Plasma antioxidant potential in severe sepsis: a comparison of survivors and nonsurvivors.

OBJECTIVE: To determine the plasma antioxidant potential of patients in the intensive care unit (ICU) with severe sepsis and secondary organ dysfunction and relate these findings to outcome. DESIGN: A prospective, cohort study. SETTING: A nine-bed ICU in a university teaching hospital. PATIENTS: Fifteen consecutive patients, who were within 16 hrs of development of severe sepsis and secondary organ dysfunction. INTERVENTIONS: Plasma samples were obtained within 16 hrs of the onset of secondary organ dysfunction and subsequently on days 2, 3, 4, 6, 8, 10, and 15 until patients either left the ICU or died. Plasma antioxidant potential was determined by an ultraviolet spectrophotometric technique. MEASUREMENTS AND MAIN RESULTS: The mean initial plasma antioxidant potential was lower than our range for healthy volunteers (p < .05). Survivors had an initial plasma antioxidant potential that was greater than nonsurvivors (p < .01), and serial subset analysis demonstrated that survivors, despite having a low initial plasma antioxidant potential rapidly attained normal or supranormal values. While plasma antioxidant potential also increased in nonsurvivors over time, values in this subset never reached the normal range and remained below values in survivors at all time points studied (p < .05). CONCLUSIONS: Plasma antioxidant potential is initially decreased in patients with sepsis who develop organ dysfunction, and it increases over time. While we have no clear evidence to prove that this reduction has a causal relationship, failure to achieve a normal plasma antioxidant potential is strongly associated with an unfavorable outcome.

The effect of anticoagulant choice on apparent total antioxidant capacity using three different methods.

We assessed total antioxidant capacity using three different methods, in plasma samples treated with either EDTA or heparin as anticoagulant, from 26 healthy subjects. Total antioxidant capacity was determined using an oxygen electrode (as the total peroxyl radical-trapping antioxidant parameter), by enhanced chemiluminescence, and by measurement of the antioxidant-mediated quenching of the absorbance of a radical cation. The choice of anticoagulant had a profound effect on antioxidant capacity with heparinized plasma giving consistently higher values than plasma anticoagulated with EDTA. Using the oxygen electrode the mean value was 786.5 +/- 171.5 mumol/L (heparin) compared to 681.4 +/- 160.4 mumol/L (EDTA, P < 0.01). The chemiluminescence technique gave a mean antioxidant capacity of 915.6 +/- 214.1 mumol/L in heparin samples and 714.4 +/- 195.4 mumol/L in EDTA samples (P < 0.0001). The absorbance quenching technique gave a mean value of 867.0 +/- 199.2 mumol/L (heparin) and 675.5 +/- 245.4 mumol/L (EDTA, P < 0.001). All methods tested showed comparable results for EDTA plasma, but the chemiluminescence technique gave higher apparent antioxidant capacity than either of the two techniques when heparin plasma was used. We suggest that either heparin is interacting to enhance antioxidant protection perhaps through release of superoxide dismutase, or the chelation of metal ions by EDTA is limiting the activity of antioxidant metalloenzymes. Consistency in the choice of anticoagulant is clearly extremely important.

Decreased antioxidant status and increased lipid peroxidation in patients with septic shock and secondary organ dysfunction.

