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An Urban Experience
I. Rapid and real-time (NFS)
ii. Error-prone and requires significant ‘fiddling’
iii. Oxygenation issues are most likely during transitions, not mid-inhalant.
1. >30% inspired O2 precludes hypoxia in normal situations
2. Know normal (accuracy tied to steep portion of Oxyhemoglobin curve)
3. Perfusion linked to: cardiac performance, body temperature, positioning, pharmacology of drugs (vasoconstrictors)
4. Reptilia have a much lower oxygen consumption rate compared to mammals and birds
3. Ventilation (IPPV) isn’t always thought of as means of monitoring (rather seen under ‘support’). However, in reptiles, provision of ventilation commonly replaces the “wait and see” approach to respiratory monitoring frequently utilized in mammals.
I. Reptilian control of respiration likely involves CO2 and pH, not oxygen
1. Episodic breathing pattern – in bursts
2. Pulmonary perfusion is also intermittent, and patterns coordinate with respiratory pattern.
3. High oxygen may suppress ventilation in reptiles (various responses to CO2, as well...). Thus, recovery frequently involves IPPV with room air.
4. Amphibians utilize cutaneous respiration, and stop breathing when offered 100% (anesthetic gas provision/monitoring are challenging...)
II. Mammals & birds- primary pattern based upon central respiratory pattern generator w/peripheral chemoreceptors; oxygen serves as a back-up when low
1. Birds: cross-current exchange:
a. One of the few species that can have lower ETCO2 than PaCO2
b. Birds are very easy to over-ventilate (also- air sac fragility)
Cardiovascular: As with ventilation, Cardiovascular function is altered by anesthetic drugs, and so monitoring is a critical part of safe provision of anesthesia. Complex by nature, this system involves the entire body with regards to changes in vasomotor tone, as well as
the heart itself, and fluid and electrolyte status of the organism.
1. Rate and Rhythm may be measured simply (auscultation or amplification) or with monitors.
a. ECG shows electrical pattern through the heart. Each species has a common pattern that should be learned. This is real-time and simple to apply (NSF)
b. Electrical conduction through the heart does NOT necessarily result in mechanical activity (a normal ECG can be seen in a heart that is NOT beating).
c. Amplification can occur over a peripheral pulse, or over the heart directly (also consider use over eyes). This may provide subjective or objective information about quality of cardiac contraction
2. Blood pressure is established in most mammals, and increases in importance with increasing size of patient (as does reliability of measurement).
a. Non-crocodilian reptile hearts are three-chambered, so direction of blood-flow is labile, and shunting
is common. This can alter anesthetic (and other respiratory gas) uptake and elimination, and is not quantifiable, clinically.
b. Reptiles, birds and mammals have conserved mechanisms for altering blood pressure (cholinergic, adrenergic and baro-receptors). However, reptiles have a large variation in “normal” that are also influenced by: temperature, activity and state of arousal. (Chelonian normal MAP if 15-30 mmHg), while squamates may be allometrically scaled (larger snakes having higher BPs). In general, change from baseline is the suggested approach to blood pressure monitoring in reptiles.
c. Birds have higher blood pressure, lower heart rates, larger stroke volume and cardiac output than mammals.
d. Types of blood pressure monitoring:
I. Amplification alone: Non-quantifiable, but can give subjective information about the quality of cardiac performance. Placement of crystal is mild to moderately time-consuming (skill level related).
II. Amplification with cuff (doppler)- limited by size and shape of limbs
III. Oscillometric (cuff limitations, but without need for crystal). Rapid application, but intermittent readings
Iv. Arterial cannulation- in general, most time consuming. Most appropriate with advanced procedures or longer duration procedures (specialist level)
Metabolic: Body temperature is a critically important consideration in ectomorphs, altering anesthetic drug uptake and distribution, cardiac and respiratory functions, and markedly influencing recovery. It is also important in small mammals and birds, but to a less critical degree. Exotic patients should always be managed at their ideal physiologic temperature, and

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