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Abstract
Introduction The pericapsular nerve group (PENG) block is a novel regional technique indicated for analgesia for hip joint pain. We administered PENG blocks and performed catheter insertion for continuous infusions in patients with femur fractures on hospital admission. In this case series, we describe our initial experience of pain management in 10 patients with continuous infusion and its associated adverse events.
Case series The PENG block was administered with an introducer needle. The catheter was then inserted 3 cm beyond the needle tip. In three patients, blood aspiration through the catheter occurred. In each patient, the catheter was repositioned 0.5–1.0 cm more medially. No blood aspiration or visible hematoma occurred subsequently. The presence of any vascular structure deep to the iliopsoas muscle was excluded postoperatively based on a Doppler color flow scan.
Discussion Overall, eight patients had femoral neck fractures, and two patients had intertrochanteric fractures. All 10 patients reported good pain relief. The median (IQR) Numerical Rating Scale (NRS) score decreased from 7 (6–7) before the block to 2 (2–2.75) 20 min after PENG catheter placement. The median (IQR) NRS score after 12, 24 and 48 hours were 2 (2–3), 2 (2–3), and 2 (0.25–2), respectively. Patients underwent surgery 24–48 hours following catheter placement. Catheters were removed by an Acute Pain Service nurse 72 hours postinsertion. We want to highlight the potential for intravascular catheter placement in this anatomical region. Further studies are required to confirm if this is a technical error or an associated complication of continuous PENG blocks.
- continuous peripheral techniques
- lower extremity
- acute pain
- ultrasound in pain medicine
- regional anesthesia
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- continuous peripheral techniques
- lower extremity
- acute pain
- ultrasound in pain medicine
- regional anesthesia
Introduction
Regional anesthesia techniques are frequently used for preoperative pain management in patients with hip fractures. Femoral nerve blocks, fascia iliaca blocks, sciatic blocks and three-in-one blocks provide good analgesia and have an opioid-sparing effect. However, the obturator nerve is inconsistently covered by these blocks, while the accessory obturator nerve is not covered at all.
The pericapsular nerve group (PENG) block was recently described as an alternative technique for analgesia in hip fractures.1
Interest toward this novel technique has increased. There have been multiple reports of PENG blocks being successfully performed without major complications, although inadvertent femoral and obturator nerve blocks have also been reported.2 3
On the placement of peripheral nerve catheters for continuous PENG blocks, the literature is scarce. To date, there have been two papers that described this technique for postoperative analgesia.4 5 Accordingly, we used PENG blocks and catheter-delivered continuous infusions for pain management in patients with femur fractures.
In this case series, we describe our experience and pain management using continuous infusions for 10 patients as well as the complications encountered.
Case report
All patients included in our series or their next-of-kin provided verbal consent for anonymous data recording and sharing in relation to this procedure.
We describe the management of 10 cases (eight femoral neck fractures and two intertrochanteric fractures) with a catheter continuous infusion PENG block. Table 1 summarizes patient characteristics.
Patient’s characteristics and observed outcomes
On arrival to the emergency department, following orthopedic evaluation, patients were examined by an anesthetic team. Suitability of block performance was assessed, and informed consent was obtained following a risk–benefit discussion with the patients or their next of kin. All patients were evaluated for block suitability with regard to anticoagulant and antithrombotic therapies as per the current recommendations. Except for low-dose aspirin and prophylactic dose low-molecular-weight heparin, no other clotting altering therapies were recorded.
Subsequently, the PENG block and catheter placement were performed with the aseptic technique under ultrasound guidance. Before the procedure, all patients reported a median (IQR) pain score of 7 (6–7) in the absence of intravenous rescue analgesia (pain score measured with the 0–10 Numerical Rating Scale (NRS)). No premedication or sedation was administered before block performance.
For all cases, a catheter-through-needle kit was used (Contiplex Tuohy, B. Braun Melsungen, Germany) with a 10 cm long/18 G Tuohy introducer needle and a 0.45 × 0.85 × 1000 mm catheter. The anatomical landmarks and technique used were the same as the ones described by Girón-Arango et al.1
Once the introducer needle was placed on the target (figure 1) in the plane between the iliopsoas tendon and periosteum and between the anterior inferior iliac spine (AIIS) and iliopubic eminence (IPE), the PENG block was performed by injecting 20 mL of the local anesthetic. The local anesthetic used consisted of ropivacaine 0.375% (nine patients) or lidocaine 0.5% (one patient). The catheter was then inserted 3 cm beyond the needle tip into the hydrodissected plane, and an injection/aspiration test with saline was performed (figure 2, left).
Needle path for the PENG block. The catheter is inserted for 3 cm beyond the needle tip. AIIS, anterior inferior iliac spine; arrow, needle; FA, femoral artery; FV, femoral vein; IPE, iliopubic eminence; IPM, iliopsoas muscle; IPT, iliopsoas tendon.
Left: color Doppler scan of an injection through a correctly placed catheter. Right: external catheter fixation with cyanoacrylate glue, sterile strips and transparent semipermeable adhesive film dressing.
If the test was negative for blood, the catheter was fixed externally with cyanoacrylate glue, sterile strips and transparent semipermeable adhesive film dressing (figure 2, right). After fixation, a 5 mL/hour infusion of ropivacaine 0.2% was started via an elastomeric pump and continued for 72 hours after catheter placement. No adjuvants were added.
