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Timothy G Buchman

Publications and source records attributed to Timothy G Buchman.

At least 37 records · Page 2Linked to original sources
PubMed2004

Nonlinear dynamics, complex systems, and the pathobiology of critical illness.

PURPOSE OF REVIEW: The review considers problems in critical illness and critical care in the context of complex systems science. Normal physiology is characterized by nonlinear dynamics, and it appears that the pathophysiology of critical illness alters those dynamics. RECENT FINDINGS: Recent evidence confirms and extends the observation that the rich variability that characterizes normal physiology "decomplexifies" with critical illness. Experimental data in animals and now in humans suggests that physiologic support that mimics normal variability may reduce the severity and/or duration of the illness. SUMMARY: Physiologic dynamics in health and in critical illness appear to reflect complex, interconnected systems biology. Alterations in illness and during recovery may provide important clues to the underlying structure of the system. With knowledge of the structure, therapy could be better focused toward supporting both function and dynamics, offering hope for improved outcomes.

Critical Care↗
PubMed2004

Antibiotics improve survival in sepsis independent of injury severity but do not change mortality in mice with markedly elevated interleukin 6 levels.

Genetically identical mice have a heterogeneous response to antibiotic therapy in sepsis, with only a subset deriving therapeutic benefit. We sought to determine whether the severity of a septic insult correlates with the survival benefit conferred by antibiotics. We also sought to determine whether antibiotics given 12 h after injury alter survival in animals predicted to die based upon high interleukin (IL)-6 levels drawn 6 h earlier. Adult male ND4 mice (n = 363) were subjected to double-puncture cecal ligation and puncture (CLP) with a 19-, 21-, or 23-gauge needle. Animals were randomized to receive imipenem or 0.9% NaCl every 12 h after CLP for 5 days. Ten-day survival was 16%, 26%, and 52%, respectively, for untreated animals. Antibiotics decreased the absolute risk of death 17% to 23% regardless of injury severity. In a separate cohort, mice (n = 37) were subjected to single or double-puncture CLP with a 21-gauge needle. IL-6 levels were assayed 6 h postoperatively and mice were followed for survival. Levels greater than 14,000 pg/mL were identified as predicting a 100% mortality (7/7 animals dead). A third set of mice (n = 94) then underwent double-puncture CLP with either 21-, 23-, or 25-gauge needle and had IL-6 levels measured in a similar fashion. Animals were randomized to receive imipenem or 0.9% NaCl beginning 12 h postoperatively (6 h after IL-6 levels were drawn) and continued for 5 days or until death. Although antibiotics decreased mortality overall, all animals with IL-6 levels greater than 14,000 pg/mL (n = 13) died, regardless of whether they received antibiotics or the gauge of needle used. These results indicate that antibiotics improve outcome in murine sepsis, regardless of injury severity. Furthermore, there is a threshold IL-6 level that can be identified 6 h after sepsis above which animals are destined to die, and antibiotic treatment does not alter their outcome.

Animals↗
PubMed2004

Sequence makes a difference: paradoxical effects of stress in vivo.

In vitro studies have shown that induction of heat shock before an inflammatory stimulus is cytoprotective, whereas induction of heat shock after an inflammatory stimulus can lead to apoptosis (the "heat shock paradox"). We sought to determine whether induction of the heat shock response in vivo caused similar, order-dependent effects on survival, and if so, by what mechanism. ND4 and C57BL/6 mice were used to calibrate the response to hyperthermia at 41.5 degrees C via induction of inducible heat shock protein 70. Sequences of heat shock and septic stresses were studied in murine models of hyperthermia (41.5 degrees C for 20 min) and cecal ligation and puncture (CLP), respectively. Previous heat shock to 41.5 degrees C did not protect CLP mice when compared with control CLP animals heated to 37 degrees C, but heat shock increased mortality when activated after CLP compared with controls. This effect of heat shock on CLP mortality was strain independent, and did not involve alterations in CLP-induced thymus, spleen, or intestinal apoptosis. We conclude that the heat shock paradox can occur in vitro and in vivo, and that the negative effects of heat shock on survival after CLP appeared to be strain independent. Furthermore, the stress of general anesthesia and warming also altered CLP mortality unexpectedly. The cellular mechanisms responsible for these "stressor" paradoxes in vivo are not known, but do not involve altered sepsis-induced apoptosis.

