1. Blood pressure monitoring Monica Morosan

2. AAGBI standards of monitoring A - Induction and Maintenance of Anaesthesia 1. Pulse oximeter 2. Non invasive blood pressure monitor 3. Electrocardiograph 4. Airway gases: oxygen, carbon dioxide and vapour 5. Airway pressure The following must also be available 6. A nerve stimulator whenever a muscle relaxant is used 7. A means of measuring the patient’s temperature

3. Methods of BP monitoring Indirect: Mercury manometer Oscillometry Automatic oscillometric technique (DINAMAP) Radial arterial compression Finapress technique Microphone (Doppler) Direct (Invasive)

4. Mercury manometer BP determined by palpation or auscultation Korotkoff sounds

5. Oscillometry Aneroid gauge (Bourdon gauge) Measures high pressures Coiled tube connected to a pointer Bellows

6. Oscillotonometry Does not use palpation or auscultation 2 cuffs (occluding – upper, overlaps the sensing cuff-lower) Inflate both and release the occluding

7. DINAMAP Air pump Bleed valve Pressure transducer (measures both pressure and oscillations) Microprocessor

8. Problems Cuff too small-over reads Cuff too large-under reads Over reads at low BP, under reads at high BP Arrhythmias External pressure on cuff Nerve palsy Petechial haemorrhages

9. Radial artery compression Pressure sensor strapped to wrist Sensor driven hydraulically by a control system (applies pressure and senses oscillations) Algorithm –BP from table values

10. Finapress technique Cuff on finger – infrared LED and photocell- detects the volume of arterial blood in the finger Electronic processor analyses the photoplethysmograph to determine the volume at MAP

11. Microphone over artery Doppler changes

12. Invasive measurement

13. Indications for A line insertion Uses: Arterial pressure measurement Drug delivery (thrombolysis) Procedural access (angio) Mechanical support techniques (IABP, ECMO) Indications: Cardiovascular instability Vasoconstrictors/ Inotropes BP manipulation Blood sampling

14. Transducer Transforms one form of energy into another Based on Wheatstone bridge

15. Information from the trace BP (systolic, diastolic, MAP) Pulse rate Position of dicrotic notch reflects peripheral resistance Upstroke part reflects miocardial contractility

17. Resonance and damping Resonance -Measuring system posseses a resonant frequency -Oscilations occuring at this frequency will produce a sine wave superimposed on the BP waveform Damping -Property of a system to resist mechanical oscillations -Air bubbles -Clot

18. Step response

19. Complications: Medical (AV fistula, false anaeurysm, thrombosis, ischaemia, infection) Equipment (disconnection, loss wire, catheter fracture, inadvertent intra arterial injection of drugs)

20. Summary Direct Indirect Complications Sources of error