Page 583 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

570 FLUID THERAPY

hypoalbuminemia may benefit from its use. Preliminary PACKED CELL VOLUME AND TOTAL
studies in dogs show that human albumin administration PLASMA PROTEINS
in dogs will increase circulating albumin concentrations,
Measurements of PCV and total plasma proteins provide
total solids, and increase COP, although the effect on essential information. The PCV indicates oxygen-carrying
mortality remains unknown. 149 Current and future stud­
capacity of the blood because oxygenated hemoglobin is
ies will give us more information about the use of this
the source of oxygen content in arterial blood. Acute
product. Potential risks include potentially fatal acute or
changes in blood volume may not be reflected in the
delayed hypersensitivity reactions, volume overload, and PCV due to fluid shifts and potential for splenic contrac­
coagulopathy. 49,91 An increase in IgG against human albu­
tion in dogs. Based on recommendations from human lit­
min does occur in normal and critically ill dogs, with
erature, the hemoglobin should be maintained greater
potentially life-threatening reactions, and therefore than 8 g/dL (PCV >24%) to maintain oxygen delivery
repeated exposures are not recommended. 18,91 Canine without undue risk of excessive transfusions. 37,57 Blood
and feline albumin are now available for purchase,
or blood products should be considered when any animal
although there is limited data available regarding the use
is showing signs of decreased oxygen delivery (e.g.,
of these products at this time.
tachypnea, exercise intolerance, decreased mentation).
Patients with a chronic anemia may not require blood
products until the PCV is less than 15%.
MONITORING
Measurement of total plasma proteins provides addi­
Intensive care of the shock patient requires frequent reas­ tional valuable information. The color of the plasma
sessment of the animal. Several monitoring tools are use­ can help to identify hemolysis or icterus. The refractom­
ful, including physical findings (e.g., mucous membrane eter reading of the total plasma protein concentration
color, capillary refill time, pulse rate and quality, heart gives subjective information regarding COP in patients
rate, respiratory rate), arterial blood pressure (by invasive that have not received synthetic colloids. A decrease in
or noninvasive means), urine output, CVP, electrocardio­ the TP over time may indicate a loss or decreased produc­
gram, cardiac output, PCV, TP, blood glucose, tion of serum proteins. With rapid drops in TP, interstitial
electrolytes, acid-base balance, oxygenation, and ventila­ edema is likely to result, especially in the face of crystalloid
tion. The patient’s underlying disease process typically administration. The TP concentration should remain
dictates the importance and frequency of each monitor­ greater than 3.5 g/dL to ensure adequate intravascular
ing technique. Although oxygen transport variables oncotic pull. Colloid therapy should be strongly consid­
(e.g., cardiac output, content of oxygen in arterial and ered when the total plasma protein concentration is less
venous blood, oxygen consumption, and oxygen deliv­ than 3.5 g/dL. Colloid osmotic pressure can also be
ery) provide useful information, 95 most veterinary measured directly with an oncometer or colloid osmom­
practices do not have the capability to monitor oxygen eter. The COP of plasma in normal patients is approxi­
transport variables. There is increasing evidence to show mately 20 to 25 mm Hg, and values less than 16 mm
that even with advanced monitoring and normalization of Hg often are found in critically ill patients. Patients with
macrohemodynamic variables, some people, especially a COP less than 16 mm Hg will likely benefit from sup­
those with sepsis, may suffer from microcirculatory dys­ plemental colloid administration.
function and organ hypoperfusion. 36,42,65 However, CENTRAL VENOUS PRESSURE
the use of current monitoring techniques are useful for
assessment, prognosis, and treatment of unstable animals Measurement of CVP can provide valuable information
and are discussed below. about right ventricular function and intravascular volume
status and is relatively easy to monitor in most veterinary
PHYSICAL EXAMINATION practices. 154 Monitoring CVP involves placement of an
Physical examination findings are quite important in indwelling jugular catheter with the tip of the catheter
order to assess changes in cardiovascular status and in the thoracic cranial vena cava. If the animal has appro­
indices of perfusion. Although interpretation of these priate right-sided heart function, CVP provides informa­
findings is subjective, objective monitoring techniques tion on filling pressures of the heart (i.e., preload). The
can also be used to support clinical impressions. Periph­ CVP should range between 5 to 10 cmH 2 O in the shock
eral pulse rate, quality, and synchrony with the heartbeat; patient (2 to 5 cmH 2 O in cats), although normal CVP
respiratory rate, rhythm, and effort; mucous membrane values range from 0 to 10 cmH 2 O. Other determinants
color; and capillary refill time provide subjective informa­ of CVP also must be considered when interpreting values,
tion regarding the status of the cardiopulmonary including intrathoracic pressure and venous distensibility.
system. Additional physical findings of importance Appropriate fluid resuscitation should result in an
include the animal’s mentation and assessment of the jug­ increase in CVP. However, intravascular volume expan­
ular veins. sion is temporary following crystalloid resuscitation