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Biomedical subjects

P Rhee

Publications and source records attributed to P Rhee.

32 records · Page 2Linked to original sources
PubMed1999

Telepresence surgery system enhances medical student surgery training.

The telepresence surgery system (TeSS) permits the surgeon to operate on a patient across distances. This is achieved through real-time 3D video vision, stereo audio, and remote instrument control with haptic feedback. Telepresence surgery has been proposed to be useful in providing specialist operative consultation to remote areas. Remotely mentoring medical students with no surgical experience through complex procedures provides an even greater challenge. Third-year medical students with no prior operative experience were mentored exclusively through use of TeSS during a standard surgical skills lab. This two-day laboratory includes abdominal procedures and thoracic procedures. The medical students were alone in the operating room and the teaching surgeon was in an entirely separate room. Anatomy, surgical principles, and adjunct techniques were taught to the students. The students felt the experience was better than standard because of the enhanced learning secondary to the required verbal accuracy in describing the procedures. In addition, they felt they had better visibility since the instructor was not standing in the way. The telepresence surgery system can be successfully used to remotely mentor and enhance introductory surgical training for inexperienced medical students.

Animals↗
PubMed1998

Open pelvic fracture and fecal diversion.

BACKGROUND: Mandatory fecal diversion has been advocated as an appropriate measure to prevent infection in the clinical setting of an open pelvic fracture. However, the efficacy of this practice has not been verified by prospective investigation and has received only inconsistent support from retrospective analyses. OBJECTIVE: To determine whether fecal diversion is associated with a substantially lower incidence of abdominopelvic infectious complications in patients with open pelvic fractures. DESIGN: Case-control study. SETTING: University-based tertiary care, level I trauma center. METHODS: The current study reviews our experience with 60 cases admitted from 1987 to 1993 to Harborview Medical Center, a regional level I trauma center. Data collected on each patient included age, sex, Injury Severity Score, Glasgow Coma Scale, initial heart rate and systolic blood pressure, location and severity of wound, fracture pattern, pelvic stability, time to open reduction internal fixation or external fixation, mortality, use of fecal diversion, and incidence and location of infection. Review of the literature produced an additional 186 patients amenable to analysis. RESULTS: Fecal diversion was performed in 19 patients, 5 (26%) of whom experienced subsequent abdominopelvic infectious morbidity. Of the remaining 41 patients, 7 patients (17%) experienced infectious complications. The 2 groups (diversion vs no diversion) were comparable with regard to relevant demographic and clinical characteristics of injury severity. Combining the present series with those reported by others gave a composite series of 246 patients. For the composite series, diversion was performed in 70% of patients. Infection developed in 27% of patients who underwent diversion vs 29% in patients who did not. In the present series, only mechanical instability was determined by stepwise logistic regression to be significantly associated with pelvic infection. This association was not altered by diversion status. CONCLUSIONS: Diversion of the fecal stream to protect open pelvic fractures is not associated with a lower incidence of abdominopelvic infectious complications. Diversion may offer protection to a select group of patients with extensive soft tissue injury or posterior wounds. Mechanical instability was independently associated with infection.

Abdominal Abscess↗
PubMed1998

Rapid arterial anastomosis with titanium clips.

BACKGROUND: The obvious advantages of rapid arterial anastomoses have prompted the continuing search for more rapid anastomotic techniques to complement the standard sutured anastomosis. Nonpenetrating, arcuate-legged titanium vascular closure staple (VCS) clips were initially developed for microvascular anastomoses. The purpose of this study was to compare VCS clips with sutured arterial end-to-end anastomosis in larger vessels. METHODS: In 6 pigs, transacted iliac arteries were reanastomosed with VCS clips on one side and continuous 6-0 polypropylene suture on the other. RESULTS: The reconstruction time was 8.4+/-5.2 minutes for clip closure and 12.0+/-6.6 minutes for suture closure (P = 0.033). All vessels were patent half an hour after completing the anastomoses with no signs of early thrombosis. CONCLUSIONS: Arterial end-to-end anastomosis can be performed more rapidly with VCS clips than continuous sutures, and are potentially useful in situations where the clamp time of the vessel is critical.

Anastomosis, Surgical↗
PubMed1998

Arterial reconstruction with vascular clips is safe and quicker than sutured repair.

