Page 116 - Basic Monitoring in Canine and Feline Emergency Patients

into account, increases in PaCO will decrease the Silverstein, D.C., Hopper, K. (eds) (2012) Small Animal
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ratio independently of actual diffusion functional- Critical Care Medicine, 2nd edn. Elsevier, St.
VetBooks.ir ity of the lung. This is because if you ventilate less acid–base analysis, ventilation, and oxygenation
Louis, Missouri, USA. Excellent concise reviews of
(i.e. have a higher PaCO ), you will move less air
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assessments.
in and out of the alveoli and less oxygen diffuses
into the blood, resulting in a lower PaO This in West, J.B., Luks, A.M. (2016) West’s Respiratory
Physiology: The Essentials, 10th edn. Wolters Kluwer,
2.
turn lowers the P/F ratio. Therefore, it is difficult Philadelphia, Pennsylvania, USA. An excellent review
to say if there has been a true decline in lung func- of the physiology behind ventilation and oxygenation
tion in the first 12 hours. An A–a gradient could be disorders.
performed to more accurately assess this as com-
pared to values at presentation, but would require
taking the patient off oxygen supplementation to
assess the blood gas at room air. Bibliography
5. Moving from 12 to 24 hours, despite the PaCO Baird, G. (2013) Preanalytical considerations in blood
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and FiO remaining fairly static, the PaO declines gas analysis. Biochemia Medica 23, 19–27.
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to 72 mmHg and therefore the P/F ratio also Bateman, S. (2008) Making sense of blood gas results.
declines to 180, indicating a significant loss of pul- Veterinary Clinics of North America Small Animal
monary function. 38, 543–557.
6. At 36 hours, the PaCO ‘normalizes,’ which Beaulieu, M., Lapointe, Y., Vinet, B. (1999) Stability of
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is particularly concerning in an animal with pro- PO , PCO , and pH in fresh blood samples stored in
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2
longed increased respiratory effort as it most likely a plastic syringe with low heparin in relation to vari-
ous blood-gas and hematological parameters.
indicates the patient is fatiguing and is close to Clinical Biochemistry 32, 101–107.
respiratory arrest. At this time point, this patient Bergman, L., Lundbye, J. (2015) Acid-base optimization
meets several criteria for requiring mechanical ven- during hypothermia. Best Practice & Research
tilation, including an inability to maintain a PaO Clinical Anaesthesiology 29, 465–470.
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>60 despite maximal O supplementation and Boron, W. (2009) Acid–base physiology. In: Boron, W.F.,
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excessive work of breathing leading to respiratory Boulpaep, E.L. (eds) Medical Physiology, 2nd edn.
fatigue. Hence, the dog was intubated and hand Saunders Elsevier, Philadelphia, Pennsylvania, USA,
ventilated via an anesthesia reservoir bag on 100% pp. 652–671.
FiO . The P/F ratio improved to 192, similar to Briganti, A., Portela, D.A., Grasso, S., et al. (2015)
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the previous 24-hour value (180), implying the Accuracy of different oxygenation indices in estimat-
ing intrapulmonary shunting at increasing infusion
decrease in P/F ratio at 36 hours was likely due rates of dobutamine in horses under general anaes-
to respiratory fatigue and relative hypoventilation thesia. The Veterinary Journal 204, 351–356.
rather than a true change in pulmonary function. Constable, P. (2014) Acid-base assessment: When and
At this point, after discussing the necessity of how to apply the Henderson-Hasselbalch equation
initiating true mechanical ventilation with the and strong ion difference theory. Veterinary Clinics
owner, humane euthanasia was elected. Necropsy of North America Food Animal 30, 295–316.
confirmed severe disseminated blastomycosis with DiBartola, S.P. (2012a) Introduction to acid-base disor-
lesions in all lung lobes, both eyes, multiple lymph ders. In: Dibartola, S.P. (ed.) Fluid, Electrolyte and
nodes, skin, and bone. Acid-Base Disorders in Small Animal Practice, 4th
edn. Elsevier, St. Louis, Missouri, USA, pp. 231–252.
DiBartola, S.P. (2012b) Metabolic acid-base disorders.
Further Reading In: Dibartola, S.P. (ed.), Fluid, Electrolyte and Acid-
Base Disorders in Small Animal Practice, 4th edn.
Burkitt Creedon, J., Davis, H. (2012) Advanced Monitoring Elsevier, St. Louis, Missouri, USA, pp. 253–285.
and Procedures for Small Animal Emergency and Gonzalez, A., Waddell, L. (2016). Blood gas analyzers.
Critical Care. Wiley-Blackwell, Ames, Iowa, USA. A Topics in Companion Animal Medicine 31, 27–34.
good resource with images on how to perform tech- Haskins, S.C. (1977) Sampling and storage of blood for
niques including arterial blood sampling and arterial pH and blood gas analysis. Journal of the American
catheter placement. Veterinary Medical Association 170, 429–433.
Dibartola, S.P. (2012) Fluid, electrolyte and acid–base Hopper, K. (2015a) Traditional acid-base analysis. In:
disorders in small animal practice, 4th edn. Elsevier, Silverstein, D.C., Hopper, K. (eds) Small Animal
St. Louis, Missouri, USA. A comprehensive text review- Critical Care Medicine, 2nd edn. Elsevier, St. Louis,
ing acid–base physiology. Missouri, USA, pp. 289–295.

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