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Biomedical subjects

D C Merrill

Publications and source records attributed to D C Merrill.

At least 73 records · Page 4Linked to original sources
PubMed1984

Mentor inflatable penile prosthesis: clinical experience in 52 patients.

The Mentor inflatable penile prosthesis is manufactured from Bioflex polyurethane, a material which is less elastic and more durable than silicone. Use of this new biocompatible polymer eliminates cylinder aneurysms and wear-induced cylinder leaks. The new prosthesis also incorporates a snap-on connector system designed to eliminate connector leaks and decrease operative time. The Mentor prosthesis has been implanted in 52 patients with organic impotence. The patients have been followed up for 2 to 16 months (average 8.3), the follow-up exceeding 1 year in 15 patients. A satisfactory cosmetic and functional result was achieved in 51 cases. Infection necessitated removal of the prosthesis in one patient. There were no pump, reservoir or tubing failures. After early connector failures there were no connector failures in the subsequent 48 patients. Additional complications included an incisional hernia and a cylinder failure which resulted from a manufacturing defect. There were no failures attributable to wear or material fatigue. The inherent reliability of this new prosthesis and the excellent functional and cosmetic results it produces justify its use in any patient who is a candidate for a penile prosthesis.

Adult↗
PubMed1984

Long-term influence of vasopressin on the control of arterial blood pressure independent of volume changes.

Studies were performed to ascertain the extent to which arterial blood pressure, and fluid and electrolyte changes seen with chronic elevations of plasma vasopressin (AVP) were caused by volume expansion or some other more direct cardiovascular or neural interactions of AVP. Group 1 (n = 7) dogs were infused with AVP (0.36 ng/kg/min) while total body weight and volume were maintained at a constant level by the use of an electronically controlled servocontrol system. Dogs in Group 2 (n = 6) were permitted to drink ad libitum during AVP infusion. Group 3 (n = 6) dogs were maintained with a constant level of H2O intake by intravenous infusion during two weeks AVP administration. The results indicate that chronic elevation of plasma AVP resulted in a prolonged elevation of arterial pressure only when there was a large expansion of total body water. Dogs with total body volume servocontrolled to a constant level (Group 1) and those with a moderate increase in volume (Group 2) exhibited no measureable change in mean arterial pressure during AVP infusion. Dogs with Fixed H2O intake (Group 3) retained a large fluid volume. They exhibited renal escape from AVP and large decreases of plasma osmolality, sodium concentration and plasma renin activity. With as libitum drinking (Group 2), only mild volume expansion occurred which resulted in a partial escape from the volume-retaining effects and smaller decreases of plasma osmolality and sodium. When total body weight and volume were servocontrolled to a constant level, no renal escape occurred and hype-osmolality, hyponatraemia and hyporeninaemia were not observed (Group 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Mentor inflatable penile prosthesis.

The new Mentor prosthesis is similar in appearance to the Scott inflatable penile prosthesis, consisting of a pump, a reservoir, and two penile cylinders. The penile cylinders of the Mentor prosthesis are constructed of Bioflex polyurethane, a new polymer which is more durable and less elastic than silicone. The use of Bioflex cylinders should increase device longevity and eliminate cylinder aneurysms. It also may be possible to correct penile deformities produced by silicone cylinders which have formed aneurysms by replacing the dilated cylinders with Bioflex cylinders. The new Mentor prosthesis utilizes snap-on connectors which rely on plastic clamps rather than suture ties to fix tubings to connectors. This method of attaching tubing to connectors will reduce operating time and should reduce the incidence of connector leaks.

Erectile Dysfunction↗
PubMed1983

Clinical experience with Scott inflatable penile prosthesis in 150 patients.

