Anthony A. Meyer

Augmented Reality Visualization for Laparoscopic Surgery

We present the design and a prototype implementation of a three-dimensional visualization system to assist with laparoscopic surgical procedures. The system uses 3D visualization, depth extraction from laparoscopic images, and six degree-of-freedom head and laparoscope tracking to display a merged real and synthetic image in the surgeon’s video-see-through head-mounted display. We also introduce a custom design for this display. A digital light projector, a camera, and a conventional laparoscope create a prototype 3D laparoscope that can extract depth and video imagery.

Effect of inhalation injury, burn size, and age on mortality: a study of 1447 consecutive burn patients

The relative impact of inhalation injury, burn size, and age on overall outcome following burn injury was examined in 1447 consecutive burn patients over a five and a half year period. The overall mortality for all patients was 9.5% (138 of 1447). The presence of inhalation injury, increasing burn size, and advancing age were all associated with an increased mortality (p < 0.01). The incidence of inhalation injury was 19.6% (284 of 1447) and correlated with increasing percent total body surface area (%TBSA) burn (r = 0.41, p < 0.01) and advancing age (r = 0.15, p < 0.01). The overall mortality for patients with inhalation injury was 31% (88 of 284) compared with 4.3% (50 of 1163) for those without inhalation injury. Using multivariate analysis inhalation injury was found to be an important variable in determining outcome, but the most important factor in predicting mortality was %TBSA burn (accuracy = 92.8%) or a combination of %TBSA burn and patient age (accuracy = 93.0%). Adding inhalation injury only slightly improved the ability to predict mortality (accuracy = 93.3%). The presence of inhalation injury is significantly associated with mortality after thermal injury but adds little to the prediction of mortality using %TBSA and age alone.

Renal injury and operative management in the United States: results of a population-based study.

BACKGROUND To evaluate the extent to which nonoperative renal trauma management has been adopted, we determined the incidence of renal injury and the rate of operative management across the United States. METHODS International Classification of Diseases, Ninth Revision diagnosis and procedure codes identified patients with renal injuries in an 18-state administrative database representing 62% of the U.S. population. RESULTS Of 523,870 patients hospitalized for trauma in 1997 or 1998, 6,231 (1.2%) had renal injuries (4.89 per 100,000 population). Sixty-four percent of patients with injuries that were classified had contusions/hematomas, 26.3% had lacerations, 5.3% had parenchymal disruption, and 4% had vascular injuries. Eleven percent of renal trauma patients required surgical management of their kidney injuries, of whom 61%, or 7% of patients with renal injuries overall, underwent nephrectomy. Injury Severity Score, mechanism, and renal injury severity were independent predictors of nephrectomy. CONCLUSION The nephrectomy rate in community and academic centers reflects renal and global injury severity. Prospective trials are indicated to determine whether, in the traumatized patient with severe kidney injury, renal preservation could lead to improved outcomes compared with nephrectomy.

Blood transfusion is an independent predictor of increased mortality in nonoperatively managed blunt hepatic and splenic injuries.

BACKGROUND Management strategies for blunt solid viscus injuries often include blood transfusion. However, transfusion has previously been identified as an independent predictor of mortality in unselected trauma admissions. We hypothesized that transfusion would adversely affect mortality and outcome in patients presenting with blunt hepatic and splenic injuries after controlling for injury severity and degree of shock. METHODS We retrospectively reviewed records from all adults with blunt hepatic and/or splenic injuries admitted to a Level I trauma center over a 4-year period. Demographics, physiologic variables, injury severity, and amount of blood transfused were analyzed. Univariate and multivariate analysis with logistic and linear regression were used to identify predictors of mortality and outcome. RESULTS One hundred forty-three (45%) of 316 patients presenting with blunt hepatic and/or splenic injuries received blood transfusion within the first 24 hours. Two hundred thirty patients (72.8%) were selected for nonoperative management, of whom 75 (33%) required transfusion in the first 24 hours. Transfusion was an independent predictor of mortality in all patients (odds ratio [OR], 4.75; 95% confidence interval [CI], 1.37-16.4; p = 0.014) and in those managed nonoperatively (OR, 8.45; 95% CI, 1.95-36.53; p = 0.0043) after controlling for indices of shock and injury severity. The risk of death increased with each unit of packed red blood cells transfused (OR per unit, 1.16; 95% CI, 1.10-1.24; p < 0.0001). Blood transfusion was also an independent predictor of increased hospital length of stay (coefficient, 5.45; 95% CI, 1.64-9.25; p = 0.005). CONCLUSION Blood transfusion is a strong independent predictor of mortality and hospital length of stay in patients with blunt liver and spleen injuries after controlling for indices of shock and injury severity. Transfusion-associated mortality risk was highest in the subset of patients managed nonoperatively. Prospective examination of transfusion practices in treatment algorithms of blunt hepatic and splenic injuries is warranted.

