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Biomedical subjects

M L Urken

Publications and source records attributed to M L Urken.

At least 73 records · Page 4Linked to original sources
PubMed1994

Use of urokinase during secondary ischemia in experimental skin flaps.

The ability of urokinase to salvage experimental flaps after a secondary ischemic insult was investigated in a rat model. Unilateral abdominal island skin flaps based on the superficial inferior epigastric vessels were raised and subjected to either 4 or 6 hours of primary ischemia followed by 12 hours of reperfusion and varying lengths of secondary ischemia. At the conclusion of secondary ischemia, the flaps were perfused with either lactated Ringer's solution or urokinase. One group of flaps served as a control and received no postischemic perfusion washout. The secondary critical ischemia time at which 50% of the flaps failed clinically was greater for flaps perfused with urokinase. Furthermore, the survival rates for all flaps perfused with urokinase were significantly greater than either control flaps or flaps perfused with lactated Ringer's solution (p < 0.05). Flap survival decreased significantly in all groups with increasing primary and/or secondary ischemia time (p < 0.05).

Animals↗
PubMed1994

Iloprost improves survival of ischemic experimental skin flaps.

The ability of the prostacyclin analogue iloprost to improve survival of ischemic experimental skin flaps was investigated. Unilateral island skin flaps based on the superficial inferior epigastric vessels were raised in 70 rats and subjected to varying lengths of primary ischemia. The flaps were divided into the following four groups: group I, no perfusion washout; group II, postischemic washout with lactated Ringer's solution; group III, postischemic washout with urokinase; and group IV, postischemic washout with iloprost. Flap survival rates for group IV were significantly higher than all other groups (p < 0.05). The primary ischemia time at which 50% of the flaps failed was 8.9 hours for group I, 9.5 hours for group II, 13.3 hours for group III, and 15.3 hours for group IV. This is the first study to investigate the effect of iloprost on skin flap survival. Iloprost was found to be significantly more effective than urokinase in salvaging ischemic experimental skin flaps.

Animals↗
PubMed1994

The iliac crest composite flap for oromandibular reconstruction.

Reconstruction of oromandibular defects following tumor ablation remains a complex endeavor. Its outcome greatly influences a cancer patient's quality of life and ability to become re-integrated into society. The number and variety of reconstructive options attest to the complexity of the problem and to the failure of any one method to demonstrate its superiority. We have favored the iliac crest-internal oblique free flap because of the quality of the bone and flexibility of the soft tissues. These qualities make this flap the ideal option for reconstruction of through-and-through defects of the oral cavity. Our experience reveals that this flap is highly successful in restoring functional mastication in most patients and is associated with minimal donor site morbidity. It is important to recognize, however, that it represents one of many available techniques for the reconstruction of composite oral mandibular defects.

Bone Transplantation↗
PubMed1994

Radial forearm flaps.

Restoration of oral cavity and pharyngeal function following ablative surgery remains an elusive goal. Conventional reconstructive methods often achieve satisfactory wound healing, but the introduction of a dynamic anesthetic and bulky flaps into the oral cavity can interfere with the function of the residual soft tissues. This article examines the anatomy, harvest technique, and applicability of neurosensory radial forearm flaps to head and neck reconstruction with special attention to the attributes of this donor site which, at present, make the radial forearm flap the flap of choice for the reconstruction of a variety of oral cavity and pharyngeal defects.

Forearm↗
PubMed1993

UW solution as an experimental microvascular skin flap perfusate.

UW solution has been found to be an effective organ perfusate for transplantation. Initial studies in experimental pedicle skin flaps have also demonstrated its unique effectiveness in prolonged ischemia. To understand better the limits of its preservation properties without the influence of endothelial clamp damage, we have undertaken to study the properties of UW solution in experimental microvascular free flaps. Control, lactated Ringer's, and UW solutions were utilized in pedicle and microvascular free flaps in Sprague-Dawley rats over varying periods of ischemia. UW solution demonstrated a clear superiority over all other solutions in both flap models. In addition there also was a significant prolongation of critical ischemia time in UW-treated free flaps compared to pedicle flaps.

Adenosine↗
PubMed1993

Mobilization regimens for the prevention of jaw hypomobility in the radiated patient: a comparison of three techniques.

