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Biomedical subjects

W K Nichols

Publications and source records attributed to W K Nichols.

At least 19 recordsLinked to original sources
PubMed1992

Axillopopliteal bypass for limb salvage.

Forty-one axillopopliteal bypass grafts have been placed in 30 patients for limb salvage in the past 12 years. The mean patient age was 65.6 years; 8 were women; 19 smoked; and six had diabetes. Sixteen grafts were straight axillopopliteal bypass grafts, and 25 were sequential axillopopliteal bypass grafts. Cumulative life-table primary patency rates at 1, 2, and 3 years were 70%, 56%, and 43%, respectively; secondary patency rates were 73%, 57%, and 50%, respectively. Corresponding limb salvage rates were 86%, 69%, and 69%, respectively. Ringed polytetrafluoroethylene (PTFE) graft patency at 3 years was 61% versus 40% for unsupported PTFE grafts (p = 0.35). Ringed PTFE axillofemoral grafts with sequential femoropopliteal saphenous vein grafts had a 3-year patency of 67%. Graft patency was restored in 25% of occluded grafts by thrombectomy and in 80% of occluded grafts by thrombectomy with graft revision (p = 0.21). Cumulative 3-year patient survival was 48%. The 30-day operative mortality rate was 20%; patients operated on for graft infection had a 30-day operative mortality rate of 36%. The data support the use of axillopopliteal bypass for limb salvage when standard revascularization techniques are contraindicated. Long-term patency is enhanced by use of externally supported PTFE and sequential femoropopliteal saphenous vein.

Aged↗
PubMed1992

Bioactivation of halogenated hydrocarbons by rabbit pulmonary cells.

1,1-Dichloro-2,2-bis (4'-chlorophenyl)ethane (DDD), 1,2-dibromoethane (DBE) and trichloroethylene are three halogenated hydrocarbons that selectively bind to pulmonary epithelial cells and that may be pneumotoxic. The susceptibility of pulmonary cells and the mechanisms of cytotoxicity of these compounds were evaluated using enriched subpopulations of isolated rabbit lung cells incubated with DDD, DBE, and trichloroethylene. These chlorinated and brominated hydrocarbons were studied to evaluate their ability to induce selective pneumotoxicity by their bioactivation in three cell types, i.e. Clara cells, alveolar type II cells, and alveolar macrophages. Evidence of cytochrome P-450 bioactivation was assessed by utilizing the suicide inhibitor, 1-aminobenzotriazole (ABT) to ameliorate cytotoxicity. DDD, DBE and trichloroethylene were cytotoxic to Clara cells, type II cells and alveolar macrophages and the order of cell susceptibility to DDD was Clara > type II > macrophages. DBE and trichloroethylene were nonselectively cytotoxic. ABT reduced the cytotoxic effects of DDD and DBE in Clara cells. These studies indicated that all three compounds were toxic to isolated lung cells and that bioactivation of DDD and DBE in rabbit Clara cells to a cytotoxic intermediate was mediated, at least in part, by cytochrome P-450 oxidation.

Animals↗
PubMed1992

Swan neck presternal ("bath tub") catheter for peritoneal dialysis.

We hypothesize that the swan neck catheter for peritoneal dialysis with exit in the presternal area will have better exit site healing and a decreased incidence of exit site infection than currently used peritoneal dialysis catheters with the exit located on the abdomen. The chest is a very stable structure, with minimal wall motion, especially of the upper chest and over the sternum. Hence, a catheter exit located on the chest will be subjected to only minimal movement. Decreased piston like movement of the catheter at the exit site reduces inward transfer of outer microbial flora. Moreover, a tight garment is usually not worn on the chest and there is less pressure on the exit. Based on this rationale a new catheter (swan neck presternal) has been designed. The presternal peritoneal dialysis catheter is composed of two flexible (silicon rubber) tubes joined through a titanium connector at the time of implantation. The device has been dubbed as a "bath tube" catheter because, with the exit on the chest, a patient may take a tub bath without the risk of exit contamination due to submersion. Two such catheters were implanted in two patients. One patient had multiple problems (including chronic exit site infection) with a previously implanted swan neck Missouri 2 catheter, the other patient was originally rejected as a peritoneal dialysis candidate due to extreme obesity. Both catheters healed well in 6 weeks and the exits have not become infected during the first 8 months. These preliminary experiences with 2 catheters support the rationale of their design.

