CARDIAC OUTPUT CO Definitions normal values Cardiac output

CARDIAC OUTPUT (CO)

• Definitions & normal values: Cardiac output (CO) Stroke volume (SV) Cardiac index (CI) CI = CO at rest (Litres/minute) Body surface area (m 2) = -----Litres/minute/m 2 End diastolic volume (EDV) –

Contd: Ejection fraction (EF) – EF = Stroke Volume End-diastolic volume X 100 = ------ % End-systolic volume (ESV) – Cardiac reserve – = ------ %

30 1500 1250 1000 750 500 250 0 Tissues L L-Liver K-Kidneys 20 10 0 K B H Lungs S Others B-Brain H-Heart S-Skin Percentage of CO Blood flow m. L / min. Distribution of Cardiac Output (CO):

Conditions affecting Cardiac Output: • EFFECT: • Increase : CONDITIONS: Anxiety - Exercise - Environmental temperature. High altitude - Pregnancy - • Decrease : • No change : Postural change-

DETERMINATION OF CARDIAC OUTPUT (CO): I. DIRECT METHODS: a. Electromagnetic flow meter – b. Doppler with Echocardiography – II. INDIRECT METHODS: a) Direct Fick’s principle – b) Indirect Fick’s principle – c) Indicator dilution method – d) Thermodilution method – e) Echocardiography – f) Roentgenographic (X-ray) method –

I. DIRECT METHODS: 1. Electromagnetic flow meter – 2. Doppler with Echocardiography – Merits & Demerits of direct methods:

II. INDIRECT METHODS: a. Fick’s principle: O 2 consumption (m. L/min) = Q Blood flow (m. L)/min = Cardiac output (CO) Arterial O 2 content (m. L/100 m. L) = AO 2 Venous O 2 content (m. L/100 m. L) = VO 2 Q= CO x (AO 2 minus VO 2) O 2 consumption (m. L/min) CO = A-V O 2 difference (m. L/100 m. L) x 100

Contd: Blood sample: Arterial O 2 consumption = 250 m. L/min. Venous - AO 2 = 20 m. L/100 m. L of blood (200 m. L/L) VO 2 = 15 m. L/100 m. L of blood (150 m. L/L) b. Indirect Fick’s principle: CO 2 expelled (m. L/min) x 100 CO = V-A CO 2 difference (m. L/min)

c. Indicator dilution method: Dye: Evan’s blue - 1824 Amount of Dye injected CO = x 60 Average conc. of Dye x Circulation time (sec. )

Merits & Demerits of indirect methods: • Fick’s principle: • Dye dilution method: • Thermodilution method:

Factors affecting Cardiac Output: I. Factors affecting Stroke volume: II. Factors affecting heart rate:

I. Factors affecting Stroke volume: 1) Ventricular filling (preload): 2) Contractility: 3) Resistance (afterload):

1) Factors influencing Ventricular filling: a. Venous return – b. Atrial pump activity – c. Ventricular compliance –

a. Factors influencing venous return: i) Cardiac pump: ii) Respiratory pump: iii) Gravity: iv) Muscle pump: v) Venomotor tone: vi) Blood volume: b. Atrial pump activity: c. Ventricular compliance: