0.9% saline is neither normal nor physiological

Abstract

Abstract:The purpose of this review is to objectively evaluate the biochemical and pathophysiological properties of 0.9% saline (henceforth: saline) and to discuss the impact of saline infusion, specifically on systemic acid-base balance and renal hemodynamics. Studies have shown that electrolyte balance, including effects of saline infusion on serum electrolytes, is often poorly understood among practicing physicians and inappropriate saline prescribing can cause increased morbidity and mortality. Large-volume (>2 L) saline infusion in healthy adults induces hyperchloremia which is associated with metabolic acidosis, hyperkalemia, and negative protein balance. Saline overload (80 ml/kg) in rodents can cause intestinal edema and contractile dysfunction associated with activation of sodium-proton exchanger (NHE) and decrease in myosin light chain phosphorylation. Saline infusion can also adversely affect renal hemodynamics. Microperfusion experiments and real-time imaging studies have demonstrated a reduction in renal perfusion and an expansion in kidney volume, compromising O 2 delivery to the renal parenchyma following saline infusion. Clinically, saline infusion for patients post abdominal and cardiovascular surgery is associated with a greater number of adverse effects including more frequent blood product transfusion and bicarbonate therapy, reduced gastric blood flow, delayed recovery of gut function, impaired cardiac contractility in response to inotropes, prolonged hospital stay, and possibly increased mortality. In critically ill patients, saline infusion, compared to balanced fluid infusions, increases the occurrence of acute kidney injury. In summary, saline is a highly acidic fluid. With the exception of saline infusion for patients with hypochloremic metabolic alkalosis and volume depletion due to vomiting or upper gastrointestinal suction, indiscriminate use, especially for acutely ill patients, may cause unnecessary complications and should be avoided. More education regarding saline-related effects and adequate electrolyte management is needed.

The use of crystalloids in traumatic brain injury

“…There is no reason why both may not be used if plasma chloride concentrations are being monitored. The case for balanced salt solutions includes the occurrence of dilution hyperchloremic acidosis following massive saline infusion [32,33]. Indeed, infusion of large volumes of normal saline commonly leads to dilution hyperchloremic acidosis, particularly in hypovolaemic patients with impaired kidney function or perfusion [33].…”

“…The case for balanced salt solutions includes the occurrence of dilution hyperchloremic acidosis following massive saline infusion [32,33]. Indeed, infusion of large volumes of normal saline commonly leads to dilution hyperchloremic acidosis, particularly in hypovolaemic patients with impaired kidney function or perfusion [33]. Evidence has been produced that massive infusion of chloride-rich fluids leads to renal ischemia following interstitial oedema, and reduces glomerular filtration following arterial vasoconstriction, hence increasing the risk of AKI [34,35].…”

Intravenous Fluids and Acute Kidney Injury

“…In balanced crystalloid fluids, metabolizable anions are incorporated to substitute bicarbonate and the final components of a balanced crystalloid resemble the constituents of normal plasma [50]. High chloride-containing saline, that is, 0.9% saline contains super physiological content of chloride which, when infused in large quantities (>2 liters), can cause hyperchloremic acidosis, which may engender complications including coagulopathy, hyperkalemia and more pronounced interstitial fluid retention; 0.9% saline infusion also causes greater fluid retention (∼60% by 6 h post infusion) than that of 5% dextrose in normal adults [51].…”

“…Chowdhury et al [52] clearly show that 0.9% saline infusion (2 liters), when compared to the same amount of balanced fluid infusion, causes more significant reduction in the renal cortical blood flow and oxygen delivery. Such differences likely are related, at least in part, to the super physiological chloride content in 0.9% saline, which activates the tubuloglomerular feedback among other renal tubular effects [67], causing afferent arteriole vasoconstriction [50]. Simultaneous venous congestion and afferent arteriole constriction further diminish forward blood flow [68].…”

Associação de hipernatremia com o prognóstico e a mortalidade de pacientes com traumatismo cranioencefálico grave em um hospital terciário brasileiro

“…(157,159,160) Além desta complicação, já é bem estabelecido que o uso excessivo de SF está associado à acidose metabólica hiperclorêmica em pacientes críticos, além do risco relativos à hipervolemia, como edema pulmonar e de alças intestinais, o que exige um uso cauteloso desta solução. (160)(161)(162) Como já mencionado anteriormente, a hipernatremia vem sendo reconhecida como fator de risco independente para óbito em vários estudos realizados em pacientes críticos, neurocríticos e com TCE. (71,125,126,128,132,135,136,138,140,142,163,164) Em alguns destes estudos, também foram avaliados separadamente os grupos que desenvolveram hipernatremia leve ou grave (ou ainda, leve, moderada e grave).…”