Page 77 - Cote clinical veterinary advisor dogs and cats 4th

Acidosis 15.e3

suspected from the initial database (e.g. > 60 mm Hg (SpO 2 = 90%) in respiratory disturbance because a patient has a normal
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ethylene glycol testing, imaging of kidneys). acidosis, oxygen should be administered to blood pH; HCO 3 , PCO 2 , and electrolytes
VetBooks.ir imaging) and neurologic evaluation in cases no higher). Cl -rich fluids (e.g., 0.9% NaCl) • Mixed acid-base disorders should be sus- Diseases and Disorders
• Thoracic imaging (radiographs ± advanced
raise it to approximately 60 mm Hg (but
must also be evaluated.
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assist compensation in chronic respiratory
pected if
of respiratory acidosis
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• The concentrations of some electrolytes (e.g.,
rebound metabolic alkalosis after the respira-
ionized calcium) can vary depending on acidosis by preventing the development of ○ PCO 2 and HCO 3 change in opposite
directions
blood pH and may require frequent reas- tory problem has been treated and PO 2 has ○ pH is normal with an abnormal PCO 2
sessment while the pH is being corrected. normalized. and/or HCO 3 −
○ pH changes in a direction opposite to
TREATMENT Chronic Treatment • One type of mixed acid-base disorder,
what is expected for the underlying disease
TREATMENT OVERVIEW Oral supplementation of NaHCO 3 (0.5-1 mEq/ the combination of metabolic acidosis
The primary aim is to correct the underlying kg/d) may be helpful in chronic metabolic with respiratory alkalosis (neutralizing pH
cause of the acid-base derangement. Treating acidosis (as in chronic kidney disease). Dietary abnormalities), commonly occurs in condi-
the inciting cause should return the blood pH chloride supplementation (e.g., KCl) assists tions such as septic shock, GDV, liver disease,
to close to normal. Usually correct the most metabolic compensation in cases of chronic and during cardiopulmonary resuscitation.
life-threatening, most treatable condition first. respiratory acidosis. • Another type of mixed acid-base disorder,
For example, acid-base abnormalities in dogs the combination of respiratory acidosis and
with gastric dilation/volvulus (GDV) often Drug Interactions metabolic alkalosis, may occur in cases of
respond to stomach decompression and aggres- NaHCO 3 is best administered as a separate GDV or in patients with pulmonary edema
sive vascular volume support with parenteral infusion and should not be given in dextrose- or that have been treated with diuretics.
fluids. In treatment of diabetic ketoacidosis alcohol-containing fluids. • The combination of respiratory acidosis
(DKA), fluid resuscitation, electrolyte supple- together with metabolic acidosis usually
mentation, and correction of hyperglycemia Possible Complications occurs in patients with acute severe respira-
result in normalization of the metabolic acidosis, • Rapid administration of NaHCO 3 can cause tory disease that also have lactic acidosis due
often without sodium bicarbonate supplementa- hypernatremia and thrombophlebitis (see to hypoxemia, shock, or low cardiac output.
tion. Blood gas–derived acid-base parameters guidelines for administration above). • Hyperchloremic and high–anion gap acidoses
are a good indication of the success of thera- • Treatment of mixed metabolic and respiratory together are usually seen in chronic kidney
peutic interventions (e.g., decreases in blood acidosis with NaHCO 3 should be avoided; disease, resolving ketoacidosis, or in patients
lactate after resuscitation) used for dealing with it can compound respiratory acidosis because with high–anion gap acidosis that develop
conditions such as GDV and DKA. CO 2 generated by NaHCO 3 is not adequately diarrhea or receive fluid therapy.
eliminated through exhalation. The clinician • Unlike dogs, cats with metabolic acidosis
Acute General Treatment should always consider whether a primary do not commonly generate compensatory
• Specific adjustment of blood pH by the respiratory disorder might be contributing respiratory alkalosis.
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administration of HCO 3 is rarely required to acidosis before deciding to administer
and should be considered only if blood pH NaHCO 3 . Prevention
is < 7.1. The aim of treatment is to raise pH Treat precipitating causes aggressively.
to 7.2 or until the physiologic consequences Recommended Monitoring
(e.g., hypotension, cardiac arrhythmias) Blood gas, serum electrolytes, and serum Technician Tips
resolve. Treatment is more important in albumin evaluation Changes in respiratory pattern or mentation
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animals with blood [HCO 3 ] < 5 mmol/L should prompt investigation of acid-base status
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because very small decreases in [HCO 3 ] at PROGNOSIS & OUTCOME in critically ill patients.
this level result in large decreases in pH. An
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approximate HCO 3 dose can be calculated Dependent on the reversibility of the underlying SUGGESTED READING
from the formula (base deficit may also be disease disorder and the trend of the acid-base Hopper K, et al: Incidence, nature, and etiology of
calculated by subtracting the patient’s variables over time metabolic acidosis in dogs and cats. J Vet Intern
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[HCO 3 ] from a normal [HCO 3 ] value): Med 26:1107-1114, 2012.
PEARLS & CONSIDERATIONS
mEq HCO 3 = 03× bodyweightkg) ADDITIONAL SUGGESTED
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(
.
× ( base deficit) Comments READINGS
• Almost all critically ill patients have an Funes S, et al: A quick reference on high anion gap
• Administer one-half of this dose intra- acid-base abnormality, but few require metabolic acidosis. Vet Clin North Am Small Anim
venously over 3-4 hours and recheck the treatment beyond correction/management Pract 47(2):205-207, 2017.
acid-base status. If the pH remains <7.2, of the underlying cause. Funes S, et al: A quick reference on hyperchloremic
the remaining half of the calculated dose can • Venous or arterial blood samples are adequate metabolic acidosis. Vet Clin North Am Small Anim
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be administered over 6-12 hours. Recheck for measuring pH, PCO 2, HCO 3 , and Pract 47(2):201-203, 2017.
venous blood gas every 4-6 hours to avoid electrolytes, but only arterial samples can be Johnson RA: A quick reference on respiratory acidosis.
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overcorrection of [HCO 3 ] or hypernatremia. used for PO 2 (PaO 2) measurement. Vet Clin North Am Small Anim Pract 47(2):185-
• The IV administration of NaHCO 3 is • Animals can have serious acid-base abnor- 189, 2017.
contraindicated in the treatment of respira- malities with normal blood pH (i.e., mixed AUTHOR: Kristin Welch, DVM, DACVECC
tory acidosis (primary lung/pleural/thoracic/ acid-base disorders). A common pitfall is to EDITOR: Benjamin M. Brainard, VMD, DACVAA,
neurologic disease). If arterial PO 2 is not fail to notice a severe, mixed acid-base DACVECC

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