Chemonges, Saul

University of Queensland eSpace

CONTEMPORARY DATA CAPTURE, ANAESTHESIA MONITORING AND POINT-OF-CARE 
TECHNOLOGY IN CRITICAL CARE RESEARCH SETTING FOR ANIMAL MODELS 
 
Saul Chemonges BVetMed, PGDipVetClinSt, MVSt, MANZCVS (Anaesthesia & Critical Care) 
Critical Care Research Group (CCRG), The Prince Charles Hospital, Brisbane, Queensland, Australia 
and 
The School of Medicine, The University of Queensland, Brisbane, Queensland, Australia. 
 
Introduction  
In critically ill patients, there is a depression of vital body systems notably the cardiovascular, respiratory and 
nervous systems.1 These systems have to be continually monitored to ensure adequate blood flow to the 
patients’ tissues, adequate oxygen concentration in the patient’s arterial blood, and adequate ventilation.1,2 
Often, in the critical patient, trends will mean more than individual measurements which underscores the 
importance of serial and chronic observations to give a more accurate indication of a patients physiological 
state.3  
As in humans, anaesthetised ill animals require meticulous critical care monitoring by trained and experienced 
professionals with the aid of contemporary patient monitoring devices in a well-equipped facility. Although 
animal patient monitors are designed to aid in determining priorities for monitoring, they are not meant to 
replace the veterinarian1,2 or technician.3 The measurements captured or derived from monitoring devices are a 
useful guide in showing trends happening within the fragile or disturbed physiology during experiments, even if 
they are not absolute values. 1 Furthermore, most, if not all the devices were developed for human medicine, so 
they may be presumed to be accurate in taking measurements, but may not necessarily represent values of the 
animal model. It is thus important to continually examine the animal by thorough basic examination and not by 
monitors alone.1,2  
Critical care clinicians, research scientists and technicians often work with experimental animal models that 
require rapid and continuous capture of vital patient information using medical devices to enable critical 
monitoring for a variety of procedures and studies. The diversity of animal patient monitoring devices in terms 
of model, brand, type and configuration poses challenges; therefore, it should not be assumed that existing 
human patient monitoring devices are standard for animals as significant variations exist.  
 
Technology for physiological and advanced haemodynamic monitoring at CCRG animal ICU  
The majority of human ICU patients are kept anaesthetised under total intravenous anaesthesia (TIVA), 
likewise, all ovine models of critical illness at CCRG are maintained by TIVA. Broadly, the ICU hardware is 
classified into advanced haemodynamic & intensive care patient monitors, and auxiliary life support equipment.  
 
Advanced haemodynamic & intensive care patient monitors 
Cardiovascular, temperature, oxygenation and respiration/ventilation physiological variables are continually 
monitored by the Marquette Solar 8000.  A pulmonary artery (PA) catheter is placed and coupled with a cardiac 
output monitor. Continuous cardiac output (CCO), mixed venous oxygen saturation (SvO2), end diastolic 
volume (EDV), systemic vascular resistance (SVR), body temperature (BT) and derived parameter monitoring 
commences using the Vigilance II monitor. Measured variables are recorded every five seconds using 
manufacturer provided software. Direct arterial blood pressure (ABP), central venous pressure (CVP), 
pulmonary artery pressure (PAP) measurements are transduced to the Marquette Solar 8000 monitor via 
respective attachments on the ports of the attachment from the PA catheter. The Marquette Solar 8000 monitor 
is also used for pulse oximetry (SPO2), ETCO2 recordings and electrocardiography (ECG).   
 
 Auxiliary life support equipment. 
This comprises mechanical ventilators, patient heating sources, medical imaging, oxygen delivery, patient 
warming and point-of-care laboratory equipment (oximetry, blood gases, blood coagulation machines 
centrifuges and refractometers). Mechanical ventilation is achieved by the use of the Galileo intensive care 
ventilator which has advanced ventilation modes and drug nebulising capabilities. Patient heating is achieved by 
the use of a circulating warm water mattress attached to either the warm water pump cooler/heater. 
 
