakening to the same extent as FNBs, and result in earlier recovery of ambulation after surgery compared to FNBs. Since ACBs produce less quadriceps weakening (due to their actions on sensory, rather than motor, nerves), this anesthetic technique may reduce the risk of falling in the postoperative period compared to FNBs; however, most studies are underpowered to detect this statistically.

Recent attention has been given to magnesium sulfate (MgSO4) as a supplement to improve and/or prolong local anesthesia postoperatively. MgSO4 is thought to reduce pain via antagonism of N-methyl-D-aspartate (NMDA) receptors. A local mechanism of action on peripheral rather than central NMDA receptors is supported by studies showing that despite providing pain relief, peripherally administered MgSO4 does not increase cerebrospinal fluid concentrations of magnesium, implying that it cannot cross the blood-brain barrier to enter the central nervous system.

In knee surgery patients, locally administered MgSO4 via the periarticular route reduces postoperative pain, reduces cumulative analgesic consumption, and prolongs analgesia. MgSO4 co-administered with local anesthetic via FNB in knee surgery patients reduces pain and postoperative analgesic consumption compared to local anesthetic alone; however, it also prolongs the time to ambulation, which could delay hospital discharge. Currently, there are no investigations into the analgesic efficacy of MgSO4 administered via ACB in TKA patients. Therefore, the purpose of this randomized controlled trial is to assess the duration of analgesia in TKA patients receiving ACBs with or without MgSO4. The investigators hypothesize that patients receiving MgSO4 will have prolonged analgesia, improved pain scores, and will be able to mobilize further, all of which will contribute to a shorter hospital length of stay in these patients.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 132 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
Official Title: Does Magnesium Sulfate as a Supplement in Adductor Canal Blocks Improve Pain Control After Total Knee Arthroplasty?
Study Start Date : September 2015
Actual Primary Completion Date : February 2017
Actual Study Completion Date : February 2017

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Knee Replacement

Arm Intervention/treatment
Experimental: Magnesium
Participants in this arm will receive magnesium sulfate + ropivacaine via adductor canal block
Drug: Magnesium Sulfate
Given via adductor canal block
Other Name: Sulfamag, Epsom salt, Health Canada DIN: 02139499

Drug: Ropivacaine
Given via adductor canal block
Other Name: Naropin

Active Comparator: Non-magnesium
Participants in this arm will receive ropivacaine via adductor canal block
Drug: Ropivacaine
Given via adductor canal block
Other Name: Naropin

Sham Comparator: Sham
Participants in this arm will receive a sham adductor canal block
Other: Sham
Sham adductor canal block

Primary Outcome Measures :
  1. Time to first analgesic request [ Time Frame: First occurrence during hospitalization (up to 72 hours postoperatively) ]
    Investigators will note the time lapsed between end of surgery and the first request for additional analgesia (given using patient controlled analgesia pumps, as is standard of care at the study institution).

Secondary Outcome Measures :
  1. Cumulative morphine consumption [ Time Frame: Cumulative dose during the first 24 postoperative hours ]
    Patient-controlled analgesia pumps allow the investigators to measure how much morphine each patient requests.

  2. Number of steps taken [ Time Frame: Number of steps taken during postoperative days 1 and 2 ]
    The investigators will record the number of steps each patient takes during postoperative days 1 and 2 in hospital.

  3. Pain [ Time Frame: 2, 4, 8, 12, and 24 hours after adductor canal injection (or sham) ]
    Pain scores will be assessed using a visual analog scale at each of the above times.

  4. Patient satisfaction [ Time Frame: Once, 24 hours after surgery ]
    Patients will rate their satisfaction with their analgesia using a scale from 1 to 5.

  5. Time to readiness for discharge [ Time Frame: Once, upon occurrence, within 72 hours after surgery ]
    The time at which each patient reaches the criteria for discharge readiness determined by physiotherapy using an assessment checklist will be recorded.

  6. Length of stay [ Time Frame: Once, within 72 hours after surgery ]
    The length of hospital stay after surgery will be recorded for each patient

  7. Side effects [ Time Frame: Upon occurrence, up to 72 hours after surgery ]
    The incidence (presence/absence) of morphine-related side effects such as nausea, vomiting, itching, and respiratory depression will be recorded.

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years to 85 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • American Society of Anesthesiologists classification score of 1 to 3
  • Presenting for unilateral primary total knee arthroplasty
  • age 18 to 85

Exclusion Criteria:

  • inability to use a patient-controlled analgesia pump
  • long-standing use of opioid medications (3 months or longer)
  • history of chronic pain syndromes
  • significant cardiovascular disease
  • medical conditions that preclude the use of a regional anesthetic technique or any of the study drugs
  • inability to read and understand English
  • incompetent to give consent to study participation
  • women who are pregnant or nursing

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT02581683

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Canada, Ontario
Kingston General Hospital
Kingston, Ontario, Canada, K7L2V7
Hotel Dieu Hospital
Kingston, Ontario, Canada, K7L5G2
Sponsors and Collaborators
Queen's University
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Principal Investigator: Vidur Shyam, MBBS, FRCPC Queen's University

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Responsible Party: Dr. Vidur Shyam, Assistant Professor, GFT, Queen's University Identifier: NCT02581683    
Other Study ID Numbers: ANAE-273-15
First Posted: October 21, 2015    Key Record Dates
Last Update Posted: July 8, 2019
Last Verified: July 2019
Additional relevant MeSH terms:
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Magnesium Sulfate
Anesthetics, Local
Central Nervous System Depressants
Physiological Effects of Drugs
Sensory System Agents
Peripheral Nervous System Agents
Anti-Arrhythmia Agents
Calcium Channel Blockers
Membrane Transport Modulators
Molecular Mechanisms of Pharmacological Action
Calcium-Regulating Hormones and Agents
Tocolytic Agents
Reproductive Control Agents