This study evaluated and compared the Therabite Jaw Motion Rehabilitation System (Therabite Corporation, Bryn Mawr, PA) to tongue blades as a technique for maintaining and/or improving mandibular range of motion in post-irradiated patients. Three groups of patients were evaluated and compared: 1) unassisted exercise, 2) mechanically assisted mandibular mobilization with stacked tongue depressors combined with unassisted exercise, and 3) the Therabite System combined with unassisted exercise. The initial average maximum incisal opening (MIO) for the study population was 21.6 mm, and did not vary significantly among the groups. Measurements were recorded at 2-week intervals for 10 weeks. At week 6 and thereafter, the net increase in MIO of group 3 (13.6 mm [+/- 1.6 mm]) was significantly greater than group 1 (6.0 mm [+/- 1.8 mm]) and group 2 (4.4 mm [+/- 2.1 mm]) (P < .05). The rate of improvement leveled after 4 week in group 1 and group 2. However, the rate of gain in MIO in the Therabite group (group 3) remained constant at 10 weeks. There was no statistical difference between groups 1 and 2.

Adult↗
PubMed1993

The additive beneficial effect of UW solution and urokinase on experimental microvascular free-flap survival.

Pharmacologic manipulation of free flaps to enhance tolerance to ischemia has become a subject of great interest in the research literature. In an effort to improve survival, perfusion washout of experimental free flaps was performed following an episode of primary ischemia. The perfusates utilized were lactated Ringer's solution (LR), University of Wisconsin solution (UW), a high-molecular-weight medium used in organ preservation, and urokinase, a thrombolytic agent. Seventy-five rats were used in this study and divided into groups of 5 each. A 3 x 6-cm abdominal free flap based on the superficial inferior epigastric vessels was raised in each rat. The free flaps were subjected to either 12 or 18 hr of primary ischemia. Following the period of ischemia, perfusion washout was performed with either LR, UW solution, or urokinase at increasing concentrations alone or in combination with UW solution. Urokinase was first evaluated as a perfusate alone at increasing concentrations. In the 12-hr ischemia group, free-flap survival was shown to increase from 0 percent in the LR-perfused flaps to 20 percent, 60 percent, and 80 percent in flaps perfused with 12,500, 25,000, and 100,000 U of urokinase, respectively (p < 0.05). A similar increase in survival was demonstrated in the 18-hr ischemia group, where 0 percent, 20 percent, and 40 percent of flaps survived following perfusion with 12,500, 25,000, and 100,000 U of urokinase, respectively (p < 0.05). Urokinase was then perfused along with UW solution to evaluate the combined effect on flap survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1993

Enhancement of fluorescein perfusion in experimental skin flaps following postischemic washout with iloprost, urokinase, verapamil, and University of Wisconsin solution.

The enhancement of blood flow in experimental skin flaps following postischemic perfusion washout was investigated in rats. Unilateral island skin flaps based on the superficial epigastric vessels were raised and subjected to 6 hr of primary ischemia. Group 1 was designated as a control and did not undergo postischemic perfusion washout. In the remaining rats, postischemic washout was performed with one of five agents: Group 2--lactated Ringer's solution; Group 3--University of Wisconsin solution, an organ preservation medium; Group 4--verapamil, a calcium channel blocker; Group 5--urokinase, a thrombolytic agent; Group 6--iloprost, a stable prostacyclin analog. Two hours following perfusion washout, fluorometric analysis revealed a statistically significant enhancement of blood flow in Groups 4, 5, and 6, compared to Groups 2 and 3 (p < 0.05). Furthermore, a significant increase in skin surface fluorescence was demonstrated in all the flaps that underwent perfusion washout, compared to the control flaps (p < 0.05). By analyzing skin surface fluorescence, the enhancement of nutritive blood flow in flaps, following postischemic perfusion washout, was evaluated. This is the first study in which the above pharmacologic agents were compared in a quantitative manner.

Adenosine↗
PubMed1993

Imaging the postoperative neck.

The variety of cervical lymphadenectomy and neck reconstructive procedures that have been developed in the past 20 years has led to confusion about nomenclature in the literature. In addition, some of these operations result in gross alteration of the normal anatomy. The authors review the present classification system for cervical lymph nodes and various lymphadenectomy and reconstructive procedures. Examples of typical postoperative images are given. A protocol for postoperative follow-up is presented, which calls for imaging for 5 years after surgery. Finally, the authors review their experience with 400 cases, 276 of which were initially classified as having no clinical evidence of disease. Recurrence developed in 68 of these (in 62 [91%] within 4-18 months of surgery). Imaging findings altered the postoperative salvage plan in 17 (25%). Clinically occult disease was found at sectional imaging in 47 (17%).

