Primary blast lung injury simulator: a new computerised model.

Mathematical modelling and computational simulation are becoming increasingly important tools in many fields of medicine where in vivo studies are expensive, difficult or impractical. This is particularly the case with primary blast lung injury, and in this paper, we give a brief overview of mathematical models before describing how we generated our blast lung injury simulator and describe some early results of its use.

Primary blast lung injury - a review.

Bomb or explosion-blast injuries are likely to be increasingly encountered as terrorist activity increases and pre-hospital medical care improves. We therefore reviewed the epidemiology, pathophysiology and treatment of primary blast lung injury. In addition to contemporary military publications and expert recommendation, an EMBASE and MEDLINE search of English speaking journals was undertaken using the medical subject headings (MeSHs) 'blast injury' and 'lung injury'. Review articles, retrospective case series, and controlled animal modelling studies published since 2000 were evaluated. 6-11% of military casualties in recent conflicts have suffered primary blast lung injury but the incidence increases to more than 90% in terrorist attacks occurring in enclosed spaces such as trains. The majority of victims require mechanical ventilation and intensive care management. Specific therapies do not exist and treatment is supportive utilizing current best practice. Understanding the consequences and supportive therapies available to treat primary blast lung injury are important for anaesthetists.

Establishing and maintaining a robust Role 2 Afloat organisation within the Royal Naval Medical Services.

In 2009, the Royal Navy (RN) reconfigured the Role 2 maritime medical treatment capability, the Role 2 Afloat (R2A). This capability is now firmly established on a number of platforms in the fleet and was recently externally validated on RFA MOUNTS BAY prior to completion of an operational deployment supporting contingency operations in the Mediterranean. This article outlines the future challenges for R2A and offers suggestions on how to maintain a robust R2A organisation within the Royal Naval Medical Service (RNMS).

Prone position ventilation in the Role 2 Afloat environment.

Prone position ventilation is a life-saving technique for the management of hypoxic respiratory failure in ventilated patients. It has particular application in the isolated Role 2 Afloat (R2A) environment where both human and material resources are limited. It can be achieved with minimal training. This article describes the rationale behind prone position ventilation and equips the reader with the knowledge base that will allow the technique to be instigated.

The role of a nurse case manager in implementing a critical pathway for infrainguinal bypass surgery.

BACKGROUND: A previous study showed the effectiveness of a clinical pathway for infrainguinal bypass surgery in reducing postoperative length of stay (LOS) in an acute care setting. Most of the deviations from the pathway were due to patient factors (50%) and/or external disposition problems (30%), but 20% were related to physician or system problems that could potentially be modified. The current study examined those factors influencing LOS following infrainguinal bypass surgery and the impact of daily rounds by a nurse case manager--a vascular nurse specialist--on LOS and pathway deviations. METHODS: Data were collected through detailed chart review and prospective tracking of pathway deviations. LOS was compared in 58 patients on the modified pathway (with the nurse case manager) to 69 patients on the original pathway and 67 prepathway controls. Multivariate analysis was used to identify factors influencing postoperative LOS and to compare LOS among the three groups. RESULTS: Use of a nurse case manager significantly reduced physician-related deviations, from the pathway from 10% to 0% (p = .015), and reduced system-related deviations from 3% to 0%. Median postoperative LOS was 7 days before the pathway was begun, 6 days with the original pathway, and 5 days after the introduction of a vascular nurse specialist (p = .0001). There were no differences in rates of complications, rates of readmission, or mortality. CONCLUSIONS: Intervention by a nurse case manager facilitated implementation of a critical pathway for patients undergoing infrainguinal bypass surgery, especially by preventing patient deviations due to intrainstitutional factors.

Ileal pouch salvage following failed ileal pouch- anal anastomosis.

