Interobserver variability in data collection of the APACHE II score in teaching and community hospitals

OBJECTIVES

To examine interobserver reliability of the Acute Physiologic and Chronic Health Evaluation (APACHE) II score and identify major causes of variability in data collection.

DESIGN

Descriptive, comparative analysis.

SETTING

Nine intensive care units in two teaching and six community hospitals

SUBJECTS

A random sample of 342 patient records selected from a network database.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Data were reabstracted and compared with the original records. Individual physiologic points derived from the APACHE II scoring system (instead of the actual physiologic values) were compared using the kappa statistic. Paired measurements of the continuous variables were compared using the interclass correlation coefficient and Bland-Altman plots. Excellent agreement was found in most demographic, admission, and discharge data. The system failure requiring intensive care unit admission was consistently identified by both data collectors in 88% of cases, but only 66% agreed on the exact admitting diagnosis. For APACHE II score components, the kappa statistic ranged from 0.315 for the Glasgow Coma Scale point to 0.976 for the age point. Significant disagreement regarding the probability of death derived from the APACHE II model was evident in some patient records. Overall agreement among groups of patients regarding the APACHE II score was good, however, with no significant difference in the mean score (20.2 vs. 20.1; p = .758). The predicted mortality from the reabstracted data was 30%, similar to the 27% predicted mortality from the original data (p = .380).

CONCLUSION

Reliability of data collection varied widely in different components of the APACHE II probability-of-death model. Significant discrepancies in some components suggested a lack of explicit definitions and timing for consistent data collection between institutions or between data collectors. Nonetheless, variability resulting from data collection appears to be randomly distributed, so that comparisons of group means are valid.

Consultation length and chronic illness care in general practice: a qualitative study

OBJECTIVE

To study the relationship between duration and content of general practice consultations for patients with chronic conditions.

DESIGN

A qualitative analysis of transcripts of consultations. The major themes and concepts of psychosocial support were identified and coded using the Ethnograph computer package.

SETTING

A mix of rural and urban general practices in two States of Australia in 1993-1994.

PARTICIPANTS

14 selected general practitioners and 50 of their patients with complex chronic conditions.

RESULTS

Transcriptions of 106 consultations were analysed. General practitioners (GPs) led most consultation dialogue and emphasised disease management. The major themes were provision of information by the GP, review of treatment by the GP, review of illness by the GP, and description and explanations of their illness by patients (patient narrative). The first three themes predominated in consultations of all lengths. Longer consultations (20 minutes and over) contained more dialogue initiated by patients and more patient narrative about living with their illness.

CONCLUSIONS

Patients with complex chronic conditions may require longer consultations to allow adequate time for review of their illness and treatment as well as an opportunity to raise issues and concerns about their illness, its impact on their lives and their personal management strategies. Longer consultations may thus provide the mechanism for what has been described as patient "enablement".

Stimulation of tyrosine phosphorylation by progesterone and its 11-OH derivatives: dissection of a Ca(2+)-dependent and a Ca(2+)-independent mechanism

Progesterone has previously been shown to exert non-genomic effects on human spermatozoa by opening plasma membrane ion channels and by stimulating protein tyrosine phosphorylation. Here we examined how these two activities are influenced by 11-hydroxyl substitution of the steroid molecule either in the alpha- or in the beta-configuration. Both the 11alpha-OH and the 11beta-OH derivatives of progesterone were more effective than progesterone in stimulating tyrosine phosphorylation, although 11alpha-OH-progesterone was a markedly weaker Ca(2+)-influx inducing agonist than the other two steroids. In Ca(2+)-containing medium, the agonist activity of the 11alpha-OH derivative was weaker than that of the 11beta-OH derivative, and it was completely abolished by genistein, whereas that of progesterone and its 11beta-OH derivative was inhibited only partly by this drug. In contrast, when applied in Ca(2+)-free medium, the 11alpha-OH derivative was the strongest of the three agonists tested, and the effects of all the three steroids were completely abolished by genistein. These data show that the structural motifs of steroid molecules that are responsible for the stimulation of tyrosine phosphorylation are different from those mediating the steroid action on Ca2+ influx through plasma membrane channels. The synthesis of selective agonists of both activities may lead to the development of new pharmacological agents to be used in the treatment of steroid-dependent pathologies.

Dopexamine attenuates flow motion in ileal mucosal arterioles in normotensive sepsis

OBJECTIVES

Injury to the small intestine is thought to play a crucial role in the development and propagation of sepsis. Cellular hypoxia, caused by hypoperfusion, may result in increased mucosal permeability, thus allowing the translocation of bacteria and endotoxin to the circulation. The purpose of this study was to assess the effect of the synthetic catecholamine, dopexamine, on the mucosal microcirculation of the septic rat ileum.

DESIGN

Randomized, crossover study.

SETTING

Teaching hospital animal laboratory.

