Anesthesia Patient Monitoring

• Patient Monitoring by Dr. Vasil Khachiashvili of Todua Clinic

Basic Anesthetic Monitoring

• Circulation is monitored via ECG and Non-Invasive Blood Pressure (NIBP)
• Oxygenation is monitored via SpO2
• Ventilation is monitored via EtCO2
• Temperature is monitored in degrees Celsius (°C)

Additional Monitoring

• Invasive blood pressure monitoring is an additional monitoring technique
• CVP monitoring is an additional monitoring technique
• Neuromuscular blockade monitoring is an additional monitoring technique
• Cardiac function monitoring is an additional monitoring technique
• Central nervous system activity, using BIS, is an additional monitoring technique
• MAC monitoring is an additional monitoring technique

Cardiovascular System Monitoring

• ECG
• Blood Pressure can be monitored invasively or noninvasively
• Pulse Pressure Variation
• Capillary Refill Time
• The difference between central and peripheral temperature
• Pletismogram
• Ultrasound
• Capnography
• Diuresis

ECG

• An ECG signal does not guarantee cardiac contraction and output
• Electrode pads are placed for leads II and V5, the most common placement
• Methods include electrode locations, filtering of noise, ST segment changes, rhythm detection, and ischemia detection
• Monitoring leads II and V5 allows for ischemia detection in 95% of patients because it monitors a large area of the myocardium
• Lead II monitors the inferior portion of the heart, supplied by the right coronary artery
• Lead V5 monitors the bulk of the left ventricle, supplied by the Left Anterior Descending artery
• RED electrode (RA): placed under the right clavicle near the right shoulder, within the rib cage frame
• YELLOW electrode (LA): placed under the left clavicle near the left shoulder, within the rib cage frame
• GREEN electrode (LL): placed on the left side below pectoral muscles lower edge of left rib cage

Blood Pressure - Noninvasive

• Measured as Systolic and Diastolic
• Mean arterial pressure (MAP) is calculated as Diastolic pressure + 1/3 (systolic - diastolic)

Blood Pressure - Invasive

• Invasive Arterial Line Placement
• Indications include the need for tight blood pressure control, such as during induced hypertension or hypotension, or with volume shifts
• Used for hemodynamically unstable patients
• Helps with frequent arterial blood sampling
• Used when noninvasive blood pressure measurements are not sufficient

Arterial Canulation

• Ultrasound-guided radial artery cannulation

Arterial Pressure Waveform

• An overdamped waveform happens due to arterial obstruction, catheter occlusion, excess tubing, stopcocks, air bubbles, or kinking of the pressure tubing
• An underdamped waveform is due to the use of nonrigid tubing or pressure bag malfunctioning

CVP - Waveform Indications

• Measurement of right heart filling pressures to assess intravascular volume and right heart function
• Drug administration to the central circulation
• Intravenous access for patients with poor peripheral access
• Indicator injection for cardiac output determination
• Access for insertion of a pulmonary artery catheter (PAC)

Advanced Hemodynamic Monitoring

• Cardiac Output Analyzer Devices

Cardiac Output Analyzer Devices

• Point-of-care echocardiography
• Thermodilution-based devices
• Lithium dilution-based devices
• Arterial pulse waveform analysis
• Aortic Doppler
• Thoracic electrical bioimpedance or bioreactance
• CO2-Based Cardiac Output Methods

Comparison of Cardiac Output Monitors

• Pulmonary Artery Flow Catheter (PAFC): Uses thermodilution, is high invasiveness, uses a PA catheter, is continuous, and is limited by shunts and arrhythmias
• Lithium Dilution Cardiac Output (LIDCO): Uses lithium dilution + pulse contour analysis (PCA), is moderate invasiveness, can be used with any venous + arterial line, is continuous, and requires good quality waveform
• Pulse Induced Contour Cardiac Output (PICCO): Uses thermodilution + pulse contour analysis (PCA), is moderate invasiveness, uses a central venous + arterial line, is continuous, and requires good quality waveform
• ProAQT: Uses pulse contour analysis, is low invasiveness, uses an arterial line, is continuous, and waveform dependent
• Transesophageal Echocardiography (TOE): Uses doppler/two-dimensional imaging, is moderate invasiveness, does not need lines, is not continuous, and is user-dependent and needs sedation
• Transthoracic Doppler (TOD): Uses doppler, has low invasiveness, does not need lines, is continuous, is user-dependent, and may pick up interference from other vessels
• Noninvasive Cardiac Output (NICO): Uses partial CO2 rebreathing Fick principle, low invasiveness (although requires intubation), no lines, is continuous, but needs intubation and is poor accuracy in lung disease
• Thoracic Impedance Cardiography (Transthoracic Impedance): Uses the measurement of change of impedance, has low invasiveness, uses no lines, is continuous, and is inaccurate in critically ill patients in general

Hemodynamic Monitoring Techniques in Non-Cardiac Surgery Studies

• EuSOS 2012 indicated that 74% of usage came from Pulse Countour, 18% from Doppler and 4% from Swan
• Relief 2018 indicated that 73% of usage came from Pulse Countour, 10% from Doppler and 17% from other unspecified measurements

