Quote from vic_rn
a patient was found down after an unknown, but believed prolonged over 3-6 hrs, unconscious. emsd to hospital, intubated. severe metabolic acidosis, with initial ph of 7.1, co2 70s, po2 60s on 100% fio2. obvious aspiration pneumonia. sedated with propofol, prvc rate of 24. despite adequate comfort sedation, patient respirations averaging 30-45 bpm. low dose bicarb gtt in use.
it was suggested to increase patient sedation to the point of overcoming respiratory drive. just wondering if this is common practice. i thought allowing the patient to remain tachypneic would reduce co2. also thinking that oxygenation would not be responsive to reduced resp rate as the patient was not 'bucking' or fighting the ventilator breaths.
do you generally allow the patient to breath instinctively, or block spontaneous respirations in initial recovery?
i am new in dealing with med icu patients and would appreciate any education and insight!
respiratory acidosis is caused by any condition which increases the pco2
while increased production of co2
(hyperthermia, cardiopulmonary arrest) is a possible cause of hypercapnia, the vast majority of cases are due to impaired removal of co2
through the lungs. hypoventilation, ventilation-perfusion mismatch and impaired alveolar gas exchange can all lead to hypercapnia. therefore, the broad categories of disease which can lead to respiratory acidosis include: respiratory center depression, neuromuscular disease, restrictive extrapulmonary disease, intrinsic pulmonary and small airway disease, large airway obstruction, and increased co2
production with impaired alveolar ventilation.
causes of metabolic alkalosis include loss of acidic chloride-rich fluids from the body and chronic administration of alkali. in small animal practice, most cases of metabolic alkalosis are caused by vomiting of stomach contents. abomasal reflux of hydrochloric acid (hcl) into the rumen will cause metabolic alkalosis in ruminants.
there are two types of metabolic acidosis. both are characterized by a decrease in the[hco3
] but they differ in how that decrease occurs. secretional metabolic acidosis is caused by a direct loss of bicarbonate-rich fluid such as diarrhea or saliva. titrational metabolic acidosis is caused by the presence of non-co2
acids that titrate bicarbonate causing a decreased [hco3
you have a few things occurring here. this very sick patient has both metabolic and respiratory acidosis as well as remaining hypoxic. the rest of the vent settings are just as important as to whether sedating the patient's inate respiratory drive is prudent. what is the tidal volume, is there pressure support and peep? what is the patients bicarb and ion gap....what is the base excess.
it's obvious that the patient is trying to assist the metabolic acidosis and blow off co2 by increasing the respiratory rate. if however the patient continues to work so hard to breathe there will be a further build up of lactic acid. this patient needs moderately aggressive resuscitation with bicarb as well as ventilation to decrease the co2 thereby increasing the ph and correcting (hopefully) the hypoxia which further contributes to the acidosis.
what is the patients lactic acid? how long after intubation were these gasses? the supression of the respiratpry drive, because it's assisting with acid base correction, needs to be done cautiously but if the patient's increase drive it contributing to the build up of lactic acid then the ventilation needs to be meticuously controlled with the patient's drive shut down to allow the interventions have their theraputic effect.
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this patient needs to be adequately ventilated first, to drop the pco2 level and increase the po2 and by correcting these at the same time correcting the metabolic acidosis with bicarb
being new to critical care you may find this helpful........http://www.ccmtutorials.com/index.htm
the bird's eye-view, two components:
- respiratory: when breathing is inadequate carbon dioxide (respiratory acid) accumulates. the extra co2 molecules combine with water to form carbonic acid which contributes to an acid ph. the treatment, if all else fails, is to lower the pco2 by breathing for the patient using a ventilator.
metabolic when normal metabolism is impaired - acid forms, e.g., poor blood supply stops oxidative metabolism and lactic acid forms. this acid is not respiratory so, by definition, it is "metabolic acid." if severe, the patient may be in shock and require treatment, possibly by neutralizing this excess acid with bicarbonate, possibly by allowing time for excretion/metabolism.
that's it! the whole of acid-base balance in six sentences. as you explore this site, keep this bird's eye-view in mind. we will also have to deal with low levels of metabolic and respiratory acid (alkalosis) - but this initial overview helps to keep the subject in focus.
i am sure this made it clear as mud.....i hope it helped some.