Reduced blood loss during burn surgery

The purpose of this study was to investigate the use of subcutaneous injection of burn wounds and skin graft donor sites with an adrenaline-saline solution to reduce blood loss during burn surgery. This retrospective study reviewed the requirements of blood products in 30 randomly selected adult patients with more than 10% body area burned, who had at least one burn operation at a university regional burn center, between January 1991 and June 1997. Patients were matched by age and percent body area burned and stratified according to the surgical technique in two groups. In Group 1, 15 patients received the modified tumescent surgical technique: subcutaneous injection of adrenaline (1 part/million in warm saline solution) into the subcutaneous tissue of the donor sites for autologous skin graft and areas of burn eschar to be excised, combined with pneumatic tourniquets in extremities and saline-adrenaline soaked nonadherent pads. In Group 2, 15 patients received the traditional surgical technique: soaked gauze compresses with an adrenaline-thrombin solution (1 ml of 1:1,000 adrenaline, thrombin 10,000 units, and 1 L of normal saline). Outcome measures, transfusion of blood products, operating time and complications between the two patient groups were analyzed using the Wilcoxon 2-sample test. The two patient groups were not different by age (40.4 +/- 19.4 vs 38.9 +/- 17.9), percent total body area burned (27.6 +/- 15.4 vs 32.8 +/- 13.4), or percent full thickness burn (7.0 +/- 8.5 vs 11.5 +/- 8.5). The modified tumescent surgical technique significantly reduced mean total blood units transfused per patient (7.9 +/- 11.5 vs 15.7 +/- 12.9 units; P = .031), and the mean blood units transfused intraoperatively per patient (4.7 +/- 7.8 vs 8.9 +/- 8.0 units; P = .026). The modified tumescent surgical technique significantly reduced the intraoperative and total blood transfusion requirements in our thermally injured patients.

Minimizing blood loss in burn surgery

BACKGROUND

Significant blood loss continues to plague early tangential excision of the burn wound. Although various techniques to reduce intraoperative blood loss have been described, there is an absence of uniformity and consistency in their application. Furthermore, it is unclear whether these techniques compromise intraoperative tissue assessment and wound outcome. The purpose of this study was to evaluate the effects of a comprehensive intraoperative blood conservation strategy on blood loss, transfusion requirements, and wound outcome in burn surgery.

METHODS

An intraoperative blood conservation strategy (CONSV) that included donor site and burn wound adrenaline tumescence, donor site and excised wound topical adrenaline, and limb tourniquets was prospectively evaluated and compared with a historical control group (HIST) where only topical adrenaline and thrombin were applied to donor sites and excised wounds.

RESULTS

Estimated blood loss was reduced from 211 +/- 166 mL per percentage body surface area excised and grafted in the HIST group to 123 +/- 106 mL in the CONSV group (p = 0.02). Similarly, the intraoperative transfusion requirement in the HIST group was reduced from 3.3 +/- 3.1 units per case to 0.1 +/- 0.3 units per case in the CONSV group (p < 0.001). There was no compromise in wound outcome in the CONSV group, which had a mean skin graft take rate of 96 +/- 4.2%.

CONCLUSION

The application of a strict and comprehensive intraoperative blood conservation strategy during burn excision and grafting resulted in a profound reduction in blood loss and transfusion requirements, without compromising wound outcome.

