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Biomedical subjects

William S Cobb

Publications and source records attributed to William S Cobb.

At least 19 recordsLinked to original sources
PubMed2006

Textile analysis of heavy weight, mid-weight, and light weight polypropylene mesh in a porcine ventral hernia model.

BACKGROUND: The purpose of this study was to assess the burst strength and stiffness of heavy weight (HW), mid-weight (MW), and light weight (LW) polypropylene mesh pre-implantation and 5 months post-implantation in a porcine ventral hernia model. MATERIALS AND METHODS: HW (95 g/cm2), MW (45 g/cm2), and LW (28 g/cm2) polypropylene were tested as dry samples (n = 8/mesh) before implantation using a stamp strain machine. Three weeks after creating four hernia defects in each mini-pig (n = 18), the polypropylene meshes (8 x 10 cm; 24/mesh type) were implanted in the preperitoneal space, ensuring 2 cm overlap circumferentially. At 5 months, the mesh was harvested en bloc with the abdominal wall. Testing of burst strength and stiffness was repeated on the ex vivo specimens. RESULTS: After implantation in the pig for 5 months, the mean burst strength and stiffness of HW and MW meshes remains the same. LW mesh with an absorbable monofilament in its weave has significant reductions in mean burst strength (P = 0.01) and mean stiffness (P < 0.0001). The burst strength for all meshes tested was much higher than measured for the abdominal wall fascia alone. The degree of shrinkage of the various weight meshes did not differ. CONCLUSION: A reduction in mean burst strength and stiffness occurs after 5 months implantation of LW polypropylene mesh with an absorbable monofilament. All meshes exhibited burst strengths that were much greater than the burst strength of the abdominal wall fascia alone. After tissue incorporation, the LW polypropylene mesh maintains mean burst strength comparable to MW polypropylene mesh, while becoming less stiff than HW mesh. Long-term, this may contribute to more physiological abdominal wall compliance after LW polypropylene mesh implantation.

Animals↗
PubMed2006

Laparoscopic ventral hernia repair in obese patients: a new standard of care.

HYPOTHESIS: Ventral abdominal hernias represent a frequent and often formidable clinical problem, especially in obese patients. Because laparoscopic ventral hernia repair (LVHR) results in few complications and a low recurrence rate, the use of minimally invasive techniques in this subgroup of patients may minimize perioperative complications and failure rates. DESIGN: Retrospective review of prospectively collected data. SETTING: Tertiary care hospital. PATIENTS: One hundred sixty-three obese patients (body mass index [calculated as weight in kilograms divided by the square of height in meters], > or =30) who underwent LVHR at our institution between July 1, 1998, and December 31, 2003. INTERVENTION: Laparoscopic ventral hernia repair with an expanded polytetrafluoroethylene mesh. MAIN OUTCOME MEASURES: Patient age, sex, body mass index, size of fascial defect and mesh, operating time, operative blood loss, length of hospitalization, complications, and hernia recurrences. RESULTS: Ninety-eight women and 65 men, with a mean body mass index of 38, underwent LVHR. Twenty patients (12.3%) had 21 postoperative complications. There was no perioperative mortality. The mean length of hospital stay was 2.6 days. The recurrence rate was 5.5% at a mean follow-up of 25 months (range, 1-73 months). CONCLUSIONS: A low rate of conversion to laparotomy, minimal perioperative morbidity, and the absence of perioperative mortality in this series indicate the safety of LVHR in obese patients with complex hernias. In addition, a success rate of more than 94.5% suggests improved efficacy of LVHR compared with the historical rates among control subjects undergoing open surgery. In experienced hands, LVHR may be the approach of choice for most patients with a body mass index of 30 or more.

Adult↗
PubMed2006

Laparoscopic versus open colostomy reversal: a comparative analysis.

