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59 Volume of circulatory blood

Circulating blood volume: normal values per kilogram, the Nadler formula, indicator dilution and causes of hypovolaemia.

The circulating blood volume is the total amount of blood in the heart and vessels: plasma plus blood cells. In adults it is about 65–70 mL per kilogram of body weight, roughly 5 litres in a 70 kg man. It depends on sex, body size and composition (fat tissue contains little blood), fitness, altitude and pregnancy. An adequate blood volume is necessary to fill the heart, maintain cardiac output and deliver oxygen to the organs. Hypovolaemia (low blood volume) is a major cause of shock.

HaemodynamicsHypovolaemiaOxygen delivery

Men≈ 68–70 mL/kg

Women≈ 65–69 mL/kg

70 kg adult≈ 4.5–5 L

Reference methodindicator dilution (labelled albumin or red cells)

Figure 1. Composition of the circulating blood volume. Plasma volume and red cell volume are measured separately with indicator dilution.

Estimation and measurement

The Nadler formula, based on radioisotope measurements, estimates blood volume from height, weight and sex:

Men: BV (L) = 0.3669 × H³ + 0.03219 × W + 0.6041

Women: BV (L) = 0.3561 × H³ + 0.03308 × W + 0.1833

(H = height in metres, W = weight in kg.) Direct measurement uses indicator dilution: a known amount of labelled albumin (plasma volume) or labelled red cells (red cell volume) is injected, and its concentration is measured after mixing. Newer methods use carbon monoxide rebreathing.

Clinical significance

Low blood volume results from bleeding, vomiting, diarrhoea, burns, excessive urination (diabetes, diuretics) or fluid shift into tissues. When blood volume falls, the body constricts vessels of the gut, skin and kidneys to preserve flow to the heart and brain. Prolonged hypoperfusion of the gut can damage its mucosa, allowing bacteria and toxins to enter the circulation and contributing to multiple organ failure. In high-risk surgical patients, an oxygen debt (inadequate oxygen delivery) was associated with organ failure and death.

High blood volume occurs in heart failure, kidney failure, excess sodium and fluid intake, hyperaldosteronism and pregnancy (physiological increase of about 40–50%).

Seek emergency care

for heavy bleeding, persistent vomiting or diarrhoea with dizziness, fainting, rapid pulse, cold skin or very little urine.

References

Nadler SB, Hidalgo JH, Bloch T. Prediction of blood volume in normal human adults. Surgery. 1962;51(2):224–232. PubMed 21936146
Shoemaker WC, Appel PL, Kram HB. Role of oxygen debt in the development of organ failure, sepsis, and death in high-risk surgical patients. Chest. 1992;102(1):208–215. doi:10.1378/chest.102.1.208
American College of Surgeons Committee on Trauma. Advanced Trauma Life Support (ATLS) Student Course Manual. 10th ed. Chicago: American College of Surgeons; 2018.

This article is for general information and does not replace a consultation with a doctor. Measurements must be interpreted by a physician together with symptoms and other tests.

Published on 29 April 2024