The 2000 Moyer Award. The relevance of base deficits after burn injuries

The relevance of an elevated base deficit (BD) during the fluid resuscitation of a thermally injured patient is not completely understood. After nonthermal trauma, early elevation of the BD represents insufficient cellular perfusion and is ultimately associated with a higher incidence of organ dysfunction and death. However, this relationship has not been completely examined after burn injuries. The purpose of this study was to determine if elevation of the BD during burn resuscitation was associated with potential consequences of malperfusion, such as systemic inflammatory response syndrome, acute respiratory distress syndrome, and multiple organ dysfunction. The records of 72 patients with burn injuries (mean age, 46 +/- 17 years; mean total body surface area burned, 44% +/- 18%) who required fluid resuscitation on admission to an adult regional burn center were analyzed. Patients with a mean BD of less than -6 mmol/L during the first 24 hours were compared with patients with a mean BD of more than -6 mmol/L. Despite adequate resuscitation with good maintenance of urinary output, the patients in the group with a mean BD of less than -6 mmol/L had more florid systemic inflammatory response syndrome (P = .004), had more prevalent acute respiratory distress syndrome (P = .012), and experienced more severe multiple organ dysfunction (P < .001) compared with patients in the group with a mean BD of more than -6 mmol/L. The results suggest that abnormal elevation of the BD after burn injuries represents a malperfusion state, which may not be recognized if only "traditional" parameters, such as UO, are followed. Furthermore, this state appears to be related to the onset of more severe systemic inflammation and organ dysfunction.

The use of inhaled nitric oxide as adjuvant therapy in patients with burn injuries and respiratory failure

Inhaled nitric oxide (NO) is a relatively new modality in the management of acute respiratory distress syndrome. The purpose of this study was to examine our experience with inhaled NO in 10 adult patients with burn injuries and acute respiratory distress syndrome-related oxygenation failure. The patients had a mean age of 50 +/- 19 years and a mean burn size of 41% +/- 20% of the total body surface area. Seven patients died and 3 survived. The survivors and nonsurvivors did not differ with respect to age, burn size, pre-NO ventilator settings, or indices of oxygenation including PaO2, oxygen saturation in arterial blood, PaO2/fraction of inspired oxygen (FIO2) ratio, and alveolar-arterial oxygen tension difference. The concentration of NO administered ranged between 5 ppm and 30 ppm. PaO2, oxygen saturation in arterial blood, and the PaO2/FIO2 ratio increased in all patients. Although it was not statistically significant, survivors tended to have a more vigorous and sustained response than non-survivors; this was best exemplified by the change in PFR. During the first hour of therapy, the PaO2/FIO2 ratio increased from 64.3 +/- 12.7 to 231.8 +/- 154.5 in survivors and from 93.9 +/- 44.0 to 161.5 +/- 81.8 in the nonsurvivors. After 12 hours of therapy, the PaO2/FIO2 ratio was 306.2 +/- 333.7 in the survivors and 178.9 +/- 69.9 in the nonsurvivors. There were no complications associated with the use of inhaled NO. Although a stronger early response to NO seems to occur in survivors, we cannot definitely conclude that the early response pattern is predictive of recovery. Nonetheless, we believe that inhaled NO has a useful role in the treatment of patients with burn injuries and severe acute respiratory distress syndrome-related oxygenation failure.

Control of pre-T cell proliferation and differentiation by the GTPase Rac-I

The GTPase Rac-I has the potential for pleiotropic functions due to its ability to interact with multiple effectors. Here, activation of Rac-I is shown to potently regulate pre-T cell differentiation and proliferation at the point of T cell antigen receptor (TCR) beta selection. An activated Rac-I effector domain mutant that restricts signaling to particular actions on actin dynamics can drive pre-T cell differentiation. Rac-I activation cannot fully substitute for the pre-TCR complex but can fully correct defects in pre-T cell development in mice lacking the adapter molecule Vav-1. The present study identifies the subset of Rac-I responses that mediate Vav-1 action as critical regulators of TCR beta selection.

Membrane recruitment of coatomer and binding to dilysine signals are separate events

It has previously been shown that transport of newly synthesized proteins and the structure of the Golgi complex are affected in the Chinese hamster ovary cell line ldlF, which bears a temperature-sensitive mutation in the Coat protein I (COPI) subunit epsilon-COP (Guo, Q., Vasile, E., and Krieger, M. (1994) J. Cell Biol. 125, 1213-1224; Hobbie, L., Fisher, A. S., Lee, S., Flint, A., and Krieger, M. (1994) J. Biol. Chem. 269, 20958-20970). Here, we pinpoint the site of the secretory block to an intermediate compartment between the endoplasmic reticulum (ER) and the Golgi complex and show that the distributions of ER-Golgi recycling proteins, such as KDEL receptor and p23, as well as resident Golgi proteins, such as mannosidase II, are accordingly affected. At the nonpermissive temperature, neither the stability of the COPI complex nor its recruitment to donor Golgi membranes is affected. However, the binding of coatomer to the dilysine-based ER-retrieval motif is impaired in the absence of epsilon-COP, suggesting that dilysine signal binding is not the major means of COPI recruitment. Because expression of the exogenous chimera of epsilon-COP and green fluorescent protein in ldlF cells at nonpermissive temperature rapidly restores the wild type properties, epsilon-COP is likely to play an important role in the cargo selection events mediated by COPI.

