Hemodynamic Monitoring Flashcards
Radial Artery Catheterization
The radial artery is the most common site for invasive blood pressure monitoring because it is technically easy to cannulate and complications are uncommon.
Radial Artery Catheterization Technique
Needle Held 30- 45 degrees.
Dorsiflexion of the wrist should be mild at most to avoid attenuating the pulse by stretch or extrinsic tissue pressure. The course of the radial artery proximal to the wrist is identified by gentle palpation, the skin is prepared with an antiseptic, and a local anesthetic is injected intradermally and subcutaneously beside the artery. Arterial catheterization can be performed with a standard IV catheter or an integrated guidewire-catheter assembly designed for this purpose.
Radial Artery Catheterization Care
Extreme wrist dorsiflexion following establishment of an A line should be avoided to prevent injury to the median nerve.
Complication Risk: Radial A-line
Overall low risk Increased Risk: vasospastic arterial disease previous arterial injury thrombocytosis, protracted shock high-dose vasopressor administration, prolonged cannulation infection.
Allen Test
Technique: compress both the radial and ulnar arteries and asks the patient to make a tight fist, exsanguinating the palm. The patient then opens the hand, avoiding hyperextension of the wrist or fingers. As occlusion of the ulnar artery is released, the color of the open palm is observed.
Normally, the color will return to the palm within several seconds; severely reduced ulnar collateral flow is present when the palm remains pale for more than 6 to 10 seconds.
Predictive value of this test is poor
Ischemic injuries seen even in patients with Normal Allen test
Indications for A-line
Elective deliberate hypotension Wide swings in intra-op BP Risk of rapid changes in BP Rapid fluid shifts Titration of vasoactive drugs End organ disease Repeated blood sampling Failure of indirect BP measurement
A-line Transducer System
Transducer system- continuous flush device
System dynamics and accuracy improved by minimizing tube length, limit stop cocks, no air bubbles, the mass of fluid is small, using non compliant stiff tubing
calibration at level of heart (mid-axillary line/right atrium or meatus of ear/circle of Willis if concerned about cerebral perfusion as in sitting pt)
Zeroing and Leveling Transducer
All pressures displayed on the monitor are referenced to local atmospheric pressure
The phlebostatic axis is on the 4th intercostal space along the mid axilla line.
The phlebostatic axis is relevant for supine and up to 60 degrees of head-up tilt.
If the transducer has not been levelled to the phlebostatic axis, pressure readings will be either falsely high or falsely low.
A 20-cm difference in height produces a 15-mm Hg difference in pressure
High-low
Low- high
Position and A-line
This point must be specifically positioned relative to the patient to ensure correct transducer level. When a significant or unexpected change in pressure occurs, the zero reference value can be rechecked quickly by opening the stopcock and noting that the pressure value on the bedside monitor is still zero.
Despite successful transducer zeroing, the measured blood pressure values seem erroneous, and a malfunctioning pressure transducer, cable, or monitor should be suspected
Underdamped
Underdamped- Systolic pressure overshoots and additional small, non-physiologic pressure waves distort the waveform and make it hard to discern the dicrotic notch (If visible, dicrotic notch will be exaggerated).
Several oscillations during square wave test.
Saltatory rather than gradual transitions. Systolic will reported higher and diastolic lower.
Overdamped
Overdamped- waveform is recognizable by its slurred upstroke, absent dicrotic notch, and loss of fine detail. Such waves display a falsely narrowed pulse pressure, although MAP may remain reasonably accurate.
One oscillation during square wave test. Dicrotic notch will be hard to visualize. Low systolic and overestimated diastolic.
Causes of Underdamped:
Catheter whip or artifact
Stiff non-compliant tubing
Hypothermia
Tachycardia or dysrhythmia
Causes of Overdamped:
Loose connections Air bubbles Kinks Blood clots Arterial spasm Narrow tubing
Actions to assess and fix damped wave forms:
Actions: Damped Waveforms Pressure bag inflated to 300 mmHg Reposition extremity or patient Verify appropriate scale Flush or aspirate line Check or replace module or cable
Square Wave Test
Square Wave Testing
Square wave testing can have a direct impact on the validity and accuracy of the hemodynamic values which are obtained from the invasive monitoring device.
