Question

A 70 kg 68 y/o male sees his cardiologist for a follow-up following his myocardial infarction 3 months earlier. He has been taking digoxin and Lisinopril^TM since his MI. At the follow-up, he complains of shortness of breath and has to sleep sitting up in his recliner. He also complains of fatigability and swelling of his ankles and hands. A physical examination finds that he has distended jugulars and pitting edema in the lower legs. His breathing was rapid 22 breaths/min) and rales were heard in the both sides at the base of the lungs. He does not have a fever, but his pulse is 116 bpm and his blood pressure is 110/80. The physician immediately admits him and orders a blood and urine analyses with the results as follows:

Blood			Urine
[Na+]	128 mEq/L		[Na+]	150 mEq/L
[K+]	3.0 mEq/L		[K+]	65 mEq/L
[Cl-]	98 mEq/L		[Cl-]	120 mEq/L
[HCO3-]	21 mEq/L		[HCO3-]	15 mEq/L
Creatinine	1.2 mg/dl		Creatinine	128 mg/dl
PCO2	24 mmHg		24 hr volume	750 ml
pH	7.51		Osmolality	600 mOsm

a) Calculate the volumes of ECF and ECV in this Px assuming the total body osmoles of the Px is 12 Osm. Do these volumes have any impact on the symptoms the Px is exhibiting and what is the cause of these changes (what is the pathology)?

Answer 1

Patients weight = 70 kg

Total body water = 60 % of body weight (ICf = 40% = 28 kg & ECF = 20%= 14kg )

In the Px TOTAL Body water = 70 x 60/100 = 42 kg

Extracellular fluid (ECF) or extracellular fluid volume (ECFV) represents all body fluid outside of cells, and consists of plasma, interstitial, and trans-cellular fluid.

The ECF osmolarity is due to [Na + Cl] due to the normal functioning of the Na-K ATPase pump on cell membranes.

The disruption of Na-K ATPase pump activity as in hypoxia causes increased ICF Na, the water follows Na+ into cell and cellular swelling occurs. Or increased ICF occurs.

The ICF osmolarity is due to [K+] ions.

Serum Osmolality is normally within the range of 275-295 mOsmol/kg (milli-osmoles per kilogram)

When the cell membranes are freely permeable to water, the osmolality of the extracellular fluid (ECF) is approximately equal to that of the intracellular fluid (ICF). So that the plasma osmolality is a guide to intracellular osmolality.

The changes in ECF osmolality have a great impact on ICF osmolality and can cause problems with normal cell functioning and volume.

The hypotonic ECF allows water to readily fill surrounding cells, increasing their volume and potentially causes cytolysis., which will affect the homeostasis as a whole.

The osmolality of blood is directly proportional to dehydration and inversely proportional to overhydration.

The increased osmolality in the blood will stimulate secretion of antidiuretic hormone (ADH) in normal humans and eventually causes increased water reabsorption, more concentrated urine, and less concentrated blood plasma.

The low serum osmolality suppresses the release of ADH, resulting in decreased water reabsorption and more concentrated plasma.

The ankle oedema occurs when an excessive volume of fluid accumulates in the tissues.

The distended jugular vein indicates the increased CVP due to fluid overload.

Bilateral rales are small clicking, bubbling, or rattling sounds in the lungs may occur due to fluid overload.