Percutaneous Drainage of Pancreatic Pseudocysts Is Associated With a Higher Failure Rate Than Surgical Treatment in Unselected Patients

OBJECTIVE The primary aim was to compare directly the effectiveness of percutaneous drainage versus surgical treatment of pancreatic pseudocysts in unselected patients. The authors also wished to identify factors that may predict a successful outcome with percutaneous drainage. SUMMARY BACKGROUND DATA Pancreatic pseudocysts are a common complication of pancreatitis, and recent data suggest that many pseudocysts may be observed or treated successfully by percutaneous drainage. Failures with percutaneous drainage have been recognized increasingly, and a direct comparison of percutaneous and surgical treatment was initiated to identify factors that may affect outcome with these approaches. METHODS A computerized index search of the medical records of patients with a diagnosis of pancreatic pseudocyst was performed from 1984 to 1995. One hundred seventy-three patients were identified retrospectively and assigned to treatment groups: observation (n = 41), percutaneous drainage (n = 66), or surgical treatment (n = 66). Data on demographics, clinical presentation, pseudocyst etiology and characteristics, diagnostic evaluation, management, and outcome were obtained. Treatment failure was defined as persistence of a symptomatic pseudocyst or the need for additional intervention other than the original treatment. RESULTS The etiology of pancreatitis, clinical presentation, and diagnostic evaluation did not differ between groups. Twenty-seven percent had documented chronic pancreatitis, and the etiology of pancreatitis was alcohol in 61% of patients. Mean pseudocyst size was 4.2 +/- 1 cm, 8.2 +/- 1.1 cm, and 7.4 +/- 1.3 cm in the observed, percutaneously treated, and surgically treated groups, respectively. Expectant treatment was successful in 93% of patients. Percutaneous drainage was successful in 42% of patients, whereas surgical treatment resulted in a success rate of 88%. Patients treated by percutaneous drainage had a higher mortality rate (16% vs. 0%), a higher incidence of complications (64% vs. 27%), and a longer hospital stay (45 +/- 5 days vs. 18 +/- 2 days) than patients treated by surgery. Eighty-seven percent of patients in whom percutaneous drainage failed required surgical salvage therapy. Multiple logistic regression analysis failed to reveal any factors significantly associated with a successful outcome after percutaneous drainage. CONCLUSIONS Percutaneous drainage results in higher mortality and morbidity rates and a longer hospital stay than surgical treatment of pancreatic pseudocysts. The clinical benefit of percutaneous drainage of pancreatic pseudocysts in unselected patients has not been realized, and the role of this treatment should be established in a clinical trial.

A statewide, population-based time-series analysis of the outcome of ruptured abdominal aortic aneurysm.

