قراءة
عرض

Laboratory Investigations:

Arterial blood gases:
↓pO2, ↑pCO2: respiratory center depression, aspiration pneumonia, pulmonary edema
Plasma electrolytes - potassium:
Hypokalemia
normal:
3.5 - 5 mE/L
- β2 agonists, caffeine, theophylline → ↑cAMP →↑ NaK-ATPase activity.
- Diuretics that ↑K+ loss into urine (loop diuretics and thiazides).
- Toluene (unknown mechanism; causes extreme muscle weakness)
- Barium (Ba2+ blocks K+ channels in the membrane of excitable cells → ↓K+ efflux

Hyperkalemia

- β blockers →↓cAMP →↓NaK-ATPase activity.
- Digitalis, fluoride (inhibits NaK-ATPase) and lithium.
- Rhabdomyolysis (e.g., after convulsion), hemolysis (e.g., arsine intoxication)

Plasma electrolytes-Anion-gap: calculated from plasma Na+, K+, HCO3- and Cl- levels

Calculation(Na+ + K+) (Cl- + HCO3-) NORMAL VALUE: <12 mE/L
Increased
anion
gapOccurs when an acid accumulates in the blood and causes a decrease in HCO3- concentration. The acid protonates HCO3- and thus H2CO3 is formed, which is converted into CO2 and H2O by carbonic anhydrase.
Examples:
- aspirin, isoniazid, iron; methanol, ehtylene glycol intoxication.
- drug-induced seizure (causes lactic acidosis).
Diff. diagnosis: shock-induced lactic acidosis, diabetic ketoacidosis
Plasma osmolality (Posm), osmolal gap:
Posm can be * measured or * calculated.
Measured PosmObtained by Freezing Point Depression OsmometerCalculated Posm= 2 x plasma [Na] + [glucose] + [BUN]Osmolal gap= MEASURED Posm CALCULATED Posm
(NORMAL VALUE: <10 units)Iincreased
osmolal gapOccurs when large amounts of an osmotically active compound accumulate in the blood.
Examples: ethanol, isopropanol, methanol, ethylene glycol intoxication


Osmolality is a measure of the osmoles (Osm) of solute per kilogram of solvent (Osm/kg), osmolarity is the number of osmoles of solute per liter (L) of solution (Osm/L).
Freezing-point depression is the decrease of the freezing point of a solvent on addition of a non-volatile solute. Examples include salt in water, alcohol in water. The radiator fluid in an automobile is a mixture of water and ethylene glycol.

Laboratory tests for renal function:

BUN, serum creatinine: their elevation indicates ↓ in the GFR; caused by nephrotoxic drugs and shock
Oxalate crystals in urine sediment: caused by ethylene glycol (converted into oxalic acid → Ca-oxalate)
Pinkish color of urine: phenothiazine intoxication
Ketonuria without metabolic change: isopropyl alcohol and acetone intoxication
ketonuria with metabolic acidosis: salicylate poisoning

Laboratory tests for hepatic function:

↑ serum ALT, AST (indicate hepatocellular injury)
↑ serum GGT, AP (indicate cholestasis)

Instrumental examinations:

ECG
 Bradycardia, AV block: beta receptor blockers
 Extreme bradycardia, PQ prolongation or AV block, ventricular arrhythmias: digitalis
 Widening of QRS (>0.1 sec): tricyclic AD, carbamazepine, quinidine, amantadine, Ca-channel blockers
 QT prolongation (indicate delayed repolarization): phenothiazines, fluorokinolones, Ca-channel blockers, As
 Ischemic changes (ST elevation): carbon monoxide (hypoxia), cocain


Endoscopic examination: obligatory after corrosive ingestion (e.g., acids, bases)
 To determine if gastric surgery is needed or not (perforation?)
 Do not be afraid, the gastroscop does not cause perforation in the hand of an expert!

X-ray examination

 Abdominal X-ray: radiopaque toxins such as iron-containing pills, enteric-coated tablets, heavy metals can be visualized
 Chest X-ray: may reveal aspiration pneumonia and pulmonary edema
 CT scan: when head trauma is suspected (intracranial hemorrhage?)

Analysis of the toxicant:

a. Qualitative analysis (screening) for unknown toxicants from urine or blood to answer the question:
What may have caused the intoxication?
1. Rapid screening tests using special kits and one-step analysis used for:
- street drugs and common hypnotics
These typically detect:
morphine, methadone, barbiturates, benzodiazepines, amphetamine, cocaine, cannabinoids from urine.
- paracetamol and salicylate from a few drops of blood: (a one-step immunoassay)
2. Screening tests for a wider range of compounds:
- TLC analysis
- Special HPLC analysis: for identification of 450 drugs (except paracetamol, aspirin)
- HPLC-MS/MS: an ultimate method for toxicant identification


b. Quantitative analysis of the serum level of a known toxicant in order to answer the questions:
How severe is the toxicant exposure? Is a specific treatment procedure needed?
Examples:
 Acetaminophen (by FPIA) - Fluorescence polarization immunoassay to determine if the acetaminophen plasma conc is high (>150 mg/L at 4 hrs) and N-acetylcysteine administration is needed.
 Li (by flame photometry) – is hemodialysis necessary?
 Salicylate (by Trinder reaction:) – is hemodialysis necessary?
 Methanol, ethylene glycol (by GC) – is hemodialysis necessary?
 Digoxin*, theophylline*, phenytoin*, (by FPIA) – is hemoperfusion necessary?
NOTE: (FPIA is also used for monitoring drug levels in plasma, e.g., gentamicin.)

2

IMPORTANT NOTE:

The Posm and osmolal gap are used as a rapid screening tests for methanol and ethylene glycol intoxication. A high plasma osmolal gap is highly suggestive of the presence of either methanol or ethylene glycol (and their acidic metabolites).
(Differential dg.: A high plasma osmolal gap is also seen in diabetic or alcoholic keto-acidosis, lactic acidosis, and after infusion of hypertonic mannitol.)

NOTE:

The patient who ingested a corrosive (acid, base) should not drink milk! Milk precipitates in the stomach, preventing the gastroscopists from seeing the mucosa! The patient should not take acid (to neutralize a base) or base (to neutralize an acid)! This may cause over-titration. Dilution by drinking water is OK.




رفعت المحاضرة من قبل: Omar The-Czar
المشاهدات: لقد قام 4 أعضاء و 61 زائراً بقراءة هذه المحاضرة








تسجيل دخول

أو
عبر الحساب الاعتيادي
الرجاء كتابة البريد الالكتروني بشكل صحيح
الرجاء كتابة كلمة المرور
لست عضواً في موقع محاضراتي؟
اضغط هنا للتسجيل