Resistance of vascular access catheters for continuous renal replacement therapy: An ex vivo evaluation.

AIM: To assess the resistance posed by double-lumen vascular access dialysis catheters at low and high blood flow. DESIGN: Controlled ex vivo study Setting: ICU Laboratory of tertiary hospital. SUBJECTS: Eleven proprietary vascular access catheters for continuous renal replacement therapy. METHODS: Heparinized spent red cells diluted in polygeline solution were pumped using the Aquarius hemofiltration machine (Edwards Life Sciences, Sydney, NSW, Australia) and its standard circuit through several vascular access catheters. Blood flow was increased and then decreased in steps of 50 ml/min (50, 150, 200, 250 and 300 ml/min) while catheter outflow and inflow pressures were recorded. The pressure-flow relationship (hydraulic resistance) of each catheter was then calculated. Study catheters were divided into two groups according to their internal diameter (large gauge vs. smaller gauge) or length (long or short). Hydraulic resistances were compared between the groups. RESULTS: Different double lumen catheters posed clearly different resistances to flow. For all groups of catheters, there was a linear relationship between pressure and flow. No statistically significant difference between short and long catheters could be demonstrated (p=0.715). On the other hand, larger gauge catheters (13 Fr or greater) had significantly lower resistances than smaller gauge (<13 Fr) catheters (p=0.0062). Furthermore, all larger gauge catheters had resistances lower than 0.430 mmHg/ml/min, while all smaller gauge catheters had resistances greater than 0.490 mmHg/ml/min. CONCLUSIONS: Commercial double-lumen dialysis catheters have variable resistance to blood flow under standard ex vivo conditions. Although both length and internal diameter varied, internal diameter had a dominant effect on resistance. This information might be useful to clinicians in guiding their choice of catheters for clinical use.

[Scoring of disseminated intravascular coagulation (DIC) in intensive care medicine]. / Il punteggio per la diagnosi della coagulazione intravascolare disseminata (CID) in terapia intensiva.

A close association between disseminated intravascular coagulation (DIC) and increased morbidity and mortality of the critically ill has been uncovered in the ongoing validation of newly developed scoring systems of DIC. DIC scoring aims at quantifying and standardizing pathological activation of coagulation in these patients. Because of the high predictive power of DIC scoring for morbidity and mortality, early identification of DIC may play an important role in the management of critical illness by widening of the therapeutic window before development of irreversible organ failure. Therapeutic intervention in DIC is not well studied. Promising data on targeted modification of DIC by administration of antithrombin has been reported in the past, however, randomized controlled trials on the use of antithrombin for the treatment of DIC are still few. Early detection of DIC by application of novel scores could play a particular role in future DIC trials by defining patient populations most likely to benefit from targeted intervention in their clotting disturbance of critical illness.

The acid-base effect of changing citrate solution for regional anticoagulation during continuous veno-venous hemofiltration.

PURPOSE: To compare the acid-base balance effects of two different citrate doses for regional citrate anticoagulant (RCA) for continuous veno-venous hemofiltration (CVVH). METHODS: We used a commercial citrate fluid (citrate concentration: 11 mmol/L) from July 2003 to July 2004 (period A) in 22 patients; then changed to a new citrate fluid (citrate concentration: 14 mmol/L) from July 2004 to Feb 2005 (Period B) in 21 patients. Replacement fluid rate was fixed at 2,000 ml/h. We measured all relevant variables for acid-base analysis according to the Stewart-Figge methodology. RESULTS: After commencement of RCA-CVVH, there was a change in bicarbonate and base excess (BE) toward acidosis for both fluids. This change was significantly different between period A and B at 6 and 12 hours (pH: p<0.01, BE: p<0.05) with greater decreases with the 11 mmol/L citrate fluid. These changes were mostly secondary to an increase in the strong ion difference (SID) and occurred despite an increased strong ion gap (SIG) (+0.5 mEq/L vs. +1.5 mEq/L; p<0.01) in the higher citrate concentration fluid. Cessation of RCA-CVVH was associated with short-lived differences in bicarbonate and SIG which were similar to those seen on initiation of RCA-CVVH but in the opposite direction. CONCLUSIONS: A small increase This was partly offset by an increase in SIG, consistent with increased citratemia. Cessation of treatment showed a differential improvement in SIG also consistent with disposal of therapy-associated citrate. These observations might assist clinicians in interpreting acidbase changes during RCA-CVVH.in citrate infusion rate caused an alkalinizing increase in SID.

