Hemodynamic Monitoring

Cardiac Index

2.5-4.2 L/min/m2 should be sustained with a normal HR & SV. Affected by hypovolemia & pain.

17-20 mL/dL

Arterial Oxygen Content

95-100%

Arterial Oxygen Saturation

2.5-4.2 L/min/m2

Cardiac Index

58-104 (gm-m/beat)

Left Ventricular Stroke Work

22-30%

Oxygen Extraction Ratio

FloTrac

Pulse Contour CO Systems that use intra-arterial wave form analysis (alternative to PAC with injectate technique) which uses a formula (not calibration process) to continually update a constant used to determine CO & SVV using the patients BP, age, gender, & body surface area. CO is calculated from SV & HR. Needs an accurate arterial waveform- dysrhythmias, hypotension or equipment failure will alter the reading.

60-130 mL/beat

Stroke Volume

770-1,500 dynes/sec/cm-5

Systemic Vascular Resistance (SVR)

Pulmonary Artery Systolic (PAS)

reflects pressure from tricuspid to mitral valves & good indicator of PAP. COPD, acute respiratory distress syndrome, and pulmonary HTN will cause it toincrease.

Stroke Volume Variation

the difference between the maximum & minimum stroke volume during 1 mechanical breath relative to the mean stroke volume. It produces data changes in preload that occur from mechanical ventilation. It's used to predict if stroke volume will improve with volume repletion. Its accuracy is debatable & may be related to tidal volume & cardiac stability.

Systolic Pressure Variation

the difference between the maximum & minimum systolic blood pressure during 1 mechanical breath. It's used to estimate circulating volume, indicates decreases in CO from blood loss & can predict response to volume repletion. More superior then CVP & PAOP data.

Pulse Pressure Variation

the difference between the maximum & minimum values of arterial pulse pressure during 1 mechanical breath divided by the mean of the 2 values. Variations may predict response to fluid therapy if in shock & in surgery. Based on Frank Starling curve, it will decrease with increased preload. It is associated with Decreased preload & contractility. It may be more accurate indicator of fluid status then CVP, PAOP, SPV & SVV!

Doppler Methods

use ultrasound & Doppler effect to estimate cardiac output. Ultrasounds waves are reflected back to source at different frequency when they hit an object & it is related to the velocity of the moving objects & angle the US beam strikes. Probe placement is essential, different methods use different body sites.

Underdamped

waveform consists of an overresponse, exaggerated, narrow, artificially peaked tracing. Systolic BP will be too high & diastolic low. Results from small air bubbles, pressure tubing too long, defective transducer.

X Descent

*Atrial relaxation* & corresponding displacement of tricuspid valve during ventricular systole. May be absent in those with mitral reguritation.

Y descent

*opening of tricuspid valve* & blood exiting the RA (causing a decrease of right atrial pressure) & going into RV. It will be attenuated if if tricuspid stenosis due to obstruction to RA emptying.

Cardiac Output

Amount of blood ejected by heart each minute. It is affected by preload, afterload & contractility. Normal 4-8 L/min

30-65 mL/beat/m2

Stroke Volume Index

Elevated CVP

results from hypervolemia, increased venous tone, ventricular dysfunction, mitral or tricuspid valve disease, pulmonary hypertension, atrial fibrillation, high pericardial pressures (tamponade), high intrathoracic pressures (pneumothorax, positive pressure ventilation), & high intra-abdominal pressure.

Pulsaus Alternans

sign of decreased myocardial contractility which indicates the presence of severe ventricular systolic failure, such as tamponade.

Overdamped

waveform is sluggish & has exaggerated or falsely widened & blunt tracing. Systolic BP will be falsely low & diastolic high. Results from large air bubbles, loose connections, no or low fluid in flush bag, low pressure in flush bag, or kink in catheter.

Square Wave Test

"fast flush" or "dynamic response test" is preformed to assure all waveforms are accurate & show the true pulmonary artery pressures. Pull & release pigtail or squeeze the button of the flush device to increase flow through the tubing. This will cause sudden rise in pressure & generate a square wave but should revert to baseline within 1 or 2 oscillations. If response lacks in shape, amplitude, or time to return to baseline, troubleshoot. If underdamped or overdamped, the hemodynamic measurements will not be accurate. This should be done initially when system placed, at least 1x per shift, after opening the cath system (rezeroing, blood sampling, changing tubing) or if wave appears distorted. It may be affected by # of stopcocks, length of tubing, & air bubbles.