OBJECTIVE: To determine antioxidant vitamin concentrations, lipid peroxidation, and an index of nitric oxide production in patients in the intensive care unit (ICU) with septic shock and relate the findings to the presence of secondary organ failure. DESIGN: A prospective, observational study. SETTING: A nine-bed ICU in a University teaching hospital. PATIENTS: Sixteen consecutive patients with septic shock, defined as: a) clinical evidence of acute infection; b) hypo- or hyperthermia (< 35.6 degrees C or > 38.3 degrees C); c) tachypnea (> 20 breaths/min or being mechanically ventilated); d) tachycardia (> 90 beats/min); e) shock (systolic pressure < 90 mm Hg) or receiving inotropes. Fourteen patients also had secondary organ dysfunction. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Antioxidant vitamin concentrations were significantly lower in the patients than the reference range obtained from a comparable group of healthy controls. The mean plasma retinol (vitamin A) concentration was 26.5 +/- 19.3 micrograms/dL compared with 73.5 +/- 18.3 micrograms/dL in healthy subjects (p < .01). Additionally, 13 (81%) patients had retinol values below the lower limit of our reference range (< 37.0 micrograms/dL). Tocopherol (vitamin E) plasma concentrations were below the reference range in all patients (< 9.0 mg/L), with a mean value of 3.6 +/- 2.0 mg/L compared with 11.5 +/- 1.3 mg/L in healthy subjects (p < .001). Plasma beta carotene and lycopene concentrations were undetectable (< 15 micrograms/L) in eight (50%) patients, and below our reference range (< 101 micrograms/L and < 154 micrograms/L, respectively) in the remaining patients. In the five patients with three or more dysfunctional secondary organs, plasma thiobarbituric acid-reactive substances were significantly increased (p < .05), suggesting increased lipid peroxidation. Concentrations of thiobarbituric acid-reactive substances correlated negatively with both plasma retinol and plasma tocopherol (r2 = .42, p < .01 and r2 = .48, p < .005, respectively). In the five patients from whom we were able to collect urine, nitrite excretion was increased approximately 400-fold (p < .001). CONCLUSIONS: These data indicate decreased antioxidant status in the face of enhanced free radical activity, and suggest potential therapeutic strategies involving antioxidant repletion.

Nitric oxide synthase activity is increased in patients with sepsis syndrome.

1. We measured nitric oxide synthase activity in peripheral blood polymorphonuclear leucocytes from 10 patients with sepsis syndrome and 10 healthy subjects. 2. Synthase activity was significantly higher in patients with sepsis than in control subjects (1202 +/- 579 compared with 595 +/- 544 pmol of nitric oxide min-1 mg-1 of cell protein, P < 0.05). 3. Activity was greatest in those patients with the larger number of organ failures, although this failed to reach significance (1489 +/- 560 in patients with three or more organ failures and 843 +/- 404 pmol of nitric oxide min-1 mg-1 of cell protein in those with less than three, P = 0.11). 4. This study provides evidence for the role of overproduction of the vasodilator nitric oxide in sepsis syndrome.

Nitric oxide production by human peripheral blood polymorphonuclear leucocytes.

1. We describe a rapid and reliable technique for the assessment of basal nitric oxide release in clinical situations, using peripheral blood polymorphonuclear leucocytes isolated by a single-step density gradient procedure. The assay is based on the quantitative conversion of oxyhaemoglobin to methaemoglobin by nitric oxide. We have further examined the ability of these cells to respond to various stimuli. 2. Basal (unstimulated) nitric oxide release occurred, which was augmented by superoxide dismutase. The mean value for healthy subjects was 283 +/- 96.7 pmol min-1 10(-6) cells. 3. Both phorbol myristate acetate and N-formyl-methionyl-leucylphenylalanine induced further release of nitric oxide, which was increased by preincubation with lipopolysaccharide, interleukin-6 and interferon-gamma. 4. Preincubation of cells with NG-monomethyl-L-arginine or L-canavanine sulphate inhibited nitric oxide production. 5. The procedure provides a valuable tool for monitoring nitric oxide up-regulation in clinical situations.

Reperfusion injury, antioxidants and hemodynamics during orthotopic liver transplantation.

Endothelial injury occurs as a result of oxygen free radical production after ischemia and reperfusion of transplanted livers, causing hemodynamic disturbance. Patients with chronic liver disease generally have low levels of fat-soluble vitamins, which have important antioxidant roles. We therefore assessed circulating levels of the antioxidants vitamin A, vitamin E, beta-carotene and lycopene, indices of lipid peroxidation and hemodynamic changes during elective orthotopic liver transplantation in 12 patients. We found that initial antioxidant levels were severely depleted compared with healthy subjects, and in some patients carotene and lycopene levels were undetectable. Increased lipid peroxidation was also evident, as shown by thiobarbituric acid-reactive substances. On reperfusion of the liver graft, vitamin A and E levels fell (p < 0.01) and were associated with decreases in systemic vascular resistance (p < 0.02). These data show that patients undergoing liver transplant have lowered antioxidant defenses and evidence of free radical damage, which compound the additional insult of reperfusion injury. Antioxidant therapy in these patients before transplantation may ameliorate the effects of reperfusion.

