Updated feasibility trial experience with the Viaderm percutaneous access device.

The percutaneous access device (PAD) is used to connect an external drive unit to the Kantrowitz CardioVad (KCV), a cardiac assist device for the treatment of chronic heart failure. The PAD conveys pneumatic power from a drive unit to the implanted blood pump and an electrocardiogram signal from the myocardium to the drive unit. The device-tissue interface of the PAD is precoated with autologous fibroblasts cultured from a skin sample of the intended recipient. This preparation demonstrated long-term stability in animals and was adopted for use in patients receiving the KCV. The KCV is activated intermittently, and the drive unit may be connected and disconnected by the patient, which subjects the PAD to frequent manipulation. To date, the PAD has been implanted in nine patients ranging in age from 41 to 74 years. Implant times ranged from 2 to 458 days, for a total of 1082 days, of which 557 days were in an outpatient setting. Two patients experienced episodes of infection that did not originate from the PAD-tissue interface. This feasibility study demonstrated that (1) the PAD is stable and infection resistant in long-term ambulatory patients, (2) the PAD withstood the challenge of daily manipulation (the KCV is turned on and off electively), and (3) PADs can be replaced, if necessary.

Perioperative management of calves undergoing implantation of a left ventricular assist device.

OBJECTIVE: To describe perioperative management of calves that underwent left lateral thoracotomy, aortic cross-clamping, partial left heart bypass and implantation of a left ventricular assist device. SAMPLE POPULATION: A total of 43 healthy castrated male calves, weighing 121 +/- 24 kg. RESULTS: Diazepam (mean +/- SD, 0.26 +/- 0.07 mg/kg), ketamine (5.9 +/- 2.17 mg/kg) and isoflurane were used in the anesthetic management of calves undergoing implantation of a left ventricular assist device in the descending thoracic aorta. Other adjunctive agents administered were fentanyl (11 +/- 5.4 microg/kg), lidocaine (4.9 +/- 3.19 mg/kg), bupivacaine (0.75%) and butorphanol (0.49 +/- 0.13 mg/kg). None of the calves regurgitated at induction or during intubation. A tube was used to drain the rumen and prevent bloat during the procedure. Partial left heart bypass was used to perfuse the caudal half of the body during the period of aortic cross clamp and device implantation. Initial mean systemic blood pressure was 96 +/- 25 mm Hg, and pressures measured in the auricular artery increased during aortic cross-clamping and bypass. Vasoconstrictor therapy was required to treat caudal arterial hypotension during the procedure in 9 calves. Mean systemic arterial pressures returned to baseline values by the end of the anesthetic period. Initial mean pulmonary arterial pressures (PAP) were 22 +/- 3 mm Hg. A significant but transient increase in pulmonary arterial pressure occurred after both heparin and protamine administration. CONCLUSIONS: The described anesthetic protocol was effective for thoracotomy and implantation of an intra-aortic left ventricular assist device in normal calves. Partial left ventricular bypass was a useful adjunct during the period of aortic cross clamp. The doses of heparin and protamine administered were effective. Responsibility to monitor oxygenation of the cranial half of the animal continues during the bypass period as hypoxemia due to pulmonary dysfunction will not be detected by the perfusionist.

Aggressive papillary tumors of the endolymphatic sac: clinical and tissue culture characteristics.

Aggressive papillary tumors of the temporal bone are neoplasms that were recently re-classified as tumors of the endolymphatic sac. They typically invade the mastoid bone and otic capsule and can grow into the petrous apex. The authors have treated three patients with this rare neoplasm and grown one of the tumors in tissue culture. This report reviews the clinical presentation in the three patients and the immunohistochemical staining characteristics of the tumor and tumor culture as compared to those of the endolymphatic sac. Findings support the hypothesis that aggressive papillary lesions of the temporal bone arise from the endolymphatic sac. Additionally, it is noted that the tumor culture maintains the characteristics of the original tumor and thus provides an exciting laboratory model for further study of this rare neoplasm.

A mechanical auxiliary ventricle. Histologic responses to long-term, intermittent pumping in calves.