Use of coagulase gene (coa) repeat region nucleotide sequences for typing of methicillin-resistant Staphylococcus aureus strains

Coagulase gene (coa) short sequence repeat region sequencing was used to measure relatedness among a collection of temporally and geographically diverse methicillin-resistant Staphylococcus aureus isolates. The results show that coa polymorphism is free of strong selective pressure and has a low index of variation that may be useful for long-term epidemiological investigations. coa typing is a useful addition to spa typing for analysis of S. aureus, including methicillin-resistant strains.

Hearing conservation for farmers: source apportionment of occupational and environmental factors contributing to hearing loss

Those who work on farms continue to have a strikingly high prevalence of hearing loss, despite efforts to promote hearing conservation in agriculture. To develop improved hearing conservation programs, we performed a source apportionment analysis for hearing loss in a large, multiphasic health survey, the New York Farm Family Health and Hazard Survey. We used information from audiometric, otoscopic, and tympanometric examinations; detailed general health and farm exposure interviews; and a second interview that focused on additional potential determinants of hearing loss. Hearing loss on audiometry was significantly associated with increased age, male gender, education through high school or less, lifetime years of hunting with guns, lifetime years of use of a grain dryer, and a history of spraying crops during the previous year. Hearing conservation programs for farmers should thus be directed toward reduction in noise exposure, both from occupational and non-occupational sources. Additional study is needed to evaluate the association seen between crop spraying and hearing loss.

Identification of secreted proteins of Mycobacterium tuberculosis by a bioinformatic approach

Proteins secreted by Mycobacterium tuberculosis are usually targets of immune responses in the infected host. Here we describe a search for secreted proteins that combined the use of bioinformatics and phoA' fusion technology. The 3,924 proteins deduced from the M. tuberculosis genome were analyzed with several computer programs. We identified 52 proteins carrying an NH(2)-terminal secretory signal peptide but lacking additional membrane-anchoring moieties. Of these 52 proteins-the TM1 subgroup-only 7 had been previously reported to be secreted proteins. Our predictions were confirmed in 9 of 10 TM1 genes that were fused to Escherichia coli phoA', a marker of subcellular localization. These findings demonstrate that the systematic computer search described in this work identified secreted proteins of M. tuberculosis with high efficiency and 90% accuracy.

Identification and characterization of two divergently transcribed iron regulated genes in Mycobacterium tuberculosis

SETTING

Low iron availability in the host induces the expression of iron acquisition systems and virulence genes in many pathogens. IdeR is a mycobacterial iron dependent regulator that controls the iron starvation and oxidative stress responses in Mycobacterium smegmatis. It is important to determine the role of IdeR and its regulon in M. tuberculosis, as identification of iron regulated genes can aid in the design of new drugs and generation of attenuated strains.

OBJECTIVE

A potential IdeR binding site was found in the M. tuberculosis genome flanked by two divergently oriented open reading frames, irg1 and irg2. The aim of this study was to determine whether irg1 and irg2 were iron and IdeR regulated genes.

DESIGN

Interaction of IdeR with the putative binding sequence was examined by gel shift and footprinting assays. Transcriptional fusions of irg1 and irg2 to IacZ were used to study the effect of iron levels on the expression of these genes.

RESULTS

IdeR binds to the predicted binding site, which overlaps with the irg1 promoter. irg1 and irg2 expression was decreased by iron in M. tuberculosis and in wild type M. smegmatis, but not in a M. smegmatis ideR mutant.

