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Biomedical subjects

R Izquierdo

Publications and source records attributed to R Izquierdo.

At least 37 records · Page 2Linked to original sources
PubMed1994

CT and MR of temporal bone malignancies primary and secondary to parotid carcinoma.

PURPOSE: To review the CT and MR characteristics of temporal bone malignancy, and to evaluate the relationship between malignancies of the temporal bone and parotid gland. METHODS: A group of 15 surgical patients with diagnosis of temporal bone malignancy were retrospectively reviewed. These included 11 cases of primary temporal bone malignancy and four cases of secondary carcinoma of the temporal bone from a primary tumor of the parotid gland. Three primary temporal bone malignancies were recurrences, and two secondary tumors were parotid recurrences. RESULTS: Five of the 11 patients with primary temporal bone malignancy had parotid infiltration (45%). All four patients with secondary temporal bone destruction caused by parotid carcinoma had erosion of the mastoid, two with erosion of the external auditory canal, and one of the middle ear. CONCLUSIONS: It is important radiographically to recognize the close relationship between malignancies of the temporal bone and parotid gland, because either may secondarily invade the other. Suspicion of malignancy in either the temporal bone or parotid gland necessitates complete imaging of the other structure. Temporal bone or skull base erosion were best seen on CT at bone algorithm. MR with and without infusion provided excellent delineation of soft-tissue tumor margins, muscle infiltration, intracranial extension, and vascular encasement.

Adolescent↗
PubMed1993

Use of vascularized fat from the rectus abdominis myocutaneous free flap territory to seal the dura of basicranial tumor resections.

Resection of large skull base tumors may sometimes result in extirpation defects that are not amenable to local tissue closure. Patients with these tumors require free tissue transfer for closure of the intracranial space after basicranial tumor extirpation. The deep inferior epigastric artery supplies the rectus abdominis muscle and the skin and subcutaneous tissue of the lower abdomen. The closure of massive, central defects can be performed with a free flap designed from the ample rectus abdominis vascular territory. This free tissue donor site has abundant and reliable well-vascularized skin and subcutaneous tissue that can be customized to seal these tenuous areas and provide three-dimensional reconstruction. We have modified the rectus abdominis myocutaneous free flap in seven patients for reconstruction of the skull base. The subcutaneous fat was sculptured to form a soft, vascularized "cork" and was used for obliteration of the irregular deep portions of defects at the midcranial base against the repaired or unrepaired dura. All patients who had the vascularized fat used to obliterate the deep space had successful closure of the defect without cerebral spinal fluid leak. There were two wound infections and one donor-site hernia in this group. The judicious use of the vascular territory of the deep inferior epigastric vessels can accomplish secure three-dimensional reconstruction of the skull base. The flap can be reliably transferred, and the vascularized subcutaneous fat can be used to sequester and seal the dura repair.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1993

Refinements using free-tissue transfer for complex cranial base reconstruction.

Resection of skull base tumors may sometimes result in massive extirpation defects that are not amenable to local tissue closure. Closure of large basicranial defects can be performed with either a myocutaneous, a deepithelialized myocutaneous, or a simple muscle free flap designed from the ample rectus abdominis vascular territory. This free-tissue donor site has abundant and reliable well-vascularized tissue that can easily be customized to seal these tenuous areas. The rectus abdominis muscle and its vascularized territory were used in 18 of 19 consecutive patients at our center to close basicranial ablation defects. Of these, 6 were rectus abdominis muscle flaps, 5 were myocutaneous rectus abdominis flaps, and 7 were deepithelialized rectus abdominis muscle flaps. All free flaps survived. The intracranial space was sealed successfully in all but one patient. This patient underwent reconstruction with a muscle free flap and had a postoperative cerebrospinal fluid leak. This complication could have been avoided by using a deepithelialized myocutaneous flap to obliterate the central dead space with the vascularized subcutaneous fat. Two patients experienced minor wound infections, and one had a subdural abscess that was fully contained by a free flap placed over the duraplasty. One patient had a donor-site hernia. There was no incidence of meningitis. Knowledge of the anatomy of the vascular territory of the deep inferior epigastric vessels can be used judiciously to secure three-dimensional reconstruction of the skull base. The donor site supplies ample tissue for reconstruction and allows individual tailoring for obliteration of geometrically complex extirpation defects in and around the cranial base without the need to reposition the patient.

Adolescent↗
PubMed1992

Attenuation of reperfusion-induced lipoperoxidation by systemic use of oxygen radical scavengers after pedicle occlusion.

