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Cholinesterase Inhibitors: Including Insecticides and Chemical Warfare Nerve Agents
Part 4: The Cholinergic Toxidrome
Section 6: Effects on Routine Laboratory Tests

Course: WB 1098
CE Original Date: October 16, 2007
CE Renewal Date: October 16, 2010
CE Expiration Date: October 16, 2012
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Learning Objectives

Upon completion of this portion of the case study, the learner should be able to:

  • Describe what routine laboratory tests can be altered by acute cholinesterase inhibitor toxicity.

Introduction

Routine laboratory test results are usually normal in patients with cholinesterase inhibitor toxicity. However, a few notable exceptions may confound the diagnosis. Examples are listed in the table below. (Schenker, Louie et al. 1998; Tareg et al. 2001; Wiener and Hoffman 2004)

Laboratory Test
Results That May Occur in Cholinesterase Inhibitor Toxicity
Presumed Cause

EKG

Note: In a series of 105 cases, Hayes et al. found that --- with the exception of rate changes --- EKG abnormalities occurred only 5% of the time. (Hayes, van der Westhuizen et al. 1978)

  • Tachycardia or bradycardia (Leikin, Thomas et al. 2002)
  • A-V block (Suzuki, Kohno et al. 1997)
  • Prolonged Q-T (Clark 2002)
  • Peaked T-waves (Hayes, van der Westhuizen et al. 1978)
  • Torsades de pointes (Leikin, Thomas et al. 2002)

 

Ketoacidosis

Present (Schenker, Louie et al. 1998)

n/a

Serum amylase

Elevated (Tareg et al. 2001; Wiener and Hoffman 2004)

Injury to pancreas from parasympathetic over­stimulation and hypersecretion (Tareg et al. 2001)

Serum creatine kinase (CK)

Elevated (Okumura, Takasu et al. 1996; Wiener and Hoffman 2004)

Fasciculations, seizures

Serum glucose

Elevated (Hayes, Wise et al. 1980; Schenker, Louie et al. 1998; Tareg et al. 2001)

Nicotinic effect on the adrenal medulla with catecholamine release (Tareg et al. 2001)

Serum lipids and triglycerides

Decreased (Wiener and Hoffman 2004)

n/a

Serum potassium

Decreased (Suzuki, Kohno et al. 1997; Tareg et al. 2001; Wiener and Hoffman 2004)

Increased

Nicotinic effect on the adrenal medulla with catecholamine release (Tareg et al. 2001)

Effect of muscular activity during seizures

Urine glucose

Elevated (Hayes, Wise et al. 1980; Schenker, Louie et al. 1998; Tareg et al. 2001)

Nicotinic effect on the adrenal medulla with catecholamine release (Tareg et al. 2001)

Urine proteins

Elevated (Hayes, Wise et al. 1980; Schenker, Louie et al. 1998; Tareg et al. 2001)

n/a (Tareg et al. 2001)

White blood cell count

Elevated with a left shift (Hayes, Wise et al. 1980; Okumura, Takasu et al. 1996; Schenker, Louie et al. 1998; Tareg et al. 2001)

Nicotinic effect on the adrenal medulla with catecholamine release (Tareg et al. 2001)

n/a = not addressed in the reference.

Key Points

  • A number of routine laboratory tests can be altered due to the cholinergic toxidrome of cholinesterase toxicity.
  • These can lead to misdiagnosis.
   

Progress Check

22. Cholinesterase toxicity has been known to cause abnormally high levels of which of the following laboratory tests. (Choose ALL correct answers)

A. Serum glucose.
B. White blood cell count.
C. Serum amylase.
D. CPK.
E. None of the above.

Answer:

To review relevant content, see Introduction in this section.

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