Vulnerability of cholecystokinin-expressing GABAergic interneurons in the unilateral intrahippocampal kainate mouse model of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is characterized by recurrent spontaneous seizures and behavioral comorbidities. Reduced hippocampal theta oscillations and hyperexcitability that contribute to cognitive deficits and spontaneous seizures are present beyond the sclerotic hippocampus in TLE. However, the mechanisms underlying compromised network oscillations and hyperexcitability observed in circuits remote from the sclerotic hippocampus are largely unknown. Cholecystokinin (CCK)-expressing basket cells (CCKBCs) critically participate in hippocampal theta rhythmogenesis, and regulate neuronal excitability. Thus, we examined whether CCKBCs were vulnerable in nonsclerotic regions of the ventral hippocampus remote from dorsal sclerotic hippocampus using the intrahippocampal kainate (IHK) mouse model of TLE, targeting unilateral dorsal hippocampus. We found a decrease in the number of CCK+ interneurons in ipsilateral ventral CA1 regions from epileptic mice compared to those from sham controls. We also found that the number of boutons from CCK+ interneurons was reduced in the stratum pyramidale, but not in other CA1 layers, of ipsilateral hippocampus in epileptic mice, suggesting that CCKBCs are vulnerable. Electrical recordings showed that synaptic connectivity and strength from surviving CCKBCs to CA1 pyramidal cells (PCs) were similar between epileptic mice and sham controls. In agreement with reduced CCKBC number in TLE, electrical recordings revealed a significant reduction in amplitude and frequency of IPSCs in CA1 PCs evoked by carbachol (commonly used to excite CCK+ interneurons) in ventral CA1 regions from epileptic mice versus sham controls. These findings suggest that loss of CCKBCs beyond the hippocampal lesion may contribute to hyperexcitability and compromised network oscillations in TLE.

The critical role of persistent sodium current in hippocampal gamma oscillations

Gamma network oscillations in the brain are fast rhythmic network oscillations in the gamma frequency range (~30-100 Hz), playing key roles in the hippocampus for learning, memory, and spatial processing. There is evidence indicating that GABAergic interneurons, including parvalbumin-expressing basket cells (PVBCs), contribute to cortical gamma oscillations through synaptic interactions with excitatory cells. However, the molecular, cellular, and circuit underpinnings underlying generation and maintenance of cortical gamma oscillations are largely elusive. Recent studies demonstrated that intrinsic and synaptic properties of GABAergic interneurons and excitatory cells are regulated by a slowly inactivating or non-inactivating sodium current (i.e., persistent sodium current, I_NaP), suggesting that I_NaP is involved in gamma oscillations. Here, we tested whether I_NaP plays a role in hippocampal gamma oscillations using pharmacological, optogenetic, and electrophysiological approaches. We found that I_NaP blockers, phenytoin (40 μM and 100 μM) and riluzole (10 μM), reduced gamma oscillations induced by optogenetic stimulation of CaMKII-expressing cells in CA1 networks. Whole-cell patch-clamp recordings further demonstrated that phenytoin (100 μM) reduced I_NaP and firing frequencies in both PVBCs and pyramidal cells without altering threshold and amplitude of action potentials, but increased rheobase in both cell types. These results suggest that I_NaP in pyramidal cells and PVBCs is required for hippocampal gamma oscillations, supporting a pyramidal-interneuron network gamma model. Phenytoin-mediated modulation of hippocampal gamma oscillations may be a mechanism underlying its anticonvulsant efficacy, as well as its contribution to cognitive impairments in epilepsy patients.

Group I metabotropic glutamate receptors generate two types of intrinsic membrane oscillations in hippocampal oriens/alveus interneurons

GABAergic interneurons in the hippocampus are critically involved in almost all hippocampal circuit functions including coordinated network activity. Somatostatin-expressing oriens-lacunosum moleculare (O-LM) interneurons are a major subtype of dendritically projecting interneurons in hippocampal subregions (e.g., CA1), and express group I metabotropic glutamate receptors (mGluRs), specifically mGluR₁ and mGluR₅. Group I mGluRs are thought to regulate hippocampal circuit functions partially through GABAergic interneurons. Previous studies suggest that a group I/II mGluR agonist produces slow supra-threshold membrane oscillations (<0.1 Hz), which are associated with high-frequency action potential (AP) discharges in O-LM interneurons. However, the properties and underlying mechanisms of these slow oscillations remain largely unknown. We performed whole-cell patch-clamp recordings from mouse interneurons in the stratum oriens/alveus (O/A interneurons) including CA1 O-LM interneurons. Our study revealed that the selective mGluR_1/5 agonist (S)-3,5-dihydroxyphenylglycine (DHPG) induced slow membrane oscillations (<0.1 Hz), which were associated with gamma frequency APs followed by AP-free perithreshold gamma oscillations. The selective mGluR₁ antagonist (S)-(+)-α-Amino-4-carboxy-2-methylbenzeneacetic acid (LY367385) reduced the slow oscillations, and the selective mGluR₅ antagonist 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP) partially blocked them. Blockade of nonselective cation-conducting transient receptor potential channels, L-type Ca²⁺ channels, or ryanodine receptors all abolished the slow oscillations, suggesting the involvement of multiple mechanisms. Our findings suggest that group I mGluR activation in O/A interneurons may play an important role in coordinated network activity, and O/A interneuron vulnerability to excitotoxicity, in disease states like seizures, is at least in part due to an excessive rise in intracellular Ca²⁺.

Cell Type-specific Intrinsic Perithreshold Oscillations in Hippocampal GABAergic Interneurons

The hippocampus plays a critical role in learning, memory, and spatial processing through coordinated network activity including theta and gamma oscillations. Recent evidence suggests that hippocampal subregions (e.g., CA1) can generate these oscillations at the network level, at least in part, through GABAergic interneurons. However, it is unclear whether specific GABAergic interneurons generate intrinsic theta and/or gamma oscillations at the single-cell level. Since major types of CA1 interneurons (i.e., parvalbumin-positive basket cells (PVBCs), cannabinoid type 1 receptor-positive basket cells (CB1BCs), Schaffer collateral-associated cells (SCAs), neurogliaform cells and ivy cells) are thought to play key roles in network theta and gamma oscillations in the hippocampus, we tested the hypothesis that these cells generate intrinsic perithreshold oscillations at the single-cell level. We performed whole-cell patch-clamp recordings from GABAergic interneurons in the CA1 region of the mouse hippocampus in the presence of synaptic blockers to identify intrinsic perithreshold membrane potential oscillations. The majority of PVBCs (83%), but not the other interneuron subtypes, produced intrinsic perithreshold gamma oscillations if the membrane potential remained above -45 mV. In contrast, CB1BCs, SCAs, neurogliaform cells, ivy cells, and the remaining PVBCs (17%) produced intrinsic theta, but not gamma, oscillations. These oscillations were prevented by blockers of persistent sodium current. These data demonstrate that the major types of hippocampal interneurons produce distinct frequency bands of intrinsic perithreshold membrane oscillations.

Assessment of Apparent Vena Caval Penetration by the Greenfield Filter

Purpose:

To examine and elucidate the mechanisms for apparent “penetration” by Greenfield vena caval filters.

Methods:

Two filters were placed in the inferior venae cavae (IVC) of four immature sheep and followed with cavography for 1 year. Two animals underwent computed tomography (CT) and laparoscopic examination. At necropsy, the vena cava and adjacent structures of all four animals were examined grossly and histologically.