BACKGROUND: Non-penetrating, arcuate-legged vascular-closure staple clips made of titanium were initially developed for microvascular anastomoses with little experience of their use in larger vessels. The purpose of this study was to compare vascular-closure staple clips to sutured anastomoses in common iliac arteries in a porcine model. METHODS: In an experimental study, transected iliac arteries on both sides of 11 pigs were randomly assigned to end-to-end anastomosis performed with vascular-closure staple clips or interrupted 6-0 polypropylene sutures. Angiographic, macroscopic and microscopic results were assessed after 2 months. RESULTS: There was no significant difference in the patency rate, tensile strength of the anastomoses, vessel diameter at the repair site, intimal thickness or wall thickness of the arteries after either method of closure. The mean (s.d.) clamp time was 19.8 (6.1) minutes for clip repair, and 36.0 (6.9) seconds for suture repair (P < 0.001). The times required for the reconstruction of the anastomoses were 17.4 (6.1) and 35.5 (7.1) minutes, respectively (P < 0.001). CONCLUSIONS: Arterial anastomoses performed with vascular-closure staple clips are faster than sutured anastomoses, and result in comparable wound healing when assessed for patency, tensile strength, degree of narrowing and intimal reaction.

Anastomosis, Surgical↗
PubMed1998

Lactated Ringer's solution resuscitation causes neutrophil activation after hemorrhagic shock.

PURPOSE: To determine the degree of neutrophil activation caused by hemorrhagic shock and resuscitation. METHODS: Awake swine underwent 15-minute 40% blood volume hemorrhage, and a 1-hour shock period, followed by resuscitation with: group I, lactated Ringer's solution (LR); group II, shed blood; and group III, 7.5% hypertonic saline (HTS). Group IV underwent sham hemorrhage and LR infusion. Neutrophil activation was measured in whole blood using flow cytometry to detect intracellular superoxide burst activity. RESULTS: Neutrophil activation increased significantly immediately after hemorrhage, but it was greatest after resuscitation with LR (group I, 273 vs. 102%; p < 0.05). Animals that received shed blood (group II) and HTS (group III) had neutrophil activity return to baseline state after resuscitation. Group IV animals had an increase in neutrophil activation (259 vs. 129%; p < 0.05). CONCLUSION: Neutrophil activation occurring after LR resuscitation and LR infusion without hemorrhage, but not after resuscitation with shed blood or HTS, suggests that the neutrophil activation may be caused by LR and not by reperfusion.

Animals↗
PubMed1997

Near-infrared spectroscopy: continuous measurement of cytochrome oxidation during hemorrhagic shock.

OBJECTIVE: Mitochondrial cytochrome a,a3 redox shifts can be determined by near-infrared wavelength reflection. Since near-infrared wavelengths penetrate skin and bone, a potential exists to noninvasively measure mitochondrial oxidation using this phenomenon. The purpose of this study was to compare conventional parameters of resuscitation with regional measurements of spectroscopically derived cytochrome redox state in a hemorrhagic shock model. DESIGN: Prospective, controlled laboratory investigation. SETTING: Animal research laboratory of a university medical center. SUBJECTS: New Zealand white rabbits (n = 23), weighing 2 to 3 kg. INTERVENTIONS: After anesthesia and instrumentation, the subjects underwent laparotomy with placement of near-infrared spectroscopy probes on the stomach, liver, kidney, and hamstring muscle. Baseline measurements were obtained, and phlebotomy was used to reduce cardiac output by 60% for 30 mins. Animals were resuscitated with shed autologous blood and crystalloid to reach baseline cardiac output (0.9%), and were monitored for an additional 60 mins. MEASUREMENTS AND MAIN RESULTS: Significant correlations between mitochondrial cytochrome a,a3 redox state, cardiac output, and oxygen delivery were observed throughout shock and resuscitation. However, gastric cytochrome oxidation did not recover after shock, despite systemic evidence of adequate resuscitation (p < .05). CONCLUSIONS: Resuscitation from severe hemorrhagic shock may not uniformly restore cellular oxygenation, despite normalization of traditional parameters of resuscitation. Direct monitoring of cytochrome oxidation may be useful in identifying regional areas of dysoxia.

Animals↗
PubMed1996

Limiting computed tomography to patients with peritoneal lavage-positive results reduces cost and unnecessary celiotomies in blunt trauma.

