Non-invasive Monitoring in ICU

Non-invasive Monitoring in ICU

• ECG (Electrocardiogram): Monitors the heart's electrical activity using silver and silver chloride electrodes on the skin.
• ECG Measures: Heart rate (HR), arrhythmias, ischemia (lack of blood supply), and conduction defects.
• ECG Modes: Two modes exist: monitoring and diagnostic.
• Lead 2: Used to detect arrhythmias.
• Lead CM5: Used to detect ischemia (right arm on sternum, left arm on V5).

Problems in Practice (ECG)

• Correct Electrode Placement: Ensuring proper contact with conductive gel is crucial.
• Electrical Interference: Diathermy can cause interference.
• Muscle Activity: Shivering or other muscle activity can affect electrode placement and readings.
• High/Low Heart Rate: May make ischemia detection difficult.
• Diathermy Plate Placement: Incorrect positioning can cause burns.

Arterial Blood Pressure Monitoring

• Method: Oscillometry (most common) using a cuff with a tube for inflation and deflation.
• Mechanism: Microprocessor controls inflation/deflation; deflation produces oscillations, peak oscillation corresponds to systolic pressure.
• Cuff Size: Cuff size must be appropriate (2/3 of upper arm).
• Cuff Placement: Middle of the cuff bladder should be over the brachial artery.
• Mean Blood Pressure Calculation: = diastolic pressure + 1/3 pulse pressure (systolic pressure -diastolic pressure)

Problems in Practice (Arterial Blood Pressure)

• **Cuff Size/Inflation:**Too small, blood pressure is overestimated; too large, it's underestimated.
• Systolic Pressure: Can be incorrectly high at low pressure and low at high pressure.
• Arrhythmias: Affect readings.
• External Pressure: On the cuff or tube can cause errors.
• Repeated Cuff Inflation: Can lead to ulnar nerve palsy and petechial hemorrhages underneath the cuff.

Pulse Oximetry

• Technology: Significant advancement in monitoring; simple, accurate, and provides continuous display of arterial oxygen saturation.
• Use: Powerful monitoring tool in ICU, ER, OR, and general wards during transport.
• Probe Components:
  • Two light beams (red and Infra-red frequencies).
  • Sensitive photodetector
• Display: Continuous oxygen saturation, pulse rate, and plethysmographic pulse waveform.

Problems in Practice (Pulse Oximetry)

• Accuracy: Accurate within +/- 2 % in the 70-100% SpO2 range.
• Error Sources: Carbon monoxide poisoning, colored nail polish, IV dyes, certain medications, excessive movement/malposition, excessive external light, venous pulsations..

Capnography (CO2 Monitoring)

• Mechanism: Uses infrared radiation absorption by CO2 to create an electrical output.
• Types: Mainstream (no delay) or Side Stream (with delay).
• Use: Indicators for endotracheal intubation, ventilation levels, disconnections in ventilators; detects pulmonary embolism and malignant hyperthermia.
• Reading Delay: Reduced delay is better; desirable less than 4 seconds for accurate readings.

Invasive Monitoring - Arterial Pressure

• Method: Invasive arterial pressure monitoring using arterial cannula and heparinized saline column.
• Advantages: Provides beat-to-beat, real-time information.
• Measurements: Useful for cardiac contractility, vascular tone and stroke volume.

Central Venous Catheterization (CVP)

• Purpose: Measures central venous pressure (filling pressure of the right atrium).
• Uses: Fluid administration, blood sampling, drug administration, parenteral nutrition, hemofiltration, hemodialysis, and transvenous pacemaker placement.
• Insertion Routes: Internal jugular, femoral, basilic, subclavian (risks of complications, especially with femoral and subclavian).

Esophageal Doppler and Temperature Probes

• Esophageal Doppler: Measures hemodynamic parameters.
• Temperature Probes: Use thermistors, thermocouples, or infrared thermometers.
• Core/Skin Temperatures: Measured from rectum, esophagus, tympanic membrane, and the axilla; Axilla is best for malignant hyperthermia detection.