SUBJECTS

Sprague-Dawley male rats.

INTERVENTIONS

Sepsis was induced by cecal ligation and perforation in 11 male Sprague-Dawley rats. Six sham animals were also studied. At 24 hrs, rats were anaesthetized, intubated, ventilated, and prepared for intravital microscopy of the mucosal surface of the ileum. Dopexamine (8 microg/kg/min) and saline were infused intravenously into each rat using a randomized crossover design.

MEASUREMENTS AND MAIN RESULTS

Observations were videotaped for later analysis of arteriolar flow patterns, red cell velocity, arteriolar diameter, and intercapillary area. All values are expressed as mean +/- SEM. The main effect of dopexamine infusion in the sepsis group was the attenuation of the rhythmic blood flow patterns (flow motion) observed during saline infusion. In each subject, dopexamine decreased the absolute number of arterioles exhibiting flow motion by 35.93+/-6.81% (p<.001, paired t-test). Dopexamine decreased the amount of time red cell flow was stopped in marginal and central arterioles by 11.83+/-2.49% (p<.001, paired t-test). Dopexamine did not alter significantly the diameter of the marginal arterioles, the intercapillary area, or the red cell velocity compared with saline in the sepsis group. The sham group displayed marked microvascular differences compared with the sepsis group with respect to arteriolar diameter (13.32+/-0.05 vs. 9.46+/-0.24 mm, p<.001), intercapillary area (975.93+/-60.60 vs. 1256.03+/-43.88 mm2, p<.05 ), red cell velocity (611.40+/-38.77 vs. 289.15+/-36.45, p<.001), and blood flow patterns (% displaying flow motion, 15.89+/-6.09 vs. 58.22+/-9.63, p<.01; % time stopped flow, 1.96+/-0.89 vs. 20.21+/-3.92, p<.005).

CONCLUSIONS

These results indicate that dopexamine increased overall blood flow and possibly oxygen delivery to the mucosa by altering patterns of blood flow within the villi. The observation that the diameter of the marginal arterioles is not affected by dopexamine indicates that dopexamine influences the mucosal microcirculation at the level of higher order arterioles. We conclude that sepsis results in abnormal microvascular villus blood flow and that dopexamine can partially restore these changes towards normal.

Patients readmitted to the intensive care unit during the same hospitalization: clinical features and outcomes

OBJECTIVE

To determine the clinical features and outcomes of patients readmitted to the intensive care unit (ICU) during the same hospital stay and the causes for these readmissions.

DESIGN

Multicenter, cohort study.

SETTING

Three ICUs from two teaching hospitals and four ICUs from four community hospitals.

PATIENTS

All ICU admissions were collected prospectively for a registry database in the seven ICUs. We retrospectively analyzed ICU admissions between January 1, 1995 and February 29, 1996.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

During the study period, 236 (4.6%) of the patients discharged alive from the ICU were readmitted to the unit. Patients with gastrointestinal (GI) and neurologic diagnoses had the highest readmission rate. Of the readmissions, 45% had recurrence of the initial disease, 39% experienced new complications, and 14% required further planned operation. Among patients readmitted for the same illness, cardiovascular and respiratory problems were the most frequent diagnoses. Of patients readmitted with a new diagnosis, 30% initially had GI diseases, while respiratory diseases accounted for 58% of the new complications. Readmissions within 24 hrs occurred in 27% of all readmissions. Patients requiring readmission had a higher hospital mortality rate (31.4%) compared with those not requiring readmission (4.3%, p < .001), even after adjustment for disease severity score (odds ratio = 5.93, p < .001).

CONCLUSIONS

Patients with GI and neurologic diseases are at greatest risk of requiring ICU readmission. Respiratory diseases are the major reason for readmission due to new complications. Readmitted patients have a high risk of hospital death that may be underestimated by the usual physiologic indicators on either initial admission or readmission. Further studies are required to determine if patients at risk for readmission can be identified early to improve the outcome.

Selective gut microcirculatory control (SGMC) in septic rats: a novel approach with a locally applied vasoactive drug

Gut mucosal hypoperfusion plays a major role in the pathogenesis of ongoing sepsis and multiple organ dysfunction syndrome. Traditionally, therapy included increasing systemic flow, thus secondarily augmenting blood flow to the gut. Direct manipulation of the gut mucosal microcirculation avoiding systemic effects, i.e., selective gut microcirculatory control (SGMC), has not been tested with a clinically available vasodilating drug. We hypothesized that a topically applied vasoactive drug would affect gut mucosal microcirculation without systemic effects. Twelve Sprague-Dawley rats were randomly assigned to cecal ligation and perforation (CLP), or sham (SC) laparotomy. Twenty-four hours after surgery, mucosal arterioles of a 3-4 cm exteriorized ileal segment were studied using intravital microscopy while suffused with saline followed by sodium nitroprusside (SNP, 100 microg/mL, 3.4 mM). SNP normalized (to SC saline values, 14.5 +/- .6 microm) the CLP arteriolar diameters, from 11 +/- 6 to 14.6 +/- .3 microm (p < .05), while mean arterial pressure (MAP) was stable. Flowmotion patterns were also normalized by SNP, and intercapillary areas (i.e., diffusion distance) were decreased. We conclude that SNP exerted beneficial effects on gut mucosal microcirculation without affecting MAP; therefore, SGMC may be a novel way to affect the course of sepsis.

