Rabbit urethral regeneration using small intestinal submucosa onlay grafts.

OBJECTIVES: To determine if small intestinal submucosa (SIS) can evoke urethral regeneration. METHODS: Twenty male white New Zealand rabbits were assigned to one of three experimental groups. Group 1 (n = 4) underwent simple urethrotomy and closure. Group 2 (n = 8), a second control group, underwent an onlay urethroplasty with a graft of full-thickness preputial skin from the host rabbit. Group 3 (n = 8) underwent an onlay urethroplasty with an SIS graft. RESULTS: All eight SIS onlay grafts promoted regeneration of the normal rabbit epithelium supported by a well-vascularized collagen and smooth muscle backing. Preputial free onlay grafts maintained a keratinizing squamous cell epithelium with a poor supportive backing, which resulted in the formation of urethral diverticulum. CONCLUSIONS: SIS onlay patch grafts for urethroplasty promote rabbit urethral regeneration.

Malignant testicular neoplasms in immunosuppressed patients.

PURPOSE: Testicular cancers were studied in patients on immunosuppression. MATERIALS AND METHODS: A retrospective analysis was done of testicular cancer in patients on immunosuppression reported on between 1975 and 1995. RESULTS: The management schemes adopted in the immunosuppressed population followed the generally accepted management concepts. No patient with low stage (A to B1) disease died of testis cancer. Only 4 of 66 patients (6.1%) with the acquired immunodeficiency syndrome died of testis cancer compared to 5 of 20 (25%) after transplantation, implying significantly higher cause specific mortality in post-transplant patients (Fisher's exact test, p < 0.01). The incidence of adverse effect of therapy did not differ from the expected incidence in other patients. CONCLUSIONS: Patients on immunosuppression with testicular neoplasms should be treated in the standard fashion as indicated by tumor histology and stage of disease, since most will tolerate therapy and benefit from the standard treatment protocols.

Enterocystoplasty: the star modification.

PURPOSE: A modification of sagittal cystoplasty is described that maximally reconfigures the native neuropathic bladder, as required in enterocystoplasty. MATERIALS AND METHODS: The star modification incorporates lateral cystotomies with anteroposterior cystotomy, as in the widely used sagittal clamshell technique. RESULTS: Enterocystoplasty was performed in 27 patients with various bowel segments using this technique and none has had complications attributable to cystoplasty after a mean followup of 2.5 years. CONCLUSIONS: Star reconfiguration defunctionalizes any potential noncompliant or hyperreflexic tendencies inherent to the neuropathic bladder before augmentation. In addition, the modification provides a technical advantage by increasing the linear length of the edge available for the anastomosis of bowel to bladder.

The prosthesis salvage operation: immediate replacement of the infected penile prosthesis.

PURPOSE: We describe our experience with salvage of the infected penile prosthesis at initial presentation in 11 patients. MATERIALS AND METHODS: All patients with prosthesis infection who presented since 1991 were considered for salvage surgery. Contraindications to a salvage operation included necrotic infections, diabetic patients with purulence in the corporeal bodies, rapidly developing infections and erosion of the device cylinders. RESULTS: In 1 patient in this group a salvage attempt was repeated after re-infection, for an overall success rate of 91%. Mean followup for the group was 21 months (range 9 to 42). Staphylococcus epidermidis was the infecting organism in 75% of our patients. CONCLUSIONS: Our experience demonstrates the safety and advantages of the immediate salvage technique.

Management of infected penile implants.

Penile prosthesis implantation is associated with a relatively low wound infection rate (3%). Proper adherence to antiseptic principles has kept the incidence low. When an infection does occur, one has the option of removing the device, allowing the infection to clear and possibly returning at a later date for reimplantation, or a salvage procedure, i.e., removing all foreign material, cleansing the wound, and reinserting a new device. The experience with salvage has resulted in approximately 80-90% success in saving the erectile abilities in a number of series.

Pharmacokinetics of dopamine in critically ill newborn infants.

Dopamine pharmacokinetics was investigated in 14 critically ill newborn infants ranging from 27 to 43 weeks of gestational age and from 0.9 to greater than 4 kg birth weight. Plasma clearance rate was determined from dopamine levels during controlled infusions under actual clinical conditions. Dopamine was administered in stepwise increasing doses up to 8 micrograms/kg/min. Dopamine concentration and dopamine clearance rate were determined from duplicate samples drawn during each infusion in each patient. Steady-state plasma dopamine concentrations and plasma clearance rates were observed within 20 minutes at each infusion. Plasma dopamine concentration ranged from 0.5 ng/ml before infusion to almost 70 ng/ml at an infusion rate of 4 to 8 micrograms/kg/min. There was a linear correlation between infusion rate and plasma dopamine concentration (r = 0.68, p less than 0.001). Neither plasma dopamine concentration nor infusion rate had a significant effect on clearance rate. These data are consistent with first-order kinetics for administered dopamine in critically ill neonates over the range of concentrations studied.

Thresholds for physiological effects of plasma catecholamines in fetal sheep.