Oxygen free radicals are implicated to cause tissue injury during ischemia and reperfusion and may play a central role in the no-reflow phenomena. Modulation of these substances has been suggested as a means of decreasing the amount of tissue loss due to ischemia and subsequent reperfusion. Pretreatment of tissues with a variety of agents has been reported to minimize the production of oxygen radicals and augment tissue survival after an ischemic insult. Ischemic clinical situations, however, usually present unexpectedly and thus pretreatment is not feasible. Our study evaluated the activity and effect of free radical scavengers delivered systemically during the ischemic interval to an ischemia/reperfusion rat intestinal model. Superoxide dismutase and dimethylthiourea were given systemically after occlusion and reperfusion to simulate a clinical sequence of a failing flap, that is, the vascular compromise, the diagnosis, and the successful resolution of the vascular embarrassment. Measurements of malonyldialdehyde (MDA), the end product of lipoperoxidation of cell walls, were compared with controls. Tissue histology was assessed and correlated with the use of these agents. A third group of rats was systemically alkalinized to attempt to shift the Bohr curve and decrease free oxygen substrate in the ischemic tissues on reperfusion. Rats treated with superoxide dismutase and dimethylthiourea showed significant reductions of MDA compared with nontreated rats (p less than 0.05), indicating attenuation of reperfusion lipoperoxidation. Systemic alkalinization of the rats did not significantly change the levels of MDA. Tissue histology showed severe injury in all ischemic groups regardless of the level of MDA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Massive craniofacial injuries from recreational fireworks: a report of three cases.

Recreational rocket injuries can result in massive destruction of facial soft tissues and bone and can produce long-term sequelae. This study reviews the cases of three patients who arrived at our medical center within a 3-week period in July 1990 who sustained severe craniofacial injuries from fireworks. A timely multidisciplinary approach is important in the care of these injuries, since there are usually associated serious ophthalmologic and cranial injuries that require immediate attention. We present the management dilemmas confronting the personnel who treat such injuries as well as tips on avoiding long-term complications.

Adult↗
PubMed1992

Complex cranial base trauma resulting from recreational fireworks injury: case reports and review of the literature.

Two patients who sustained complex skull base trauma secondary to recreational fireworks injuries are reported. Initial assessment and management included axial and coronal computerized tomography, control of hemorrhage, debridement of wound and brain, isolation of brain from external environment, and reconstruction of the cranial base floor. Secondary orbital and facial reconstruction used available bone fragments and iliac bone graft in one patient and vascularized free tissue transfer in the other. In both patients, reconstruction of both the intracranial and extracranial compartments was successful with acceptable cosmetic result. Modification of multiple conventional approaches, along with a multispecialty surgical team, was used to deal effectively with these unique cases.

Adult↗
PubMed1992

En bloc resection of an ethmoid carcinoma involving the orbit and medial wall of the cavernous sinus.

The involvement of the cavernous sinus by malignant tumors has limited their surgical treatment. We report here a successful en bloc resection of an invasive ethmoid carcinoma involving the cavernous sinus in a 46-year-old man. To prepare for surgery on this patient, a cadaver study was performed to investigate the feasibility of en bloc cavernous sinus resection and reconstruction. The preoperative evaluation, operative approach, and postoperative management are presented.

Adenocarcinoma↗
PubMed1991

The great auricular nerve revisited: pertinent anatomy for SMAS-platysma rhytidectomy.

Aesthetic platysma surgery during rhytidectomy has gained popularity for contour restoration of the jaw line, cervicomental angle, as well as anterior neck defects. The superficial musculoaponeurotic system-platysma flap is elevated and suspended in a cephaloposterior direction by suturing to the investing fascia overlying the sternocleidomastoid muscle and the mastoid bone. This procedure is usually performed without total visualization of the great auricular nerve, possibly placing this nerve at risk during suspension. Anatomical dissections of the great auricular nerve were performed bilaterally on 10 cadavers to delineate its course in the superior neck and identify anatomy pertinent to the elevation of flaps and placement of sutures during superficial musculoaponeurotic system-platysma suspension.

Cadaver↗
PubMed1989

Absorption of onlay bone grafts in immature rabbits: membranous versus enchondral bone and bone struts versus paste.

The absorption of onlay membranous and enchondral bone graft struts and paste was studied in immature New Zealand rabbits using a volume-displacement technique to determine the volume change in the grafts 8 weeks and 21 weeks after grafting. Membranous and enchondral bone paste does not survive as an onlay graft. Both enchondral and membranous bone graft struts undergo significant resorption (78% decreased volume in the enchondral grafts and 50% in the membranous bone grafts). These data support the clinical experience that both types of onlay bone grafts lose significant volume, and are in relative contradistinction to prior animal studies comparing membranous and enchondral onlay bone grafts.

Animals↗
PubMed1989

Effect of probenecid and benzbromarone on gluconeogenesis in isolated rat liver cells.