It assesses for adequately damped, over-damped, and under damped.
Adequately- damped waveform is when there are only two oscillations that follow the fast-flush wave. Oscillations should be no more than 1/3 the height of the previous oscillation. The subsequent transducing should demonstrate a clear arterial waveform with a discernable dicrotic notch.
Aline Complications
Nerve Damage Hemorrhage/ Hematoma Infection Thrombosis Air embolus Skin necrosis Loss of digits Vasospasm Arterial aneurysm Retained guide wire
ASA closed claims for A-lines
ASA closed claims for A-lines: 54% were related to radial artery use (ischemic injury, median or radial nerve injury, or retained wire fragment), less than 8% were associated with use of the brachial artery, and the remainder followed severe thrombotic or hemorrhagic complications after femoral artery monitoring
Complications of Direct Arterial Pressure Monitoring
Distal ischemia, pseudoaneurysm, arteriovenous fistula Hemorrhage
Arterial embolization
Infection
Peripheral neuropathy Misinterpretation of data Misuse of equipment
Aortic Stenosis
Aortic stenosis Pulsus parvus (narrow pulse pressure) Pulsus tardus (delayed upstroke)
Aortic Regurgitation
Aortic regurgitation Bisferiens pulse (double peak) Wide pulse pressure
Hypertrophic cardiomyopathy
Spike and dome (mid-systolic obstruction)
Systolic left ventricular failure
Pulsus alternans (alternating pulse pressure amplitude) inspiration)
Cardiac tamponade
Pulsus paradoxus (exaggerated decrease in systolic blood pressure during spontaneous
Pulse pressure variation
Pulse pressure variation (PPV) is calculated as the difference between maximal (PPMax ) and minimal (PPMin ) pulse pressure values during a single mechanical respiratory cycle, divided by the average of these two values.
Yields a %- PPV: grey zone of 9% to 13%, such that those below 9% should receive intravascular volume expansion, whereas those above 13% should not. For those between the two values, the measurement is not able to provide meaningful information and the decision should be made on other criteria
During positive pressure ventilation, increases in lung volume compress lung tissue and displace blood contained within the pulmonary venous reservoir into the left heart chambers, thereby increasing left ventricular preload. Simultaneously, the increase in intrathoracic pressure reduces left ventricular afterload. The increase in left ventricular preload and decrease in afterload produce an increase in left ventricular stroke volume, an increase in cardiac output, and in the absence of changes in peripheral resistance, an increase in systemic arterial pressure. In most patients the preload effects are more prominent, but in patients with severe left ventricular systolic failure, the reduction in afterload plays an important role in increasing ventricular ejection.
To measure PPV accurately: In general, mechanical ventilation with tidal volumes of 8 to 10 mL/kg, positive end-expiratory pressure of 5 mm Hg or greater, regular cardiac rhythm, normal intraabdominal pressure, and a closed chest are necessary to duplicate the experimental conditions.
