Lab results in CO poisoning: 1. Analysis of carboxyhemoglobin (HbCO) requires direct spectrophotometric measurement in specific blood gas analyzers.Elevated CO levels are significant; however, low levels do not rule out exposure, especially if the patient already has received 100% oxygen or if significant time has elapsed since exposure. HbCO levels in cigarette smokers typically range from 3-5%, but may be as high as 10% in some heavy smokers. 2.Bedside pulse carbon monoxide (CO)-oximetry is now available but requires a special unit and is not a component of routine pulse oximetry. 3.Arterial blood gas measurement PaO2 levels should remain normal. Oxygen saturation is accurate only if directly measured but not if calculated from PaO2, which is common in many blood gas analyzers. As with pulse oximetry, estimate PCO2 levels by subtracting the carboxyhemoglobin (HbCO) level from the calculated saturation. PCO2 level may be normal or slightly decreased. Metabolic acidosis occurs secondary to lactic acidosis from ischemia . 4.Troponin, creatinine kinase-MB fraction, myoglobin Myocardial ischemia is frequently associated with patients hospitalized for moderate-to-severe CO exposure and is a predictor of mortality. Patients with preexisting disease can experience increased exertional angina with HbCO levels of just 5-10%. At high HbCO levels, even young healthy patients develop myocardial depression. 5.Creatinine kinase, urine myoglobin: Nontraumatic rhabdomyolysis can result from severe CO toxicity and can lead to acute renal failure. 6.Complete blood count Look for mild leukocytosis. 7.Disseminated intravascular coagulation (DIC) and thrombotic thrombocytopenic purpura (TTP) require further hematologic studies. 8.Electrolytes and glucose level - Hypokalemia and hyperglycemia with severe intoxication 9.Blood lactate - An elevated lactate level is an indication of severity; in one study, a lactate level of 1.85 mmol/L or above had a sensitivity of 70.8% and a specificity of 78.0% to predict the need for hyperbaric oxygen therapy. If the source of the CO was a house fire and the lactate level is 10 mmol/L or higher, the patient may have concomitant cyanide poisoning. 10.BUN and creatinine levels - Acute renal failure secondary to myoglobinuria 11.Liver function tests - Mild elevation in fulminant hepatic failure 12.Urinalysis - Positive for albumin and glucose in chronic intoxication 13.Methemoglobin level - Included in the differential diagnosis of cyanosis with low oxygen saturation but normal PaO2 14.Toxicology screen - For instances of suicide attempt 15. Ethanol level - A confounding factor of intentional and unintentional poisonings 16.Cyanide level - If cyanide toxicity also is suspected (eg, industrial fire); cyanide exposure suggested by an unexplained metabolic acidosis; rapid determinations rarely are available. Smoke inhalation is the most common cause of acute cyanide poisoning.
Posted on: Sat, 27 Dec 2014 12:53:39 +0000
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