Animals↗
PubMed2004

Age disproportionately increases sepsis-induced apoptosis in the spleen and gut epithelium.

Both aging and sepsis independently increase splenic and gut epithelial apoptosis. Sepsis-induced apoptosis in either cell type is also associated with increased mortality in young mice. We sought to determine whether age alters sepsis-induced splenic and gut epithelial cell death. Young (2 months) and aged (22 months) male ND4 mice were subjected to either single-puncture cecal ligation and puncture (CLP) with a 23-gauge needle or sham laparotomy. Apoptosis was assessed 24 hours later in the spleen and gut epithelium by active caspase 3 and hematoxylin and eosin staining. Aged septic mice had increased splenic apoptosis compared with either young septic animals or aged sham animals (15 vs. 7 vs. 5 apoptotic cells/high-powered field, P < 0.05). Similarly, aged septic animals had an elevation in gut epithelial cell death compared with either young septic or aged sham mice (33 vs. 16 vs. 6 apoptotic cells/100 contiguous crypts, P < 0.05). Elevated intestinal cell death was not associated with changes in either gut proliferation or cell division. To verify that the increase in splenic apoptosis seen in septic aged animals was not strain specific, double-puncture CLP with a 25-gauge needle or sham laparotomy was performed on young (4 months) or aged (24 months) C57BL/6 male mice. Similar to results seen in outbred animals, aged septic animals in this inbred strain had increased splenic apoptosis compared with either young septic animals or aged sham animals (23 vs. 7 vs. 4 apoptotic cells/ high powered field, P < 0.05). These results indicate that although infection and aging each independently cause an increase in splenic and gut epithelial apoptosis, their combination leads to a disproportionate increase in cell death in these rapidly dividing cell populations,and potentially plays a role in the marked increase in mortality seen with aging in sepsis.

Aging↗
PubMed2003

National estimates of hospitalization charges for the acute care of traumatic brain injuries.

PRIMARY OBJECTIVE: To estimate hospitalization charges for the acute care of traumatic brain injuries (TBIs)in the US and to identify factors associated with increased charges. RESEARCH DESIGN: Population-based descriptive study. METHODS: The 1996 National Inpatient Sample was used, which contains all-payer data on hospital inpatient stays from 906 hospitals in 19 states. Multivariate linear regression with the log (mean + 1)charges as the dependent variable was used to identify factors associated with increased charges. RESULTS: An estimated 254,500 TBIs required hospitalization in 1996 in the US, with 5.4 billion US dollars charged to treat these injuries during acute hospitalization. Patient age (up to 34 years), increasing severity of injury and urban teaching hospitals were associated with higher mean charges in multi-variate analysis. CONCLUSIONS: Based on hospitalization rates, mean and total charges, segments of the population were identified that are likely candidates for injury prevention interventions.

Adolescent↗
PubMed2003

Effects of age on mortality and antibiotic efficacy in cecal ligation and puncture.

