Monitoring Oxygen Balance and Acid-Base Status

13 important questions on Monitoring Oxygen Balance and Acid-Base Status

Oxyhemoglboin dissociation curve?

Acidosis and fever shift to the right resulting in a lower affinity of oxygen for hemoglobin

How can you clinically assess the determinants of cardiac output?

variabele: hr and rhythm: finger on pulse, ECG, SA02

Preload:
right heart: Neck vein disteion, liver enlargement, depente edema, CVP
left heart, presence of dyspnoe, orthopnea, pulmonary edema, crepitations

Afterload ( leftheart ) MAP

Contractility: ejection fraction and stroke volume estimate by echocardiography

What allow an indwelling arterial catheter?

continuous measurement of RR, pulse volume or pressure and MAP
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Where is the CVC placed and what does it meassure?

internal jugular or subclavian vein
It meassures central venous pressure, central venous oxygen saturation

How to determine if additional fluid is beneficial?

Passive leg raising (PLR)  : gravitational transfer of approximately 300 ml of blood. Reaction in 30 to 60 seconds; Fluidresponsiveness

What is the approach for evaluation of Acid-Base disorders?

1. check pH
2. Check HCO3 and PaCo2
3. if a respiratory disturbance is present, determine if it is an acute or chronic
4. if a metabolic disturbance is present, determine if it is an acute or chronic
5. Always calculate the aniongap

How to estimate the AG

na - ( CL + hco3 )

in severe hypoalbuminemia a decrease of AG of 2.5 a 3.0 mmol for every 1 albumin will occur.

To correct for this: AG corrected = ag observed + 2.5 ( normal - measured albumin )

Acidosis with normal AG ( often is increased )

hyperchloremic acidosis ( loss of hco3 or vlume reuscitation with normal saline )

How is metabolic alkalosis usually characterized?

chloride - depleted ( hypovolemic , most common )
chloride-expanded ( hypervolemic )

What is helpfull diagnostic tool in metabolic alkalosis?

Chloride test in urine. >20 chloride expanded
<20 chloride depleted.

What is the limit of renal (HCO3) compensation in respiratory acidosis?

45mmoll

How does sepsis presents itselfs in acid-base disorders?

respiratory alkalosis
metabolic acidosis

The causes of elevated anios gam metabolic acidosis can be remebered with the following mnemominc: MUDPILES.

Methanol, uremia, diabetic ketoacidosi, paracetamol, isoniazid, lactic acidosis, ethylene glycol and salicylates

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