Catheters, Indwelling↗
PubMed1992

Six-year experience with swan neck catheters.

From the beginning of our continuous ambulatory peritoneal dialysis (CAPD) program in January 1977 until June 1985, we used Tenckhoff and Toronto Western Hospital catheters. Throughout these years catheter survival probabilities of about 30% at three years persisted unchanged and were similar to survival probabilities reported by the National CAPD Registry special survey for these catheters. The first improvement in catheter results regarding leaks was noted after the adoption of lateral catheter insertion. Malfunction was less using swan neck prototypes from August 1985 to April 1986. The latter catheters were made of 80 degrees arc angle tubing between 8.5 cm spaced cuffs and were inserted in a reversed U-shape tunnel with the incision at the top of the tunnel. The use of these catheters was abandoned because of high cuff extrusion and exit infection rates. The next generation of swan neck catheters, the swan neck Missouri 2 and 3 catheters with straight intraperitoneal segments, improved the results dramatically. These catheters were made of 180 degrees arc angle tubing between 5 or 3 cm spaced cuffs. The estimated survival probability of 61% at three years more than doubled compared to previously used catheters. Recently we modified the intraperitoneal segment of the catheters, replacing the straight segment with a coiled one. These modified catheters, the swan neck Missouri coiled catheters, have been used exclusively since February 1990. In addition to an acceptable survival probability of 88% at one year, there are two major advantages of these catheters, the same as for other coiled catheters: elimination of infusion pain due to a jet effect and pain related to straight catheter tip pressure on the peritoneum experienced by some patients.

Bacterial Infections↗
PubMed1992

Isolated traumatic accessory splenic rupture: a case report and literature review.

Although small and relatively protected, an accessory spleen can be the cause of acute intraabdominal symptoms following minimal trauma. Although a splenic fracture or laceration may not be apparent on by CT scan, the scan cannot rule out the possibility. The diagnosis of splenic injury should be entertained in light of appropriate history and physical findings. The case we present and prior similar cases are a useful review of isolated accessory splenic rupture due to blunt trauma.

Abdominal Injuries↗
PubMed1991

Morphology of peritoneal dialysis catheter tunnel: macroscopy and light microscopy.

There is scanty knowledge of the morphology of peritoneal dialysis catheter tunnels in humans, even though such knowledge may impact on peritoneal catheter design, implantation and postimplantation care. Past descriptions of catheter tunnels are based mainly on data from animal experiments. Based on these data, it has been assumed that epidermal spreading is inhibited by collagen fibers ingrown into the cuff. Our preliminary investigation indicated that this may not be the case in humans and led us to study catheter tunnel morphology in more detail. Eighteen catheter tunnels (2-5mm of tissue around the catheters) were removed in 17 peritoneal dialysis patients. The catheters were inserted 30 to 2013 days prior to removal (median 366 days). The catheters were removed electively or because of infectious or noninfectious complications. Contrary to the observations in animals, in only 1 case did epithelium extend to the cuff with only a minimal amount of granulation tissue present at the end of a 9 mm long sinus tract. In the remaining cases, the leading edge of the epithelium always met granulation tissue 1-14 mm from the exit, and the cuffs were found 8-33 mm from the exit. In tunnels older than 197 days, dense fibrous tissue was ingrown into the cuffs, and a dense fibrous capsule surrounded the cuff. The uninfected intercuff segment formed a pseudosheath, indistinguishable from a tendon sheath or synovial membrane. Infection in the catheter tunnel propagates through the part of the cuff adjacent to the tubing inside the capsule, suggesting that the cuff per se does not constitute a major barrier for spreading infection. This observation, by exclusion, infers that the beneficial role of an external cuff in decreasing exit infections is by providing firm anchorage of the catheter resulting in restriction of its piston like movement and thereby minimizing trauma and inward conveyance of outer sinus tract flora.