Polymyxin-dextran antiendotoxin pretreatment in an ovine model of normotensive sepsis

OBJECTIVE

To test the hypothesis that adult sheep pretreated with polymyxin-dextran and then made septic by cecal ligation and perforation would have fewer changes in microvascular integrity and cellular architecture in extrapulmonary organs.

DESIGN

Prospective, randomized, double-blind, placebo-controlled animal study.

SETTING

An animal research facility in a university-affiliated hospital.

SUBJECTS

Mature, male Suffolk sheep (32 to 67 kg).

INTERVENTIONS

Animals with chronic indwelling catheters were pretreated with polymyxin B-dextran (6 mg/kg) or placebo (dextran) and an intra-abdominal focus of infection was then produced by cecal ligation and perforation. Treatment (polymyxin B or placebo) was continued every 8 hrs for 48 hrs.

MEASUREMENTS AND MAIN RESULTS

Forty-eight hours after randomization, the polymyxin B-dextran group manifested significantly less pyrexia (p = .04), higher mean arterial pressures (p = .02), less variable serum albumin concentrations (p = .05), and a trend toward decreased lactate concentrations (p = .10). Qualitative morphometry and semiquantitative scoring of tissue from gastrocnemius muscle demonstrated that polymyxin B-dextran-treated sheep had significantly increased total capillary (p = .04) and capillary luminal areas (p = .038) and less mitochondrial swelling and damage (p = .03) compared with the placebo sheep.

CONCLUSIONS

Pretreatment of sheep in a polymicrobial, peritonitis model of sepsis with polymyxin B-dextran resulted in a significant amelioration of sepsis-induced ultrastructural damage. In placebo-treated control animals, these ultrastructural lesions were associated with a greater severity of sepsis, as measured by the presence of pyrexia, increased lactate concentrations, and less stable blood pressures. These findings justify the investigation of the effects of polymyxin B-dextran in a post onset model of sepsis.

Effect of noninvasive positive pressure ventilation on mortality in patients admitted with acute respiratory failure: a meta-analysis

OBJECTIVE

To critically appraise and summarize the trials examining the addition of noninvasive positive pressure ventilation to standard therapy on hospital mortality and need for endotracheal intubation in patients admitted with acute respiratory failure.

DATA SOURCES

We searched MEDLINE (1966 to September 1995) and key references were searched forward using the Scientific Citation Index (SCISEARCH). Bibliographies of all selected articles and review articles were examined. Authors of all selected and review articles were contacted by letter to identify unpublished work.

STUDY SELECTION

a)

POPULATION

patients with acute respiratory failure; b) intervention: noninvasive positive pressure ventilation; c) outcome: mortality and/or endotracheal intubation; and d) design: randomized, controlled study. Two of us independently selected the articles for inclusion; disagreements were settled by consensus. Seven (three unpublished) of 212 initially identified studies were selected.

DATA EXTRACTION

Two authors independently extracted data and evaluated methodologic quality of the studies.

DATA SYNTHESIS

Noninvasive positive pressure ventilation was associated with decreased mortality (odds ratio = 0.29; 95% confidence interval 0.15 to 0.59) and a decreased need for endotracheal intubation (odds ratio = 0.20; 95% confidence interval 0.11 to 0.36). Sensitivity analysis suggested a greater benefit of noninvasive positive pressure ventilation in patients with chronic obstructive pulmonary disease (COPD). The inclusion/exclusion of unpublished trials did not influence these results.

CONCLUSIONS

The addition of noninvasive positive pressure ventilation to standard therapy in patients with acute respiratory failure improves survival and decreases the need for endotracheal intubation. However, this effect is restricted to patients whose cause of acute respiratory failure is an exacerbation of COPD. Further research is warranted to determine whether noninvasive positive pressure ventilation confers benefit in patients without COPD who have acute respiratory failure.

