Clinical features and disease progression of elderly patients at the ICU setting

OBJECTIVE

To describe and characterize a cohort of octogenarian patients admitted to the ICU of the University Central Hospital of Asturias (HUCA).

DESIGN

Retrospective, observational and descriptive study of 14 months' duration.

SETTING

Cardiac and Medical intensive care units (ICU) of the HUCA (Oviedo).

PARTICIPANTS

Patients over 80 years old who were admitted to the ICU for more than 24 h.

INTERVENTIONS

None.

MAIN VARIABLES OF INTEREST

Age, sex, comorbidity, functional dependence, treatment, complications, evolution, mortality.

RESULTS

The most frequent reasons for admission were cardiac surgery and pneumonia. The average admission stay was significantly longer in patients under 85 years of age (p = 0,037). 84,3% of the latter benefited from invasive mechanical ventilation compared to 46,2% of older patients (p = <0,001). Patients over 85 years of age presented greater fragility. Admission for cardiac surgery was associated with a lower risk of mortality (HR = 0,18; 95% CI (0,062-0,527; p = 0,002).

CONCLUSIONS

The results have shown an association between the reason for admission to the ICU and the risk of mortality in octogenarian patients. Cardiac surgery was associated with a better prognosis compared to medical pathology, where pneumonia was associated with a higher risk of mortality. Furthermore, a significant positive association was observed between age and frailty.

Calcium, phosphorus, PTH and death rates in a large sample of dialysis patients from Latin America. The CORES Study

BACKGROUND

Mineral metabolism parameters may play a role in the survival of patients with chronic kidney disease (CKD).

METHODS

In the CORES Study, we analysed the association between calcium, phosphorus and PTH and mortality (all-cause and cardiovascular) in 16 173 haemodialysis (HD) patients over 18 years from six Latin American countries, who underwent haemodialysis up to 54 months. Unadjusted, case-mix-adjusted and time-dependent multivariable-adjusted hazard ratio (HR) of death were calculated for categories of serum albumin-corrected calcium (Ca(Alb)), phosphorus and PTH using as 'reference values' the range in which the lowest death rate was observed. Age, gender, vitamin D treatment, diabetes, vintage, vascular access, weight, blood pressure and laboratory variables (serum albumin, haemoglobin, creatinine, ferritin and Kt/V) were used as confounding variables.

RESULTS

Low (<9.5 mg/dL) and high (>10.5 mg/dL) Ca(Alb) increased the HR for all-cause mortality. Low (<9.0 mg/dL) Ca(Alb) increased the HR for cardiovascular mortality. High phosphorus (>5.5 mg/dL) increased the HR for both all-cause and cardiovascular mortality. Low phosphorus (<4.0 and <3.0 mg/dL) increased the HR for both all-cause and cardiovascular mortality. Furthermore, low (<150 pg/mL) and high (>500 and >300 pg/mL) PTH increased the HR for both all-cause and cardiovascular mortality. In addition, only phosphorus >6.0 mg/dL increased the HR for cardiovascular hospitalizations. No effect was observed with Ca(Alb) or PTH.

CONCLUSIONS

In summary, in 16,173 HD patients, elevated and reduced serum levels of albumin-corrected calcium, phosphorus and PTH levels were associated with increments in all-cause mortality. Similar results were obtained when only cardiovascular mortality was analysed.

Effect of aluminium load on parathyroid hormone synthesis

BACKGROUND

Aluminium overload leads to parathyroid hormone (PTH) suppression. However, it is unclear whether a decrease in synthesis or release of the hormone is mainly involved. The aim of this study was to assess the effect of an acute administration of aluminium on PTH synthesis and release in rats with chronic renal failure and secondary hyperparathyroidism.

METHODS

The study was performed using 100 adult male Wistar rats (body weight 443+/-54 g). 7/8 nephrectomy was performed and the rats were maintained on a high dietary phosphorous intake. Five weeks after surgery, the rats were randomly divided into two groups, one loaded with aluminium (AlCl3) and the other given placebo. Aluminium or placebo were administered i.p. for two consecutive days. The placebo group received saline at the same pH as the aluminium solution. After 2 weeks, serum calcium, phosphorous, creatinine, PTH, and aluminium were measured. The parathyroid glands were removed and PTH messenger RNA (mRNA) was measured by northern blot. Intact PTH was measured by IRMA (Rat PTH, Nichols Institute).