Hyperglycemia and the outcome of pediatric cardiac surgery patients requiring peritoneal dialysis.

OBJECTIVE: To study the nature of the association between glycemia and ICU mortality in pediatric cardiac surgery patients treated with peritoneal dialysis (PD). MATERIALS AND METHODS: Retrospective observational study in the ICU of a tertiary hospital involving forty pediatric cardiac surgery patients treated with PD. We selected patients requiring PD, extracted glucose measurements and nutritional intake data during ICU stay and calculated mean and maximum blood glucose values i) during ICU stay; ii) during dependence on PD; and iii) during independence from PD. We statistically assessed the relationship between glycemia-related variables and ICU mortality. MEASUREMENTS AND RESULTS: Twenty-two patients treated with PD died (mortality 55%). In the PD cohort, 9725 blood glucose measurements were performed (every 3.3 hours on average). The mean glycemia during dependence on PD was significantly higher in non-survivors than survivors (p<0.0001), but not during independence from PD (p=0.49). The area under the receiver operator characteristic curve for the mean glycemia during dependence on PD was significantly greater than that obtained during independence from PD. Even after adjustment for severity of illness using multivariate logistic analysis, the mean glycemia and calorie intake during PD were significant and independent predictors of ICU mortality. CONCLUSIONS: A higher mean blood glucose concentration during PD, but not during PD-free periods was associated with greater ICU mortality. Mean glycemia and calorie intake during PD were significant and independent predictors of ICU mortality.

A pilot randomized controlled crossover study comparing regional heparinization to regional citrate anticoagulation for continuous venovenous hemofiltration.

OBJECTIVE: To evaluate the efficacy and safety of a regional heparinization and a regional citrate method of anticoagulation in CVVH. DESIGN: Randomized controlled cross-over study. SUBJECTS: Ten critically ill patients with acute renal failure. SETTING: ICU of tertiary hospital. INTERVENTION: CVVH was performed with pre-filter fluid replacement at 2000 ml/h and a blood flow rate of 150 ml/min. Regional heparinization was by the administration of heparin pre-filter at 1500 IU/h and protamine post-filter at 15 mg/h. Regional citrate anticoagulation was by means of a citrate-based replacement fluid (14 mmol/L) administered pre-dilution. RESULTS: We studied nine males and one female. The mean age and APACHE II score were 70.5 and 17 respectively. Median circuit life was 13 hours (IQR 9.28) for the regional heparinization method compared to 17 hours (IQR 12,19.5) for the regional citrate method (p=0.77). There were no episodes of bleeding in either group. CONCLUSION: Regional heparinization and regional citrate anticoagulation achieve similar circuit life in critically ill patients receiving CVVH.

Renal blood flow in experimental septic acute renal failure.

Reduced renal blood flow (RBF) is considered central to the pathogenesis of septic acute renal failure (ARF). However, no controlled experimental studies have continuously assessed RBF during the development of severe septic ARF. We conducted a sequential animal study in seven female Merino sheep. Flow probes were implanted around the pulmonary and left renal arteries. Two weeks later, systemic hemodynamics and RBF were monitored continuously during a 48-h control period and, after a week, during a 48-h period of hyperdynamic sepsis induced by continuous Escherichia coli infusion. Infusion of E. coli induced hyperdynamic sepsis with significantly increased cardiac output (3.8+/-0.4 vs 9.8+/-1.1 l/min; P<0.05), decreased mean arterial pressure (89.2+/-3.2 vs 64.3+/-5.3 mm Hg; P<0.05), and increased total peripheral conductance (42.8+/-3.5 in controls vs 153.7+/-24.7 ml/min/mm Hg in septic animals; P<0.05). Hyperdynamic sepsis was associated with marked renal vasodilatation (renal conductance: 3.0+/-0.7 vs 11.4+/-3.4 ml/min/mm Hg; P<0.05) and a marked increase in RBF (262.3+/-47.7 vs 757.4+/-250.1 ml/min; P<0.05). Serum creatinine increased over 48 h (73+/-18 vs 305+/- micromol/l; P<0.05) whereas creatinine clearance decreased (95.5+/-25.9 vs 20.1+/-19.3 ml/min; P<0.05). After 24 h, urine output decreased from 1.4 to 0.3 ml/kg/h (P<0.05). Infusion of E. coli induced hyperdynamic sepsis and ARF. Septic ARF in this setting was associated with a marked increase in RBF and with renal vasodilatation.