Free radicals and antioxidants in sepsis.

OBJECTIVES: The clinical condition of sepsis is caused by the release of numerous mediators from many cells. The purpose of this review is to describe the results of studies in which the role of free radicals and/or the potential therapeutic value of antioxidants are assessed. DATA SOURCES: The studies described in this review come from a variety of sources, including Med-Line CD-ROM computerized database, Index Medicus, and references identified from the bibliographies of pertinent articles and books. Reports were confined to English language articles from 1966 to 1992. STUDY SELECTION: All retrieved references in which free-radical activity was assessed or antioxidants were measured or administered in sepsis or endotoxemia were included. This selection process encompassed clinical, animal and in vitro cell culture work. DATA EXTRACTION: Cited literature was found in reputable peer-reviewed clinical or basic science journals. DATA SYNTHESIS: Any contradictions in the results of studies are discussed. CONCLUSIONS: There is evidence that free radicals play an important role in the pathogenesis of sepsis. Antioxidant therapy has the potential to protect against such injury. It is suggested that combination therapy, which augments the endogenous antioxidant defenses, is likely to be the best approach.

Correction of cellular zinc depletion by oral zinc supplementation in elderly subjects.

Immune function declines with age, and has been implicated in the increased incidence of cancer and infections in the elderly. In this hospital, many elderly patients have evidence of zinc depletion. In the present study, we supplemented those elderly patients who had depressed polymorphonuclear cell (PMNC) zinc levels with 135 mg oral zinc sulphate for 4 weeks. Plasma and PMNC zinc increased markedly but the percentage of peripheral blood T-lymphocytes expressing the surface markers CD3, CD4 and CD8 were unchanged. Plasma concentrations of vitamins A and E also remained constant. This study confirms the 25-30% incidence of cellular zinc depletion in this patient population, and demonstrates that zinc concentrations can be brought back to within normal limits by oral zinc supplements, but with no effect on T-cell phenotypes.

Vitamin C depletion and pressure sores in elderly patients with femoral neck fracture.

OBJECTIVE: To evaluate the contribution of specific nutritional deficiencies (as indicated by zinc; vitamin A, C, and E; albumin; and haemoglobin concentrations) to the risk of pressure sores. DESIGN: Observational cohort study. SETTING: St James's University Hospital, Leeds. SUBJECTS: 21 elderly patients presenting consecutively to the orthopaedic unit with femoral neck fracture. MAIN OUTCOME MEASURE: Full thickness epidermal break over a pressure bearing surface. RESULTS: 10 patients (48%) developed a pressure sore during their hospital stay. Indices of zinc status and concentrations of albumin, haemoglobin, and vitamins A and E were similar in patients who developed a pressure sore and those who did not. Mean leucocyte vitamin C concentration, however, was 6.3 (SD 2.2) micrograms/10(8) cells in patients who developed a pressure sore as compared with 12.8 (4.6) micrograms/10(8) cells in patients who did not. CONCLUSIONS: Low concentrations of leucocyte vitamin C appear to be associated with subsequent development of pressure sores in elderly patients with femoral neck fractures.

Symptomatic zinc deficiency in experimental zinc deprivation.

An evaluation of indices of poor zinc status was undertaken in five male subjects in whom dietary zinc intake was reduced from 85 mumol d-1 in an initial phase of the study to 14 mumol d-1. One of the subjects developed features consistent with zinc deficiency after receiving the low zinc diet for 12 days. These features included retroauricular acneform macullo-papular lesions on the face, neck, and shoulders and reductions in plasma zinc, red blood cell zinc, neutrophil zinc and plasma alkaline phosphatase activity. Alcohol induced hepatitis, which was suspected in this subject, may have caused a predisposition to altered zinc metabolism and possible zinc deficiency which was exacerbated by subsequent zinc deprivation. The report supports the value of neutrophil zinc concentration as an indicator of poor zinc status.

Evidence of cellular zinc depletion in hospitalized but not in healthy elderly subjects.

