Seizures are one of the most common conditions encountered by EMS providers and one where critical interventions can significantly affect patient outcomes [1].
Oxygenation and ventilation can be compromised during prolonged seizures, as well as during the postictal phase after seizures. Here are three things you should know about seizures and respiratory compromise.
1. Seizures can cause upper airway obstruction and respiratory depression
A seizure is an episode of abnormal electrical discharges from neurons in the brain that causes a change in behavior, sensory perception or motor activity [3]. Seizures can be generalized or partial, depending on how much of the brain is affected [4].
Generalized tonic-clonic seizure is the most common type of seizure EMS providers encounter. Generalized tonic-clonic seizures occur when both hemispheres of the brain are affected by abnormal neuronal discharges. They present with a loss of consciousness, and body-wide muscle rigidity (tonic phase), and are followed by rhythmic convulsions (clonic phase) [4]. A deviated gaze and incontinence are also common signs of a tonic-clonic seizure.
Seizures can affect both respiration and upper airway protection. Patients may stop breathing at the beginning of a convulsive seizure as muscles contract [4]. Generalized seizures then cause a catecholamine surge and increased metabolic rate, which increases cerebral oxygen demand and strains the cardiovascular system [3,4].
The gag reflex is also suppressed during a seizure and the patient may aspirate if they vomit. The patient’s upper airway may also be obstructed by their relaxed tongue.
Generalized tonic-clonic seizures usually last a few seconds to a few minutes. Afterward, there is often a postictal phase, during which patients have an altered mental status before returning to full alertness.
As seizures are usually of short duration, patients are most often in the postictal phase when EMS arrives [4]. Patients may be unconscious or only respond to painful stimuli during the postictal phase. The patient is likely to have respiratory depression and diminished airway reflexes [4].
Postictal patients may also be confused or combative, especially as they transition from somnolent to awake. The postictal phase may last a few minutes to several hours, but patients usually fully recover after 20 minutes. If a patient remains confused for longer than 20 minutes after a seizure, consider another cause of altered mental status [4].
A seizure that lasts more than 20 minutes, or recurs before a patient regains consciousness, is a life-threatening condition known as status epilepticus [1]. This may lead to brain damage, hypoxia, hypercapnia, pulmonary edema, hypoglycemia, and metabolic acidosis [4].
It is important to determine the duration of seizures, how many seizures the patient had, what the patient was doing before the seizure and whether or not the patient regained consciousness after each seizure to identify status epilepticus.
Epilepsy is the most common cause of seizures, particularly when patients are not compliant with prescribed anticonvulsants. Seizures can also be caused by hypoxia, head injury, stroke, hypoglycemia, brain tumor, poisoning, meningitis and fever [4].
It is important to identify and treat the underlying cause of seizures and to never assume that one was caused by epilepsy. Ask bystanders and look for a medical identification bracelet to determine if the patient has a history of seizures.
Ask if the patient was complaining of anything before the seizure began, if they struck their head or if they may have overdosed. Check blood glucose on any suspected seizure patient to assess for hypoglycemia.
Two other types of seizures are absence and partial seizures. An absence seizure is a type of generalized seizure that usually occurs in children, which causes a temporary loss of awareness that may only last for a few seconds. Patients are unable to communicate during the episode and there is no postictal phase afterwards [4].
Partial seizures affect only part of the brain and patients usually remain conscious during the episode. They may report an odd feeling or you might see a shaking of one limb. Partial seizures can progress to generalized tonic-clonic seizure, which are known as complex partial seizures [4].
2. Waveform capnography can help guide airway management during and after seizures
Airway management for a patient having a seizure involves protecting the upper airway, administering high-flow oxygen and assisting ventilation if needed [4]. Waveform capnography provides continuous feedback on upper airway patency and ventilation, which can help determine what treatment is needed to achieve those goals.
Capnography measures the amount of carbon dioxide exhaled (end-tidal CO2, or ETCO2) after each breath. Normal ETCO2 is 35 to 45 mm HG. Capnography also displays a waveform for each breath and continuously measures the patient’s respiratory rate. ETCO2 can be measured with nasal prongs or a circuit connected to a bag-valve mask.
Elevated ETCO2 with a normal respiratory rate may be caused by an increase in basal metabolic rate. Elevated ETCO2 with a slow respiratory rate indicates hypoventilation, as excess CO2 accumulates in the lungs and is not excreted effectively. Hypoventilation may also cause low ETCO2 if respirations are shallow and little exhaled air reaches the sensor or if the patient exhales excess CO2.