Head and Neck Neoplasms↗
PubMed1993

Prolongation of secondary critical ischemia time of experimental skin flaps using UW solution as a normothermic perfusate.

A myriad of investigations have been published on the pharmacologic manipulation of flaps to enhance tolerance to ischemia. We recently reported a threefold increase in ischemic tolerance of the rat abdominal skin flap pedicle after 6 hours of primary ischemia and 12 hours of reperfusion. Flaps underwent normothermic perfusion washout with lactated Ringer's or U.W. solution, a newly developed organ preservation medium. Perfusion washouts were performed at one of three different points in the protocol: (1) onset of primary ischemia; (2) onset of secondary ischemia; or (3) 2 hours after onset of secondary ischemia. The last group was used to simulate the clinical situation in which flaps are discovered and salvage procedures instituted at a delayed time interval. This is the longest normothermic ischemic interval reported. We undertook the present study to determine the utility of the U.W solution in prolonging the tolerance of the flap to a second ischemic insult after a period of reperfusion. Seventy-five unilateral rat abdominal skin flaps were raised. Secondary ischemia was produced by placing a microvascular clamp across the inferior epigastric pedicle. Flap survival was assessed at 1 week postoperatively. While none of the nonperfused flaps survived 8 hours of secondary ischemia, at least 50% of the U.W. perfused flaps survived an average of 14 hours of secondary ischemia. Lactated Ringer's perfusion washout only modestly increased the ischemic tolerance. Perfusion washout in the secondary ischemic phase improved the ischemic tolerance to a significantly greater degree than in the primary ischemic interval.

Adenosine↗
PubMed1993

Hemodynamics of the rodent abdominal skin flap following primary ischemia.

The effect of varying periods of ischemia and reperfusion times on subsequent blood flow was studied in the rodent abdominal skin flap. Using perfusion fluorometry, measurements of blood flow were quantified in 60 Sprague-Dawley rats undergoing clamp-induced ischemic periods ranging from 0 to 6 hours and reperfusion times ranging from 2 to 8 hours. Flaps subjected to ischemia times of 0, 2, 4, or 6 hours require 8 hours of reperfusion time before reaching baseline levels of blood flow. Blood flow in flaps subjected to 6 hours of ischemia was statistically less than the flow in flaps ischemic for 0, 2, and 4 hours and was directly related to length of reperfusion. These results demonstrate that flap perfusion does not fully take place immediately after clamp release. The factors thought to be responsible for these findings and the implications for the design and interpretation of flap ischemia experiments are discussed.

Abdomen↗
PubMed1992

New approach to the management of airway obstruction in "high risk" neonates.

Epignathus is a rare tumor of newborns that is associated with a high mortality secondary to airway obstruction in the neonatal period. Due to recent advances in prenatal ultrasound and magnetic resonance imaging techniques, accurate in utero diagnosis of this rare teratoma will enable the health care team to prepare for "emergency" management of a difficult airway. We present a case of a newborn with a large epignathus diagnosed prenatally who underwent tracheotomy with intact maternal-fetal circulation. After airway stabilization, maternal-fetal circulation was interrupted and the epignathus was successfully removed. To our knowledge, this is the first extrauterine surgical procedure successfully performed using this technique. A new approach to airway management in "high risk" neonates involving the cooperative efforts of pediatricians, neonatologists, anesthesiologists, and otolaryngologists is presented.

Airway Obstruction↗
PubMed1992

The superior trapezius myocutaneous flap in head and neck reconstruction.

The superior trapezius myocutaneous flap, based on the paraspinous perforating branches of the intercostal vessels, is generally not a first-line choice for reconstruction of head and neck defects. However, after wound breakdown following radical neck dissection and radiation therapy, the superior trapezius flap is extremely reliable for coverage of exposed major neck vessels. The flap was used in 30 patients undergoing lateral neck reconstruction. All 30 patients had undergone prior neck dissection and all but two had undergone prior radiation therapy. There were no flap failures. The superior trapezius flap is unique among other regional myocutaneous flaps presently in use in that it has a superiorly based pedicle, which reduces the problem of gravitational pull on the suture lines of severely unfavorable recipient beds. Another advantage of using the denervated muscle of this flap is that it imposes no additional functional loss. The deficiencies of this flap are primarily related to its limited arc of rotation, thereby precluding its use when resurfacing defects that extend beyond the midline of the neck. The reliability of the superior trapezius flap after neck dissection can be explained by the angiosome concept. Based on that concept, previous ligation of the transverse cervical vessels during a neck dissection serves to simultaneously stage this flap, thereby improving its reliability and potential surface area available.

