Monitoring in Anaesthesia and ICU.

Dr Amupitan.

Outline

• Introduction
• Standards of monitoring
• Types of monitors
• Conclusion

Introduction

• Monitors used during anaesthesia are established with patient safety in mind
• The monitoring devices are able to do so by yielding useful information about the patient’s condition and providing early warning of any physiological derangement.
• However, they should be used in conjunction with careful clinical observation of the patient.

• One of the primary responsibility of the anaesthetist is to act as a guardian of the anaesthesized patient during surgery.

Standards of basic anaesthetic monitoring.

• Standard I - qualified anaesthesia personnel shall be present in the room through out the conduct of all general anaesthesia , regional and monitored anaesthetic care.
• Standard II – during anaesthesia, the patient’s oxygenation, ventilation, circulation and temperature shall continually be evaluated.

Types of monitors.

• Cardiac monitors – arterial blood pressure, ECG, central venous pressure,
• Pulmonary monitors- capnography, pulse oximetry
• Miscellanous monitors – temperature monitoring, urine output , precordial stethoscope, neurological monitoring, neuromuscular blockade.

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Cardiac monitors.

• Arterial blood pressure
• This can be non invasive or invasive
• Blood pressure monitoring mandatory in patients undergoing anaesthesia.
• Non invasive blood pressure monitoring done with use of manual or automated sphgmanometer.

Invasive blood pressure monitoring

• Indications
• Induced hypotension
• Anticipation of wide blood pressure swings
• End organ disease necessitating precise beat to beat blood pressure regulation
• Need for multiple arterial blood gas analysis.

• Arterial cannulation allows continuous BP monitoring.
• The arterial cannula is connected to a pressure transducer system and the pressure waveforms are displayed on the monitor.
• Sites for arterial cannulation include radial, brachial,femoral and dorsalis pedis arteries.

• Other less common sites for cannulation include axillary, popliteal and posterior tibial arteries.
• Complication of invasive BP monitoring.
• Thrombosis
• Distal embolization of thrombus
• Bruising, haematoma, arteriovenous fistula
• Local or systemic sepsis.

• Electrocardiography (ECG) – all patients should have intraoperative ECG monitoring.
• ECG is a recording of the electrical potentials generated by the myocardial cells.
• Ideal for detection of cardiac arrythymias and ischaemia.
• Used for detection of conduction abnormalities and electrolyte disturbances.

Central venous catheterization

• Indications
• Monitoring of central venous pressure
• For administration of fluid for hypovolaemia and shock.
• For infusion of caustic drugs and total parenteral nutrition.
• For aspiration of air embolus
• For gaining venous access in patients with poor peripheral veins.

• Contraindication
• Fungating tricuspid valve vegetations
• patients receiving anticoagulant therapy
• Patients who have had an ipsilateral carotid endarterectomy because of possibility of unintentional carotid artery puncture.

• Central venous cannulation involves introducing a catheter into a vein so that the catheter tip lies just above or at junction of superior vena cava and the right atrium
• Measurement of CVP is made with a water column or preferably, an electronic transducer.

• Sites of central venous cannulation - internal jugular, external jugular, subclavian, basilic and femoral veins.
• Complications:
• Infection
• Air or thrombus embolism
• Arrythymias – indicating catheter tip is at right atrium.

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• Haematoma
• Pneumothorax, haemothorax
• Cardiac perforation
• Injury to surrounding nerves and arteries.

Pulmonary monitors.

• Pulse oximetry.
• Pulse oximeters are mandatory monitors for any anaesthetic procedure.
• It combines the principle of oximetry and plethsmography to non invasively measure oxygen saturation in arterial blood .
• It utilizes the differences in light absorption spectra of oxyhaemoglobin and deoxyhaemoglobin to determine their relative

• Proportion and hence the oxygen saturation.
• Pulse oximeter provide an indication of tissue perfusion and measure heart rate
• Indications
• Routine perioperative use
• Patients with increased risk of hypoxia – pregnancy, obesity
• Used in critically ill patients.

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• Checking efficacy of cardiopulmonary resuscitation

Factors that may underestimate pulse oximetry falsely

• Methaemoglobin
• Methylene blue
• Overestimating pulse oximetry:
• Carboxyhamogloblin.

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• Other causes of artefact include – excessive ambient light, hypotension, cold extremities, motion, hypothermia, low perfusion , anaemia etc.

Capnography

• Determination of end tidal CO2 concentration to confirm adequate ventilation is useful during all anaesthetic procedure especially general anaesthesia.
• It is a valuable monitor of the pulmonary, cardiovascular and anaesthetic breathing systems.
• It relies on the principle of absorption of infra red light by CO2.

• There are two types of analyzers – the mainstream and the side stream capnographs
• Uses of capnograph
• As a respiratory monitor- hypoventilation and hyperventilation
• As a metabolic monitor- malignant hyperthermia in which there is high end tidal CO2.

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• Capnograph rapidly and reliably detect oesophageal intubation. This is a common cause of anaesthetic catastrophe.
• Sudden cessation of CO2 during expiratory phase may indicate a circuit disconnection.
• Curare cleft- when using muscle relaxants.

Conclusion.

• Monitoring is very important in anaesthesia to ensure patient safety. Its use cannot be overemphasized.