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Fluid therapy
/content/chapter/10.22233/9781910443262.chap4
Fluid therapy
- Authors: Amanda Boag and Dez Hughes
- From: BSAVA Manual of Canine and Feline Emergency and Critical Care
- Item: Chapter 4, pp 29 - 43
- DOI: 10.22233/9781910443262.4
- Copyright: © 2018 British Small Animal Veterinary Association
- Publication Date: March 2018
Abstract
Fluid therapy is part of the treatment plan in most critically ill animals. The precise type, rate and total volume of fluid to be administered for optimal management of a patient can be difficult to determine. This chapter guides the reader in terms of decision-making and application of goal-directed fluid therapy.
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Figures
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4.1
Major fluid compartments of the body (% of bodyweight). © 2018 British Small Animal Veterinary Association
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4.1
Major fluid compartments of the body (% of bodyweight).
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4.2
(a) Normal fluid volumes and concentration. (b) Hypotonic fluid loss results in a reduced plasma volume and increased concentration of the extracellular fluid. An osmotic gradient exists, which favours the movement of water from the intracellular to the extracellular space. (c) Water moves out of the cells to buffer the reduction in extracellular fluid, thereby supporting the intravascular volume. The major extracellular cation is sodium (○) and the major intracellular cation is potassium (•). Small dots represent water molecules. © 2018 British Small Animal Veterinary Association
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4.2
(a) Normal fluid volumes and concentration. (b) Hypotonic fluid loss results in a reduced plasma volume and increased concentration of the extracellular fluid. An osmotic gradient exists, which favours the movement of water from the intracellular to the extracellular space. (c) Water moves out of the cells to buffer the reduction in extracellular fluid, thereby supporting the intravascular volume. The major extracellular cation is sodium (○) and the major intracellular cation is potassium (•). Small dots represent water molecules.
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4.3
(a) Normal fluid volumes and concentration. (b) Hypertonic fluid loss results in a reduced plasma volume and a reduced concentration of the extracellular fluid. An osmotic gradient exists, which favours the movement of water into cells from the extracellular space. (c) Water movement into the cells exacerbates the reduction in intravascular volume. The major extracellular cation is sodium (○) and the major intracellular cation is potassium (•). Small dots represent water molecules. © 2018 British Small Animal Veterinary Association
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4.3
(a) Normal fluid volumes and concentration. (b) Hypertonic fluid loss results in a reduced plasma volume and a reduced concentration of the extracellular fluid. An osmotic gradient exists, which favours the movement of water into cells from the extracellular space. (c) Water movement into the cells exacerbates the reduction in intravascular volume. The major extracellular cation is sodium (○) and the major intracellular cation is potassium (•). Small dots represent water molecules.
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4.5
Pulse profiles from direct arterial pressure measurement. Assessing the height and width of the pulse together allows an estimation of pulse volume. (Note that in practice it is not always possible to palpate the plateau in the normal pulse profile; see Chapter 3.) © 2018 British Small Animal Veterinary Association
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4.5
Pulse profiles from direct arterial pressure measurement. Assessing the height and width of the pulse together allows an estimation of pulse volume. (Note that in practice it is not always possible to palpate the plateau in the normal pulse profile; see Chapter 3.)
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4.6
Guidelines for the clinical assessment of dehydration. © 2018 British Small Animal Veterinary Association
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4.6
Guidelines for the clinical assessment of dehydration.
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4.8
(a) Hypovolaemic shock. Large open dots represent albumin molecules and small dots represent small solutes. (b) Intravascular expansion during infusion of isotonic crystalloid. There is no concentration gradient change between the intracellular and extracellular space. (c) Intravascular expansion with isotonic crystalloid. Intravascular crystalloid equilibrates with the interstitial space and intravascular volume falls compared with the initial volume of expansion. (d) Intravascular expansion following hypertonic crystalloid results in a large increase in intravascular sodium concentration and a large osmotic gradient for water to flow into the vasculature. (e) Intravascular expansion following hypertonic crystalloid. Water passes into the intravascular space from the interstitial and intracellular compartments, producing a rapid, but transient, expansion of intravascular volume. PMN = polymorphonuclear leucocyte; RBC = red blood cell. The major extracellular cation is sodium (○) and the major intracellular cation is potassium (•). Small dots represent water molecules. © 2018 British Small Animal Veterinary Association
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4.8
(a) Hypovolaemic shock. Large open dots represent albumin molecules and small dots represent small solutes. (b) Intravascular expansion during infusion of isotonic crystalloid. There is no concentration gradient change between the intracellular and extracellular space. (c) Intravascular expansion with isotonic crystalloid. Intravascular crystalloid equilibrates with the interstitial space and intravascular volume falls compared with the initial volume of expansion. (d) Intravascular expansion following hypertonic crystalloid results in a large increase in intravascular sodium concentration and a large osmotic gradient for water to flow into the vasculature. (e) Intravascular expansion following hypertonic crystalloid. Water passes into the intravascular space from the interstitial and intracellular compartments, producing a rapid, but transient, expansion of intravascular volume. PMN = polymorphonuclear leucocyte; RBC = red blood cell. The major extracellular cation is sodium (○) and the major intracellular cation is potassium (•). Small dots represent water molecules.
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4.10
A water manometer for measurement of central venous pressure (CVP). Tube A is attached to the central line in the patient and the patient is positioned in right lateral recumbency. For an accurate reading it is important that point X is at approximately the same height as the patient’s right atrium. The three-way stopcock is closed to the patient. Tube B is filled with saline from a syringe attached to tube C, until the height of the water column is at least 20 cm. The three-way stopcock is then opened so that it allows communication between tubes A and B (i.e. off to tube C). The saline in tube B will run into the patient until the water column reaches a height that is in equilibrium with the patient’s CVP. This height is read as the CVP in cmH2O. Repeat measurements can be taken as often as necessary but for reliable interpretation the patient’s position must be consistent. Note: for the purposes of this illustration, a coloured dye was added to the saline in this manometer. © 2018 British Small Animal Veterinary Association
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4.10
A water manometer for measurement of central venous pressure (CVP). Tube A is attached to the central line in the patient and the patient is positioned in right lateral recumbency. For an accurate reading it is important that point X is at approximately the same height as the patient’s right atrium. The three-way stopcock is closed to the patient. Tube B is filled with saline from a syringe attached to tube C, until the height of the water column is at least 20 cm. The three-way stopcock is then opened so that it allows communication between tubes A and B (i.e. off to tube C). The saline in tube B will run into the patient until the water column reaches a height that is in equilibrium with the patient’s CVP. This height is read as the CVP in cmH2O. Repeat measurements can be taken as often as necessary but for reliable interpretation the patient’s position must be consistent. Note: for the purposes of this illustration, a coloured dye was added to the saline in this manometer.