To clarify the physiological role for the marked increases in circulating norepinephrine (NE) and epinephrine (E) that occur at birth, we performed graded infusions of NE and E in preterm (131 days) and full-term (142 days) fetal sheep. A variety of hemodynamic, metabolic, and endocrine responses to stepwise increases in plasma catecholamine levels were analyzed by computer-based graphical analysis of the dose-response curves. We determined the "threshold" value or minimum plasma concentration necessary to produce discernible effects. We observed increases in systolic blood pressure, diastolic blood pressure, and dP/dt beginning at plasma concentrations of 500-800 pg/ml of NE or E. In contrast, increases in plasma free fatty acid and glucose levels were observed at E concentrations as low as 50-100 pg/ml. Full-term animals had generally lower thresholds and higher peak responses than preterm animals. Because these thresholds for infused NE and E are well within the range of plasma catecholamine values seen at birth, these results underscore the importance of circulating catecholamines in the events of neonatal adaptation.

Dopamine pharmacokinetics in critically ill newborn infants.

To compare clinical responses with plasma concentrations of dopamine and to compare dopamine pharmacokinetics in infants of different gestational age or clinical condition, dopamine was administered under carefully controlled conditions of dose and rate of infusion. The dose was increased stepwise from 1 to 2, to 2 to 4, and 4 to 8 micrograms/kg/min. Plasma concentrations of catecholamines, including dopamine, were compared with blood pressure, heart rate, and Doppler cardiac output. The data were analyzed to determine the threshold or minimal plasma concentration of dopamine necessary to produce discernible effects. Plasma clearance rate was calculated from steady-state plasma concentrations. The average threshold for increases in mean arterial pressure was 50% below that for increases in heart rate. Improvements in arterial pressure were noted before and at lower thresholds than for increases in heart rate. Serial echocardiographic data showed dose-dependent increases in cardiac output and stroke volume without significant change in heart rate or systemic vascular resistance. Thresholds and plasma clearance values were similar in infants of gestational age 27 to 42 weeks and birth weights 900 to 4300 g. Administration of dopamine at initial dosages lower than commonly recommended, followed by incremental increase in dose, may be associated with improved left ventricular performance with avoidance of undesirable tachycardia and arrhythmias.

The effect of chemical sympathectomy on catecholamine release at birth.

The precise source of circulating catecholamine (CA) at birth and their role in circulatory adaptation is unclear. In order to determine the contribution of increased postganglionic sympathetic nerve activity to the CA surge at birth, we induced complete sympathectomy in near term fetal lambs prior to delivery by giving 6-hydroxydopamine. Chronically catheterized fetal sheep received either 6-hydroxydopamine (n = 5) or control infusion (n = 6). Chemical sympathectomy was verified by tyramine infusion. Lambs were delivered at 142 +/- 1 days of gestation and serial plasma CA, heart rate, blood pressure, cardiac output, blood gases, blood glucose, and free fatty acids, were measured before and for 4 h after delivery. Myocardial beta-adrenergic receptors and tissue CA concentration were determined following sacrifice. Baseline circulating norepinephrine (NE) values were lower in sympathectomized animals (183 +/- 45 versus 373 +/- 125 pg/ml, p less than 0.05) and epinephrine values were slightly higher (118 +/- 89 versus 48 +/- 1 pg/ml, NS). There was only a 2-fold increase in NE after cord cutting in sympathectomized animals while control animals had a 4-fold increase (peak NE values 354 +/- 121 versus 1305 +/- 363 pg/ml respectively, p less than 0.001). Epinephrine increased significantly in both groups and there were no significant differences between sympathectomized and control animals. Heart rate and blood pressure rose abruptly in both groups after cord cutting and there were no significant differences.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic clearance and plasma appearance rates of catecholamines in preterm and term fetal sheep.

Plasma catecholamines increase markedly during labor and delivery. Moreover we have noted greater increases at birth in preterm than term lambs. It was unclear whether these differences were due to differences in secretion or clearance. We therefore designed experiments to compare the metabolic clearance rates (MCR) and plasma appearance rates of norepinephrine (NE) and epinephrine (E) in chronically catheterized term (143 +/- 1 days) and preterm (131 +/- 1 days) fetal sheep. Two different techniques, radioisotope tracer techniques and infusion of cold hormones for estimation of clearance rates, were compared systematically in the same group of animals. The results demonstrate that MCR of NE in term fetuses (178 +/- 28 ml X kg-1 min-1) is similar to preterm fetuses (205 +/- 22 ml X kg-1 min-1) as is MCR for E (193 +/- 28 versus 170 +/- 33 ml X kg-1 min-1, respectively). Estimates of MCR from cold hormone infusion were highly dependent on infusion rate with estimates as much as 150% above that determined by isotope tracer infusions. Plasma appearance rates for both NE and E in term and preterm animals were similar. There were no detectable physiologic alterations during the tracer isotope infusions whereas infusions of cold hormone were associated with marked alterations in heart rate and blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)