Diaspirin crosslinked hemoglobin improves systemic oxygen uptake in oxygen supply-dependent septic rats

Diaspirin crosslinked hemoglobin (DCLHb) is a cell-free hemoglobin derived from human erythrocytes. DCLHb has been shown to improve blood flow to vital organs in healthy and septic animals. In this study, we determined the efficacy of DCLHb by comparing its effect on systemic O2 uptake to freshly stored and aged red blood cells (RBCs) in septic rats. Twenty-four hours after induction of sepsis by cecal ligation and perforation, O2 supply dependency was created by isovolemic hemodilution with rat plasma. In O2 supply dependency, rats were randomized to receive an exchange transfusion of 7.5 ml "fresh" RBCs (stored < 6 d; Hct: 70%), "fresh" diluted RBCs (stored < 6 d; Hct: 30%), "old" RBCs (stored 28 to 35 d; Hct: 70%), or DCLHb (Hb: 100 g/L). We found, that survival following O2 supply dependency and transfusion with old RBCs was poor (33% versus 91.7% in the other groups; p < 0.01), precluding further analysis of post-transfusion data from this group. Systemic O2 uptake increased in all remaining groups (p < 0.001), while systemic O2 delivery increased with "fresh" RBCs (p < 0.0001) and "fresh" diluted RBCs (p < 0.05) but not with DCLHb. Systemic O2 extraction increased with DCLHb as compared to baseline (p < 0.05) and to the other groups (p < 0.0001). Improved tissue oxygenation was associated with an increase in blood pressure and a fall in arterial lactate in all groups. We conclude that transfusion of DCLHb or "fresh" RBCs was efficacious at increasing systemic O2 uptake in O2 supply-dependent, septic rats.

The effects of cross-linked hemoglobin on regional vascular conductance in dogs

Hemoglobin (Hgb) solutions cause systemic vasoconstriction, which might limit their use as intraoperative blood substitutes. This constriction is thought to be caused by interaction between Hgb and nitric oxide (NO). To determine whether alpha-alpha cross-linked hemoglobin (XL-Hgb) interferes with NO-mediated vasodilation caused by acetylcholine (ACh) and sodium nitroprusside (NTP), we infused these compounds into the femoral, superior mesenteric, and circumflex coronary arteries of anesthetized dogs (n = 6) before and after partial exchange transfusion with XL-Hgb. Additional animals (n = 6) were studied after treatment with 5% albumin. XL-Hgb administration increased mean arterial pressure (MAP) from 81 +/- 5 to 112 +/- 8 (P < 0.05). Albumin reduced MAP from 84 +/- 4 mm Hg to 76 +/- 4 mm Hg (P < 0.05). Vascular conductance after XL-Hgb decreased in the femoral artery, was not changed in the mesenteric bed, and increased modestly in the coronary artery (from 0.19 +/- 0.03 to 0.26 +/- 0.02 mL x mm Hg(-1) x min(-1), P < 0.05). After albumin, conductance was unchanged in the femoral artery and increased in the mesenteric artery. Conductance also increased in the coronary bed (from 0.25 +/- 0.02 to 0.49 +/- 0.03 mL x mm Hg(-1) x min(-1), P < 0.05). The vasodilator response to ACh in the femoral or mesenteric beds was either unaffected or augmented by either XL-Hgb or albumin. In the coronary bed, XL-Hgb blunted the dilator responses to ACh and NTP, while albumin augmented the coronary dilator responses to ACh. In five additional dogs, the NO synthase inhibitor N(G)-monomethyl L-arginine caused MAP to increase from 85 +/- 4 to 90 +/- 8 mm Hg and blunted the coronary dilator responses to ACh by approximately 25%. Subsequent XL-Hgb administration caused a further increase in MAP to 112 +/- 19 mm Hg (P < 0.05) and also further blunted ACh-mediated vasodilator responses in the coronary circulation. XL-Hgb has complex effects on the circulatory system, including a reduction in the vasodilator responses to ACh and NTP in canine coronary arteries in vivo. The potential impact of these events on patients with significant coexisting disease is unclear.

Characteristics of longer consultations in Australian general practice

OBJECTIVE

To assess the association between general practitioner (GP) billing for "longer" consultations, patient factors linked with health care need, and other consultation characteristics.

DESIGN

Retrospective analysis of data from Medicare (1984-1992), Australian Morbidity and Treatment Survey (1990-1991) and Australian Capital Territory Record Linkage Study (1988-1992).

SETTING

Australian general practice, 1984 (introduction of Medicare) to 1992.

MAIN OUTCOME MEASURES

Consultations billed as longer (> or = 20 or > 25 minutes) compared with standard; type of billing (bulk or private); patient health care need (defined as health and sociodemographic factors linked to worse health outcomes); consultation continuity, type of care given and number of problems managed.

RESULTS

Longer billed consultations increased between 1984 and 1992, from 2.8% to 6.7% of all standard and longer consultations. Longer consultations were more likely to be bulk-billed than privately billed (odds ratio [OR], 1.74). They were more likely than standard consultations to deal with psychological diagnoses (OR, 2.06; 95% confidence interval [95% Cl], 1.83-2.32) or multiple problems (OR for four versus one diagnosis, 5.18; 95% Cl, 4.31-6.22) and to involve patients aged under 50 years, new to the practice or with new problems, but not chronic disease. In the ACT, those billed for longer consultations were more commonly tertiary educated (OR, 1.99; 95% Cl, 1.35-2.94), bulk-billed (OR, 2.75; 95% Cl, 2.51-3.10), aged 40-49 years and non-obese.

