Agency for Toxic Substances and Disease Registry 
Case Studies in Environmental Medicine (CSEM) 

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

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)

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