RESULTS

No differences in serum PTH levels were found between the two groups after 5 weeks of renal failure. At the end of the study the rats given aluminium had higher aluminium levels than the placebo group and lower PTH levels. No significant differences were found for calcium, phosphorous, renal function, or body weight. PTH mRNA expression was lower in the aluminium group than in the placebo group.

CONCLUSION

The administration of aluminium in rats with chronic renal failure resulted in reductions in serum PTH and PTH mRNA. Thus far, previous studies had demonstrated that aluminium suppressed PTH release. The present findings suggest that PTH synthesis is also reduced.

Bone aluminum uptake in uremic rats receiving intraperitoneal iron

To assess the effect of concomitant iron and aluminum loads on bone aluminum accumulation and on the response to the deferoxamine test in rats with the same aluminum surcharge, Wistar rats with chronic renal failure were divided into three groups: iron-overloaded rats (N = 6) (intraperitoneal iron); iron-depleted rats (N = 6) (blood withdrawal two to three times per week); control rats (N = 4) (no manipulation). All groups received intraperitoneal aluminum simultaneously. After 6 wk, a deferoxamine challenge test was performed. Thereafter, bone aluminum and iron were measured. The iron-overloaded rats showed higher bone iron content (iron overloaded: 147.7+/-55.4 microg/g; iron depleted: 7.9+/-1.0, and controls 13.3+/-9.9 microg/g, p < 0.010) and lower bone aluminum content (iron overloaded: 14.2+/-4.0 microg/g; iron depleted: 70.9+/-35.1 microg/g; controls: 72.7+/-28.3 microg/g p < 0.005). No differences were found between the iron-depleted and control rats. After the deferoxamine infusion, the iron-depleted rats tended to have higher serum aluminum increments (p = NS) and higher urinary aluminum excretion (p < 0.012, p < 0.020) than control rats despite similar amounts of aluminum in bone of the two groups. Aluminum bone accumulation was minor if iron and aluminum loads were given concomitantly. The iron depletion influenced the results of the deferoxamine challenge test in rats with similar bone aluminum burden.

Use of ultrafiltration and chromatography to assess aluminum speciation in serum after deferoxamine administration

Deferoxamine effectively chelates aluminum by forming aluminoxamine, a low-molecular-weight compound removable by dialysis. However, aluminum-bound species other than aluminoxamine might be present in serum after the administration of deferoxamine. To study aluminum speciation after the administration of deferoxamine, high-performance liquid chromatography (HPLC) and ultrafiltration techniques were used. Samples of serum were obtained from six dialysis patients 44 hours after the administration of a single dose of deferoxamine. HPLC and ultrafiltration studies were performed. In the HPLC studies, samples underwent ultrafiltration, the filtrate was injected into the chromatographic system, and detection was performed by UV light and atomic absorption spectrometry. Unknown species of aluminum other than aluminoxamine were found in the early elution fractions. In the ultrafiltration studies, the same samples of serum from the six patients underwent ultrafiltration using membranes with different molecular-weight cutoff values from 1 to 30 kd. The percentages of aluminum found by ultrafiltration using membranes with cutoff values of 5, 10, and 30 kd were greater (64.4% +/- 2.5%, 63.5% +/- 3.7%, and 65.6% +/- 4.3%, respectively) than the percentages obtained with membranes with a 1-kd cutoff value (38.7%), suggesting that the unknown species of aluminum have a molecular weight between 1 and 5 kd. The unknown species of aluminum cannot be aluminoxamine because they behaved in a different way with HPLC.

Aluminum exposure in chronic renal failure in iberoamerica at the end of the 1990s: overview and perspectives

Epidemic aluminum neurotoxicity has virtually disappeared in the dialysis population; however, sporadic toxic effects caused by contamination of water with aluminum are still reported. In this review, the current situation in Iberoamerica is analyzed. Exposure to aluminum through dialysate shows considerable geographical differences even within the same country, including seasonal variability. Sometimes the tap water showed very high aluminum content that does not permit the water treatment system to efficiently remove all the aluminum, forcing the use of water treatment systems with a double reverse-osmosis filter on line. The use of adequate water treatment systems and a correct control policy has improved the quality of the dialysate, minimizing the aluminum exposure. However, an additional problem in Iberoamerica is the difficulty to obtain aluminum-free concentrates for the preparation of the final dialysis solution. Aluminum still seems to be implicated in a great percentage of symptomatic low-bone remodeling lesions in South America compared with Europe, demonstrating that exposure to aluminum through dialysate is still a cause of concern in some areas of the world.