OBJECTIVE: To determine if computed tomographic (CT) scanning can be used to identify patients with blunt trauma, positive results of diagnostic peritoneal lavage (DPL), and a stable hemodynamic status who could be managed safely and cost-effectively without celiotomy. DESIGN: Patients with blunt trauma who required an abdominal evaluation underwent DPL. Patients with a red blood cell count greater than 10(11)/L (10(5)/mm3) on lavage then underwent CT. Patients with solid organ injury alone, as detected on CT scan, were observed; those with evidence of hollow viscus injury underwent celiotomy. RESULTS: Sixty-seven hemodynamically stable patients had a red blood cell count greater than 10(11)/L on DPL; 38 patients underwent subsequent CT scanning, and 29 underwent immediate celiotomy in violation of the protocol. Eleven patients in the protocol group ultimately underwent celiotomy. Overall, there were significantly fewer nontherapeutic celiotomies performed in the protocol group (2/38 vs 9/29, P < .01). There were no deaths in either group. Because DPL is less expensive than CT, limiting CT to patients with DPL-positive results and hemodynamic stability reduced the charges associated with abdominal evaluation by $580,594 over a period of 2 years. CONCLUSION: Limiting CT to the evaluation of patients with DPL-positive results and hemodynamic stability is safe, reduces charges, and results in a lower rate of nontherapeutic celiotomies compared with DPL alone.

Abdominal Injuries↗
PubMed1995

Factors influencing outcome in stab wounds of the heart.

BACKGROUND: The purpose of this study was to identify factors associated with unfavorable outcome following stab wounds to the heart in order to improve selection of patients who may benefit from aggressive resuscitative efforts. METHODS: Preoperative and operative variables were reviewed for all patients treated for cardiac stab wounds at a level I trauma center from 1987 to 1993 in an attempt to identify factors influencing survival. RESULTS: Twenty-nine (53%) of the 55 patients who were resuscitated following stab wounds to the heart during the study period survived. Although profound hypotension (systolic blood pressure < 40 mm Hg), cardiopulmonary resuscitation, and emergency room thoracotomies were associated with poor outcome, none were uniformly predictive of death. Some patients survived with each of these characteristics. CONCLUSIONS: We recommend that all patients suspected of having cardiac stab wounds be fully resuscitated and undergo thoracotomy, as significant survival can be achieved and death is not always the outcome.

Adult↗
PubMed1993

Tumor necrosis factor and monocytes are released during hemorrhagic shock.

Tumor necrosis factor (TNF) is a key mediator involved in many physiologic processes including immunity, inflammation, and metabolism. A relationship between TNF and hemorrhagic shock has not been clearly demonstrated. To help understand the role of TNF in hemorrhagic shock we developed a hemorrhagic shock model to measure TNF and monocyte levels during hemorrhage and resuscitation. Male Sprague-Dawley rats were anesthetized and subjected to a 50% blood loss (30 ml/kg) over 2 min and left in shock for 58 min. The animals were then resuscitated with two times blood loss (60 ml/kg) using lactated Ringers over 1 h. This model results in 75% mortality within 3 days (LD 75). Blood samples (2 ml) were obtained at intervals during shock and resuscitation, and assayed for TNF concentrations and white blood cell counts. Despite a marked fall in total leukocytes (24,600 pre-hemorrhage to 11,300 post-hemorrhage, P < 0.005), monocytes increased in percentage and in total count. Blood levels of TNF were initially undetectable but rose within 10 min after hemorrhage, peaked at 30 min after hemorrhage, and then became undetectable during resuscitation. In this model, macrophages and TNF are released into the circulation after hemorrhagic shock. TNF may play a role as a mediator in the pathophysiology of hemorrhagic shock.

Animals↗
PubMed1993

Portal hypertension.

The treatment of portal hypertensive gastrointestinal hemorrhage has seen many new and innovative advances in the past 15 years, including pharmocotherapy, sclerotherapy, transjugular intrahepatic portacaval shunt, partial portacaval shunt, and hepatic transplantation. Such an array of therapeutic options provides great flexibility for the physicians managing this complex disorder. The less invasive procedures tend to be associated with higher rates of rebleeding from esophageal varices. However, these procedures serve as excellent bridges to hepatic transplantation in poor-risk patients. Surgical portasystemic shunts offer a permanent solution to portal hypertensive bleeding but also have several drawbacks. Standard (end-to-side or side-to-side) portacaval shunts are associated with unacceptably high rates of p4rtasystemic encephalopathy because of complete diversion of portal flow away from the liver. Selective shunts, such as the distal splenorenal shunt, result in maintenance of portal perfusion, but this is not lasting in alcoholic cirrhotics. Partial shunting (small-diameter portacaval H-graft with collateral ligation) is the most recent addition to the surgical armamentarium. This allows for hepatic portal perfusion, thus minimizing encephalopathy rates, but it violates the right upper quadrant if the patient is a candidate for hepatic transplantation. This large array of treatment options, each with its own advantages and disadvantages, permits for careful selection of the best modality based on several influencing factors. These include the underlying liver disease, the prognosis, the health team's experience, the resources available to the patient and the community, and the cost-effectiveness of each treatment.