CONCLUSION

Two M. tuberculosis iron/IdeR regulated genes were identified. irg1 is predicted to be the M. tuberculosis hisE gene, which is involved in histidine biosynthesis. It is directly upstream of the M. tuberculosis hisG. irg2 encodes a putative membrane protein that is a member of the PPE family.

Variation in blood lead and hematocrit levels during pregnancy in a socioeconomically disadvantaged population

Lead is a long-recognized human toxicant that crosses the placenta. Fetal sensitivity to environmental agents can vary with stage of development; therefore, how maternal blood lead levels change during pregnancy and how fetal exposure is influenced provide useful knowledge. In this study, the authors describe longitudinal changes in blood lead levels during the course of pregnancy in a sample of socioeconomically disadvantaged pregnant women. The women were recruited early in pregnancy when they sought care at one of two obstetrics clinics in Albany, New York. Maternal blood lead levels changed between the 1st and 2nd trimesters, from 1.99 microg/dl to 1.69 microg/dl (hematocrit corrected, 1.70-1.62); between the 2nd and 3rd trimester from 1.78 microg/dl to 1.86 microg/dl (hematocrit corrected, 1.65-1.72); and between 3rd trimester and delivery from 1.80 microg/dl to 2.17 microg/dl (hematocrit corrected, 1.70-1.86). These changes were statistically significant and were corrected for secular trends. The rate of change per day in lead levels averaged -36.6% from trimester 1 to trimester 2, 18.3% from trimester 2 to trimester 3, and -40.8% from trimester 3 to delivery. The patterns in our study were consistent with the patterns reported in a few other longitudinal studies of change in lead level during pregnancy. Findings reveal significant associations between maternal blood lead levels and both hematocrit and trimester of pregnancy. Clinicians who interpret test results should take into account the dynamics of these variables when determining appropriate care for both mother and neonate.

Risk factors for Giardia intestinalis infection in agricultural villages practicing wastewater irrigation in Mexico

This study assessed the risk factors for Giardia intestinalis infection in an agricultural population in Mexico. Exposure groups included 2,257 individuals from households exposed to untreated wastewater, 2,147 from a group using the effluent from a series of reservoirs, and 2,344 from rain-fed agricultural villages. Stool samples were collected from 6,748 individuals. Wastewater samples were tested for fecal coliforms/100 ml and Giardia sp. cysts/L. Untreated wastewater samples contained 10(8) fecal coliforms/100 ml and up to 300 Giardia sp. cysts/L. Hydraulic retention (3-7 months) in the reservoirs, however, provided an improved effluent quality (10(1)-10(4) fecal coloforms/100 ml and < or = 5 Giardia sp. cysts/L). Children 1-14 years of age had the highest prevalence of infection (20%). Data showed marginal associations between storing drinking water in unprotected containers and lack of facilities for feces disposal and the risk of infection (odds ratios [ORs] = 1.76 and 1.19, 95% confidence intervals [CIs] = 0.95-3.23, and 0.97-1.45, respectively). Individuals purchasing vegetables at the city market had higher rates of infection than those buying at the village shop (OR = 2.49, 95% CI = 1.00-6.17). No excess risk was found in individuals exposed to untreated wastewater compared with controls (OR = 1.07, 95% CI = 0.84-1.36); the group using reservoir water was not different from the controls (OR = 1.22, 95% CI = 0.94-1.58). No risk from agricultural activities was detected (OR = 0.83). This pattern of infection may be addressed by primary health care and wastewater treatment.

