Anaesthesia Monitoring - MIMV 3rd Year

Questions and Answers

Which condition can lead to an erroneously high reading of SpO2?

Hypovolaemia

Bradyarrhythmias

Carboxyhaemoglobin (correct)

Hypothermia

What can cause hypoxaemia due to impaired oxygen transfer?

Hypotension

External light

Movement

Ventilation/Perfusion (V/Q) mismatch (correct)

Which of the following factors does NOT affect signal detection?

Skin pigment

Probe positioning

Hypotension

Intra-cardiac shunt (correct)

What is a primary method used for monitoring inhalant agents?

Infrared absorption spectroscopy Signup and view all the answers

Which monitoring technique is commonly used to estimate core temperature?

Deep oesophagus thermometer probe Signup and view all the answers

What is considered a normal SpO2 level?

95 – 100% Signup and view all the answers

What PaO2 level corresponds to an SpO2 drop indicating a potential problem?

Below 90 mmHg Signup and view all the answers

Which mechanism is used in pulse oximetry to measure the degree of saturation?

Pulse photoplethysmography Signup and view all the answers

According to Beer-Lambert law, which of the following factors influences light absorbance?

Path length of light Signup and view all the answers

What light wavelength is predominantly absorbed by oxyhaemoglobin (OHb)?

940 nm Signup and view all the answers

What physiological change occurs immediately after acute hemorrhage?

Increased sympathetic tone Signup and view all the answers

Which type of pulse oximetry technology allows for the distinction of different haemoglobin species?

Masimo pulse oximetry technology Signup and view all the answers

What is the main purpose of measuring Mean Arterial Pressure (MAP)?

It represents the perfusion pressure of the organs. Signup and view all the answers

In pulse oximetry, what does the receiver measure?

The difference between emitted and received light Signup and view all the answers

Which hormone is primarily affected by low right atrial stretch during hypovolaemia?

Atrial Natriuretic Peptide (ANP) Signup and view all the answers

What primary interference affect most pulse oximeters?

Different algorithms for animals Signup and view all the answers

In response to acute hypotension, which of the following mechanisms is activated to restore blood volume?

Increased sympathetic tone Signup and view all the answers

What is the estimated time frame for the late response to acute hemorrhage?

Hours to days Signup and view all the answers

Which method is NOT a form of cardiovascular monitoring?

Liver function tests Signup and view all the answers

What change occurs in pulse pressure when there is an increase in Systolic Arterial Pressure (SAP)?

Increase in pulse pressure Signup and view all the answers

What is one of the key reasons for monitoring animals under anaesthesia?

To ensure an adequate anaesthesia depth Signup and view all the answers

Which of the following arteries is NOT typically palpated for assessing peripheral pulse in animals?

Radial artery Signup and view all the answers

Which of the following physiological aspects should be monitored during anaesthesia?

Respiratory system and temperature Signup and view all the answers

What does the presence of limb withdrawal reflexes indicate in rabbits under anaesthesia?

The anaesthesia depth is too light Signup and view all the answers

What autonomic response can nociception stimulate during anaesthesia?

Tachycardia and hypertension Signup and view all the answers

What eye movement is an indicator of anaesthesia depth in dogs and cats?

Central eye position Signup and view all the answers

Which reflex is crucial for assessing the depth of anaesthesia, especially in horses?

Perineal reflex Signup and view all the answers

What does electrocardiography primarily assess?

Electrical activity in terms of rate and rhythm Signup and view all the answers

How does the cardiovascular response to nociception differ in horses compared to other animals?

Horses typically show hypertension due to increased stroke volume Signup and view all the answers

What is the primary function of a sphygmomanometer?

To inflate the cuff to occlude blood flow Signup and view all the answers

Why are complete anaesthesia records important?

They are considered legal documents Signup and view all the answers

What is the consequence of using a cuff that is too tight during oscillometry?

It yields inaccurately high ABP measurements Signup and view all the answers

What does the maximal decrease in oscillation size during oscillometry indicate?

Diastolic arterial pressure Signup and view all the answers

In the placement of electrodes for electrocardiography, what shape should they form?

Triangular Signup and view all the answers

What is one limitation of plethysmography?

It only displays pulse strength as a waveform Signup and view all the answers

Which statement accurately describes the purpose of high definition oscillometry?

It has high sensitivity and displays pressure changes Signup and view all the answers

What does an inflated cuff during sphygmomanometry aim to accomplish initially?

Occlude blood flow to a limb Signup and view all the answers

What does a high Bispectral Index (BIS) value indicate?

Patient is awake and aware Signup and view all the answers

Which component is primarily associated with determining tissue oxygen delivery (DO2)?

Cardiac output Signup and view all the answers

In terms of parasympathetic tone activity (PTA), what does a predominant sympathetic tone reflect?

