THE CLINICAL CHALLENGE

A general discussion of the diagnosis and treatment of seizure disorder is beyond the scope of this book. This chapter focuses on the considerations of airway management in the seizure patient. In the simple, self-limited, generalized seizure, airway management is directed at termination of the seizure and prevention of hypoxia from airway obstruction. Paralysis and intubation should be considered when decline despite supplemental oxygen or when typical first-line measures fail to terminate the seizure in a reasonable time. For the simple seizure, basic airway maneuvers, expectant observation (most seizures end spontaneously), supplemental high-flow oxygen, and vigilance are usually all that is necessary. Airway protection from aspiration is rarely required in the simple, self-limited seizure because the uncoordinated motor activity precludes coordinated expulsion of gastric contents.

Determining when to proceed from supportive measures to intubation is the main clinical challenge. The Epilepsy Foundation has revised its definition of status epilepticus as follows: Any continuous seizure activity for 5 or more minutes or multiple seizures without recovery to a baseline neurologic condition. The rationale for 5 minutes (previously 30) was that the majority of non–status-related seizures are much shorter in duration, typically 2 to 3 minutes. The brain’s compensatory mechanisms to prevent neuronal damage rely on adequate oxygenation and cerebral blood flow are often compromised well before 30 minutes, particularly in patients with underlying illness. Evidence also suggests that with longer seizure duration, pharmacologic therapies become less effective. The mortality rate for status epilepticus is >20% and also increases with duration of seizure activity. Therefore, intubation should be undertaken early as a part of overall supportive therapy in cases where the seizure is not promptly terminated by anticonvulsant medications. The absolute and relative indications for intubation in the seizing patient are listed in Box 38-1.

APPROACH TO THE AIRWAY

Self-Limited Seizure

Most seizures terminate rapidly, either spontaneously or in response to medication, and require only supportive measures. Positioning the patient on his or her side, providing oxygen by face mask, suctioning secretions and blood carefully, and occasionally using the jaw thrust to relieve obstruction are usually all that is necessary to prevent hypoxia and aspiration. Bite blocks should not be placed in the mouths of seizing patients. They are not indicated and will only serve to increase the likelihood of injury. Attempts to ventilate during a seizure are usually ineffective and rarely necessary.

Prolonged Seizure Activity

Although most self-limited seizures do not require intubation, several indications exist for intubation in the prolonged seizure. Extensive generalized motor activity will eventually cause hypoxia, hypotension, significant acidosis, rhabdomyolysis, hypoglycemia, and hyperthermia. Respiratory depression may result from high doses or combinations of anticonvulsants. Hypoxia despite supplemental high-flow oxygen, is an indication for immediate intubation.

No clear guideline specifically defines the duration of seizure activity requiring intubation. A good rule of thumb is that patients with seizures lasting <5 minutes with evidence of hypoxemia (central cyanosis or pulse oximetry readings <90% despite supplemental oxygen and clearly inadequate respirations) or patients with seizures lasting beyond 5 minutes despite appropriate anticonvulsant therapy should be considered for intubation. Generally, when first-line (benzodiazepine) anticonvulsants fail to terminate grand mal seizure activity, rapid sequence intubation (RSI) is indicated. Phosphenytoin, which has a relatively short loading time, may be initiated as a second-line agent before intubation, if time allows. Other second-line anticonvulsants (phenytoin and phenobarbital) require at least 20 minutes for a loading dose; therefore, at the time of initiation, intubation is advisable. The initiation of a propofol or phenobarbital infusion may also be an indication for intubation because of their respiratory depressant effects. Both agents act synergistically with benzodiazepines, which increases the likelihood of apnea and the need for airway management.

RSI is the method of choice in the seizing patient. In addition to its technical superiority, RSI ends all motor activity, allowing the body to begin to correct the metabolic debt. However, cessation of motor activity while the patient is paralyzed does not represent termination of the seizure, and effective loading doses of appropriate anticonvulsants (e.g., phenytoin) are required immediately after intubation. The recommended technique for the seizure patient is described in Box 38-2.

Standard RSI technique is appropriate in the seizing patient with the following modifications:

1. Preoxygenation: Preoxygenation may be suboptimal because of uncoordinated respiratory effort; therefore, pulse oximetry is critical. After giving succinylcholine, the patient may desaturate to <90% before complete relaxation and thus may require oxygenation using a bag and mask apparatus and 100% oxygen before attempts at intubation and continuous passive oxygenation by nasal cannula at 5 to 15 L per minute throughout the intubation sequence.

2. Paralysis with induction: Etomidate is a good induction agent if there is associated hypotension. Etomidate may raise the seizure threshold (and therefore inhibit seizure activity) in generalized seizures. Ketamine has been shown to be effective at terminating status epilepticus and at reducing the need for intubation in children. Propofol has also been used as an induction agent in this setting at a dose of 1.5 mg per kg. Little data exist on propofol as an induction agent in patients with seizures; however, there is evidence that it provides rapid suppression of seizure activity after a bolus and infusion and has been used in refractory status epilepticus. Midazolam is an alternative, but the dosage reduction required in a hemodynamically compromised patient means it functions poorly as an induction agent. It is not known whether midazolam offers any additional anticonvulsant activity in a setting in which benzodiazepine seizure therapy has already been maximized. The full induction dose of midazolam is 0.3 mg per kg, but this often is reduced to 0.1 to 0.2 mg per kg for status epilepticus patients to prevent hemodynamic compromise, particularly because most patients have already received benzodiazepine therapy. Succinylcholine is recommended for neuromuscular blockade in this setting because of its very short duration of action. An intubating dose of rocuronium will result in paralysis for roughly an hour and thus will prevent the clinician from knowing if there is ongoing seizure activity without continuous electroencephalogram (EEG) monitoring.

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Noninvasive Mechanical Ventilation Distorted Airways and Acute Upper Airway Obstruction Reactive Airways Disease Blind Intubation Techniques The Difficult Pediatric Airway Video Laryngoscopy

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