Results:

Based upon cavography and CT imaging, all filters appeared to penetrate the vena cava at 12 months. However, at laparoscopy, no hooks or limbs were exposed, and the pericaval tissues remained intact; each hook or limb was within the adventitia or encapsulated in scar tissue. Histology of the tissue at the hook sites revealed remodeling of the intimal surface of the IVC and thinning of the adventitia.

Conclusions:

Based upon these data, we hypothesize that the vena cava gradually adapts by medial and adventitial thinning and myointimal remodeling to the radial force exerted by a filter. This process allows increase in the filter base diameter while maintaining the integrity of the cava and protecting adjacent structures.

Development of the sexually dimorphic nucleus of the preoptic area and the influence of estrogen-like compounds

One of the well-defined sexually dimorphic structures in the brain is the sexually dimorphic nucleus, a cluster of cells located in the preoptic area of the hypothalamus. The rodent sexually dimorphic nucleus of the preoptic area can be delineated histologically using conventional Nissl staining or immunohistochemically using calbindin D28K immunoreactivity. There is increasing use of the bindin D28K-delineated neural cluster to define the sexually dimorphic nucleus of the preoptic area in rodents. Several mechanisms are proposed to underlie the processes that contribute to the sexual dimorphism (size difference) of the sexually dimorphic nucleus of the preoptic area. Recent evidence indicates that stem cell activity, including proliferation and migration presumably from the 3^rd ventricle stem cell niche, may play a critical role in the postnatal development of the sexually dimorphic nucleus of the preoptic area and its distinguishing sexually dimorphic feature: a signifi-cantly larger volume in males. Sex hormones and estrogen-like compounds can affect the size of the sexually dimorphic nucleus of the preoptic area. Despite considerable research, it remains un-clear whether estrogen-like compounds and/or sex hormones increase size of the sexually dimor-phic nucleus of the preoptic area via an increase in stem cell activity originating from the 3^rd ventricle stem cell niche.

Venous thrombosis incidence in burn patients: preliminary results of a prospective study

There are few prospective data on the incidence of deep venous thrombosis (DVT) in burn patients. In an on-going prospective study, hospitalized burn patients 18 years or older with an expected hospital length of stay more than 72 hours were imaged with baseline venous duplex ultrasound of all extremities within the first 48 hours after admission and weekly until discharge. Patient demographics and clinical risk factors for DVT were assessed. At the time of submission, 40 patients met screening criteria, and 30 were enrolled. Ultrasound diagnosed seven patients with 11 acute DVT for an incidence of 23%. One pulmonary embolism was documented. DVT patients had a mean age of 49 +/- 23 years with an average TBSA burn of 15 +/- 4% compared with those without thrombosis with a mean age of 44 +/- 17 years (P = NS) and TBSA burn of 18 +/- 25% (P = NS). There were no statistically significant differences for DVT patients in terms of age, number of central line days, hospital length of stay, or TBSA burned. Given the preliminary findings of this small study, we believe that all hospitalized burn patients are at risk for DVT. On-going investigation will be helpful in defining level of risk and improved prevention strategies for thromboembolic complications in burn patients.

Computed tomographic venography is specific but not sensitive for diagnosis of acute lower-extremity deep venous thrombosis in patients with suspected pulmonary embolus

PURPOSE

Duplex ultrasound scanning (US) is the accepted standard means of diagnosis for lower-extremity suprageniculate deep venous thrombosis (LE-DVT). Computed tomographic venography (CTV) has been proposed as an alternative modality for diagnosis of LE-DVT in patients with suspected pulmonary embolism (PE). This study compared CTV with US as a means of diagnosing acute LE-DVT.

METHODS

A retrospective review of US and CTV scans from 136 patients with suspected PE who underwent both studies to exclude acute LE-DVT at a single institution was performed. Studies were reviewed and coded in a blinded manner. US was considered to be the reference test. Direct costs of each study were determined by using commercial software.

RESULTS

The sensitivity and specificity rates of CTV were 71% and 93%, respectively. The positive predictive value, negative predictive value, and accuracy rates of CTV were 53%, 97%, and 90%, respectively. DVT localization was the same in eight of 10 cases in which the results of both US and CTV were positive. CTV costs and charges per study were greater than those of US by $46.88 and $602.00, respectively.

CONCLUSION

CTV is specific, but has a lower sensitivity rate and positive predictive value for the diagnosis of acute LE-DVT compared with US. Additionally, CTV is more costly than US scanning. Because of the lower sensitivity rate and positive predictive value and the increased cost of CTV, US remains the screening study of choice in cases of suspected acute LE-DVT.

Renal artery aneurysms: a 35-year clinical experience with 252 aneurysms in 168 patients

OBJECTIVE

To define the relevance of treating renal artery aneurysms (RAAs) surgically.

SUMMARY BACKGROUND DATA

Most prior definitions of the clinical, pathologic, and management features of RAAs have evolved from anecdotal reports. Controversy surrounding this clinical entity continues.

METHODS

A retrospective review was undertaken of 168 patients (107 women, 61 men) with 252 RAAs encountered over 35 years at the University of Michigan Hospital. Aneurysms were solitary in 115 patients and multiple in 53 patients. Bilateral RAAs occurred in 32 patients. Associated diseases included hypertension (73%), renal artery fibrodysplasia (34%), systemic atherosclerosis (25%), and extrarenal aneurysms (6.5%). Most RAAs were saccular (79%) and noncalcified (63%). The main renal artery bifurcation was the most common site of aneurysms (60%). RAAs were often asymptomatic (55%), with a diagnosis made most often during arteriographic study for suspected renovascular hypertension (42%).

RESULTS

Surgery was performed in 121 patients (average RAA size 1.5 cm), including 14 patients undergoing unilateral repair with contralateral RAA observation. The remaining 47 patients (average RAA size 1.3 cm) were not treated surgically. Operations included aneurysmectomy and angioplastic renal artery closure or segmental renal artery reimplantation, aneurysmectomy and renal artery bypass, and planned nephrectomy for unreconstructable renal arteries or advanced parenchymal disease. Eight patients underwent unplanned nephrectomy, being considered a technical failure of surgical therapy. Dialysis-dependent renal failure occurred in one patient. There were no perioperative deaths. Late follow-up (average 91 months) was available in 145 patients (86%). All but two arterial reconstructions remained clinically patent. Secondary renal artery procedures included percutaneous angioplasty, branch embolization, graft thrombectomy, and repeat bypass for late aneurysmal change of a vein conduit. Among 40 patients with clearly documented preoperative and postoperative blood pressure measurements, 60% had a significant decline in blood pressure after surgery while taking fewer antihypertensive medications. Late RAA rupture did not occur in the nonoperative patients, but no lessening of this group's hypertension was noted.

CONCLUSION

Surgical therapy of RAAs in properly selected patients provides excellent long-term clinical outcomes and is often associated with decreased blood pressure.

Thromboprophylaxis in an academic medical center

INTRODUCTION

Questions regarding which patients require prophylaxis for thromboembolism, what methods should be used and the appropriate duration of treatment remain unanswered.

METHODS AND MATERIALS

A retrospective review from a single academic medical center was undertaken to evaluate prophylactic strategies. Multiple sources of data were used to identify patients who were prophylaxed and those who developed deep vein thrombosis or pulmonary embolism. These data were analyzed to determine factors associated with successful prophylaxis including age, type of prophylaxis and admitting services.

RESULTS

A total of 22,030 patients were admitted of whom 7520 (36%) received prophylaxis and there were 523 thromboembolic events. Pneumatic compression devices and antiembolic stockings had the lowest incidence of failure, 2.2% and 3.2% respectively. There were significant differences in the rates of prophylaxis used by the five admitting services, being highest in surgery (40.8%) and lowest in gynecology (11.4%). However, these groups had the lowest incidence of venous thromboembolism (4.3%, 2.3%). Both of these groups used pneumatic compression as the method of choice (64.3% and 65.2%).

CONCLUSIONS

Thromboembolism prophylaxis reduces the incidence of DVT and PE, however, our study demonstrates the variable effectiveness of each method in different types of patients. Our data suggest that patient risk of DVT should be individually assessed and an appropriate method of prophylaxis should be applied when warranted.

Burnout among American surgeons

BACKGROUND

The long-term consequences of stress on the surgeon are unknown. One manifestation of stress is burnout. The purpose of this study was to measure the prevalence of burnout in actively practicing American surgeons.

METHODS

The Maslach Burnout Inventory and a questionnaire of our own design were sent to 1706 graduates of various University of Michigan surgical residencies (1222) and members of the Midwest Surgical Association (484). The response rate was 44%. Responses from 582 actively practicing surgeons were the sample used for analysis.

RESULTS

Thirty-two percent of actively practicing surgeons showed "high" levels of emotional exhaustion, 13% showed "high" levels of depersonalization, and 4% showed evidence for low personal accomplishment. Younger surgeons were more susceptible to burnout (r = -0.28, P <.01). Burnout was not related to caseload, practice setting, or percent of patients insured by a health maintenance organization. Important etiologic factors were a sense that work was "overwhelming" (r = 0.61, P <.01), a perceived imbalance between career, family, and personal growth (r = -0.56), P <.01), perceptions that career was unrewarding (r = -0.42, P <.01), and lack of autonomy or decision involvement (r = -0.39, P <.01). A strong association was noted between burnout elements and a desire to retire early (r = 0.50, P <.01).

CONCLUSIONS

Burnout is an important problem for actively practicing American surgeons. These data could be used to modify existing surgical training curricula or as an aid to surgical leadership when negotiating about the surgical work environment.

A clinical comparison of pneumatic compression devices: the basis for selection

PURPOSE

The five pneumatic compression devices (PCDs) that are marketed provide mechanical protection from deep venous thrombosis (DVT). They differ with respect to patterns of compression and the length of the sleeve. Evidence linking differences to clinical outcomes is lacking. Our purpose was twofold: to evaluate each of the marketed PCDs with respect to effectiveness, compliance, and patient and nursing satisfaction and to determine whether there is a clinical basis for the selection of one device over another.

METHODS

Each of the marketed devices was used exclusively for a 4-week period. Patients participated in an evaluation including venous duplex ultrasound scan, DVT risk assessment, and device evaluation. Vascular laboratory records were used to document DVT. Compliance was measured by meters installed on all pumps. A ranking matrix was stratified by compression pattern: rapid graduated sequential compression, graduated compression, and intermittent compression, and each device was rated by patients and nurses.

RESULTS

The PCDs were used in 1350 cases with a DVT rate of 3.5% ranging from 2% to 9.8% depending on the method of compression. Patients with DVT were older (58 vs 54 years), had better compliance (67% vs 50%), and had more compression days (11 vs 7.2). When thigh-length sleeves were used, a greater proportion of DVT occurred in the proximal segments (71%) as compared with the number of proximal DVT when the calf-length devices were used (52%; P =.21). Devices W, X, and Y had comparable rates of DVT, which were lower than those for V and Z. Compression device W, [correction] with calf and thigh sleeves, achieved the best overall ranking largely because of high scores for patient and nurse satisfaction.

CONCLUSION

Our data appear at odds with commonly held beliefs. We were unable to show a difference in DVT incidence based on the length of the device or the method of compression. Randomized studies are needed to confirm our findings and evaluate hypotheses derived from this study.

Diagnosis and endovascular treatment of iliocaval compression syndrome

PURPOSE

The purpose of this study was to evaluate the clinical presentation, diagnosis, and endovascular treatment of iliocaval compression syndrome (ICS).

PATIENTS AND METHODS

During a 3-year period, 18 patients (17 women, 1 man; mean age, 42 years) presented with clinical and imaging findings consistent with ICS. All patients were evaluated with venography and Doppler ultrasound (DUS), 13 of 18 with intravascular pressure measurements, 12 of 18 with intravascular ultrasound, 9 of 18 with air plethysmography (APG), and 4 of 18 with magnetic resonance venography. Seventeen patients were treated with endovascular stenting, one was treated with angioplasty alone, and six received adjunct thrombolysis.

RESULTS

Despite the presence of stenosis or occlusion in all cases, APG indicated no iliac vein obstruction (outflow fraction > or = 40%) in nine patients. DUS revealed acute (6) or chronic (7) unilateral iliofemoral deep venous thrombosis in 13 of 18 patients, whereas the results of five of 18 DUS studies were normal. Recanalization and stent placement (n = 17) or angioplasty (n = 1) was achieved in all patients. The average pressure gradient was 5.6 mm Hg preprocedure and 0.6 mm Hg postprocedure. The primary patency rate demonstrated with DUS (n = 17) and venography (n = 7) at 6 months was 89%. The primary patency rate at 12 months was 79%.

CONCLUSIONS

ICS often presents as sudden unilateral left lower extremity pain and swelling in young to middle-aged female patients after pregnancy, surgery, or a period of inactivity. Venography, intravascular ultrasound, and magnetic resonance venography demonstrate high sensitivity, whereas APG-outflow fraction demonstrates low sensitivity in the diagnosis of ICS. Endovascular stenting and angioplasty provide safe and effective early and intermediate-term treatment of symptomatic ICS.

Efficacy and durability of autogenous saphenous vein conduits for lower extremity arterial reconstructions in preadolescent children

OBJECTIVE

Limb length discrepancies (LLDs) in growing children may accompany extremity arterial occlusions. Revascularization with vein grafts has been questioned because of degenerative graft changes observed at other sites. This study was undertaken to define vein graft durability and efficacy in lower extremity revascularizations in preadolescent children.

STUDY DESIGN

Fourteen children (10 boys, 4 girls) with a mean age of 7.3 years (range, 2-11 years) who underwent 16 lower extremity revascularizations with greater saphenous vein grafts were subjected to follow-up with graft ultrasonography, ankle/brachial indices (ABIs) with and without exercise, and limb length determinations. A mean of 5.7 years elapsed between the onset of ischemia and operation. Arterial occlusions resulted from cardiac catheterizations (11), arteritis (1), dialysis cannulation (1), and penetrating trauma (1). Indications for operation included LLD (6), claudication (4), both LLD and claudication (3), markedly diminished ABIs with a potential for LLD (2), and a traumatic transection with hemorrhage (1). The reconstructions with 15 reversed and one in situ vein grafts included iliofemoral (11), femorofemoral (1), aortofemoral (1), femoropopliteal (1), popliteal-popliteal (1), and popliteal-posterior tibial (1) arterial bypass grafts.