Adolescent↗
PubMed1991

Complete external iliac artery disruption after percutaneous aortic valvuloplasty in two young children: successful repair with hypogastric artery transposition.

The majority of vascular injuries in young children are iatrogenic. This is a report of two complete external iliac artery disruptions occurring during percutaneous transfemoral balloon aortic valvuloplasty in a 2-year-old and a 5-year-old child. The damaged external iliac artery was bypassed by extensively mobilizing the hypogastric surgery and rotating it upward to anastomose it to the proximal common femoral artery. Normal limb pulses, function, and growth were noted in follow-up.

Anastomosis, Surgical↗
PubMed1990

Bioactivation of 3-methylindole by isolated rabbit lung cells.

3-Methylindole (3MI) is a pneumotoxin that causes selective lung lesions indicative of Clara cell and alveolar epithelial cell damage in ruminants and rodents. The present study examined the cytotoxicity of 3MI to isolated rabbit Clara cells, type II alveolar epithelial cells, and alveolar macrophages. 3MI produced a dose-dependent cytotoxicity to Clara cells detectable within 1 hr of incubation at 37 degrees C which reached a maximum at 3 hr. Concentrations of 0.25 and 0.5 mM 3MI were cytotoxic to Clara cells, while type II and alveolar macrophages required 1 mM 3MI before cytotoxicity was observed. The cytochrome P450 suicide substrate inhibitor, 1-aminobenzotriazole, inhibited 3MI-induced cytotoxicity in Clara cells, type II cells, and alveolar macrophages. These observations were consistent with a cytochrome P450-mediated bioactivation of 3MI to a toxic intermediate. Studies with a trideuteromethyl analog of 3MI demonstrated a much reduced cytotoxicity to Clara cells as well as to type II cells, and macrophages. The deuterium isotope effect suggested that C-H bond breakage at the 3-methyl group is a requisite oxidative transformation in the bioactivation of 3MI to a selective lung cell cytotoxin. The selectivity of cellular cytotoxicity is probably associated with higher rates of bioactivation by Clara cell cytochrome P450 monooxygenases compared to those of type II cells and macrophages. These studies demonstrate that 3MI is bioactivated in isolated pulmonary cells without the intervention of other organs and that bioactivation requires functional cytochrome P450 enzymes.

Animals↗
PubMed1990

Total parathyroidectomy and autotransplantation in hyperplasia of the parathyroid gland.

Hyperparathyroidism caused by multiple-gland hyperplasia has traditionally been treated by subtotal parathyroidectomy. Excellent results have been reported by some, particularly in primary hyperparathyroidism, but other have reported a significant incidence of recurrent hyperparathyroidism. Since 1979, we have chosen to avoid the possibility of remedial exploration of the neck and its attendant risks by treating all patients with primary and secondary hyperplasia with total parathyroidectomy and heterotopic autotransplantation. A total of 20 patients were studied. There were no failures of grafts and no operative complications. We conclude that this procedure is a reliable and safe alternative in the treatment of primary or secondary hyperplasia of the parathyroid gland.

Adult↗
PubMed1989

Diagnostic dilemma of an unsuspected hyperfunctioning accessory parathyroid gland after total parathyroidectomy with autotransplantation in a peritoneal dialysis patient.