The incidence and mortality of sepsis increase with age, consequently, 80% of the clinical mortality from sepsis occurs in patients over age 65. Despite this aged clinical population, most research models of sepsis use 6- to 16-week-old mice as patient surrogates. This age range of mice corresponds to human ages 10 to 17 years. To assess the influence of age on rodent CLP and on antibiotic therapy, we studied young (4 month), mature (12 month), and aged (24 month) mice. Male C57BL/6 mice (n = 27-30 in each age group) were subjected to cecal ligation and puncture (CLP), two punctures with a 25-gauge needle. Mice were observed untreated for 10 days. Young mice had 20% mortality, mature mice had 70% mortality (P = 0.0013 vs. young), and aged mice had 75% mortality (P = 0.0001 vs. young). To assess the effects of age on antibiotic therapy, mice were subjected to CLP as above (n = 38-40 in each age group). Mice were then randomized to treatment with intraperitoneal injections of ceftriaxone and metronidazole or normal saline. Therapy was initiated 12 h after CLP, and injections were repeated every 12 h for 7 days. Young mice saw a 56% decrease in mortality from CLP with antibiotic therapy (P = 0.001), and mature mice had a 30% decrease in mortality (P = 0.06). Aged mice saw no benefit from antibiotic therapy. We also compared plasma cytokine levels between young and aged mice after CLP. When compared with young mice, aged mice had higher levels of IL-6 and TNF-alpha 24 h after CLP. However, high IL-6 was predictive of mortality at any age. Mice appear to have age-dependent responses to intra-abdominal sepsis and to appropriate therapy.

Age Factors↗
PubMed2003

Sepsis from Pseudomonas aeruginosa pneumonia decreases intestinal proliferation and induces gut epithelial cell cycle arrest.

OBJECTIVES: To evaluate whether the up-regulation in sepsis-induced gut epithelial apoptosis is balanced by an increase in intestinal proliferation and to assess mechanisms affecting the gut's regenerative response to overwhelming infection. DESIGN: Prospective, randomized, controlled study. SETTING: Animal laboratory in a university medical center. INTERVENTIONS: Mice were subjected to intratracheal injection of Pseudomonas aeruginosa and killed between 1.5 and 24 hrs after induction of pneumonia-induced sepsis to assess for gut epithelial proliferation and cell division and for apoptosis. Animals were compared with sham-operation controls, septic transgenic mice that overexpress Bcl-2 throughout their small intestinal epithelium, and septic p53-/- mice. MEASUREMENTS AND MAIN RESULTS: Proliferation and cell division were assessed by measuring S-phase and M-phase cells in intestinal crypts. The number of S-phase cells showed a progressive decline at all time points measured, with a 5-fold decrease in proliferation between control animals and septic mice 24 hrs after intratracheal injection of pathogenic bacteria (p <.0001). In contrast, cells in M-phase remained constant for the first 12 hrs after the onset of sepsis, but increased nearly 50% at 24 hrs after instillation of P. aeruginosa (p <.005). Both the decrease in S-phase cells and the increase in M-phase cells were partially suppressible in Bcl-2 overexpressors, but cellular proliferation and division were similar between septic p53-/- and p53+/+ mice. Crypt apoptosis was increased at all time points, with maximal death occurring between 12 and 24 hrs. CONCLUSIONS: Sepsis from P. aeruginosa pneumonia induces a p53-independent decrease in gut epithelial proliferation. Despite an increase in sepsis-induced intestinal apoptosis, there is no compensatory increase in intestinal epithelial proliferation, and there is evidence of a cell cycle block with an accumulation of cells in M-phase. Decreasing gut apoptosis by overexpression of Bcl-2 is associated with a partial reversal of the effect of sepsis on the cell cycle.

Animals↗
PubMed2003

Surgeons, intensivists, and the covenant of care: administrative models and values affecting care at the end of life.