Esophageal and Gastric Varices↗
PubMed1991

Superoxide dismutase polyethylene glycol improves survival in hemorrhagic shock.

Oxygen free radicals are known to form after reperfusion of ischemic tissue. To test the role and importance of oxygen free radicals in hemorrhagic shock, an animal model of hemorrhagic shock and resuscitation was utilized. Sprague-Dawley rats were anesthetized with halothane and then subjected to approximately 50 per cent blood volume hemorrhage (30 cc/kg), followed by a 60 min shock period. Resuscitation was performed over 1 hour with lactated ringers (LR) at a volume of two times blood loss (60 cc/kg). This model results in a survival rate of 25 per cent over 72 hrs. Using this model, animals were randomized to receive either LR, Superoxide Dismutase-Polyethylene Glycol (SOD-PEG) (15,000 units/kg) with LR or Catalase-Polyethylene Glycol (CAT-PEG) (175,000 units/kg) with LR. The group treated with SOD-PEG demonstrated significantly increased survival rates vs the group treated with LR (67% vs 25%, P = 0.02). The group treated with CAT-PEG demonstrated no significant improvement in survival when compared to the LR-treated group (20% vs 24%). These data suggest that treatment directed toward oxygen free radicals and reperfusion injury may play an important role in hemorrhagic shock resuscitation.

Animals↗
PubMedDate not supplied

Design of preservation solutions for universal tissue preservation in vivo: demonstration of efficacy in preclinical models of profound hypothermic cardiac arrest.

The design of new solutions for the universal preservation of tissues is a quest that would facilitate multiple-organ harvesting from organ donors since current preservation solutions do not provide optimum preservation for all organs. In contrast, a new approach to bloodless surgery using hypothermic blood substitution (HBS) to protect the whole body during profound hypothermic circulatory arrest (clinical suspended animation) has focused on the development of a hybrid solution design with the objective of providing universal tissue preservation. In this study, a porcine model of uncontrolled lethal hemorrhage was employed. A combination of two new solutions, maintenance and purge, was used in a cardiopulmonary bypass (CPB) technique to affect profound hypothermia and prolonged cardiac arrest (60 min), with resuscitation after surgical repair of the vascular deficit induced to affect exsanguination. After rewarming and recovery, pigs were monitored for 6 weeks for neurological deficits, cognitive function (learning new skills), and organ dysfunction. All the normothermic control animals died (n = 10), whereas 90% (9 of 10) in the HBS group survived (P < .05). Moreover, all of the survivors were neurologically intact, displayed normal learning and memory capability, and had no long-term organ dysfunction. Histology of brains after 6 weeks revealed no ischemic damage in marked contrast to control animals, which all showed diffuse ischemic damage. The demonstrated efficacy of these synthetic, acellular HBS solutions for protection of all the tissues in the body during clinical suspended animation justifies their consideration for multiple-organ harvesting from cadaveric and living donors.

Animals↗
PubMedDate not supplied

The pathophysiology of tension pneumothorax in ventilated swine.

It remains unclear as to whether the cardiovascular collapse observed in tension pneumothorax (TP) is strictly a mechanical pressure-related phenomenon or secondary to hypoxemia. This study describes the pathophysiologic changes associated with a surgically induced progressive TP in a ventilated swine model. With a balloon occlusion catheter surgically placed into the pleural space, progressive volumes of pneumothorax were created in six anesthetized pigs on positive-pressure ventilation. Air was introduced into the right hemithorax in 100-mL increments every 4-5 min, with measurements of heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), mean intrapleural pressure (MIP), oxygen saturation (O2%), arterial blood gas (ABG), and cardiac output (C.O.). With the induced progressive TP, results showed that O2% measures decreased immediately and continued to decline throughout the experiment to levels below 50% prior to cardiovascular collapse. The MAP and HR remained relatively stable until approximately 57% total lung capacity progressive TP (600 mL) was reached. At this point, a significant decline in MAP and increase in HR was noted, indicating tension physiology. The C.O. showed a small but significant decrease after 200 mL of air was injected, with a progressive decline after this point. At > 97% total lung capacity TP, lethal cardiovascular collapse occurred in all animals and was associated with an abrupt drop in C.O., HR, and MAP. There was a concurrent equalization of MIP with CVP at the point of collapse. Arterial blood gas measures correlated with O2% trends during the trials. We conclude that the findings of this study support the alternative hypothesis that significant hypoxemia occurs early and precedes hypotension in ventilated animals with TP. Occlusive mechanical compression, suggested by equalization of MIP and CVP, is probably a late event.

Analysis of Variance↗