Carbon Monoxide

Given the Planet Hoth like winter weather out there, we are likely to see a few cases of….

Carbon Monoxide Poisoning

Carbon Monoxide is a colorless, odorless and nonirritating gas produced by the incomplete combustion of carbonaceous materials. Thus, we often see an increase in presentations during the winter, secondary to the use of indoor heating sources. It is one of the most common causes of unintentional poisoning deaths in the United States.

Carbon Monoxide impairs oxygen delivery to the tissues because of the high binding of CO to hemoglobin. 240x the affinity of oxygen! And thus causes a left shift in the oxyhemoglobin dissociation curve.

High Risk Exposures: smoke inhalation, stoves, portable heaters, gasoline powder generators, automobile exhaust, charcoal grills, inhaling spray paint

In acute poisonings, you can see:

• Central Nervous System: headache (most common symptom), malaise, confusion, depression, impulsiveness, hallucinations, agitation, drowsiness, visual disturbances, syncope, seizure, coma
• Gastrointestinal symptoms: abdominal pain, nausea, vomiting, diarrhea
• Respiratory symptoms: shortness of breath
• Cardiac: chest pain, palpitations, myocardial injury
• Delayed Neuropsychiatric syndrome: can arise 3 –240 days after recovery
• Note: often diagnosed as a viral syndrome

Examination and Tests:

• Suspect it! If you do not consider it, you cannot diagnosis it
• Base work-up on the patient’s symptoms and clinical exam
• HbCO … elevated levels are significant, but, a normal level does not rule out exposure
• Level does not correlate well with the clinical signs and symptoms
• Normal: 0.4-3%
• Smokers: 0-5% (some can have up to 10-15%)
• Mild poisoning: greater than 10% without clinical symptoms
• Moderate poisoning: greater than 10% with minor clinical signs/symptoms (headache, fatigue)
• Severe poisoning: greater than 20% with loss of consciousness, confusions or signs for cardiac ischemia
• SpO2 is not helpful as standard pulse oximetry cannot screen for CO, as it does not differentiate carboxyhemoglobin from oxyhemoglobin
• ABG
• Lactic acid
• BMET (look for hyperglycemia, hypokalemia, renal failure)
• CPK (look for signs of rhabdomyolysis)
• CXR (if there are pulmonary symptoms)
• Head CT (in patients who do not improve rapidly)
• ECG
• Cardiac Enzymes (if abnormal ECG or history of cardiac disease)
• Cyanide level (if smoke exposure)

Management:

• Remove the patient from the source (duh!)
• ABCs
• Oxygen. Oxygen Administration enhances the elimination of carbon monoxide from the body.  If the patient is symptomatic in the Emergency Department, use a NRB.
• Carbon Monoxide half-life on room air is 4-5 hours
• Carbon Monoxide half-life on 100% NRB is about 60-90 minutes
• Carbon Monoxide half-life with HBO treatment is about 30 minutes
• Treat until asymptomatic
• If pregnant, consult OB as they may need treatment for 24 hours
• Consider transferring for hyperbaric treatment if COHb is greater than 25%, if there is evidence for ongoing end-organ ischemia, if there is severe metabolic acidosis (pH less than 7.1), if there was a loss of consciousness, or in pregnant women with a level greater than 20% or signs of fetal distress.
• Note: These are controversial
• Don't forget other potiental exposures!  Make sure everyone else has been removed from the environment

Uncomplicated UTIs

Acute Uncomplicated Cystitis and Pyelonephritis

A common presentation to every Emergency Department, but practice variation is amazing.  What does the literature show?

Acute cystitis refers to an infection of the bladder (lower track) and it can occur alone or in conjunction with pyelonephritis (infection of the kidney, the upper track). 

We will focus on uncomplicated cases, in an otherwise healthy, non-pregnant adult. 

• So, what makes it a complicated urinary tract infection?  Complicated UTIs are associated with underlying conditions that increase the risk of infection or of failing therapy (obstruction, anatomical abnormality, urologic dysfunction or multi-resistant uropathogens). 

The vast majority of uncomplicated cystitis and pyelonephritis in women are the result of E. coli (75-95%), with other common causes being Proteus mirabilis, Klebsiella penumoniae and Staph saprophyticus.  Therefore, your local antimicrobial susceptibility patterns to E. coli should be the basis for treatment (contact your ID colleagues and/or lab for this information).

 

Clinical manifestations of cystitis consist of dysuria, urinary frequency, urinary urgency, suprapubic pain, and/or hematuria (note: these can be subtle in the extremes of age).

