Expression of CD11c and EMR2 on neutrophils: potential diagnostic biomarkers for sepsis and systemic inflammation.

There is a need for cellular biomarkers to differentiate patients with sepsis from those with the non-infectious systemic inflammatory response syndrome (SIRS). In this double-blind study we determined whether the expression of known (CD11a/b/c, CD62L) and putative adhesion molecules [CD64, CD97 and epidermal growth factor (EGF)-like molecule containing mucin-like hormone receptor (EMR2)] on blood neutrophils could serve as useful biomarkers of infection and of non-infectious SIRS in critically ill patients. We studied 103 patients with SIRS, 83 of whom had sepsis, and 50 healthy normal subjects, using flow cytometry to characterize neutrophils phenotypically in whole blood samples. Patients with SIRS had an increased prevalence of neutrophils expressing CD11c, CD64 and EMR2 in comparison with healthy subjects (P < 0.001), but normal expression of CD11a, CD11b, CD62L and CD97. An increase in the percentage of neutrophils bearing CD11c was associated with sepsis, EMR2 with SIRS and CD64 with sepsis and SIRS. Neutrophils expressing CD11c had the highest sensitivity (81%) and specificity (80%) for the detection of sepsis, and there was an association between the percentage of neutrophils expressing EMR2 and the extent of organ failure (P < 0.05). Contrary to other reports, we did not observe an abnormal expression of CD11b or CD62L on neutrophils from patients with SIRS, and suggest that this discrepancy is due to differences in cell processing protocols. We propose that blood neutrophils expressing CD11c and EMR2 be considered as potential biomarkers for sepsis and SIRS, respectively.

Metabolic effects of intensive insulin therapy in critically ill patients.

Our aim was to investigate the effects of glycemic control and insulin concentration on lipolysis, glucose, and protein metabolism in critically ill medical patients. For our methods, the patients were studied twice. In study 1, blood glucose (BG) concentrations were maintained between 7 and 9 mmol/l with intravenous insulin. After study 1, patients entered one of four protocols for 48 h until study 2: low-insulin high-glucose (LIHG; variable insulin, BG of 7-9 mmol/l), low-insulin low-glucose (LILG; variable insulin of BG 4-6 mmol/l), high-insulin high-glucose [HIHG; insulin (2.0 mU . kg(-1).min(-1) plus insulin requirement from study 1), BG of 7-9 mmol/l], or high-insulin low-glucose [HILG; insulin (2.0 mU.kg(-1).min(-1) plus insulin requirement from study 1), BG of 4-6 mmol/l]. Age-matched healthy control subjects received two-step euglycemic hyperinsulinemic clamps achieving insulin levels similar to the LI and HI groups. In our results, whole body proteolysis was higher in patients in study 1 (P < 0.006) compared with control subjects at comparable insulin concentrations and was reduced with LI (P < 0.01) and HI (P = 0.001) in control subjects but not in patients. Endogenous glucose production rate (R(a)), glucose disposal, and lipolysis were not different in all patients in study 1 compared with control subjects at comparable insulin concentrations. Glucose R(a) and lipolysis did not change in any of the study 2 patient groups. HI increased glucose disposal in the patients (HIHG, P = 0.001; HILG, P = 0.07 vs. study 1), but this was less than in controls receiving HI (P < 0.03). In conclusion, low-dose intravenous insulin administered to maintain BG between 7-9 mmol/l is sufficient to limit lipolysis and endogenous glucose R(a) and increase glucose R(d). Neither hyperinsulinemia nor normoglycemia had any protein-sparing effect.

Neutrophils in development of multiple organ failure in sepsis.