RESULTS

Among patent grafts available for follow-up, 36% (5 of 14) remained unchanged, 50% (7 of 14) developed nonaneurysmal dilatation, and 14% (2 of 14) exhibited nonprogressive aneurysmal expansion. One graft became occluded, and one graft was lost to follow-up. Collectively, the grafts manifest an 11.2% expansion at an average of 10.7 years postoperatively. ABIs increased from 0.75 preoperatively to 0.97, at an average of 11.0 years postoperatively. LLDs were reduced from 1.66 to 1.24 cm, at an average of 11.4 years postoperatively.

CONCLUSION

Vein graft reconstructions of lower extremity arteries in preadolescent children are durable. They provide an efficacious means of restoring normal blood flow, and in 70% of children their preexisting LLDs were reduced.

How DRGs hurt academic health systems

BACKGROUND

Academic health centers continue their mission of clinical care, education, and research. This mission predisposes them to accept patients regardless of their individual clinical variation and financial risk. The purpose of this study is to assess the variation in costs and the attendant financial risk associated with these patients. In addition, we propose a new reimbursement methodology for academic health center high-end DRGs that better aligns financial risks.

STUDY DESIGN

We reviewed clinical and financial data from the University of Michigan data warehouse for FY1999 (n = 39,804). The diagnosis-related groups were classified by volume (group 1, low volume to group 4, high volume). The coefficient of variation for total cost per admission was then calculated for each DRG classification. A regression analysis was also performed to assess how costs in the first 3 days estimated total costs. A hybrid methodology to estimate costs was then determined and its accuracy benchmarked against actual Medicare and Blue Cross reimbursements.

RESULTS

Low-volume DRGs (< 75 annual admissions) had the highest coefficient of variation relative to each of the three other DRG classifications (moderate to high volume, groups 2, 3, and 4). The regression analysis accurately estimated costs (within 25% of actual costs) in 64.7% of patients with a length of stay > or = 4 days (n = 16,287). This regression fared well compared with actual FY 1999 DRG-based Medicare and Blue Cross reimbursements (n = 9,085 with length of stay > or = 4 days), which accurately reimbursed the University of Michigan Health System in only 43.9% of cases.

CONCLUSIONS

Academic health centers receive a disproportionate number of admissions to low-volume, high-variation DRGs. This clinical variation translates into financial risk. Traditional risk management strategies are difficult to use in health care settings. The application of our proposed reimbursement methodology better distributes risk between payers and providers, and reduces adverse selection and incentive problems ("moral hazard").

Outcomes after surgery for thoracic outlet syndrome

PURPOSE

This study determined whether there is an association between psychological and socioeconomic characteristics and the long-term outcome of operative treatment for patients with sensory neurogenic thoracic outlet syndrome (N-TOS).

METHODS

Clinical records, preoperative psychological testing results, and long-term follow-up questionnaire data were reviewed for consecutive patients who underwent surgery for N-TOS from 1990 to 1999. Multivariate logistic regression models were developed as a means of identifying independent risk factors for postoperative disability.

RESULTS

Operative decompression of the brachial plexus via a supraclavicular approach was performed for upper extremity pain and paresthesia with no mortality and minimal morbidity in 170 patients. After an average follow-up period of 47 months, 65% of patients reported improved symptoms, and 64% of patients were satisfied with their operative outcome. However, 35% of patients remained on medication, and 18% of patients were disabled. Preoperative factors associated with persistent disability include major depression (odds ratio [OR], 15.7; P =.02), not being married (OR, 7.9; P =.04), and having less than a high school education (OR, 8.1; P =.09).

CONCLUSION

Operative decompression was beneficial for most patients. Psychological and social factors, including depression, marital status, and education, are associated with self-reported disability. The impact of the preoperative treatment of depression on the outcome of TOS decompression should be studied prospectively.

Recurrent thromboembolism in patients with vena cava filters

BACKGROUND

Patients with venous thromboembolic disease are treated with anticoagulation or vena cava filter placement to prevent pulmonary embolism. A recent report suggested that filter placement may increase the risk of recurrent deep venous thrombosis (DVT) and prompted a review of our experience.

METHODS

Prospectively collected data on 2109 consecutive patients receiving filters were evaluated for recurrent thromboembolism, vena cava occlusion, or venous stasis ulceration. Outcomes were stratified and analyzed according to the use of anticoagulants at the time of insertion and at follow-up. Incidence rates were also compared with reports in the literature.

RESULTS

Of 1191 patients with DVT at filter placement, complete follow-up data at a mean of 9 years were available for 465. Recurrent DVT was found in 12% of the 241 patients who were given anticoagulants and 15% of the 224 who were not (P >.05). We also failed to find a significant association between the use of anticoagulation and the incidence of pulmonary embolism (2%), stasis ulceration (2%), and vena cava occlusion (0.0).

CONCLUSIONS

Recurrent DVT in patients with existing thromboembolic disease is not an unexpected event, which, in our experience, is not associated with anticoagulant or filter use. Anticoagulation should be used when possible to treat existing DVT to reduce thrombus progression and potentially to reduce subsequent complications but does not seem to reduce the rate of recurrent DVT. Rates of recurrent thromboembolism were consistently less than the 20% to 50% reported in the literature.

P-selectin antagonism causes dose-dependent venous thrombosis inhibition

Inhibition of P-selectin by antibody or selectin antagonist decreases inflammation and thrombosis. This study evaluates the dose-response relationship using a selectin receptor antagonist. Eight male baboons (Papio anubis) underwent inferior vena caval thrombosis using a 6 h balloon occlusion model. Three animals received 500 microg/kg P-selectin antagonist (rPSGL-Ig) and five 1 mg/kg rPSGL-Ig with or without a non-anticoagulant dose of Dalteparin. These animals were compared to our published results in this model with 4 saline controls and 8 animals that received 4 mg/kg rPSGL-Ig. A statistically significant dose-response relationship existed between rPSGL-Ig dose and thrombosis (p < 0.01), and between rPSGL-Ig dose and spontaneous recanalization (p<0.05). Inflammatory assessment revealed decreased gadolinium enhancement in all rPSGL-Ig groups compared to previously reported control, despite no significant differences in inflammatory cell extravasation. No dose of rPSGL-Ig caused anticoagulation. Selectin antagonism results in a dose-dependent decrease in thrombosis and increase in spontaneous recanalization.

Impact of chronic obstructive pulmonary disease on elective and emergency abdominal aortic aneurysm repair

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is associated with abdominal aortic aneurysm (AAA) expansion and is considered by some to be a relative contraindication to conventional aortic surgery. This study was undertaken to determine if COPD increases operative death, morbidity, intensive care unit (ICU) length of stay (LOS), and hospital LOS, after AAA repair.

METHODS

Data from national administrative records supplemented with laboratory data previously obtained for a system-wide study were analyzed in a retrospective review of 1053 consecutive patients (264 with and 789 without COPD) undergoing operation for intact or ruptured AAAs in Veterans Administration Hospitals from 1997 to 1998. Bivariate comparisons and multivariate regression were used to evaluate the impact of COPD on the number of days of ventilation, ICU LOS, total hospital LOS, and death, while controlling for other known risk factors, including acute myocardial infarction, renal failure, and age.

RESULTS

The mortality rate in elective aneurysm patients did not differ (P =.99) between patients with (3.7%) or without COPD (3.7%). However, elective AAA repair was associated with longer hospital LOS (14.4 vs 12.3 days, P =.01), longer ICU LOS (6.5 vs 5.4 days, P =.01), and a higher incidence of requiring 96 hours or more ventilation (6.9% vs 3.6%, P =.02) in patients with COPD. Ruptured AAA affected 4.9% of patients and was strongly associated with COPD (P =.02); however, COPD did not result in a statistically significant increase in death (P =.25).

