Cholinesterase Inhibitors: Including Insecticides and Chemical Warfare Nerve Agents

Part 4: The Cholinergic Toxidrome

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Section 6: Effects on Routine Laboratory Tests

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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)

Introduction
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)
  • 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)
  • Tachycardia or bradycardia (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.
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