Open colostomy reversal carries significant rates of wound infection, anastomotic leak, and incisional hernia which often limit its acceptance. We hypothesized that the laparoscopic approach to the restoration of intestinal continuity may result in lower perioperative morbidity and faster postoperative recovery. Twenty-two cases of laparoscopic colostomy reversals performed at a single institution were identified and compared to 22 randomly selected open colostomy closures performed during the same time period. Patients were compared based on demographics, previous indications for colostomy procedures, and perioperative outcomes. A total of 152 patients underwent reversal of left-sided colostomies during the study period. The laparoscopic approach was successful in 20 of 22 cases; there were 2 conversions to open (9%) secondary to inability to adequately mobilize the rectal stump. The laparoscopic and open groups were comparable based on mean age (54 years versus 49 years; P = 0.23), BMI (26 kg/m(2) versus 27 kg/m(2); P = 0.66), gender (9% males versus 13% males; P = 0.23), ASA Class (2.6 versus 2.3; P = 0.07), and history of previous intra-abdominal sepsis (17 versus 16 cases). Operative times were similar (158 versus 189 minutes; P = 0.16), and estimated blood loss was significantly less in the laparoscopic group (113 versus 270 ml; P = 0.01). No intraoperative complications occurred in the laparoscopic group and two enterotomies occurred in the open group. The laparoscopic group had earlier passage of flatus (3.5 versus 5.0 days; P = 0.001) and shorter hospitalization (4.2 versus 7.3 days; P = 0.001). Perioperative complications occurred in 3 (14%) laparoscopic and 13 (59%) open cases (P = 0.01). There was no mortality in this series. The laparoscopic approach can be safely used in the restoration of intestinal continuity. It results in a decreased perioperative morbidity and faster recovery, and it offers distinct advantages over the open approach to colostomy reversal.

Adult↗
PubMed2006

Prospective evaluation of adhesion formation and shrinkage of intra-abdominal prosthetics in a rabbit model.

Laparoscopic ventral hernia repair requires an intraperitoneal prosthetic; however, these materials are not without consequences. We evaluated host reaction to intraperitoneal placement of various prosthetics and the functional outcomes in an animal model. Mesh (n = 15 per mesh type) was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included ePTFE (DualMesh), ePTFE and polypropylene (Composix), polypropylene and oxidized regenerated cellulose (Proceed), and polypropylene (Marlex). Adhesion formation was evaluated at 1, 4, 8, and 16 weeks using 2-mm mini-laparoscopy. Adhesion area, adhesion tenacity, prosthetic shrinkage, and compliance were evaluated after mesh explantation at 16 weeks. DualMesh had significantly less adhesions than Proceed, Composix, or Marlex at 1, 4, 8, and 16 weeks (P < 0.0001). Marlex had significantly more adhesions than other meshes at each time point (P < 0.0001). There were no statistically significant differences in adhesions between Proceed and Composix meshes. After mesh explantation, the mean area of adhesions for Proceed (4.6%) was less than for Marlex (21.7%; P = 0.001). The adhesions to Marlex were statistically more tenacious than the DualMesh and Composix groups. Overall prosthetic shrinkage was statistically greater for DualMesh (34.7%) than for the remaining mesh types (P < 0.01). Mesh compliance was similar between the groups. Prosthetic materials demonstrate a wide variety of characteristics when placed inside the abdomen. Marlex formed more adhesions with greater tenacity than the other mesh types. DualMesh resulted in minimal adhesions, but it shrank more than the other mesh types. Each prosthetic generates a varied host reaction. Better understanding of these reactions can allow a suitable prosthetic to be chosen for a given patient in clinical practice.

Animals↗
PubMed2006

Intra-abdominal placement of antimicrobial-impregnated mesh is associated with noninfectious fever.

The antimicrobial, silver/chlorhexidine, when impregnated on mesh has been demonstrated to resist mesh infection in in vitro and in vivo models. The clinical, human systemic response to intraperitoneal placement of silver/chlorhexidine-impregnated mesh has not been investigated to date. Between October 2002 and November 2004, all in-patients undergoing laparoscopic ventral hernia repair were retrospectively analyzed. All repairs used expanded polytetraflouroethylene (ePTFE) Dual Mesh (DM) or ePTFE impregnated with silver/chlorhexidine, Dual Mesh Plus (DM+). Patient demographics, hernia characteristics, mesh type, operative details, and hospital course data were collected. Noninfectious fevers were defined as a temperature greater than 100.4 F without an identified source. Standard statistical methods were used. During the 2-year study period, 120 patients underwent laparoscopic ventral hernia repair (DM = 55, DM+ = 65). The two groups were similarly matched in terms of age, body mass index, American Society of Anesthesiologists score, defect size, and mesh size. Postoperative fever without an identified source occurred in 10 (18.2%) patients with DM and in 25 (38.5%) patients using DM+ (P = 0.015). A multivariant analysis revealed that only mesh type and body mass index predicted postoperative fever. All fevers resolved within the first 72 hours in the DM patients; however, 16 per cent of the DM+ group had persistent fevers of unknown origin after 72 hours. Within the DM+ group, patients with postoperative fevers had significantly longer postoperative stays (4.8 days vs 3.0 days; P = 0.009). The use of antimicrobial-impregnated ePTFE mesh with silver/chlorhexidine in laparoscopic ventral hernia repair is associated with noninfectious postoperative fever. In our patients, the evaluation and management of these fevers resulted in a significantly longer hospital stay.