CONCLUSIONS

Although COPD does not appear to increase operative death, it is associated with an increased risk of rupture. Elective repair of AAA should not be deferred in patients with COPD despite their higher LOSs and need for postoperative ventilation.

In vivo evaluation of vena caval filters: can function be linked to design characteristics?

PURPOSE

To compare the five vena caval filters marketed in the United States and one investigational vena caval filter and to determine whether there is an association between their design and their in vivo function.

METHODS

Four of each type of filter--Simon Nitinol (SN), Bird's Nest (BN), Vena Tech (VT), Greenfield stainless steel (PSGF), Greenfield titanium (TGF), and the investigational stent cone filter (NGF)--were studied for 60 days in 12 sheep. Radiographic and pathologic outcomes to be assessed included clot capture and resolution, vena caval penetration, position of the filter, thrombogenicity, and vessel wall reaction.

RESULTS

Filters differed with respect to the number of clot-trapping levels and the interdependence of the legs. All devices were successfully placed. Intentionally embolized clot was captured. One VT and two SN filters migrated in response to clot capture. Resolution of thrombus was variable, and related to the design of the device. Fibrin webbing was widely present with the VT, BN, and SN filters but limited in the others. The VT and NGF filters demonstrated the most stable filter base diameter.

CONCLUSIONS

The performance of vena caval filters differs with respect to clot resolution and mechanical stability. Interdependent filter limbs and single-stage conical capture sites appear to result in more favorable performance in in vivo studies.

The percutaneous greenfield filter: outcomes and practice patterns

OBJECTIVE

The percutaneous steel Greenfield filter (PSGF) is similar in appearance to the titanium Greenfield filter (TGF) but differs in the length and orientation of the attachment hooks and in the over-the-wire delivery system. Because these differences improve ease of insertion and attachment, they may affect patient outcomes and physician practices. The purpose of this study was to evaluate the performance of the PSGF relative to the TGF and to determine whether there had been a change in physician practices.

METHODS

The Michigan Filter Registry contains data for a prospective cohort of 2188 patients with Greenfield filters. Procedural and long-term outcomes for patients with a PSGF were abstracted. These events were compared with rates for Registry patients who had a TGF. Trends for indication for placement, delivery route, and filter location were also compared with published series.

RESULTS

Since 1995, 600 PSGFs have been placed in 599 patients. A 1-year mortality rate of 42% left 349 patients available for annual follow-up, and studies were completed for 231 (66%). Periprocedural events occurred in 2.5% of cases with associated morbidity in 1.5%. The rate of new pulmonary embolism was 2.6%, and vena caval patency was 98.3%. The combined rate of new venous thromboembolic events was 12.5%. Left-sided femoral vein placements increased to 20%, and the major indication for filter placement has become prophylaxis (46%).

CONCLUSIONS

The PSGF is similar to the TGF with respect to patient outcomes, and it provides decreased rates of asymmetry along with excellent fixation. The flexible carrier system has allowed more frequent access through the left femoral vein. The ease of use and favorable patient outcomes have resulted in more frequent placement for prophylactic indications.

Prophylactic vena caval filters in trauma: the rest of the story

OBJECTIVE

The purpose of this study was to describe outcomes for patients with trauma who had vena caval filters placed in the absence of venous thromboembolic disease (group P) and compare them with outcomes for patients with trauma who had filters placed after either deep venous thrombosis or pulmonary embolism (group T).

DESIGN

The study is a case series of consecutive patients who received vena caval filters after traumatic injury. Data were collected prospectively at the time of filter placement from reports of diagnostic studies obtained for clinical indications and during the annual follow-up examinations. Event rate findings are based on objective tests. Data were obtained from the Michigan Vena Cava Filter Registry.

RESULTS

Filters were placed in 385 patients with trauma; 249 of these filters were prophylactic (group P). Event rates were similar in the two groups. New pulmonary embolism was diagnosed in 1.5% of the patients in group P and 2% of the patients in group T. Caval occlusion rates were 3.5% for group P and 2.3% for group T. In all, 15.6% of the patients in group P had deep venous thrombosis or pulmonary embolism after placement. The frequencies of lower extremity swelling and use of support hose were higher in group T than in group P (43% vs 25% and 25% vs 3.5%, respectively; P <.005). Outcomes were comparable in the two groups with respect to mechanical stability of the filter.

CONCLUSIONS

The prophylactic indication for vena caval filter placement in patients with trauma is associated with a low incidence of adverse outcomes while providing protection from fatal pulmonary embolism. The current challenge is to limit the number of unnecessary placements through improved methods of risk stratification.

Filter complications and their management

Complications from the use of vena caval filters are rare but can occur at placement, during other procedures, or late in follow-up. Placement problems such as bleeding from the insertion site or embolism from thrombus manipulation are largely avoidable. Technical difficulties with introduction, positioning, or misplacement have been minimized by use of flexible carriers and guidewires. However, later insertion of guidewires without fluoroscopy for line changes can lead to problems of entrapment. Filter capture of emboli can result in further thrombus propagation at that site or in filter obstruction. Management of these events requires adequate visualization to determine whether to use lytic therapy or a second filter. Late complications include filter strut fracture in 0.05% of cases and filter penetration, of even rarer functional significance. Pain that can be attributed to the filter has been found only in a single case of pelvic misplacement. The limited consequences of mechanical changes in the filter argue strongly against unnecessary interventions, which frequently result in an increase in morbidity.

Length of stay has minimal impact on the cost of hospital admission

BACKGROUND

Hospital cost containment, cost reduction, and alternative care delivery systems continue to preoccupy health care providers, payers, employers, and policy makers throughout the United States. The universal metric for gauging the success of these efforts is hospital length of stay (LOS). Reducing the LOS purportedly yields large cost savings. The purpose of this study is to assess precisely how much hospitals save by shortening LOS.

STUDY DESIGN

We reviewed the cost-accounting records of all surviving patients (n = 12,365) discharged from our academic medical center during fiscal year 1998 with LOS of 4 days or more. Actual costs were identified through the University of Michigan cost-accounting system. Individual patient costs were broken out on a daily basis and then decomposed further into variable direct, fixed direct, and indirect categories. The population was analyzed by determining the incremental resource cost of the last full day of stay versus the total cost for the entire stay. The data were also stratified by LOS and by surgical costs. An analysis of all trauma patients was then performed on all patients discharged from the hospital's adult level I trauma center (n = 665). Costs were determined on specific days, including admission day, each ICU day, day of discharge from the ICU, and each of the last 2 days before the discharge day.

RESULTS

The incremental costs incurred by patients on their last full day of hospital stay were $420 per day on average, or just 2.4% of the $17,734 mean total cost of stay for all 12,365 patients. Mean end-of-stay costs represented only a slightly higher percentage of total costs when LOS was short (e.g., 6.8% for patients with LOS of 4 days). Even when the data were stratified to focus on patients without major operations, the $432 average last-day variable direct cost was only 3.4% of the $12,631 average total cost of care. A focus on the trauma center helps to explain this phenomenon. For our trauma center, variable direct costs accounted for 42% of the mean total cost per patient of $22,067. The remaining 58% was hospital overhead (fixed and indirect costs). The median variable direct cost on the first day of admission is $1,246, and the median variable direct cost on discharge is $304. Approximately 40% of the variable costs are incurred during the first 3 days of admission.