CONTEXT: End-of-life care remains a challenging and complex activity in critical care units. There is little information concerning the influence of administrative models of care delivery on end-of-life care. OBJECTIVE: To compare and contrast end-of-life care delivery in intensive care units using "semiclosed," "open," and "closed" administrative models. DESIGN: Ethnographic study of three critical care units. SETTING: University hospitals in the United States and New Zealand. SUBJECTS: Approximately 600 physicians, nurses, allied health personnel, patients, family members, and friends. MEASUREMENTS AND MAIN RESULTS: Ethnographic observations were made at three sites for 75, 3, and 10 wks, respectively. Eighty end-of-life care episodes were observed. The interactions among care personnel and families varied according to the administrative model, depending on whether surgeons or intensivists had primary patient responsibility. This led to differential timing on the shift from "cure" to "comfort," and differential decision-making power for families. CONCLUSIONS: End-of-life care varies according to the administrative model. When surgeons have primary responsibility for the patient, the most important goal is defeating death. When intensivists have sole patient responsibility, scarce resources are considered and quality of life is a significant variable. Discussions about improving the way end-of-life decisions are carried out in intensive care units rarely consider the administrative models and personal, professional, and national values affecting such decisions. To improve care at the end of life, we must critically examine these features.

Attitude of Health Personnel↗
PubMed2003

Antibiotics improve survival and alter the inflammatory profile in a murine model of sepsis from Pseudomonas aeruginosa pneumonia.

Differing antibiotic regimens can influence both survival and the inflammatory state in sepsis. We investigated whether the addition and/or type of antimicrobial agent could effect mortality in a murine model of Pseudomonas aeruginosa pneumonia-induced sepsis and if antibiotics altered systemic levels of cytokines. FVB/N mice were subjected to intratracheal injection of pathogenic bacteria and were given gentamicin, imipenem, or 0.9% NaCl 2 h after surgery, which continued every 12 h for a total of six doses. Survival at 7 days (n = 24 in each group) was 100% for mice given gentamicin, 88% for mice given imipenem, and 8% for sham mice treated with 0.9% NaCl (P < 0.0001). Systemic interleukin (IL) 6 levels were assayed 6 h postoperatively on all mice to see if they were predictive of outcome. Plasma IL-6 levels above 3,600 pg/mL were associated with a 100% mortality, levels under 1,200 pg/mL were associated with a 100% survival, and levels between 1,200 and 3,600 pg/mL had no utility in predicting mortality. In a separate experiment, mice were sacrificed at 3, 6, 12 or 24 h after instillation of P. aeruginosa and were assayed for levels of TNF-alpha, IL-6, IL-10, and IL-12. Significant alterations in the proinflammatory cytokines TNF-alpha and IL-6 were present at all time points except 3 h between mice treated with antibiotics and sham controls. In contrast, statistically significant differences in the anti-inflammatory cytokine IL-10 were present between the groups only at 6 h, and levels of IL-12 were similar at all time points. These results indicate that both gentamicin and imipenem increase survival at least 10-fold in a model of pneumonia-induced monomicrobial sepsis, and this is predominantly associated with a down-regulation of proinflammatory cytokines.

Animals↗
PubMed2003

Iron overload before cecal ligation and puncture increases mortality.

Iron metabolism is dysregulated in critically ill patients. A mouse model of dysregulated iron metabolism was used to examine the consequence of iron loading upon sepsis. Mice deleted in the hfe gene (hfe-/-) abnormally accumulate iron in tissue; defects in the human hfe gene are clinically expressed as hemochromatosis. Hfe-/- mice and wild-type counterparts were randomized to receive either high- or low-iron diets for 2 weeks. After iron loading, mice were subjected to cecal ligation and puncture (CLP), a clinically relevant animal model of intra-abdominal sepsis. A preliminary (but underpowered) study suggested that iron-loaded hfe-/- mice had increased mortality as compared with hfe-/- mice fed a low-iron diet. There was no difference between wild-type and hfe-/- mice fed a low-iron diet or between wild-type mice fed hihg- and low-iron diets. A subsequent, appropriately powered study showed that iron-loaded hfe-/- mice had significantly higher mortality from intra-abdominal sepsis than hfe-/- mice fed a low-iron diet. Iron loading was confirmed through chemical assay of iron concentration in hepatic tissue. Animals with dysregulated iron handling, loaded with iron and subjected to CLP, had double the mortality of animals with normal iron levels. Critical care patients often have altered iron metabolism. In clinical practice, critically ill patients may receive iron through direct administration and the transfusion of blood products. Iron therapy may adversely affect the clinical outcome from sepsis.