Aluminum-induced osteogenesis in osteopenic rats with normal renal function

Previous studies have shown a different effect of aluminum (Al) on bone metabolism in animals with chronic renal failure and conversely, positive osteogenic effects in animals with normal renal function. The aim of this study was to evaluate the effect of aluminum on bone metabolism in osteopenic rats. We studied male Wistar rats with severe osteopenia induced by adding NH4Cl (2%) to the drinking water over a 6-month period. The rats were divided into two groups and followed for 4 months. The Aluminum group (G1) received AlC13 intraperitoneally (10 mg/kg/5 days/week) (n = 8); the Control group (G2) did not receive any treatment after stopping the administration of NH4Cl (n = 5). In all animals we measured biochemical markers (serum Ca, P, Cr, Al, osteocalcin, hydroxyproline) as well as bone mineral density and bone histomorphometry (BV/TV, CTh, ObS/BS, OTh, and NOc/TV). Bone aluminum content, measured by atomic absorption spectrometry, was 101.6 +/- 13 microg/g in the Al overloaded group and 1.31 +/- 0.14 in controls. Bone mineral density, evaluated by dual X-ray absorptiometry (DXA) at the proximal extremity of the tibia was significantly higher in G1 (0.292 +/- 0.01 g/cm2 versus 0. 267 +/- 0.02 g/cm2). No significant differences were found between the biochemical markers. In the histomorphometric parameters we observed significant differences in G1 compared with G2: an increase in BV/TV (18.59 +/- 5.6 versus 7.69 +/- 3.08%) and in CTh (0.52 +/- 0.06 versus 0.36 +/- 0.07 mm) with a moderate increment of the osteoid thickness (14.05 +/- 4.72 versus 5.25 +/- 0.9 microm) (P < 0. 05). Changes in others parameters and the relationship between biochemical parameters of bone remodeling, Al, and histology were analyzed. These findings indicate that in rats with normal renal function, Al is able to induce bone formation even when osteopenia is present.

Low percentage of aluminoxamine and ferrioxamine in uremic serum after desferrioxamine administration

HPLC was used to study the effectiveness of two different desferrioxamine (DFO) administration strategies (15 mg/kg DFO, 1 h or 44 h before dialysis) on generation of aluminoxamine and ferrioxamine in five hemodialysis patients. The percentage of ultrafilterable aluminum and iron in these patients was also investigated by electrothermal atomic absorption spectrometry. The administration of DFO in both schemes increased the ultrafilterable serum aluminum concentrations from a mean of 17.1 +/- 1.6% to a mean of 75.7 +/- 14.1%. However, 1 h after DFO infusion, only 38.8 +/- 7.7% of the total serum aluminum was bound to DFO; 44 h after DFO infusion, only 15.8 +/- 8.0% was bound. Similar results were obtained for ferrioxamine. These results suggest that the ultrafilterable serum fraction contains aluminum and iron chelated by DFO and by DFO metabolites, which retain similar metal-chelating abilities.

Ultrafiltrable aluminium after very low doses of desferrioxamine

BACKGROUND

The recommended dose of desferrioxamine for the treatment of aluminium intoxication is 5 mg/kg/week. However, there are no data about the efficiency of lower doses. The objective of this study was to investigate the capacity of very low doses of desferrioxamine in the generation of ultrafiltrable aluminium.

METHODS

Five patients undergoing haemodialysis with a similar biochemical profile and serum aluminium levels >40 microg/l were studied. The three different doses of desferrioxamine used (0.5, 2.5 and 5.0 mg/kg) were administered randomly to each patient at 1 week intervals. Total and ultrafiltrable serum aluminium was measured before and 44 h after the administration of desferrioxamine.

RESULTS

All doses of desferrioxamine significantly increased the total serum aluminium; no differences were found between 2.5 and 5.0 mg/kg. The total serum aluminium levels doubled with the 2.5 and 5.0 mg/kg doses, while the increase with 0.5 mg/kg was lower (32.6%, P<0.05). Ultrafiltrable aluminium increased with the three doses; from 7.1+/-2.8, 3.9+/-0.6 and 7.5+/-4.1 to 25.7+/-7.3, 44.3+/-10.1 and 59.1+/-19.8 microg/l, respectively (P<0.05). The efficiency of each dose was calculated using the ratio between the increase in ultrafiltrable aluminium and the dose of desferrioxamine administered. The efficiency ranged from 10.3+/-3.9 for the higher dose (5 mg/kg) to 37.2+/-10.3 for the lower dose (0.5 mg/kg).