Multiple organ failure is a major threat to the survival of patients with sepsis and systemic inflammation. In the UK and in the USA, mortality rates are currently comparable with and projected to exceed those from myocardial infarction. The immune system combats microbial infections but, in severe sepsis, its untoward activity seems to contribute to organ dysfunction. In this Review we propose that an inappropriate activation and positioning of neutrophils within the microvasculature contributes to the pathological manifestations of multiple organ failure. We further suggest that targeting neutrophils and their interactions with blood vessel walls could be a worthwhile therapeutic strategy for sepsis.

Outcomes, cost and long term survival of patients referred to a regional weaning centre.

BACKGROUND: Regional weaning centres provide cost effective care for patients who have undergone prolonged mechanical ventilation. There are few published European data on outcomes in these patients. METHODS: Patients admitted for weaning to the Lane Fox Respiratory Unit (LFU) between January 1997 and December 2000 were identified. The proportion weaned from mechanical ventilation, in-hospital mortality, and subsequent survival after discharge were examined. RESULTS: A total of 153 patients had been ventilated for a median of 26 days before transfer. The daily cost per patient stay was 1350. Fifty eight patients (38%) were fully weaned, 42 (27%) died, and 53 (35%) required ventilatory support at discharge from hospital of whom 36 (24%) required only nocturnal ventilation. Univariate analysis showed increasing age (OR 1.06, p<0.001), length of ICU stay (OR 1.02, p = 0.001), APACHE II predicted risk of death score (OR 1.02, p = 0.05), and a surgical cause for admission (OR 4.04) were associated with mortality. Neuromuscular/chest wall conditions were associated with low mortality (OR 0.36) but low likelihood of weaning from ventilation (OR 0.28). Female sex (OR 2.13, p = 0.03) and COPD (OR 2.81) were associated with successful weaning. Overall survival at 3 years from admission was 47%. Long term survival was lowest in patients with COPD. CONCLUSIONS: Most patients survived to leave hospital, the majority having been liberated from ventilatory support. Survivors were younger and spent less time ventilated in the referring ICU. The underlying diagnosis determined success of weaning, hospital survival, and long term outcome.

The pulmonary physician in critical care * 2: oxygen delivery and consumption in the critically ill.

Early detection and correction of tissue hypoxia is essential if progressive organ dysfunction and death are to be avoided. However, hypoxia in individual tissues or organs caused by disordered regional distribution of oxygen delivery or disruption of the processes of cellular oxygen uptake and utilisation cannot be identified from global measurements. Regional oxygen transport and cellular utilisation have an important role in maintaining tissue function. When tissue hypoxia is recognised, treatment must be aimed at the primary cause. Supplemental oxygen may be life saving in some situations but cannot correct inadequate oxygen delivery caused by a low cardiac output or impaired ventilation. Recent innovations include artificial oxygen carrying proteins and "haemoglobin" molecules designed to improve tissue blood flow by reducing viscosity. Regulating cell metabolism using different substrates or drugs has so far been poorly explored but is an exciting area for further research. A minimum level of global oxygen delivery and perfusion pressure must be maintained in the critically ill patient with established "shock", but advances in the understanding and control of regional distribution and other "downstream" factors in the oxygen cascade are needed to improve outcome in these patients.

The effects of leucodepletion in patients who develop the systemic inflammatory response syndrome following cardiopulmonary bypass.