Commercial low-citrate anticoagulation haemofiltration in high risk patients with frequent filter clotting.

This study assessed the safety and efficacy of a commercial low-citrate concentration-based pre-filter replacement fluid during continuous veno-venous haemofiltration (CVVH) in patients with frequent filter clotting and high risk of bleeding. We used a commercial low-citrate fluid as pre-dilution replacement fluid during CVVH (citrate: 11 mmol/l (33 meq/l), sodium: 140 mmol/l, chloride: 108 mmol/l and potassium: 1 mmol/l). A calcium and magnesium infusion was delivered separately by central line for the maintenance of serum ionized calcium (Cai) and total magnesium (Mg). In this prospective observational study, 30 patients, 124 filters and 1,515 treatment-hours were observed. Median filter life of citrate CVVH was 9.5 hours. Filter life in the 48 hours prior to citrate CVVH was also observed. In the patients on prior non-anticoagulant CVVH (n=14) filter life increased significantly with citrate (9.5 hours vs 5 hours; P<0.0001). In patients on prior heparin CVVH (n = 15), filter life was similar with citrate (10 hours vs 8 hours; P = 0.68). However, in patients with prior early/frequent filter clotting despite heparin (n = 11) filter life increased significantly (10 hours vs 7 hours; P=0.038). Of 411 serum Cai measurements, none showed a Cai < 0.85 mmol/l and, of 84 observations, none showed a serum Mg<0. 6 mmol/l. One patient with sepsis and shock needed to cease citrate CVVH because of progressive ionized hypocalcaemia and increasing anion gap. No other adverse effects were observed. In selected patients, CVVH with a commercial low-citrate concentration solution as pre-filter replacement fluid and a simultaneous calcium and magnesium infusion protocol appears generally safe. Filter life was acceptable and superior to that achieved with previous treatment.

Low-dose citrate continuous veno-venous hemofiltration (CVVH) and acid-base balance.

OBJECTIVE: To evaluate the acid-base effect of low-dose regional citrate anticoagulation (RCA) during continuous veno-venous hemofiltration (CVVH). DESIGN: Prospective observational study. SETTING: ICUs of tertiary public and private hospitals. SUBJECTS: Thirty critically ill patients with acute renal failure at risk of bleeding or with a major contraindication to heparin-CVVH and/or short filter life. METHODS: We used a commercial citrate-based fluid (11 mmol/L, sodium: 140 mmol/L, chloride: 108 mmol/L and 1 mol/L of potassium) as pre-dilution replacement fluid during CVVH. Further potassium was added according to serum potassium levels. We measured all relevant variables for acid-base analysis according to the Stewart-Figge methodology. RESULTS: Before treatment, study patients had a slight metabolic acidosis, which worsened over 6 hours of RCA-CVVH (pH from 7.39 to 7.38, p < 0.005; bicarbonate from 23.2 to 21.6 mmol/L, p < 0.0001 and base excess from -2.0 to -3.0 mEq/L, p < 0.0001) due to a significant increase in SIG (from 5.8 to 6.6 mEq/L, p < 0.05) and a decrease in SIDa (from 37.5 to 36.6 mEq/L, p < 0.05). These acidifying effects were attenuated by hypoalbuminemia and a decrease in lactate (from 1.48 to 1.34 mmol/L, p < 0.005) and did not lead to progressive acidosis. On cessation of treatment, this acidifying effect rapidly self-corrected within six hours. CONCLUSIONS: Low dose RCA-CVVH induces a mild acidosis secondary to an increased strong ion gap and decreased SIDa which fully self-corrects at cessation of therapy. Clinicians need to be aware of these effects to correctly interpret changes in acid-base status in such patients.

A comparison of two citrate anticoagulation regimens for continuous veno-venous hemofiltration.