The mechanical auxiliary ventricle (MAV) is an avalvular, inseries left ventricular assist device (LVAD) comprised of a 60 cc Biomer blood pump implanted in the descending thoracic aorta, a percutaneous access device (PAD), and an external pneumatic drive. In four calves the MAV was implanted and activated intermittently for 192, 249, 423, and 785 days, respectively; no anticoagulants were administered. When the animals were killed, the implants were retrieved, and autopsies, including gross, light microscopic, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) examinations, were performed. The MAV was securely attached to the aorta in every animal. A thin, even smooth, pseudoneointimal layer (PNI) contiguous with the aorta at the level of the suture line covered the MAV's blood-contacting surface. Areas of calcification beneath the PNI, expected in growing animals with implanted pumping devices, were noted. At autopsy there was no evidence of thrombosis or infection in the regions of the blood pump or the PAD. These findings confirm the calves' benign histologic response to the MAV, and together with the results of hematologic and biochemiccal studies, and bench tests of system components being reported elsewhere, indicate the system's readiness for limited clinical investigation in selected patients with chronic congestive failure.

Atypical invasion of the temporal bone in vestibular schwannoma.

Vestibular schwannomas typically present with erosion of the temporal bone that is limited to the boundaries of the internal auditory canal. Four patients with extensive erosion, excavations, and pseudosatellite defects in the petrous apex are presented. These bony changes extended anteriorly up to the level of the carotid canal. The patients did not have stigmata of neurofibromatosis type 2 and they did not have systemic bony disorders. The tumors did not show any unusual histopathologic changes. Such invasive tumors present an unusual surgical challenge compared to vestibular schwannomas with a more typical pattern of bony erosion. Radiological features and surgical considerations relevant to vestibular schwannomas with this rare presentation are discussed.

Erythropoietin-augmented isovolemic hemodilution in skull-base surgery. Case report.

Human erythropoietin in concert with intraoperative hemodilution, tumor embolization, and surgical staging was used to manage a red blood cell mass in an anemic Jehovah's Witness patient with a hypervascular meningioma. Erythropoietin (3000 U thrice weekly) and oral iron (1300 mg daily) were given for 1 month prior to surgery, raising the hemoglobin level from 11.8 to 14.1 gm/100 ml. A posterior fossa craniectomy combined with a temporal craniectomy was then performed so that partial petrosectomy, section of the transverse sinus, incision of the tentorium, and exposure of the lesion could be carried out. The first stage of the surgery was terminated immediately prior to tumor mobilization. Isovolemic hemodilution was initiated just before the skin incision. Postoperatively, the hemoglobin concentration dropped to 11.5 gm/100 ml. The erythropoietin dose was doubled and administration of oral iron continued, leading to a hemoglobin level of 14.0 gm/100 ml at 1 month after the first operation. The tumor was embolized using superselective catheterization. The next day, at the second stage of the surgery, the tumor was extirpated, again employing isovolemic hemodilution. By the 4th postoperative day, the hemoglobin level had dropped to 9.4 gm/100 ml. The patient made an uncomplicated recovery. Erythropoietin therapy contributed substantially to the successful outcome of this case. Since erythropoietin has the potential to augment all other forms of autologous banking, its role in elective neurosurgery may become increasingly important in an era of heightened concern about heterologous transfusion.

Use of neurosurgical techniques for removal of a cardiac tumor.

A 6-week-old male infant with a capillary hemangioma of the right atrioventricular groove adjacent to the right coronary artery and conduction system underwent successful resection with the aid of microneurosurgical instrumentation. The technical challenge was thought to be analogous to that encountered by microneurosurgeons in their dissection of brain tumors.

The transcranial translabyrinthine approach to acoustic neuromas.

We originally described the transcranial translabyrinthine approach (TCTL) to acoustic neuroma. The approach is a labyrinthine dissection that is performed via the suboccipital exposure. It allows a complete and direct visualization of the internal auditory canal and the identification of the facial nerve at "Bill's bar." The TCTL enhances the suboccipital approach and adapts to its concepts of the classical transmastoid translabyrinthine approach. We hereby report our initial experience with the TCTL and present the surgical results in six additional cases. We also discuss the indications of this approach and compare it to alternative approaches that are used for the removal of large acoustic neuromas that extend laterally in the internal auditory canal.

Split-calvaria osteoplastic rotational flap for anterior fossa floor repair after tumor excision. Technical note.