Persistent or recurrent hyperparathyroidism in patients with chronic renal failure may be a frustrating problem. We report a case history of a peritoneal dialysis patient who underwent total parathyroidectomy with autotransplantation for secondary hyperparathyroidism, developed tertiary hyperparathyroidism, and in an attempt to control hypercalcemia underwent seven partial resections of the autotransplant. Subsequently, a total excision of the parathyroid autograft was performed, but the patient continued to have hyperparathyroidism and unexpectedly was found to have a hyperplastic fifth parathyroid gland identified by thallium-technetium subtraction scan. The fifth gland was removed, and a part was implanted in the right forearm; however, the autoimplant had to be completely removed because of rapidly developing hypercalcemia. Hypercalcemia was controlled, but elevated levels of parathormone persisted. Remaining parathyroid tissue could not be found.

Female↗
PubMed1989

Transaxillary or supraclavicular decompression for the thoracic outlet syndrome. A comparison of the risks and benefits.

The difficult exposure with the transaxillary resection of the first rib (TAR) prompted an analysis of the TAR versus the supraclavicular approach (SCR) for decompressing the thoracic outlet in patients with thoracic outlet syndrome (TOS). Thirty-seven patients underwent 30 TAR and 15 underwent SCR for TOS. The operating time was similar for the two groups. Mean blood loss was 61 cc for the SCR group and 218 cc for the TAR group. There was one complication in the SCR group, a urinary tract infection, whereas the TAR group had 21 complications including pneumothorax (13), laceration of subclavian vessel (3), winged scapula (3), pleural effusion (1), and wound infection (1). Postoperative hospitalization averaged 3 and 5 days, respectively, for the SCR and TAR patients. All SCR patients and all but one TAR patient were improved or asymptomatic immediately postoperatively. Ninety-three per cent and 81 per cent, respectively, of SCR and TAR patients were improved at 2 months, whereas 100 per cent and 83 per cent, respectively, remained improved at a mean follow-up of 3 years. The significantly fewer complications, decreased blood loss and shorter postoperative hospitalization, noted in the SCR patients supports this approach as the preferred form of management for TOS.

Adult↗
PubMed1989

Late occurrence of aortoenteric fistula. After removal of a prosthetic graft.

Aortoenteric fistula is an uncommon but devastating complication of aortic surgery. The authors present a case of aortoenteric fistula occurring several years after resection of an aortic prosthesis that had not previously been involved in fistula formation. The pathophysiology and clinical evaluation of aortoenteric graft fistula are discussed.

Aorta, Thoracic↗
PubMed1989

Thrombocytopenia associated with heparin-coated catheters in patients with heparin-associated antiplatelet antibodies.

Thrombocytopenia was associated with the presence of heparin-coated pulmonary artery catheters in 12 patients with heparin-associated antiplatelet antibodies. The thrombocytopenia persisted so long as the heparin-coated catheters were in place, even when all other sources of heparin were discontinued. The high morbidity and mortality associated with heparin-induced thrombocytopenia mandates that heparin administration cease and that all heparin-coated catheters be removed from patients with heparin-associated antiplatelet antibodies.

Aged↗
PubMed1988

Surgical management of refractory venous stasis ulceration.

A 15-year experience with 27 patients, 20 to 75 years of age, with refractory venous stasis ulcers is presented. All patients had been managed with support hose, elevation, elastic wraps, Unna's paste boots, and graduated compression stockings. Because of multiple recurrences of their ulcers, the patients were offered surgical treatment to reduce the venous hypertension in the areas of ulceration. The 27 patients had 32 modified Linton procedures. Five had bilateral procedures. At the time of operation, 18 limbs had medial malleolar ulcers, five had bimalleolar ulcers, four had lateral ulcers, three had posterior ulcers, and two patients were free of ulcer. Medial incisions were used in 20 limbs, lateral incisions in six, medial and lateral incisions in three, and midposterior incisions in three. Split-thickness skin grafts were placed on six limbs the day of surgery and on 22 limbs 4 to 7 days later. Postoperative complications included deep venous thrombosis in two, partial flap necrosis in three, and cellulitis of the lower leg in three patients. Follow-up has ranged from 6 months to 10 years. During the most recent clinic visits, 21 limbs were completely healed, whereas six limbs had a recurrence of the ulcer. Five patients have been lost to follow-up. The good long-term results in 78% of the cases indicate that patients with recurrent venous stasis ulcers may receive lasting benefit from modified Linton procedures.

