Alexandre Toledo Maciel

Evolutive standard base excess and serum lactate level in severe sepsis and septic shock patients resuscitated with early goal-directed therapy: still outcome markers?

PURPOSE To compare the evolution of standard base excess and serum lactate level between surviving and non surviving patients with severe sepsis and septic shock resuscitated with early goal-directed therapy. METHODS This is a retrospective study in an intensive care unit of a university tertiary hospital where 65 consecutive severe sepsis and septic shock patients were observed without any intervention in the treatment by the authors of this report. RESULTS In our study, the mortality of severe sepsis and septic shock patients was 38%. The central venous oxygen saturation of both groups was above 70% after the resuscitative period, excluding the second day of the non survivors group (69.8%). After the second day, the central venous oxygen saturation was significantly higher in the survivors group (P < .001). Standard base excess was initially low in both groups, but from the second day on, the correction of standard base excess was significantly more successful and linear in the survivor group (P < .001). Lactate levels were similar during the evolution of both groups. CONCLUSIONS Although evolutive standard base excess and serum lactate level are still outcome markers in severe sepsis and septic shock patients resuscitated with early goal-directed therapy, other studies must be performed to clarify if hemodynamic interventions based on standard base excess and serum lactate level could be reliable to improve clinical outcomes in severe sepsis and septic shock patients.

The use of sodium-chloride difference and chloride-sodium ratio as strong ion difference surrogates in the evaluation of metabolic acidosis in critically ill patients

PURPOSE Inorganic apparent strong ion difference (SIDai) improves chloride-associated acidosis recognition in dysnatremic patients. We investigated whether the difference between sodium and chloride (Na(+)-Cl(-)) or the ratio between chloride and sodium (Cl(-)/Na(+)) could be used as SIDai surrogates in mixed and dysnatremic patients. PATIENTS AND METHODS Two arterial blood samples were collected from 128 patients. Physicochemical analytical approach was used. Correlation, agreement, accuracy, sensitivity, and specificity were measured to examine whether Na(+)-Cl(-) and Cl(-)/Na(+) could be used instead of SIDai in the diagnosis of acidosis. RESULTS Na(+)-Cl(-) and Cl(-)/Na(+) were well correlated with SIDai (R = 0.987, P < 0.001 and R = 0.959, P < 0.001, respectively). Bias between Na(+)-Cl(-) and SIDai was high (6.384 with a limit of agreement of 4.463-8.305 mEq/L). Accuracy values for the identification of SIDai acidosis (<38.9 mEq/L) were 0.989 (95% confidence interval [CI], 0.980-0.998) for Na(+)-Cl(-) and 0.974 (95% CI, 0.959-0.989) for Cl(-)/Na(+). Receiver operator characteristic curve showed that values revealing SIDai acidosis were less than 32.5 mEq/L for Na(+)-Cl(-) and more than 0.764 for Cl(-)/Na(+) with sensitivities of 94.0% and 92.0% and specificities of 97.0% and 90.0%, respectively. Na(+)-Cl(-) was a reliable SIDai surrogate in dysnatremic patients. CONCLUSIONS Na(+)-Cl(-) and Cl(-)/Na(+) are good tools to disclose SIDai acidosis. In patients with dysnatremia, Na(+)-Cl(-) is an accurate tool to diagnose SIDai acidosis.

Differences in acid-base behavior between intensive care unit survivors and nonsurvivors using both a physicochemical and a standard base excess approach: a prospective, observational study.

PURPOSE This study aimed to test the hypothesis that intensive care unit survivors and nonsurvivors differ with regard to type and severity of acid-base disorders. MATERIALS AND METHODS Prospective, observational, cohort study of 107 consecutive patients admitted in a 7-bed intensive care unit during a 6-month period that stayed at least 4 days. All acid-base variables for the first 3 days and the day of discharge were analyzed. RESULTS Survivors had significant metabolic acidosis upon admission, which was due to hyperlactatemia, an excess of unmeasured anions, and principally, hyperchloremia. A progressive decrease in these anions in the presence of constant hypoalbuminemia led to normal standard base excess at discharge. Nonsurvivors had greater metabolic acidosis upon admission with acidifying variables in similar proportions to that of the survivors. On the day of death, nonsurvivors had a similar degree of metabolic acidosis but a different proportion of the anions (less chloride and more lactate) compared with the day of admission. Unmeasured anions were greater in nonsurvivors both on the day of admission and on the day of death. CONCLUSIONS Intensive care unit survivors and nonsurvivors differed in the severity of metabolic acidosis; however, the proportion of the different anions causing the acidosis on admission was similar between these 2 groups.