The development of the systemic inflammatory response syndrome (SIRS) is associated with increased morbidity and mortality. Numerous anticytokine trials have failed to demonstrate any outcome benefit and there has been little evidence of improvement in the prognosis of this condition over the past 20 years. This study examines the effect of using a white cell filter designed to remove polymorphonuclear cells (PMNs) in patients who developed SIRS 36 h after cardiopulmonary bypass (CPB). Twenty-four patients were randomized to receive either leucofiltration (LF) or control therapy (CT). The two groups were well matched at study entry in terms of age, severity of illness and length of time on CPB. LF patients received 60 min filtration periods using a venovenous extracorporeal circuit at a flow rate of 200 ml/min with the cycle repeated every 12 h while SIRS and other entry criteria were met. CT patients received standard therapy. LF patients received an average of 4.2 cycles (range 1-8) and, after 15 min filtration, the total leucocyte count had fallen from 16.2 +/- 5.3 to 10.4 +/- 3.3 x 10(9)/l and PMN from 14.4 +/- 5.2 to 8.3 +/- 4.2 x 10(9)/l. The mean platelet count changed from 127 +/- 87 to 117 +/- 82 x 10(9)/l. No adverse effects related to leucodepletion were observed. There was no difference between the groups in either mortality or length of stay at the intensive care unit or at hospital discharge. Organ function was assessed regularly during the study period and significant changes occurred only in respiratory and renal function. In the LF patients, respiratory function assessed by change in hypoxaemia index from baseline and renal function assessed by serum creatinine showed significant treatment effects compared to CT patients (p < 0.01, < 0.01 respectively); three CT patients, but no LF patients, received haemofiltration during the study period. Leucofiltration safely and effectively removes circulating PMNs from patients with SIRS following CPB. This may result in improved pulmonary and renal function in these patients. Further studies are required of the kinetics and phenotypic characteristics of PMN removal by leucofiltration and a larger multicentre study will be necessary to determine whether this novel therapy has a significant outcome benefit in critically ill patients with SIRS.

Leucodepletion and the interaction of polymorphonuclear cells with endothelium in systemic inflammatory response syndrome.

The abnormal interaction of polymorphonuclear cells (PMNs) with blood vessel walls is considered to underlie the multiple organ failure of systemic inflammatory response syndrome (SIRS). This consideration is supported by the present finding that PMNs from patients with SIRS are activated, as assessed by an increased distribution of cells bearing CD64, enhanced expression of CD11b and decreased expression of CD62L, and are highly adhesive to endothelial monolayers. Passage of SIRS blood through leucodepletion filters in a laboratory-designed extracorporeal circuit resulted in a marked depletion of PMNs. Of the PMNs that remained in the blood, far fewer cells bound to cultured endothelial cells in comparison with PMNs prior to leucofiltration. We propose that leucofiltration of SIRS blood will limit the number of PMNs available for binding to blood vessel walls and, hence, reduce the pathological manifestations associated with this disorder.

Effects of glutamine supplementation, GH, and IGF-I on glutamine metabolism in critically ill patients.

During critical illness glutamine deficiency may develop. Glutamine supplementation can restore plasma concentration to normal, but the effect on glutamine metabolism is unknown. The use of growth hormone (GH) and insulin-like growth factor I (IGF-I) to prevent protein catabolism in these patients may exacerbate the glutamine deficiency. We have investigated, in critically ill patients, the effects of 72 h of treatment with standard parenteral nutrition (TPN; n = 6), TPN supplemented with glutamine (TPNGLN; 0.4 g x kg(-1) x day(-1), n = 6), or TPNGLN with combined GH (0.2 IU. kg(-1). day(-1)) and IGF-I (160 microg x kg (-1) x day(-1)) (TPNGLN+GH/IGF-I; n = 5) on glutamine metabolism using [2-(15)N]glutamine. In patients receiving TPNGLN and TPNGLN+GH/IGF-I, plasma glutamine concentration was increased (338 +/- 22 vs. 461 +/- 24 micromol/l, P < 0.001, and 307 +/- 65 vs. 524 +/- 71 micromol/l, P < 0.05, respectively) and glutamine uptake was increased (5.2 +/- 0.5 vs. 7.4 +/- 0.7 micromol x kg(-1) x min(-1), P < 0.05 and 5.2 +/- 1.1 vs. 7.6 +/- 0.8 micromol x kg(-1) x min(-1), P < 0.05). Glutamine production and metabolic clearance rates were not altered by the three treatments. These results suggest that there is an increased requirement for glutamine in critically ill patients. Combined GH/IGF-I treatment with TPNGLN did not have adverse effects on glutamine metabolism.

