Biomedical subjects

John Hoopman

Publications and source records attributed to John Hoopman.

6 recordsLinked to original sources

PubMed2004

A useful algorithm for determining fluence and pulse width for vascular targets using 1,064 nm Nd:YAG laser in an animal model.

BACKGROUND AND OBJECTIVES: Many current parameters to ablate vascular beds using 1,064 nm lasers are based on high-energy settings and often fail to consider vessel diameter and/or pulse width. This study attempts to define the minimal effective dosage (MED) of energy and pulse width for specific vessel diameters in an animal model. STUDY DESIGN/MATERIALS AND METHODS: 1,064 nm Nd: YAG was used in 15 Sprague-Dawley rats. Bilateral extended dorsolateral skin flaps were elevated and vessel diameters from 0.1 to 1 mm were identified. Pulse widths (PW) in a range of 15-60 milliseconds and fluences between 70-110 J/cm2 with contact cooling at 5 degrees C (Celsius) were utilized. Results were determined clinically and histologically. RESULTS: Ideal pulse width and MED for each vessel diameter were determined using a 6 mm spot size. Histology showed early hemostasis and subsequent thrombosis, which are consistent with clinical findings. CONCLUSIONS: This model allows in vivo monitoring of vessel ablation. Optimal pulse width and MED levels versus vessel diameter determined in this animal model provide a useful algorithm that may allow for more effective treatment of vascular targets utilizing the 1,064 nm Nd:YAG laser.

Algorithms↗

PubMed2004

Effect of low-level laser therapy on abdominal adipocytes before lipoplasty procedures.

Low-level laser therapy is a new subspecialty for the medical application of lasers that provides therapeutic rather than surgical outcomes for many medical indications. Recently, low-level laser therapy was reported to "liquefy" or release stored fat in adipocytes by the opening of specialized yet not identified cell membrane-associated pores after a brief treatment. Currently, low-level laser therapy is a U.S. Food and Drug Administration-approved technology for improving pain alleviation. To explore these data further, a series of in vitro studies on human preadipocytes and institutional animal care and use committee-approved protocols in a porcine Yucatan model and an institutional review board-approved clinical study were performed. Using a 635-nm low-level laser of 1.0 J/cm supplied to the authors by the vendor, these studies were designed to determine whether alteration in adipocyte structure or function was modulated after low-level laser therapy. Cultured human preadipocytes after 60 minutes of laser therapy did not change appearance compared with nonirradiated control cells. In the porcine model, low-level laser therapy (30 minutes) was compared with traditional lipoplasty (suction-assisted lipoplasty) and ultrasound-assisted lipoplasty. From histologic and scanning electron microscopic evaluations of the lipoaspirates, no differences were observed between low-level laser therapy-derived and suction-assisted lipoplasty-derived specimens. Using exposure times of 0, 15, 30, and 60 minutes in the presence or absence of superwet wetting solution and in the absence of lipoplasty, total energy values of 0.9 mW were delivered to tissue samples at three increasing depths from each experimental site. No histologic tissue changes or specifically in adipocyte structure were observed at any depth with the longest low-level laser therapy (60 minutes with superwet fluid). Three subjects undergoing large-volume lipoplasty were exposed to superwet wetting fluid infiltration 14 minutes before and 12 minutes after, according to vendor instructions. Tissue samples from infiltrated areas were collected before suction-assisted lipoplasty and lipoaspirates from suction-assisted lipoplasty. No consistent observations of adipocyte disruptions were observed in the histologic or scanning electron microscopy photographs. These data do not support the belief that low-level laser therapy treatment before lipoplasty procedures disrupts tissue adipocyte structure.

Abdomen↗

PubMed2003

Sutureless laparoscopic heminephrectomy using laser tissue soldering.

BACKGROUND AND PURPOSE: Widespread application of laparoscopic partial nephrectomy has been limited by the lack of a reliable means of attaining hemostasis. We describe laser tissue welding using human albumin as a solder to control bleeding and seal the collecting system during laparoscopic heminephrectomy in a porcine model. MATERIALS AND METHODS: Laparoscopic left lower-pole heminephrectomy was performed in five female domestic pigs after occluding the hilar vessels. Using an 810-nm pulsed diode laser (20 W), a 50% liquid albumin-indocyanine green solder was welded to the cut edge of the renal parenchyma to seal the collecting system and achieve hemostasis. Two weeks later, an identical procedure was performed on the right kidney, after which, the animals were sacrificed and both kidneys were harvested for ex vivo retrograde pyelograms and histopathologic analysis. RESULTS: All 10 heminephrectomies were performed without complication. The mean operative time was 82 minutes, with an average blood loss of 43.5 mL per procedure. The mean warm ischemia time was 11.7 minutes. For each heminephrectomy, a mean of 4.2 mL of solder was welded to the cut parenchymal surface. In three of the five acute kidneys and all five 2-week kidneys, ex vivo retrograde pyelograms demonstrated no extravasation. In addition, no animal had clinical evidence of urinoma or delayed hemorrhage. Histopathologic analysis showed preservation of the renal parenchyma immediately beneath the solder. DISCUSSION: Laser tissue welding provided reliable hemostasis and closure of the collecting system while protecting the underlying parenchyma from the deleterious effect of the laser during porcine laparoscopic heminephrectomy.

