Making sense of metabolic alkalosis...

[MPKH]

Hi all,

I'm not sure if this is ther right forum to post this...if not, mods please move this to its proper home.

My question concerns a patient's condition. He came in with the chief complaint of hip pain, and due to a series of human errors, he was given morphine round the clock instead of PRN. Sometime during yesterday's afternoon, he became unresponsive, and went unconscious. Blood work were drawn, and his blood gas were as follows

pH: 7.55

pCO2: 34.9

PO2: 141

HC03: 30.7

O2 sat: 99% (with 2L on rebreather)

From looking at his blood gas, I understand that the patient is experiencing uncompensated metabolic alkalosis. The elevated pH and bicarbonate are both indicative of metablic alkalosis, uncompensated as the pH is quite out of the normal range. What doesn't really make sense to me is the respiratory side of thing--why is the pCO2 so low? I thought that with a disturbance in the metabolic acid/base control, respiratory efforts will be made to try to balance the disturbance. As well, I know that with metabolic alkalosis, the body will hypoventilate to conserve CO2 to lower the pH...and the patient was hyperventilating, at a resp rate of 20-26! Is it due to the respiratory system being unable to compensate?

As well, how do you correct uncompensated acidosis/alkalosis?

Thanks!

[Esme12, ASN, BSN, RN]

Hi all,

I'm not sure if this is there right forum to post this...if not, mods please move this to its proper home.

My question concerns a patient's condition. He came in with the chief complaint of hip pain, and due to a series of human errors, he was given morphine round the clock instead of PRN. Sometime during yesterday's afternoon, he became unresponsive, and went unconscious. Blood work were drawn, and his blood gas were as follows

pH: 7.55

pCO2: 34.9

PO2: 141

HC03: 30.7

O2 sat: 99% (with 2L on rebreather)

From looking at his blood gas, I understand that the patient is experiencing uncompensated metabolic alkalosis. The elevated pH and bicarbonate are both indicative of metabolic alkalosis, uncompensated as the pH is quite out of the normal range. What doesn't really make sense to me is the respiratory side of thing--why is the pCO2 so low? I thought that with a disturbance in the metabolic acid/base control, respiratory efforts will be made to try to balance the disturbance. As well, I know that with metabolic alkalosis, the body will hypoventilate to conserve CO2 to lower the pH...and the patient was hyperventilating, at a resp rate of 20-26! Is it due to the respiratory system being unable to compensate?

As well, how do you correct uncompensated acidosis/alkalosis?

Thanks!

You state that the patients respiratory rate is now 22-26, which indicates to me that the patient is already trying to compensate for the alkalosis and hypoventilation and elevated PCO2...by increasing the RR rate..........which was probably higher before intervention and transport. If the prehospital PCO2 was taken and it was 60 and just stimulating the patient during transport the body will begin to compensate to low off that CO2 in the awakening process to begin correction with out medical intervention.

Alkalosis? Treatment depends on the cause. HCL IV can be given and dialysis performed if unable to correct in any other way.

Acidosis? Treatment again depends on causative factor....from IV ringers lactate, IV bicarb dialysis, hyperventilation.

Metabolic alkalosis

Medscape: Medscape Access

Metabolic acidosis

Medscape: Medscape Access

medscape requires registration but it is an amazing resource and it is free!

I am curious.......Why is the patient on a non rebreather at only 2 liters?

[MPKH, BSN, RN]

Something seems wonky here. Are you sure these values are correct? If you went PaCo2, 34.9 is barely low...not VERY low?

Yes I am sure those values are correct. The PaCO2 is on the low side, which was what was boggling my mind

[MPKH, BSN, RN]

The bicarb response to compensate for acidosis in my understanding takes many days.....

Admittedly we were not supplied with any sort of time frames.....

He was admitted in the afternoon on Day 1, and the doc had written the order, one of which included the PRN morphine that was given as scheduled due to human mistakes. On the afternoon of Day 2, he started going downhill (unresponsive, low O2 sats, unable to rouse). Labs were drawn in the evening of Day 2.

[MPKH, BSN, RN]

I am curious.......Why is the patient on a non rebreather at only 2 liters?

Thanks Esme for the links :) I will definitely look it up...and as for the non rebreather...he was needling a higher flow at the beginning, but got better....the nurse was just busy in doing every thing else, and when she turned it down to 2L, left on the rebreather. I'm aware that rebreathers are normally used for O2 flow higher than 5L/min.