A 25-year study of nosocomial bacteremia in an adult intensive care unit.

OBJECTIVE: To identify the organisms, their antibiotic susceptibility, and the associated focus on infection causing nosocomial bacteremia in patients in an adult intensive care unit (ICU) between 1971 and 1995. DESIGN: Prospective observational study. SETTING: A 12-bed general adult ICU in a 1,000-bed tertiary referral teaching hospital. PATIENTS: Four hundred eighty-six episodes of bacteremia involving 570 organisms in 425 patients. MEASUREMENTS AND MAIN RESULTS: Blood cultures taken from patients with suspected nosocomial infection were analyzed. Isolated organisms were identified, and their susceptibility to commonly used antibiotics was determined. Clinical details, including antibiotic treatment, were recorded for all patients. From 1986 to 1995, culture results of samples obtained from other sites were used to help identify the focus of infection causing bacteremia. All results were collected prospectively by clinical microbiologists. Between 1971 and 1990, the number of bacteremias and the relative frequency of isolation of individual organisms changed little, with Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella species predominating. During 1991 to 1995, the number of bacteremias increased two-fold, largely attributable to increased isolation of Enterococcus species, coagulase-negative staphylococci, intrinsically antibiotic-resistant gram-negative organisms (particularly P. aeruginosa), and Candida species. The most commonly used antibiotics for the treatment of bacteremic patients throughout the 1970s were amoxicillin and gentamicin. After the introduction of cephalosporins in the early 1980s, their use increased progressively to equal that of gentamicin in the 1990s, whereas amoxicillin use decreased. Since the introduction of cephalosporins, increases in the antibiotic resistance of gram-negative organisms have been largely confined to an outbreak of gentamicin- and ceftazidime-resistant organisms caused by contaminated arterial pressure monitors during 1992 and 1993 and a two-fold increase in ceftazidime resistance of the Pseudomonas species. Gentamicin resistance of gram-negative aerobes remained unchanged (excluding the arterial pressure monitor outbreak), despite gentamicin being one of the most frequently prescribed antibiotics throughout the 25-yr period. Between 1986 and 1995, two thirds of all bacteremic organisms were cultured from intravascular catheters, which were designated as the focus of infection, 7% were secondary to gastrointestinal pathology, but only approximately 3% were secondary to wound, respiratory tract, or urinary tract infections. CONCLUSIONS: Bacteremias have become more frequent in the ICU, probably because of the increased use of intravascular catheters, which are the most frequent foci for bacteremic infection. The spectrum of organisms has changed, and this can be temporally related to the changes in the antibiotics prescribed. Gentamicin resistance of gram-negative organisms has not increased during a 25-yr period, despite being one of the most frequently prescribed antibiotics in the ICU.

The metabolic consequences of critical illness: acute effects on glutamine and protein metabolism.

Net protein loss and large decreases in plasma glutamine concentration are characteristics of critical illness. We have used [2-15N]glutamine and [1-13C]leucine to investigate whole body glutamine and leucine kinetics in a group of critically ill patients and matched healthy controls. Glutamine appearance rate (Ra,Gln) was similar in both groups. However, in the patients, the proportion of Ra,Gln arising from protein breakdown was higher than in the control group (43 +/- 3 vs. 32 +/- 2%, P < 0.05). Glutamine metabolic clearance rate (MCR) was 92 +/- 8% higher (P < 0.001), whereas plasma glutamine concentration was 38 +/- 5% lower (P < 0.001) than in the control group. Leucine appearance rate (whole body proteolysis) and nonoxidative leucine disposal (whole body protein synthesis) were 59 +/- 14 and 49 +/- 15% higher in the patients (P < 0.001). Leucine oxidation and MCR were increased in the patients by 104 +/- 37 and 129 +/- 39%, respectively (P < 0.05). These results demonstrate that critical illness is associated with a major increase in protein turnover. The acute decrease in plasma glutamine concentration and the unaltered plasma Ra,Gln suggest that the increase in proteolysis is insufficient to meet increased demand for glutamine in this severe catabolic state.