Adult↗
PubMed1988

Aneurysms and pseudoaneurysms of the superficial temporal artery caused by trauma.

Superficial temporal artery (STA) aneurysms as a result of trauma represent less than 1% of reported aneurysms. During the past 200 years only the type of trauma and the preferred treatment have significantly changed. Patients are generally young men with a recent history of blunt head trauma. They may complain of a mass, headache, or other vague symptoms. Neurologic defects are rare; however, if a neurologic deficit exists, the physician should consider either arteriography or a head CT scan to search for intracranial pathologic conditions. In most cases the diagnosis may be made by obtaining a complete history and physical examination. The treatment of choice is ligation and resection, which may be accomplished with the patient under local or general anesthesia. In rare instances, arteriography with selective embolization may be useful when the traumatic aneurysm is complicated by severe facial trauma. Three cases of STA aneurysms are presented. The history, pathophysiology, origin, presentation, diagnosis, differential diagnosis, and treatment of STA aneurysms are reviewed.

Adolescent↗
PubMed1987

Differential effects of cartilage-derived growth factor stimulation of collagen secretion by bovine aortic and microvascular endothelial cells.

Cartilage-derived growth factor (CDGF), a protein closely related to basic fibroblast growth factor, is known to have both mitogenic and chemokinetic properties in microvascular endothelial cells (MVEC). Because of the angiogenic properties of CDGF and its rate in accelerating wound repair, the capacity of this factor to stimulate both proliferation and matrix synthesis was compared in distinct populations of vascular endothelial cells: MVEC from bovine adrenal cortex and macrovascular endothelial cells from the bovine aorta (BAEC). No significant differences in the responses to mitogenic stimulation using CDGF (5-100 units/ml) were observed using MVEC and BAEC. Only rapidly dividing MVEC, however, showed significant increases in collagen secretion in the presence of CDGF. The differential responsiveness of these two cell populations to a defined growth factor underscores the phenotypic diversity of endothelium.

Animals↗
PubMed1986

Effect of heparin on platelet aggregation inhibited by PGI2, trifluoperazine and verapamil.

The enhancement of platelet aggregation by heparin in the presence of certain inhibitors of aggregation was investigated in an attempt to discern the mechanism through which heparin alters platelet function in plasma. These studies were performed by adding prostaglandin I2 (PGI2), verapamil, or trifluoperazine to platelet-rich plasma (PRP) in the presence or absence of heparin. Adenosine diphosphate (ADP), collagen, or arachidonic acid were used for induction of platelet aggregation. The inhibitory agents reduced platelet aggregation to 5 to 20% of control in the absence of heparin. When present in the reaction mixture along with the inhibitor, heparin restored aggregation to approximately 57 to 92% of control depending on the inhibitor and aggregating agent. This proaggregatory action of heparin was observed when heparin and PGI2 were preincubated together or separately for 20 min prior to the addition of PRP and ADP. Results were similar regardless of the sequence in which PGI2 and heparin were added to PRP, and irrespective of the time of incubation of platelets with PGI2. No suppression of platelet cyclic AMP concentration was observed with heparin alone. Heparin also failed to reduce the magnitude of platelet cyclic AMP accumulation promoted by PGI2, forskolin, or a mixture of PGI2 and forskolin. These observations suggest that heparin promoted platelet aggregation and partially overcame the effect of certain inhibitory agents by mechanism(s) that did not involve a reduction of platelet cyclic AMP.

Blood Platelets↗