Introduction:
Continuous peripheral nerve blocks (CPNBs) are conceptually simple: a catheter is percutaneously installed adjacent to a peripheral nerve or plexus, and local anesthetics are administered through the catheter, providing a prolonged block that may adjust to the desired effect. The maximum duration of a single-injection peripheral nerve block is 8 to 24 hours. Whenever an extended neural blockade is preferred, CPNB provides an alternative option.
What Are the Indications of the CPNB?
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CPNBs are for extending the duration of intraoperative surgical anesthesia and treating intractable hiccups.
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CPNB-induced sympathectomy and vasodilation to enhance blood flow following a vascular accident, digit transfer or replantation, or limb salvage.
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To relieve Raynaud's disease vasospasm and treat peripheral embolism.
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CPNB is used to treat chronic pain conditions like pain due to cancer, complex regional pain syndrome, ischemia-induced pain, pain due to ulcers, phantom limb pain, and trigeminal neuralgia.
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Following any trauma, CPNB offers analgesia while transported to a distant treatment center or simply waiting for surgical repair.
How Is Catheter Insertion Done in CPNB?
1. Skin Preparation and Patient Draping:
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Independent of the technique used, sterility is critical for the effectiveness of CPNB (neurostimulation or ultrasound). Therefore, hand washing with an antiseptic solution, sterile gloves, surgical masks, and head caps, and alcohol-based chlorhexidine antiseptic solutions are all recommended by the American Society of Regional Anesthesia and Pain Medicine (ASRA).
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The ultrasound probe must be further sterile protected. In addition, to avoid and recognize catheter infection, the catheter dressing after insertion must be clean and transparent.
2. Needle Choice:
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In regional anesthesia, short bevel needles are generally accepted as standard practice. However, the literature does not support the idea that using short bevel needles reduces nerve injury.
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The application of ultrasound for catheter insertion is growing, and Tuohy needles and thin-walled needles are prevalent with this method. But besides the use of ultrasound, the risk of intrapreneurial local anesthetic injections is quite prevalent. Moreover, according to Liu et al., a blunt needle (pencil point or Tuohy) provides a better appreciation of a ‘pop’ as tactile feedback when the various fascias are perforated for fascia iliaca blocks.
3. Nerve Stimulation:
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Peripheral nerve blocks were performed utilizing induced paresthesia (no paresthesia and no analgesia), fascial ‘pop,’ or even fluoroscopic guidance before the advent of portable nerve stimulators in 1962.
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Even though there has never been a repeated comparison of nerve stimulation and paresthesia, which was and remained the most frequently used approach, nerve stimulation was regarded as the gold standard till the emergence of ultrasound in 1989.
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The basic principle of nerve stimulation is to use an electrical current to position an insulated needle adjacent to a peripheral nerve to administer local anesthetic or to place a perineural catheter. Without a doubt, nerve stimulation has a significant success rate for both single-shot perineural blocks (SPNB) and CPNB when appropriately used.
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To prevent nerve injury and ensure catheter placement parallel to the nerve, the needle must be directed tangentially to the nerve during catheter placement. In this situation, a three-orifice catheter will spread the local anesthetic more easily along the nerve than an end-orifice catheter.
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To avoid premature catheter dislocation, the placement should occur before administering the local anesthetic. To prevent displacement after insertion, the cannula over the needle technique of threading the perineural catheter three to four centimeters past the tip of the cannula with successive subcutaneous tunneling for four to five centimeters is the method of choice for catheter placement.
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According to the research, the ideal distance to advance a perineural catheter far beyond the tip of the needle is uncertain. Still, evidence suggests that increasing the insertion distance greater than five centimeters is associated with an increased risk of catheter coiling because there is no evidence of insertion lengths greater than five centimeters. The maximum penetration depth should be regarded as five centimeters.
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A stimulating catheter is another option: an insulated needle is employed to identify the target nerve, accompanied by the insertion of a perineural catheter that carries current to its tip. Despite evidence supporting some benefits in specific anatomic locations (popliteal fossa, femoral, and interscalene region), the clinical relevance in light of the significantly increased material costs remains unknown.
What Are the Benefits of CPNB?
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Benefits include a dramatic reduction in the need for additional opioids, opioid-related adverse effects, sleep disturbances, and increased patient satisfaction.
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Furthermore, ambulatory CPNB has been shown to reduce the time to adequate ambulation while optimizing daily activities, particularly in comparison to intravenous opioids.
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Accelerated progress in passive joint range of motion just after shoulder and knee arthroplasty has been described for continuous regional anesthesia, possibly resulting in shorter hospitalization.
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There have been reports of ambulatory shoulder arthroplasty and 23-hour stay knee and hip arthroplasty utilizing ambulatory continuous interscalene, femoral, and psoas compartment nerve blocks, respectively.
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Moreover, a continuous femoral nerve block reduces post-knee arthroplasty inflammation.
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The CPNB could not produce significant long-term advancements in outcomes such as decreased chronic pain and improved health-related quality of life.
What Are the Complications of CPNB?
- Absolute and Relative Contraindications: Skin infection at or adjacent to the puncture site, systemic disease, raised body temperature, increased susceptibility to bleeding or bruising, patients on systemic anticoagulation therapy, changing neurology, peripheral neuropathy, and risk of compartment syndrome.
- Minor Complications: Dislodgement of the catheter, leakage of the fluid, detachment from the pump system, malfunction of the infusion pump system, and irritation in the skin or hypersensitivity to the sterile catheter dressing are all possibilities.
- CPNB -Specific Complications: Incorrect placement of the catheter results in too much distance from the target nerve and thus provides insufficient analgesia or is in an undesirable position such as intravascular, intrapleural, intraneural, epidural, or even intrathecal. However, it is uncertain whether the migration of the catheter is possible after proper placement.
- Infections: Lack of or ineffective antibiotic prophylaxis and axillary or femoral catheter placement are risk factors for disease in CPNB. Other studies, however, have identified inter-scalene placement as the most problematic for infection. Additional risk factors include intensive care unit, male sex, and enhanced infusion time. Insufficient evidence suggests that subcutaneous catheter tunneling reduces the risk of bacterial colonization and infection. To avoid such complications, use sterile preventive measures such as antiseptic hand washing, sterile gloves, surgical masks and hats, and alcohol-based chlorhexidine antiseptic solutions.
- Neurologic Complications: Even though neurologic injury caused by CPNB is usually temporarily ranging from 0.3 percent to 2.0 percent, it is still the most feared concern when performing regional anesthesia. Damage can occur during catheter placement or even after surgery.
- Local Anesthetic Toxicity: Despite these low infusion rates, local anesthetic toxicity has been noted as a possible side effect of CPNB. Local anesthetic systemic toxicity is a profound and uncommon side effect of CPNB. Although continuous infusion is unlikely to cause an abrupt onset of toxicity, patients using a pump with bolus capability are in danger if migration occurs intravascularly. In addition, Myonecrosis is a rare complication caused by repeated boluses of Bupivacaine.
Conclusion:
A few aspects of perineural infusion remain uncertain, including the optimal catheter insertion treatment method, the perfect method for each indication, the infusates with the highest safety, standardized local anesthetic delivery modalities, and enhancement of continuous ambulatory infusion to decrease potential risks (as falling). The ideal analgesic technique for many surgical procedures needs to be determined further, and CPNB should be compared to possible new analgesic techniques or regimens to improve the outcome of the method.