Adult↗
PubMed1992

Management of the paralyzed face with microneurovascular free muscle transfer.

Facial paralysis is a devastating physical condition in which no single therapeutic approach consistently restores mimetic facial expression. The purpose of this article is to review the current treatment modalities for facial paralysis with particular emphasis on the indications for using free flaps to achieve facial reanimation. Primary attention is given toward rehabilitation of the lower two thirds of the face. The various neuromuscular free flaps used for facial reanimation are described and their merits and deficiencies are discussed.

Facial Paralysis↗
PubMed1992

Paraganglioma of the inferior laryngeal paraganglia. A case report.

Laryngeal paragangliomas are uncommon, usually benign neoplasms. The overwhelming majority of these tumors are supraglottic, arising from the superior laryngeal parasympathetic paraganglia. Few paragangliomas of the infraglottic region have been described. We describe the case of a 35-year-old man with a family history of carotid body tumors who presented with an infraglottic paraganglioma.

Adult↗
PubMed1992

Surface sensibility of the floor of the mouth and tongue in healthy controls and in radiated patients.

Increased areas of anesthesia in the oral cavity have been shown to significantly impair oral function in normal individuals. In patients who undergo oral cavity reconstruction, loss of sensation plays a major role in producing disturbances in postoperative oral function. Free tissue transfer techniques have permitted the problem of sensory loss to be addressed through the use of sensate cutaneous free flaps, in which microneural anastomoses are performed between a sensory nerve supplying the flap and a recipient nerve in the head and neck. To critically assess the results of such reconstructions, the effect of sensory restoration on oral cavity rehabilitation must be studied. As a first step toward this goal, normal values for sensory discrimination of the floor of mouth and tongue are needed. Previous studies of oral sensation failed to examine the ventral tongue and floor of mouth. The purpose of this study is to determine the surface sensibility of these regions in healthy patients and in patients who received radiation therapy to the oral cavity. Sensation was evaluated using static and moving two-point discrimination in 90 healthy subjects divided equally into three age groups: 20 to 40 years, 41 to 60 years, and 61 to 80 years. In addition, 20 patients who received radiation therapy were studied. The mucosa of the dorsal and ventral aspects of the lateral tongue, tongue tip, and floor of mouth was examined. The tongue tip is the most sensitive area, followed by the dorsal lateral tongue, ventral lateral tongue, and floor of mouth. The effects of age and radiation therapy on sensory discrimination are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The combined sensate radical forearm and iliac crest free flaps for reconstruction of significant glossectomy-mandibulectomy defects.

The loss of motor and sensory function of the tongue following ablative surgery has a devastating effect on oral function. At the present time, there is no way to restore lost tongue musculature following partial glossectomy. The use of sensate cutaneous flaps has been shown to restore sensory feedback to reconstructed areas of the oral cavity. No single composite flap supplies a sensate soft-tissue component together with an osseous component of sufficient bone stock for functional mastication. In this article, the combination of the radial forearm free flap with the iliac crest osteocutaneous or osteomyocutaneous free flap is reported. The radial forearm free flap was used to resurface the resected portion of the tongue to provide maximum mobility and sensation. The lingual nerve was the recipient nerve for anastomosis to the antebrachial cutaneous nerves in all but one case. The iliac bone was used to reconstruct the mandible, with the iliac skin paddle or the internal oblique muscle used to reconstruct the neoridge. This combination of flaps was used in 10 patients. There was one flap failure due to vascular kinking from "piggybacking" the iliac crest to the distal end of the radial forearm flap. As a result, the use of two separate sets of recipient vessels is now advocated. Although a single composite free flap offers an excellent form of oromandibular reconstruction in most cases, it has been shown that oral function deteriorates when large areas of anesthesia are present in the oral cavity. We believe that this combination of two free flaps offers an opportunity for superior function in select patients with significant glossectomy and/or large mucosal defects.

Anastomosis, Surgical↗