Definition

• An elevation of carbon dioxide (CO2 ), usually in reference to the partial pressure of CO2 in arterial blood (PaCO2 ).
• The term hypercapnia is often used to describe elevation of end-expiratory partial pressure of CO2 (PE CO2 ) as this pressure is normally correlated to the PaCO2 .
• However, because horses can develop large discrepancies between their PaCO2 and P E CO 2 during anesthesia PE CO 2  should not be relied upon alone to accurately measure the magnitude of hypercapnia, and PaCO2  should be checked using blood gas analysis (see Measurement of carbon dioxide section below).

Measurement of carbon dioxide

Causes of hypercapnia

Hypoventilation

Physiologic effects of hypercapnia

Treatment of hypercapnia (in horses under general anesthesia)

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Brosnan R J, Steffey E P & Escobar A (2012) Effects of hypercapnic hyperpnea on recovery from isoflurane or sevoflurane anesthesia in horses. Vet Anaes Analg 39 (4), 335-344 PubMed.
• Khanna A K, McDonell W N, Dyson D H et al (2000) Cardiopulmonary effects of hypercapnia during controlled intermittent positive pressure ventilation in the horse. Can J Vet Res 59 (3), 213-221 PubMed.
• Taylor P M (1998) Effects of hypercapnia on endocrine and metabolic responses to anaesthesia in ponies. Res Vet Sci 65 (1), 41-46 PubMed.

Other sources of information

• Muir W W & Hubbell J A E (2009) Equine Anesthesia: Monitoring & Emergency Therapy. 2nd edn. Elsevier, USA.
• Lumb A B (2005) Nunns Applied Respiratory Physiology. 6th edn. Elsevier, USA.
• West J B (2005) Respiratory Physiology: The Essentials. 7th edn. Lippincott, Williams & Wilkins, UK.