The Scott inflatable penile prosthesis was implanted in 150 patients with organic (89%) and psychologic (11%) impotency from 1979 to 1982. The patients were followed up for an average of twenty-five (6-46) months. A satisfactory result was achieved in 133 (89%) patients. Forty-nine major complications occurred in 38 patients. Forty-four surgical procedures were performed in 33 patients to correct mechanical or technical complications (32), replace the device (9), or remove the device (3). Two patients refused corrective surgery, and the complications could not be corrected in 2 patients. Cylinder leaks (15), leaks at tubing/connector junctions (14), and cylinder aneurysms (7) were responsible for most of the mechanical failures. Additional refinements in surgical technique will not eliminate these problems. Device modifications should be made to increase cylinder durability, to eliminate the need for suture ligation of tubing/connector junctions, and to assure symmetrical cylinder expansion.

Adult↗
PubMed1983

Influence of daily sodium intake on vasopressin secretion and drinking in dogs.

Studies were carried out to determine the relationship between daily sodium intake, drinking, and vasopressin (AVP) secretion in normal conscious dogs. Chronic responses to 5-day elevations of daily sodium intake (200 meq/day) and 2-wk decreases in daily sodium intake (5 meq/day) were determined. Dogs were studied with ad libitum drinking and with water intake restricted to the amount drunk during the normal-sodium (30 meq/day) control period. Although acute elevations of plasma AVP occurred after a normal (40 meq Na) gastric load, chronic high-sodium intake resulted in no change of steady-state plasma AVP levels or daily AVP excretion (UAVP) with ad libitum drinking. Total water intake and frequency of drinking, however, increased nearly fourfold. In the absence of excess drinking, plasma AVP and UAVP both exhibited a nearly sixfold increase during the period of high-sodium intake. Despite elevations of plasma AVP, daily urine volume increased and urine osmolality rose only gradually during the 5 days of high-sodium intake. Chronic low-sodium intake also did not alter plasma AVP, but total water intake was reduced 20%. The data indicate that with water available, extracellular osmolality is controlled predominantly by drinking rather than by AVP secretion, that either osmolality or sodium concentration is the predominant controller of drinking and AVP secretion, and that daily water excretion need not be related directly to plasma AVP.

Animals↗
PubMed1979

Laboratory comparison of urethral profilometry techniques.

A comparison of urethral pressure profiles performed with the air infusion, water infusion, membrane catheter, and transducer tip catheter techniques was made in a canine model. The gas and water infusion methods gave statistically identical results if the gas studies were performed at flow rates of 100 ml./min. and pull rates of 5 cm./min. The transducer tip catheter and the gas and water infusion techniques gave accurate recordings of peak urethral pressure but were incapable of detecting multiple areas of urethral compression. The transducer tip catheter measurements often were difficult to interpret because of rotation and flexion artifact. The membrane catheter was capable of recording multiple areas of urethral compression but gave spuriously high recordings of peak urethral pressure. We conclude that none of the methods tested will give accurate recordings of urethral pressure in all clinical situations.

Animals↗
PubMed1979

The treatment of detrusor incontinence by electrical stimulation.

Cystometrograms were done on 20 patients before and during transrectal stimulation to determine if electrical stimulation increased the detrusor reflex threshold. In 4 patients the detrusor reflex threshold was increased during stimulation and urinary continence was restored. However, each patient became incontinent when transrectal stimulation was discontinued for 1 to 5 days. Thus, cyclic periods of stimulation were necessary to maintain the beneficial effects of electrical stimulation and a permanent pelvic floor stimulator was implanted since chronic transrectal stimulation was inconvenient.

Adult↗
PubMed1978

Effect of baclofen and dantrolene on bladder stimulator-induced detrusor-sphincter dyssynergia in dogs.

The effect of baclofen (Lioresal) and dantrolene (Dantrium) on bladder stimulation-induced detrusor-sphincter dyssynergia was studied in normal and chronic T-10 paraplegic dogs. Dantrolene, which depresses skeletal muscle contractility, had little effect on electrically evoked contractions of the urethral sphincter in dogs. Baclofen, which acts centrally by potentiating presynaptic inhibition, depressed the pudendal to pudendal nerve reflex and decreased urethral resistance during bladder stimulation.