OBJECTIVES The purpose of this study was to perform the first statewide, population-based, time-series analysis of the frequency of ruptured abdominal aortic aneurysm (RAAA), to determine the outcomes of RAAA, and to assess the association of patient, physician, and hospital factors with survival after RAAA. The hypotheses of the study were as follows: 1) the rate of RAAA would increase over time and 2) patient, surgeon, and hospital factors would be associated with survival. BACKGROUND Ruptured abdominal aortic aneurysm is a life-threatening emergency that presents the surgeon with a technically demanding challenge that must be met and surmounted in a short time if the patient is to survive. METHODS Data were obtained from the following four separate data sources: 1) the North Carolina Hospital Discharge database, 2) the North Carolina American Hospital Association database, 3) the North Carolina State Medical Examiners database, and 4) the Area Resource File. All patients with the diagnosis of an abdominal aortic aneurysm (AAA) were selected for initial assessment. Patients were grouped into those with and those without rupture of the abdominal aneurysm. RESULTS During the 6 years of the study, 14,138 patients were admitted with a diagnosis of AAA. Of these, 1480 (10%) had an RAAA. The yearly number of patients with elective AAAs increased 33% from 1889 in 1988 to 2518 in 1993. The yearly number of RAAAs increased 27% from 203 to 258. The mortality rate for AAA was 5%, as compared with 54% in RAAA patients. The patients age was found to be the most powerful predictor of survival. Univariate logistic regression analyses demonstrated an association of the surgeons experience with RAAA and patient survival after RAAA. Analysis of the survival rates of board-certified and nonboard-certified surgeons demonstrated that patients with RAAAs who were treated by board-certified surgeons had significantly better survival. When the survival was compared in small (less than 100 beds) and large (more than 100 beds) hospitals, survival was significantly better in the larger hospitals. CONCLUSIONS Ruptured abdominal aortic aneurysm remains a highly lethal lesion, even in the best of hands. Despite the many improvements in the care of seriously ill patients, there was no significant improvement in the survival of RAAA during this study. This suggests that early diagnosis is the best hope of survival in these patients. The study demonstrated that survival after RAAA was related most strongly to patient age at the time of the RAAA. The physicians and the hospitals experience with RAAA, the physicians background as measured by board certification, and the type of hospital at which the operation was performed (small vs. large) also may be associated with survival. These findings may have important implications for the regionalization of care and the education and credentialling of physicians. Given the lack of recent progress of improving the outcome of RAAA, aggressive efforts to treat patients before rupture are appropriate.

Proficiency of Surgeons in Inguinal Hernia Repair Effect of Experience and Age

Objectives:We examined the influence of surgeon age and other factors on proficiency in laparoscopic or open hernia repair. Summary Background Data:In a multicenter, randomized trial comparing open and laparoscopic herniorrhaphies, conducted in Veterans Administration hospitals (CSP 456), we reported significant differences in recurrence rates (RR) for the laparoscopic procedure as a result of surgeons’ experience. We have also reported significant differences in RR for the open procedure related to resident postgraduate year (PGY) level. Methods:We analyzed data from unilateral laparoscopic and open herniorrhaphies from CSP 456 (n = 1629). Surgeons experience (experienced ≥250 procedures; inexperienced <250), surgeons age, median PGY level of the participating resident, operation time, and hospital observed-to-expected (O/E) ratios for mortality were potential independent predictors of RR. Results:Age was dichotomized into older (≥45 years) and younger (<45 years). Surgeons inexperience and older age were significant predictors of recurrence in laparoscopic herniorrhaphy. The odds of recurrence for an inexperienced surgeon aged 45 years or older was 1.72 times that of a younger inexperienced surgeon. For open repairs, although surgeons age and operation time appeared to be related to recurrence, only median PGY level of <3 was a significant independent predictor. Conclusion:This analysis demonstrates that surgeons age of 45 years and older, when combined with inexperience in laparoscopic inguinal herniorrhaphies, increases risk of recurrence. For open repairs, only a median PGY level of <3 was a significant risk factor.

Massive transfusion in trauma patients: tissue hemoglobin oxygen saturation predicts poor outcome.

