Article: Mohanty, C. R., Varghese, J. J., Panda, R., Sahoo, S., Mishra, T. S., Radhakrishnan, R. V., Topno, N., Hansda, U., Shaji, I. M., & Behera, S. H. P. (2023). Ultrasound-guided selective peripheral nerve block compared with the sub-dissociative dose of ketamine for analgesia in patients with extremity injuries. The American Journal of Emergency Medicine, 63, 94–10. PMID: 36332503
Question: In adult trauma patients with isolated extremity injuries, do peripheral nerve blocks, compared to sub-dissociative ketamine, result in a reduction of pain by the numerical scale rating of at least 3 points?
What They Did:
- Design: Prospective, open-label, randomized clinical trial
- Site: Tertiary care emergency department in Eastern India
- Duration: October 19, 2020 to September 29, 2021
- Patients
- Patients were randomly assigned to the PNB or SDK group.
- The PNB group received peripheral ultrasound-guided nerve block(s) while the SDK group received 0.3 mg/kg of ketamine.
- In the PNB group, Ropivacaine 0.375% was used to perform a PNB of the upper or lower extremity, depending on the patient’s injury.
- The SDK group received ketamine with 100ml of normal saline infused over 10 minutes.
- Investigators measured the numerical rating scale (NRS) at baseline, followed by 30 min, 60 min, 120 min, 180 min, and 240 min post-intervention.
- Trial Registry: Clinical Trial Registry of India (CTRI/2020/10/028290; dated 8/10/2020)
Population:
Inclusion Criteria:
- Patients aged 18-65 years with traumatic musculoskeletal injuries to upper or lower extremities
- A pain score of >5 on the numerical rating scale (NRS)
Exclusion Criteria:
- Extremity injuries involving more than one limb
- Coagulopathy
- Confirmed nerve injury
- Active hemorrhage
- Known allergy to local anesthetics
- Crushed injury with suspected compartment syndrome
- Received any analgesia before presenting to the ED
- Pregnant and lactating women
- Unstable vital signs
- Altered mental status
Intervention:
- Patients with upper extremity injuries received musculocutaneous (lateral cutaneous nerve of the forearm), median, radial, and/or ulnar nerve blocks.
- Patients with lower extremity injuries received a block of femoral (saphenous nerve), popliteal-sciatic, superficial peroneal, tibial, and/or deep peroneal nerve blocks.
- The anesthetic for the blocks used was Ropivacaine 0.375%. 8-10 ml of the drug was used for femoral and popliteal-sciatic nerve blocks, while 2-5ml was used for all other PNBs.
Comparator:
- Subdissociative ketamine (0.3mg/kg) with 100ml of normal saline infused over 10 minutes.
Outcomes:
Primary Outcome: A reduction in pain by at least 3 points on the NRS without rescue analgesia at 30 minutes.
Secondary Outcomes:
- The need for rescue analgesia (given during the observation period if the patient reported a pain score of >5 on the NRS after the interventions. Fentanyl (1 μg/kg) was used as rescue analgesia.)
- Any adverse events
- Patient satisfaction in either arm
Results:
Study Characteristics:
- 198 people were assessed for eligibility
- 78 were excluded
- 120 were randomized
- 60 allocated to the PNB group
- 60 allocated to the SDK group
- The median age of the patients in the PNB and SDK groups was 31.5 and 35.0 years respectively.
- The baseline NRS score was comparable between both groups with PNB at 7.59 and SDK at 7.27 [-0.27 – 0.649,0.106].
Primary Outcome:
- The NRS score was significantly lower in the PNB group compared to the SDK group at 30, 60, 120, 180, and 240 minutes post-intervention
- All patients in the PNB group exhibited primary outcome (NRS ≥3 reductions) at 30 min post-intervention compared with 65% in the SDK group (35 patients).
- The decrease in NRS score from baseline at 30 minutes was higher in the PNB group compared to the SDK group [-2.166 (-2.640, – 1.692)]
- The maximum decrease in NRS score from baseline (-7) was observed at 120 mins in the PNB group compared to 180 minutes in the SDK group (-4.5).
Secondary Outcomes:
- Rescue analgesia was required in 10 (18%) of patients in the SDK group but in none in the PNB group.
- In the SDK group, 35 (64%) reported dizziness, and 15 (27%) reported nausea as side effects.
- None of the patients in the PNB group reported any complications.
- Three patients in the PNB group had motor weakness after the block.
Strengths:
- Randomized study design increases external validity.
- There was a clearly defined methodology.
- The primary outcome was patient-oriented
- A random computer sequence generator was used to allocate subjects to either arm of the study.
- The authors used a unique ID for each subject to maintain confidentiality, which helps to prevent unblinding for outcome assessment.
- The study used selective PNBs, which have advantages in the ED setting due to minimal motor blockade and the requirement for a smaller volume of local anesthetic agents.
- This study observed patients in the SDK group for 240 minutes post-intervention compared to previous studies that observed patients for <120 minutes.
- The emergency physician performing the PNB or administering the SDK was not the individual collecting the data on pain reduction.
Limitations:
- The study was performed at a single-center study in a tertiary care hospital. The results from single-center studies are not generalizable to all populations.