Pulse Oximeter
Method of measuring hemoglobin oxygen saturation (SpO2)
Noninvasive
Measures transmission of light through a solution to the concentration of the solute in the solution
Application of Beer-Lambert Law
Typically used wavelengths of light are 660 and 940 nm
Pulse oximeter probe is composed of a light emitter and a photodetector
ASA/ AANA Standards for Basic Monitoring requires that variable pitch tone be audible when in use
Pulse Oximetry Uses:
Detection of hypoxemia Detection of perfusion Sites: fingers, toes, nose, ear, tongue, cheek Inaccuracy Malposition of probe Dark nail polish Different hemoglobin Dyes Electrical interference Shivering
Indications for Central Venous Cannulation
Central venous pressure monitoring
Pulmonary artery catheterization and monitoring Transvenous cardiac pacing
Temporary hemodialysis
Drug administration
• Concentrated vasoactive drugs
• Hyperalimentation
• Chemotherapy
• Agents irritating to peripheral veins
• Prolonged antibiotic therapy (e.g., endocarditis)
Rapid infusion of fluids (via large cannulas) • Trauma
• Major surgery
Aspiration of air emboli
Inadequate peripheral intravenous access Sampling site for repeated blood testing
Indications for Central Venous Cannulation
Central venous pressure monitoring
Pulmonary artery catheterization and monitoring Transvenous cardiac pacing
Temporary hemodialysis
Drug administration
• Concentrated vasoactive drugs
• Hyperalimentation
• Chemotherapy
• Agents irritating to peripheral veins
• Prolonged antibiotic therapy (e.g., endocarditis)
Rapid infusion of fluids (via large cannulas) • Trauma
• Major surgery
Aspiration of air emboli
Inadequate peripheral intravenous access Sampling site for repeated blood testing
Insertion Sites for CVCs
*Right internal jugular vein Left internal jugular vein Subclavian veins External jugular veins Femoral veins
RIJ Prefered
Reasons for this preference include the consistent, predictable anatomic location of the internal jugular vein, readily identifiable and palpable surface landmarks, and a short straight course to the superior vena cava. An internal jugular vein catheter is highly accessible during most surgical procedures and has a high rate of successful placement (90% to 99%)
LIJ
Cupola of the pleura is higher on the left, theoretically increasing the risk of pneumothorax. The thoracic duct may be injured during the procedure as it enters the venous system at the junction of the left internal jugular and subclavian veins.129 The left internal jugular vein is often smaller than the right and demonstrates a greater degree of overlap of the adjacent carotid artery.130 Most important, any catheter inserted from the left side of the patient must traverse the innominate (left brachiocephalic) vein and enter the superior vena cava perpen- dicularly. As a result, the catheter tip may impinge on the right lateral wall of the superior vena cava, increasing the risk of vascular injury. This anatomic disadvan- tage pertains to all left-sided catheterization sites and highlights the need for radiographic confirmation of proper catheter tip location. Finally, most operators have less experience performing left internal jugular vein cannulation, which leads to more adverse events and morbidity.
SC
Pneumothorax is the most common complication of subclavian vein cannulation, although unintended arterial puncture may actually be more frequent.
CVCs
7 french, 20 cm length, Multiport catheters most common
Placement usually not confirmed by XRAY in OR
Aspirate blood from all ports
After surgery, XRAY
Ideally, tip within the SVC, just above junction of venae cavea and the RA, parallel to vessel walls, positioned below the inferior border of clavicle and above the level of 3rd rib, the T4/T5 interspace, the carina, or takeoff right main bronchus
CVC Contraindications
R atrial tumor
Contralateral pneumothorax
Infection at site
Complications of Central Venous Pressure Monitoring
Mechanical Vascular injury
Arterial
Venous
Cardiac tamponade
Respiratory compromise
Airway compression from hematoma Pneumothorax
Nerve injury
Arrhythmias Thromboembolic
Venous thrombosis
Pulmonary embolism
Arterial thrombosis and embolism Catheter or guidewire embolism
Infectious
Insertion site infection Catheter infection Bloodstream infection Endocarditis
Misinterpretation of data Misuse of equipment
CVP monitoring
CVP pressures = RAP = RV preload.
CVP in a spontaneously breathing patient is approximately 2-7 mmHg
This rises about 3-5 mmHg during mechanical ventilation
CVP Waveform
5 Phasic Events
Three Peaks (a, c, v)
Two Descents (x, y)
Requires an understanding of the cardiac cycle
“a” wave
Caused by atrial contraction (follows the P-wave on EKG)
End diastole
Corresponds with “atrial kick” which causes filling of the right ventricle.
“c” wave
Atrial pressure decreases after the “a” wave as a result of atrial relaxation
The “c” wave is due to isovolumetric right ventricular contraction; tricuspid valve closed bulges back into the right atrium
Occurs in early systole (after the QRS on EKG)
The c wave always follows the ECG R wave because it is generated during onset of ventricular systole.
