Normal Saline is a safe solution if you do not give litre of litres into a patient without checking BGA. The effect of pH-influence is based on the fact that in normal Serum sodium is around 140 and chlorid 104 mmol/l. If you infuse a normal saline solution (0.9%) wich contains sodium 154 and chlorid 154mmol you increase the ammount of chloride more than sodium. You add more negative ions (chlorid) into the blood. To keep the balance of positive and negative ions constantly postive hydrogen ions will increase in the serum. Defined chemically as the negative decimal logarithm of the hydrogen ion activity the pH will decrease in this scenario.

You can have the same effect if you infuse albumin solution.

For better understanding go to the emcrit.org website. There are some very go podcast concerning acid-base disorders. I recommend this site to every resident in our ICU.

Here is the link

http://emcrit.org/podcasts/acid-base-i/

It is safe. It is an isotonic solution and does not do much harm provided infused judiciously.

Another problem is renal function. A randomized, controlled, double-blind crossover study on the effects of 2-L infusions of 0.9% saline and plasma-lyte® 148 on renal blood flow velocity and renal cortical tissue perfusion in healthy volunteers. Conclusions: This is the first human study to demonstrate that intravenous infusion of 0.9% saline results in reductions in renal blood flow velocity and renal cortical tissue perfusion. This has implications for intravenous fluid therapy in perioperative and critically ill patients. NCT01087853.

I would not say that NS is safe because it is an isotonic solution. An isotonic solution may be unsafe in some patients and in certain circumstances. I would be grateful to Karosas if says something about the pathophysiology of reductions in renal blood flow velocity and of renal cortical perfusion.

Twelve healthy adult male subjects received 2-L intravenous infusions over 1 hour of 0.9% saline or Plasma-Lyte 148 in a randomized, double-blind manner. Crossover studies were performed 7 to 10 days apart. MRI scanning proceeded for 90 minutes after commencement of infusion to measure renal artery blood flow velocity and renal cortical perfusion. Blood was sampled and weight recorded hourly for 4 hours.

Results : There was a significant REDUCTION in mean renal artery flow velocity (P = 0.045) and renal cortical tissue perfusion (P = 0.008) from baseline after saline, but not after Plasma-Lyte 148. There was no difference in concentrations of urinary neutrophil gelatinase-associated lipocalin after the 2 infusions (P = 0.917).

And the second : an increase in chloride concentration ( property of 0.9 NaCl - 154mmol/l chloride ) causes specificaly renal vasoconstriction and decrease in GFR : an increase in the plasma chloride conc. by 12mmol/l above the normal leads to an increase in renal vascular resistance by as much as 35prc., a decrease in GFR by 20prc. and diuresis also. ( Zander R. Fluid management : 12-13, 2006. )

Thank you Karosas, the work is really interesting and I think it's important to investigate the pathophysiological causes of renal vasoconstriction and decrease in GFR , considering that in critically ill patients renal function may already be impaired by hypovolemia / hypoperfusion.

This is a very interesting matter. I work at the ICU and ER units where we frecuently find normal Anion Gap metabolic acidosis with high levels of chloride in patients that have previously received NaCl 0,9% in resuscitation. This sometimes makes the colleagues confuse about the origin of " persistent acidosis" . There is a growing evidence about deletereous efects of fluid overload in critically ill patients, including saline solution. Here is the link of one of the many publications regarding saline infusion in critical patients:

http://www.medscape.com/viewarticle/781538

Use of isotonic saline in critically ill patients is not only safe but life saving. However, as Ingo stated if you are infusing litres and litres of saline, one has to be concerned about metabolic acidosis. Perhaps in those cases where enormous quantities of saline is infused, the patient will develop signs and symptoms of circulatory fluid overload sooner or later than metabolic acidosis.

As I said in another forum, I recommend reading: Resuscitation Fluids JA Myburgh and M. G. Mythen | N Engl J Med 2013, 369:1243-1251. It is a very interesting review article with types, compositions, and recommendations for use. I agree with the comments of Dr. Iqbal

Studies in critically ill patients due to cholera has shown that mortality is high when saline is used to correct volume depletion . Diarrhea causes sodium & bicarbonate loss leading to volume depletion & metabolic acidosis . Replacement with saline corrects volume depletion , but worsens metabolic acidosis . Metabolic acidosis causes vasodilation of blood vessels & myocardial depression worsening shock & increasing mortality . It was the development of ringer lactate which improved survival in cholera patients . Therefore , in patients in critically patients where metabolic acidosis plays an important role , ringer lactate is preferred over saline . These aspects have been discussed in my article ' Acute renal failure due to Acute diarrheal disease ' which is available in RG . The work done by CCJ Carpenter in Asiatic Cholera has been highlighted in this article . Saline can be used in patients in whom shock should be corrected in situations such as massive bleed , till blood becomes available . Therefore , the role of saline would depend on the cause of shock .

The causes of shock are hypovolemia , cardiogenic , sepsis , anaphylaxis & endocrinal . Hypovolemic shock is due to blood loss , plasma loss & fluid & electrolyte loss from vomiting , diarrhea , drains & massive diuresis . In the emergency room , saline would be the fluid of choice to stabilize the patient , till the cause is evaluated . In vomiting , saline would be the fluid of choice , while in diarrhea , ringer lactate would be required .Cardiogenic shock would need inotropes , rather than fluids . The choice of fluids in sepsis can be saline or ringer lactate & multi organ failure would determine prognosis . Anaphylaxis would need adrenaline & steroids along with saline to stabilise the patient . The fluid of choice in diabetic ketoacidosis is saline even with acidosis , since this is corrected with insulin . Though fluid therapy plays an important role in stabilizing the patient in shock , it is complications such as ARDS & AKI that determine further need of fluid therapy . The prognosis in critically ill patients depends on multiple factors & the role of saline in causing hypercholeremic acidosis should be evaluated . Albumin is expensive as an initial fluid therapy .

There is a great review about N/S in Lancet that will put into question some things about the infusion

This is an exciting topic

Hemorrhagic shock: The "physiology approach"Journal of Emergencies, Trauma and Shock

2012 | journal-article

• DOI: 10.4103/0974-2700.102357
• EID: 2-s2.0-84870281554

Depend on the underlying pathology for that critical patients