Definition

The case synopsis raises a discussion about side effects of local anesthetic versus potentially more serious complications of regional anesthesia for surgery. Regional anesthesia provides high-quality analgesia and minimizes opioid-related side effects. Although both opioid and surgical complications are much more prevalent than regional anesthetic complications, some do occur.

Numerous studies have shown that perineural local anesthetic infusions provide profound analgesia. Continuous techniques such as these have been used to provide both intraoperative anesthesia and postoperative analgesia. Certain complications are block specific, such as a pneumothorax with supraclavicular or infraclavicular blocks or epidural spread with a lumbar plexus block. This chapter does not discuss block-specific complications, but rather perioperative complications regarding continuous peripheral nerve blockade.

A variety of complications associated with peripheral nerve block, perineural catheter insertion, and surgery have been reported ( Table 54.1 ). Early recognition of complications is essential in subsequent treatment. Recognition of problems potentially related to a nerve block begins with a focused history and physical examination. Review of the medical record for medications administered systemically or through peripheral nerve catheters can aid in narrowing the differential. Furthermore, surgical factors, including but not limited to patient positioning intraoperatively, surgical approach, and postoperative surgical dressings, may be causal factors.

Recognition

Problems with peripheral nerve catheters may present in a variety of ways based on the primary pathology. The clinical features of neurologic complications, including nerve injury, include the following:

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  Prolonged motor block long after cessation of local anesthetic infusion

  
  
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  Reduced touch or paresthesias that persist or worsen after cessation of infusion

  
  
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  Pain that is neuropathic in nature

  
  
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  Numbness and perception of a heavy or weak extremity

  
  
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  Loss of proprioception

The clinical features of inadequate analgesia or ischemia include the following:

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  Increasing or high patient-reported pain score without numbness

  
  
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  Increasing or high patient-reported pain score with numbness

  
  
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  Increased opioid requirements and opioid-related side effects

The clinical features of infectious complications include the following:

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  Late onset of symptoms, 2 to 3 days after peripheral nerve catheter placement

  
  
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  Tissue erythema and swelling at catheter insertion site

  
  
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  Pain and tenderness at catheter insertion site

  
  
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  Leukocytosis and fever

The clinical features of local anesthetic toxicity will not be discussed here as they are the focus of Chapter 103 .

Risk Assessment

The incidence of complications following peripheral nerve block is low; benefit must be assessed against the risks of general anesthesia and central neuraxial techniques. Auroy and coworkers reported the incidence of serious complications related to regional anesthesia in a prospective study using data from 103,730 cases. They found that the incidence of cardiac arrest and neurologic injury related to regional anesthesia was low, more than 3 standard deviations less after regional procedures compared with spinal anesthesia. Although these data did not discriminate between single-injection and continuous peripheral nerve block, in general, peripheral nerve blocks were associated with fewer neurologic injuries and cardiac arrests when compared against central neuraxial techniques.

Brull and colleagues in a publication reviewed 32 studies and estimated the rate of nerve complications at approximately 0.4% for neuraxial block and 0.3% for peripheral nerve blocks. However, they also noted that permanent neurologic injury was uncommon with regional anesthesia. Bergman and coworkers retrospectively examined the neurologic complications after 405 consecutive continuous axillary nerve block catheter procedures where they found no greater incidence of neurologic complications using continuous catheter techniques than using single injections. Borgeat and colleagues prospectively examined complications associated with interscalene block for shoulder surgery and found no differences between catheter techniques and single-injection blocks.

Leaving a catheter in situ entails the potential risk of infection and catheter migration into a vessel. This risk must be balanced against the benefit of superior analgesia compared with oral medications alone. In addition, although Cuvillon and coworkers were able to isolate bacterial colonization in 57% of 208 femoral nerve catheters, no clinically relevant infectious complications occurred. There was one case (0.1% incidence) of a serious infection (abscess), and superficial erythema was observed in 0.7% of the patients in Borgeat’s series (cited earlier). Only superficial skin infections (5% incidence) were reported in the recent series by Boezaart and associates. Only one case report of migration into a vessel has been reported in the literature, so the incidence of that complication is unknown.

Following resolution of the primary block with long-acting amide local anesthetics, inadvertent catheter dislodgment or incorrect initial catheter positioning is the most common cause of pain. This can occur in up to 10% to 20% of patients and is by far the most common complication of continuous perineural nerve block. Additionally, patients with infusions of low concentrations of local anesthetics in a functional perineural catheter may suffer breakthrough pain. Use of patient-controlled bolus, in addition to the background basal infusion, can reduce the severity of breakthrough pain. As the case synopsis illustrates, the challenge for the clinician is to balance the risk of motor block or even local anesthetic toxicity against the patient’s discomfort from inadequately controlled pain.

The cause of postoperative falls is multifactorial, encompassing lower extremity surgery, age, and obesity. Some controversy exists regarding the incidence of postoperative falls with patients receiving regional anesthesia. Wasserstein and colleagues and Ilfeld and colleagues identified continuous femoral nerve block as an independent risk factor for falls following total knee arthroplasty. Conversely, Memtsoudis and colleagues reviewed a national database of over 191,000 patients in more than 400 hospitals that did not show an association between regional anesthesia and inpatient falls. However, they were not able to discriminate between single-shot blocks and catheters. Care must be taken in patients with peripheral nerve catheters, and involvement of anesthesiologists in development of a hospital falls prevention program can help minimize risks.

Implications

Neurologic complications can result in weakness and chronic pain, with reduced functional capacity after surgery. Careful technique and patient selection are important factors in reducing these complications. Prolonged motor block produced by high local anesthetic concentrations may delay early ambulation, but has not been shown to affect long-term functional outcomes following arthroplasty. In fact, patients given either epidural or peripheral nerve catheters after knee arthroplasty have increased rates of recovery for the first 6 weeks after surgery compared with those on opioid analgesia regimens. Failed blocks result in pain and reduced patient satisfaction, many times leading to increased use of opioids and opioid-related side effects such as respiratory depression, pruritus, nausea, vomiting, and constipation. Infection can result in discomfort, limitation of activity, potential for infected hardware, and reoperation. Falls can increase morbidity, cause prolonged hospital length of stay, and may lead to reoperation.