Abstract
The widespread use of anticoagulants for a variety of conditions is a concern for anesthesiologists who place peripheral and neuraxial blocks. Development of a central hematoma can have catastrophic complications for the patient. It can be difficult to generalize recommendations for neuraxial blocks and peripheral blocks, which generally have less risk. We present a typical case, review anticoagulation guidelines, and discuss considerations for care of these complicated patients.
Keywords
anticoagulation, antithrombotic, peripheral nerve block, regional anesthesia, thrombolytic
Case Synopsis
A 70-year-old man with a history of valvular heart disease, peripheral vascular disease, and diabetes mellitus is scheduled to undergo a below-the-knee amputation. The patient has been receiving daily anticoagulation with warfarin since his aortic valve replacement 5 years ago. Five days before surgery, the patient’s warfarin was discontinued by his primary care physician, at which time he began therapeutic anticoagulation bridging therapy with low-molecular-weight heparin (LMWH). The patient’s last injection of LMWH was 24 hours ago. The orthopedic surgeon intends to reinitiate anticoagulation with LMWH 12 hours after surgery. During the preanesthetic interview, the patient requests peripheral nerve catheters for extended postoperative analgesia.
Acknowledgment
The author wishes to thank Dr. James R. Hebl for his contribution to the previous edition of this chapter.
Problem Analysis
Definition
The use of peripheral nerve blocks (PNBs) for perioperative anesthesia and analgesia has increased dramatically. Reasons for the increased use of PNBs include not only the potential benefits ( Box 35.1 ) but also the avoidance of complications that may accompany general anesthesia and/or central neuraxial techniques. These include concerns about postoperative nausea and vomiting, respiratory depression from parenteral opioids, hemodynamic instability resulting from sympathetic block, and delayed discharge after outpatient surgery.
Superior postoperative analgesia
Improved rehabilitative efforts (owing to analgesia)
Decreased perioperative nausea and vomiting
Faster emergence and recovery
Earlier mobilization (unilateral blockade)
Faster outpatient discharge
Improved blood flow to affected extremity
Benefits extended with continuous catheter techniques
However, the use of PNBs is associated with its own unique set of concerns and complications. In particular, hemorrhagic complications have been reported with greater frequency as changes in clinical practice occur (e.g., more aggressive perioperative anticoagulation, new regional techniques, and new anticoagulants). Although hemorrhagic complications are quite rare, they can be among the most devastating complications of PNB and have been reported with a variety of PNBs.
Recognition
In general, localized bruising and tenderness are common following PNB, with reported frequencies ranging from 8% to 23%. True hemorrhagic complications appear to be much less common. For example, the reported frequency of hematoma formation after brachial plexus block ranges from 0.2% to 3%. Most hematomas are small, unrecognized, and clinically inconsequential. However, there have been reports of more severe hemorrhagic complications, as well as significant neurologic impairment after hematoma formation. Recognition of bleeding complications relies on astute clinical vigilance throughout the perioperative period; this is especially important in patients receiving perioperative anticoagulation. Significant hypotension, localized pain or tenderness, severe ecchymosis, unexplained anemia, or the development of neurologic deficits may signal underlying hemorrhage or a compressive hematoma. Imaging may be required for confirmation and to determine the location and extent of injury.
Risk Assessment
There are no reports on the frequency or severity of hemorrhagic complications with PNB in patients receiving anticoagulants. Reports of direct vascular injury after PNB are limited to case reports. Such complications have occurred in patients with normal hemostasis and in those receiving anticoagulation therapy. Neurologic compromise from bleeding is usually transient and self-limited. Thus in contrast to central neuraxial bleeding, bleeding into a more compliant peripheral nerve site seems unlikely to be associated with irreversible, permanent nerve injury.
The majority of severe hemorrhagic complications after PNB have been associated with either posterior lumbar plexus (i.e., psoas compartment; see Chapter 175 ) or lumbar sympathetic blocks. In all instances, patients received anticoagulants before, during, or after PNB. Irreversible platelet aggregation inhibitors (e.g., ticlopidine, clopidogrel) are also implicated as contributing to hemorrhagic complications in patients with PNB. Severe hemorrhage requiring transfusion, but not permanent neurologic injury, may be the most serious complication of PNB in anticoagulated patients. Severe hemorrhage and subsequent injury is most likely if the PNB is performed at concealed, noncompliant sites (e.g., psoas compartment). Further, such occult bleeding may go unrecognized for several hours to days.
Implications
Perioperative anticoagulation for the prevention of venous thromboembolism can result in significant morbidity, mortality, and resource allocation. Knowledge of specific clinical risk factors for thromboembolism ( Box 35.2 ) is the basis for the proper use of perioperative anticoagulation treatment or prophylaxis. These risk factors are present alone or in combination in a high proportion of hospitalized patients. Consequently, many patients who present for elective or emergency surgery are, or will be, receiving medications that alter normal hemostasis. All clinicians should be aware of this, especially when performing regional anesthesia.
Increased age
Prolonged immobility (paresis)
Prior stroke or paralysis
Previous venous thromboembolism
Cancer (active or occult) and cancer therapies
Major surgery
Abdominal surgery
Pelvic surgery
Lower extremity surgery
Trauma, especially lower extremity injury
Obesity
Varicose veins and other flow obstructions (tumor, arterial abnormality)
Cardiac dysfunction
Indwelling central venous catheter
Inflammatory bowel disease
Nephrotic syndrome
Pregnancy, postpartum period, estrogen use, and estrogen receptor modulators
Erythropoiesis-stimulating agents
Paroxysmal nocturnal hemoglobinuria
Thrombophilia (acquired or inherited)
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