A Wave

*right atrium contraction*, corrsponds with *p-wave*. Will be absent if tricuspid stenosis, RV hypertrophy, pulmonary hypertension, pulmonary stenosis, or AF. Giant waves if RA contracts to eject blood to RV through a closed tricuspid valve in severe tricuspid stenosis. Prominent if there is pericardial constriction (tamponade).

Contractility

Ability of myocardial muscle to shorten or amount of strength produced when it ejects blood. Influenced by neural factors & metabolic states (hypoxia, hypercarbia, and acidosis).

Afterload

Amount of work the heart must do to eject blood, impedance or resistance to contraction. It reflects all things affecting tension of chamber wall during contraction (systole).

Central Venous Oxygen Saturation

CVP used to analyze blood sample for oxygen content- it should be greater than 70%. If less than 70%, tissues are extracting more oxygen then is normal indicating tissues do not perceive oxygen needs are met suggesting a bad outcome.

4-8 L/min

Cardiac Output

0-8 mmHg

Central Venous Pressure (Right atria)

Preload

Decreases from Bleeding & third spacing post op. Bleeding is a major problem because reduces oxygen carrying capacity. Bleeding results from CBP circuit due to platelet destruction, less clotting factors, inadequate hemostasis from incomplete heparin reversal or excessive protamine administration, or bleeding from suture site. Transfusion of blood products & clotting studies indicated. If HTN, must decrease BP to protect suture sites. Will need surgical reexploration. Drops in BP, cardiac filling pressure, & U/O indicate hypovolemia. Isotonic colliods or colloids (albumin, blood) used for volume replacement. If it is high= fluid excess so hold fluids, admin diuretic & vasodilators may be needed.

Intra-arterial pressure monitoring

Direct measurement of *arterial blood pressure* & is usually more accurate than indirect (ausculatory) measurements. Indicated post op cardiac surgery, drug therapy, & intra-aortic balloon pump & requires frequent monitoring. Also used to assess perfusion status if dysrhythmias. If used in peripheral artery, it will falsely elevate SBP due to amplitude of waveform but the MAP & DBP are accurate. Complications include risk of ischemia, thrombosis of extremity, infection, bleeding. Prolonged hyperextension of wrist may cause nerve damage. Assess for paresthesias, redness, extremity temperature & color. Armband may be used to stabilize the catheter.

Mean Arterial Pressure (MAP)

Driving force of peripheral blood flow & the preferred pressure to be elevated in unstable patients. It is usually displayed in parenthesis on the monitor. It does not change with pressure waveforms, it is a mean through the duration of the cardiac cycle. Normal 70-130 mmHg

Afterload

Increases result postop from severe LV dysfunction, hypovolemia, increased catecholamines, vasoconstriction, & hypothermia. Use volume related interventions & rewarming blanket, vasodilators. Decreases result fromvasodilitation so use pressors.

Pulmonary Artery Catheters (PAC)

Indicated to assess cardiac function, cardiac output, cardiac index, & intracardiac pressures. Ideal to measure within the LV however, risk of damage & arrhythmias so not done continuously so it is closest indicator & provides earlier indications of *changes in LV function* then CVP. Measures Pulmonary Artery Pressure (PAP), Pulmonary Artery Systolic (PAS), Pulmonary Artery Diastolic (PAD), Pulmonary Artery Mean (PAM), & POAP to determine fluid therapy & titration of vasoactive drugs. There is a lack of evidence for their use, in CABG patients had higher weight gain & longer intubation times & may be associated with higher morbidity & resource allocation. May be used in those with pulmonary hypertension, ⬇️ CO, hypovolemia, predicated postop hemodynamic instability & to assess response to therapy. Also in those undergoing CABG with poor LV performance, LV aneurysmectomy, recent MI, diastolic dysfunction, acute ventricular septal rupture, or insertion of LVAD. Used postop if sxs of RV failure. It should be able to distinguish between pulmonary HTN & RV ischemia. The capacity for continuous mixed venous oxygen saturation (SvO2) should be available.

50-62 (gm-m/m2/beat)

Left Ventricular Stroke Work Index 50-62 gm-m/m2/beat

Left Arterial Line

Line that can be used for direct admin of vasoactive infusions to bypass the pulmonary system. Not used often due to risk of air entry or cath dislodgement, as well as, tamponade with line removal.

S3/S4

May indicate decreased ventricular compliance.