Cellular immune function declines with age and is implicated in the increased incidence of cancer, and morbidity and mortality associated with infections in elderly people. Elderly people are at risk of nutritional depletion, including of zinc, and zinc is known to influence immunity. The present study assessed zinc status in both healthy elderly subjects and elderly inpatients. Polymorphonuclear-cell zinc was decreased in the hospitalized subjects and 27% had values below the reference range for healthy elderly and young subjects. Since PMNC zinc is decreased in experimental zinc depletion and correlates with muscle zinc, we suggest that 27% of the patients studied may be zinc depleted and may benefit from zinc supplementation.

Effect of fasting, self-selected and isocaloric glucose and fat meals and intravenous feeding on plasma zinc concentrations.

This study investigated the effect of fasting, self-selected meals and isocaloric oral glucose and fat meals and intravenous (i.v.) feeding on plasma zinc concentrations in men. Plasma zinc remained stable when volunteers fasted all day, but self-selected meals and 600 kCal of dextrose or fat emulsion caused significantly reduced plasma zinc concentrations [mean (SD) 12.1 (1.4), 12.3 (0.6) and 12.2 (0.7) mumol/L at 1400 h, respectively, compared with a fasting level of 13.9 (1.6) mumol/L at 0800 h, P less than 0.05]. In patients undergoing intravenous hyperalimentation, plasma zinc decreased from 12.0 (1.4) mumol/L at 0800 h to 10.0 (1.1) mumol/L at 1400 h [mean (SD), P less than 0.01]. These data show that both enteral and i.v. feeding cause a decline in plasma zinc and that glucose alone is not responsible for this post-prandial fall since ingestion of isocaloric amounts of glucose or fat have a similar effect.

The effect of dietary vitamin E deficiency on plasma zinc and copper concentrations.

Vitamin E and zinc have a number of functions in common, including membrane stabilisation, antioxidant function and modulation of prostaglandin metabolism. Previous studies have shown vitamin E malabsorption during zinc depletion and it appears that there is an interaction between the two nutrients. In this study we have investigated whether vitamin E deficiency affects zinc and copper concentrations in experimental animals. Male Wistar rats were maintained on a vitamin E deficient diet for either 6 or 10 months. At the end of the experimental period all animals had undetectable plasma vitamin E levels and increased red cell fragility. Plasma zinc concentrations were significantly reduced in all vitamin E deficient animals compared to control rats (p<0.002) and copper levels were reciprocally elevated (p<0.002). It appears likely that decreased zinc levels may represent redistribution of circulating zinc to tissues and cells as a secondary antioxidant, or for membrane stabilisation or prostaglandin synthesis.

Monocyte zinc and in vitro prostaglandin E2 and interleukin-1 beta production by cultured peripheral blood monocytes in patients with Crohn's disease.

This study investigated the relationship between zinc status and prostaglandin E2 and interleukin-1 beta production by cultured monocytes in patients with Crohn's disease. Monocyte zinc was significantly decreased in both 12 inpatients and 22 outpatients compared with controls (P less than 0.001) but lymphocyte and polymorphonuclear cell zinc were normal. When cultured monocytes from 10 outpatients with Crohn's disease were stimulated with lipopolysaccharide, prostaglandin E2 production increased markedly, coupled with a fall in monocyte zinc. In matched controls, prostaglandin E2 production was significantly less and monocyte zinc remained stable. No difference in interleukin-1 release was noted between patients and controls. The addition of prednisolone to cell cultures suppressed prostaglandin E2, interleukin-1 synthesis, and monocyte zinc did not change. Zinc chloride augmented prostaglandin E2 production in patients, but not controls, and interleukin-1 remained stable. These results demonstrate a link between low monocyte zinc concentration and excessive prostaglandin production in patients with Crohn's disease.

The effects of acute infection on indices of zinc status.

Various indices of zinc status were assessed in 12 patients with acute urinary tract or chest infections on Day 1 and Day 7 of the infection. Leucocyte counts were raised on Day 1 but had returned to near normal by Day 7. Plasma zinc was decreased on Day 1 in conjunction with depressed plasma albumin concentrations (r = 0.71, p < 0.001) but both had returned to normal by Day 7. Mononuclear cell zinc was raised in all patients on Day 1 compared to Day 7 and control values, but polymorphonuclear cell zinc remained unchanged. However, polymorphonuclear cell alkaline phosphatase activity was grossly increased on Day 1 and correlated with leucocyte count (r = 0.61, p < 0.01). Plasma alkaline phosphatase activity was variable. These results indicate that in patients with infections measurement of plasma mononuclear cell zinc concentration and alkaline phosphatase activity are misleading indicators of zinc status. Polymorphonuclear cell zinc is unaffected by leucocytosis, inflammation and stress and may therefore provide a more reliable index of zinc status in such patients.