Attempts have been made to salvage failed ileal pouch-anal anastomoses (IPAA) performed for ulcerative colitis or familial polyposis coli. These can be categorized as total reconstruction of the IPAA, partial transabdominal approach, and partial transperineal approach. The aims of our study were to determine the overall success of pouch salvage; to examine the demographics, indications, and outcomes for each approach; and to assess anorectal physiology and patient satisfaction in those with successful salvage operations. We reviewed data, including results of anorectal manometry, from 29 patients undergoing salvage procedures for failed IPAA. Seventeen salvage attempts were successful, 11 attempts failed, and one patient was lost to follow-up. Success rates were 100% in the total reconstruction group, 25% in the partial transabdominal group, and 55% in the transperineal group. In those undergoing total reconstruction of the IPAA (n = 9), functional outcome, as measured by incontinence, improved with 50% reporting incontinence preoperatively compared to 0% postoperatively (P = 0.055). Mean 24-hour stool frequency and nighttime stool frequency declined. All patients reported satisfaction with their outcomes. Sixty percent of patients who underwent ileal pouch salvage following IPAA have been successful in avoiding permanent ileostomy. These results suggest that a continued effort to salvage failed IPAA, including the use of total reconstruction, is a viable alternative to permanent ileostomy.

A case-control assessment of risk factors for gallbladder carcinoma.

Gallbladder carcinoma is an uncommon, but highly fatal disease. Its symptoms frequently mirror those of gallstone disease, and in most instances, diagnosis is an incidental finding at surgery. While risk factors have been suggested for this cancer, many may in reality simply be a consequence of the older age of the population. This study is one of the few to approach this question by using a case-control study design comparing gallbladder carcinoma patients with a gallstone population, coupled with multivariate analysis to determine age-independent risk factors. Univariate analyses showed gallbladder carcinoma patients to be older than gallstone patients and to have many age-associated diseases. Following multiple regression adjustment for age, this disease was associated with female gender and with a previous history of gallstone symptoms. Carcinoma patients were less likely to have cholesterol gallstones in their gallbladders at surgery. A previous history of smoking was a substantial risk but of borderline statistical significance. Previous studies report associations that may be due to the older age of the gallbladder carcinoma patient. Our results show that after adjusting for age with multivariate analysis, gallbladder cancer subjects were predominantly female, more likely to report previous gallstone symptomology, and to smoke. While gallstones were not universally isolated from carcinoma patients at cholecystectomy, when present, they were less frequently classified as cholesterol gallstones based on visual inspection. Further cohort studies which target these populations will allow us to gain a more solid consensus on the risk factors for this disease.

Early outcome of in situ femorotibial reconstruction among patients with diabetes alone versus diabetes and end-stage renal failure: analysis of 83 limbs.

PURPOSE: Both end-stage renal disease and diabetes have been demonstrated to have a negative effect on the outcome of infrainguinal arterial reconstruction, primarily because of increased perioperative morbidity and wound complications. This study was undertaken to determine whether the combination of these comorbid factors affects the outcome of distal arterial reconstruction. METHODS: Eighty-three distal lower extremity arterial bypasses originating from the femoral artery and terminating at the peroneal, anterior, or posterior tibial artery were performed on 76 patients over a 5-year period at a tertiary care medical center. Autogenous greater saphenous vein was used as the bypass conduit in all instances. Combined inflow and composite vein procedures were excluded. RESULTS: There was one perioperative death, for a mortality rate of 1.2%. The diabetes mellitus (DM) plus end-stage renal disease (DM+ESRD) cohort displayed a significantly lower 1-year primary patency rate compared with the diabetes mellitus cohort, 53% versus 82% (p < 0.02). However, the limb salvage rate for the DM+ESRD and DM cohorts during the same time interval were not significantly different, 63% versus 84% (p < 0.06). The 52% 1-year survival rate for the DM+ESRD cohort was strikingly lower than the 90% 1-year survival rate for the DM cohort (p < 0.002). CONCLUSION: Despite the use of the optimal autogenous conduit, the combination of diabetes and end-stage renal disease can be expected to significantly decrease primary graft patency without affecting limb salvage. The greatest effect of these comorbid factors is on patient survival.