All patients reported good pain relief postblockade with a decrease in the median (IQR) NRS score from 7 (6–7) to 2 (2–2.75) 20 min after PENG catheter placement. The median (IQR) NRS scores after 12, 24 and 48 hours were 2 (2–3), 2 (2–3), and 2 (0.25–2), respectively.
We used the Wilcoxon signed-rank test to compare the repeated pain score measurements before and 20 min after block execution. The difference in pain scores was statistically significant (p=0.002), despite the small sample size (figure 3).
Wilcoxon signed-rank test to compare the repeated pain scores measurements before and 20 min after block execution (p=0.002). Dots: NRS values. vertical lines: IQR. NRS, Numerical Rating Scale.
Patients underwent surgery between 24 and 48 hours after arrival, as per the institutional policy. The 48-hour NRS score was recorded postoperatively. Catheters were removed by an Acute Pain Service nurse 72 hours postinsertion. The multimodal analgesia regimen at our institution includes paracetamol 3 g/day intravenously, ketorolac 30 mg intravenously on request (maximum 90 mg/day) and tramadol 50 mg intravenously, as required (max 150 mg/day), if NRS score ≥5 after administering the non-steroidal anti-inflammatory drugs. No medication other than paracetamol was required.
Discussion
The PENG block targets the articular branches innervating the anterior hip capsule. We report the analgesic effect of this block on two intertrochanteric fractures and eight femoral neck fractures. In all cases, the continuous PENG block provided effective analgesia in both preoperative and postoperative periods. However, we encountered some technical difficulties.
First, regarding the equipment used, we observed that a catheter-through-needle kit with a Tuohy introducer was more suitable for catheter placement than a catheter-over-needle model. The catheter-through-needle kit allowed easier insertion of the catheter below the psoas tendon and above the periosteum in the hydrodissected plane, although a steep needle angle was used (figure 2, left). In contrast, when using a catheter-over-needle kit (E-Cath, Pajunk, Geisingen, Germany; Contiplex C, B. Braun Melsungen, Germany), the relatively steep needle angle and catheter tip facing the bone were the two main issues impeding its insertion in the proper plane.
The second obstacle is the novelty of this block. Since this is a recently described technique, the operator has to be familiar with both the PENG block and peripheral nerve catheter placement under ultrasound guidance. Another issue is potential catheter displacement due to self-removal in uncooperative patients, particularly the elderly, who were representative in our series. We did not encounter this problem in any of our cases but performed preventive triple fixation with cyanoacrylate glue, sterile strips and transparent semipermeable adhesive film dressing.
Our patients were continuously monitored by Acute Pain Service nurses for signs and symptoms of local anesthetic systemic toxicity (LAST), as per the hospital policy. No cases of LAST have been identified.
Our case series also demonstrated a complication. We recorded three cases of potential intravascular cannulation when we performed aspiration via the catheter. In all three cases, blood was autofilling the catheter along with the attached syringe.
Intrafemoral artery placement is unlikely because the femoral artery is usually more than 3 cm away from the needle tip. It is also unlikely for intravenous placement because the catheter fills quickly with blood without aspiration.
The psoas bursa is an avascular plane, except in the situation of a hot inflamed bursitis (in which case the Doppler could be positive because of hyperaemia in the peribursal soft-tissues). In our series, the presence of vascular structures deep to the iliopsoas muscle was excluded postoperatively based on a color Doppler scan. However, blood vessels, if any, crossing this fascial plane should not have a wide enough lumen to allow inadvertent cannulation.
In all three cases, after blood backflow, the catheter was removed, and the puncture was repeated with the needle tip repositioned 0.5–1 cm more medially. The catheter was rethreaded 3 cm beyond the needle tip, and an aspiration test was performed with no blood backflow.
The reason for a more medial insertion point for the second time was to allow a more medial catheter placement between AIIS and IPE. The first puncture site was in close proximity to AIIS, rather than IPE.
One possible explanation for blood aspiration via the catheter in the absence of identifiable vascular structures could be the presence of blood collection with dilution of local anesthetics spreading cranially through the iliopsoas bursa. This bursa lies closer to the base of the femoral triangle between the psoas tendon and the anterior surface of the femoral neck. In adults, the psoas bursa communicates with the hip joint in approximately 15% of the cases and can therefore be a pathway for intra-articular hematoma spread.6–9 To simplify, there could be enlargement of the psoas bursa because of blood collection after the facture. This hypothesis could explain the negative aspiration test after catheter repositioning because the psoas bursa would be located more laterally. Scanning of the area could not reveal hematoma, as it is not hematoma but blood collection in the bursa with dilution of the local anesthetic. Therefore, it can be compressed with ultrasound probe positioning.
Another hypothesis is that the trauma causing the fracture led to the formation of an iliopsoas muscle hematoma.
In both scenarios, the needle tip could have just slightly pierced the posterior fascial layer of the iliopsoas muscle or bursa to allow plane hydrodissection as well as a negative aspiration test. On needle withdrawal, advancement of the catheter could have pushed the soft tip distally within the collection. Relocation to a medial direction potentially moved the catheter outside the bursa.
There was no clinically visible hematoma in any of the three cases. Eventually, no femoral or obturator nerve block was recorded.
In conclusion, we would like to raise awareness about potential intra-vascular catheter placement in this anatomical region giving a limited experience with PENG blocks. Further studies are required to assess if this is a technical error or a potential associated complication of this block.
Footnotes
Contributors RDB: block execution, acquisition of data, drafting and revision of manuscript. EP: block execution, acquisition of data, critical revision of manuscript. GP: revision of manuscript. CGS: revision of manuscript, language editing. EB: critical revision, supervisor.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.