CONCLUSION

Longer billed consultations were not associated with greater patient need, other than psychosocial need, but with bulk billing and patient socioeconomic advantage. However, evaluation was complicated by the effects of continuity of care and number of problems managed in the consultation.

Transfusing red blood cells stored in citrate phosphate dextrose adenine-1 for 28 days fails to improve tissue oxygenation in rats

OBJECTIVE

To determine whether the time that red blood cells are stored in citrate phosphate dextrose adenine-1 solution before transfusion alters the ability to improve tissue oxygenation.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research institute laboratory.

SUBJECTS

Male Sprague-Dawley rats (350 to 450 g).

INTERVENTIONS

Twenty-four hours after randomization to sham laparotomy (n = 21) or cecal ligation and perforation (n = 16)1 supply-dependency of systemic oxygen uptake (VO2) was induced in rats by isovolemic hemodilution. Rats were then re-randomized to receive either rat red blood cells stored in citrate phosphate dextrose adenine-1 for 3 days ("fresh" n = 17) or rat red blood cells stored in citrate phosphate dextrose adenine-1 for 28 days ("old" n = 20).

MEASUREMENTS AND MAIN RESULTS

Changes in systemic VO2 were measured for 90 mins to determine the efficiacy of the treatment. Statistical analysis included a fully factorial repeated-measures, generalized linear model. No significant interaction was found between cecal ligation and perforation or sham animals and transfusion with fresh or old red blood cells. However, comparing the combined groups of animals receiving either fresh or old red blood cells, we found that after the transfusion of old red blood cells, systemic VO2 was not significantly improved (after hemodilution 1.68 +/- 0.27 mL/100 g/min, after transfusion 1.86 +/- 0.17 mL/100 g/min; p > .05). In contrast, transfusion with fresh red blood cells acutely increased systemic VO2 (after hemodilution 1.62 +/- 0.06 mL/100 g/min, after transfusion 2.10 +/- 0.09 mL/100 g/min; p = .049).

CONCLUSION

Storage of rat red blood cells for 28 days in citrate phosphate dextrose adenine-1 impaired their ability to improve tissue oxygenation when transfused into either control or septic rats placed into supply dependency of systemic VO2.

Assessing the efficiency of the admission process to a critical care unit: does the literature allow the use of benchmarking?

OBJECTIVES

To determine the ability of the current literature to supply appropriate data for benchmarking admission practice to a multidisciplinary critical care unit.

DESIGN

Retrospective review of data collected prospectively on a cohort of 614 patients and a systematic review of the literature.

SETTING

A 30-bed multidisciplinary critical care unit at a university teaching hospital.

PATIENTS

Consecutive admissions to the critical care unit over a 6-month period.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

For each patient, demographic data and admitting diagnosis were recorded on admission. Information necessary to calculate the Acute Physiology and Chronic Health Evaluation II and Therapeutic Intervention Scoring System (TISS) scores were collected daily. TISS variables were categorized as "active" or "non-active" treatment variables. Patients were then identified on a daily basis as receiving or not receiving active treatment. A review of the literature, using MEDLINE and the search term "Therapeutic Intervention Scoring Index" (as a textword), was conducted to identify studies that had similarly divided their patients. Using the method of benchmarking, the proportion of patients admitted who received active treatment during their stay in the critical care units was compared between the index critical care unit and those in the literature. A greater proportion of the patients admitted to our unit received active treatment (97.7%) when compared to other studies in the literature (20-66%). However, a number of potential confounding factors were present, such as the availability of intermediate care units, overnight recovery room ventilation, and critical care bed availability between the index critical care unit and those described in the literature.

CONCLUSIONS

The current literature does not provide adequate data on critical care unit admission practices to allow useful application of the method of benchmarking. There is a need for publicly accessible large databases to allow individual critical care units to determine their level of efficiency when compared to similar institutions.

Myocardial collagen changes and edema in rats with hyperdynamic sepsis

OBJECTIVE

To determine if sepsis, which is accompanied by both systolic and diastolic myocardial dysfunction, involves changes in myocardial collagen, as myocardial collagen changes can affect both myocardial compliance and contractility.

DESIGN

Prospective, randomized, controlled study.

SETTING

Animal laboratory at a university-affiliated hospital.

SUBJECTS

Male Sprague-Dawley rats, weighing 310 to 396 g.

INTERVENTIONS

Cecal ligation and perforation (to induce sepsis) for 24 (n = 9) or 48 hrs (n = 9); sham laparotomy for 24 (n = 10) or 48 hrs (n = 9) with saline fluid resuscitation or normal control (n = 5) groups.