Impact of a critical pathway on postoperative length of stay and outcomes after infrainguinal bypass.

PURPOSE: To determine the effect of a critical pathway on postoperative length of stay and outcomes after infrainguinal bypass. METHODS: A critical pathway for care of patients after infrainguinal bypass was introduced in December 1995 to coordinate postoperative care at our institution. We compared care of 67 consecutively treated patients before institution of the pathway with care of 69 consecutively treated patients with the critical pathway in place. Data collection was done by means of chart review. Univariate analyses were used to identify differences between prepathway and postpathway patients and to identify factors influencing postoperative length of stay. Multivariate analysis was used to identify factors that influenced length of stay and to examine the effect of use of the pathway after adjusting for other factors. RESULTS: Patients on the pathway were similar to prepathway controls with respect to comorbid illnesses, vascular risk factors, indications for surgical treatment, type of conduit, and type of operation. Factors associated with longer postoperative stays included distal anastomoses to tibial rather than popliteal vessels (p = 0.02), preexisting cardiac disease (p = 0.005), postoperative complications (p = 0.0003), lower preoperative hematocrit (p = 0.01), and elevated preoperative creatinine level (p = 0.006). Overall, pathway patients had somewhat shorter postoperative lengths of stay (median value 7 days; range 2 to 29 days) than prepathway patients (median value 6 days; range 2 to 35; p = 0.01), and the two groups had similar frequencies of postoperative complications, readmission, and 6-month mortality. However, patients on the pathway were more likely to be discharged to an intermediate-care facility rather than directly home. After 12 patients with extraordinarily prolonged postoperative stays were excluded, multivariate analysis indicated that pathway patients had significantly shorter postoperative stays (p = 0.001). However, the difference was not significant if patients with extraordinarily long postoperative stays were included in the analysis (p = 0.28). CONCLUSION: Use of a critical pathway was associated with a modest decrease in postoperative length of stay for most patients. This was accomplished without an adverse effect on readmission, complication, or mortality rates. However, the decrease in stay may have been achieved primarily by discharging more patients to intermediate-care facilities. The pathway did not appear to have any effect when the subset of patients with extraordinarily long stays because of complex medical problems was included.

Is splenectomy more dangerous for massive spleens?

BACKGROUND: Reports vary about whether risks are greater for removal of massive (> or = 1500 g) spleens than for smaller (< 1500 g) spleens. We sought to determine the hazards of splenectomy. METHODS: We reviewed 223 consecutive adults with elective splenectomies for hematologic diseases. Morbidity and mortality rates were combined with published data to create a meta-analysis. RESULTS: Patients with massive spleens are more likely to have postoperative complications (relative risk [RR] 2.1, 95% confidence interval [CI] 1.3 to 3.4; P = 0.003) and death (RR 4.7, 95% CI, 1.5 to 15.1; P = 0.01). However, when the investigation is restricted to comparable diagnoses, patients with massive spleens do not differ from those with smaller spleens regarding complications (RR 1.4, 95% CI, 0.8 to 2.7; P = 0.3) or mortality (RR 2.1, 95% CI, 0.5 to 9.7; P = 0.4). These observations are confirmed by metaanalysis. Furthermore, multivariate analysis indicts age as a critical risk of complications and death. CONCLUSIONS: Increased age and underlying illness are the predominant factors associated with morbidity and mortality following splenectomy for hematologic disease. Adjusting for age and diagnosis, spleen size is not a hazard.

Durability of early prosthetic dialysis graft cannulation: results of a prospective, nonrandomized clinical trial.