Characterization of an animal model of severe sepsis associated with respiratory dysfunction

PURPOSE Pathophysiological studies in humans regarding sepsis are difficult to perform due to ethical and methodological concerns. In this context, animal models of sepsis can be useful to better understand this condition and to test therapeutic strategies. The purpose of this study was to characterize a feasible and clinically relevant model of sepsis in pigs that could be useful for testing different therapeutic interventions. METHODS 5 White Large pigs were anesthetized, arterial and pulmonary catheters were introduced, and sepsis was induced by fecal peritonitis. Several biochemical indicators of organ dysfunction and infectious parameters were measured. The pigs were monitored until death, when fragments of organs were removed for pathology. Three animals without peritonitis served as controls and were sacrificed 24 hours after surgery without developing significant changes in organ function. RESULTS Septic pigs survived 17 hours on average (range, 16-18 h), and Escherichia coli was recovered from blood cultures. They developed a significant decrease in left ventricular work and a nonsignificant reduction in mixed venous oxygen saturation. Respiratory dysfunction was characterized by a decrease in the PaO2/FiO2 ratio and respiratory compliance. Pathology of the lungs revealed areas of pulmonary collapse, hemorrhage, pulmonary congestion, and discrete neutrophil infiltrate. CONCLUSIONS Fecal peritonitis in pigs is a clinically relevant model of sepsis associated with acute lung injury without direct pulmonary insult. This model may prove to be useful for studying pathogenic aspects of secondary lung injury as well as for validating ventilatory or pharmacologic interventions.

First-year experience of a Brazilian tertiary medical center in supporting severely ill patients using extracorporeal membrane oxygenation

OBJECTIVES: The aim of this manuscript is to describe the first year of our experience using extracorporeal membrane oxygenation support. METHODS: Ten patients with severe refractory hypoxemia, two with associated severe cardiovascular failure, were supported using venous-venous extracorporeal membrane oxygenation (eight patients) or veno-arterial extracorporeal membrane oxygenation (two patients). RESULTS: The median age of the patients was 31 yr (range 14–71 yr). Their median simplified acute physiological score three (SAPS3) was 94 (range 84–118), and they had a median expected mortality of 95% (range 87–99%). Community-acquired pneumonia was the most common diagnosis (50%), followed by P. jiroveci pneumonia in two patients with AIDS (20%). Six patients were transferred from other ICUs during extracorporeal membrane oxygenation support, three of whom were transferred between ICUs within the hospital (30%), two by ambulance (20%) and one by helicopter (10%). Only one patient (10%) was anticoagulated with heparin throughout extracorporeal membrane oxygenation support. Eighty percent of patients required continuous venous-venous hemofiltration. Three patients (30%) developed persistent hypoxemia, which was corrected using higher positive end-expiratory pressure, higher inspired oxygen fractions, recruitment maneuvers, and nitric oxide. The median time on extracorporeal membrane oxygenation support was five (range 3–32) days. The median length of the hospital stay was 31 (range 3-97) days. Four patients (40%) survived to 60 days, and they were free from renal replacement therapy and oxygen support. CONCLUSIONS: The use of extracorporeal membrane oxygenation support in severely ill patients is possible in the presence of a structured team. Efforts must be made to recognize the necessity of extracorporeal respiratory support at an early stage and to prompt activation of the extracorporeal membrane oxygenation team.