MEASUREMENTS AND MAIN RESULTS

Collagen content and interstitial space were determined, using polarized light microscopy and a computer video densitometry system. At 24 and 48 hrs post surgery, heart rate and cardiac index were increased, and systemic vascular resistance index was decreased significantly in the sepsis vs. the sham rats. Collagen content was decreased significantly in the sepsis vs. the sham groups both at 24 and 48 hrs following surgery (1.83 +/- 0.79 [SD] % [24 hrs], 1.76 +/- 0.31% [48 hrs] vs. 2.83 +/- 0.73% [24 hrs], 2.25 +/- 0.72% [48 hrs]; p < .01). Interstitial space was increased significantly in the sepsis vs. the sham groups (13.9 +/- 3.5% [24 hrs], 15.6 +/- 5.2% [48 hrs] vs. 8.6 +/- 4.2% [24 hrs], 9.9 +/- 4.8% [48 hrs]; p < .01).

CONCLUSIONS

Sepsis is accompanied by changes in myocardial collagen content and myocardial edema. These changes may contribute to the systolic and diastolic myocardial dysfunction, and particularly to the ventricular dilation, observed in sepsis.

Intestinal mucosal permeability to 51Cr-ethylenediaminetetraacetic acid is increased after bilateral lower extremity ischemia-reperfusion in the rat

BACKGROUND

Despite successful revascularization of ischemic extremities, multiorgan dysfunction syndrome develops in some patients. Mechanisms responsible for this are not known; however, the gastrointestinal tract has been implicated as a possible mediator. Our objective was to demonstrate increased intestinal mucosal permeability after bilateral hindlimb ischemia-reperfusion (I-R) in a rodent model.

METHODS

Sixteen male Wistar rats were randomized either to 4 hours of bilateral hindlimb tourniquet ischemia and 24 hours of reperfusion (n = 8) or control groups (n = 8). The animals received 10 MuCi 51Cr-ethylenediaminetetraacetic acid (EDTA) by gavage, and excretion was measured in urine collected every 8 hours in 16 animals and every 4 hours in 8 animals. Arterial blood pressure was monitored continuously. Intravenous normal saline solution (3 ml/hr) with fentanyl (2 microgram/100 gm/hr) was continuously administered. Immediately before death complete blood count and levels of arterial lactate, creatinine, and urea were obtained. Mesenteric lymph nodes were harvested from the ileocecal region and cultured. Distal small bowel and proximal colon were preserved for histologic analysis. An additional 11 rats, six experimental and five control, were evaluated for mesenteric lymph node cultures only.

RESULTS

Urinary excretion of 51Cr-EDTA was significantly greater in the I-R group between 0 and 8 hours (p < 0.02) and 8 to 16 hours (p < 0.0002) of reperfusion. This increase occurred as early as 4 to 8 hours of reperfusion (p < 0.0001). Urine volume in the I-R group was significantly reduced during 0 to 4 hours of reperfusion (p < 0.002). Hemoglobin and lactate level were significantly different in the I-R group. Leukocyte and platelet counts, levels of creatinine and urea, and colony counts from mesenteric lymph nodes were similar in I-R and control groups. Blinded histologic analysis of bowel segments did not reveal morphologic differences.

CONCLUSIONS

Bilateral hindlimb I-R produces remote intestinal mucosal injury shown by significantly increased permeability to 51Cr-EDTA. Such increased mucosal permeability may be important in the development of multiorgan dysfunction syndrome in patients who sustain lower extremity I-R injury.

Sepsis depresses the metabolic oxygen reserve of the coronary circulation in mature sheep

This study was undertaken to describe the metabolic O2 reserve of the coronary circulation in an awake sheep model of hyperdynamic sepsis. Forty-eight hours after sheep were randomized to either a SHAM group (n = 8) or a cecal ligation and perforation (CLP) group (n = 8), we measured hemodynamics, organ blood flows, and systemic and myocardial O2 metabolism variables at baseline and through four stages of progressive hypoxia. A significant elevation in arterial lactate levels occurred at a higher O2 delivery in the CLP group (527 +/- 55 ml/min/m2) than in the SHAM group (357 +/- 29 ml/min/m2, p < 0.05). The heart's metabolic O2 reserve (difference in circulatory determinants of O2 availability between baseline and where O2 uptake could not be sustained) was exhausted at an O2 content of 56.9 +/- 4.2 ml O2/L in SHAM sheep and 79.6 +/- 7.2 ml O2/L (p < 0.05) in CLP sheep. An increase in coronary blood flow was three times greater in SHAM than in CLP animals. Myocardial O2 extraction increased in hypoxia in SHAM sheep (0.78 +/- 0.03 to 0.88 +/- 0.02, p < 0.05), but not in CLP sheep (0.79 +/- 0.02 to 0.80 +/- 0.04). We conclude that the metabolic O2 reserve of the coronary circulation is depressed in this model of hyperdynamic sepsis as the ability to increase both coronary blood flows and myocardial O2 extraction was significantly limited.