BACKGROUND Severely bleeding trauma patients requiring massive transfusion (MT) often experience poor outcomes. Our purpose was to determine the potential role of near infrared spectrometry derived tissue hemoglobin oxygen saturation (StO2) monitoring in early prediction of MT, and in the identification of those MT patients who will have poor outcomes. METHODS Data from a prospective multi-institution StO2 monitoring study were analyzed to determine the current epidemiology of MT (defined as transfusion volume >/=10 units packed red blood cells in 24 hours of hospitalization). Multivariate logistic regression was used to develop prediction models. RESULTS Seven US level I trauma centers (TC) enrolled 383 patients. 114 (30%) required MT. MT progressed rapidly (40% exceeded MT threshold 2 hours after TC arrival, 80% after 6 hours). One third of MT patients died. Two thirds of deaths were due to early exsanguination and two thirds of early exsanguination patients died within 6 hours. One third of the early MT survivors developed multiple organ dysfunction syndrome. MT could be predicted with standard, readily available clinical data within 30 minutes and 60 minutes of TC arrival (area under the receiver operating characteristic curve = 0.78 and 0.80). In patients who required MT, StO2 was the only consistent predictor of poor outcome (multiple organ dysfunction syndrome or death). CONCLUSION MT progresses rapidly to significant morbidity and mortality despite level I TC care. Patients who require MT can be predicted early, and persistent low StO2 identifies those MT patients destined to have poor outcome. The ultimate goal is to identify these high risk patients as early as possible to test new strategies to improve outcome. Further validation studies are needed to analyze appropriate allocation and study appropriate use of damage control interventions.

Wound coverage with cultured autologous keratinocytes: use after burn wound excision, including biopsy followup.

Cultured autologous keratinocytes (CAK) have been used in eight patients as part of their definitive treatment for burn wound closure. The CAK grafts were placed on surgically excised wounds rather than mature granulation tissue. This technique guaranteed that permanent skin coverage derived from cultured cells, and not residual epidermal cells from surviving dermis. Graft take was variable, ranging from zero in the case of one of the children to 85%. Long-term assessment noted adequate permanent coverage, confirmed by biopsy. Electron micrographs demonstrated no well formed anchoring fibrils, which may account for the graft fragility which has been reported as much as 1 year postgraft. Advantages of using CAK are that an acceptable permanent wound closure can be achieved without depending on donor site availability. An almost unlimited quantity of skin is available because the original biopsy can be expanded manyfold in the laboratory.

Extracapsular extension of the sentinel lymph node metastasis: a predictor of nonsentinel node tumor burden.

ObjectiveTo identify predictors of nonsentinel node (NSN) tumor involvement in patients with a tumor-involved sentinel node (SN). Summary Background DataFor many breast cancer patients who undergo intraoperative lymphatic mapping and sentinel lymphadenectomy (LM/SL), the SN is the only tumor-involved axillary node. Associations between NSN tumor involvement and several clinical and histopathologic factors have been identified. The authors hypothesize that extracapsular extension (ECE) of the SN metastasis is highly predictive of NSN tumor involvement. MethodsBetween May 1998 and December 2001, 260 patients (263 cases) with clinical T1 or T2 (<5.0 cm) breast cancer underwent LM/SL at the University of North Carolina, using a combined blue dye and technetium sulfur colloid technique. In all cases with a tumor-involved SN, axillary lymph node dissection (ALND) was recommended. Statistical analysis, with Pearson chi-square tests, Fisher exact test, and multiple logistic regression, was performed. ResultsThe SN contained tumor in 74 (28.1%) cases. ALND was performed in 70 of the 74 cases. ECE of the SN metastasis was present in 18 (25.7%) of the 70 cases. Patients with ECE of the SN metastasis were more likely to have NSN tumor involvement and had a greater total number of tumor-involved nodes than patients without ECE of the SN metastasis. Increasing size of the SN metastasis and increasing size of the primary tumor, examined as continuous variables, were associated with an increased likelihood of NSN tumor involvement on univariate analysis. However, only ECE of the SN metastasis was associated with NSN tumor involvement on multivariate analysis. ConclusionsECE of the SN metastasis is a strong predictor of NSN tumor involvement. All patients with ECE of the SN metastasis should undergo mandatory completion ALND.