Pulse Contour Parameters

• PCCO - Pulse Contour Cardiac Output (Continuous)
• ABP - Arterial Blood Pressure
• HR - Heart Rate
• SV - Stroke Volume: 50-110mls

Volume Responsiveness

• SVV - Stroke Volume Variation: <10%
• PPV - Pulse Pressure Variation <10%

Afterload

• SVR - Systemic Vascular Resistance
• SVRI - Systemic Vascular Resistance Index: 1700-2400 dynscm-5*m2

Contractility

• dPmx - Index of left ventricular contractility

Thermodilution Parameters

• CO - Cardiac Output: 4 - 8litres/min
• CI - Cardiac Index : 3- 5litres/min/m2
• GEDI - Global End Diastolic Index: 680-800ml/m2
• ITBVI - Intra Thoracic Blood Volume Index: 850-1000ml/m2
• SVR - Systemic Vascular Resistance
• CFI - Cardiac Function Index: 4.5-6.5%
• GEF - Global Ejection Fraction: 25-35%
• ELWI - Extravascular Lung Water Index: 3-7mls/kg
• PVPI - Pulmonary Vascular Permeability Index: 1.0-3.0

Novel Tools for Hemodynamic Monitoring

• Optimized Fluid Therapy balances 'Restrictive' fluid therapy and 'Liberal' fluid therapy around a optimal Fluid balance

Frank-Starling Curve

• The Frank-Starling curve plots Cardiac Output (CO) against Left Ventricular End-Diastolic Volume (LVEDV)

Battle of Two

• Static Macrocirculatory Hemodynamics includes Mean Arterial Pressure (MAP), Central Venous Pressure (CVP), and Pulmonary Artery Occlusion Pressure (PAOP).
• Dynamic Parameters includes Pulse Pressure Variation (PPV, Stroke Volume Variation (SVV), and Passive Leg Raising (PLR).

We used to overvalue CVP

• Central venous pressure must not be used to diagnose a volume deficit in spontaneously breathing or ventilated patients-prohibition applies to both perioperative and intensive care patients
• International Guidelines for Management of Sepsis and Septic Shock (2016) suggest dynamic over static variables be used to predict fluid responsiveness (weak recommendation, low quality of evidence).

Dynamic Variables

• Pulse Pressure Variation (PPV)- >13% is Positive; and <9% is Negative with a Gray Zone from 9-13%
• Stroke Volume Variation (SVV)- >10% is Positive

PPV and SVV Limitations

• Spontaneous breathing activity
• Cardiac arrhythmias
• Low tidal volume
• Low lung compliance
• Open thorax
• Increased intra-abdominal pressure
• Low HR/RR ratio <3.6

Passive Leg Raising (PLR)

• Passive Leg Raising (PLR), when Positive, exhibits Cardiac Output >10%

Sensitivity and specificity of Dynamic parameters

• Mini Fluid Challenge is measured against: Pulse pressure variation (PPV), Stroke Volume Variation (SVV), passive leg raising (PLR), and EtCO2 variation measuring IJV Distensibility
• Oximetric waveform measured against: IVC assessement
• Pulmonary Artery Catheter assessed against: pulse contour analysis (PCA), Transthoracic Echocardiography (TTE

Pulmonary Artery Catheter

• The Fick equation is: Svo2=Sa02-V02/CO×Hbx1.34

Respiratory System Monitoring

• Mandatory respiratory monitors used during general anesthesia include pulse oximetry, capnography, inspired oxygen analyzer, and disconnect alarm systems
• Direct visualization of the chest and a precordial or esophageal stethoscope may provide additional information

Mind the Following

• Methylene blue, indocyanine green, and indigo carmine uses
• Isosulfan blue injections transiently result in falsely low saturation readings
• Methemoglobinemia occurs when red blood cells (RBCs) contain methemoglobin at levels higher than 1%

Temperature Monitoring

• Indications include a need to control temperature during induced hypothermia and rewarming, infants and small children thermal liability due to high surface area-to-volume ratio, adults subjected to large evaporative losses or low ambient temperatures, febrile patients, and patients with autonomic dysfunction are unable to autoregulate their body temperature
• Malignant hyperthermia is always a possible complication, and temperature monitoring should always be available

Bispectral Index (BIS) Monitoring

• Monitoring The BIS monitor is the first method that is FDA approved to assess the hypnotic effects of drugs

Neuromuscular Block Monitoring

• Train of four (TOF) is where muscles are electrically stimulated 4 times in rapid succession & the number of contractions are noted. This is used to titrate NMB to the minimum effective dose
• After achieving adequate sedation, electrodes are applied and the nerve is stimulated using a low current (10-20 mA)

Intrabdominal Pressure (IAP)

• Intrabdominal Pressure can be measured via Bladder, Direct Peritoneal, Gastric, or Rectal Pressures

Intracranial Pressure (ICP)

• Intracranial Pressure can be measured using ICP monitoring devices using Intraparenchymal fibreoptic catheter, Epidural transducer, Ventriculostomy, or Subdural catheter

Near-Infrared Spectroscopy (NIRS)

• Note the regional tissue venous saturations are only detected in the superficial area of cerebral cortex