Relationship between TISS and ICU cost.

OBJECTIVE: To determine whether the therapeutic intervention scoring system (TISS) reliably reflects the cost of the overall intensive care unit (ICU) population, subgroups of that population and individual ICU patients. DESIGN: Prospective analysis of individual patient costs and comparison with TISS. SETTING: Adult, 12 bedded general medical and surgical ICU in a university teaching hospital. SUBJECTS: Two hundred fifty-seven consecutive patients including 52 coronary care (CCU), 99 cardiac surgery (CS) and 106 general ICU (GIC) cases admitted to the ICU during a 12-week period in 1994. A total of 916 TISS-scored patient days were analysed MAIN OUTCOME MEASURES: A variable cost (VC) that included consumables and service usage (nursing, physiotherapy, radiology and pathology staff costs) for individual patients was measured daily. Nursing costs were calculated in proportion to a daily nursing dependency score. A fixed cost (FC) was calculated for each patient to include medical, technical and clerical salary costs, capital equipment depreciation, equipment and central hospital costs. The correlation between cost and TISS was analysed using regression analysis. RESULTS: For the whole group (n = 257) the average daily FC was pound sterling 255 and daily VC was pound sterling 541 (SEM 10); range pound sterling 23-pound sterling 2,806. In the patient subgroups average daily cost (FC + VC) for CCU was pound sterling 476 (SEM 17.5), for CS pound sterling 766 (SEM 13.8) and for GIC pound sterling 873 (SEM 13.6). In the group as a whole, a strong correlation was demonstrated between VC and the TISS for each patient day (r = 0.87, p < 0.001) and this improved further when the total TISS score was compared with the total VC of the entire patient episode (r = 0.93, p < 0.001). This correlation was maintained in CCU, CS and GIC patient cohorts with only a small median difference between actual and predicted cost (2.2 % for GIC patients). However, in the individual patient, the range of error was up to +/- 65 % of the true variable cost. For the whole group the variable cost per TISS point was pound sterling 25. CONCLUSION: These results demonstrate that TISS reliably measures overall ICU population costs as well as those of the subgroups CCU, CS and GIC. However, the relationship between TISS and cost is less reliable for the individual patient.

Neurohypophysial hormone and melatonin secretion over the natural and suppressed menstrual cycle in premenopausal women.

OBJECTIVE: Vasopressin, oxytocin and melatonin have been reported to be influenced by ovarian steroids. The neurohypophysial hormones have also been shown to display a diurnal pattern of secretion in men. We therefore studied the diurnal pattern of neurohypophysial hormone and melatonin secretion in premenopausal women and in women on oral contraceptives. DESIGN: Healthy normally cycling premenopausal women were studied over 24 hours during the midfollicular and midluteal phases of the menstrual cycle. Healthy premenopausal women on oral contraceptives were studied over 24 hours at similar times. SUBJECTS: Eight healthy normally cycling women and 7 healthy premenopausal women on oral contraceptives. MEASUREMENTS: Plasma vasopressin, oxytocin and melatonin were measured by radioimmunoassay. RESULTS: Vasopressin concentrations and its nocturnal peak were highest in the follicular phase of the natural menstrual cycle and attenuated in the women on oral contraceptives. Oxytocin concentrations did not vary between the two phases of the menstrual cycle, but increased on oestrogen administration. Overall melatonin secretion was augmented in the women on oral contraceptives. CONCLUSIONS: Vasopressin release and its nocturnal peak were greatest in the follicular phase of the menstrual cycle, while melatonin secretion was augmented in the women on oral contraception.

Bicarbonate-based haemofiltration in the management of acute renal failure with lactic acidosis.