Unmeasured anions account for most of the metabolic acidosis in patients with hyperlactatemia

PURPOSE To characterize the different components of metabolic acidosis in patients with hyperlactatemia in order to determine the degree to which lactate is responsible for the acidosis and the relevance that this might have in the outcome of these patients. METHODS Arterial blood gas, arterial lactate, Na+, K+, Ca2+, Mg2+, Cl-, phosphate, albumin, and creatinine were measured on admission to make a diagnosis of the acid-base disturbances present. Intensive Care Unit and in-hospital mortality were also recorded. RESULTS A total of 58 patients with hyperlactatemia were included. They usually had a mild acidemia (pH 7.31 +/- 0.12) and a significantly high Standard Base Deficit (7.6 +/- 6.7 mEq/L). In addition to lactate (4.3 +/- 2.3 mEq/L), chloride (106.9 +/- 9.5 mEq/L) and unmeasured anions (8.6 +/- 5.0 mEq/L) accounted for the metabolic acidosis. Unmeasured anions were primarily responsible for the acidosis in both Intensive Care Unit survivors and nonsurvivors (44.7% +/- 26.0% and 46.0% +/- 17.5%, respectively, P = 0.871). Lactate contributed in similar percentages to the acidosis in both groups (23.0% +/- 11.8% and 24.2% +/- 9.7% in Intensive Care Unit survivors and nonsurvivors, respectively; P = 0.753). Correlation between Standard Base Deficit and lactate was found only in Intensive Care Unit nonsurvivors (r = 0.662, P < 0.01). DISCUSSION Hyperlactatemia is usually accompanied by metabolic acidemia, but lactate is responsible for a minor percentage of the acidosis; unmeasured anions account for most of the acidosis in patients with hyperlactatemia. The percentage of the acidosis due to hyperlactatemia was not relevant in terms of outcome.

Determinants of Oxygen and Carbon Dioxide Transfer during Extracorporeal Membrane Oxygenation in an Experimental Model of Multiple Organ Dysfunction Syndrome

Extracorporeal membrane oxygenation (ECMO) has gained renewed interest in the treatment of respiratory failure since the advent of the modern polymethylpentene membranes. Limited information exists, however, on the performance of these membranes in terms of gas transfers during multiple organ failure (MOF). We investigated determinants of oxygen and carbon dioxide transfer as well as biochemical alterations after the circulation of blood through the circuit in a pig model under ECMO support before and after induction of MOF. A predefined sequence of blood and sweep flows was tested before and after the induction of MOF with fecal peritonitis and saline lavage lung injury. In the multivariate analysis, oxygen transfer had a positive association with blood flow (slope = 66, P<0.001) and a negative association with pre-membrane PaCO2 (slope = −0.96, P = 0.001) and SatO2 (slope = −1.7, P<0.001). Carbon dioxide transfer had a positive association with blood flow (slope = 17, P<0.001), gas flow (slope = 33, P<0.001), pre-membrane PaCO2 (slope = 1.2, P<0.001) and a negative association with the hemoglobin (slope = −3.478, P = 0.042). We found an increase in pH in the baseline from 7.50[7.46,7.54] to 7.60[7.55,7.65] (P<0.001), and during the MOF from 7.19[6.92,7.32] to 7.41[7.13,7.5] (P<0.001). Likewise, the PCO2 fell in the baseline from 35 [32,39] to 25 [22,27] mmHg (P<0.001), and during the MOF from 59 [47,91] to 34 [28,45] mmHg (P<0.001). In conclusion, both oxygen and carbon dioxide transfers were significantly determined by blood flow. Oxygen transfer was modulated by the pre-membrane SatO2 and CO2, while carbon dioxide transfer was affected by the gas flow, pre-membrane CO2 and hemoglobin.

Physicochemical analysis of blood and urine in the course of acute kidney injury in critically ill patients: a prospective, observational study.

