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Introduction: Metabolic acidosis during hemorrhagic shock is common and conventionally considered to be due to hyperlactatemia. There is increasing awareness, however, that other nonlactate, unmeasured anions contribute to this type of acidosis.
Methods: Eleven anesthetized dogs were hemorrhaged to a mean arterial pressure of 45 mm Hg and were kept at this level until a metabolic oxygen debt of 120 mLO2/kg body weight had evolved. Blood pH, partial pressure of carbon dioxide, and concentrations of sodium, potassium, magnesium, calcium, chloride, lactate, albumin, and phosphate were measured at baseline, in shock, and during 3 hours post-therapy. Strong ion difference and the amount of weak plasma acid were calculated. To detect the presence of unmeasured anions, anion gap and strong ion gap were determined. Capillary electrophoresis was used to identify potential contributors to unmeasured anions.
Results: During induction of shock, pH decreased significantly from 7.41 to 7.19. The transient increase in lactate concentration from 1.5 to 5.5 mEq/L during shock was not sufficient to explain the transient increases in anion gap (+11.0 mEq/L) and strong ion gap (+7.1 mEq/L), suggesting that substantial amounts of unmeasured anions must have been generated. Capillary electrophoresis revealed increases in serum concentration of acetate (2.2 mEq/L), citrate (2.2 mEq/L), alpha-ketoglutarate (35.3 microEq/L), fumarate (6.2 microEq/L), sulfate (0.1 mEq/L), and urate (55.9 microEq/L) after shock induction.
Conclusion: Large amounts of unmeasured anions were generated after hemorrhage in this highly standardized model of hemorrhagic shock. Capillary electrophoresis suggested that the hitherto unmeasured anions citrate and acetate, but not sulfate, contributed significantly to the changes in strong ion gap associated with induction of shock.
Background and Objectives: Delirium is a common and major complication subsequent to cardiac surgery. Despite scientific efforts, there are no parameters which reliably predict postoperative delirium. In delirium pathology, natriuretic peptides (NPs) interfere with the blood–brain barrier and thus promote delirium. Therefore, we aimed to assess whether NPs may predict postoperative delirium and long-term outcomes. Materials and Methods: To evaluate the predictive value of NPs for delirium we retrospectively analyzed data from a prospective, randomized study for serum levels of atrial natriuretic peptide (ANP) and the precursor of C-type natriuretic peptide (NT-proCNP) in patients undergoing coronary artery bypass grafting (CABG) with or without cardiopulmonary bypass (off-pump coronary bypass grafting; OPCAB). Delirium was assessed by a validated chart-based method. Long-term outcomes were assessed 10 years after surgery by a telephone interview. Results: The overall incidence of delirium in the total cohort was 48% regardless of the surgical approach (CABG vs. OPCAB). Serum ANP levels >64.6 pg/mL predicted delirium with a sensitivity (95% confidence interval) of 100% (75.3–100) and specificity of 42.9% (17.7–71.1). Serum NT-proCNP levels >1.7 pg/mL predicted delirium with a sensitivity (95% confidence interval) of 92.3% (64.0–99.8) and specificity of 42.9% (17.7–71.1). Both NPs could not predict postoperative survival or long-term cognitive decline. Conclusions: We found a positive correlation between delirium and preoperative plasma levels of ANP and NT-proCNP. A well-powered and prospective study might identify NPs as biomarkers indicating the risk of delirium and postoperative cognitive decline in patients at risk for postoperative delirium.