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|NI FEATURE: THE EDITORIAL DEBATE III-- PROS AND CONS
|Year : 2018 | Volume
| Issue : 5 | Page : 1301-1302
Is buffered crystalloid safer than normal saline in neurosurgery?
Shalini Nair, Mathew Joseph
Neuro-Intensive Care Unit, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Web Publication||17-Sep-2018|
Dr. Mathew Joseph
Neuro.-Intensive Care Unit, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Nair S, Joseph M. Is buffered crystalloid safer than normal saline in neurosurgery?. Neurol India 2018;66:1301-2
Normal saline has been the commonest intravenous fluid used both for resuscitation and as a maintenance fluid in emergency departments, operating rooms and intensive care units. However, normal saline is not normal when compared to plasma, neither in its osmolality nor the electrolyte content. The two major problems identified with the use of large volumes of normal saline are metabolic complications (primarily, hyperchloremic acidosis) and acute kidney injury, possibly as a consequence of the acidosis acting on renal vasculature and blood flow. In the brain, saline induced hyperchloremic acidosis has been suggested as a cause of brain stem ischemia akin to its effect on renal blood flow., These potential problems have been known for a long time, and the use of balanced solutions as a replacement for normal saline has been studied with varying conclusions regarding the prevention of complications. The traditionally used balanced solution is Ringer's lactate, but this is a poor choice in patients with raised intracranial pressure because it is hypo-osmolar (273 mOsm/L) when compared to plasma, and could, therefore, contribute to brain edema. Plasma-lyte A is the latest solution that has been made commercially available to overcome the problems with the more time-honoured solutions.
Plasma-lyte A is an acetate and gluconate buffered solution with an osmolality of 294 mOsm/L. It has a strong ion difference of 29 mOsm/L and is overall more physiological in constitution than normal saline. Semler et al., proved that use of balanced solutions could prevent the need for new renal-replacement therapy, persistent renal dysfunction or death in one of every 94 critically ill patients in the intensive care unit (ICU). The use of Plasma-lyte A has increased tremendously in neurosurgery, and it is a little surprising that its effect on the brain has not been studied in greater detail. The authors need to be commended for their contribution to neurosurgical literature.
The use of neutrophil gelatinase associated lipocalin (NGAL) instead of serum creatinine helps to detect acute renal injury (AKI) earlier, as the authors have described. Urine NGAL is often considered to be superior and more reliable in diagnosing AKI, but a meta-analysis by Haase et al., found the urine and serum levels NGAL to perform equally well in diagnosing AKI. The cutoff of >150 ng/ml, as used by the authors, improved the performance of NGAL in standardized clinical labs. The use of serum creatinine for measuring the renal function pre-operatively and NGAL for measuring the renal status in the postoperative period is less than ideal. Serum creatinine is well known to imperfectly estimate renal dysfunction, and in patients with a reduced muscle mass, creatinine estimate alone may delay the diagnosis of renal failure. It is possible to argue that serum NGAL might have been raised in patients preoperatively, as is known to occur in chronic renal dysfunction.,
The methodology of the study published in this issue of Neurology India seems quite robust and the two arms are relatively well matched to compare the results between them. It is unfortunate that the normal saline group had a higher blood loss as the incidence of metabolic complications could be attributed to this factor rather than the choice of fluids. However, this argument can largely be refuted by the lack of significant difference in the administered blood and fluids. It is also possible that the metabolic acidosis itself contributed in some part to the bleeding. In a trauma cohort, Smith et al., found acidosis to affect rates of factor amplification and fibrin cross-linking, contributing to coagulopathy. Hyperchloremia caused a longer k and a decreased α angle on thromboelastography.
The hyperchloremia secondary to saline infusion produced the expected difference in pH and chloride levels. The authors did not find any significant changes in sodium or osmolality in the two groups, possibly because the volumes of fluid infused were not particularly large. Young et al., investigating the effect of saline versus a buffered crystalloid solution on acute kidney injury among patients in the intensive care unit (the SPLIT trial) did not find any difference in the rate of AKI or the utilization of renal replacement therapy in the group using saline or buffered crystalloid solution. The low volume of infused fluid (<2 L) was considered to be one of the factors that resulted in this lack of difference noted among the two goups., The lack of change in osmolality led to a similar brain relaxation. A more objective and definitive test to assess the blood flow may show differences in brain perfusion when using the two fluids for cranial surgeries. This effort by the authors should pave the way for a much larger trial to evaluate the benefits of balanced solutions over normal saline in the brain.
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