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25 Cards in this Set
- Front
- Back
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Normal VT
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10-20 mL/kg in most domestic species
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Alveolar Ventilation ( VA) =
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RR x (VT– VD)
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Hypercapnia: PaCO2 > 45 mmHg
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§ From 45 - ˜100 mmHg it is a respiratory stimulant, § CNS stimulant and vasodilator § In excess of 100mmHg it is an anesthetic & CNS depressant
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PAO2 =
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[(Patm-PH20) x FiO2] - PaCO2 /0.8
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“Cyanosis” requires >
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5gm/dL of deoxygenated Hb
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CaO2=
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(Hg x %Sat x 1.34)+ (0.003 x PaO2)
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Apnea Monitor
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detects air flow, rate only, alarms w/apnea §continuous, auditory signal
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Ventilometry
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•Measures the volume of a breath (tidal volume) §simple turbine-propelled vWright’s respirometer §computerized, flow-generated
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Pulse oximetry
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•Detects infrared light absorption at two wavelengths, and calculates saturation of hemoglobin with O2 •Contains algorithm to subtract non-pulsatile reflectance •PaO2 = SpO2 – 30 (estimate)
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MAP needed for
1.brain 2.renal 3.muscles |
Cerebral and coronary (50-60 mmHg) §Renal and mesenteric (60-70 mmHg) §Muscle compartments (>70 mmHg)
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pulse Not palpable lower than MAP of about
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40
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sphyngomanometry:
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uses a cuff to occlude arterial supply to a known pressure, and define the return of flow (systolic)
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oscilometric:
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uses cuff, but computer detects oscillations of artery. (S, D and M)
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calculated MAP=
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D+1/3(S-D)
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Pulse Oximetry•Accuracy
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•Fair SpO2 ,<> 75-90% •Overestimation SpO2< 70% • Underestimation SpO2 > 90%
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Heart Rate limits on CO
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•Heart rate directly contributes to CO up to a point, then it decreases CO: §Decreasing preload (most of filling occurs in first half of diastole) §Decreasing SV §Decreasing myocardial oxygenation potential (coronary arteries fill in diastole)
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•Type of murmur changes treatment during anesthesia:
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§Restrictive conditions require increased filling pressures §Regurgitant conditions are aided by increasing forward flow §Failing myocardium requires contractile assistance
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Central Venous Pressure
Monitoring |
•Zero reference = RA •Measurement in cmH2O • with a water column •Or in mmHg with • a pressure transducer •1 mmHg = 1.36 cmH2O •CVP = 0-5 cmH2O in SA •CVP> 12 cmH2O, High •CVP < 0 cm H20, Low
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BP cuff should be what % of limb circumference
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30-40%
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Results of cooling
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Increased recovery time: mortality in some studies nDecreased metabolic rate and MAC (5% for each C°) nDecreased oxygen demand of tissues
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Capillary Filtration Pressure
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•Net Driving Pressure into Capillary •[(Pc-Pi) – (pp- pi)] §Pc = capillary hydrostatic pressure vArteriole approx. 35 mmHg vVenuole approx. 15 mmHg §Pi = interstitial hydrostatic pressure (0) §pp = plasma oncotic pressure (20-28 mmHg) §pi = interstitial oncotic pressure (3mmHg) •Balance » 10 mmHg fluid OUT of capillary • » 10 mmHg fluid IN to venule
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Disadvantages of Colloids
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•Circulatory overload •Anaphylactic reactions (incidence 0.033%) •Coagulation disorders: §‘Coating of platelets’ §Volume dilution of clotting factors vDextrans (worst) vStarches (hetastarch) vGelatins (not in use)
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Assessment of Hydration
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•Hydration is the presence of fluid in the interstitial space (intravascular and intracellular are far more difficult parameters to assess) §Dehydration for <3 days 80% ECF, 20% ICF §Dehydration for >3 days 60% ECF, 40% ICF •Koch and Graber
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Emergency Fluid Resuscitation
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•Aim: restore tissue perfusion & oxygenation •Shock fluid rates (high end value- constant re-evaluation will most likely limit these numbers): •Think ¼ blood volume to start §Blood volume: vDog 80-90 ml/kg (isotonic) vCat 60-70 ml/kg (isotonic) vColloid (dextran or hetastarch) 20ml/kg §7.5% Hypertonic saline in colloid 4ml/kg over 10min
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Acute Blood Loss
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•Goal: restore circulating blood volume (CBV) •Initially any fluid type will restore volume and maintain cardiac output •Volume of crystalloid must be 3 x volume of colloid for the same CBV •Replace red cells or use whole blood once bleeding is under control, or when loss exceeds 20% of blood volume •What comes out must go in
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