Resolving the Conflict Between Regional Analgesia and Developing Compartment Syndrome in Below-Knee Surgeries With the High-Volume Proximal Adductor Canal (Hi-PAC) Block: A Prospective Feasibility Study

Abstract

The consideration of regional analgesia (RA) in below-knee surgeries is always a controversial topic due to the fear of masking symptoms of developing compartment syndrome (CS) in the postoperative period. Compartment syndrome (CS) has been found frequently in below-knee surgeries, particularly among tibial diaphyseal fractures. Like any other surgery, below-knee surgeries have significant postoperative pain that requires effective postoperative analgesia protocol. The analgesia quality makes a big difference when compared with or without RA. Also, the presence or absence of RA cannot prevent or promote the development of CS. Therefore, patients should not be deprived of their right to remain pain-free in the postoperative period by compromising the analgesia protocol. The pain out of proportion to the surgery or injury is a typical symptom of developing CS, which can cause increased analgesic demands postoperatively. Timely diagnosis and treatment of CS require vigilant postoperative monitoring of the warning signs by trained staff. Avoiding RA for fear of presumed masking of symptoms and delaying CS diagnosis may not be a solution instead of choosing an appropriate RA with regular postoperative monitoring for such warning symptoms. The high-volume proximal adductor canal (Hi-PAC) block has been described as a procedure-specific and motor-sparing RA technique appropriate for below-knee surgeries. In this prospective study, we evaluated the analgesic efficacy of the Hi-PAC block in below-knee surgeries. We also observed the effect of the Hi-PAC block, due to proximal and distal drug distribution, on masking the symptoms of the developing CS during postoperative monitoring. We found the Hi-PAC block to be a safer and more effective RA alternative for below-knee surgeries with an added motor-sparing benefit that facilitated early mobility and discharge. Its property of not interfering with postoperative surveillance to detect the symptoms of CS and intervene in time helps deal with the anxiety of CS in below-knee surgeries.

Keywords: below-knee surgeries; compartment syndrome; foot and ankle surgeries; postoperative pain management; procedure-specific ra; regional analgesia; regional anesthesia.

Figure 1. Probe position and relevant sonoanatomy of the high-volume proximal adductor canal (Hi-PAC) block

(A) Probe position of the Hi-PAC block. (B) Needle insertion during Hi-PAC block. (C) Sonoanatomy at the level of the apex of the femoral triangle appears as a “figure of 3” formed by the medial borders of the sartorius and the adductor longus muscles. (D) Sonoanatomy at the level of proximal adductor canal (target site). (E) Needle direction and drug deposition during Hi-PAC block. The green line below STM indicates the vasoadductor membrane. The white line indicates the needle. The blue area indicates the drug spread. Hi-PAC: high-volume proximal adductor canal; FA: femoral artery; STM: sartorius muscle; VMM: vastus medialis muscle; ALM: adductor longus muscle; AMM: adductor magnus muscle; SN: saphenous nerve; Ant.Lat.: anterolateral; Post.Med.: posteromedial

Figure 2. Bar diagram depicting the change in vital parameters before and after the high-volume proximal adductor canal (Hi-PAC) block

HR: heart rate; SBP: systolic blood pressure; DBP: diastolic blood pressure; MAP: mean arterial pressure

Figure 3. Line diagram depicting the change in postoperative pain scores (at rest and after squeezing) over time

Hi-PAC: high-volume proximal adductor canal; T0: pain scores before the Hi-PAC block; T6: pain scores six hours after the Hi-PAC block; T12: pain scores 12 hours after the Hi-PAC block; T24: pain scores 24 hours after the Hi-PAC block

Figure 4. Pie diagram representing the total analgesic duration of the high-volume proximal adductor canal (Hi-PAC) block

Figure 5. “To give or not to give” dilemma situation while considering regional analgesia for below-knee surgeries and available regional analgesia (RA) options

ACS: acute compartment syndrome; RA: regional analgesia; LA: local anesthetic; Hi-PAC: high-volume proximal adductor canal