Chapter Fourteen, part 2. Hypovolemic States
Channel Your Enthusiasm
Exploring the Use of Saline Solutions in Medical Practice
The chapter discusses the intricacies of using various saline solutions in medical contexts, focusing on sodium concentrations in isotonic and hypertonic solutions. It highlights the rationale behind choosing specific percentages of saline solutions over others for conditions like hyponatremia, emphasizing the balance between sodium and volume administration. Additionally, the conversation touches on the historical use of different intravenous fluid options, the shift towards normal saline post-operatively, and the effectiveness of bicarbonate drips in specific medical scenarios.
Outline Chapter 14 — Treatment
- Treatment
- Both oral and IV treatment can be used for volume replacement
- The goal of therapy are to restore normovolemia
- And to correct associated acid-base and electrolyte disorders
- Oral Therapy
- Usually can be accomplished with increased water and dietary sodium
- May use salt tablets
- Glucose often added to resuscitation fluids
- Provides calories
- Promotes intestinal Na reabsorption since there is coupled Na and Glucose similar to that seen in the proximal tubule
- Rice based solutions provide more calories and amino acids which also promote sodium reabsorption
- 80g/L of glucose with rice vs 20 g/L with glucose alone
- IV therapy
- Dextrose solutions
- Physiologically equivalent to water
- For correcting hypernatremia
- For covering insensible losses
- Watch for hyperglycemia
- Footnote warns against giving sterile water
- Saline solutions
- Most hypovolemic patients have a water and a sodium deficit
- Isotonic saline has a Na concentration of 154, similar to that of plasma see page 000
- Half-isotonic saline is equivalent to 550 ml of isotonic saline and 500 of free water. Is that a typo?
- 3% is a liter of hypertonic saline and 359 extra mEq of Na
- Dextrose in saline solutions
- Give a small amount of calories, otherwise useless
- Alkalinizing solutions
- 7.5% NaHCO3 in 50 ml ampules 44 mEq of Na and 44 mEq of HCO3
- Treat metabolic acidosis or hyperkalemia
- Why 44 mEq and not 50?
- Do not give with calcium will form insoluble CaCO3
- Polyionic solutions
- Ringers contains physiologic K and Ca
- Lactated Ringers adds 28 mEq of lactate
- Spreads myth of LR in lactic acidosis
- Potassium chloride
- Available as 2 mEq/mL
- Do not give as a bolus as it can cause fatal hyperkalemia
- Plasma volume expanders
- Albumin, polygelastins, hetastarch are restricted to vascular space
- 25% albumin can pull fluid into the vascular space
- 25% albumin is an albumin concentration of 25 g/dL compare to physiologic 4 g/dL
- Says it pulls in several times its own volume
- 5% albumin is like giving plasma
- Blood
- Which fluid?
- Look at osmolality, give hypotonic fluids to people with high osmolality
- Must include all electrolytes
- Example of adding 77 mEw of K to 0.45 NS and making it isotonic
- DI can be replaced with dextrose solutions, pure water deficit
- Case 14-3
- Diarrhea with metabolic acidosis
- He chooses 0.25 NS with 44 mEq of NaCl and 44 NaHCO3
- Talks about blood and trauma
- Some studies advocate delaying saline until penetrating trauma is corrected APR about to. Keep BP low to prevent bleeding. Worry about diluting coagulation factors
- Only do this if the OR is quickly available
- Volume deficit
- Provides formula for water deficit and sodium deficit
- Do not work for isotonic losses
- Provides a table to adjust fluid loss based on changes in Hgb or HCTZ
- Says difficult to estimate it from lab findings and calculations
- Follow serial exams
- Serial urine Na
- Rate of replacement
- Goal is not to give fluid but to induce a positive balance
- Suggests 50-100 ml/hr over what is coming out of the body
- Urine
- Insensibles 30-50
- Diarrhea
- Tubes
- Hypovolemic shock
- Due to bleeding
- Sequesting in third space
- Why shock?