“x” descent
Systolic decrease in atrial pressure due to atrial relaxation
Mid-systolic event
“v” wave
ventricular ejection, which drives venous filling of the atrium
occurs in late systole with the tricuspid still closed
occurs just after the T-wave on EKG
“y” descent
Diastolic decrease in atrial pressure due to flow across the open tricuspid valve
Pulmonary Artery Pressure Monitoring is use for
Right-sided heart catheter used for direct bedside assessment of : Intracardiac pressures (CVP, PAP, PCWP/ PAWP) Estimate LV filling pressures Assess LV function CO Mixed venous oxygen saturation PVR and SVR Pacing options
Describe the make up Pulmonary Artery Pressure Catheters
7 french (introducer is 8.5 french) 110 cm length marked at 10 cm intervals 4 lumens distal port PAP second port 30 cm more proximal CVP third lumen balloon forth wires for temp thermister
Pulmonary Artery Pressure Monitoring indications
Indications: LV dysfunction Valvular disease Pulmonary HTN CAD ARDS/ resp failure Shock/sepsis ARF Surgical procedure: cardiac, aortic, OB
Pulmonary Artery Catheter Complications
Arrhythmias (including V-fib, RBBB, complete heart block)
Catheter knotting
Balloon rupture
Thromboembolism; air embolism
Pneumothorax
PA rupture
Infection (endocarditis)
Damage to cardiac structures (valves, etc.)
Relative Contraindications– WPW syndrome, Complete LBBB
Vena cava and RA junction
15
Right atrium
15-25
Right ventricle
25-35
Pulmonary artery
35-45
Wedged in pulmonary capillary
40-50
PCWP Waveform
‘a’ wave
The represents contraction of the left atrium. Normally it is a small deflection unless there is resistance in moving blood into the left ventricle as in mitral stenosis.
PCWP Waveform
‘c’ wave
The ‘c’ wave is due to a rapid rise in the left ventricular pressure in early systole, causing the mitral valve to bulge backward into the left atrium, so that the atrial pressure increases momentarily.
PCWP Waveform
‘v’ wave
The ‘v’ wave is produced when blood enters the left atrium during late systole.
Prominent ‘v’ wave reflect mitral insufficiency causing large amounts of blood to reflux into the left atrium during systole.
Cardiac Output Monitoring
Thermodilution Continuous thermodilution Mixed venous oximetry Ultrasound Pulse Contour
Transesophageal Echocardiography
7 Cardiac Parameters Observed Ventricular wall characteristics and motion Valve structure and function Estimation of end-diastolic and end-systolic pressures and volumes (EF) CO Blood flow characteristics Intracardiac air Intracardiac masses
Transesophageal Echocardiography Uses in OR
Uses in the OR: Unusual causes of acute hypotension Pericardial tamponade Pulmonary embolism Aortic dissection Myocardial ischemia Valvular dysfunction Valvular function Wall motion
Transesophageal Echocardiography complications
Complications: Esophageal trauma Dysrhythmias Hoarseness Dysphagia
AANA Standard 9: Monitoring and Alarms
Monitor, evaluate, and document the patient’s physiologic condition as appropriate for the procedure and anesthetic technique.
When a physiological monitoring device is used, variable pitch and threshold alarms are turned on and audible.
Document blood pressure, heart rate, and respiration at least every five minutes for all anesthetics.
a. Oxygenation Continuously monitor oxygenation by clinical observation and pulse oximetry. The surgical or procedure team communicates and collaborates to mitigate the risk of fire.
b. Ventilation: Continuously monitor ventilation by clinical observation and confirmation of continuous expired carbon dioxide during moderate sedation, deep sedation or general anesthesia. Verify intubation of the trachea or placement of other artificial airway device by auscultation, chest excursion, and confirmation of expired carbon dioxide. Use ventilatory monitors as indicated.
c. Cardiovascular: Monitor and evaluate circulation to maintain patient’s hemodynamic status. Continuously monitor heart rate and cardiovascular status. Use invasive monitoring as appropriate.
d. Thermoregulation: When clinically significant changes in body temperature are intended, anticipated, or suspected, monitor body temperature. Use active measures to facilitate normothermia. When malignant hyperthermia (MH) triggering agents are used, monitor temperature and recognize signs and symptoms to immediately initiate appropriate treatment and management of MH
e. Neuromuscular When neuromuscular blocking agents are administered, monitor neuromuscular response to assess depth of blockade and degree of recovery.
