A patient around 55/m (70kg) year was admitted in ED with hypoxia condition, diabetic, hypertension and cardiac arrest. CPR was also done for around 20 minutes.
Primary atrial blood gas analysis of PCO2 was 210 mm of Hg. A mixed respiratory acidosis and metabolic acidosis condition.
patient's weight =70 kg
ventilator condition (mode=SIMV, VT=480,RR=16,PEEP=5, Fio2=95%, Bicarbonate is lower than expected so Na2CO3- was administered (IV).
After 4 hr on Ventilator atrial blood is taken for AVG analysis and AVG is done . PCO2 value was 184 mm of Hg on ventilator and PO2 was in Range.
Why did it slightly decrease as i expected ? or patient have other complicated diseases.
It would be interesting to know:
1) patient's weight
2) how you set the ventilator (mode, TV, RR,..)
3) if bicarbonate was administered
4) ABE base excess
To C.Rout..Sir.
thats why i have questioned to all. Because PaCo2 value (AVG) is very very High after putting on Ventilator (Taema) Ext..
I think this happen due to hyperventilation. But Pao2 is in range. and may be cause the brainstem area to become stimulated (chemoreceptors monitoring gas levels in the body),
Sir Meena, obviously the patient usa been hypoventilated: the tidal volume (VT) is too low. Set the VT of the ventilator with 600 ml and stop the bicarbonade infusion because at this point is deleterious. The metabolic acidosis is probably related to hemodinamic state. What are PAS, HR , uryne output and inotropic infusion? I set the FiO2 max at 0,55 and probably the respiratory and haemodinamic parameters will be better without lung oxygen toxicity.
OK
Following a cardiac arrest, even with effective CPR the most you're likely to achieve is 30% of the patient's normal cardiac output. Over 20 minutes you will get global intracellular hypoxia, accumulation of lactate and a metabolic acidosis. I note you did not mention the arterial blood pH. Was it in the range 7.1 to 7.2? The metabolic acidosis is why we always "hyperventilate" the patient at and after a cardiac arrest in order to limit the degree of acidosis. With inadequate ventilation you will see an accumulation of CO2 and the mixed metabolic and respiratory acidosis that you saw. Once the patient is on a mechanical ventilator, you should hyperventilate the patient to "blow off" the accumulated CO2 and move towards a normal pH. After recovery from a cardiac arrest, depending on the cause, you are likely to continue to see a low cardiac output and may need to put the patient on an inotrope. Inotropes don't work very well in the presence of an acidosis of that degree and I can see why you wanted to give the bicarbonate.
However, there is probably little point giving it until you have blown the patient down to a slightly lower than normal pCO2. By the time you get down to a pCO2 of about 35 mmHg you may find that you don't need the bicarbonate any more.
Next, if you did measure the blood gases after giving the bicarb, what would you expect to happen? You have a closed system with fixed ventilation. Imagine that the system has a high concentration of hydrogen ions. You have just added sodium bicarb. Write down the equilibrium equations in both directions from H2CO3. You are pouring in hydrogen ions and bicarbonate at one end. What is going to come out of the other end?
Finally, now that you have salvaged the patient - what caused the cardiac arrest??
Actually Bicarbonate infusion was stopped immediately when we saw the AVG report. HCo3- conc. was reached near to 20mm/lit. PH is in compensatory phase.
we have corrected at first Bicarbonate . PaCo2 value was also 42 mm of Hg at the same ventilator parameter and mode after 2 Hr.
Patient was also CAD problem and also follow up case of Cardiology.
After Removing ventilator Then he was on T -piece around 4 hrs.
Patient was Saved.
Thanks God.!!
With rescue of spontaneous circulation the close system (central venous blood) with high pCO2 became open system and pCO2 decrease, but tissue and cellular pCO2 is much higher than venous pCO2 and CO2 wash out slowly to venous system. Your hypoventilated patient had much than one reason tohave high pCO2. Note that pO2 in physiologic range with FiO2=95% get a critically low P/F value