Critical Care Mailbag - IV Fluids

Critical Care Mailbag: IV Fluids

Scott Weingart MD and Rob Orman MD

PEARLS

• Normal saline makes patients more acidotic due to excessive chloride.

• Lactated Ringer’s was designed to not affect the acid-base status.

• Lactated Ringer’s should not be given to patients with brain injury as it is hypotonic.

• 3 amps of sodium bicarbonate in D5W or sterile water is a good option in a patient with a pre-existing, non-anion gap acidosis.

Is there any reason to not use Lactated Ringer’s over normal saline in an acidotic patient requiring fluid resuscitation?

• There are a few reasons but Lactate Ringer’s is probably the better choice.

• If you give a patient saline it will make them more acidotic due to the excessive chloride. The more saline that is given, the more chloride the patient gets and they develop a hyperchloremic metabolic acidosis. This is not a problem in a patient with functional kidneys that is not too sick; they will pee out the bad stuff and keep the good stuff. Studies have shown normal saline made healthy volunteers feel sick.

• In a sick patient, the kidneys might not be functioning well. They may be unable to reestablish their normal acid-base status.

• Lactated Ringer’s was designed to be given in copious quantities without affecting acid-base. It leaves patients at their normal acid base status. If they are acidotic, it will shift them toward normal. It is a good idea for many acidotic patients. There is no outcome data available for Lactated Ringer’s and it is unclear if it saves lives. However, there is some accumulating evidence that saline can lead to worsening kidney function in sick patients. Some studies indicate saline may cause more patients to die. These aren’t perfect randomized controlled trials. However, comparison of patients who received saline to those who didn’t showed increased renal damage and a tendency to increased mortality.

• Is there is a reason to not give Ringer’s. Ringer’s is a hypotonic solution. This doesn’t matter for most patients but patients with neurocritical care issues can have problems controlling intracranial pressure. Don’t give it to patients with a brain injury.

• Will it increase the lactate? Only if you gave a lot of it and the patient didn’t have a functioning liver. However, this does not give the patient a lactic acidosis but just increases the measured value of lactate. This can affect assessment of resuscitation. Until the lactate is cleared, the patient does not receive the acid-base benefits of the Lactated Ringer’s solution. It is the conversion by the liver or muscle that leads to a better situation than normal saline. Otherwise, the lactate sits there similar to chloride with normal saline.  There are a lot of organs that are able to take up lactate and it will clear eventually.

• There are options like PlasmaLyte and Normosol but not everyone has these available. We all have sodium bicarbonate. In general, Weingart does not support pushing sodium bicarbonate in acidotic patients as it does not improve the situation. However, if you put 3 amps of sodium bicarbonate in D5W or sterile water, you make an isotonic, alkalotic solution. It is fine for brain injury patients as well. This is the smartest way to go for a patient with a pre-existing, non-anion gap acidosis. Don’t administer it with a pressure bag as it has dextrose but you can run it in.
• This will fix hypertonic, hyperchloremic metabolic acidosis.
• This is the solution of choice if the patient has a renal tubular acidosis.

• There aren’t great studies demonstrating outcome problems with using Lactated Ringer’s in neurocritically ill patients but it is considered poor form.

• Patients with vomiting are losing HCl and should be given normal saline.  For diarrhea, give Lactated Ringer’s. For vomiting, give saline. However, most of your gastroenteritis patients will have functional kidneys and it doesn’t matter.