General discussion on monitoring technology 
Veterinary aids or devices are required for capturing data and monitoring body systems. Monitoring the 
critically ill patient is important because drug effects are less predictable and often more pronounced in stressed 
animals.4-6 Constant monitoring is essential to maintain the necessary level of analgesia/anaesthesia, maintain a 
free airway, and to be able to recognise and deal with complications promptly. The data captured from the 
monitored parameters using medical devices and how frequently this is done depends on the changing needs of 
the individual patient in critical care. This information is necessary for the critical care veterinarian to make a 
final decision regarding treatment changes if necessary. It is very important for the critical care veterinarian to 
continually review and interpret the results of monitoring in particular to decide on the urgency of a particular 
scenario for each experimental subject. It is vital to know the limitations of the method used, and what the data 
means. The collection of information without knowing why or what to do with it once it has been availed is 
counterproductive. For this reason the role of the critical care veterinarian is vital for observing and testing the 
known subjective assessments such as monitoring of central nervous system functions.  
Patient monitoring devices 
The emergence of all-in-one or multi-parameter patient monitors such as Marquette Solar 8000 that our group 
uses to monitor experimental animal patients may not be a common place in many animal ICUs. These devices 
have modular capabilities of continuous measurement and the monitoring of ECG, SPO2, ABP, CVP, ETCO2 
and body temperature. The Marquette Solar 8000 monitor also has the capability of monitoring anaesthetic 
gases. In the veterinary market, multi-parameter patient monitors come in various makes and models with 
varying capabilities such as Surgivet™, Mindray™, Bionet™, VetSpecs™, Pace Tech™, Cardell™, 
Datascope™ and Digicare™. We discuss the relevance of the individual modules below. 
The ECG detects the electrical activity of the heart but not the cardiac function.1 This is important for 
monitoring cardiac rate and rhythm, the presence or absence of effective coronary blood flow, disturbances in 
potassium ion concentration and drug intoxication.7 In the event of cardiac arrest, asystole and fibrillation can be 
differentiated. An ECG however does not give any indication of cardiac output and whether problems arising 
originate within the heart or are due to extrinsic factors.4,7  
Adequate blood pressure is necessary for tissue perfusion which is determined by cardiac output. ABP is often 
monitored in the critical patient to provide information on cardiac output.3 There are two types of blood pressure 
measurements: invasive or direct blood pressure measurement (IBPM) and non-invasive or indirect blood 
pressure measurement (NIBPM).The accuracy of any device used to measure blood pressure is an important 
consideration when selecting monitoring equipment, the ANSI/AAMI SP10 standard has been widely cited in 
this respect in recent veterinary publications.8 A sphygmomanometer can be used for indirect manometry of 
arterial pressure by employing an inflatable cuff and a stethoscope. It is commonly used in conjunction with a 
Doppler flow probe. It is important for measuring systolic pressure and to a lesser extent diastolic pressure in 
animals.1,9 This simple method provides good comparative information of blood pressure. Commonly used 
oscillometric non-invasive blood pressure monitors include Cardell Veterinary Monitor 9401 BP (Sharn 
Veterinary Inc, Tampa, FL); and Datascope Passport, (Datascope Corp, Paramus, NJ).10 The Surgivet V60046 is 
also commonly used in non-invasive blood pressure measurement.11 The Marquette Solar 8000 monitor also has 
NIBPM capabilities. An example of ultrasonic non-invasive blood pressure monitor is the ultrasonic Doppler 
flow detector, Model 811-B (Parks Medical Electronics Inc, Aloha, OR).10  
We routinely measure and monitor direct ABP and CVP with the Marquette Solar 8000 monitor. CVP  
monitoring is useful in measurement of hydrostatic pressure in the intrathoracic vena cava which is a useful 
guide not only in fluid replacement therapy but also to the ability of the right heart to handle the venous return.3 
Direct blood pressure measurement is not without problems; clotting in the catheter can occur, time is required 
to instrument the patient, the electronic equipment is expensive and potentially fatal complications can occur.12  
Increasingly, echocardiography is now considered an indispensable tool for diagnosis and haemodynamic 
monitoring in critically ill patients.13 We also routinely monitor CCO, but some disadvantages have been 
reported.14 
A pulse oximeter is a device that measures the saturation of oxyhaemoglobin in blood and is one of the most 
utilised monitors in the critically ill or emergent patient.3 It also shows a pulse waveform, which, while not 
giving an actual measurement of the pulse pressure, does give the rate and some indication of its character.1,4,5 