Adult↗
PubMed2005

Normal intraabdominal pressure in healthy adults.

BACKGROUND: Intraabdominal pressure (IAP) has been considered responsible for adverse effects in trauma and other abdominal catastrophes as well as in formation and recurrence of hernias. To date, little information is available concerning IAP in normal persons. Our purpose in this study was to measure the normal range of IAP in healthy, nonobese adults and correlate these measurements with sex and body mass index (BMI). METHODS: After Institutional Review Board approval, 20 healthy young adults (< or =30 years old) with no prior history of abdominal surgery were enrolled. Pressure readings were obtained through a transurethral bladder (Foley) catheter. Each subject performed 13 different tasks including standing, sitting, bending at the waist, bending at the knees, performing abdominal crunches, jumping, climbing stairs, bench-pressing 25 pounds, arm curling 10 pounds, and performing a Valsalva and coughing while sitting and also while standing. Data were analyzed by Student's t-test and Pearson's correlation coefficients. RESULTS: Intraabdominal pressure was measured in 10 male and 10 female subjects. The mean age of the study group was 22.7 years (range, 18-30 years), and BMI averaged 24.6 kg/m(2) (range, 18.4-31.9 kg/m(2)). Mean IAP for sitting and standing were 16.7 and 20 mm Hg. Coughing and jumping generated the highest IAP (107.6 and 171 mm Hg, respectively). Lifting 10-pound weights and bending at the knees did not generate excessive levels of pressure with the maximum average of 25.5 mm Hg. The mean pressures were not different when comparing males and females during each maneuver. There was a significant correlation between higher BMI and increased IAP in 5 of 13 exercises. CONCLUSION: Normal IAP correlates with BMI but does not vary based on sex. The highest intraabdominal pressures in healthy patients are generated during coughing and jumping. Based on our observations, patients with higher BMI and chronic cough appear to generate significant elevation in IAP. Thus, this group of patients may potentially be at increased risk for abdominal wall hernia formation following surgery.

Abdomen↗
PubMed2005

Laparoscopic adrenalectomy for malignancy.

The superiority of the minimally invasive approach to adrenal resections has been well documented for benign pathology. With technical advances and increased experience, surgeons have successfully performed laparoscopic adrenalectomies for metastatic and primary malignancies of the adrenal gland. The technique of laparoscopic adrenalectomy as it pertains to malignant lesions is presented. A review of the literature demonstrates the safety and efficacy of laparoscopic adrenalectomy for metastatic colorectal, lung, and renal tumors. For primary adrenal malignancies, radical resections can be effectively performed laparoscopically; however, continued long-term follow-up is needed to establish the minimally invasive technique as the preferred approach.

Adrenal Gland Neoplasms↗
PubMed2005

Laparoscopic restoration of intestinal continuity after Hartmann's procedure.