Extra and intracellular expression of Mycobacterium tuberculosis genes

To understand how Mycobacterium tuberculosis survives and grows in an infected host, we are studying the mycobacterial transcriptional machinery and its response to stresses encountered in vitro and in vivo. Much has been learned about sigma factors and other transcriptional regulators concerning their roles in controlling mycobacterial gene expression. It has recently been shown that sigma A is the essential housekeeping sigma factor and the alternative sigma factor sigma B, not essential for growth in a laboratory setting, is required for a robust protective response to various environmental stresses. We are also studying the mechanism by which the R522H mutation in sigma A prevents the transcription of certain genes, including some that are believed necessary for virulence. Also under investigation is the mycobacterial iron acquisition apparatus and its regulation, as metabolism of this essential element plays a key role in microbial pathogenesis. We have identified and characterized the major mycobacterial iron regulator IdeR that blocks the synthesis of the iron uptake machinery and have identified target genes in M. smegmatis and M. tuberculosis that are directly repressed by IdeR. Recent studies have examined the control of M. tuberculosis gene expression in vivo. Among these new approaches are an in vivo expression technology system to identify M. tuberculosis genes that are induced in macrophages and mice and a novel RT-PCR method that allows an accurate comparison between the levels of specific mRNAs in M. tuberculosis grown in vitro with those found in bacteria growing in human macrophages.

COPI vesicles accumulating in the presence of a GTP restricted arf1 mutant are depleted of anterograde and retrograde cargo

Microinjection of the slowly hydrolyzable GTP analogue GTP(gamma)S or the ectopic expression of a GTP restricted mutant of the small GTPase arf1 (arf1[Q71L]) leads to the rapid accumulation of COPI coated vesicles and buds in living cells. This effect is blocked at 15 degrees C and by microinjection of antibodies against (beta)-COP. Anterograde and retrograde membrane protein transport markers, which have been previously shown to be incorporated into COPI vesicles between the endoplasmic reticulum and Golgi complex, are depleted from the GTP(gamma)S or arf1[Q71L] induced COPI coated vesicles and buds. In contrast, in control cells 30 to 60% of the COPI carriers co-localize with these markers. These in vivo data corroborate recent in vitro work, suggesting that GTP(gamma)S and arf1[Q71L] interfere with the sorting of membrane proteins into Golgi derived COPI vesicles, and provide the first in vivo evidence for a role of GTP hydrolysis by arf1 in the sorting of cargo into COPI coated vesicles and buds.

Coat proteins regulating membrane traffic

This review focuses on the roles of coat proteins in regulating the membrane traffic of eukaryotic cells. Coat proteins are recruited to the donor organelle membrane from a cytosolic pool by specific small GTP-binding proteins and are required for the budding of coated vesicles. This review first describes the four types of coat complexes that have been characterized so far: clathrin and its adaptors, the adaptor-related AP-3 complex, COPI, and COPII. It then discusses the ascribed functions of coat proteins in vesicular transport, including the physical deformation of the membrane into a bud, the selection of cargo, and the targeting of the budded vesicle. It also mentions how the coat proteins may function in an alternative model for transport, namely via tubular connections, and how traffic is regulated. Finally, this review outlines the evidence that related coat proteins may regulate other steps of membrane traffic.

Pentacyclic triterpenes from Chuquiraga ulicina

Four taraxastane triterpenes, 3 beta-acetoxy-6 beta-hydroxytaraxasta-20-ene, 6 beta-hydroxytaraxasta-20-en-3-one, 6 beta-hydroxytaraxasta-20-ene 3 beta-palmitate and 3 beta,6 beta-dihydroxytaraxasta-20-ene were isolated from the dichloromethane-methanol extract of Chuquiraga ulicina ssp. ulicina together with the known triterpenes lupeol, lupenyl acetate, lupenone, friedelinol, 3 beta-acetoxy-30-nor-lupan-20-one, and 30-nor-lupan-3 beta-ol-20-one.

ARDS in patients with thermal injury

OBJECTIVE

To determine the time to onset of the adult respiratory distress syndrome (ARDS) in patients with thermal injury requiring mechanical ventilation. Secondarily, to consider the burn-related risk factors, demographics, incidence, and mortality for ARDS in this population.

DESIGN

Retrospective chart review; ARDS defined according to the American-European Consensus Conference and the Lung Injury Severity Score definitions.

SETTING

Regional, tertiary referral, adult burn unit in a university teaching hospital.