PURPOSE: Initiation of hemodialysis frequently requires temporary central venous catheterization, which leads to subsequent venous stenosis in 50% of patients. These lesions severely limit upper extremity dialysis fistula creation. The present study was undertaken to determine whether early cannulation (EC) allowed omission of temporary venous catheterization without affecting perioperative morbidity and long-term graft patency. METHODS: Seventy-nine prosthetic grafts for hemodialysis were placed in 76 patients over a 40-month period. Patients who required hemodialysis between 24 and 72 hours after surgery were assigned to EC. The remaining grafts underwent late cannulation (LC) after postoperative day 14. All grafts were constructed with a 6 mm stretch-expanded polytetrafluoroethylene conduit in the brachial artery-to-axillary vein position. Statistical analysis of cumulative primary patency estimates and patient survival data were determined by Kaplan-Meier analysis and log-rank test, patient variables were compared using chi 2 and Fisher's exact test, and multivariate analysis was performed using Cox's proportional hazard model. RESULTS: Forty-eight patients underwent EC and 31 underwent LC. There were no significant differences regarding age (mean, 61.5 years), history of diabetes, congestive heart failure, hematocrit level (mean, 30%), or presence of peripheral vascular disease. Thrombosis occurred before cannulation in one of 48 ECs (2.0%) and one of 31 LCs (3.2%). There were no episodes of cannulation hemorrhage or wound infection in either group. Cumulative primary patency estimates for EC were 0.89, 0.82, and 0.70 at 3, 6, and 12 months, respectively. These were not significantly different from the LC estimates of 0.86, 0.78, and 0.74 at 3, 6, and 12 months, respectively. Overall, patients who had a history of peripheral vascular disease had a significantly decreased 12-month patency rate (60% vs 74%; p = 0.05). Central venous catheters were omitted in 47 of 48 EC patients. CONCLUSION: EC of prosthetic dialysis grafts does not increase perioperative morbidity rates or decrease 12-month cumulative primary patency rates.

Relationship of cardiovascular risk factors to racial differences in femoral bypass surgery and abdominal aortic aneurysmectomy in Massachusetts.

UNLABELLED: Atherosclerosis is more severe in blacks than in whites, but abdominal aortic aneurysms, which have traditionally been thought to have an atherosclerotic etiology, appear to be less common in blacks. Because of this incongruity, we compared risk factor profiles in patients undergoing abdominal aortic aneurysm repair and patients undergoing femoral bypass for atherosclerotic occlusive disease. A dual case-control study was conducted, first, comparing patients who had undergone aneurysmectomy to a control group of patients who had undergone appendectomy; and then comparing patients who had undergone femoral bypass surgery to the same appendectomy controls. We initially used hospital discharge data for the entire state of Massachusetts and, in a second phase, data obtained from a review of medical records from Boston University Medical Center Hospital and Boston City Hospital. The statewide database indicated that rates of femoral bypass surgery were higher in blacks than in whites, but after adjusting for differences in hypertension, diabetes, and low socioeconomic status, the black/white odds ratio for femoral bypass fell to 1.44 (95% confidence interval: 1.08, 1.92). A similar analysis based on the hospital chart review, provided better control of confounding and indicated that there was no racial difference in rates of femoral bypass after correcting for other risk factors (odds ratio = 0.94; 95% confidence interval: 0.40, 2.22; p = 0.90). In contrast, the statewide database found higher rates of abdominal aortic aneurysm surgery in whites, and particularly in white males. Smoking and hypertension were strong risk factors for aneurysmectomy, but diabetes mellitus and socioeconomic status were not. After adjusting for other variables, the black/white odds ratio for aneurysmectomy was 0.29 (95% confidence interval: 0.07, 1.23; p = 0.09). CONCLUSIONS: Substantial differences are found in the risk factor profiles for aneurysmal disease and femoral atherosclerotic occlusive disease. Diabetes is a particularly strong risk factor for femoral disease, but not for aneurysmal disease. In addition, blacks had higher rates of femoral bypass surgery in Massachusetts, but the apparent racial difference appeared to be due to a greater prevalence of hypertension, smoking, and diabetes in blacks. In contrast, abdominal aortic aneurysms occurred predominantly in white males, and adjustment for other risk factors further accentuated the greater risk in whites.