Clinical manifestations of pyelonephritis consist of those of cystitis plus fever (>38^oC), chills, flank pain, costrovertebral angle tenderness and nausea/vomiting. 

Diagnosis: on physical make note of temperature, costovertebral angle tenderness and an abdominal examination

Labs:

Urinalysis (either dipstick of microscopic) and urine culture with susceptibility

o   A urinalysis in the absence of a urine culture is sufficient for the diagnosis of uncomplicated cystitis if the symptoms are consistent with a UTI, unless there is reason to suspect antimicrobial resistance or other complicating features

• Urinalysis: Pyuria (in a clean catch, mid-stream urine specimen) is the most valuable diagnostic test for UTI, as it is present in almost all women with acute cystitis or pyelonephritis; its absence prompts the evaluation for another diagnosis. 

o   An abnormal result is ≥ 10 leukocytes/mL

o   If white cell casts are noted, they are diagnostic of an upper tract infection. 

o   The presence of hematuria is helpful since it is common in UTI but not in urethritis or vaginitis. 

• Urine Dipsticks look for the presence of:

o   Leukocyte esterase (an enzyme released by leukocytes, thus reflecting pyuria)

o   Nitrite (reflecting the presence of Enterobacteriaceae, which converts urinary nitrate to nitrite). 

o   The dipstick is most accurate for predicting UTI when it is positive for either leukocyte esterase or nitrite, with a sensitivity or 75% and a specificity of 82%

• Urine culture. Routine cultures are not generally necessary.  Consider obtaining prior to initiation of therapy if: the symptoms are not characteristic of UTI, if the symptoms persist or if they have recur within 3 months following prior treatment or if a complicated UTI is suspected. 

Differential Diagnosis: vaginitis, urethritis, structural uretheral abnormalities, painful bladder syndrome, pelvic inflammatory disease, nephrolithiasis

           

Treament:

• Cystitis:

·      Nitrofurantoin monohydrate/macrocrystals: 100mg PO BID for 5 days

o   Avoid if there is a suspicion for pyelonephritis and it is in contraindicated when creatinine clearance if < 60mL / min

·      Trimethoprim-sulfamethoxazole: 1 double strength tablet (160/800) BID for 3 days         

o   Avoid if location resistance is >20% or if the patient has taken TMP-SMX in the preceding 3 months

·      Fosfomycin trometamol: 3g in a single dose.  (more expensive and slightly less effective)

·      Fluoroquinolones (ciprofloxacin, levofloxacin, ofloxacin) for 3 days

o   Should be reserved for other uses other than acute cystitis

·      Beta-Lactams (amoxicillin-clavulanate, cefpodoxime, cefdinir & cefaclor) for duration of 7 days are less effective than TMP-SMX or the fluoroquinolones

o   Cephalexin is not well studied

o   Generally have inferior efficacy and more adverse effects compared with other agents, so they should be used with caution for uncomplicated cystitis

• Pyelonephritis

·      Urine culture should be obtained

·      Outpatient management is appropriate for patients with mild-moderate illness who can be stabilized with rehydration and have adequate follow-up

·      Fluoroquinolones are the only oral antimicrobials recommend for the outpatient empirical treatment of acute complicated pyelonephritis

o   Ciprofloxacin 500mg BID for 7 days or 1000mg ER for 7 days; consider an initial 400mg intravenous dose

o   Levofloxacin 750mg PO for 5-7 days

o   An initial dose of a long-acting parental antimicrobial (ceftriaxone 1g or an aminoglycoside) can be considered prior to starting oral treatment, especially if local resistance to fluoroquinolones is greater than 10%. 

o   If allergic to fluoroquinolones, give an initial dose of a long-acting parental antimicrobial (ceftriaxone 1g or an aminoglycoside) and then start TMP-SMX or an oral beta-lactam for 14 days

o   Other alternative is aztreonam 1g IV every 8-12 hours

What about men?

• Asymptomatic bacteriuria and symptomatic urinary tract infection are much less common in men due to the longer urethral length, drier periurethral environment and antibacterial substances in prostatic fluid. 
• Risk factors: insertive anal intercourse and lack of circumcision
• Treatment is similar to the treatment in women, except, nitrofurantoin and beta-lactams should not be used (do not achieve reliable tissue concentrations and are less effective for occult prostatitis. 

o   A 7 day course of antibiotics are recommended

References:

International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Disease.  Clinical Infectious Disease. 2011; 52(5):e103-e120

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