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?
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
Symptomatic hyponatremia occurs at what serum sodium level?
< or equal to 120mEq/L
Treatment of symptomatic hyperkalemia?
- Potassium removal
- Remove all sources of K+
- Kayexelate cation-exchange resin, which binds K+ in exchange for sodium (Orally 15-30g in 50-100mL 20% sorbitol; Rectally 50g in 200mL 20% sorbitol)
- Shift potassium intracellularly
- Glucose 1amp of D50 and regular insulin 5-10u IV (insulin response may be blunted in the acutely ill)
- Bicarbonate 1amp IV
- Nebulize with albuterol (10-20mg)
- Counteract cardiac effects
- Calcium gluconate 5-10mL of 10% solution (use cautiously in patients receiving digitalis as it may precipitate digitalis toxicity)
All measures are temporary and last 1-4 hours. Consider dialysis if measures fail.
Treatment for hypokalemia?
- Mild, asymptomatic: oral KCl 40mEq x 1 dose
(or KCl 20mEq IV q2h X 2 doses)
- Symptomatic: KCl 20mEq IV q1 x 4 doses
For IV repletion, no more than 10mEq/h is advisable (can increase t 40mEq/h if with continuous ECG monitoring.
Treatment of hypercalcemia?
Only if symptomatic (>12mg/dL), replete associated volume deficit, then induce a brisk diuresis with normal saline.
Critical level: 15mg/dL (may rapidly progress to death)
Treatment of hypocalcemia?
Ionized calcium <4mg/dL
- Calcium carbonate susp 1250mg/5mL q6h enterally
- 10% Calcium gluconate 2gIV over 1h x 1 dose
Recheck levels in 3days. Goal to achieve serum concentration of 7-9mg/dL. Correct associated deficits in Mg, K and pH.
Treatment of Hyperphosphatemia?
Phosphate binders (sucralfate, aluminum-containing antacids)
Calcium acetate tablets
Dialysis if with renal failure
Treatment of hypophosphatemia?
- Neutra-Phos 2 packets q6h per gastric tube
- KPHO4 or NaPO4 0.15mmol/kg over 6h x 1 dose
-KPHO4 or NaPO4 0.25mmol/kg over 6h x 1 dose
Recheck level 4h after end of infusion, if <2.5, begin oral packets or start KPHO4 or NaPO4 0.15mmol/kg IV over 6h X 1 dose
Treatment of Hypermagnesemia?
- Eliminate exogenous sources of Mg
- Correct concurrent volume deficits
- Correct acidosis
- Manage acute symptoms: Calcium chloride 5-10mL
Treatment of hypomagnesemia?
- MgSO4 0.5mEq/kg in NSS 250mL, IV infusion over 24h x 3days
- OR Milk of magnesia 15mL (~49mEq Mg) q24 per gastric tube; hold for diarrhea
Severe deficits (<1mEq/L):
1mEq/kq in NSS 250mL IV infusion over 24h X 1d, then 0.5mEq/kg in 250mL NSS IV over 24h X 2d OR
1-2g MgSo4 IV over 15minutes
- May give in 2 minutes if with torsades de pointes
- Simultaneous calcium gluconate can counteract adverse side effects of a rapidly rising Mg level and correct concurrent hypocalcemia.
Recheck Mg levels in 3days after each correction.
Replacement of ECF during surgery, to address both losses and sequestration, often requires how much fluid to support homeostasis?
500-1000mL/h of a balanced salt solution
In the initial postoperative period, an isotonic fluid should be administered. After the initial 24-48 hours, fluids can be changed to 5% dextrose in 0.45% saline. If with normal renal function, potassium may be added to the IV fluids.
The earliest sign of volume overload is?
Weight gain. The average postoperative patient not receiving nutritional support should lose approximately 0.25 to 0.5 pounds (0.11 to 0.23kg) per day from catabolism.