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Haemodynamic monitoring (Non-invasive BP monitoring (Types (Automated …
Haemodynamic
monitoring
Non-invasive BP
monitoring
Measurements
SBP: force of contraction
DBP: pressure during relaxation
Pulse pressure: difference SBP-DBP
MAP: average SBP/DBP
Types
Automated
Must align correctly with bladder on anterior, to compress artery
Need correct fit
Inflates autoatically to where SBP may be and goes over
Gradually deflates, detecting changes in pressure
Sphygmomanometer
Bladder placed over brachial, rest arm horizontal at midsternal level
Palpate brachial while inflating, pulse dissapears, go >30 over to account for the auscultatory gap
Place stethoscope on brachial, let down slowly to hear Korotkoff sounds
Physiology
Oscillometry used to measure SBP, MAP, DBP
Occlusion of arterial flow, no oscillations
When turbulant blood begins to flow, detect oscillantion (SBP), at its max, this is MAP, diastole calculated as an estimate
Errors
Cuff placement: bladder at front, small cuff (high reading),
large cuff (low reading)
Unreliable in irregular HR e.g. AF (different pressure changes)
Pain (high), white coat effect (high)
Advantages and disadvantages
Advantages: easy, cheap, non-invasive, minimal skill needed
Disadvantages: non-continuous, no additional information provided, less accurate
Arterial lines
(invasive BP monitoring)
Method
Arterial cannula inserted into radial artery
(can also use femoral, posterior tibial, drsalis pedis, brachial)
Allen's test beforehand to check ulnar collateral circulation
Connected to pressurised NaCl bags to ensure no backflow of blood into the giving set, plus flush to prevent line clotting
Column of saline in the giving set transmits the pressure changes to a transducer (BP, myocardial contractility, circulating volume)
Complications
Haemorrhage
Thrombosis, emboli
Infection
Accidental drug injection (NEVER EVENT)
Indications
Continous beat-beat BP measurement
Frequent ABGs
Advantages and disadvantages
Advantages: continous BP monitoring, accurate measures,
other info provided
Disadvantages: expensive, invasive, complications,
skill needed, resonance, dampening
Errors
Dampening (reduced transmission to transducer e.g. clot, line kinks/compression)
Resonance (oscillations causes by something other than arterial pressure picked up and measured by the line)
Central venous
lines/catheters (CVCs)
Method
Pressure trace generated by backpressure into the vein
Measures central venous pressure (CVP), i.e. pressure of SVC/RA,
filling pressure of R side of the heart
Affected by RA pressure, intravascular vol, venous tone,
pulmonary vascular resistance, intrathoracic pressure
Increases to max with RA contraction, decreases as it relaxes,
increases slightly as it starts to refill
Affected by RH pathology (RV failure, TV disease, SVCO, fluid overload, PH)
Complications
Early: pneumothorax, haemothorax, haemoatoma, haemopericardium, temponade, surgical emphysema, air embolus
Late: infection, thrombosis, stenosis, erosions, catheter fracture
Types
Direct access (short term; infection risk)
PICC lines (long term use, via arm vein)
Hickmann (long term use, surgically inserted)
Implanted ports (long term; surgically inserted)
Indications
IV access if peripheral not possible
CVP monitoring
Irritant substances e.g. chemo, TPN, vasoactive agents
RRT, transvenous pacing
Cardiac output
Non-invasive measurement
NIBP (impression)
Transoesophageal ECHO
Invasive
arterial lines, CV monitoring (impression)
Cardiac catheterisation/angiography
Dyes/thermodilution (conc vs time to get output)
Physiology
CO = HR X SV
Mean arterial
pressure (MAP)
Calculation
Average SBP and DBP
DBP + (SBP/DBP)/3
Physiology
Measurement of mean pressure in the arteries, as dictated by CO, SVR and central venous pressure
Normal range 65-105mmHg (<65 = hypotension)
