Need help with hyper, hypo, and isotonic solutions?

Daytonite, BSN, RN · Oct 1, 2007

Your scenarios here are examples of the three types of fluid volume deficit (dehydration) that occur. This is fluid and electrolyte theory, to be sure. I happen to have a very nice table that breaks all the information down on these three types of dehydration and it's kind of hard to post the information, but I'll try. This information is coming from page 477 of intravenous therapy: clinical principles and practice, by judy terry, leslie baranowski, rose anne lonsway and carolyn hedrick, published by the intravenous nurses society, 1995.

Isotonic fluid volume deficit

type of loss: solute and water loss proportional, no change in plasma volume, serum sodium level is decreased to 125-150 meq/l. The cause of the fluid loss is gi fluid loss, urine loss and decreased oral intake.

Clinical signs: poor skin turgor; cold, dry dusky skin; sunken eyes; dry mucous membranes; depressed fontanelles in babies; rapid pulse; low b/p; irritability or lethargy

fluid replacement guidelines: initially, a bolus of 0.9% sodium chloride or ringer's lactate is given followed by 5% dextrose in water and 0.45% sodium chloride. Half of the deficit should be replaced in the first 8 hours and the remaining half over the next 16 hours

Hypotonic fluid volume deficit

type of loss: more solute is lost than water. Plasma volume moves from the ecf to the icf. Serum sodium levels are decreased below 125 meq/l. The cause of the fluid loss is often a gi fluid loss with hypotonic oral intake.

Clinical signs: include very poor skin turgor; cold, clammy, dusky skin; sunken eyes; slightly dry mucous membranes; depressed fontanelles in babies; rapid pulse; very low blood pressure; lethargy; coma; seizures

Fluid replacement guidelines: initially a bolus of 0.9% sodium chloride or ringer's lactate followed by 5% dextrose in water and 0.9% sodium chloride. If the patient is severely symptomatic 3% sodium chloride at 4ml/kg should be given over 10 minutes with close monitoring. Half of the fluid deficit should be replaced in the first 8 hours and the remaining half over the next 16 hours.

Hypertonic fluid volume deficit

Type of loss: there is greater water loss than solute loss. Volume moves from the icf to the ecf. Sodium levels are maintained at over 150 meq/l. The cause is gi fluid loss with hypertonic oral intake, diabetes insipidus, fever and hyperventilation.

Clinical signs: include fair skin turgor; cold, thick and doughy skin; sunken eyes; parched mouth; depressed fontanelles in babies; a moderately rapid pulse; moderately low blood pressure; hyperirritability; high-pitched crying in babies; seizures.

Fluid replacement guidelines: 5% dextrose in water and 0.225% or 0.45% sodium chloride. If the patient is hypertensive 0.9% sodium chloride or ringer's lactate should be given at a rate of 20ml/kg over one hour. Fluid replacement should be given slow and gradual over 48 hours. 2 to 3 meq/kg of potassium should be given per 24 hours. At least 2 meq/l/hour of sodium should also be included in the iv fluids that are used.

In reading your scenarios and the answers I am wondering if the answers you give are yours or ones given to you by your textbook/workbook? The reason is because your answers do not seem to fit with the parameters I've listed above. However, I've given you reasons for the types of solutions your answers say to use.

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Patient with a history of severe congestive heart failure, admitted for tx of sepsis and dehydration. Bp=70/40, p-110, weak and thready.
Answer: give isotonic solution.
Why do you want to give a isotonic solution? Is it because that since the person is dehydrated, you do not want to overhydrate the cells with a hypotonic solution and you don't want to make the dehydration worse by giving him a hypertonic solution, thus you give him an isotonic solution?

Isotonic dehydration is where the loss of solutes and water is proportional. Therefore, you are going to give fluid replacement that is going to replace both elements (electrolytes and water) equally. Isotonic solutions are given for rehydration and to replace sodium and chloride. These solutions are used to replace extracellular fluid (ecf). The key factor is that these solutions have a sodium concentration that is similar to that of the extracellular fluid which effectively limits their fluid distribution to the ecf. The fluid distributes between the interstitial fluid (isf) and the plasma in proportion to their volumes. Intracellular fluid volume does not change.

Isotonic solutions include 0.9% sodium chloride, dextrose 5% in water, dextrose and 2.5% saline, dextrose 5% in water and 0.45% saline, lactated ringer's, dextrose 2.5% in 1/5 strength lactated ringers, 6% dextran and and 0.9% saline, 10% dextran and 0.9% saline and a number of formulated electrolyte solutions (I.e., normosol r, isolyte e, plasmalyte r).

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Patient, age 40, hypertensive, who has been on diuretic therapy. Skin and mucous membranes are dry, and he's complaining of a headache. Bp=200/120
Answer: give hypotonic solution
Is it because that since the skin and mucous membranes are dry you want to give a hypotonic solution so that the cells can become more hydrated than with a isotonic solution?

Hypotonic dehydration is where the loss of sodium is greater than the loss of water due to the diuretics. What has happened is the extracellular fluid has shifted into the intracellular space leaving free water in the extracellular spaces. Treatment is also fluid replacement, but the fluid needs to have extra sodium added to it which changes the iv solution to a hypotonic one.

There in only one hypotonic solution: 0.45% sodium chloride.

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A 35 year old patient who recently underwent abdominal surgery. Her ng tube is draining 1200 ml of fluid per shift, she's losing large amounts of acid and electrolytes. Abg analysis shows a ph of 7.60.
Answer: give hypertonic solution.
Is it because that since you lose the acid and electrolytes, you want to increase the osmolality by giving the hypertonic solution (such as hypertonic normal saline) to replace the electrolyte loss?

Hypertonic fluid volume deficit means that there is a greater proportional loss of water than there is of sodium. The extracellular fluid becomes hypertonic as a result and fluid in the intracellular spaces shifts out of the cell and into the extracellular space. These patients are rehydrated slowly with hypertonic solutions since rapid rehydration can result in seizures.

There are many hypertonic iv solutions. Most common you will see used are 5% dextrose in 0.45 sodium chloride, 5% dextrose in 0.9% sodium chloride, 5% dextrose in lactated ringer's injection, dextrose 10% in water and 3% sodium chloride.

ARRR10 · Oct 1, 2007

Ok... I think I am beginning to understand the concept. Thanks again Daytonite, I'll let you know how I do with Exam II in med/surg tomorrow? I have a weird feeling that this exam is going to be a tough one.

Daytonite, BSN, RN · Oct 1, 2007

Fluids and electrolytes is a very hard concept. Truth? I failed the crni (certified rn, intravenous) exam the first time I took it by one question. They sent me a letter telling me they hand scored my test to make sure they had the score correct. I missed the most questions in the section on fluid and electrolytes. I could have kicked myself because I thought I knew that stuff pretty well. This test costs $300 to take. So, I really studied over the next year and re-took it again after paying another $300 and the second time did a whole lot better on the fluid and electrolyte questions, passed and got my certification. I have great respect for norma metheny who wrote Fluid & Electrolyte Balance: Nursing Considerations because I practically lived, ate and slept with that book while studying for my second go around with the crni exam.

Good luck with your test today.

ARRR10 · Oct 2, 2007

Got a 81% but the teacher threw out some questions so I got a 89.71% and guess what, I got all the fluid and electrolyte portion of the test correct. Thanks Daytonite.