CONCLUSIONS

Our results suggest that very low-dose desferrioxamine (>5 mg/kg) increases the ultrafiltrable (potentially dialysable) aluminium.

Aluminium removal with the double chamber technique: paired filtration-dialysis (PFD)

Several dialysis techniques have been used to improve aluminium removal. So far there are no data available using paired filtration-dialysis (PFD). In this study, we evaluated the aluminium removed by PFD in two phases. Bovine plasma with known concentrations of aluminium and desferrioxamine was used in both experiments. In phase I, the aluminium removal was investigated using the PFD system (single pass) in its usual configuration, modifying the order of the convective and diffusive processes, dialysis with high permeability membranes and dialysis with low permeability membranes. During the second phase, the experiment lasted longer using recirculation, and the PFD was compared with conventional dialysis using high permeability membranes. Changes in the PFD configuration did not alter the aluminium removal; the efficiency of PFD for aluminium removal was very close to that of dialysis with high permeability membranes and much greater than with low permeability membranes. The aluminium is removed mainly in the first part of the dialysis. Aluminium mobilization using the double chamber technique (PFD) was efficient and might be of value for those patients with aluminium overload who needs high depurative techniques and are unable to tolerate high-flux techniques.

Prevention of aluminium exposure through dialysis fluids. Analysis of changes in the last 8 years

Despite extensive measures to control aluminium exposure, chronic and acute episodes of aluminium intoxication still occur. The objective of this study was to analyse the changes in the aluminium content of dialysis fluid and the effect on serum aluminium in different dialysis centres in Spain in the last 8 years. For this purpose, the aluminium content in dialysis fluid and serum samples (N=5609) from 17 dialysis centres was analysed for >8 years (from the last quarter of 1988 to 1996). In that period of time, the percentage of dialysis fluid samples with acceptable concentrations of aluminium (<2 microg/l) increased from 0% in 1988 to 80% in 1996. The percentage of dialysis fluid samples with high aluminium levels (>6 microg/l) ranged between 37.5% in 1988 and 2.3% in 1996. The improvement in the quality of the dialysis fluid resulted in lower values of serum aluminium. The percentage of serum samples with low aluminium (<20 microg/l) increased from 16.5% in 1988 to 54.2% in 1966. The mean serum aluminium correlated with the mean dialysis fluid aluminium (r=0.55, P<0.001). A higher correlation was found when the aluminium in dialysis fluid ranged between 4 and 10 microg/l (r=0.802, P<0.001), and no correlation was found when the aluminium in dialysis fluid was <4 microg/l. Even taking into account that the dialysis fluid is not the only source of aluminium for dialysis patients, our study clearly demonstrated a close relationship with the serum aluminium content. Therefore, we must emphasize the necessity for controlling the aluminium content in dialysis fluid more often than is done at present.

Staining of bone aluminium: comparison between aluminon and solochrome azurine and their correlation with bone aluminium content

The aim of this study was to compare the sensitivity and specificity of the two histochemical stains most commonly used as indirect markers of the aluminium bone content. The clinical study was made in 28 biopsies from patients undergoing haemodialysis and the experimental study in 17 tibias from Wistar rats aluminium overloaded and with different deposits of iron. All samples were stained with aluminon, solochrome azurine and Perls and aluminium bone content was also measured. When the positive cases with Perls were excluded in the clinical study (without iron interference), the trabecular surface stained with solochrome azurine correlated with the aluminium bone content (r = 0.71, P < 0.001). With aluminon, on the other hand, no correlation was found. Solochrome azurine was always positive with aluminium contents greater than 8 micrograms/g. Aluminon was positive over 17 micrograms/g. In the experimental study, the iron concentration, in addition to other parameters, was also measured. As in the clinical study, the trabecular surface stained with solochrome azurine correlated with the aluminium content. If the positive Perls cases were excluded, the trabecular surface stained with solochrome azurine doubled the trabecular surface stained with aluminon (P < 0.001). No intratrabecular aluminon staining was observed while the intratrabecular solochrome staining correlated with the aluminium content (P < 0.001). Solochrome azurine was more sensitive than the aluminon and its lack of specificity can be easily corrected by employing Perls staining to exclude the iron interference.