The effect of benzbromarone on gluconeogenesis from several gluconeogenic substrates in isolated rat liver cells is reported. Benzbromarone inhibited glucose synthesis from all substrates employed when the drug was used at concentrations half to ten times greater than its therapeutic plasma levels. This inhibition was more pronounced from lactate and pyruvate than from fructose and glycerol. The results are compared with those obtained for probenecid, a classical uricosuric drug. We found that probenecid inhibited the pathway in the same way as benzbromarone.

Animals↗
PubMed1988

Inhibition of purine catabolism by benzbromarone in isolated rat liver cells. Comparison with allopurinol and probenecid.

Benzbromarone, a potent uricosuric agent, inhibited allantoin production in isolated hepatocytes at concentrations half to ten times greater than therapeutic plasma levels of the drug. In addition, the drug at these concentrations also markedly inhibited xanthine oxidase (EC 1.2.1.37), an enzyme involved in the regulation of this pathway. We found that allopurinol is several times superior to benzbromarone in the lowering of allantoin production (if they are compared in terms of their relative therapeutic levels), and that probenecid had no effect on it.

Allopurinol↗
PubMed1985

Serum calcium metabolism in acute experimental pancreatitis.

Serum calcium changes in severe pancreatitis were studied in 23 dogs. Twelve dogs underwent duodenotomy and served as controls. Pancreatitis was induced in the other 11 by autologous bile injection (1 ml/kg) into the pancreatic duct. Serum amylase, total calcium, ionized calcium, albumin, magnesium, chloride, phosphorous, parathyroid hormone (PTH), and calcitonin were measured at 0, 1/2, 1, 3, 6, 24, 48, and 72 hours after duodenotomy or bile injection. Serum amylase levels became significantly elevated in all dogs with pancreatitis at 30 minutes (p less than 0.01) and remained so throughout the entire experiment. Total calcium levels dropped significantly 30 minutes after pancreatitis was induced from 10.0 +/- 0.3 mg/dl compared with 8.8 +/- 0.4 mg/dl in control dogs (p less than 0.05) and remained statistically lower for as long as 1 hour. Ionized calcium levels were significantly lower than were those of control dogs at 1/2, 1, 3, and 6 hours (p less than 0.05). Serum magnesium and chloride levels showed no significant changes between both groups. The only significant difference in phosphorus values was at 6 hours when they were higher in dogs with pancreatitis than in controls (6.2 +/- 0.3 mg/dl versus 4.8 +/- 0.4 mg/dl; p less than 0.05). Serum albumin levels remained unchanged throughout the study except for 48 hours when they were significantly lower in animals with pancreatitis (p less than 0.02). PTH levels were significantly greater in dogs with pancreatitis than in controls at 1, 3, 6, and 24 hours (p less than 0.05). There was no significant difference in calcitonin levels between both groups. Ionized calcium is a more reliable indicator of calcium fluxes in acute experimental pancreatitis since it remains depressed longer than total serum calcium. The time course of PTH elevation indicates a reaction to hypocalcemia, and failure of PTH secretion is not the cause of hypocalcemia in pancreatitis. This study does not support elevation of calcitonin as a cause of hypocalcemia in acute pancreatitis.

Acute Disease↗
PubMed1984

Comparative study of protease inhibitors on coagulation abnormalities in canine pancreatitis.

Coagulation abnormalities induced by pancreatitis were studied in 36 dogs. The 12 dogs in group I underwent a duodenotomy alone. The six dogs in groups II, III, IV, and V had pancreatitis induced by bile injection (1 cc/kg) into the pancreatic duct. Twenty minutes after bile-induced pancreatitis, group III was given 1.0 mg/kg aprotinin (trasylol), group IV was given 10 mg/kg S-2441, a new synthetic protease inhibitor, and group V was given 0.5 mg/kg alpha 2-antitrypsin by intravenous infusion over 10 min. Blood was drawn for amylase, protime (PT), partial thromboplastin time (PTT), fibrinogen, and platelets, in addition to markers of hypercoagulation, fibrinopeptide A, and antithrombin III, and markers of fibrinolysis, B beta 15-42 immunoreactive peptide (IP), and alpha 2-antiplasmin at baseline, 1/2, 1, 3, 6, 24, 48, and 72 hr after duodenotomy or bile injection. There was no significant difference in PT, platelets, antithrombin III, and fibrinopeptide A among the five groups. With the induction of pancreatitis (group II), serum amylase was significantly elevated but fibrinogen only became elevated at 24 hr and PTT at 48 hr. The increase in B beta 15-42 IP seen 30 min after induction of pancreatitis and the decrease in alpha 2-antiplasmin were blunted by aprotinin, alpha 1-antitrypsin, and S-2441, but inhibition of the rise in amylase and B beta 15-42 IP only reached significance with S-2441 (P less than 0.05). Pancreatitis-induced fibrinolysis was inhibited by S-2441 suggesting that synthetic protease inhibitors may play a therapeutic role in pancreatitis.

Acute Disease↗