Administration, Oral↗
PubMed2003

A meta-analysis of controlled trials of anticoagulant therapies in patients with sepsis.

Although coagulation abnormalities may partly underlie the physiologic derangements of the sepsis syndrome, anticoagulant therapies have produced mixed results on survival in clinical studies. We hypothesized that a meta-analysis of clinical trials of anticoagulants in sepsis may provide insight as to the therapeutic utility of targeting the clotting cascade in this syndrome. We searched electronic databases and reviewed bibliographies of pertinent articles to identify controlled clinical studies in which anticoagulants had been administered as adjunctive therapy to patients with sepsis. After establishing statistical homogeneity, odds ratios (OR; with 95% confidence intervals [CI]) for effect of these agents on mortality and bleeding complications were determined using Mantel-Haenszel methodology. Potential for publication bias was assessed by the use of a statistical test of funnel plot asymmetry. Weighted linear regression was performed to examine the effect of control group mortality rate on treatment efficacy. We identified 11 studies that satisfied our inclusion criteria. Collectively, these studies enrolled 4690 patients (range of 29-2314) and examined three agents: antithrombin III (2659 patients), tissue factor pathway inhibitor (210 patients), and activated protein C (1821 patients). After establishing statistical homogeneity (P > 0.10, chi-square), we found that the OR (with 95% CI) for effect on mortality for these agents, relative to control treatment, was 0.8692 (0.7519-1.006). Weighted linear regression analysis was consistent with a control group mortality dependent effect for these agents (P = 0.02). Only five of the studies reported bleeding complications. Pooling the results of these five studies (4376 patients) resulted in an OR (with 95% CI) of 1.70 (1.40-2.07) relative to control treatment for bleeding risk. Anticoagulants as adjuvant therapy do not appear to improve outcome in sepsis and are associated with a significant risk of bleeding complications. To the extent that their treatment effect is dependent upon disease severity, the safety and efficacy of these agents may be enhanced by refinement in techniques of clinical stratification.

Anticoagulants↗
PubMed2003

Bcl-2 inhibits gut epithelial apoptosis induced by acute lung injury in mice but has no effect on survival.

Gut epithelial apoptosis is increased in human studies and animal models of noninfectious inflammation and sepsis. Elevated intestinal cell death appears to be physiologically significant in sepsis. Previous studies demonstrate that overexpression of the antiapoptotic protein Bcl-2 in the gut epithelium of transgenic mice is associated with improved survival from Pseudomonas aeruginosa pneumonia and cecal ligation and puncture. The functional significance of elevated gut apoptosis in noninfectious inflammation has not been examined. We hypothesized that intestinal apoptosis would be detrimental to survival in noninfectious critical illness. To address this issue, acute lung injury (ALI) was induced with intratracheal injection of lipopolysaccharide (LPS, 800 microg) in wild-type (WT) FVB/N mice and transgenic mice that overexpress Bcl-2 in their intestinal epithelium. Guts were harvested at 12, 24, 48, and 72 h and assessed for apoptosis by both hematoxylin and eosin and active caspase-3 staining in 100 contiguous crypts. ALI increased gut epithelial apoptosis 12 h after LPS instillation compared with shams (P < 0.01), whereas overexpression of Bcl-2 decreased intestinal apoptosis compared with WT animals with ALI when assayed by active caspase-3 (P < 0.05). Plasma levels of tumor necrosis factor alpha, interleukin (IL)-6, and IL-10 were similar between WT and transgenic animals with ALI, both of which had elevated IL-10 levels at 12 h and elevated IL-6 levels at 24 h compared with sham animals. In a separate experiment, transgenic and WT animals with ALI were followed for mortality to determine whether gut overexpression of Bcl-2 conferred a survival advantage. Survival at 10 days was 73% in WT animals (n = 33) and 65% in Bcl-2 animals (n = 23, P = ns). These results indicate that while gut epithelial apoptosis is elevated in multiple models of critical illness, prevention of intestinal cell death by overexpression of Bcl-2 is associated with a disparate survival effect between sepsis and noninfectious inflammation.