CONCLUSIONS

For most patients, the costs directly attributable to the last day of a hospital stay are an economically insignificant component of total costs. Reducing LOS by as much as 1 full day reduces the total cost of care on average by 3% or less. Going forward, physicians and administrators must deemphasize LOS and focus instead on process changes that better use capacity and alter care delivery during the early stages of admission, when resource consumption is most intense.

Academic health systems management: the rationale behind capitated contracts

OBJECTIVE

To determine why hospitals enter into "capitated" contracts, which often generate accounting losses. The authors' hypothesis is that hospitals coordinate contracts to keep beds full and that in principal, capitated contracts reflect sound capacity management.

SUMMARY BACKGROUND DATA

In high-overhead industries, different consumers pay different prices for similar services (e.g., full-fare vs. advanced-purchase plane tickets, full tuition vs. financial aid). Some consumers gain access by paying less than total cost. Hospitals, like other high-overhead business enterprises, must optimize the use of their capacity, amortizing overhead over as many patients as possible. This necessity for enhanced throughput forces hospitals and health systems to discount empty beds, sometimes to the point where they incur accounting losses serving some payors.

METHODS

The authors analyzed the cost accounting system at their university teaching hospital to compare hospital and intensive care unit (ICU) lengths of stay (LOS), variable direct costs (VDC), overhead of capitated patients, and reimbursement versus other payors for all hospital discharges (n = 29,036) in fiscal year 1998. The data were analyzed by diagnosis-related groups (DRGs), length of stay (LOS), insurance carrier, proximity to hospital, and discharge disposition. Patients were then distinguished across payor categories based on their resource utilization, proximity to the hospital, DRG, LOS, and discharge status.

RESULTS

The mean cost for capitated patients was $4,887, less than half of the mean cost of $10,394 for the entire hospitalized population. The mean capitated reimbursement was $928/day, exceeding the mean daily VDC of $616 but not the total cost of $1,445/day. Moreover, the mean total cost per patient day of treating a capitated patient was $400 less than the mean total cost per day for noncapitated patients. The hospital's capitated health maintenance organization (HMO) patients made up 16. 0% of the total admissions but only 9.4% of the total patient days. Both the mean LOS of 3.4 days and the mean ICU LOS of 0.3 days were significantly different from the overall values of 5.8 days and 1 day, respectively, for the noncapitated population. For patients classified with a DRG with complication who traveled from more than 60 miles away, the mean LOS was 10.7 days and the mean total cost was $21,658. This is in contrast to all patients who traveled greater than 60 miles, who had an LOS of 7.2 days and a mean total cost of $12,569.

CONCLUSION

The capitated payor directed the bulk of its subscribers to one hospital (other payors transferred their sicker patients). This was reflected in the capitated group's lower costs and LOS. This stable stream of relatively low-acuity patients enhanced capacity utilization. For capitated patients, the hospital still benefits by recovering the incremental cost (VDC) of treating these patients, and only a portion of the assigned overhead. Thus, in the short run, capitated patients provide a positive economic benefit. Other payors' higher-acuity patients arrive more randomly, place greater strains on capacity, and generate higher overhead costs. This results in differential reimbursement to cover this incremental overhead. Having a portfolio of contracts allows the hospital to optimize capacity both in terms of patient flows and acuity. One risk of operating near capacity is that capitated patients could displace other higher-paying patients.

Physician impact on the total cost of care

BACKGROUND AND OBJECTIVES

Physicians' efforts at cost containment focus on decreased resource utilization and reduced length of stay. Although these efforts appear to be appropriate, little data exist to gauge their success. As such, the goal of this study is to determine trauma service cost allocations and how this information can help physicians to contain costs.

MATERIALS AND METHODS

The authors analyzed the costs for 696 trauma admissions at a level I trauma center for fiscal year 1997. Data were obtained from the hospital costing system. Costs analyzed were variable direct, fixed direct, and Indirect costs. Together, the fixed and indirect costs are referred to as "hospital overhead." Total Cost equals variable direct plus fixed direct plus indirect costs.

RESULTS

The mean variable, fixed, and indirect costs per patient were $7,998, $3,534, and $11,086, respectively. Mean total cost per patient was $22,618.

CONCLUSION

The 35% variable direct cost represents the percentage of total cost that is typically under the immediate influence of physicians, in contrast to the 65% of total cost over which physicians have little control. Physicians must gain a better understanding of cost drivers and must participate in the operations and allocations of institutional fixed direct and indirect costs if the overall cost of care is to be reduced.

Venous thrombosis prophylaxis by inflammatory inhibition without anticoagulation therapy

OBJECTIVE

This study was performed to determine the effectiveness of recombinant P-selectin glycoprotein ligand Ig (rPSGL-Ig) pretreatment to decrease thrombosis and inflammation in experimental venous thrombosis. rPSGL-Ig, a unique mucin-like glycoprotein, has a high affinity for P-selectin.

METHODS

Twelve juvenile baboons underwent inferior vena cava (IVC) thrombosis with temporary 6-hour IVC balloon occlusion. Before balloon placement, the animals received rPSGL-Ig (4 mg/kg; n = 8) or saline solution for control (n = 4). The animals underwent evaluation with duplex ultrasound scan imaging, magnetic resonance venography (MRV), phlebography, coagulation profile, and tissue analysis at death for cytokines and vein wall leukocyte morphometrics. With the MRV results, thrombus development, thrombus resolution, and inflammation (gadolinium; square millimeters of enhancement) were assessed.

RESULTS

Each animal provided two time points for evaluation (days 2 and 6 after balloon occlusion). A significant decrease in IVC thrombosis between balloons was found in the rPSGL-Ig animals (1 of 16) versus the control animals (5 of 8; P <.01). The MRV results showed significantly less enhancement in the rPSGL-Ig animals at days 2 and 6 (P <.05). Spontaneous thrombus resolution (including balloon sites) was significantly greater from day 2 to day 6 in the rPSGL-Ig animals versus the control animals (23% vs 2%; P <.001), without pulmonary embolism. Lower interleukin-8, platelet factor IV, and monocyte chemotactic protein-1 levels were found in rPSGL-Ig vein walls without significant differences in vein wall leukocyte morphometrics. There were significantly lower D-dimer levels in the rPSGL-Ig-treated animals (P <.05), but there were no differences in measurements of coagulation. Adequate circulating rPSGL-Ig levels were documented.

CONCLUSION

Pretreatment with rPSGL-Ig results in: (1) a significant inhibition of thrombosis and vein wall inflammation; (2) a decrease in vein wall cytokine expression; and (3) a promotion of thrombus resolution. Inflammatory inhibition by rPSGL-Ig without anticoagulation therapy provides effective venous thrombosis prophylaxis in experimental venous thrombosis.

Paying a premium: how patient complexity affects costs and profit margins

OBJECTIVE AND BACKGROUND

Tertiary medical centers continue to be under extreme pressure to deliver high-complexity care, but paradoxically there is considerable pressure within these institutions to reduce their emphasis on tertiary care and refocus their efforts to develop a more community-like practice. The genesis of this pressure is the perceived profitability of routine surgical activity when compared with more complex care. The purpose of this study is to assess how the total cost and profit (loss) margin can vary for an entire trauma service. The authors also evaluate payments for specific trauma-related diagnostic-related groups (DRGs) and analyze how hospital margins were affected based on mortality outcome.