PATIENTS AND PARTICIPANTS

Patients with thermal injury requiring mechanical ventilation, admitted between 1 January 1991 and 28 February 1995.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Of 469 consecutive admissions, 126 (26.9%) received intubation and mechanical ventilation. ARDS was defined according to the American-European Consensus and Lung Injury Severity Score (score > 2.5) definitions. The mean time to onset of ARDS from admission to the burn unit was 6.9 +/- 5.2 and 8.2 +/- 10.7 days when defined by the American-European Consensus and Lung Injury Severity Score definitions respectively (p = 0.41). Of the intubated patients, 53.6 and 45.2% developed ARDS according to the American-European Consensus and Lung Injury Severity Score definitions, respectively (p = 0.19). Using multivariate logistic analysis, only age proved to be an independent risk factor for the development of ARDS (p = 0.03), although there was a trend toward an increased incidence of inhalation injury in patients with ARDS. Mortality was not significantly greater (41.8 vs 32.2%) in those with ARDS compared to those without (p = 0.27).

CONCLUSIONS

According to the American-European Consensus Conference and the Lung Injury Severity Score definitions, ARDS is common in the adult burn population and has a delayed onset compared to most critical care populations. We found age to be a major predisposing factor for ARDS.

Evaluation of protein A gene polymorphic region DNA sequencing for typing of Staphylococcus aureus strains

Three hundred and twenty isolates of Staphylococcus aureus were typed by DNA sequence analysis of the X region of the protein A gene (spa). spa typing was compared to both phenotypic and molecular techniques for the ability to differentiate and categorize S. aureus strains into groups that correlate with epidemiological information. Two previously characterized study populations were examined. A collection of 59 isolates (F. C. Tenover, R. Arbeit, G. Archer, J. Biddle, S. Byrne, R. Goering, G. Hancock, G. A. Hébert, B. Hill, R. Hollis, W. R. Jarvis, B. Kreiswirth, W. Eisner, J. Maslow, L. K. McDougal, J. M. Miller, M. Mulligan, and M. A. Pfaller, J. Clin. Microbiol. 32:407-415, 1994) from the Centers for Disease Control and Prevention (CDC) was used to test for the ability to discriminate outbreak from epidemiologically unrelated strains. A separate collection of 261 isolates form a multicenter study (R. B. Roberts, A. de Lencastre, W. Eisner, E. P. Severina, B. Shopsin, B. N. Kreiswirth, and A. Tomasz, J. Infect. Dis. 178:164-171, 1998) of methicillin-resistant S. aureus in New York City (NYC) was used to compare the ability of spa typing to group strains along clonal lines to that of the combination of pulsed-field gel electrophoresis and Southern hybridization. In the 320 isolates studied, spa typing identified 24 distinct repeat types and 33 different strain types. spa typing distinguished 27 of 29 related strains and did not provide a unique fingerprint for 4 unrelated strains from the four outbreaks of the CDC collection. In the NYC collection, spa typing provided a clonal assignment for 185 of 195 strains within the five major groups previously described. spa sequencing appears to be a highly effective rapid typing tool for S. aureus that, despite some expense of specificity, has significant advantages in terms of speed, ease of use, ease of interpretation, and standardization among laboratories.

Endogenous polyamines modulate Ca2+ channel activity in guinea-pig intestinal smooth muscle

The polyamines spermine and spermidine inhibit L-type Ca2+ channels in whole-cell recordings from guinea-pig ileum cells (Gomez and Hellstrand, Pflügers Arch, 430:501-507, 1995 [4]). To study whether they modulate channel activity under physiological conditions, we further investigated their actions on Ca2+ channels and the effects of altered cellular polyamine contents. In inside-out patches, spermine (0.1-1 mM) inhibited channel activity without affecting the amplitude of unitary currents. In cell-attached recordings, addition of spermine to the bath did not influence channel activity in the patch, indicating that its extracellular action is direct and not mediated via passage of the polyamine through the cell membrane. Cellular contents of spermidine and spermine were decreased by about 50% by organ culture of ileum strips for 5 days with the adenosylmethionine decarboxylase inhibitor CGP 48664 (10 microM). This caused enhanced channel activity in cell-attached recordings, suggesting a reduced level of channel block by endogenous polyamines compared with control cells. Whole-cell recordings in the perforated patch mode showed increased current in polyamine-depleted cells, while this was not seen when cells were dialysed with the pipette solution. We conclude that polyamines block Ca2+ channels from the inside as well as the outside of the cell membrane, and that endogenous polyamines in smooth muscle modulate Ca2+ channel activity.

