By Craig
Definition- study of blood flow Haemodynamic monitoring refers to monitoring of blood in the cardiovascular system Uses Is NB in the critically ill pt Can assist diagnosis and decision making in regards to treatment Guides appropriate usage of fluids during resuscitation aiming for specific haemodynamic targets
Monitoring can be non-invasive, minimally invasive and invasive It s use is correlated with the pt s clinical state Involves measuring the blood pressure, preload pressure, pulmonary artery pressure, left /right ventricular end diastolic pressures/ volumes, stroke volumes and variants and cardiac output.
Non invasive blood pressure Indirectly measures BP Problem, it can be unreliable when not used properly ( size of the cuff, under-or overestimate the actual BP) Contraindications to its use are relative Avoid in - in limbs with severe PVD - venous cannulation - arteriovenous fistulas - previous lymphnode clearance ( radical mastectomies ) Complications are rare -skin ulceration, oedema & bruising -ulnar nerve injury ( rare)
Monitors Bp directly by cannulating arterial vessel Advantages Monitors the arterial wave form, which can reveal more information about CO, SV, SVV Heart rate frequent arterial blood gas analysis Indications - unstable pt s needing beat to beat monitoring -during cardiovascular interventions Basics - the arterial wave changes as the pressure wave moves away from the proximal aorta - systolic pressure increases and the systolic portion of the wave narrows - Mean Arterial Pressure (MAP) remains the same - This is due to bifurcation, non compliance of the vessels ( arteriosclerosis), which leads waves bouncing back - It record artefacts wave due damping effects( over-damping and underdamping effects, due to air bubble, or long tubing)
Complications - vascular thrombosis -distal embolization(clot or air) -vascular spasm -accidental drug injection -infection (local and systemic) -damage to nearby structure ( heamatoma and nerve injuries )
Indicated in -central venous pressure monitoring -administration of drugs (vasopressors and potassium replacement) -parenteral nutrition Is a good approximation of a right atrial pressure Assumed to be a good indicator of right ventricular preload It was also used a guide for the fluid management Ideally the pressures are measured at the end of expiration Studies demonstrated that there is no association between the CVP and circulating blood volume and that the CVP does not predict fluid responsiveness CVP can be affected by changes on the venous tone, intrathoracic pressures ( intrinsic and extrinsic PEEP) in critically ill pt s on a ventilator Complications similar to the pulmonary artery catheterization (PAWP)
Introduced in the 1970 s Also known as Pulmonary artery occlusion pressure, it involves the use of vascular catheter with a flotation balloon place in the pulmonary artery Inflation of the balloon created a static column between the catheter tip and the left atrium It basically measured the left ventricular end-diastolic pressure (LVEDP), which was assumed to be representing left ventricular end diastolic volume(lvedv) or LV Preload Used in the ICU and operating room as haemodynamic monitor and fluid responsiveness Current evidence suggest it is a poor predictor of preload and volume responsiveness It can still be used as reflection of the left atrial pressure, only if the tip of the balloon is placed in the Zone 3 which at the level of the left atrium
It s use a LVEDP measurements affected by -Aortic insufficiency: actual LVEDP > PAWP -non compliant ventricle : PAWP< LVEDP -Respiratory failure : PAWP > LVEDP It assumes that the resistance in the pulmonary veins is negligible. elevated in critically ill pt s with hypoxemia, endotoxemia, ARDS
It can be used as a tool to measure Svo2 Calculations of Cardiac Output with the dilution methods using -Indocyanine ( green dye) -Radio isotopes -Chemicals ( sodium thiocyanate) -Thermal dilution
Damage to adjacent structures Perforation or rupture of pulmonary artery( leading to pulmonary infarction) Infection Air embolisation Dysrhythmia Right bundle block or complete heart block Valve damage
Thermal and other indicators injected into a central vein, circulate in the pulmonary system and all chambers of the heart detected in the systemic artery It gathers the following information, cardiac output, central blood volumes and extra-vascular lung water can be quantified Lithium dilution test -The advantage is that the Li can be injected in the peripheral vein and detected in an arterial line -The disadvantage is in abnormal cardiac shunts it can give wrong results, and it requires disposal of sampled blood
Uses two methods -ecchocardiography -doppler technique Echocardiography - measures systolic and diastolic volumes and the stroke volumes is calculated as difference of the two - problems : equipment is expensive and trained personnel are limited Doppler technique - it measures the velocities of all red blood cells moving in the path of the beam -in addition to stroke volume it provides information on the aortic flow -dopplers can be used oesophageal or transcutaneous
Positioned about 30-40cm from the teeth Offers alternative from the thermodilution techniques for monitoring CO and it s variations Advantages - training is easy and short, nurses can use it at bedside - it s small with a diameter of 6mm -minimally invasive( inserted nasally or orally) -contraindications are relative ( e.g. agitated pt s, pharyngo-oesophageal pathology, Aortic dissection or severe aortic coarctation) -used in sedated and ventilated pt s Disadvantages -assumes that the descending Aorta has 70% of CO -Affected by Aortic pathology -in abnormal upper and lower body blood distribution - affected by turbulence ( Tachycardia, Anaemia, Aortic valve diseases)
Continuous probes designed to measures trans-pulmonary(parasternal) and transaortic( suprasternal) cardiac output. Can be used in non sedated pt s alternative to thermal dilution techniques
Arterial pressure wave form analysis Considered minimally invasive and provides real time and continuous data that allow prompt response It analyses the systolic portion on the wave, uses SVV to predict fluid responsiveness Different products are available PiCCO -uses manual calibration (transpulmonary thermodilution) - thermo indicator injected via central vein and sensor in the arterial catheter - disadvantage is that it involves large vessel cannulation (femoral) LiDCO - pulse power calibration - calibration using an indicator solution Flo Trac/Vigileo - does not need calibrations - easy to use
Aortic dissection Arterial compression Atherosclerosis Atrial fibrillation and arrythmias
Non invasive method of monitoring pt s oxygenation of hemoglobin (Hb) It uses two light wavelength( infrared ) passed through pt s tissue to a photodetector on the other side. The amount of absorbed light is propotional to concentration(hb) Oxygenated Hb absorbs more light than the deoxygenated Hb HbO2 is compared to the total amount of Hb in the blood (expressed as a fraction) -% saturation= (HBO2/HbO2 +HB) by 100 Pulse oxymetry mostly used in ICU pt, critically ill. - it has good accuracy - it s simple and fast in detecting tissue saturation It can be a sensitive marker of hypoventilation.( low PaO2) Venous oxymetry is used to detect SvO2 ( maker of balance between whole body DO2 and VO2 ){ delivery and consumption} SvO2=DO2/VO2
It does not indicate respiratory sufficiency or oxygen metabolism at cellular level It does not replace the use of blood gas analysis( base excess, ph, PCO2 ) It can erroneous readings in a pt with hypovolaemia, on vasopressors, calloused skin or shivering. In carbonmonoxide poisoning may show normal saturation pt is hypoxic
Measurement of CO2 in the exhaled gas 2 methods colorimetric method and a infrared capnography Colorimetric - uses a litmus paper in a Infrared device Gastric tonometry device to measures CO2 - provides more quantitative measurements - placed in the expiratory tubing - marker of proper placement of ET tube - indirect indicator of cardiac output