Decreased capillary density in vivo in bowel mucosa of rats with normotensive sepsis

Translocation of bacteria and endotoxin leading to sepsis occurs in animals subjected to burns or intestinal ischemia. This may be mediated in part by bowel mucosal microcirculatory dysfunction. However, the direct effect of sepsis on the mucosal microcirculation is unknown. The objective of this study was to develop a technique for intravital microscopy of the mucosa of the small bowel in an animal model of normotensive sepsis. We tested the hypothesis that normotensive sepsis induced by cecal ligation and perforation leads to a decrease in perfused capillaries in the small bowel mucosa at 24 hr. Twelve male Sprague-Dawley rats were hemodynamically monitored and randomly assigned to cecal ligation and perforation (CLP) or control laparotomy (sham). Twenty-four hours after initial surgery each animal was reanesthetized and the mucosal surface of the distal small bowel prepared for intravital microscopy. Laser doppler measurements of bowel wall blood flow were made immediately and repeated after a 30-min stabilization period. Intravital microscopy of the mucosal microcirculation of six villi per animal was performed and the images recorded on videotape (2 min/villus). The areas surrounded by perfused capillaries (intercapillary area) were then measured using video analysis software. Laser doppler flowmetry revealed a decrease in bowel wall blood flow during the stabilization period in the shams that did not occur in the CLP rats. The intercapillary areas were significantly greater in the CLP rats compared to sham rats (1329 +/- 316 microns2 vs 979 +/- 217 microns2, P = 0.044). The intercapillary areas were also more highly variable in the CLP group (median coefficient of variation 102 vs 83% in the sham group, P = 0.025). Intravital microscopy may be used to examine microcirculatory function of the small bowel mucosa. Sepsis induced by CLP leads to a decrease in the number of perfused capillaries in the small bowel mucosa.

Local cholinergic mechanisms mediate nitric oxide-dependent flow-induced vasorelaxation in vitro

To determine whether local cholinergic mechanisms evoke nitric oxide (NO)-mediated flow-induced vasorelaxation, canine coronary artery rings without endothelium were suspended beneath an organ chamber that contained a stainless steel tube and a femoral artery segment with endothelium. The rings were superfused at a basal rate of 1 ml/min with physiological salt solution that was bubbled with 95% O2-5% CO2 and maintained at 37 degrees C. They were stretched to optimal length and contracted with prostaglandin F 2 alpha (2 x 10(-6) M). When flow through the stainless steel tube (direct superfusion) was increased from the basal rate of 1 to 4 ml/min, coronary force did not change. Superfusion of the rings (n = 8) with effluent from the femoral segment (endothelial superfusion) at 4 ml/min to study flow-induced vasodilation caused a 67.3 +/- 10.8% relaxation. Treatment of the segment with the NO synthase blocker NG-monomethyl-L-arginine (10(-4) M) eliminated the relaxation seen during endothelial superfusion (P < 0.05 vs. control). Application of atropine (10(-6) M) to additional femoral segments (n = 8) abolished the coronary relaxation observed during endothelial superfusion at 1 ml/ min, and the flow-induced relaxation observed at 4 ml/min was reduced from 64 +/- 8.3 to 27 +/- 5.6% (P < 0.05 vs. control). In studies on additional segments and rings (n = 6), the flow-induced relaxations at 4 ml/min of endothelial superfusion were blunted from 86 +/- 10 to 28 +/- 13% after the segments were treated with acetylcholinesterase (0.00028 U/min for 20 min). These data indicate that basal- and flow-induced release of NO from the vascular endothelium can be mediated by local cholinergic mechanisms. It is possible that flow causes acetylcholine release from certain endothelial cells, which stimulates NO release from these cells or from neighboring endothelial cells.

Pentoxifylline does not prevent microvascular injury in normotensive, septic rats

OBJECTIVE

To determine if treatment with pentoxifylline would decrease the tissue injury that occurs in a normotensive model of sepsis.

DESIGN

Random assignment to control, cecal ligation-perforation, or cecal ligation-perforation plus pentoxifylline groups for a 24-hr study.

SETTING

Animal laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Sepsis was induced by cecal ligation-perforation with aggressive fluid resuscitation (normal saline 10 mL/kg/hr). Pentoxifylline was administered as a 2-mg/kg bolus, followed by a continuous infusion of 6 mg/kg/hr.