Albumins↗

PubMed2002

Laparoscopic interstitial laser coagulation of renal tissue with and without hilar occlusion in the porcine model.

PURPOSE: To evaluate the safety and efficacy of interstitial laser coagulation (ILC), applied via a laparoscopic approach, with and without hilar occlusion in the porcine model. MATERIALS AND METHODS: In nine female farm pigs, bilateral renal mobilization was performed via a transperitoneal laparoscopic approach. Using a 600- micro m bare-tip silicon diode laser fiber inserted 0.5 cm into the lower pole of each kidney, diode laser energy (wavelength 805 nm) was applied for 15 minutes at 6 W. In each pig, the left renal hilum was clamped during ILC. Animals were sacrificed immediately (N = 3) or at 2 weeks (N = 3) or 4 weeks (N = 3). The kidneys were inspected grossly, and the lesions were evaluated microscopically. Nicotinamide adenine dinucleotide (NADH) histochemical staining was performed to assess viability. RESULTS: Grossly, parenchymal lesions appeared firm and white with a central zone of carbonization, cavitation, or both. Histopathology examination revealed cellular inflammation in acute lesions; chronic lesions demonstrated coagulative necrosis with progressive fibrosis. The NADH staining showed residual viable cells within the treatment zone of survival animals but not in acute animals. The mean size of the treatment zone in kidneys with unoccluded blood flow was 2.4 x 2.1 x 2.0 cm, 4.0 x 3.3 x 2.8 cm, and 3.3 x 3.5 x 2.0 cm in the acute, 2-week, and 4-week group, respectively. Hilar occlusion resulted in a slightly, but statistically insignificantly, larger lesion. In the 2-week survival group, one animal had a left subcapsular hematoma on the hilar-occluded side. In another 2-week animal, extension of the ILC zone was noted beyond the kidney into the psoas muscle. In the 4-week survival group, two animals developed gross hematuria; one had a left perinephric urinoma and urine leak noted at necropsy. CONCLUSIONS: Renal ILC may represent an alternative minimally invasive technique for ablation of renal tumors. However, histologic evidence of viable cells within the treatment zone mandates refinement of the technique in the animal model before further application in humans. Hilar occlusion does not appear to enhance tissue ablation.

Animals↗

PubMed2002

Laparoscopic partial nephrectomy with a diode laser: porcine results.

PURPOSE: To develop a safe and effective technique for laparoscopic partial nephrectomy without need for hilar occlusion. MATERIALS AND METHODS: Laparoscopic transperitoneal lower-pole partial nephrectomy was performed in five 45- to 50-kg female farm pigs using a 980-nm diode laser. Standard transperitoneal access was obtained, and a four-port approach was used to perform a laparoscopic right partial nephrectomy using a diode laser (23 W) without hilar occlusion. The pigs were allowed to recover and 2 weeks later underwent a left laparoscopic partial nephrectomy. Postoperatively, renal function was monitored by serial serum creatinine measurements. Both kidneys and ureters were removed for ex-vivo retrograde pyelograms and histologic analysis. RESULTS: The 980-nm diode laser resulted in successful lower-pole partial nephrectomy without hilar occlusion in all 10 of the kidneys. In three cases, laser hemostasis was insufficient, and adjunctive hemostatic clips were necessary to stop bleeding. The mean operative time was 126 minutes, and the mean laser time was 84 minutes. An average of 23% (range 13%-33%) of the kidney parenchyma was resected. The mean blood loss was 150 mL (range 50-300 mL). There was no evidence of urinary extravasation on ex-vivo retrograde pyelograms at 2 weeks in any of the kidneys. CONCLUSION: Laparoscopic partial nephrectomy without hilar occlusion using the 980-nm diode laser is feasible in the porcine model. Because adjunctive hemostatic measures may be necessary in some cases, clinical trials in humans should be limited to small exophytic tumors.

Animals↗

PubMedDate not supplied

Laparoscopic partial nephrectomy using holmium laser in a porcine model.

OBJECTIVE: To evaluate the utility of the holmium laser for partial nephrectomy in a porcine model. METHODS: Transperitoneal lower pole laparoscopic partial nephrectomy was performed in 5 farm pigs. All animals underwent a left-sided laparoscopic partial nephrectomy and were kept alive for 2 weeks (survival group). Subsequently, a right laparoscopic partial nephrectomy was performed (acute group), and the animals were sacrificed. A 1000-microm (n=6) or 550-microm (n=4) end-fire holmium laser fiber set at 0.2 joules and 60 pulses per second was used to transect the lower pole of the kidney 1 cm below the level of the hilum. The cut parenchymal surface was then sealed with fibrin glue in the survival animals. The operated on kidneys were inspected grossly and evaluated microscopically. RESULTS: Laser transection was successfully completed in all cases, and hemostasis proved adequate without any adjunctive measures. No perioperative complications occurred. Estimated blood loss was less than 50 cc for each laparoscopic partial nephrectomy. The acute and survival pigs showed no statistically significant differences in specimen size or weight. Serum creatinine levels were normal in all survival animals. Extravasation was noted on retrograde pyelograms of 2 animals in the survival group. CONCLUSIONS: The Holmium:YAG laser provides an efficacious modality for transecting the kidney in a porcine model. Clinical trials are necessary to determine its role in laparoscopic partial nephrectomy in humans.

Animals↗