Pulse oximetry measures oxygenation through a probe attached to a finger, toe or earlobe. Pulse oximetry may be difficult to obtain during a tonic-clonic seizure, so look for cyanotic skin as another sign of hypoxia. Remember that patients may be adequately oxygenated and have a normal pulse oximetry reading, but still be hypoventilating and have an abnormal ETCO2.
Administer oxygen via non-rebreather mask at 12-15 liters per minute to any patient who is actively seizing or is postictal, regardless of their pulse-ox reading, to help with the increased metabolic demands of the brain for oxygen [4]. Patients who are hypoventilating during a seizure, remain hypoxic despite high-flow oxygen or have poor respiratory effort require assisted ventilation with a bag-valve mask connected to oxygen.
Waveform capnography is also useful to assess upper airway patency. A waveform will be absent if the airway is obstructed by the tongue or oral secretions. A waveform will reappear if interventions work at achieving patency.
Start by positioning the patient on their side, suction the oropharynx and insert a nasal airway to clear a path for oxygenation and ventilation. Do not place anything in a seizure patient’s mouth.
3. Definitive airway management for seizures is stopping the seizure
As important as oxygenation and ventilation are during a seizure, it is equally important to stop the seizure. Depending on resources available, airway management may have to be temporarily deferred in order to administer anti-seizure medication.
Assume that any patient who is actively seizing on EMS arrival is in status epilepticus, which can cause permanent brain damage even with adequate oxygenation and ventilation [3]. Seizures that last longer than 5 minutes are unlikely to stop without intervention and should be promptly treated with a benzodiazepine [3].
Benzodiazepines, such as Valium (diazepam), Ativan (lorazepam) or Versed (midazolam), are the first line treatment for seizures. The earlier a seizure is treated with a benzodiazepine, the more likely it is to terminate [3].
While intravenous administration of a benzodiazepine is ideal, obtaining intravenous access can be difficult in a seizing patient, as well as time-consuming. Diazepam, lorazepam, and midazolam can all be administered intramuscularly.
A large trial showed that intramuscular midazolam terminated seizures faster than intravenous lorazepam [5]. Midazolam can also be administered intranasally, and diazepam can be administered rectally.
Depending on local protocols, it may be best to administer a benzodiazepine by intramuscular, intranasal or rectal route before attempting to obtain intravenous access. Whichever medication or route is used, use a reference or cross-check process to ensure that the correct dose is administered. The few extra seconds to perform a medication cross-check is well worth the added layer of patient safety.
Repeated doses of benzodiazepines may be needed to terminate seizures, and they should be administered until all seizure activity has ceased. Seizure activity may still be taking place in the brain, even if generalized convulsions have stopped. A deviated gaze, irregular respiratory pattern and occasional muscle contractions are all signs that the patient is still seizing and requires more medication.
Respiratory depression is a side effect of benzodiazepines, which can be detected immediately when monitoring waveform capnography. Assist ventilation with a bag-valve mask if respiratory depression occurs, and titrate respiratory rate and tidal volume to maintain ETCO2 between 35 and 45 mm Hg.
Generalized seizures can cause many forms of respiratory compromise, including respiratory arrest, respiratory depression and loss of upper airway reflexes. Waveform capnography is a reliable tool to help detect respiratory compromise, make airway management decisions and provide feedback on how well airway interventions are working.
References
1. Michael G, O’Connor R. The diagnosis and management of seizures and status epilepticus in the prehospital setting. Emerg Med Clin N Am (2011) 29; 29-39.
2. Myers JB, Slovis CM, Eckstein M, et al. Evidence based performance measures for emergency medical services systems: a model for expanded EMS benchmarking. Prehosp Emerg Care, 2008; 12: 141–51.
3. Pillow M, Howes, D, O’connor, R et al. Seizure assessment in the emergency department. Medscape 2015, Jan 8. Retrieved from: http://emedicine.medscape.com/article/1609294-overview
4. EMS Training: Epilepsy and Seizure Management. Epilepsy Foundation, 2011.
5. Silbegleit R, Durkalski V, Lowenstein D, et al. Intramuscular versus intravenous therapy for prehospital status epilepticus. N Engl J Med. 2012; 366(7):591-600
This article, originally published in June 2016, has been updated.
