Peter Lawrence

University of California, Los Angeles, Los Angeles, CA, United States

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Publications (10)19.56 Total impact

  • Jonathan Bath, Peter F Lawrence
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    ABSTRACT: Recent changes to the working practices of physicians in both Europe and the United States have led to concerns regarding a reduced exposure of surgical trainees to operations and thus a potential for a decreased operative experience throughout training. Simulation has been used in many professional fields such as the aeronautical industry to prepare pilots prior to real-life situations and has become recognised as a potentially useful educational tool in surgery. Surgical skills from basic knot-tying to more sophisticated simulation programmes for aortic aneurysm surgery have been introduced in surgical training programmes. Surgical simulation has been demonstrated to have validity in preparing surgeons for operative situations; however, a commitment from educators, protected time and well-orchestrated sessions are key elements in the success of a simulation programme. This article provides 12 tips for the development and implementation of an effective surgical simulation programme informed by experience of large-scale simulation at an academic institution and relevant literature regarding simulation training.
    Medical Teacher 01/2012; 34(3):192-7. · 1.82 Impact Factor
  • Peter F Lawrence
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    ABSTRACT: Conservative, nonresectional management of aortic graft infections is the optimal management for selected patients with aortic graft infections. The best candidates are those patients who have significant comorbidities, or where the existing aortic graft is in a location that precludes excision without causing a high likelihood of morbidity and/or mortality, such as thoracoabdominal and aortic arch grafts. When considering the conservative approach, computed tomographic angiography, supplemented by Indium(111) leukocyte scanning, is the best combination of diagnostic tests. Contraindications to a conservative approach are infected anastomotic aneurysms, graft-enteric fistulas, and suture-line hemorrhage. Needle aspiration of perigraft fluid or phlegmon, under ultrasound or computed tomography guidance, is useful to both culture the infection and provide drainage. A conservative approach should not be considered when the graft infection is due to invasive Gram-negative organisms, such as Pseudomonas or Salmonella species. Once a conservative approach is selected as the best treatment option, drainage of an infected perigraft space is critical to success, and can be performed either percutaneously or with open surgery, whether an endograft or surgically placed graft is in place. If open drainage is required, the perigraft space should be debrided and catheters placed for long-term antibiotic irrigation. With continuous antibiotic irrigation until the cultures are negative, followed by life-long oral antibiotics, there are multiple case reports and small series of long-term survivors. Whether the aortic graft infection is cured or controlled is debated, but outcomes for high-risk patients and those with grafts in critical vascular beds are often superior to a high-risk surgical graft resection.
    Seminars in Vascular Surgery 12/2011; 24(4):199-204. · 1.02 Impact Factor
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    ABSTRACT: Patients with healed venous ulcers often experience recurrence of ulceration, despite the use of long-term compression therapy. This study examines the effect of closing incompetent superficial and/or perforating veins on ulcer recurrence rates in patients with CEAP 5 who have progressive lipodermatosclerosis and impending ulceration. Endovenous ablation was performed on patients with CEAP 5 disease and incompetent superficial and/or perforator veins and increasing lipodermatosclerosis and/or progressive malleolar pain. A minimum of 3 months of compressive therapy was attempted before endovenous ablation of incompetent veins. Demographic data, risk factors, CEAP classification, procedural details, and postoperative status were all recorded. Patients underwent duplex ultrasound scans before ablation to assess for deep, superficial, and perforator venous incompetence as well as postoperatively to confirm successful ablation. Twenty-eight endovenous ablation procedures (superficial = 19; perforator = 9) were performed on 20 patients (limbs = 21). The mean patient age was 73 years old (range, 45-93 years) and the mean body mass index was 29.5 (18.9-58.4). Ninety-five percent of patients previously wore compression stockings (20-30 mm Hg = 9; 30-40 mm Hg = 10; none = 1) for a mean time of 23.3 months (range, 3-52 months) since the prior ulcer healed. Indications for venous ablation were increasing malleolar pain (55%) and/or lipodermatosclerosis (70%). Technical success rates for the ablation procedures were 100% for superficial veins and 89% for perforators (96.4% overall). All patients underwent closure of at least one incompetent vein. Postoperatively, 95% of patients were compliant with wearing compression stockings (20-30 mm Hg = 8; 30-40 mm Hg = 11; none = 1). Ulcer recurrence rates were 0% at 6 months and 4.8% at 12 and 18 months. These data compare with prior studies showing an ulcer recurrence rate up to 67% at 12 months with compression alone. Patients with CEAP 5 healed venous ulcers that undergo endovenous ablation of incompetent superficial and perforating veins and maintain compression have reduced ulcer recurrence rates compared with historical controls that are treated with compression alone.
    Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 11/2011; 55(2):446-50. · 3.52 Impact Factor
  • Jonathan Bath, Peter Lawrence
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    ABSTRACT: Surgical training in the USA and Europe has undergone radical changes with respect to working patterns, culture and limitation on working hours in recent years. Many surgeons who trained prior to the Accreditation Council for Graduate Medical Education (ACGME) duty-hour restrictions have expressed concern that surgeons currently exiting from training may not have had the same operative experience as in the pre-ACGME era. These concerns are particularly relevant in vascular surgery with the prevalence of endovascular therapies reducing the exposure of trainees to more traditional open vascular operations. Simulation has been used in many non-medical fields for technical skill acquisition prior to real-life performance and in recent years has been identified as a useful tool in surgical training. This article highlights the growing need for open vascular simulation as exposure to complex open vascular operations diminishes. The culture of, 'see one, do one, teach one' is fast becoming replaced by 'do many on a simulator, attain competency then perform under supervision in the operating room'. This will only be successfully achieved by the widespread incorporation of open vascular simulation into current vascular training programs if work hours remain limited and endovascular modalities continue to replace traditional open operations.
    Vascular 08/2011; 19(4):175-7. · 0.86 Impact Factor
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    ABSTRACT: Standardizing surgical skills teaching has been proposed as a method to rapidly attain technical competence. This study compared acquisition of vascular skills by standardized vs traditional teaching methods. The study randomized 18 first-year surgical residents to a standardized or traditional group. Participants were taught technical aspects of vascular anastomosis using femoral anastomosis simulation (Limbs & Things, Savannah, Ga), supplemented with factual information. One expert instructor taught a standardized anastomosis technique using the same method each time to one group over four sessions, while, similar to current vascular training, four different expert instructors each taught one session to the other (traditional) group. Knowledge and technical skill were assessed at study completion by an independent vascular expert using Objective Structured Assessment of Technical Skill (OSATS) performance metrics. Participants also provided a written evaluation of the study experience. The standardized group had significantly higher mean overall technical (95.7% vs 75.8%; P = .038) and global skill scores (83.4% vs 67%; P = .006). Tissue handling, efficiency of motion, overall technical skill, and flow of operation were rated significantly higher in the standardized group (mean range, 88%-96% vs 67.6%-77.6%; P < .05). The standardized group trended to better cognitive knowledge (mean, 68.8% vs 60.7%; P = .182), creation of a secure knot at the toe of the anastomosis, fashioning an appropriate arteriotomy, better double-ended suture placement at the heel of the anastomosis (100% vs 62.7%; P = .07), and accurate suture placement (70% vs 25%; P = .153). Seventy-two percent of participant evaluations suggested a preference for a standardized approach. This study demonstrates the feasibility of open vascular simulation to assess the effect of differing teaching methods on performance outcome. Findings from this report suggest that for simulation training, standardized may be more effective than traditional methods of teaching. Transferability of simulator-acquired skills to the clinical setting will be required before open simulation can be unequivocally recommended as a major component of resident technical skill training.
    Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 01/2011; 53(1):229-234, 235.e1-2; discussion 234-5. · 3.52 Impact Factor
  • P F Lawrence, A Chandra
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    ABSTRACT: The treatment paradigm for patients with critical limb ischaemia (CLI) has changed over the past decade with an increase in endovascular interventions. Accompanying this shift has been a fundamental question as to whether open surgery or endovascular therapy represents the optimal treatment for CLI. Review. A review of open versus endovascular surgery was performed. The supporting arguments by respective clinicians of both an 'open first' and an 'endo first' approach are summarised, followed by the available evidence in the literature for each. A summary of an informal survey of endovascular surgeons regarding five indications for an 'open first' approach to CLI are reviewed. Present and future clinical tools and research for providing a more objective decision for intervention in CLI are then summarised. Supporters of either an 'open first' or 'endo first' approach make claims which are not entirely supported by the current level 1 evidence. Five conditions which endovascular surgeons agree that patients with CLI should be treated primarily by open revascularisation include common femoral artery pathology; arterial occlusions caused by extrinsic compression pathologies; extensive foot gangrene/sepsis; young patients and those requiring dependent-free soft tissue reconstructions where durability is paramount; and infrageniculate popliteal and proximal tibial occlusion with single, distal tibial target vessel. Clinical scoring systems and mathematical modelling of lower extremity disease assist in making a prospective intervention decision. The treatment of CLI has changed and continued clinical and research work is focussed on which intervention is more effective. While more attempts at endovascular treatment are made, there remain specific indications for open surgical treatment of CLI. As more work is done towards determining optimal intervention choices on a patient-specific basis, clearer indications for either intervention will emerge.