Accuracy and failure rates (failure to produce a reading) vary widely from model to model and from species to 
species.15 We get reasonably consistent oximetry signals in sheep by clamping the probe on the nasal pore or the 
lip. There are studies indicating that third generation pulse oximeters may not perform better than older 
instruments.16 
A capnograph analyses end-tidal carbon dioxide (ETCO2) during breathing and gives valuable information on 
the ventilatory status of the patient.3-6,17 The ETCO2 is a close approximation to arterial pCO2 and therefore 
gives an indication of hypo- or hypercapnia. Capnography failures are usually associating with excessive 
fogging or fluid build-up within the breathing apparatus. 
A stethoscope is an important aid in monitoring heart rate and can provide more than just heart rate.3  
Ventilation meters are used to measure respiratory tidal volume. There are various types; however, the most 
useful ones are Wright's Respirometer and the Dräger Volumeter.4 The associated problems are that they do not 
reveal the adequacy of distribution or of gaseous exchange in the lungs. Ventilation meters may add resistance 
to the airway and are only useful if one is not sure of the adequacy of the tidal volume after reversal of a muscle 
relaxant.1,4 Our patients are ventilated with the Galileo ventilator which has inbuilt ventilation meters and 
provides real time parameters for ventilation. 
Performing regular patient-side monitoring tests of certain parameters is important critical care. The regular 
monitoring of PCV, refractometric TP, blood glucose, electrolytes, venous or arterial blood gas, clotting 
parameters and blood smear examination should be considered. Full blood panels for complete blood count 
(CBC) and biochemistry are required periodically as a benchmark. The analysis of blood gases (PaO2, PaCO2, 
and pH) is the most effective way of measuring respiratory efficiency. Handheld devices and standard chemistry 
analysers are available for use in blood gas analysis.18 The common handheld devices are the i-Stat19 and the 
lactate meter.20 Differences exist between different machines.21,22 There are various point-of-care or desktop 
blood analysers in use in emergency and critical care establishments. We use the bench top ABL800 FLEX 
blood gas analyser, which can measure up to 18 STAT parameters on the same blood sample including 
creatinine. Our group utilises the rotating pin thromboelastometry (ROTEM) to determine if bleeding is caused 
by haemorrhage or clotting factor deficiency, and the Multiplate platelet function analyser which uses 
impedance aggregometry to assess platelet function in whole blood. 
A thermometer is used for measuring body temperature. Either rectal, oesophageal or core temperature may be 
monitored. There are also thermometers that are designed to detect body temperate in the external ear canal.23,24 
For our animal models, continuous core temperature is monitored in real-time with the aid of the PA catheter 
and CCO monitor. 
Mechanical ventilators 
Mechanical ventilators are important aids of respiration during life support for example in the management of 
respiratory failure, cardiac arrest, neurologic impairment, and nonresponsive hypotension25 to perform some or 
all of the work of breathing.26 Ventilators are widely used in veterinary medicine to improve the survival of 
animals with hypoxaemic and hypercapnic respiratory failure.27 The indications, goals, and prognosis of 
mechanical ventilation in animals have been covered in detail elsewhere.26 The ventilator also acts as a 
ventilation meter, respiratory rate monitor and apnoea alarm.  
Conclusion 
Monitoring of critically ill patients is essential; failure to detect warning signs of impending disaster results in a 
dead or impaired patient. Even if the patient survives, there might be considerable visceral organ damage. 
Monitoring devices can be misleading if they do not function correctly or are not properly set up. Artefacts do 
occur; it is therefore important for the veterinarian to physically check the patient first, before assuming the 
instrument is faulty. There is no device that replaces the veterinarian in monitoring an animal patient. Our 
monitoring practices probably represent an advanced and appropriate technology available during the provision 
of total intravenous anaesthesia in ovine models. 
Acknowledgments 
Indebted to contributions from the Critical Care Research Group (CCRG) animal laboratory team at The Prince 
Charles Hospital specifically: Dunster KR, Diab S, Passmore M, McDonald C, Simonova G, Foley S, Hayes R, 
Platts D, Tung J-P, Shekar K, Fung Y, and Fraser JF. 
 
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Contemporary data capture, anaesthesia monitoring and point-of-care technology in critical care research settings for animal models

http://espace.library.uq.edu.au/view/UQ:328111/CDCAMP_Saul_Chemonges.pdf

Contemporary data capture, anaesthesia monitoring and point-of-care technology in critical care research settings for animal models

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