- The enrolled cohort represents a convenience sample, introducing the potential for selection bias.
- Opaque envelopes for allocation can be opened in advance, transilluminated, or manipulated, leading to unblinding.
- Patients and the physician performing the intervention were not blinded. However, it is also unclear whether data collectors were blinded.
- A successful nerve block requires reducing NRS to zero, which essentially mandates that PNB outperforms SDK.
- It is not clear what happened to patients who had an unsuccessful nerve block.
- The experience level of the physicians in this study may not be generalizable to ED physicians with less experience in nerve blocks.
- Investigators assessed outcomes up until 240 minutes post-intervention, but Ropivacaine can last >240 minutes (up to 6-12 hours), while Ketamine typically has a half-life of 150 minutes. Any differences in post-intervention side effects may be the result of measurement bias.
- Differences between the intervention groups in key variables such as gender, type, pattern, and mechanism of injury may affect the pain score among participants.
- The SKD group had more lower extremity injuries than upper extremity injuries.
- The PNB group has more upper extremity injuries than lower extremity injuries.
- PNB has more cut than blunt injuries.
- SDK had more blunt than cut injuries.
- Over 80% of the study participants are 30-year-old males, making generalizability to women and older patients difficult to assess.
Discussion:
Comparing a procedure to a medication is challenging. While both SDK and PNBs provide pain relief, their similarities end there. Although PNBs offer excellent pain control, not all providers possess the requisite experience and skill to perform the wide array of available blocks. Physicians with less experience in PNBs can more quickly administer SDK or other systemic analgesia. The lower side effect profile seen with PNBs in this study, at least partially, reflects the physicians’ extensive training in ultrasound-guided nerve blocks, limiting generalizability to less experienced providers. Novice providers might use more anesthetics, encounter higher adverse reactions, and achieve less analgesia.
PNBs also require specific equipment, such as an ultrasound, nerve block catheters, and intra-lipids in case of overdose, whereas SDK only requires a standard peripheral IV catheter. SDK can typically be administered faster than performing a PNB and requires fewer resources. Given these differences, further evaluation of factors like time to therapy, the number of PNB attempts to achieve analgesia, the procedure length, and the total duration of ED stay are needed.
Additionally, not all patients with traumatic injuries are candidates for the procedure, such as those with suspected compartment syndrome or nerve injury, patients with multiple limb injuries, or patients with non-limb injuries. This greatly narrows the pool of patients for whom peripheral nerve blocks are a viable option for analgesia.
Author’s Conclusion: “The study provides evidence that ultrasound-guided PNB is superior to SDK in terms of its analgesic efficacy in the management of acute pain due to extremity injuries and is associated with higher patient satisfaction. The need for rescue analgesia was significantly less in the PNB group. SDK was associated with a high incidence of dizziness and nausea.”
Our Conclusion:
This randomized clinical trial is the first to compare PNBs with SDK for analgesia. The findings indicate that PNBs can provide excellent pain control when administered by highly trained providers, though implementation requires careful consideration of provider experience and patient selection. However, the various limitations warrant further research to evaluate practical factors like time to therapy and resource requirements.
Clinical Bottom Line:
We recommend using PNBs for analgesia in patients with traumatic extremity injuries, but only if the physician has the requisite experience and expertise in performing these blocks. Additionally, careful patient selection is crucial to ensure safety and effectiveness.
References:
- Motov S, Mann S, Drapkin J, et al. Intravenous subdissociative-dose ketamine versus morphine for acute geriatric pain in the Emergency Department: A randomized controlled trial. Am J Emerg Med. 2019;37(2):220-227. PMID:29807629
- Beaudoin FL, Haran JP, Liebmann O. A comparison of ultrasound-guided three-in-one femoral nerve block versus parenteral opioids alone for analgesia in emergency department patients with hip fractures: a randomized controlled trial. Acad Emerg Med. 2013;20(6):584-591. PMID: 23758305
- Ahern TL, Herring AA, Miller S, Frazee BW. Low-Dose Ketamine Infusion for Emergency Department Patients with Severe Pain. Pain Med. 2015;16(7):1402-1409. PMID:25643741
For More Information, Check Out:
- NYSORA Upper and Lower Extremity Blocks
- Highland Ultrasound- Upper Extremity Blocks
- Highland Ultrasound- Lower Extremity Blocks
Guest Post By:
Ultrasound Fellow
Vassar Brothers Hospital, Poughkeepsie, New York
E-mail: Nicholas.Maenza@NuvanceHealth.org
Stephanie Midgley, MD, FPD-AEMUS, FACEP, DipABLM
Director of Clinical Ultrasound
Advanced Clinical Ultrasound Fellowship Director
Assistant Emergency Medicine Residency Program Director
Vassar Brothers Hospital, Poughkeepsie, New York
Twitter/X: @nuvancePOCUS
Marco Propersi, DO FAAEM
Vice-Chair, Emergency Medicine
Assistant Emergency Medicine Residency Program Director
Vassar Brothers Hospital, Poughkeepsie, New York
Twitter/X: @marco_propersi
Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter/X: @srrezaie)
