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From the Departments of *Anesthesiology, Orthopedic Surgery, and Neurosurgery, Dartmouth Medical School, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire.
Address correspondence and reprint requests to Brian D. Sites, MD, Director of Regional Anesthesia, Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH, 03756. Address e-mail to brian.sites{at}hitchcock.org.
Abstract
BACKGROUND: Traditional uses of ultrasound by anesthesiologists include transesophageal echocardiography, facilitation of vascular access, and guidance of peripheral nerve blocks.
METHODS: In this case series, we report a novel application of ultrasound by anesthesiologists to facilitate the operative dissection of upper extremity peripheral nerve tumors.
RESULTS: In four cases, ultrasound was used to intraoperatively locate the tumor, plan the safest surgical approach, and exclude tumor vascularity.
CONCLUSIONS: Ultrasound can be used by anesthesiologists to facilitate the surgical management of peripheral nerve tumors.
Ultrasound technology is used by almost every medical specialty. Among anesthesiologists, it has been accepted for transesophageal echocardiography and for facilitating central venous access (1,2). In the past 5 yr, ultrasound has gained popularity for neural imaging by regional anesthesiologists (3–6). In this application, anesthesiologists can image, with great detail, the complex and varied peripheral nervous system. There have been no reports of the use of ultrasound by anesthesiologists to assist in the surgical management of peripheral nerve tumors. The purpose of this case series is to document an evolving practice at our institution in which ultrasound is used by anesthesiologists to facilitate the surgical dissection of peripheral nerve tumors.
CASE REPORTS
The Committee for the Protection of Human Subjects at Dartmouth Medical School does not require individual approval for case reports. All images and data respect privacy as mandated by the Health Insurance Portability and Accountability Act.
Case 1
A 41-yr-old man presented to the operating room for a resection of two peripheral nerve tumors associated with his right median nerve. The first lesion was a 3-cm mass immediately proximal to the wrist crease. The second lesion was a 2-cm mass located in the midforearm. After informed consent and the establishment of general endotracheal anesthesia with neuromonitoring, the surgical dissection began.
The distal tumor was easily palpable by the surgeons, whereas the more proximal lesion was not. At this point, an intraoperative consultation was obtained by the neurosurgeons from the regional anesthesia service. The specific request by the surgeons was to use ultrasound to localize the proximal nonpalpable tumor, plan the initial skin incision, assess for vascularity, and to define the proximal and distal margins of the tumor. To achieve this end, a high-frequency ultrasound system (Micromaxx, HS probe: scanning at 13 MHz, Sonosite, Bothell, WA) was used to examine the patient’s right forearm and median nerve. To maintain sterile conditions, the probe was inserted into a sterile probe cover (Ultrasound Probe Sheath, Bard Access Systems, Salt Lake City, UT). The heterogeneous hypoechoic mass was easily identified on long axis (Fig. 1). The normal median nerve was also defined both proximal and distal to the tumor. The tumor margins were traced on the skin using a marking pen. Using color Doppler, we identified no vascularity associated with the tumor, which could potentially complicate the surgical dissection. The surgeons, using the margins drawn on the skin, dissected out the tumor (Fig. 2). The lesion was successfully removed without anatomical disruption of the median nerve. A postresection ultrasound confirmed the normal appearance of the median nerve. The final pathological diagnosis was confirmed to be a schwannoma. In a 1-mo follow-up, the patient demonstrated no sensory or motor deficits in his hand or arm.
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Cases 2–4
Table 1 summarizes three additional cases in which the intraoperative use of ultrasound by anesthesiologists proved helpful in the resection of peripheral nerve tumors.
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DISCUSSION
These four cases illustrate a novel clinical use of ultrasound by anesthesiologists in the operating room.
Ultrasound is an accepted modality for assisting in the diagnosis of peripheral nerve tumors (7–9). The largest ultrasound case series of peripheral nerve tumors consisted of eight patients having a total of nine peripheral nerve tumors (9). The authors reported that all lesions appeared hypoechoic and homogenous. Three tumors had associated vascularity that was obliterated with light probe pressure. The final diagnoses included unspecified peripheral nerve tumor, neurofibroma, schwannoma, and spindle-cell tumor.
The potential benefits of an intraoperative evaluation of peripheral nerve tumors with ultrasound include faster surgical resection, as in our index case where the tumor was nonpalpable. In addition, benefits include reduction in collateral damage (such as vascular injury), avoidance of contiguous normal neural structures, and identification of tumor-associated vascularity.
Such a practice is not without controversy. Specifically, issues may arise regarding the appropriateness, training, and credentialing of anesthesiologists engaged in the intraoperative use of ultrasound to facilitate the surgical management of peripheral nerve tumors. This diagnostic use of ultrasound is philosophically and practically different from the use of ultrasound as a therapeutic intervention, as occurs during a peripheral nerve block. This controversy underscores the need for practice standards and core competencies of the various ultrasound applications (from nerve imaging to central line placement). In our case series, many of the competencies (e.g., image generation, color Doppler application, muscle-nerve distinction) involved in performing a (therapeutic) ultrasound-guided nerve block (10) overlap with those needed to conduct a diagnostic ultrasound examination of a peripheral nerve tumor. Thus, it is our opinion that experienced and trained regional anesthesiologists engaged in neural imaging for nerve blocks are well situated and "qualified" to facilitate the surgical dissection of peripheral nerve tumors.
In conclusion, this case series has described an evolving ultrasound practice at our institution.
Footnotes
Accepted for publication July 31, 2007.
REFERENCES
This article has been cited by other articles:
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  R. S. Adler The Use of Compact Ultrasound in Anesthesia: Friend or Foe Anesth. Analg., December 1, 2007; 105(6): 1530 - 1532. [Full Text] [PDF]
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