AIMS: To assess the safety and efficacy of two different commercial citrate containing pre-filter replacement fluids during continuous veno-venous hemofiltration (CVVH) in patients with frequent filter clotting. SETTING: Four intensive care units. PATIENTS: Sixty-three critically ill patients with acute renal failure (ARF). DESIGN: Prospective observational study. METHODS: We used a commercial citrate fluid (citrate: 11 mmol/L -fluid A) as predilution replacement for CVVH. We then changed to a new commercial citrate fluid (citrate: 14 mmol/L-fluid B) as replacement fluid and performed statistical comparisons. Replacement fluid rate was fixed at 2,000 ml/hour. RESULTS: Filter life was 12.2 hour with fluid A compared with 17.1 hour with fluid B on average (p=0.0001). Mean post filter ionized calcium concentration was 0.52 mmol/L with fluid A compared with 0.40 mmol/L with fluid B (p<0.0001). Citrate intolerance led to cessation of treatment in one patient with fluid A and one patient with fluid B. Overall ionized calcium levels were higher (A: 1.18 vs B: 1.13 mmol/L; p<0.0001) and bicarbonate was lower (A: 22.4 vs B: 24.5 mmol/L; p<0.0001) during treatment with fluid A. Alkalemia was seen in 10 patients treated with fluid A and 16 patients treated with fluid B (NS). CONCLUSIONS: We have developed a simple approach to regional citrate anticoagulation for CVVH using a commercial citrate-containing fluid as replacement fluid. Increasing citrate concentration from 11 to 14 mmol/L increased filter life while maintaining relative safety and simplicity.

A pilot study of the effect of altering airway pressure on systolic pulse pressure variation in the systemic and pulmonary arterial circulations.

OBJECTIVE: Systolic pressure variation results from cyclical fluctuation in the intra-thoracic pressure associated with mechanical ventilation and has been used as a measure of relative hypovolemia in mechanically ventilated patients. The impact of the magnitude of the tidal volume and airway pressure on systolic pressure variation, however, has not been examined in mechanically ventilated patients. METHODS: Two patients underwent monitoring following elective cardiac surgery. Tidal volume was randomly varied between 3 and 11 mL/kg over a two minute interval, and the corresponding airway pressure was monitored, as were the effects on the systolic pressure variation of the systemic and pulmonary circulations. RESULTS: There was a strong correlation between increasing tidal volume and peak airway pressure (p<0.0001). In addition, peak airway pressure strongly correlated with the systolic pressure variation of both the systemic and pulmonary circulations (p<0.0001). The increase in diastolic pulmonary arterial pressure induced by insufflation correlated well with the associated increase in systolic blood pressure (p<0.0001). Similarly, the increase in systolic pulmonary artery pressure (PAP) correlated with the associated decrease in systolic blood pressure induced by insufflation (p<0.0001). CONCLUSIONS: Systolic pressure variation in the systemic and pulmonary circulations is affected by tidal volume and peak airway pressure. This should be considered when using systolic pressure variation as a marker of intravascular volume status. Our findings regarding the correlations between changes in the pulmonary arterial pressure and the systemic arterial pressure induced by mechanical ventilation are consistent with the proposed physiological mechanisms of systolic pressure variation.

[Epidemiological analysis on many cases of tsutsugamushi disease found in Hiroshima Prefecture, Japan].

The clinical findings of tsutsugamushi disease and the fauna of trombiculid mites in Hiroshima Prefecture were studied in this report. We reviewed 63 cases of tsutsugamushi disease occurring between 1990 and 1999, and most of cases were contracted in the area around the midportion of the Oota River (55 cases; 87.3%). Of these, 30 cases (47.1%) lived in Asakita-ku in Hiroshima City. Eschar was detected in 33/19 (84.6%) cases, and 97.6% (40/41), 88.9% (16/18) patients showed eruption and lymphadenopathy respectively. Biochemical examination revealed liver dysfunction in 38.1% (8/21) patients. Of the 11 cases examined on peripheral blood smear, atypical lymphocytes were detected in 10 cases (90.9%). Fifty-five cases (90.2%) occurred during the restricted season between September and December each year. The predominance of Leptotrombidium scutellare was verified by collection of trombiculid mites along the basin of the Oota River. Serum antibody titration on a patient in Asakita-ku showed reaction to Kawasaki type antigen definitive to L. scutellare. Therefore, we speculate that L. scutellare is a candidate for the vector of Orientia tsutsugamushi in Hiroshima Prefecture.