PENG block: Advantages of out-of-plane approach.

Sir

We have read with interest the article 'Pericapsular nerve group (PENG) block: A feasibility study of landmark based technique,' by Jadon et al.[1] We want to congratulate them, as feasibility and safety of a landmark technique will contribute to a widespread use of this block[2] in situations of low ultrasound availability. They performed 4 of 10 blocks under ultrasound guidance in an out-of-plane approach, leading to optimal analgesia. According to our experience,[3] several advantages arise with this approach.

Some precautions should be considered in pericapsular nerve group (PENG) block. Proximity to the femoral vessels and nerve should preclude to medial-to-lateral injection. The tip of the needle should not be placed in the medial aspect of the psoas tendon due to the proximity of urinary viscera or obturator nerve.[4] Lateral femoral cutaneous nerve injury should also be avoided,[5] as it is usually located close to the prick point. An out-of-plane technique would minimise the chance of unintentional harm, as the prick is given more medial and needle tip is directed to an outer zone of iliac bony edge.

A preliminary scan can easily discard anatomical abnormalities, minimising the chance of unintentional damage, as the whole path of needle cannot be seen with this approach. It could also be a better alternative when high-quality ultrasound equipment is unavailable, as the identification of the whole needle is not necessary.

PENG block efficacy was corroborated by our group using an 'in-plane' approach, showing less opioid consumption after total hip replacement. Based on our recent experience, we suggest an 'out-of-plane' approach as a quicker and potentially safer alternative.

PENG block was performed in 38 patients. Approach was chosen according to the preference of the anaesthetist. We measured the time needed to block performance, including preliminary scan, and morphine consumption. No neurologic or vascular damage was detected [Table 1].

Table 1

Statistical data

	Out-of-plane approach PENG (n=21)	In-plane approach PENG (n=17)
Sex (male:female ratio)	11:10	7:10
Age (range, mean)	60-89, 73	46-87, 71
Surgery indication (n)
Coxarthrosis	15	11
Fracture	5	3
Other	1	3
Local anaesthetic*
Mean volume (mL)	20	20
Concentration (%) (range, mean)	0.25-0.5, 0.34	0.25-0.5, 0.36
Mean time to perform PENG block (seconds)	53	84
Mean morphine usage in PACU† (mg)	1.77	1.64
Patients requiring morphine in 48 h (%)	4.7	11.7
Nausea or vomiting requiring IV medication (%)	9.5	17.64

*Plain levobupivacaine (all cases), †Post Anaesthesia Care Unit

Several disadvantages should be considered. Out-of-plane blocks are usually difficult in unexperienced hands and catheter placement could be more difficult.

To sum up, 'out-of-plane' approach [Figure 1] carries benefits like a quicker technique. It could also be a safer choice, although further studies are needed to determine it.

Figure 1

Out-of-plane PENG block scheme (a). Out-of-plane PENG block: sonographic image (b and c). (1) Pectineus muscle, (2) inguinal ligament, (3) femoral vein, (4) femoral artery, (5) iliopectineal bursa, (6) iliopectineal eminence, (7) psoas tendon, (8) femoral nerve, (9) genitofemoral nerve, (10) anteroinferior iliac spine and (11) lateral femoral cutaneous nerve. Arrows in (b): needle tip. Arrow in (c): needle trajectory

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Conflicts of interest

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