Continuous haemofiltration with lactate-based replacement fluid is widely used for the treatment of acute renal failure (ARF). In the presence of lactic acidosis, such treatment exacerbates rather than improves the clinical state. Continuous haemofiltration using a locally-prepared bicarbonate-based replacement fluid was performed in 200 patients over 7 years. All the patients had ARF with concomitant lactic acidosis, or demonstrated lactate intolerance after starting haemofiltration with lactate-based replacement fluids. In every case it was possible to correct the acidosis without inducing either extracellular volume expansion or hypernatraemia. In 89 patients (45%), the lactic acidosis resolved while being treated with bicarbonate-based haemofiltration. Fifty-seven patients (28.5%) survived. Significant differences at presentation in the group who survived, compared with those who died, were seen in age (50.8 vs. 57.1), mean arterial pressure (68.5 vs. 60.0 mmHg) and APACHE II score (32.1 vs. 38.9). Neither the severity of the presenting acidosis nor the arterial blood lactate appeared to predict outcome. Patients who developed ARF and lactic acidosis after cardiac surgery had a low survival rate. The combination of ARF and lactic acidosis that cannot safely be treated by haemofiltration using lactate-based replacement fluids can be managed with bicarbonate-based haemofiltration.

Daily patterns of secretion of neurohypophysial hormones in man: effect of age.

The neurohypophysial hormone vasopressin contributes to control of urine output and, while urine flow shows a clear daily rhythm, there has been debate as to whether this is true of neurohypophysial hormones. A study was performed on fifteen adult males, with a mean age of 25 years, over a 24 h period, nine blood samples being taken at regular intervals for the determination of neurohypophysial hormones and indices of fluid balance. Samples were taken via an indwelling cannula so that sleep was undisturbed. A daily variation in the plasma concentrations of oxytocin and vasopressin was demonstrated with concentrations reaching a nadir in the late afternoon. Concentrations of both hormones peaked at 02.00 h. Vasopressin concentrations were inversely correlated with packed cell volume, indicating that the altered hormone release was affecting fluid retention. Consistent with this was the observation that the relationship of plasma osmolality to vasopressin depended on the time of day. To determine the effect of ageing, a similar study was performed on nine healthy elderly subjects with a mean age of 70 years. The nocturnal peak of vasopressin was markedly attenuated, while oxytocin release was similar to that in the younger group. These observations confirm the existence of a daily rhythm in the plasma concentrations of neurohypophysial hormones and indicate that the amplitude of the vasopressin change decreases with age.

Melatonin administration and pituitary hormone secretion.

OBJECTIVE: The relationship between the pineal gland and pituitary function remains controversial, while the role of melatonin in the adaptation of the organism to the light-dark cycle of the environment is becoming increasingly recognized. The aim of this study was to investigate the effect of a manipulation of the melatonin rhythm on pituitary hormone secretion in man. DESIGN: Double-blind controlled clinical study. SUBJECTS: Ten adult healthy male volunteers, aged 21-33 years, were studied on two occasions: once after the administration of melatonin 5 mg orally for 4 days at 1700 hours and once after the administration of placebo, at similar times. On the day of each study the subjects undertook their normal duties but refrained from taking heavy exercise, from smoking and drinking alcohol. MEASUREMENTS: Serum cortisol, growth hormone, prolactin and plasma vasopressin, oxytocin, melatonin, sodium, potassium, osmolality and packed cell volume were measured over the following 24 hours. RESULTS: The cortisol peak was advanced and prolactin release increased after melatonin administration, while growth hormone was not affected. Vasopressin and oxytocin levels were found to increase during the night in the control study, but the period of the nocturnal increase in vasopressin concentrations was reduced after the administration of melatonin and the nocturnal increase of oxytocin was absent. CONCLUSION: Altering the melatonin rhythm may affect neuroendocrine function, influencing the nocturnal pattern of neurohypophysial hormone secretion, augmenting prolactin release and advancing the peak of cortisol release.