Chapter 6 Oxygen Balance and Acid-Base Status

Question 1

What will cause a** Right Shift** of the Oxyhemoglobin Dissociation Curve

Answer 1

Acidosis
Fever
Increased CO2 production

Question 2

What will cause a** Left Shift** of the Oxyhemoglobin Dissociation Curve

Answer 2

Hypothermia
Alkalosis
Low CO2

Question 3

How does a** Right Shift** of the Oxyhemoglobin Dissociation Curve **affect Hemoglobins Affinity of Oxygen **

Answer 3

Decreased Affinity
(Oxygen Released to Tissues Easier, but requires higher PO2 to fully saturate hemoglobin)

Question 4

How does a** Left Shift** of the Oxyhemoglobin Dissociation Curve **affect Hemoglobins Affinity of Oxygen **

Answer 4

Increased Afffinity
(Harder to unload Oxygen to tissues, but lowwer PO2 required to saturate)

Question 5

What is Pre-Load

How is it measured

Answer 5

Ventricular Volume at the end of Diastole

Central Venous Pressure or Pulmonary Artery Occlusion Pressure

Question 6

What is afterload

Answer 6

myocardial wall tension required to overcome the resistance, or pressure load, that opposes ejection of blood from the ventricle during systole

Question 7

Normal Svo2 (Venous O2 Saturation) is …

Normal Scvo2 (Central Venous O2 Saturation) is …

Answer 7

Normal Svo2 is >65%.

Normal Scvo2 is >70%.

Question 8

What lab can help assess oxygen balance

Answer 8

Lactic Acid (Elevation means anaerobic respiration is occuring)

Question 9

An SPO2 of 94% equates to a PaO2 of…

Answer 9

Pao2 of at least 60 mm Hg

Question 10

Indications for Arterial Line

Answer 10

Requiring continuous hemodynamic monitoring

Requiring 4 Atrerial blood samples in 24 hours

Question 11

What is a normal Pulse Pressure

Answer 11

Pulse Pressure = Systolic Pressure – Diastolic Pressure

Normal = 30–40 mm Hg

Question 12

What should you do if you suspect distal ischemia after placing an arterial line

Answer 12

Remove it

Question 13

What is a normal Central Venous Pressure (CVP)

Answer 13

2 to 6 mm Hg, (measurements should be made at the end of expiration)

Question 14

What is a low CVP suggestive of

Answer 14

Low intravascular volume / Decreased Preload

Question 15

How can you assess for fluid responsiveness

Answer 15

250-500mL Fluid Challenge

Passive Leg Raising

Question 16

When should Blood Transfusion be considered in critically ill patients

Answer 16

<7g/dL (<8g/dL if heart failure/ischemia)

Question 17

How do you assess the adequacy of Respiratory compensation in Metabolic Acidosis

Answer 17

Winter’s Formula/Expected

Expected Paco2 = 1.5 × [HCO2] + 8 ± 2

Question 18

How do you calculate the anion gap

What is a Normal Gap

How do you correct for hypoalbuniemia

Answer 18

AG = Na+ – (Cl- + HCO2-)
Normal AG = 10 ± 4
For Every Decrease in albumin by ag/dL add 2.5-3 to AG

Question 19

Causes of Wide Anion Gap Acidosis

Answer 19

Question 20

Cause of Normal Anion Gap Acidosis

Answer 20

Often GI / Renal Loss of Bicarb

Question 21

How Do you Differentiate Chloride Responsive and Chloride Unresponsive Metabolic Alkalosis

Answer 21

urine chloride <20 mmol/L =chloride-responsive metabolic alkalosis

urine chloride >20 mmol/L = chloride-resistant metabolic alkalosis

Question 22

What is normal respiratory compensation for Metabolic Alkalosis

Answer 22

Paco2 rise 6 to 7 mm Hg for every increase of 10 mmol/L in HCO2

Question 23

How to Differentiate Acute Vs Chronic Respiratory Acidosis

Answer 23

Acute- HCO2 increases** 1 mmol/L** for every 10mmHg increase in PaCO2 (maximum of 30 to 32 mmol/L)

Chronic-HCO2 increases 3.5 mmol/L for each increase of 10 mm Hg in Paco2

Question 24

Differentiating Acute Vs. Chronic Respiratory Alkalosis

Answer 24

[HCO2] decreases** 2 mmol/L in acute** respiratory alkalosis and** 5 mmol/L in chronic** respiratory alkalosis for each decrease of 10 mm Hg ) in Paco2