    European journal of vascular and endovascular surgery: the official journal of the European Society for Vascular Surgery 03/2010; 39 Suppl 1:S32-7. · 2.92 Impact Factor
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    ABSTRACT: Although technological improvements continue to advance the designs of aortic stent grafts, miniaturization of the required delivery systems would allow their application to be available to a wider range of patients and potentially decrease the access difficulties that are encountered. We performed this feasibility study to determine if thin-film NiTi (Nitinol) could be used as a covering for stent grafts ranging from 16 mm to 40 mm in diameter. Specifically, we wished to determine the profile reduction attainable and improve the flexibility of our design. Using a novel hot-sputter deposition technique, we created sheets of thin-film NiTi (TFN) with a tensile strength of >500 Megapascal (MPa) and thickness of 5-10 microns. TFN was used to cover stents, which were then deployed in vitro. Patterned thin film was fabricated via a lift-off technique; grafts were constructed with stents ranging from 16-40 mm and deployed in a pulsatile flow system from the smallest diameter polymer tubing into which the stent and TFN would fit. The bending/stiffness ratio vs similar sized expanded polytetrafluoroethylene (ePTFE)-covered stents was also determined. TFN was created in both non-patterned and patterned forms, with a tensile strength of >100 MPa for the latter. We created devices that were successfully deployed via delivery systems half the size of fabric-covered stent grafts (ie, the 16 mm stent graft that originally was delivered via a 16French (F) system was reduced to 8F, and the 40 mm stent graft delivered via a 24F system was reduced to 12F). No migration of the devices was observed with deployment in both straight and curved tubing, which was sized so that the stent grafts were oversized by 20%. Both forms of the thin-film were noted to be more flexible than the same sized ePTFE stent graft, and the patterned graft had an additional 15-30% flexibility vs the non-patterned film. These in vitro results demonstrate the feasibility of TFN for covering stent grafts designed for placement in the aorta. The delivery profile can be significantly reduced across a wide range of sizes, while the material remained more flexible than ePTFE.
    Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 08/2009; 50(2):375-80. · 3.52 Impact Factor
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    ABSTRACT: Inflammatory abdominal aortic aneurysms (IAAA) can present significant challenges to surgeons, especially in the juxtarenal location where they may not be amenable to endovascular repair. The dense, inflammatory component of these lesions can encase adjacent structures including the duodenum, ureters, and inferior vena cava putting them at risk for injury during open exposure. We report a novel ''reverse hybrid'' technique using a combined endovascular and open approach for repair of large, juxtarenal IAAA's.
    Vascular and Endovascular Surgery 01/2009; 43(5):494-6. · 0.88 Impact Factor
  • Peter F Lawrence
    Perspectives in Vascular Surgery and Endovascular Therapy 12/2008; 20(4):356-7.
  • J C Jimenez, P F Lawrence
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    ABSTRACT: As endovascular procedures increasingly become the procedures of choice for limb salvage, a subset of patients remains that requires open arterial reconstruction due to anatomic or pathologic reasons. Traditional greater saphenous vein harvest performed during open bypass for peripheral occlusive arterial disease is associated with long surgical incisions, increased operative times devoted to wound closure, and wound complications such as infection and dehiscence. Endoscopic conduit harvest, used with excellent results in coronary artery bypass surgery, can also be used in minimally invasive arterial bypass for limb salvage with certain technical modifications. These approaches to complex limb salvage procedures may result in shortened operating room time, shorter length of stay, reduced readmissions for wound complications, and ultimately, decreased costs to the health care system. The treating surgeon must continue to stay up to date with these approaches and be aware of pertinent issues regarding open and minimally invasive arterial interventions, as well as endovascular approaches.
    The Journal of cardiovascular surgery 09/2006; 47(4):415-23. · 1.51 Impact Factor