Chapter 126: Hydrocarbons

High-Yield Facts

• The primary concern after hydrocarbon ingestion is pulmonary toxicity.

• Viscosity, surface tension, and volatility are three important properties to assess the toxicity of liquid hydrocarbons.

• Coughing, gagging, chocking, and vomiting after hydrocarbon ingestion are presumptive of aspiration.

Introduction

The term hydrocarbon is used to describe a large number of organic molecules that contain mostly hydrogen and carbon atoms. Hydrocarbons are primarily derived from petroleum distillates but may also be derived from other sources such as plants, animal fats, and natural gas. Hydrocarbon-containing products are pervasive in daily life (Table 126-1).

In 2011, the National Poison Data System reported nearly 1700 pediatric hydrocarbon exposures in the United States.¹ The majority of those exposures were unintentional. The most common exposures reported were gasoline, kerosene, lamp oils, lighter fluids, and lubricating and motor oils. Young children tend to have accidental exposures; adolescent exposures tend to represent the abuse of volatile hydrocarbons or suicidal attempts. Fortunately, deaths from hydrocarbon exposures are rare.

Classification and Properties

There are two basic types of hydrocarbon molecules. The aliphatic compounds consist of a branched or straight chain structure; the cyclic hydrocarbons consist of a closed ring. Each of these basic types have many subtypes, all with varying characteristics such as hydrogen or carbonsubstitutions, the presence of one or more double covalent bond and multi-ring structures.

The length of the hydrocarbon chain affects the chemical properties of the molecule. Short-chain molecules, such as butane, are gases at room temperature. Intermediate length chains, which encompass the majority of chemical exposures, are liquids at room temperature. The long-chain hydrocarbons, such as paraffin and tar, are solids at room temperatures.

Viscosity, surface tension, and volatility are three important physical properties used to assess the toxicity of liquid hydrocarbons. Viscosity is the measurement of a liquid's resistance to flow. Volatility describes the tendency of a liquid to become a gas. Surface tension describes the property of adherence of a liquid compound along a surface. These three properties are used to assess the risk of pulmonary toxicity from a hydrocarbon ingestion.

Pathophysiology

Pulmonary toxicity is the primary concern after hydrocarbon ingestions. The exact pathogenesis of hydrocarbon-induced pulmonary toxicity is debated in the literature; however, aspiration of hydrocarbons can lead to direct injury of lung tissue.^2,3 The viscosity, surface tension, and volatility of hydrocarbons determine the risk of aspiration during an ingestion. Compounds with low viscosity, low surface tension, and high volatility have a higher risk of aspiration and subsequent pulmonary toxicity.