Aminobutyrates↗
PubMed1978

Comparative study of air and water measurements of peak and stabilized static urethral pressures.

Air and water were forced through female dogs' urethras to determine static urethral pressures. The cauda equina was sectioned to eliminate reflex responses to urethral manipulation, and the urethras were compressed circumferentially with inflatable Silastic cuffs. The peak and stabilized urethral pressures were recorded at flow rates between 20 and 150 ml./min. while cuff pressures were varied between 0 and 100 cm. of water. When the fluid recordings of static urethral pressure were compared with Millar transducer tip catheter measurements of urethral pressure, there were no statistically significant differences between the air cystometer, aneroid sphygmomanometer, and Millar catheter recordings of urethral pressure. At these high flow rates, the water recordings of urethral pressure were significantly higher than the Millar catheter determinations of static uretheral pressure.

Air↗
PubMed1978

A laboratory evaluation of a new hydraulic incontinence device.

A new hydraulic incontinence device is described. The device is physiologic because it can be deflated to allow resistance-free voiding and it is designed to respond instantaneously to fluctuations in intra-abdominal pressure, irrespective of whether the bulb is placed at the level of the bulbous urethra or the bladder neck. The device is simple, consisting only of a urethral cuff, an abdominal reservoir and 1 pump containing a single valve.

Abdomen↗
PubMed1977

Failure to control postprostatectomy urinary incontinence by urethral compression.

A modification of Kaufman's urinary incontinence device was implanted unsuccessfully in 5 patients. This device achieved passive urinary continence in each of these patients; however, all patients continued to experience moderate to severe stress incontinence. The results of this study challenge the concept that static urethral compression can achieve total urinary continence in patients with postprostatectomy incontinence.

Aged↗
PubMed1977

Modified thoracoabdominal approach to the kidney and retroperitoneal tissue.

Exposure to the retroperitoneal space may be improved by performing thoracotomy through the 8th rib bed rather than the 9th or 10th and by combining a subcostal incision with the standard longitudinal abdominal incision. This modification of the standard thoracoabdominal incision has been used to remove giant hypernephromas, to perform radical nephrectomies with node dissection and to remove retroperitoneal lymphatic structures in non-seminomatous testis tumors.

Adenocarcinoma↗
PubMed1977

Electric pelvic floor stimulation. Mechanism of action.

This canine study delineates two mechanisms of action for electric pelvic floor stimulation. The electric stimulation increases urethral resistance by activating the pelvic floor skeletal muscle. Direct pudendal nerve stimulation is the most effective method for applying the electric stimulus. The two electric devices presently employed clinically, the pelvic floor stimulator and the transrectal stimulator, are less effective methods for increasing pelvic floor skeletal muscle contraction. Electric stimulation also activates a pudendal-to-pelvic nerve reflex that depresses or eliminates uninhibited detrusor contractions.

Animals↗
PubMed1976

Experience with the Small-Carrion penile prosthesis.

The Small-Carrion prosthesis has been implanted successfully in 14 of 15 patients. These prostheses are implanted through a dorsal midline penile incision which simplifies the procedure. The perineal approach is preferred for keloid formers and paraplegics who will use a condom catheter. Operative failure may be decreased by paying particular attention to the size of prosthesis implanted and the positioning of its distal tip.

Adult↗
PubMed1975

Urinary incontinence. Treatment with electrical stimulation of the pelvic floor.

Electrical pelvic floor stimulation may be administered either externally by the transrectal tampon or internally with the implantable pelvic floor stimulator. This treatment modality requires intact pelvic floor innervation and therefore is unsuccessful in patients with pelvic floor denervation. Pelvic floor stimulation has been successful in patients with stress and with congenital, iatrogenic, and postoperative urinary incontinence.

Adolescent↗