BACKGROUND: Colostomy closure after a Hartmann's procedure typically requires a laparotomy. It also carries the risk of significant morbidity including anastomotic leak, wound infection, and incisional hernia. The aim of this study was to review our experience with laparoscopic restoration of intestinal continuity after Hartmann's procedure. METHODS: After institutional review board approval, we retrospectively reviewed the medical records of patients undergoing laparoscopic colostomy reversal between July 1997 and July 2004. RESULTS: Twenty-two patients were identified; all patients had left colon colostomies. A laparoscopic technique was used in 21 patients, and 1 patient underwent hand-assisted colostomy reversal concurrently with right radical nephrectomy. The laparoscopic approach was successful in 20 cases, and there were 2 conversions to open (9%) secondary to dense adhesions around the rectal stump. The mean time to closure of the colostomy was 168 days (range 69-385 days). The mean operative time was 158 minutes (range 84-356 minutes). The estimated blood loss averaged 114 mL (range 30-250 mL). The average length of hospitalization was 4.2 days (range 2-6 days). Bowel function returned on an average of 3.5 days (range 2-5 days). Three patients (14%) developed postoperative wound infections. There were no anastomotic leaks and no mortality. At a mean follow-up of 14.7 months, the only long-term complication has been a small hernia at a colostomy site. CONCLUSIONS: Laparoscopic colostomy reversal after Hartmann's procedure can be performed with low morbidity and a short hospital stay. The need for conversion to open surgery is uncommon despite patients' previous surgeries. A laparoscopic approach to colostomy takedown is safe and feasible and may result in a reduction in complications and length of stay as has been seen with other minimally invasive procedures.

Adult↗
PubMed2005

Guide wire entrapment by inferior vena cava filters: an experimental study.

BACKGROUND: In situ vena cava filters are at risk for complications with the use of J-tipped guide wires. The purpose of this study was to evaluate the impact of two commonly used J-tipped guide wires on the stability of the four most recently released vena cava filters in an in vitro flow model. STUDY DESIGN: Four filters (OptEase [F1], Günther Tulip [F2], Vena Tech LP [F3], and Recovery [F4]) were inserted into an in vitro flow model. Two J-tipped guide wires (0.032-inch [GW-1], 0.035-inch [GW-2]) were passed through each filter (n = 50 passes per wire) for a distance of 10 cm. The inserter was blind as to the effects of the wire. The filters were monitored by an independent observer for adverse events occurring between the filters and the guide wires. These were defined as: migrations (>1 cm), change of position (tilt>10 degrees), and entrapment of the wire (unable to remove wire). Descriptive statistics, chi-square, and Fisher's exact test were used (p < 0.05 considered significant). RESULTS: GW-1 resulted in a lower incidence of entrapment, migration, and tilt for all filters compared with GW-2 (F1, p = 0.003; F2, p < 0.0001; F3, p < 0.0001; F4, p = 0.0004). GW-1 resulted in entrapment in 0%, migration in 7.5%, and tilt in 10.5% of insertions. GW-2 resulted in entrapment in 1%, migration in 26.5%, and tilt in 5.5% of insertions. The incidence of adverse events for GW-1 was significantly different compared with all filters (F1, 0%; F2, 46%; F3, 4%; and F4, 22%; p < 0.0001). Similarly, the incidence of adverse events for GW-2 was significantly different when evaluating all filters (F1, 12%; F2, 48%; F3, 22%; F4 60%; p < 0.0001). CONCLUSIONS: The smaller-diameter guide wire resulted in a decreased incidence of adverse events for all filters, but there is still risk for complications. Knowledge of potential complications associated with vena cava filters and the postinsertion use of guide wires are essential to avoid potential mishaps.

Catheterization↗
PubMed2005

Laparoscopic repair of incisional hernias.

Laparoscopic repair of incisional hernia has been shown safe and efficacious, with low rates of conversion to open, short hospital stay, moderate complication rate, and low recurrence. Using the benefits of open retromuscular, sublay repair, the laparoscopic approach provides adequate mesh overlap and allows for identification of the entire abdominal wall fascia at risk for hernia formation. Fixation of the prosthesis to the abdominal wall is best provided by transabdominal to secure the mesh during the initial phase of incorporation. Long-term follow-up data support the durability of laparoscopic repair of ventral hernias with reduced rate of recurrence, low risk of infection, and applicability to difficult patient populations, such as the morbidly obese and those with prior failed attempts.

Abdominal Wall↗
PubMed2005

Clinical outcomes of laparoscopic adrenalectomy for lateralizing nodular hyperplasia.