MATERIALS AND METHODS

The authors analyzed the actual cost of all trauma discharges (n = 692) at their level I trauma center for fiscal year 1997. Data were obtained from the trauma registry and the hospital cost accounting system. Total cost was defined as the sum of the variable, fixed, and indirect costs associated with each patient. Margin was defined as expected payments minus total cost. The entire population and all DRGs with 10 or more patients were stratified based on survival outcome, Injury Severity Score, insurance status, and length of stay. The mean total costs for survivors and nonsurvivors within these various categories and their margins were evaluated.

RESULTS

The profit margin on nonsurvivors was $5,898 greater than for survivors, even though the mean total cost for nonsurvivors was $28,821 greater. Within the fixed fee arrangement, approximately 44% of transfers had a negative margin. Both survivors and nonsurvivors become increasingly profitable out to 20 days and subsequently become unprofitable beyond 21 days, but nonsurvivors were more profitable than survivors.

CONCLUSIONS

There is a wide variance in both the costs and margins within trauma-related DRGs. The DRG payment system disproportionately reimburses providers for nonsurvivors, even though on average they are more costly. Because payers are likely to engage in portfolio management, patients can be transferred between hospitals based on the contractual relationship between the payer and the provider. This payment system potentially allows payers to act strategically, sending relatively low-cost patients to hospitals where they use fee-for-service reimbursement and high-cost patients to hospitals where their reimbursement is contractually capped. Although specific to the authors' trauma center and its payer mix, these data demonstrate the profitability of maintaining a level I trauma center and preserving the mission of delivering care to the severely injured.

Indirect versus direct measurement of brachial plexus depth

Supraclavicular nerve blocks are effective but may be complicated by pneumothorax. We hypothesized that, to avoid this complication, the depths of the brachial plexus and the lung could be estimated to guide needle placement. In 17 patients undergoing surgical relief of thoracic outlet syndrome, we designated a point on the skin midway between the clavicle and the trapezius muscle, in line with the most lateral point of the arterial pulsation in the supraclavicular fossa, to make preoperative height measurements relative to the clavicle and then intraoperative depth measurements of the plexus, artery, and pleura. The height of the reference point above the top of clavicle did not differ significantly from the depth of the plexus. The height of the reference point above the top, middle, and bottom of the clavicle differed significantly from the pleural depth (P = 0.0001, P = 0.0001, P = 0.0005, respectively). Patient weight correlated significantly with the depth of the plexus (P = 0.004, r2 = 0.45), artery (P = 0.0003, r2 = 0.42), and pleura (P = 0.0003, r2 = 0.58). We conclude that it is possible to accurately estimate the depth of the brachial plexus in the supraclavicular fossa.

IMPLICATIONS

In this study, we sought to minimize the risk of pneumothorax when approaching the brachial plexus through the supraclavicular fossa by developing a technique that could accurately estimate the depth of the nerves, within a range that is well clear of the lung.

Trauma services: a profit center?

BACKGROUND

Previous studies have demonstrated inadequate reimbursement for severely injured patients with a resultant negative economic impact for the trauma service and hospital. The purpose of this study was to assess the total cost of care for all injured patients discharged from the trauma service in fiscal year 1997, and to determine the proportion of costs for the most severely injured on total cost. In addition, we assessed the total service costs and the revenue for treatment of the most severely ill. The final result was the determination of the profit (loss) margin for the entire service.

STUDY DESIGN

All patients discharged from our Level I Trauma Center in fiscal year 1997 were included (n = 696). The population was then stratified into 2 subgroups using the Injury Severity Score (ISS). Patient grouping was facilitated by integration of the trauma registry with the hospital cost accounting system. The population was sub-divided into 2 distinct groups. Group A represented all patients with an ISS >15 (n = 192). Group B contained all patients with an ISS <15 (n = 504). Length of stay and mortality of each group was recorded. Cost of care was determined by the hospital cost accounting system TSI (Transition System Incorporated, Boston, MA), which is designed to generate cost center data on a cost per patient basis. Total costs were determined for the entire population and Groups A and B. The proportion of costs consumed by each group was then calculated. Reimbursement was determined by calculating expected payments for each patient. These calculations are based on previously agreed upon allowances from each insurer and are reconciled at the end of each fiscal year to ensure accuracy.

RESULTS

The average length of stay for the population and Groups A and B were 7.5, 9.8, and 6.7 days respectively. Mortality in each group was 9.7%, 19.3%, and 6%. Over 92% of the population sustained blunt mechanism injury and only 8% were penetrating. When controlled for length of stay, the profit margin for Group A is $1,242/day and for Group B is $519/day. Comparison of mean cost/patient between Group A and Group B was $35,727 versus $17,623, respectively.

CONCLUSION

Trauma centers can be profitable. Group A is responsible for 44% of the total service cost while accounting for only 28% of the discharges. Moreover, this group is responsible for 57% of the profit, and yields the greatest return. The ability to care for the sickest patients, while enormously costly, is essential to the economic viability of the trauma center and its future growth.

Low-dose low-molecular-weight heparin is anti-inflammatory during venous thrombosis

PURPOSE

Venous thrombosis results in a vein wall inflammatory response initiated by thrombus. Although anticoagulation with standard heparin (SH) and low-molecular-weight heparin (LMWH) is known to limit further thrombosis, their anti-inflammatory properties are poorly defined. The anti-inflammatory properties of these heparins were studied.

METHODS

Sprague-Dawley rats were divided into groups and underwent inferior vena caval (IVC) ligation just below the renal level producing IVC thrombosis. One hour before ligation, animals received subcutaneous SH or LMWH at either high or low dose; normal saline (NS) was used as control. Six hours after ligation, animals were killed, and the IVCs were analyzed for clot presence, vein wall morphometrics, and vein wall permeability (VP) to define injury.

RESULTS

Animals in both low-dose groups had no measurable anticoagulation, whereas those in both high-dose groups were adequately anticoagulated. There were statistically less IVC neutrophils for all groups compared with the control group, with low-dose LMWH showing the least cells (low-dose LMWH, 16 +/- 3; high-dose LMWH, 37 +/- 10; low-dose SH, 37 +/- 6; high-dose SH, 32 +/- 9; NS control, 63 +/- 2). Similar results were noted for total inflammatory cells. The lowest VP was noted for low-dose LMWH.

CONCLUSION

Although both SH and LMWH inhibited vein wall neutrophils and total inflammatory cells, low-dose LMWH was most effective limiting neutrophil extravasation and was the only intervention to decrease VP below control levels. This occurred without preventing thrombus formation or causing a state of anticoagulation. Low-dose LMWH possesses anti-inflammatory properties distinct from its anticoagulant properties.

Suprarenal filter placement

PURPOSE

This study was undertaken to determine the clinical outcomes for patients with Greenfield filters placed in the suprarenal (SR) inferior vena cava (IVC).

METHODS

We collected data prospectively from annual follow-up evaluations of patients with filters. Patients underwent venous color-flow duplex examinations of the IVC and lower extremities, abdominal radiographs, and physical assessment. The outcomes for those patients with filters in the SR IVC were compared with the outcomes previously reported and with the outcomes for patients with filters in the infrarenal cava.