Administration, Inhalation↗
PubMed2003

Surgeons, intensivists, and the covenant of care: administrative models and values affecting care at the end of life--Updated.

CONTEXT: End-of-life care remains a challenging and complex activity in critical care units. There is little information concerning the influence of administrative models of care delivery on end-of-life care. OBJECTIVE: To compare and contrast end-of-life care delivery in intensive care units using "semiclosed," "open," and "closed" administrative models. DESIGN: Ethnographic study of three critical care units. SETTING: University hospitals in the United States and New Zealand. SUBJECTS: Approximately 600 physicians, nurses, allied health personnel, patients, family members, and friends. MEASUREMENTS AND MAIN RESULTS: Ethnographic observations were made at three sites for 75, 3, and 10 wks, respectively. Eighty end-of-life care episodes were observed. The interactions among care personnel and families varied according to the administrative model, depending on whether surgeons or intensivists had primary patient responsibility. This led to differential timing on the shift from "cure" to "comfort," and differential decision-making power for families. CONCLUSIONS: End-of-life care varies according to the administrative model. When surgeons have primary responsibility for the patient, the most important goal is defeating death. When intensivists have sole patient responsibility, scarce resources are considered and quality of life is a significant variable. Discussions about improving the way end-of-life decisions are carried out in intensive care units rarely consider the administrative models and personal, professional, and national values affecting such decisions. To improve care at the end of life, we must critically examine these features.

Anthropology, Cultural↗
PubMed2002

The community of the self.

Good health, which reflects the harmonious integration of molecules, cells, tissues and organs, is dynamically stable: when displaced by disease, compensation and correction are common, even without medical care. Physiology and computational biology now suggest that healthy dynamic stability arises through the combination of specific feedback mechanisms and spontaneous properties of interconnected networks. Today's physicians are already testing to 'see if the network is right'; tomorrow's physicians may well use therapies to 'make the network right'.

Feedback, Physiological↗
PubMed2002

High-frequency oscillatory ventilation for acute respiratory distress syndrome in adults: a randomized, controlled trial.

Observational studies of high-frequency oscillatory ventilation in adults with the acute respiratory distress syndrome have demonstrated improvements in oxygenation. We designed a multicenter, randomized, controlled trial comparing the safety and effectiveness of high-frequency oscillatory ventilation with conventional ventilation in adults with acute respiratory distress syndrome; 148 adults with acute respiratory distress syndrome (Pa(O2)/fraction of inspired oxygen <or= 200 mm Hg on 10 or more cm H2O positive end-expiratory pressure) were randomized to high-frequency oscillatory ventilation (n = 75) or conventional ventilation (n = 73). Applied mean airway pressure was significantly higher in the high-frequency oscillation group compared with the conventional ventilation group throughout the first 72 hours (p = 0.0001). The high-frequency oscillation group showed early (less than 16 hours) improvement in Pa(O2)/fraction of inspired oxygen compared with the conventional ventilation group (p = 0.008); however, this difference did not persist beyond 24 hours. Oxygenation index decreased similarly over the first 72 hours in both groups. Thirty-day mortality was 37% in the high-frequency oscillation group and was 52% in the conventional ventilation group (p = 0.102). The percentage of patients alive without mechanical ventilation at Day 30 was 36% and 31% in the high-frequency oscillation and conventional ventilation groups, respectively (p = 0.686). There were no significant differences in hemodynamic variables, oxygenation failure, ventilation failure, barotraumas, or mucus plugging between treatment groups. We conclude that high-frequency oscillation is a safe and effective mode of ventilation for the treatment of acute respiratory distress syndrome in adults.

APACHE↗