Factors affecting the relationship between arterial and end-tidal carbon dioxide pressures in the anaesthetised horse.
Abstract: To assess the effects of the duration of anaesthesia, position of recumbency, mode of ventilation, anaesthetic drug protocol, patient age and type of surgical procedure on the usefulness of capnometry as a measure of the partial pressure of arterial carbon dioxide (P(a)co(2)) during general anaesthesia in horses. Methods: A prospective study compared the P(a)co(2) values with those of partial pressure of end-tidal carbon dioxide (ETco(2)) in horses anaesthetised for elective or emergency surgical procedures. The difference between P(a)co(2) and ETco(2) (P(a)co(2)- ETco(2)) and the physiological dead space to tidal volume ratio (V(D)/V(T)) were calculated. The effects of the study parameters on these variables was determined. Results: The agreement between P(a)co(2) and ETco(2) was poor. P(a)co(2)- ETco(2) and V(D)/V(T) during the first 60 min of anaesthesia was significantly less than after 60 min of anaesthesia. Mode of ventilation, position of recumbency, anaesthetic drug protocol, patient age and type of procedure did not have a significant affect on either value. Conclusions: P(a)co(2)- ETco(2) in anaesthetised horses can be large, making ETco(2) unreliable as a predictor of P(a)co(2) and for assessment of pulmonary ventilation. For anaesthesia lasting less than 60 min at least one blood gas analysis of an arterial blood sample is required to assess P(a)co(2)- ETco(2). Arterial blood gas analysis should be repeated after 60 min of general anaesthesia.
Publication Date: 2010-02-13 PubMed ID: 20148820DOI: 10.1111/j.1751-0813.2009.00535.xGoogle Scholar: Lookup
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Summary
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This research sought to determine how various factors influenced the relationship between arterial and end-tidal carbon dioxide pressures during general anaesthesia in horses and found that the conventional method of measuring end-tidal carbon dioxide (ETco2) was not a reliable predictor of arterial carbon dioxide pressure (Paco2).
Study Design and Methods
- The study was designed to look into factors like duration of anaesthesia, position of recumbency, ventilation mode, anesthetic protocol, patient’s age, and type of procedure to see if they impacted the use of capnometry, a method used to measure Paco2.
- This prospective study compared Paco2 values with the partial pressure of end-tidal carbon dioxide (ETco2) in anaesthetised horses undergoing either elective or emergency surgical procedures.
- Difference between Paco2 and ETco2 (Paco2 – ETco2) as well as physiological dead space to tidal volume ratio (V(D)/V(T)) were calculated and the effects of chosen parameters on these variables were examined.
Results of the Study
- The results showed poor agreement between Paco2 and ETco2, revealing that ETco2 is an unreliable method for predicting Paco2 and assessing pulmonary ventilation.
- It was also found that the ratio of Paco2 – ETco2 and V(D)/V(T) was significantly less during the first 60 minutes of anaesthesia as compared to beyond 60 minutes.
- There was no significant effect on these values from factors such as mode of ventilation, position of recumbency, anaesthetic drug protocol, patient age, and type of procedure.
Study Conclusions
- The study concluded that in anaesthetised horses, the difference between Paco2 and ETco2 can be large which renders ETco2 to be unreliable as a measure to determine Paco2 or to assess pulmonary ventilation.
- Therefore, upon anaesthetising horses, at least one arterial blood gas analysis of arterial blood sample should be carried out to evaluate Paco2 – ETco2 when the anaesthesia is expected to last less than 60 minutes.
- Furthermore, an arterial blood gas analysis needs to be repeated after 60 minutes of general anaesthesia to assess the Paco2.
Cite This Article
APA
Rainger JE, Dart CM, Perkins NR.
(2010).
Factors affecting the relationship between arterial and end-tidal carbon dioxide pressures in the anaesthetised horse.
Aust Vet J, 88(1-2), 13-19.
https://doi.org/10.1111/j.1751-0813.2009.00535.x Publication
Researcher Affiliations
- University Veterinary Teaching Hospital Camden, University of Sydney, Camden, New South Wales 2570, Australia. j.rainger@vetp.usyd.edu.au
MeSH Terms
- Anesthesia, General / veterinary
- Animals
- Blood Gas Analysis / veterinary
- Carbon Dioxide / analysis
- Carbon Dioxide / blood
- Horses / physiology
- Intermittent Positive-Pressure Ventilation / veterinary
- Partial Pressure
- Posture / physiology
- Prospective Studies
- Respiratory Dead Space / physiology
- Tidal Volume
- Time Factors
Citations
This article has been cited 2 times.- Stefanik E, Drewnowska O, Lisowska B, Turek B. Causes, Effects and Methods of Monitoring Gas Exchange Disturbances during Equine General Anaesthesia.. Animals (Basel) 2021 Jul 9;11(7).
- Mosing M, Böhm SH, Rasis A, Hoosgood G, Auer U, Tusman G, Bettschart-Wolfensberger R, Schramel JP. Physiologic Factors Influencing the Arterial-To-End-Tidal CO(2) Difference and the Alveolar Dead Space Fraction in Spontaneously Breathing Anesthetised Horses.. Front Vet Sci 2018;5:58.
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