RESULTS

SR placement accounted for 7.6% (148/1932) of all filter placements. Follow-up data were available for 73 placements, or 49%. No cases of renal dysfunction were related to filter placement. The rate of recurrent pulmonary embolism (PE) was 8%, and the rate of long-term caval occlusion was 2.7%. These rates did not differ statistically from the rates for patients with infrarenal filters (P > .05). Male patients tended to be older by 15 years, to have more recurrent PE, and to experience more filter migration (6 vs 2 mm). Failure of SR filters to prevent PE was associated statistically with the primary indication for placement. Recurrent PE was the indication in 5 of 6 patients who sustained PE after SR filter placement (P = .007). Filter limb fracture was seen only with the stainless-steel Greenfield filter.

CONCLUSION

Greenfield filters placed above the renal vein provide protection from PE with a minimal risk of occlusion. Twenty-five years of experience with Greenfield filters shows that they are safe and effective both in young female patients of child-bearing potential and in all patients with appropriate indications for SR placement.

IL-10 regulates thrombus-induced vein wall inflammation and thrombosis

Vein wall inflammation associated with venous thrombosis is mediated by an imbalance in proinflammatory as compared with antiinflammatory molecules. We hypothesize that IL-10 is an important antiinflammatory cytokine that influences vein wall inflammation and thrombus propagation during venous thrombosis. To test this hypothesis a model of inferior vena caval thrombosis was used. Studies were performed at sacrifice 2 days after thrombus induction and included leukocyte morphometrics, myeloperoxidase activity, vein wall permeability, thrombus weight, and IL-10 ELISA analysis from the vein wall. IL-10 was elevated in the vein wall during venous thrombosis. Neutralization of IL-10 increased inflammation, while supplementation with rIL-10 demonstrated a dose- and time-dependent decrease in inflammation. Interestingly, a low 2.5-microg rIL-10 dose given at time of initiation of thrombosis most significantly decreased inflammation. Thrombus weight was importantly diminished by reconstitution of IL-10. These studies support an important role for IL-10 in the regulation of thrombus-associated inflammation and thrombosis and suggest that IL-10 could be used as a therapeutic agent in the treatment of venous thrombosis.

Assessment of apparent vena caval penetration by the Greenfield filter

PURPOSE

To examine and elucidate the mechanisms for apparent "penetration" by Greenfield vena caval filters.

METHODS

Two filters were placed in the inferior venae cavae (IVC) of four immature sheep and followed with cavography for 1 year. Two animals underwent computed tomography (CT) and laparoscopic examination. At necropsy, the vena cava and adjacent structures of all four animals were examined grossly and histologically.

RESULTS

Based upon cavography and CT imaging, all filters appeared to penetrate the vena cava at 12 months. However, at laparoscopy, no hooks or limbs were exposed, and the pericaval tissues remained intact; each hook or limb was within the adventitia or encapsulated in scar tissue. Histology of the tissue at the hook sites revealed remodeling of the intimal surface of the IVC and thinning of the adventitia.

CONCLUSIONS

Based upon these data, we hypothesize that the vena cava gradually adapts by medial and adventitial thinning and myointimal remodeling to the radial force exerted by a filter. This process allows increase in the filter base diameter while maintaining the integrity of the cava and protecting adjacent structures.

GABAA receptor pharmacology and subtype mRNA expression in human neuronal NT2-N cells

Human NT2 teratocarcinoma cells differentiate into neuron-like NT2-N cells when treated with retinoic acid. GABA evoked concentration-dependent whole-cell currents in NT2-N cells with an EC50 of 21.8 microM and a Hill slope of 1.2. GABAA receptor (GABAR) currents reversed at ECl- and did not display voltage-dependent rectification. GABAR single channels opened in bursts to a 23 pS main conductance level and a 19 pS subconductance level, with infrequent openings to a 27 pS conductance level. Kinetic properties of the main conductance level were similar to other native and recombinant GABAR channels. Diazepam and zolpidem enhanced GABAR currents with moderate affinity, whereas methyl-6, 7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate inhibited GABAR currents. Loreclezole enhanced GABAR currents with high affinity, but furosemide antagonized GABAR currents with low affinity. The neurosteroids alphaxalone and pregnenolone sulfate appropriately modulated GABAR currents. Zinc blocked GABAR currents with low affinity, but lanthanum did not significantly alter NT2-N GABAR currents. Reverse transcription PCR (RT-PCR) performed on RNA from NT2-N cells clearly detected transcripts encoding human alpha2, alpha3, alpha5, beta3, gamma3, and pi subtypes. The combined pharmacological and RT-PCR results are most consistent with a single or predominant GABAR isoform composed of an alpha2 and/or alpha3 subtype combined with the beta3 and gamma3 subtypes. The data do not rule out receptors containing combinations of alpha2 and/or alpha3 subtypes with the alpha5 subtype or receptors with both beta1 and beta3 subtypes. The presence or absence or the pi subunit in functionally expressed receptors could not be determined.

Trauma service cost: the real story

OBJECTIVE

The objective was to define and characterize the costs associated with trauma care at a level I trauma center. Once the costs were identified, attending physician-led teams were designed to reduce costs within each cost center.

SUMMARY BACKGROUND DATA

The location and magnitude of the costs on a trauma service remain largely unknown. Focused cost-containment strategies remain difficult to implement because the expected return on these interventions is unknown.

METHODS

Cost center data were reviewed for the 40 major DRGs admitted for the first 6 months of the fiscal years 1996 and 1997. Data were obtained from the hospital finance department using the Transition Systems Inc. accounting system. We focused on variable direct costs, those that vary with patient volume (e.g., staff nursing expense and medical/surgical supplies). To address issues of inflation, pay raises, and changing costs, a proxy value was created for 1996 and costs were held constant for the 1997 calculation. The major services that constitute cost centers identified in the system were nursing, surgical, pharmacy, laboratory, radiology, and emergency services. Attendings were assigned to develop and oversee customized cost-reduction modalities specific to each cost center. The cost-reduction modalities used to achieve significant savings were as follows: nursing, case management approach focusing on early discharge; surgical, meeting with operating room (OR) purchasing to modify expensive behavior patterns; pharmacy, integrating clinical pharmacist with direct attending support; laboratory, enforcing protocol for lab draws; radiology, increasing the use of emergency room ultrasound and accepting outside x-rays; and emergency services, 24-hour in-house attending staff to reduce emergency room time. The surgical and emergency services cost centers predominately generate costs by the length of time care is delivered in that area.

RESULTS

For each period, data from 363 patients were compared. Mean length of stay decreased between the study periods from 8.72 to 7.06 days, while the average injury severity score was unchanged. Together, these cost centers constituted 87.4% of the total cost of care delivered. Significant cost reduction was achieved in all six variable cost centers: nursing (24%), surgical (5%), pharmacy (57%), laboratory (27), radiology (7%), and emergency (36). The mean cost per case was reduced by 25%.

CONCLUSIONS

Identification of the true cost centers and directed attending surgeon involvement are essential to the development and implementation of a successful cost-reduction process.

Endovascular methods for caval interruption

Current methods for vena caval interruption have developed in parallel with advances in endovascular techniques. Six filters are currently approved by the FDA for marketing: three Greenfield filters, the Venatech, Simon Nitinol, and Bird's Nest filter. These are compared with respect to design and function. In addition, the utility and limitations of temporary filters are addressed. The use of endovascular techniques to correct misplacement of a filter, to free entangled guidewires, or to adjust filter limb distribution is described.