70-105 mmHg

Mean Arterial Pressure

Central Venous Pressure (CVP)

Measures BP in *right atrium & vena cava*. It is influenced by intravascular volume, ventricular compliance, & intrathoracic pressure. Always assess patient to guide treatment. Help assure accuracy by measuring at *end-expiration* to minimize affect of intrathoracic pressure. Align transducer at *phlebostatic axis*. Complications may be site related (ie pneumo if jugular/subclavian). Risk of vascular injury reduced with real time ultrasound imaging during insertion. Minimize infection with sterile technique protocols- hand hygeine, barrier precautions, chlorhexidine skin antisepsis, careful site selection, antibiotic catheters. Review site daily. Complications include pneumothorax (usually during placement if internal jugular or subclavian), thrombus, infection, air emoli, vessel performation, cath shearing & embolization, thrombophlebitis, extravastion (into mediastinum, pericardoium, retroperitoneum, plueral cavity), hemothorax, vascular injury-hematoma, arterial laceration, perforation of superior vena cava, pericardial perforation, arterial puncture, subpleural hematoma, & uncontrolled venous bleeding.

0.5mL/kg/hr

Minimum Urinary output- Cardiac patients often have diuresis from hemodilution & osmotic agents from CPB & elevated ANP.

60-80%

Mixed Venous Oxygen Saturation

100mL/hr for 3 hours or 200mL for first 3 hours or 300mL in 1st hour postop

Notify MD if chest tube drainage exceeds

200-290 mL/min

Oxygen consumption

900-1,150 mL/min

Oxygen delivery

Passive leg raise (PLR)

Predicts that cardiac output will increase with volume expansion & to validate CVP findings with with patient supine in bed & raising legs to 45 deg for at least 1 minute to draw blood from venous system in abdomen & lower limbs to determine if volume deficit.

4-12 mmHg

Pulmonary Artery Occlusive (Wedge) Pressure

15-30/6-12 mmHg

Pulmonary Artery Pressure

LidCO

Pulse Contour CO Systems that use intra-arterial wave form analysis (alternative to PAC with injectate technique) that uses lithium dilatation to calibrate & the arterial pulse wave analysis through PulseCO. Access site is through the radial or brachial artery. Small dose of lithium chloride admin IV. CO is determined by dilatation curve from a lithium sensitive probe in the art line.

Pulse Index Continuous Cardiac Output (PiCCO)

Pulse Contour CO Systems that use intra-arterial wave form analysis (alternative to PAC with injectate technique) which requires femoral or axillar art line & thermodilutation is used for calibration. A thermistor catheter records aortic waveforms & CO is calculated based on area in systolic waveform. May not be accurate estimates of CO, esp. in hypothermic patients under CPB & upper body warming devices.

Pulmonary Artery Diastolic (PAD)

Reflects pressure between pulmonic & aortic valves used to indicate LV function if no obstruction.

Decreased CVP

Results hypovolemia, low cardiac output. Volume replacement & treat cause (too much diuretic, third spacing, bleeding, diaphoresis, vasodilatation?).

25-30/0-8 mmHg

Right Ventricular Pressure

8-16 (gm-m/beat)

Right Ventricular Stroke Work

5-10 (gm-m/m2/beat)

Right Ventricular Stroke Work Index

Murmurs

Sudden presence or absence of indicate changes in valve function.

69-177 dynes/sec/cm-5

Systemic Vascular Resistance Index

100-130/60-90 mmHg

Systolic/Diastolic BP

L arterial pressure

The earliest indicator of a change in LV preload if there is no obstruction to flow!

Hemodynamics

The study of the dynamics of blood circulation in order to determine the adequacy of cardiac output. It is monitored closely for changes in fluid status and cardiac health.

Preload

The volume of blood in the right atrium or left ventricle at the end of diastole or beginning of systole. It is quantified with central venous pressure (CVP) & pulmonary artery occlusion pressure (PAOP) which reflect the patients volume status. The end-diastolic volume (EDV) is related to the amount of stretch of the sarcomeres. Preload reflects all things affecting tension of the chamber wall at the end of filling (diastole).

12-15 mL/dL

Venous Oxygen Content

pulmonary artery pressure (PAP)

With no flow obstruction, it indirectly *reflects Left Arterial Pressure & the approximate LV end diastolic pressure* (LVEDP- "left sided preload").

Indirect (Austculatory) Measurements

affected by cuff size, underestimate actual SBP if hypotensive because Krokoff sounds become inaudible, best measurement of BP when at rest but underestimates DBP.

Stroke Volume

affected postop by preload, afterload & contractility. It drops if patient rewarmed (vasodilitation).

Mixed venous blood

amount of oxygen in systemic circulation after blood passes through tissues.

C Wave

bulging tricusid valve into right atrium at ventricular systole, corresponds with *QRS*. Will be large if tricuspid regurgitation.

