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CHAPTER 15 Altered mental status
Mariecely Luciano‐Feijoó and Jefferson G. Williams
Introduction
The patient presenting with altered mental status (AMS), or altered level of consciousness, is a common encounter for EMS. AMS is not a disease, but rather a possible symptom of many conditions, and the differential diagnosis can be extensive [1]. Many etiologies of AMS have the potential to cause significant morbidity and mortality. It is essential that proper care be initiated in the field, along with early consideration of a broad differential diagnosis. Often, treatment must begin before the etiology of AMS is confirmed. In most instances, this treatment should be instituted in conjunction with attempts to determine the underlying cause. The main challenge of a prehospital patient with undifferentiated AMS is to rapidly identify and treat life‐threatening or potentially reversible problems in the field in order to prevent added morbidity from the complications of a prolonged condition.
Assessing mental status
Altered mental status can be defined as a change in a person’s level of consciousness or cognitive function [2]. Whether these changes occur over time or suddenly, disruption in normal brain function can cause a change in usual behavior that may not be noticeable to the patient (him or herself) but is often noticeable to others and a cause for concern. Friends, family members, or bystanders may then summon EMS.
AMS encompasses a collection of more specific neurologic problems. For example, a patient with AMS may have a change in consciousness, which is described as having two major components: arousal and content. A patient with a change in arousal (level of alertness) may range from unresponsive (comatose) to hyperalert and unable to focus on the examiner. On the other hand, a patient with a change in the content of his consciousness may have a normal level of alertness but may have a change in brain function that causes an inability to interact with his environment (e.g., an inability to interpret or form language) [2].
Assessing mental status is about determining what specific behaviors or actions (or lack thereof) of a patient are abnormal or different from that patient’s usual baseline brain function. The assessment should consider what deficits are present (i.e., alteration in alertness, content, or both) and the timing of those deficits. For example, two common states of altered mental status are delirium and dementia. Delirium is distinguished by its acute onset, and patients may wax and wane in level of arousal, attentiveness, and cognition. Dementia is characterized by a more gradual onset of diminished cognition with normal level of arousal and often decreased orientation.
Assessment of the AMS patient may be challenging due to the breadth of abnormalities that the term encompasses and because the AMS patient is impaired in his or her ability to participate in the history and exam. Common medical terms used to describe AMS, such as stuporous, obtunded, or confused may hold different meaning for different medical professionals. For this reason, they are best avoided. Family or bystanders may also describe vague symptoms, such as “he’s just not acting right,” or nonspecific concerns. Nonetheless, the EMS clinician can develop an effective differential diagnosis and treatment plan by determining a patient’s specific deficits and gaining an understanding of timing and specific possible causes via a thorough history and exam.
Approach to the patient with AMS
Once scene safety is assured, EMS personnel of all levels should assess the ABCs, check vital signs, and immediately address life‐threatening conditions. Appropriate basic life support measures, such as basic airway management and respiratory support, should be instituted before any attempt is made to gather a complete history or perform a detailed physical examination. Once the ABCs are adequately addressed, additional history, physical examination, and field findings should prove useful for developing an appropriate differential diagnosis and treatment plan.
Airway, ventilation, and oxygenation
For the majority of AMS patients, the first priority is to establish and maintain an adequate airway. A patient who is unresponsive may not be able to protect his or her airway, and an obstructed airway may be contributing to altered mental status. Evaluate whether the patient can protect his or her airway; whether there is a need for suction, or repositioning, or removal of a physical obstruction; and whether airway adjuncts or advanced airway placement is necessary. A nasopharyngeal or oropharyngeal airway, if tolerated, may be a helpful adjunct to maintain airway patency. If no contraindication exists (particularly the need for spinal precautions), the lateral decubitus position may be advantageous for airway protection in many AMS patients (see Chapters 2, 3, and 4).
Once the airway is patent, assess breathing adequacy. If the patient is apneic or hypoventilating, respirations should be immediately assisted using a bag‐valve mask. Advanced airway placement for longer‐term ventilation may be considered if bag‐valve‐mask ventilation is not effective, but the majority of patients can be initially managed with airway adjuncts, enough hands, and basic maneuvers.
Hypoxia may also be a cause or an effect of altered mental status. Assessment of respiratory rate and depth, as well as pulse oximetry, can assist the EMS clinician in determining if there is a need to improve the patient’s oxygenation. Supplemental oxygen via nonrebreather mask may be the most appropriate initial therapy for a hypoxic patient with adequate respiratory drive and tidal volume while other vital signs are being assessed, but positive‐pressure ventilation with supplemental oxygen may be required for the hypoxic patient with shallow or otherwise ineffective respiratory effort.
Noninvasive positive‐pressure ventilation (NIPPV, e.g., CPAP or BiPAP) may be of special assistance in the patient who is hypercapneic and/or hypoxic as a cause of AMS. NIPPV may improve ventilation, gas exchange, and CO2 removal, and therefore treat AMS. However, choice of this therapy is predicated upon the patient being able to protect his or her airway, have an adequate respiratory drive, and have a mental status capable of tolerating the mask and clinician instructions. Attempting NIPPV in a patient with AMS mandates meticulous ongoing attention to the patient to evaluate for improvement or decline in mental status and vital signs. As an additional assessment parameter, waveform end‐tidal CO2 monitoring can assist the EMS clinician in both diagnosing and managing the patient with elevated pCO2. Should the patient decline while being treated with NIPPV, or mental status worsen such that the patient cannot cooperate with the therapy or protect his or her airway, manual supportive airway measures such as a bag‐valve‐mask with advanced airway placement will be required to facilitate positive‐pressure ventilation.
Other vital signs
Once the airway is secured and appropriate oxygenation and ventilation are established, the