BACKGROUND: Nodular adrenal hyperplasia (NAH) may mimic the biochemical characteristics of an aldosterone-producing adenoma. The authors evaluated the outcomes of unilateral laparoscopic adrenalectomy in the setting of lateralizing aldosterone hypersecretion by NAH. METHODS: Retrospective review of consecutive patients who underwent a laparoscopic adrenalectomy for primary hyperaldosteronism owing to NAH was performed. Patient demographics, perioperative symptoms, medications, radiographic findings, and serum chemistries were analyzed. Response to operation was classified according to postoperative control of hypertension and hypokalemia as resolved, improved, or refractory. RESULTS: From January 1999 to October 2004, 15 patients underwent a laparoscopic unilateral adrenalectomy for hyperaldosteronism owing to lateralizing NAH. Nine (60%) patients presented with > or =5 years of hypertension, including 8 (53%) patients with labile or malignant hypertension. Ten (67%) patients had hypokalemia. Abdominal imaging results were normal in 9 (60%) patients. All patients underwent adrenal venous sampling (94% successfully), which revealed an average adjusted aldosterone ratio of 17.6 (range, 1.2 to 75.9). At a mean follow-up of 26 (range, 4 to 58) months, hypertension had resolved in 4 (27%), improved in 8 (53%), and was refractory in 3 (20%) patients. Hypokalemia resolved in all patients. There were no complications, conversions, or mortalities. CONCLUSION: This series shows that unilateral adrenalectomy for lateralizing NAH results in eradication of hypokalemia and resolution or significant improvement in hypertension in 80% of patients at long-term follow-up. When lateralization of aldosterone production is noted, laparoscopic adrenalectomy provides significant clinical improvement even in patients with a pathologic diagnosis of NAH.

Adrenal Glands↗
PubMed2005

Gas embolism during laparoscopic cholecystectomy.

Advancements in laparoscopic surgery have resulted in decreased length of hospitalization, reduced postoperative pain, and better cosmesis following general surgical procedures. Carbon dioxide gas embolism is a rare occurrence that can be fatal. We report the case of a patient with a venous gas embolism during laparoscopic cholecystectomy. A 63-year-old woman presented with intermittent right upper quadrant pain, and her abdominal ultrasound showed a possible gallbladder polyp. A laparoscopic cholecystectomy was planned. A Veress needle was placed in the right upper quadrant to initiate abdominal access. Shortly after carbon dioxide insufflation, the patient's hemodynamic status deteriorated, her oxygen saturation dropped, and her end-tidal CO2 decreased. Gas insufflation was immediately stopped, and the patient was resuscitated. She stabilized quickly, and the procedure was performed without further event. She did well postoperatively and was discharged home the next day. Carbon dioxide embolism during laparoscopy, albeit rare, can be a fatal complication of the procedure. Whenever sudden changes in hemodynamic stability occur, venous gas embolism should be considered. As laparoscopic techniques and applications are expanded, the general surgeon must be aware of this entity.

Carbon Dioxide↗
PubMed2005

The argument for lightweight polypropylene mesh in hernia repair.

The development of polypropylene prosthetics revolutionized surgery for the repair of abdominal wall hernias. A tension-free mesh technique has drastically reduced recurrence rates for all hernias compared to tissue repairs and has made it possible to reconstruct large ventral defects that were previously irreparable. The repair of abdominal wall defects is one of the most commonly performed general surgical procedures, with over 1 million polypropylene implants inserted each year. Surprisingly, little research has been performed to investigate the interaction of abdominal wall forces on a ventral hernia repair or the required amount or strength of the foreign-body material necessary for an adequate hernia repair. The long-term consequences of implantable polypropylene prosthetics are not without concern. The body generates an intense inflammatory response to the prosthetic that results in scar plate formation, increased stiffness of the abdominal wall, and shrinkage of the biomaterial. Reducing the density of polypropylene and creating a ''light weight'' mesh theoretically induces less foreign-body response, results in improved abdominal wall compliance, causes less contraction or shrinkage of the mesh, and allows for better tissue incorporation. A review of the laboratory data and short-term clinical follow-up is reviewed to provide a strong basis or argument for the use of ''light weight'' prosthetics in hernia surgery.

Dioxanes↗
PubMed2004

Advanced age is not a prohibitive factor in laparoscopic nephrectomy for renal pathology.

