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Iatrogenic Arteriovenous Fistula During Lumbar Microdiscectomy

Sadhasivam, Senthilkumar MD*; Kaynar, A Murat MD

doi: 10.1213/01.ANE.0000137391.55836.56
Technology, Computing, and Simulation: Neurosurgical Anesthesia: Case Report
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Vascular lacerations, arteriovenous fistulae, and pseudoaneurysms are rare, but potentially life threatening, complications of lumbar disk surgery. These iatrogenic vascular injuries may present with significant hypotension during the perioperative period. Early diagnosis and surgical repair may decrease morbidity and mortality. We discuss perioperative implications of postdiscectomy vascular injuries in this report.

IMPLICATIONS: Iatrogenic vascular injuries after lumbar disk surgery are rare but potentially life threatening. Such injuries may perioperatively present in a diverse array of manifestations, and often the diagnosis is delayed or overlooked, which may increase morbidity and mortality. Early diagnosis and surgical repair of these vascular injuries can be life saving.

*Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, University of Pennsylvania; and †Department of Anesthesiology and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston

Accepted for publication June 15, 2004.

Address correspondence and reprint request A. Murat Kaynar, MD, Department of Anesthesiology and Critical Care, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215. Address e-mail to mkaynar@bidmc.harvard.edu.

Vascular structures close to the lumbar spine can be injured during the surgical removal of herniated intervertebral discs. Depending on the extent and location of the trauma, the lacerations of the vessels may result in hemorrhage, formation of false aneurysm, or hemodynamically significant arteriovenous fistula (AVF). The frequent mortality of 40%–50% after these vascular injuries is often related to acute blood loss into the retroperitoneal or intraperitoneal space. We describe an iatrogenic AVF with early diagnosis and management resulting in a successful outcome.

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Case Report

A 28-yr-old healthy woman, with symptoms of low back pain and urinary retention, was scheduled for left-sided microdiscectomy of a herniated L4-5 intervertebral disk. Anesthesia was induced with thiopental and tracheal intubation facilitated with succinylcholine. Anesthesia was maintained with isoflurane, nitrous oxide in oxygen, and vecuronium. The patient was positioned prone, and the procedure was uneventful until removal of the disk, which coincided with a sudden decrease in arterial blood pressure from 110/70 to 70/40 mm Hg. There was no significant bleeding in the operative field and no significant decrease in end-tidal CO2. The surgical field was flooded with normal saline to prevent possible air embolism caused by air entrainment into exposed lumbar veins.

The lungs were ventilated with 100% oxygen, the endotracheal tube was position confirmed, and 3 L of lactated Ringer's solution and 1 mg of phenylephrine (100-μg boluses) were administrated. Her arterial blood pressure stabilized at 120/60 mm Hg. A bleeding lumbar vein was ligated, and the rest of the procedure was uneventful. The trachea was extubated in the operating room, and the patient was transferred to the recovery room. On physical examination, the abdomen was soft and nontender, and the lower extremities were nonedematous, with pulses equally palpable. Because of continuing requirements for volume resuscitation and vasopressor medications, the patient was transferred to the intensive care unit where she received 6 U of packed red blood cells. A right-sided abdominal bruit suggested the possibility of an AVF. Angiography was performed, which revealed a fistula between the right common iliac artery and the inferior vena cava (Fig. 1). An emergency exploratory laparotomy was performed for persistent hemodynamic instability. There was no free blood in the peritoneal cavity. However, a large retroperitoneal hematoma extending from the ligament of Treitz to the pelvis was found. The right common iliac artery had a 50% circumferential tear, and the inferior vena cava had a 2.5-cm defect extending into the proximal left common iliac vein. The injuries were repaired, and the patient had an uneventful postoperative course.

Figure 1

Figure 1

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Discussion

The causes of potentially lethal intraoperative hypotension during lumbar disk surgery include hemorrhagic shock caused by iatrogenic vascular injuries (1–10), venous air embolism (11), and anaphylactic drug reactions. We report a case of iatrogenic AVF presenting with unexplained sudden hypotension.

The incidence of vascular injuries, including AVF, lacerations, and pseudoaneurysms during disk operations, is one to five per 10,000 (4). Risk factors include anterior annulus and longitudinal ligament degeneration, improper positioning of the patient, and repeated operations (4,6,11). The interspace most frequently associated with vascular injury is L4-5, corresponding to the common iliac vessels and the vena cava (2,5,6,11). This was the case in our patient.

Angiography is the “gold standard” for diagnosing iatrogenic vascular injury (3). Clinical features and use of angiography, ultrasonography with color-flow Doppler mapping, or computerized tomography are important for early diagnosis (3,12). Because vascular injuries are associated with frequent mortality (40%–50%), diagnostic tests should not delay surgical treatment in hemodynamically unstable patients (3,8,9,13,14).

In young and healthy patients, hypotension from blood loss may be delayed, and retroperitoneal or intraperitoneal bleeding may not be obvious with the patient in the prone position. Therefore, when there is unexplained intraoperative hypotension and anemia during spinal surgery, iatrogenic vascular injury should be considered. Intraoperative death of a young patient caused by aortic injury during discectomy has been reported; electromechanical dissociation from severe hypovolemia was diagnosed as pulmonary embolism because there was no obvious surgical bleeding (15). Early diagnosis and aggressive management are important. If major vascular injury is suspected, discectomy should be interrupted and emergency laparotomy performed, even in the presence of hemodynamic instability (16). Medical antishock trousers had been successfully applied to stabilize hemodynamics until an emergency laparotomy was performed in a patient with life threatening injury to iliac vessels during lumbar discectomy (17).

In contrast to vascular lacerations, AVF may not present with severe symptoms in the first 24 hours. In a case series, the diagnosis was established after 24 hours in 56 of 66 patients with AVF (4). Hemodynamically significant AVF may be associated with anemia, hypovolemia, lower limb edema, abdominal thrill, back and abdominal pain, high output cardiac failure, rectal bleeding, hematuria, and renal failure caused by increased venous pressures (1–4,6–9). These symptoms usually resolve after surgical correction. Percutaneous endovascular repair is less invasive, involves less blood loss, and may be equally successful (18,19). In repairing complicated AVF, cardiopulmonary bypass may be required to enable control and safety (20).

In conclusion, we describe a case of traumatic AVF in a young healthy patient undergoing lumbar disk surgery. Anesthesiologists should be aware of the potential for vascular injuries during lumbar discectomy and be prepared to intervene.

We sincerely thank Mehernoor Watcha, MD, Associate Professor in Anesthesia and Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, for his critical review and suggestions.

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References

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