Lower heart rate variability Signup and view all the answers

What physiological change is observed in the electroencephalographic (EEG) patterns during anaesthesia?

Predominance of high amplitude and low frequency waves Signup and view all the answers

Which wave frequency is primarily characteristic of a conscious state in an EEG recording?

Alpha waves (α) Signup and view all the answers

Which factor can lead to an erroneously low reading of SpO2?

Anaemia Signup and view all the answers

What can cause hypoxaemia through a mismatch in ventilation and perfusion?

Intra-cardiac shunt Signup and view all the answers

Which of the following affects the accuracy of inhalant agent monitoring?

Methane interference Signup and view all the answers

What is a common method for monitoring core temperature during anesthesia?

Deep oesophagus thermometer probe Signup and view all the answers

Which condition may falsely elevate SpO2 readings in pulse oximetry?

Methaemoglobin presence Signup and view all the answers

What is a direct consequence of decreased Na+/K+ ATPase pump activity?

Cell edema and hyperkalaemia Signup and view all the answers

How is core temperature related to CNS activity during anaesthesia?

A decrease of 1°C reduces MAC by 5%. Signup and view all the answers

What effect does hypothermia have on cats during recovery from anaesthesia?

It can cause hyperthermia upon recovery. Signup and view all the answers

What is an important monitoring aspect when using neuromuscular blocking drugs?

Reducing muscle weakness while ensuring adequate paralysis. Signup and view all the answers

Which ECG finding indicates myocardial stress or dysfunction?

ST segment depression and T-wave inversion Signup and view all the answers

What is a primary reason for monitoring animals under anaesthesia?

To maintain physiological functions Signup and view all the answers

Which physiological aspect is NOT typically monitored during anaesthesia?

Mental status Signup and view all the answers

What reflex is crucial for assessing the depth of anaesthesia in horses?

Palpebral reflex Signup and view all the answers

What response can nociception trigger in the autonomic nervous system during anaesthesia?

Tachycardia and hypertension Signup and view all the answers

Which muscle reflex indicates light anaesthesia in rabbits?

Limb withdrawal reflex Signup and view all the answers

What is a crucial factor in achieving accurate arterial blood pressure measurements during invasive monitoring?

Zeroing the system to atmospheric pressure Signup and view all the answers

Which method is employed to check the autonomic response during anaesthesia?

Measuring heart rate and arterial blood pressure Signup and view all the answers

What is a common characteristic of brain activity during deep anaesthesia?

Reduced muscle tone Signup and view all the answers

Which of the following could lead to inaccurate arterial blood pressure readings?

Presence of air bubbles in the system Signup and view all the answers

What is the relationship between blood pressure and organ blood flow outside the range of 60 to 160 mmHg?

Organ blood flow becomes directly proportional to blood pressure Signup and view all the answers

What determines the adequacy of anaesthesia depth in dogs and cats?

Nystagmus and lacrimation Signup and view all the answers

What type of measuring system is preferred for invasive arterial blood pressure monitoring?

A saline-filled non-compliant system Signup and view all the answers

During arterial blood pressure monitoring, what important step must be performed to ensure reliability?

Leveling the system to the heart Signup and view all the answers

Study Notes

Introduction to Anaesthesia Monitoring

Essential for maintaining physiological functions during anaesthesia.
Adequate monitoring improves patient safety, crucial for high-risk species like horses (1 death per 100 cases).
Complete anaesthesia records serve as legal documentation.

Parameters to Monitor

Central nervous system (CNS)
Cardiovascular system (CVS)
Respiratory system
Body temperature
Neuromuscular and renal function
Metabolic and coagulation status

CNS Monitoring

Reflexes: Monitor palpebral, corneal, limb withdrawal, perineal, and righting reflexes to assess anaesthesia depth.
Eye movement: Positions indicate anaesthesia depth; particularly in dogs and cats.
Autonomic activity: Changes in heart rate and blood pressure reflect nociception, affecting sympathetic and vagal responses.

CVS Monitoring

Acute haemorrhage leads to decreased venous return, preload, and cardiac output, resulting in hypotension.
Initial response involves sympathetic activation, increasing heart rate and systemic vascular resistance while redirecting blood flow to vital organs.
Long-term restoration of blood volume through oral intake and renal functions occurs over hours to days.

Monitoring Techniques

Heart rate and rhythm assessed through electrocardiography.
Arterial blood pressure measurement techniques include manual sphygmomanometry, oscillometry, and high-definition oscillometry.
Mean arterial pressure (MAP) is crucial for assessing organ perfusion: MAP = (SAP + 2 * DAP) / 3.

Electrocardiography and Blood Pressure

Electrocardiography detects arrhythmias; requires at least three electrodes for correct placement.
Non-invasive techniques like pulsometry and oscillometry assess arterial blood pressure, with specific guidelines for cuff placement and size.
MAP as a primary value for organ perfusion over systolic and diastolic pressures.

