Anesth Analg 2006;102:973-974
© 2006 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000199174.30944.B4
LETTER TO THE EDITOR
Blurred Vision as the only Symptom of a Positive Epidural Test Dose
Manuel C. Vallejo, MD,
Shawn T. Beaman, MD, and
Sivam Ramanathan, MD
Department of Anesthesiology, Magee-Womens Hospital, University of Pittsburgh, Pittsburgh, PA; vallejomc{at}anes.upmc.edu
To the Editor:
A 29-year-old prime at term patient requested labor epidural analgesia. Using the loss of resistance technique, a 17-gauge Tuohy needle was used to place a flexible tip single orifice Arrow® catheter 5 cm into the epidural space. After negative aspiration, a 3 mL test dose of 1.5% lidocaine with 1:200,000 epinephrine was given. Within 1 min, the patient reported bilateral blurred vision without any other symptoms. Her pulse remained stable between 75 and 85 bpm, and her blood pressure remained stable between 128–145 mm Hg systolic. Spo2 remained 100% on room air with a reassuring fetal heart tracing. She was positioned supine with left uterine displacement. The blurred vision resolved within 5 min. The catheter was retested with another 3-mL test dose. Again, she reported only bilateral blurred vision with no other symptoms or vital sign changes. The catheter was removed and replaced at another interspace. Test dose was negative. She was bolused with 10 mL of 0.125% bupivacaine and placed on continuous patient-controlled epidural analgesia. The rest of her labor and vaginal delivery proceeded uneventfully.
The blurred vision experienced by this patient on two successive test dose occasions utilizing the same epidural catheter most likely represented intravascular placement. Visually, this was supported by the 0.5 cm heme staining noticed at the catheter tip on removal. We believe her blurred vision was a result of direct test dose intracranial venous system dissemination via Batson's vertebral venous plexus (Fig. 1). Batson's vertebral venous plexus consists of four interconnected venous networks surrounding the vertebral column: 1) the anterior external vertebral venous plexus, 2) the posterior external vertebral venous plexus, 3) the anterior internal vertebral venous plexus, and 4) the posterior internal vertebral venous plexus. Both the anterior internal and posterior internal vertebral venous plexus constitute the epidural venous plexus. Batson's vertebral venous plexus is composed of valveless, thin-walled, low pressure vessels that have numerous communications with veins in the spinal canal, the veins around the spinal column, and the bones of the vertebral column. This system also communicates directly with intercostals veins, the azygous system, and the intracranial venous system. The vertebral venous plexus bypasses the caval, portal, and pulmonary vein systems and has been postulated by Batson as a way for aberrant spread of infection, air emboli, and tumor metastases to other parts of the body (Figure 1) (1). Walsh and Goldberg reported a case of blindness after pneumothorax explained by the introduction of air into the vertebral venous system (1,2).
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Figure 1. Schematic drawing of Batson's vertebral venous plexus. Arrows showing cranial and caudal spread. Schematic drawing recreated and modified from Batson (1).
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Positive intravascular test dose usually results in tachycardia secondary to epinephrine, with symptoms of mild local anesthesia toxicity including tinnitus, perioral paresthesias, and a metallic taste. In this patient, the only symptom of intravascular placement was bilateral blurred vision. This report emphasizes that atypical symptoms can occur, and the value of using a test dose to rule out intravascular or intrathecal placement cannot be underestimated.
References
- Batson OV. The function of the vertebral veins and their role in the spread of metastases. Ann Surg 1940;112:138–49.[Medline]
- Walsh FB, Goldberg HK. Blindness due to air embolism: a complication of extrapleural pneumolysis. JAMA 1940;114:654.