BackgroundSequential physicochemical alterations in blood and urine in the course of acute kidney injury (AKI) development have not been previously described. We aimed to describe these alterations in parallel to traditional renal and acid–base parameters.MethodsOne hundred and sixty eight consecutive critically ill patients with no previous kidney disease, who had an indwelling urinary catheter at ICU admission and who remained with the catheter for at least two days without dialysis were included. A sample of blood and spot urine were collected simultaneously, once daily, until catheter removal or dialysis requirement. Traditional acid–base and renal parameters were sequentially evaluated in parallel to blood and urinary physicochemical parameters. Patients were classified during this period as having or not AKI and, for patients with AKI, duration (transient or persistent) and severity (creatinine-based AKIN stage) were evaluated.ResultsOne hundred and thirteen patients (67.3%) had AKI: 92 at ICU admission and 21 during the observation period. AKI development was characterized in blood by increased values of phosphate and unmeasured anions (SIG), decreased albumin, and in urine by decreased values of sodium (NaU), chloride (ClU) as well as high urinary strong ion difference (SIDu). These alterations began to occur before AKI diagnosis, and they reverted in transient AKI but remained in persistent AKI. NaU, ClU and albumin decreased, and phosphate, SIG and SIDu increased with AKI severity progression. NaU and ClU values increased again when AKIN stage 3 was reached.ConclusionsSimultaneous physicochemical analysis of blood and urine revealed standardized alterations that characterize AKI development in critically ill patients. These alterations paralleled AKI duration and severity. Future studies should consider including sequential evaluation of urine biochemistry as part of the armamentarium for AKI diagnosis and management.

Monitorização de eletrólitos urinários em pacientes críticos: estudo preliminar observacional.

OBJECTIVE Intensive care unit survivors and non-survivors have distinct acid-base profiles. The kidneys regulation of urinary electrolytes and the urinary strong ion difference plays a major role in acid-base homeostasis. The aim of this study was to evaluate the potential utility of daily spot urinary electrolyte measurement in acid-base and renal function monitoring. METHODS We prospectively recorded daily plasma acid-base parameters and traditional markers of renal function in parallel with spot urinary electrolyte measurements in patients with urinary catheters admitted to our intensive care unit. Patients who remained in the intensive care unit for at least 4 days with a urinary catheter were included in the study. RESULTS Of the 50 patients included in the study, 22% died during their intensive care unit stay. The incidence of acute kidney injury was significantly higher in non-survivors during the 4-day observation period (64% vs. 18% in survivors). Urinary chloride and sodium were lower and urinary strong ion difference was higher on day 1 in patients who developed acute kidney injury among both survivors and non-survivors. Both groups had similar urine output, although non-survivors had persistently higher urinary strong ion difference on all days. Survivors had a progressive improvement in metabolic acid-base profile due to increases in the plasma strong ion difference and decreases in weak acids. These changes were concomitant with decreases in urinary strong ion difference. In non-survivors, acid-base parameters did not significantly change during follow-up. CONCLUSIONS Daily assessment of spot urinary electrolytes and strong ion difference are useful components of acid-base and renal function evaluations in critically ill patients, having distinct profiles between intensive care unit survivors and non-survivors.

Effect of Paco2 variation on standard base excess value in critically ill patients

PURPOSE The aim of this study was to investigate the impact of acute Paco(2) temporal variation on the standard base excess (SBE) value in critically ill patients. METHODS A total of 265 patients were prospectively observed; 158 were allocated to the modeling group, and 107 were allocated to the validation group. Two models were developed in the modeling group (one including and one excluding Paco(2) as a variable determinant of SBE), and both were tested in the validation group. RESULTS In the modeling group, the mathematical model including SIDai, SIG, l-lactate, albumin, phosphate, and Paco(2) had a predictive superiority in comparison with the model without Paco(2) (R(2) = 0.978 and 0.916, respectively). In the validation group, the results were confirmed with significant F change statistics (R(2) change = 0.059, P < .001) between the model with and without Paco(2). A high correlation (R = 0.99, P < .001) and agreement (bias = -0.25 mEq/L, limits of agreement 95% = -0.72 to 0.22 mEq/L) were found between the model-predicted SBE value and the SBE calculated using the Van Slyke equation. CONCLUSIONS Acute Paco(2) temporal variation is related to SBE changes in critically ill patients.