Continuous Cardiac Output

cath that uses a warm tracer placed in the right ventricle & the thermal filament warms ever 30-60 sec & cardiac output calculated based on time in takes warmed blood to pass thermistor. It is averaged over 3-6 min. It is expensive and may delay response to changes in CO. It also hinders mobility in the pt and increases risk of ICU associated delirium.

Pulmonary Artery Mean (PAM)

continuous average of pressure in pulmonary artery during a single cardiac cycle since pressures increase with systole & decrease during diastole.

Contractility

decreases may result postop from changes in preload, increased afterload, or factors affecting myocardium (ischemia, ventrcle failure, aneurysms), electrolyte imbalance & tampanode. Optimize the preload & afterload & address cause. May need inotropes, vasodilators, IABP which may increase CO by 1L or biventricular pacing.

Arterial Pulse Contour CCO

estimates CO based on pulse contour analysis from the arterial pressure pulsation waveform which is proportional to stroke volume. The arterial pressure waveform not only calculates CO, but also stroke volume variance, & extravascular lung water to predict the response to fluid therapy. The waveform is measured through an art line but there are also non-invasive methods as well. The PVV is not clinically useful & digital pleth variability is not for routine practice.

Paradoxical pulse

exaggeration of the normal variation in the pulse during inspiratory phase of respiration, where pulse is weaker during inhalation.

V wave

filling of right atrium with a closed tricuspid valve, it corresponds with the *T wave*. Gaint if acute increase in pressure in the RV from tricuspid reguritation. Prominent if pericardial constriction (tamponade, pneumothorax).

valves!

may require higher filling pressures post op to maintain CO- no nitroglycerin.

Cardiac output

measured with Pulmonary artery catheter (PAC) via thermodilutation or Fick's method. A bolus is injected into RA, as the fluid mixes with the blood into the pulmonary artery the temperature change is measured. The amount of time it takes the cooled blood to move is used to calculate it. The longer time it takes for the cooled blood to pass, the lower it will be. Accuracy of this method depends on temperature of injectate, injectate technique, minimal manipulation of syringe, time between measurements, lack of obstruction to smooth injection, and pt position. It will be underestimated if there is an intracardiac right to left shunt or tricuspid regurgitation. It will be overestimated if there is a left to right shunt. Dysrhythmias will prevent mixing & alter the results as well.

Esophageal Doppler Technique

measures blood flow velocity in descending aorta with a Doppler in the esophagus. Pt is sedated & mechanically ventilated. CO calculated based on the diameter of the aorta, distribution of CO in aorta & flow velocity of blood in aorta.

Venous Oxygen Saturation

monitored continuously from certain type of PAC to measure oxygen delivery (amount O2 carried to tissue each min) & oxygen consumption (amount O2 used by tissue) = tissue oxygen balance. It reflects *tissue oxygenation & cardiopulmonary function*. Normal is 60-80%. Changes in oxygen delivery, consumption, or tissue oxygenation used to assess efficacy of treatment & may indicate deterioration. It should be investigated promptly. Affected by changes in preload, afterload, & contractility

Nexfin Monitor

noninvasive CO monitor that is completely noninvasive to determine hemodynamic parameters. It's connected by wrapping inflatable cuff around finger to clamp the artery at a constant pressure & applying counter pressure that is equal to arterial pressure to represent the brachial artery pressure waveform. This is a basis for CO. Results are not consistent.

Electrical Bioimpedance

noninvasive method to determine CO based on changes in thoracic impedance as blood is ejected from LV. The algorithm eliminates the impedance from other tissues & lung volume changes. Other method may be ET tube that measure electrical impedance in the ascending aorta.

Pulmonary Artery Occlusive Pressure (POAP)

obtained when the PAC balloon is inflated to reflect the pressure between the tip of the PAC & the aortic valve. Since it covers less area, it is more *reflective of LV function* & will closely equate to *left arterial pressure & LVEDP (LV preload)*. It may be greater than LVEDP, in some conditions such as mitral valve disease, high pulmonary vascular resistance, use of positive pressure ventilation (increase intrathoracic pressure), tachycardia & COPD. It may also be elevated after revascularization while having low volume status. It will be lower than the LVEDP if there is aortic regurgitation, noncompliant LV, or PE. It also normally slightly lower than the PAD (by <5mmHg). Balloon must be inflated to get reading which increases risk of pulmonary artery rupture, pulmonary infarction, pulmonary thrombosis, PE, & pulmonary artery hemorrhage. Therefore readings not done routinely, but done if acute change in clinical status or PAD occurs or if no correlation between it & PAD exists. Always minimize time of balloon inflation. Inflate balloon slowly to prevent migration of catheter into a smaller pulmonary vessel & rupture.