- Progressive volume depletion leads to
- Increased sympathetic NS
- Increased Ang 2
- Initially this maintains BP, cerebral and coronary circulation
- But this can decrease splanchnic, renal and mucocutaneous perfusion
- This leads to lactic acicosis
- This can result in intracellular contents moving into circulation or translocation of gut bacteria
- Early therapy to prevent irreversible shock
- In dogs need to treat with in 2 hours
- In humans may need more than 4 hours
- Irreversible shock associated with pooling of blood in capillaries
- Vasomotor paralysis
- Hyperpolarization of vascular smooth muscle as depletion of ATP allows K to flowing out from K channels opening. Ca flows out too leading to vasodilation
- Glyburide is an K-ATP channel inhibitor (?) caused increased vasoconstriction and BP
- Pluggin of capillaries by neutrophils
- Cerebral ischemia
- Increased NO generation
- Which Fluids?
- Think of what is lost and replace that.
- Bleeding think blood
- Raise the hct but not above 35
- Acellular blood substitutes, looked bad at the time of this writing
- Di aspirin cross linked hemoglobin had increased 2 and 28 day mortality vs saline
- Colloids sound great but they fail in RCTs
- SAFE
- FEAST
- Points out that saline replaces the interstitial losses why do we think those losses are unimportant
- Pulmonary circulation issue
- Pulmonary circulation is more leaky so oncotic pressure less effective there
- Talks about the lungs be naturally protected from pulmonary edema
- Rate of fluid
- 1-2 liters in first hour
- Suggests CVP or capillary wedge pressure during resuscitation
- No refs in the rate of fluid administration section
- Lactic acidosis
- Points out that HCO can impair lactate utilization
- Also states that arterial pH does not point out what is happening at the tissue level. Suggests mixed-venous sample.
References
Why is Gonorrhea Called the Clap? - Nurx™
Here’s the piece we celebrated from David Goldfarb: The Normal Saline Ceremony - PMC
Potency of Oral Rehydration Solution in Inducing Fluid Absorption is Related to Glucose Concentration | Scientific Reports an interesting report on how
Isotonic versus hypotonic solutions for maintenance intravenous fluid administration in children
Here’s a study in the Lancet that explored use the bicarbonate infusion in severe metabolic acidosis. https://www.sciencedirect.com/science/article/pii/S0140673618310808
Joel briefly reviewed the issues with normal saline vs balanced solution and alluded to some of these reports: SMART Balanced Crystalloids versus Saline in Critically Ill Adults | NEJM And SALT-ED https://www.nejm.org/doi/10.1056/NEJMoa1711586
We did not discuss this article on LR in cirrhotics but this study lower incidence of adverse outcomes and did not show higher lactate levels Lactated Ringer's vs Saline Among Critically Ill Adults With Cirrhosis: A Secondary Analysis of the Isotonic Solutions and Major Adverse Renal Events Trial
Joel mentioned a Cochrane review of albumin that showed increased mortality: Human albumin administration in a critically ill patients: systematic review of randomised controlled trials
The SAFE Trial that exonerated albumin: A Comparison of Albumin and Saline for Fluid Resuscitation in the Intensive Care Unit | NEJM
JC mentioned this study: Comparison of 5% human albumin and normal saline for fluid resuscitation in sepsis induced hypotension among patients with cirrhosis (FRISC study): a randomized controlled trial and then this one: A randomized-controlled trial comparing 20% albumin to plasmalyte in patients with cirrhosis and sepsis- induced hypotension plus here is the CONFIRM Terlipressin plus Albumin for the Treatment of Type 1 Hepatorenal Syndrome | NEJM and ATTIRE A Randomized Trial of Albumin Infusions in Hospitalized Patients with Cirrhosis | NEJM
Amy taught us that the military do use hetastarch in emergencies- up to 1 liter. Here’s a study that looked at its use. Hydroxyethyl Starch or Saline for Fluid Resuscitation in Intensive Care | NEJM
And here’s a cool resource: Fluid resuscitation in haemorrhagic shock in combat casualties | Disaster and Military Medicine | Full Text
Anna reviewed European guidelines on volume resuscitation- Timing and volume of fluid administration for patients with bleeding - Kwan, I - 2014 | Cochrane Library
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