Incidence and risk factors of incisional hernia formation following abdominal organ transplantation.

BACKGROUND: Hernia formation is common following abdominal operations, and transplant patients are at increased risk due to postoperative immunosuppression. The purpose of this study was to estimate the incidence of incisional hernia formation following primary abdominal solid organ transplantation and identify clinical risk factors for hernia formation. METHODS: We performed a single-institution retrospective review of a prospectively collected database to evaluate all patients who underwent primary liver, kidney, or pancreas transplantation between 2000 and 2011. The primary outcome was hernia formation at the transplant incision. Univariate and multivariate Cox proportional hazards models were used to identify risk factors for incisional hernia formation. RESULTS: A total of 3,460 transplants were performed during the study period: 2,247 kidney only, 718 liver only, and 495 pancreas or simultaneous pancreas and kidney (pancreas group). The overall incisional hernia rate was 7.5 %. The Kaplan-Meier rates of hernia formation at 1, 5, and 10 years were 2.5, 4.9, and 7.0 % for kidney; 4.5, 13.6, and 19.0 % for liver; and 2.5, 12.7, and 21.8 % for the pancreas groups. On univariate analysis, surgical site infection (SSI), body mass index (BMI) >25, delayed graft function, and withholding a calcineurin inhibitor or mycophenolate mofetil (MMF) were associated with hernia formation in the kidney group. SSI and BMI >25 were associated with hernia formation in the liver group. In the pancreas group, SSI, cyclosporine, and withholding MMF were all associated with hernia formation. On multivariate analysis, SSI was strongly associated with hernia formation in all groups. Hazard ratio: kidney = 24.71 (13.00-46.97); liver = 12.0 (6.40-22.52); pancreas = 12.95 (2.78-60.29). CONCLUSION: Incisional hernias are common following abdominal organ transplant with nearly one in five patients developing an incisional hernia 5 years after liver or pancreas transplantation. Strategies focusing on prevention and early treatment of SSI may help to decrease the risk of incisional hernia formation following abdominal organ transplantation.

Infrared thermographic profiles of vessel sealing devices on thyroid parenchyma.

BACKGROUND: During thyroid lobectomy, division of the thyroid parenchyma has traditionally been accomplished using suture ligation. Development of hemostatic techniques in the forms of ultrasonic dissection (UD) and electronic vessel sealing (EVS) have increased the usage of these devices during thyroid operations. We sought to characterize the thermal profile of each of these devices when used to divide the parenchyma of the thyroid gland. METHODS: Using a porcine model, the parenchyma of the gland was sealed by alternating application of the UD and EVS devices. In each case, the thermal activity was recorded using infrared thermal imaging. We performed multiple seals with each instrument and then compared the thermal profiles. RESULTS: There was no significant difference in lateral thermal spread of EVS and UD above 39, 40 or 60°C (2.30 ± 0.31 mm versus 2.53 ± 0.47 mm, P = 0.26; 2.22 ± 0.27 mm versus 2.47 ± 0.47 mm, P = 0.22, and 1.37 ± 0.27 mm versus 1.54 ± 0.26 mm, P = 0.22). There was no significant difference in mean time above 39 or 40°C (35.1 ± 8.7 s versus 31.7 ± 9.3 s, P = 0.47 and 29.9 ± 8.1 s versus 27.3 ± 6.7 s, P = 0.50). UD reached a greater maximum temperature (179.12 ± 0.0008C versus 96.52 ± 5.6C, P ≤ 0.001) and stayed over 60°C for longer than EVS (9.5 ± 1.8 s versus 5.3 ± 0.97 , P ≤ 0.001). CONCLUSIONS: The amount of lateral spread of thermal energy was not significantly different between the UD and EVS devices. However, the use of UD produced a higher maximum temperature during thyroid parenchyma sealing and remained above 60°C longer than EVS. This may translate into greater thermal injury to thyroid and surrounding tissues during division.

Regional differences in cerebral edema after traumatic brain injury identified by impedance analysis.

OBJECTIVE: Cerebral edema is a common and potentially devastating sequel of traumatic brain injury. We developed and validated a system capable of tissue impedance analysis, which was found to correlate with cerebral edema. METHODS: Constant sinusoidal current (50 microA), at frequencies from 500 to 5000 Hz, was applied across a bipolar electrode unit superficially placed in a rat brain after traumatic brain injury. Rats were randomized to three groups: severe controlled cortical injury (CCI), mild CCI, or sham injury. At 60 h post-CCI, cerebral voltage and phase angle were measured at each frequency at the site of injury, at the penumbral region, at the ipsilateral frontal region, and in the contralateral hemisphere. Impedance measurements were also obtained in vivo. The electrical properties of varied injuries and specified locations were compared using a repeated measures analysis of variance (RMANOVA), were correlated with regional tissue water percentage using regression analyses, and were combined to generate polar coordinates. RESULTS: The measured voltage was significantly different at the site of injury (P<0.0001), in the penumbra (P=0.002), and in the contralateral hemisphere (P=0.005) when severe, mild, and sham CCI rats were compared. Severely injured rats had statistically different voltage measurements when the various sites were compared (P=0.002). The ex vivo measurements correlated with in vivo measurements. Further, the impedance measurements correlated with measured tissue water percentage at the site of injury (R2=0.69; P<0.0001). The creation of a polar coordinate graph, incorporating voltage and phase angle measurements, enabled the identification of impedance areas unique to normal, mild edema, and severe edema measurements in the rat brain. CONCLUSIONS: Electrical measurements and tissue water percentages quantified regional and severity differences in rat brain edema after CCI. Impedance was inversely proportional to the tissue water percentage. Thus, impedance measurement can be used to quantify severity of cerebral edema in real time at specific sites.