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 next steps are to accurately measure and frequently reassess the patient’s other vital signs, including heart rate, blood pressure, and temperature. Abnormalities in these may indicate various shock states or cardiac dysrhythmias, which can certainly cause AMS. Identification of significant fever, environmental hyperthermia, or hypothermia, with associated AMS, should also lead to immediate treatment for these life‐threatening conditions. Many of the newest generation cardiac monitors also can measure carbon monoxide and methemoglobin levels via co‐oximetry, which can provide clues to the cause of AMS in the right clinical setting (e.g., a house fire with smoke inhalation). Should vital signs that are taken automatically using the cardiac monitor be incongruent with the rest of the clinical picture, they should be assessed manually (e.g., blood pressure measurement via a manual cuff) to ensure accuracy.
Physical exam
Regarding the remainder of the physical examination, the first task after addressing ABCs is to determine the type and degree of AMS. In general, it is best for the level of consciousness (arousal or alertness) to be described by the response that the patient makes to a given stimulus. EMS clinicians can use the simple mnemonic AVPU to classify their findings.
A = the patient is Alert
V = the patient responds only to loud Verbal stimuli
P = the patient responds only to Painful stimuli
U = the patient is Unconscious/Unresponsive
EMS clinicians may also use the Glasgow Coma Scale (GCS) (see Chapter 30). A study done with paramedics scoring videotaped patients with AMS confirmed that paramedics can determine GCS scores that correlate well with those of emergency physicians [3]. In addition, a directed and focused physical exam and secondary survey can aid in determining the cause of AMS:
Head
The head should be examined for any obvious signs of trauma, such as scalp and facial lacerations, abrasions, and contusions. The pupils should be observed for symmetry and light reactivity. If they demonstrate bilateral mydriasis, this may indicate cerebral hypoxia or a toxicological etiology (e.g., anticholinergics, sympathomimetics, selective serotonin reuptake inhibitors, etc.). Miosis is often due to opiate overdose. However, clonidine, antipsychotics, organophosphates, sedative‐hypnotics, and pontine stroke may also cause miosis. Unequal pupils may be found as a normal variant, but they could also indicate impending brain herniation from trauma or a spontaneous intracranial hemorrhage. Any odor on the patient’s breath should be noted, as some odors may provide clues to specific conditions that may benefit from early recognition and treatment. For example, acetone odor is associated with elevated serum ketones, which may indicate diabetic ketoacidosis. The smell of bitter almonds is associated with cyanide poisoning, which could benefit from hydroxocobalamin administration in the field.
Neck
Any upper airway stridor should be documented and plans to care for a partially or soon‐to‐be obstructed airway must take precedence. Should signs of possible acute trauma be found in a patient with AMS, the cervical spine should be evaluated for any step off, deformity, or penetrating trauma, and EMS personnel should maintain cervical spine precautions.
Chest
The respiratory rate, pattern, and depth should be noted. Auscultation can identify rhonchi, crackles, wheezing, or lack of breath sounds, which could aid in identifying infection, volume overload, asthma/COPD exacerbation, or pneumothorax as the cause of AMS due to decreased oxygen supply to the brain. Again, any outward signs of trauma should be identified.
Abdomen
The abdomen should be exposed and evaluated for any sign of blunt or penetrating trauma or distention. In females of child‐bearing age with gravid‐appearing abdomens, pregnancy and its complications (e.g., eclampsia, HELLP syndrome, and ectopic pregnancy) should be considered. After initial exposure and visualization,
