Functional Duration of Closure Systems Used in Partial Nephrectomy.

PURPOSE: We determined the functional life of various configurations of partial nephrectomy closure systems. MATERIALS AND METHODS: Sutures were prepared using standard techniques for sutured renorrhaphy during partial nephrectomy. Tested systems included knot/Hem-o-Lok®, Lapra-Ty®/Hem-o-Lok and Hem-o-Lok/Hem-o-Lok combinations. The saline filled tank was maintained at 37C. Vicryl®, Stratafix™ polyglycolic acid-polycaprolactone or V-Loc™ 180 sutures were suspended at 4 or 2 N. Suture material breakage or slippage was considered failure. RESULTS: At 4 N 20% of sutures terminated with knot/Hem-o-Lok failed by 3 weeks compared to 56% and 100% terminated with Lapra-Ty/Hem-o-Lok and Hem-o-Lok/Hem-o-Lok, respectively (p <0.0001). The 55% and 100% of failures with Lapra-Ty/Hem-o-Lok and Hem-o-Lok/Hem-o-Lok, respectively, were generally due to slippage vs 11% with knot/Hem-o-Lok (p <0.0001). Overall failure rates with Lapra-Ty/Hem-o-Lok for zero to 4-zero sutures were 41% with Vicryl, 82% with polyglycolic acid-polycaprolactone and 24% with V-Loc 180 (p <0.0001). The only sutures without failure at 4 N with Lapra-Ty/Hem-o-Lok and knot/Hem-o-Lok closure systems were Vicryl zero, and V-Loc 2-zero and 3-zero. At 2 N Lapra-Ty/Hem-o-Lok failure (17.5% vs 0%, p = 0.039) and Hem-o-Lok/Hem-o-Lok failure (39% vs 16%, p = 0.074) were more common with polyglycolic acid-polycaprolactone than with V-Loc sutures. CONCLUSION: Hem-o-Lok/Hem-o-Lok and Lapra-Ty/Hem-o-Lok combinations resulted in more frequent failures at 3 weeks or greater than knot/Hem-o-Lok. For all sutures tested knots were superior to Lapra-Tys to backstop Hem-o-Loks at 4 N. Preferably, Vicryl zero or V-Loc 2-zero/3-zero sutures should be used in combination with knots or Lapra-Tys at 4 N. Under these experimental conditions the Lapra-Ty/Hem-o-Lok combination did not reliably suspend the other sutures tested for 3 weeks. If Lapra-Ty/Hem-o-Lok or Hem-o-Lok/Hem-o-Lok combinations are used, we recommend closure at lesser tension and/or the use of appropriate sutures.

Holding Strength of a Hem-o-lok/Lapra-Ty Clip Combination on Sutures Used During Partial Nephrectomy.

OBJECTIVE: To investigate the anti-slip strength of closing systems employing sutures terminated with a Hem-o-lok/Lapra-Ty clip combination to determine which sutures perform best for this application. Partial nephrectomy is the reference standard for treatment of small renal masses. The main disadvantage of partial nephrectomy is the risk of technical complications, including renorrhaphy site bleeding and urine leak. MATERIALS AND METHODS: A materials testing system produced a constant velocity pull on the free end of an anchored suture. A Lapra-Ty clip was attached 1 cm from the end of each suture as a backstop for the Hem-o-lok. A digital force gauge measured the tension that was applied until the suture slipped in the closing system. Vicryl, Monocryl, Chromic, Stratafix, and V-Loc sutures of diameters 1 to 4-0 were tested (n = 7 for each suture type, 161 total experiments). RESULTS: The holding strength of a Lapra-Ty/Hem-o-lok clip combination is lowest for Vicryl 4-0 (4.3 ± 1.4N) and highest for Monocryl 0 (16.5 ± 1.6N) sutures. Larger sutures (1 and 0) hold at higher tensions than sutures with smaller dimensions (4-0 and 3-0). For 2-0 sutures, the holding strength was 5.7N with Vicryl, 13.8N with Stratafix, and 15.9N with V-Loc sutures. CONCLUSION: The mean values of holding tension of this anchoring system for all sutures tested was greater than the amount found to be sufficient for tissue closure in previous studies (3.2N). Barbed sutures (Stratafix, V-Loc) appeared to have superior holding strength when compared with most standard sutures; barb orientation does not influence holding tension.

Low-cost EEG-based sleep detection.

A real-time stage 1 sleep detection system using a low-cost single dry-sensor EEG headset is described. This device issues an auditory warning at the onset of stage 1 sleep using the "NeuroSky Mindset," an inexpensive commercial entertainment-based headset. The EEG signal is filtered into low/high alpha and low/high beta frequency bands which are analyzed to indicate the onset of sleep. Preliminary results indicate an 81% effective rate of detecting sleep with all failures being false positives of sleep onset. This device was able to predict and respond to the onset of drowsiness preceding stage 1 sleep allowing for earlier warnings with the result of fewer sleep-related accidents.

Investigation of forces involved in closure of the renal remnant after simulated partial nephrectomy.

OBJECTIVE: To investigate the potential biomechanical causes of the complications of partial nephrectomy (PN) in a preclinical model of sliding-clip renorrhaphy. PN is a reference standard for amenable small renal masses. One disadvantage of PN, however, is the risk of postoperative bleeding and/or urinary leak. MATERIALS AND METHODS: Simulated tumor excision and reconstruction using sliding-clip renorrhaphy were performed on fresh porcine kidneys. Suture tension (newtons, N) was measured in nonperfused and perfused states. RESULTS: Mean suture tension initially applied during renorrhaphy was 2.8 ± 0.7 N. After simulated perfusion to 120 mm Hg, increased tension was necessary to control fluid extravasation (average, 3.2 ± 0.7 N). For intravascular pressures above 200 mm Hg, an average tension of 3.4 ± 0.7 N was necessary to prevent observable leakage. The increase in suture tension under normal and hypertensive states averaged 21 ± 28% and 29 ± 31%, respectively. In experiments examining maximum suture tension before suture tear through, failure of the anchored sutures varied with the width of incorporated renal capsule. Mean forces were 5.7 ± 3.2, 8.8 ± 5.7, and 14.0 ± 6.0 N with 0.5, 1.0, and 1.5 cm of capsule, respectively. Review of video footage indicated that acute angles appear to contribute to suture failure. CONCLUSION: This study demonstrates that the tension required to cause suture failure is only slightly higher than the tension typically applied during PN and necessary to control bleeding and urine leaks. After reperfusion of the kidney, the tension can increase by ≥ 29% under hypertensive conditions. Incorporation of sufficient (≥ 0.5 cm) capsule and avoidance of acute angles of entry or exit during closure of the kidney are likely to reduce suture failure.