Cellular and muscle zinc in surgical patients with and without gastrointestinal cancer.

1. The zinc status of surgical patients with and without gastrointestinal cancer was studied. 2. Plasma zinc was lowest in patients with cancer concurrent with depressed plasma albumin concentrations. 3. Polymorphonuclear cell zinc was decreased in both patient groups and correlated strongly with abdominal muscle zinc (r = 0.89, P less than 0.001). 4. Mononuclear cell and total leucocyte zinc were similar to control values in both groups of patients. Total leucocyte, but not mononuclear cell, zinc correlated weakly with muscle zinc (r = 0.48, P less than 0.05). 5. The results suggest that polymorphonuclear cell zinc may be better than leucocyte zinc in assessing zinc status and that some surgical patients may be zinc-depleted. The presence of gastrointestinal cancer did not influence the zinc status.

Relation between zinc status and hepatic functional reserve in patients with liver disease.

Patients with liver disease may be at risk of zinc depletion. We measured polymorphonuclear cell, mononuclear cell, plasma, and erythrocyte zinc values, and erythrocyte carbonic anhydrase activity to assess zinc status in 17 patients with non-alcoholic liver disease (primary biliary cirrhosis and chronic active hepatitis) and 13 patients with alcoholic liver disease. The plasma zinc concentration was reduced in both patient groups and correlated strongly with the plasma albumin concentration. The mean polymorphonuclear cell zinc value in both groups was similar to that of controls but when results were combined and grouped according to hepatic functional reserve, patients with more severe liver damage (grade C) had a lower polymorphonuclear cell zinc value (mean (SD) 0.86 (0.24) nmol/mg protein) than patients with grade A (1.44 (0.43) nmol/mg protein, p less than 0.01) or grade B liver damage (1.08 (0.30) nmol/mg protein, p less than 0.05), or control subjects (1.26 (0.28) nmol/mg protein, p less than 0.001). The polymorphonuclear cell zinc value did not correlate with other indices of zinc status. The mononuclear cell zinc value was normal in all patients and was unrelated to hepatic damage. The erythrocyte zinc value and carbonic anhydrase activity were raised in alcoholic patients only. Since the polymorphonuclear cell zinc concentration is low in human experimental zinc deficiency and also correlates with tissue zinc, we suggest that our results provide evidence of progressive leucocyte zinc depletion in patients with liver disease.

Zinc concentrations in pure populations of peripheral blood neutrophils, lymphocytes and monocytes.

It is doubtful if the measurement of plasma or serum zinc is of value in assessing zinc status. Leucocyte zinc has been suggested as an alternative since it may be representative of tissue zinc stores; but in many studies poorly defined cell populations make interpretation difficult. This paper describes detailed techniques for the isolation and analysis of pure populations of neutrophils, lymphocytes and monocytes. Zinc concentrations (+/- 1SD) in normal subjects were 1.26 +/- 0.27 nmol/mg protein, 1.85 +/- 0.32 nmol/mg protein and 2.58 +/- 0.65 nmol/mg protein in neutrophils, lymphocytes and monocytes respectively. Fasting caused a significant decrease in neutrophil and lymphocyte zinc, and an increase in monocyte zinc. Supplementation of zinc-replete subjects with 135 mg zinc/day for 3 weeks had no significant effect on cellular zinc concentrations.

Essential element nutritional status in cystic fibrosis.

Serum calcium, magnesium, iron, copper and zinc were measured in 117 patients with cystic fibrosis. Apart from serum iron levels, all the other essential element levels were well maintained and there was no evidence of a need for supplementation. Serum iron was frequently low and the need for iron supplements must be considered after further investigation. The subjects studied covered a wide age range, had widely varying fat malabsorption and clinical grading, and also varying degrees of pulmonary involvement. We found no evidence that any of these parameters directly influenced essential element status as assessed by serum levels.