Risks of synchronous gastrointestinal or biliary surgery with splenectomy for hematologic disease.

BACKGROUND: The addition of splenectomy to a gastrointestinal (GI) operation may have an adverse effect on mortality, morbidity, and even survival. OBJECTIVE: To determine the risks of the converse: synchronous GI surgery appended to splenectomy for hematologic diseases. DESIGN: Retrospective cohort. SETTING: Multiple hospitals comprising an affiliated surgical training program. PATIENTS: Consecutive sample of 207 adults (mean age, 49 years) with splenectomies for hematologic diseases. INTERVENTION: Splenectomy and concomitant GI or biliary surgery (group 1, n=19) and splenectomy alone (group 2, n=188). MAIN OUTCOME MEASURES: Length of hospital or intensive care unit stay, later operations, postoperative infections, postoperative abdominal abscess, major complications, and death. RESULTS: Preoperative and intraoperative factors were similar in both groups. Operative mortality was 3 of 19 in group 1 and 8 of 188 in group 2 (p=.07). The mean number of major complications tended to be higher in group 1 (1.5 vs 0.5, P=07). Despite no difference between the incidences of overall postoperative infections, patients in group 1 were much more likely to develop an abdominal abscess (4 of 19 vs 3 of 188, P=.002). Logistic regression established that patients undergoing splenectomy and synchronous GI or biliary surgery were 25 times more likely to develop an intra-abdominal abscess than were patients with splenectomy alone, even controlling for confounding factors (odds ratio, 24.7; 95% confidence interval, 3.1 to 196; P=.002). CONCLUSIONS: Synchronous GI or biliary surgery with splenectomy for hematologic disease increases the risk of intra-abdominal abscess and should be avoided. Complication and mortality rates may also be increased.

Risk factors for chronic venous insufficiency: a dual case-control study.

PURPOSE: Most epidemiologic studies on chronic venous insufficiency (CVI) are cross-sectional surveys that suggest potential risk factors by describing their population. However, these relationships could be due to the CVI population's older age. We performed a dual case-control study with multivariate analysis to address this issue. METHODS: Ninety-three patients with venous ulcers, 129 patients with varicose veins (VV), and 113 general population control patients from two hospitals were interviewed by use of a standardized questionnaire covering medical history, patient demographics, medications, and lifestyle questions. Univariate and multivariate analyses were used to compare the groups. RESULTS: Univariate analyses showed CVI to be characterized by several factors, many of which were found to be age related after multivariate analysis. Age-adjusted relationships for CVI include male sex and obesity. Histories of serious leg injury or phlebitis were important associations resulting in a 2.4-fold and 25.7-fold increase in risk for CVI, respectively. After adjusting for age, subjects with VV tend to be younger and female, to more frequently have a history of phlebitis, and to report a family history of VV more frequently than control subjects. CONCLUSIONS: Many of the previously suggested associations found with CVI are in reality due to this population's greater age. Patients with CVI are older, male, obese, have a history of phlebitis, and have a history of serious leg injury. These results suggest that a prior deep vein thrombosis, either clinical or subclinical, may be a predisposing factor for CVI.

Racial differences in the incidence of femoral bypass and abdominal aortic aneurysmectomy in Massachusetts: relationship to cardiovascular risk factors.

