2Why is assessing acid-base status important? Assessing the tachypnic animalLow oxygenation vs. blowing off CO2Assessing vomiting animalsMetabolic alkalosis with high outflow obstruction vs. metabolic acidosisDiabetic animalsKetoacidosis vs. ketosis alone
3Why is assessing acid-base status important? Renal failure animalsDo you need to supplement NaHCO3?Dyspnic animalsAll though arterial blood gas is best we can make some assessments using venous samples.
23Respiratory alkalosis Acid-Base PhysiologyRespiratory alkalosisDefined as a ↓CO2
24Respiratory Alkalosis CausesHypoxemiaIn some cases of respiratory disease oxygen can not get into blood stream but CO2 can get out.In these cases the body increases respiratory rate in response to hypoxemia which PCO2
25Respiratory Alkalosis CausesHypoxemia ExamplesMild to moderate pneumonia or CHFPTEInterstitial fibrosis
26Respiratory Alkalosis CausesStimulation of respiratory centerIntracranial diseaseHepatic encephalopathyGram negative sepsisRapid correction of metabolic acidosisOver compensationLast hrs
27Respiratory Alkalosis What effect does ↓CO2 have on the body?H+ + HCO3 H2CO3 H20 + CO2
28Respiratory Alkalosis ↓CO2 Causes a shift to the rightH+ + HCO3 H2CO3 H20 + ↓CO2Leading to ↓H+ & ↓HCO3 & ↑pH
29Respiratory Alkalosis See both an acuteand a chronicMetaboliccompensatoryresponse.
30Respiratory Alkalosis Acute compensationUse nonbicarbonated buffersCl/HCO3 exchange in cell membranesSimilar for both dogs and catsOccurs with in 15 minutes
31Respiratory Alkalosis Chronic compensationDogsRenal adaptationIncrease H+ retentionIncrease HCO3 excretionTakes 2-5 days to reach steady stateMaybe a similar mechanism in cats
32Compensated Respiratory Alkalosis Unfortunately this is not enough to override the ↓CO2
46Acid Base Analysis Is the patient acidic or alkalotic? Does the PCO2 or HCO3 match the pH?If PCO2 matches then it is respiratory, if HCO3 matches it is metabolic.The other value measures compensation.
55Maggie 10-year-old F/S Lab How do her clinical signs match up?Tachycardia, pale gums, poor pulsesTachypneaVenous blood gas Arterial blood gaspH – pH – 7.28PCO PCO2 – 10.1HCO HCO3 – 5.0PO2 – 189Does she need oxygen?
74Metabolic Acidosis Detrimental effects of Acidosis Decreased myocardial contractility when pH < 7.2Predispose heart to VPCsPeripheral insulin resistanceObtunded state or coma
75Metabolic Acidosis Treatment IV fluids to address dehydration or hypovolemia –Use pH balanced fluids such as LRS or Norm R
76Metabolic Acidosis Treatment Blood transfusions for anemia
77Metabolic Acidosis Treatment NaHCO3 supplementUse only when dehydration, hypovolemia, and anemia have been addressedpH is < 7.2Do not use when body has not shown compensation with a low PCO2
78Metabolic Acidosis Treatment NaHCO3 supplement.3 x [Wt(Kg)] x BEBE = Normal HCO3 (24) – HCO3 of patientIf pH < 7.1 then bolus 25%Give 50% over 12 hrs.
79Metabolic Acidosis Treatment NaHCO3 supplementMonitor acid-base status q 6 hrsStop supplement when pH is 7.2Recheck acid-base status 6 hrs later to make sure further supplementation is not needed.
80Metabolic Alkalosis Renal physiology Normally expect the kidney to excrete HCO3 and conserve H+Normal human patients given 1,000 mEq NaHCO3 /day for 2 weeks excreted virtually all of the HCO3Metabolic alkalosis has significantly less HCO3 load- Burton David Rose, 1994
83Metabolic Alkalosis Renal physiology Hypokalemia Increased H+/K+ exchange leading to influx of H+ into cells. This leads to H+ secretion in renal tubules.Severe hypokalemia causes renal excretion of Cl-
84Metabolic Alkalosis Treatment IV fluids - .9% NaCl K+ supplementation Replenishes Cl-Acidic fluidWith out Cl- you can not encourage H+ retention and HCO3 excretionK+ supplementationCorrect primary problem
85Respiratory Acidosis and Alkalosis TreatmentNo specific treatment necessaryTherapy directed towards the primary problem.