Chapter 26: Drug Overdose

Introduction

Patients with overdose are a small percentage of those mechanically ventilated. Many of these patients require immediate intubation and mechanical ventilation—often by prehospital personnel. Ventilation of these patients is usually straightforward. However, complications can complicate the course of mechanical ventilation if not managed correctly.

Overview

The patient presenting with a drug overdose is frequently obtunded and unable to effectively maintain spontaneous breathing. However, with some classes of drugs (eg, tricyclic antidepressants) central nervous system hyperactivity may be the initial clinical presentation. If ingested in sufficient quantity, all drugs can result in respiratory depression and necessitate intubation and mechanical ventilation (Table 26-1). In addition, cardiovascular compromise commonly occurs with many types of drug overdoses. Narcotics and sedatives frequently result in hypotension, while tricyclic antidepressants and cocaine can cause life-threatening arrhythmias. The length of ventilatory support may be short or prolonged depending on the drug ingested, the quantity ingested, and the presence of underlying lung disease or complications. Patients may have periods of wakefulness followed by periods of profound respiratory depression. Even when the quantity of ingested drug is insufficient to depress spontaneous breathing, risk of aspiration may still be a primary concern necessitating close observation or intubation for airway protection.

Mechanical Ventilation

Indications

Patients with drug overdose are intubated to facilitate mechanical ventilation and for airway protection. Mechanical ventilation is usually initiated due to apnea or acute ventilatory failure. Oxygenation is often not a concern with these patients unless aspiration has occurred.

Ventilator Settings

These patients are not difficult to ventilate unless aspiration has occurred. They tend to be young and otherwise healthy without underlying lung disease. The ventilatory mode of choice is A/C (continuous mandatory ventilation [CMV]) provided with either pressure or volume ventilation (Table 26-2 and Figure 26-1). Any mode with a backup rate is acceptable. In spite of the fact that the lungs are normal, V_T and airway pressures should always be lung-protective. As a result a V_T of 6 to 8 mL/kg ideal body weight is appropriate with a rate of about 15 to 20/min, dependent on Paco₂. If volume-controlled ventilation is selected, an inspiratory time of 1 second is appropriate. With pressure-controlled ventilation, the pressure control level should be set to provide the desired V_T of 6 ...