Pulse Oximetry

Continuous, non-invasive measurement of hemoglobin oxygen saturation (SpO2) is crucial; normal ranges are 95-100%.
SpO2 can be a delayed indicator of hypoxaemia, which may not reflect immediate low PaO2 levels.

Respiratory System Monitoring

Pulse oximetry uses two mechanisms for oxygen saturation evaluation: pulse photoplethysmography and spectrophotometric oximetry.
Algorithm limitations include issues with hypotension, skin pigmentation, and external light interference.

Hypoxaemia Causes

Caused by factors like low inspired oxygen, hypoventilation, diffusion impairments, and V/Q mismatch.

Gas and Inhalant Agent Monitoring

Both inspired and expired gases must be monitored to prevent hypoxic mixtures.
Inhalant agent concentrations are measured via infrared absorption spectroscopy, mindful of interference from gases such as methane.

Mechanical Ventilation

Primarily achieved through positive pressure ventilation, which includes volume-controlled and pressure-controlled methods.

Temperature Monitoring

Core temperature measurement ideally occurs at the pulmonary artery or approximated through the deep oesophagus.

Introduction to Anaesthesia Monitoring

Monitoring is crucial to maintain physiological functions and ensure appropriate anaesthesia depth.
Enhances patient safety, especially notable in high-risk species like horses with a mortality rate of 1 in 100 cases.
Monitoring creates complete anaesthesia records for legal accountability, and also promotes personnel safety through proper analgesia.

Parameters to Monitor

Central Nervous System (CNS)
Cardiovascular System (CVS)
Respiratory System
Body Temperature
Neuromuscular Function
Renal Function
Metabolic Status (including haematological and biochemical variables)
Coagulation Status

CNS Monitoring Techniques

Reflex Assessment:
- Palpebral reflex evaluated bilaterally; corneal reflex persists until deep anaesthesia.
- Limb withdrawal reflex is crucial in rabbits, indicating anaesthesia depth.
Eye Movement and Position:
- Eye position changes can signal anaesthesia depth; notable in dogs, cats, and cattle.
- Horses may show slow palpebral contraction at deep anaesthesia, making globe position unreliable.
Autonomic Nervous System Activity:
- Heart rate and arterial blood pressure reflect nociception; can lead to tachycardia/hypertension or bradycardia/hypotension.
- Parasympathetic Tone Activity (PTA) indicates anaesthesia depth and analgesia-nociception balance.
Electroencephalography (EEG):
- Measures cortical brain electrical activity, indicating anaesthesia depth through different wave frequencies.
- The Bispectral Index (BIS) ranges from 0 (isoelectric activity) to 100 (awake), with ideal depth around 60%.

Cardiovascular System Monitoring

Goal to maintain tissue oxygen delivery (DO2) influenced by cardiac output, arterial oxygen content, and oxygen extraction.
Arterial Blood Pressure (ABP):
- Invasive monitoring requires catheterization; a non-compliant system connection to pressure transducers ensures accurate readings.
- Mean Arterial Pressure (MAP) is crucial for organ perfusion, needing maintenance within 60-160 mmHg to ensure effective blood flow.

Respiratory System Monitoring

Hypoxaemia Causes:
- Low inspired oxygen, hypoventilation, and V/Q mismatch are critical factors affecting oxygenation.
Gas Monitoring:
- Inspired and expired gases analyzed to identify hypoxia; inhalant agent monitoring essential for ensuring proper anaesthetic delivery.
- Special filters required to distinguish inhalants from methane interference, which could falsely elevate readings.

Temperature Monitoring

Core temperature should be managed to prevent CNS depression and maintain metabolic rates, primarily measured at the pulmonary artery or deep oesophagus.
Hypothermia can lead to cellular edema, acidosis, and decreased organ perfusion, influencing MAC (Minimum Alveolar Concentration).
Bradycardia and hypotension are common effects of temperature disruptions, affecting ECG readings, and increasing risks during recovery.

Neuromuscular Junction Monitoring

Important for patients administered neuromuscular blocking agents to assure adequate paralysis and normal recovery.
Proper electrode placement ensures accurate monitoring; incorrect placement may lead to erroneous interpretations of neuromuscular function.

Renal Function Monitoring

Maintain MAP during anaesthesia as hypotension can adversely affect renal function and overall patient safety.

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Description

This quiz focuses on the critical aspects of monitoring animals during anaesthesia, emphasizing the importance of maintaining physiological functions and adequate anaesthesia depth. It highlights the safety concerns related to anaesthesia in various species, particularly horses, dogs, and cats. Test your knowledge on best practices and statistics in veterinary anaesthesia monitoring.