03 Fluid & Electrolyte Therapy Flashcards
Why is Lactated Ringer’s used rather than bicarbonate?
LR is slightly hypotonic in that it contains 130mEq of lactate. LR is used rather than bicarbonate because it is more stable in IV fluids during storage. It is converted into bicarbonate by the liver after infusion, even in the face of hemorrhagic shock.
How can sodium chloride lead to metabolic acidosis?
Sodium chloride is mildly hypertonic, containing 154mEq of sodium balanced by 154mEq of chloride. The high chloride concentration imposes a significant chloride load on the kidneys and may lead to a hyperchloremic metabolic acidosis.
NaCl however is an ideal solution for correcting volume deficits associated with hyponatremia, hypochloremia, and metabolic alkalosis.
Where are less concentrated sodium solutions employed?
0.45% Sodium chloride is useful for replacement of ongoing GI losses as well as for maintenance fluid therapy in the postoperative period. It provides sufficient free water for insensible losses, and enough sodium to aid the kidneys in adjustment of serum sodium levels.
Why is dextrose added to solutions with <0.45% sodium chloride?
The addition of 5% dextrose (50g dextrose per L) supplies 200kcal/L, and dextrose is always added to <0.45% sodium chloride solutions to maintain osmolality and thus prevent the lysis of red blood cells that may occur with rapid infusion of hypotonic fluids.
The addition of K+ is useful once adequate renal function and urine output are established.
Where is hypertonic saline used?
Hypertonic saline (3.5 and 5%) is used for correction of severe sodium deficits. 7.5% is used for closed head injuries, shown to increase cerebral perfusion and decrease ICP. (However there have been concerns also about increased bleeding, as hypertonic saline is an arteriolar vasodilator.)
What are the 4 types of colloids?
- Albumin
- Dextrans
- Hetastarch
- Gelatins
What are the disadvantages of albumin?
It can be associated with allergic reactions (blood derivative).
It has been shown to induce renal failure and impair pulmonary function when used for resuscitation in hemorrhagic shock.
What are the disadvantages of dextrans?
Glucose polymers produced by bacteria and grown on sucrose media, dextrans are associated with alterations in blood viscosity. Hence they are used primarily to lower blood viscosity.
What are disadvantages of hydroxyethyl starch?
Produced by hydrolysis of insoluble amylopectin, HES can cause hemostatic derangements related to decreases in vWF and factor VIII:C, leading to postoperative bleeding in cardiac and neurosurgery patients. Can also induce renal dysfunction (hyperchloremic acidosis).
What are the disadvantages of gelatins?
Produced from bovine collagen, both urea-linked gelatin and succinylated gelatin (Gelofusine) have been shown to impair whole blood coagulation time.
Treatment of hypernatremia?
- Treat associated water deficit. In hypovolemic patients, volume should be restored with normal saline before the concentration abnormality is addressed.
- Once adequate volume has been achieved, water deficit is replaced using a hypotonic fluid (5% dextrose, 5% dextrose in 1/4 normal saline, or enterally administered water).
- Rate of fluid administration should achieve a decrease in serum sodium of no more than 1mEq/h and 12mEq/day. 0.7mEq/L in chronic hypernatremia.
Formula used to estimate amount of water needed to correct hypernatremia?
Water deficit (L) = [(serum sodium - 140)/140] X TBW
Estimate TBW as 50% of lean body mass in men, 40% in women
Overly rapid correction of hypernatremia can lead to?
Cerebral edema and herniation
Treatment of hyponatremia?
- Free water restriction
- Sodium administration: If neurologic symptoms are present, 3% NSS should be used to increase the sodium by no more than 1 mEq/L per hour until the serum Na reaches 130mEq/L or symptoms are improved.
Rapid correction of hyponatremia can lead to?
Pontine myelinosis: seizures, weakness, paresis, akinetic movements, unresponsiveness, permanent brain damage and death