A split-calvaria osteoplastic rotational flap to repair the anterior fossa floor after tumor excision was devised and tested clinically. At surgery, the flap is outlined between the glabella and the vertex. After the pericranium between the glabella and the flap's anterior pole is elevated to form its pedicle, a full-thickness craniotomy is performed to expose the diploic aspect of the bone graft donor site (when the graft is relatively wide, bifrontal craniotomies may be advantageous). The diploic space is split in situ, taking care to protect the pedicle and its attachments to the osseous segment. Linear osteotomies in the outer table are created to mobilize the flap. With the flap rotated frontally, the craniotomy is completed. After tumor extirpation, the margins of the osseous segment of the flap are shaped to conform to the defect of the anterior fossa floor. Transverse osteotomies are performed so that the graft's convex curve conforms to that of the anterior fossa floor. The flap is then rotated into position. Follow-up evaluation in two patients at 22 and 30 months demonstrated bone integrity of the anterior fossa floor with graft preservation. Transient postoperative cerebrospinal fluid (CSF) rhinorrhea, which occurred in Case 1, was avoided in Case 2 by placing the osseous segment of the graft coplanar with the bone floor of the fossa. Neither patient had late meningitis or CSF rhinorrhea. The split-calvaria osteoplastic rotational flap may represent an advance toward the ideal reconstruction of the anterior cranial fossa floor.

Sacral root stimulation for controlled micturition: prevention of detrusor-external sphincter dyssynergia by intraoperative identification and selective section of sacral nerve branches.

Electrical stimulation of the S2 nerve root can be used to produce detrusor contraction and voiding in patients with spinal cord injury, but concurrent stimulation of the external urethral sphincter causes detrusor-sphincter dyssynergia. This has been managed with a second surgical procedure, peripheral transection of the pudendal nerve. In this study, performed in dogs after spinal cord transection, laminectomy and ventral foraminotomy permitted tracing of the S2 root into the pelvis, where its branches were identified by electrical stimulation and urodynamic recording. The pudendal (somatic) branch was sectioned; the autonomic branch innervating the detrusor was preserved. Electrical stimulation of the proximal S2 root then produced detrusor contraction without contraction of the external urethral sphincter. This approach, which requires a single operation and spares pudendal nerve functions mediated by nerve roots other than S2, may enable a neurostimulator to provide effective voiding, without detrusor-external sphincter dyssynergia, in man.

Transcranial translabyrinthine approach to vestibular schwannomas.

Surgeons who utilize the suboccipital approach for the removal of large vestibular schwannomas, can perform a planned labyrinthectomy from within the intracranial cavity via the suboccipital exposure. This transcranial translabyrinthine approach provides one of the major advantages of the conventional transmastoid translabyrinthine approach, namely, unambiguous identification of the facial nerve as it exits the internal auditory canal, without the need for complete mastoidectomy and labyrinthectomy. The labyrinthectomy is best performed prior to the complete exposure of the internal auditory canal. The approach requires the surgeon to identify the endolymphatic sac intracranially, then drill the temporal bone and follow the vestibular aqueduct to the utricle. The lateral and superior semicircular canal ampullae, the superior vestibular nerve, Bill's bar, and the facial nerve at the lateral end of the internal auditory canal can then be identified. After testing on multiple cadaver temporal bones, this approach was used in patients with large tumours that extended far laterally in the internal auditory canal. The steps in the technique are described in detail.

Transoral-transclival clipping of a giant lower basilar artery aneurysm.

The authors discuss the choice of the transoral-transclival approach for the repair of a lower basilar artery aneurysm in a 32-year-old sickle-cell patient. Efficiency of approach and minimization of damage to vital structures support the use of this technique. The risks of cerebrospinal fluid fistula and meningitis are considered. One year after operation, the patient is neurologically intact.

Percutaneous intra-aortic balloon counterpulsation.

Intra-aortic balloon pumping is the mainstay in the management of acute left ventricular dysfunction in the critical care setting. Percutaneous insertion affords rapid initiation of the procedure. Complications are in greatest part vascular and infectious. The advent of new-generation, totally automatic, closed-loop IABP systems offers the prospect of increasing the effectiveness of IABP support under most conditions, and especially during arrhythmias. This and other developments suggest that despite its standing as the most widely used temporary cardiac assist device, IABP has still to realize its full therapeutic potential.

Transcallosal, transventricular approach to a basilar apex aneurysm.

A new approach to the basilar apex in a patient with a megadolichobasilar anomaly and an abnormally rostral basilar apex aneurysm is described. The details of the surgical approach and the advantages and limitations of this transcallosal, interseptal approach are described.

Pregnancy-associated subacute hemorrhage into a prolactinoma resulting in diabetes insipidus.

A young woman with a small pituitary tumor associated with hyperprolactinemia developed subacute intrapituitary hemorrhage during the third trimester of pregnancy and presented with central diabetes insipidus. Magnetic resonance imaging established the diagnosis. After transsphenoidal surgery, her visual findings resolved, and the patient had an uneventful spontaneous delivery.