MEASUREMENTS AND MAIN RESULTS

Compared with controls, rats in the cecal ligation-perforation group had an increased heart rate (432 +/- 12 vs. 399 +/- 10 beats/min) and respiratory rate (129 +/- 6 vs. 94 +/- 7 breaths/min). Blood pressure was slightly decreased (104 +/- 4 vs. 125 +/- 5 mm Hg), while cardiac index was not significantly different (50.1 +/- 5.7 vs. 40.7 +/- 3.9 mL/min/100 g). Blood pressure (103 +/- 4 mm Hg) was the only parameter that was significantly different in the cecal ligation-perforation plus pentoxifylline group compared with controls. When compared with controls, tissue wet/dry weight ratios were increased in the diaphragm of the cecal ligation-perforation group and in the liver, pancreas, small bowel, and large bowel of the cecal ligation-perforation, and the cecal ligation-perforation plus pentoxifylline groups. Tissue/plasma albumin ratios were increased in the diaphragm of the cecal ligation-perforation group and in the liver, pancreas, and large bowel of the cecal ligation-perforation and the cecal ligation-perforation plus pentoxifylline groups. There were no significant differences between the cecal ligation-perforation and the cecal ligation-perforation plus pentoxifylline groups.

CONCLUSIONS

Normotensive sepsis is accompanied by increased vascular permeability in the diaphragm and intra-abdominal organs. Pentoxifylline appears to attenuate some of the systemic manifestations of sepsis. However, pentoxifylline did not prevent the development of protein-rich tissue edema.

Modulation of hemodynamics and organ blood flow by nitric oxide synthase inhibition is not altered in normotensive, septic rats

Hyperdynamic sepsis is associated with a redistribution of organ blood flow. We hypothesized that increased nitric oxide (NO) production could mediate this process. The objective of this study was to determine the effect of a NO synthesis inhibitor on systemic and organ blood flows in vivo in septic and in normal rats. Rats were instrumented for hemodynamic monitoring and randomized to undergo cecal ligation and perforation (CLP) or control laparotomy. Cardiac output and organ blood flow were measured by thermodilution and radioactive microspheres, respectively. Baseline values were obtained at 24 h after CLP or control laparotomy and after the administration of L-nitro-arginine methyl ester (L-NAME) at 2, 4, 8, and 16 mg/kg intravenously. All studies were performed in awake, unrestrained animals. Septic animals were normotensive and hyperdynamic. L-NAME decreased cardiac index and increased systemic vascular resistance and mean arterial blood pressure to an equivalent degree in control and in CLP animals. CLP was associated with significantly increased relative blood flow to the small bowel and portal circulation. Although cardiac output decreased with L-NAME, blood flow to the diaphragm, liver, and brain was relatively well preserved. Absolute blood flow to other organs, including small bowel, decreased in parallel to the cardiac output. The effect of L-NAME on organ blood flow was comparable in control and in CLP animals. We conclude that the influence of NO on organ blood flows appears to vary between organs, but that NO does not explain the redistribution of blood flow observed in hyperdynamic sepsis.

Does implementing pulse oximetry in a critical care unit result in substantial arterial blood gas savings?

OBJECTIVES

To examine the impact of pulse oximetry on the use of arterial blood gas and other laboratory determinations and to examine predictors of the use of arterial blood gas measurements.

DESIGN

Before (preoximetry)/after (postoximetry) study.

SETTING

Thirty-bed multidisciplinary critical care unit.

PATIENTS

Consecutive admissions of 300 patients (150 before and 150 after oximetry).

MEASUREMENTS

For each patient examined, the number of arterial blood gas determinations, serum electrolyte levels, complete blood chemistries, arterial lactate levels, and creatinine samples were recorded for the initial 9 days of the stay in the critical care unit. These data were stratified by nursing shift (day vs night) and by the source of the admission (medical vs surgical). Other information collected included demographic variables, the severity of illness, the length of stay in the critical care unit, and various ventilatory parameters.

RESULTS

Introducing pulse oximetry was associated with a marginal (10.3 percent; p < 0.025) reduction in the use of arterial blood gas determinations. This decrease was accounted for by changes occurring on the night shift and in the surgical patient. These findings were also observed for serum electrolyte determinations. No significant differences in the use of arterial blood gas measurements were found for medical patients. No significant differences were found in the use of arterial lactate levels, complete blood chemistries, or creatinine determinations. Significant predictors of arterial blood gas determinations included the number of days intubated, the number of ventilator orders, the number of days on an inspired oxygen content (FIO2) greater than 50 percent, and the acute physiology and chronic health evaluation II (APACHE II) score.

CONCLUSIONS

The implementation of pulse oximetry in this manner gives an idea how effective the technology will be in reducing the use of arterial blood gas determinations without guidelines for the use of pulse oximetry. As only a marginal decrease was observed in the total population of medical and surgical patients, and only on the night shift, formal and standardized guidelines for the most efficient use of pulse oximetry should be considered. If these were considered, pulse oximetry may indeed make a significant contribution to improving the efficiency of care services.