Influence of iron status in the response to the deferoxamine test

The study presented here was carried out to evaluate the possible relationship between serum iron and iron transferrin saturation with the response to the deferoxamine test in 86 chronic renal failure patients undergoing hemodialysis. The deferoxamine test was performed as a diagnostic tool for aluminum intoxication. Basal serum aluminum levels correlated with: (1) serum aluminum levels after the infusion of deferoxamine (r = 0.45; P < 0.05); (2) serum iron levels (r = -0.26; P < 0.05), and; (3) iron transferrin saturation (r = -0.33; P < 0.05). The increase in serum aluminum levels after deferoxamine administration (DAI) showed a negative relationship with serum iron levels (r = -0.23; P < 0.05) and iron transferrin saturation (r = -0.26; P < 0.05). The correlations improved when analysis of this study included only those patients with high serum iron levels or high iron transferrin saturation (r = -0.55). Patients with low probability of having aluminum overload (serum iron levels < 40 micrograms/L and DAI < 150 micrograms/L) had significantly higher values of serum iron, iron transferrin saturation, and serum ferritin levels compared with those patients with a high probability of having aluminum overload (serum aluminum levels > 40 micrograms/L and DAI > 150 micrograms/L). The study presented here suggests that patients who have indicators of iron repletion would tend to have lower increases in serum aluminum levels after the challenge with deferoxamine and presumably a higher incidence of false negative results with the deferoxamine test. These findings indicate that iron measurements must be always taken into account when interpreting the deferoxamine test.

Binding of aluminium to plasma proteins: comparative effect of desferrioxamine and deferiprone (L1)

Ultramicrofiltration techniques were used to study both the binding of aluminium to high molecular weight proteins in the presence of different concentrations of desferrioxamine and deferiprone (L1) and the kinetics of aluminium release from human serum proteins. Human serum from healthy volunteers was used in all studies. The serum was spiked with aluminium (100 micrograms/l) and different concentrations of chelators. Ultramicrofiltration was performed with Amicon YMT membranes which had a nominal cut-off of 30,000 Da. Aluminium was measured by graphite furnace atomic absorption spectrometry in total serum and ultrafiltered fluid. Deferiprone shows a higher capability to displace aluminium from serum proteins (80%) than desferrioxamine (60%) at equivalent concentrations of the chelators. The kinetics of the release were also faster for deferiprone, taking 20 min to achieve its maximum effect, whereas, desferrioxamine achieved only 80% of its maximum effect after 2 h. Thus, deferiprone could be an attractive alternative to desferrioxamine, as an aluminium chelator agent.

Role of iron metabolism in absorption and cellular uptake of aluminum

The effect of iron status on aluminum (Al) absorption was investigated in this study in vivo using an animal model and in vitro using an intestinal mucosal cell line. In the in vivo model rats were rendered iron overloaded by intraperitoneal injection of iron dextran (5 mg/48 hr) or iron deficient by phlebotomy (2.5 to 3 ml blood/week). These rats, and normal controls, were then dosed with Al(OH)3 (40 mg/day) for 30 days. Urinary excretion of Al was significantly greater in the iron deficient group than in the other two groups throughout the study period, and brain Al at the end of the experiment was significantly increased in the iron depleted group (1.93 micrograms/g) and decreased in the iron overloaded group (0.73 microgram/g) compared with controls (1.42 micrograms/g). The brain Al levels in iron overloaded rats were no higher than those in normal rats that had not been dosed with Al(OH)3 (0.61 microgram/g). No significant differences were found in serum Al levels. In the in vitro experiments cultures of the rat intestinal cell line RIE1 were iron overloaded by addition of iron nitrilotriacetate (0.1 mM) or iron depleted with desferrioxamine (5 micrograms/ml) for 20 days prior to pulsing with Al transferrin (0.5 mg/ml) for 24 hours. Uptake of Al was significantly greater in the iron depleted cells (2.3 ng/micrograms cell DNA) than in iron overloaded (0.81 ng) or untreated (0.83 microgram) cells. These studies show that iron depletion markedly increases absorption and cellular uptake and suggest that susceptible individuals, such as renal failure patients, run an increased risk of toxicity if they are iron deficient.