Cornerstones of Monitoring: Physical Assessment
Inspection, palpation, and auscultation
Examples:
Observing chest rise and fall & auscultation of breath sounds pre-op, after intubation, and when ventilatory parameters change
direct palpation of a pulse when a monitor value is questionable
direct observation of a beating heart during cardiac surgery or palpation of the aorta by the surgeon
inspection of mucous membranes, skin color, and skin turgor
hydration, oxygenation, and perfusion
inspecting the surgical field for blood loss, observing urine output
evaluating JVD
pupillary response
MANY other examples
Precordial or Esophageal Stethoscope
Minimally invasive, cost-effective continuous monitor
Continual assessment of breath sounds and heart tones
Precordial placed on chest surface
Esophageal placed 28-30 cm into esophagus
Very sensitive monitor for bronchospasm, airway obstruction, changes in HR/ rhythm
Electrocardiogram
Interval
If you need a more in-depth review of ECG, please read Miller Chapter 47 “Electrocardiography, Perioperative Ischemia, and Myocardial Infarction”
The lines are 1 mm apart, with every fifth line intensified. The speed of the paper is standardized to 25 mm/sec. On the horizontal axis, 1 mm represents 0.04 second, and 0.5 cm represents 0.20 second. On the vertical axis, 10 mm represents 1 microvolt (mV). On every recording, a 1-cm (1-mV) calibration mark should indicate that the ECG is appropriately calibrated (MIller’s Anesthesia (8th ed) p. 1430).
Electrocardiogram purpose
Purpose- detect arrhythmias monitor heart rate detect ischemia detect electrolyte changes monitor pacemaker function
Accurate detection of the R wave and measurement of the R wave–R wave interval serve as the basis from which digitally displayed values are derived and periodically updated (e.g., at 5- to 15-second intervals)- can lead to inaccuracies
Proper ECG Placement
3-Lead ECG
Electrodes RA, LA, LL
Leads I, II, III
3 views of heart (no anterior view)
Three-electrode monitoring
Is usually adequate for tracking HR, detecting R waves for synchronized direct-current shock in cardioversion, and detecting ventricular fibrillation. However, it is inadequate for diagnosing more complex arrhythmias for which a true V1 lead is necessary, such as to distinguish between right versus left bundle branch block (LBBB) or ventricular tachycardia (VT) and supraventricular tachy- cardia (SVT) with aberrant ventricular conduction. The three-electrode system is also inadequate for ST-segment monitoring because it does not provide multilead monitoring or precordial leads, which are often most sensitive for detecting ischemia.
5-Lead ECG
V1 is the preferred lead for special arrhythmia monitoring, whereas the other precordial leads, especially V3 to V5, are the preferred leads for ischemia monitoring. The five electrode monitoring system is currently the standard for monitoring patients with suspected perioperative myocardial ischemia
Proper ECG Placement
A majority of the dysrhythmias and ischemia seen during anesthesia can be detected by a combination of monitoring leads II and V5.
Gain Setting and Frequency Bandwidth
Gain should be set at standardization
1 mV signal produces 10-mm calibration pulse
Therefore, a 1-mm ST segment change is accurately assessed
Filtering capacity should be set to diagnostic mode
Filtering out the low end of frequency bandwidth can distort ST segment
ECG for Ischemia Detection
5 Principle Indicators:
ST segment elevation , ≥1mm T wave flattening or inversion Development of Q waves ST segment depression, flat or downslope of ≥1mm Peaked T waves Arrhythmias
Inferior wall ischemia
(right coronary artery) Changes in Lead II, III, AVF
Lateral wall ischemia
(circumflex branch of left coronary artery) Changes in Lead I, AVL, V5-V6
Anterior wall ischemia
(left coronary artery) Changes in V3-V4
Septal ischemia
(left descending coronary artery) Changes in Lead V1-V2