Since the first procedure by Clayman and colleagues in 1990, laparoscopic nephrectomy has been performed at multiple institutions worldwide and is an accepted approach for benign and malignant renal pathology. We retrospectively compared the outcomes of laparoscopic nephrectomy for renal pathology in patients older than and less than 65 years of age. Data were collected for all patients undergoing elective nephrectomy (simple, radical, and nephroureterectomy) for renal pathology between November 2000 and June 2003. A total of 94 laparoscopic nephrectomies (62 hand-assisted, 32 totally laparoscopic) for renal disease were performed. Indications for surgery included renal cell carcinoma (63), transitional cell carcinoma (7), hypertension (9), chronic pyelonephritis (6), nonfunctioning kidney (4), complex cyst (3), and polycystic kidney disease (2). There were 33 elderly patients (> or = 65 years) and 61 adult patients (< 65 years). The elderly group had a mean operative time (238 min vs 234.3 min; P = 0.89) and blood loss (88.5 mL vs 149.8 mL; P = 0.68) similar to the adult group. Likewise, the incidence of perioperative complications was no different between the two groups (intra-op: 3.0% vs 0%; P = 0.35/post-op: 21.2% vs 16.4%; P = 0.56). The length of hospitalization was longer in the elderly population (5.7 days versus 5.0 days; P = 0.01) compared to the younger adult group. Laparoscopic nephrectomy is well tolerated in the elderly population. For all surgical indications, the use of a minimally invasive approach confers operative times, blood loss, and morbidity that are comparable to those of younger patients. Yet, length of stay remains longer for elderly patients undergoing nephrectomy.

Adolescent↗
PubMed2004

Colonoscopic perforations: incidence, management, and outcomes.

Fiberoptic colonoscopy provides superior diagnostic and therapeutic capabilities in the treatment of lower gastrointestinal disease processes. A well-recognized, but uncommon, complication during the procedure is perforation. The purpose of this study was to determine the incidence of colonoscopic perforation, define risk factors, assess the management of these complications, and evaluate outcomes. From January 1997 through December 2003, 43,609 colonoscopies were performed in our medical center. There were 14 (0.032%) perforations (1 in 3115 procedures); 7 from diagnostic and 7 from therapeutic procedures. General surgeons performed 1243 procedures (2.9%), and their rate of perforation was 0.080 per cent compared with 0.031 per cent for gastroenterologists during the same period. Half of the perforations occurred in the rectosigmoid, and the most common mechanism was mechanical (n = 6). Perforation was identified immediately during endoscopy in 50 per cent of the patients. Thirteen of 14 perforations were treated within 24 hours; 1 was delayed 48 hours. Initial surgical management was undertaken in 11/14 patients. Initial nonoperative treatment was attempted in three and was successful in only one patient. The mean length of stay following perforation was 11.2 days (range, 4-36 days). Three patients (21.4%) had 7 postoperative complications. Colonoscopic perforations are uncommon but can be recognized early and managed surgically with acceptable morbidity and postoperative length of stay.

Adult↗
PubMed2003

Differential regulation of somatodendritic and nerve terminal dopamine release by serotonergic innervation of substantia nigra.

Nigrostriatal dopaminergic neurons release dopamine from dendrites in substantia nigra and axon terminals in striatum. The cellular mechanisms for somatodendritic and axonal dopamine release are similar, but somatodendritic and nerve terminal dopamine release may not always occur in parallel. The current studies used in vivo microdialysis to simultaneously measure changes in dendritic and nerve terminal dopamine efflux in substantia nigra and ipsilateral striatum respectively, following intranigral application of various drugs by reverse dialysis through the nigral probe. The serotonin releasers (+/-)-fenfluramine (100 micro m) and (+)-fenfluramine (100 micro m) significantly increased dendritic dopamine efflux without affecting extracellular dopamine in striatum. The non-selective serotonin receptor agonist 1-(m-chlorophenyl)-piperazine (100 micro m) elicited a similar pattern of dopamine release in substantia nigra and striatum. NMDA (33 micro m) produced an increase in nigral dopamine of a similar magnitude to mCPP or either fenfluramine drug. However, NMDA also induced a concurrent increase in striatal dopamine. The D2 agonist quinpirole (100 micro m) had a parallel inhibitory effect on dopamine release from dendritic and terminal sites as well. Taken together, these data suggest that serotonergic afferents to substantia nigra may evoke dendritic dopamine release through a mechanism that is uncoupled from the impulse-dependent control of nerve terminal dopamine release.

Animals↗