PURPOSE: Atherosclerotic disease appears to be more severe in black patients than in white patients, but abdominal aortic aneurysms, which have traditionally been believed to have an atherosclerotic cause, are reported to be less common in black patients than in white patients. Our goals were to compare and contrast factors associated with the development of abdominal aortic aneurysms and clinically significant atherosclerotic occlusive disease (1) to determine whether these diseases share a common cause and (2) to explore their association with race. METHODS: Dual case-control studies were conducted with multivariate analysis to compare cases (patients undergoing aneurysmectomy or patients undergoing femoral bypass) with a comparison group consisting of patients who had undergone appendectomy. Two data sources were used: (1) hospital discharge data for Massachusetts from 1984 through 1988 and (2) medical records at University Hospital of Boston and Boston City Hospital. For both the Massachusetts database and the hospital chart review, records were obtained for all patients discharged between January 1984 and December 1988 with an International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) procedure code for abdominal aortic aneurysm resection (38.44) or aneurysmorrhaphy (38.34) or with a procedure code for femoral artery bypass/reconstruction (39.29). To conduct a nested case-control study, records were also obtained for a control group consisting of patients between the ages of 50 and 84 years who had undergone appendectomy during the same 5-year period. RESULTS: Black patients had higher rates of femoral bypass than did white patients after adjustment for age and sex (odds ratio = 1.97; 95% confidence interval: 1.49, 2.61; p < 0.0001). However, femoral bypass was also associated with hypertension, diabetes, and low household income. After adjusting for these additional factors in the statewide data set, the black/white odds ratio for femoral bypass was only 1.44 (95% confidence interval: 1.08, 1.92). The parallel case-control study at University Hospital and Boston City Hospital, which provided information about smoking status and more accurate ascertainment of coexisting hypertension and diabetes, indicated that there was no racial difference in rates of femoral bypass after correcting for these additional risk factors (odds ratio = 0.94; 95% confidence interval: 0.40, 2.22; p = 0.90). In contrast, abdominal aortic aneurysmectomy occurred predominantly in white men. Aneurysmectomy was also associated with smoking and hypertension, but aneurysmectomy was not significantly associated with diabetes mellitus or family income. The black/white odds ratio for aneurysm was 0.29; (95% confidence interval: 0.07, 1.23; p = 0.09 after adjustment for other variables). CONCLUSIONS: Hypertension, smoking, and male sex are risk factors for the development of femoral atherosclerosis and abdominal aortic aneurysm formation. However, abdominal aortic aneurysms occur predominantly in white men and do not appear to be associated with diabetes mellitus or income. In contrast, the higher rate of femoral artery bypass in black patients is probably the result of greater prevalence among black patients of hypertension, diabetes, smoking, and perhaps by other ill-defined factors associated with socioeconomic status.

Traction injury to the liver during laparoscopic cholecystectomy.

We describe an intraoperative complication of laparoscopic cholecystectomy and make recommendations to avoid its occurrence. We describe a case in which the liver was lacerated during a routine laparoscopic cholecystectomy. The laceration occurred when the gallbladder was retracted into the suprahepatic space, causing a traction injury of the quadrate lobe, 2 cm lateral to the falciform ligament. The placement of the epigastric trocar through the falciform ligament fixed the liver to the abdominal wall, facilitating the injury. When placing the epigastric trocar, care should be taken to avoid placement through the falciform ligament. If this is not possible, retraction of the gallbladder into the suprahepatic space should be accomplished while observing the liver edge. If the liver edge seems to be under tension, division of the falciform ligament to allow for easy retraction of the liver is recommended.

Functional outcomes in limb salvage vascular surgery.

BACKGROUND: The crisis in health care brings a new focus to defining successful outcomes of medical treatments. The surgical literature has been criticized for not assessing functional outcomes in addition to technical success. METHODS: We evaluated the functional outcomes of limb salvage surgery over 3 years in 38 patients 65 years of age and older with limb-threatening ischemia. The RAND-36-Item Health Survey 1.0 was used as a health assessment tool. RESULTS: In spite of an 80% limb salvage rate, only 58% of patients survived 3 years and only 25% survived with the index limb and were able to walk. The RAND scores of patients whose limbs were amputated did not significantly differ from those of patients whose surgery was successful. CONCLUSION: Functional outcome goals need to be better defined for patients who need limb salvage vascular operations to enhance the quality of care given these patients and to be in concert with emerging health policy.