Utilization of intensive care unit days in a Canadian medical-surgical intensive care unit

OBJECTIVES

To analyze the utilization of intensive care unit (ICU) days in a Canadian medical-surgical ICU and to identify ICU patients with prolonged ICU length of stay (LOS).

DESIGN

Prospective descriptive study.

SETTING

A Canadian tertiary care medical-surgical ICU.

PATIENTS

Consecutive patients admitted to an adult medical-surgical ICU. Neurosurgical, cardiac surgical, and coronary care unit patients were excluded.

MEASUREMENTS

For each ICU admission, patient demographics, diagnosis, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, ICU LOS, and hospital mortality were collected. The patients' risk of death was calculated using the APACHE II equation. Admissions were stratified by ICU LOS into four groups: 1 to 2, 3 to 6, 7 to 13, and > or = 14 days. Among the four LOS groups, the number of ICU days and observed and predicted death rates were compared. Admissions were also stratified by risk of death into five probability range quintiles. Among the five risk groups, ICU LOS was compared between survivors and nonsurvivors.

RESULTS

A total of 1,960 admissions utilized 9,298 ICU days. ICU LOS (mean +/- SEM) was 4.74 +/- 0.2 (median, 2; range, 1 to 178) days. Short-stay patients (ICU LOS < or = 2 days) accounted for 60.3% of total admissions but consumed only 16.4% of total ICU days. Long-stay patients (ICU LOS > or = 14 days) accounted for 7.3% of total admissions but consumed 43.5% of total ICU days. Among the long-stay patients, the most common reasons for admission were pneumonia, multiple trauma, neuromuscular weakness, and septic shock. The mortality for long-stay patients approached 50%. When analyzed by patients' mortality risks, those with a risk of death >0.8 (predicted to die) or <0.2 (predicted to live) whose outcomes were opposite to that predicted had twice the ICU LOS compared with patients whose outcomes were consistent with prediction.

CONCLUSION

In a Canadian medical-surgical ICU, patients with ICU LOS > or = 14 days accounted for 7.3% of total admissions but consumed 43.5% of total ICU days. Identification of patients with prolonged ICU LOS who would ultimately die in the ICU may lead to earlier withdrawal of therapy in these patients, resulting in a substantial reduction in suffering and cost savings. In our study population, outcome prediction using the APACHE II equation did not provide sufficient power to accurately discriminate between nonsurvivors and survivors.

Transcriptional control of the iron-responsive fxbA gene by the mycobacterial regulator IdeR

Exochelin is the primary extracellular siderophore of Mycobacterium smegmatis, and the iron-regulated fxbA gene encodes a putative formyltransferase, an essential enzyme in the exochelin biosynthetic pathway (E. H. Fiss, Y. Yu, and W. R. Jacobs, Jr., Mol. Microbiol. 14:557-569, 1994). We investigated the regulation of fxbA by the mycobacterial IdeR, a homolog of the Corynebacterium diphtheriae iron regulator DtxR (M. P. Schmitt, M. Predich, L. Doukhan, I. Smith, and R. K. Holmes, Infect. Immun. 63:4284-4289, 1995). Gel mobility shift experiments showed that IdeR binds to the fxbA regulatory region in the presence of divalent metals. DNase I footprinting assays indicated that IdeR binding protects a 28-bp region containing a palindromic sequence of the fxbA promoter that was identified in primer extension assays. fxbA regulation was measured in M. smegmatis wild-type and ideR mutant strains containing fxbA promoter-lacZ fusions. These experiments confirmed that fxbA expression is negatively regulated by iron and showed that inactivation of ideR results in iron-independent expression of fxbA. However, the levels of its expression in the ideR mutant were approximately 50% lower than those in the wild-type strain under iron limitation, indicating an undefined positive role of IdeR in the regulation of fxbA.