Understanding IV Fluids : Volume Resuscitation, Sepsis/septic shock DKA/HHS
Channel: QuickGuidesForMedicine
Date: 2020-07-13

In this video I talk about IV Fluids and different reasons for use such as in Volume resuscitation, septic shock, DKA/HHS, and specific compositions of the common IV fluids we encounter in the ICU and on medical floors. Feel free to jump to your preferred section via the timestamps below;

⏰ Timestamps:

Choosing IV Fluids - 0:58

IV fluid compositon - 1:30

Volume resuscitaiton - 7:36

DKA/HHS - 17:36

Selecting IV fluids whether during resuscitation or for maintenance hydration in the ICU or anywhere else in the hospital is often a tricky task. Balancing patient’s lab data with their IV fluid needs requires careful attention to detail and understanding of the composition of the IV fluids. 

We will go further to describe some of the scenarios where patients require IV fluid therapy and we’ll talk about the specific considerations in each scenario.

1. **Fluid resuscitation:**

Contrary to what you may see practiced, Lactated ringers (and other balanced crystalloids) have better outcome than Normal saline (Smart Trial). The chloride content, pH and Osmolality in LR are more similar to normal serum values compared to NS with a very high Sodium and Chloride content (Decreased Strong Ion Difference which is (0) with normal saline) with the chloride replacing lost bicarbonate and then causing hyperchloremic non-anion gap metabolic acidosis bypassing many of the intrinsic buffer systems.

***Why should I give LR in a patient with lactic acidosis or other existing acidosis commonly encountered in the ICU?***

Lactated Ringers contains Sodium Lactate and not Lactic acid which are 2 different things as the latter contains H ion and the former does not. Therefore, giving lactated ringers will not contribute to the acidosis, in fact it has a potential to push the serum towards alkalosis as ‘lactate’ acts as a buffer, eventually converted to Bicarbonate. Beware in patients with liver failure there may be a rise in serum lactate using LR as the liver is not able to metabolize lactate and apparent elevated lactate levels may cause concerns for the care team, however it is important to understand that the lactate here is not as a result of decreased tissue perfusion this is instead (Type B Lactic acidosis) and may not worsen patient’s condition and its also important to note that theoretically, vital tissues such as the brain and the cardiac tissue may use ‘lactate’ as source of fuel in cases of ischemia/hypoperfusion.

***Won’t the Potassium in Lactated ringers contribute worsen hyperkalemia?***

A 1 Liter bag of Lactated ringers contains about 4meq of potassium which in estimation would be less than potassium in an hyperkalemic patient so theoretically due to the distribution of potassium between ICF and ECF, there would tend to be a reduction in serum potassium by receiving the 4meq of potassium in the lactated ringers in an hyperkalemic patient. Also keep in mind that the alternative NS will likely cause normal anion gap metabolic acidosis which tends to trigger Hyperkalemia due to the effects of the H/K exchangers and if we remember that LR tends to make serum slightly more alkalotic, then we would see that possibility of worsening hyperkalemia is infact less with Lactated ringers compared to normal saline. Finally remember all the 40meQ of Potassium we freely give in a patient with hypokalemia with an expected 0.4meq rise in serum potassium? It would take giving a minimum 10L of LR to achieve the same effect.

***When should I avoid LR in fluid resuscitation?***

Although there is still a paucity of evidence to support this, it is probably safe to avoid LR in patients with traumatic brain injury as the slightly hypotonic features of lactated ringers may cause fluid shift in the CNS worsening tissue edema. It may also be reasonable to avoid LR in hyponatremic patients as this may be worsened due to low levels of Na in LR, would be advisable to use NS instead.

**In DKA/HHS?**

It is best to avoid NS due to the potential of worsening the already existing metabolic acidosis seen in DKA and occasionally in HHS. Most patients on continuous insulin infusion will require potassium so it is best to give this in a mix with **0.45% NS** or in LR. It is important to note though that it is ok to replace K in these patients separately from the main fluid therapy.
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