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, the next step is palpation of the abdomen to identify any rigidity or tenderness that could suggest intra‐abdominal conditions associated with AMS such as ascites, or perforated or ischemic bowel.
Neurological
In addition to pupillary findings, any focal neurologic signs suggesting stroke or increased intracranial pressure should be noted. An unresponsive patient with focal neurologic signs or concern for elevated intracranial pressure (e.g., Cushing’s triad of hypertension, bradycardia, and irregular respirations) are especially concerning and may need rapid transport to a specialty center. Seizures or seizure‐like activity also cause altered mental status. Signs of ongoing seizure (fixed gaze, tonic‐clonic movements) or post‐ictal state (AMS with evidence of loss of bowel or bladder tone, tongue trauma) should be noted. Family or friends may be able to validate that the patient’s speech is not normal, providing evidence of altered content of consciousness. EMS personnel should screen for stroke using an established stroke scale, such as the Cincinnati Prehospital Stroke Scale, Los Angeles Prehospital Stroke Screen, or Melbourne Ambulance Stroke Screen [4–6]. To further guide patient care, assessment with a stroke screen that considers large vessel occlusion, such as the Rapid Arterial Occlusion Evaluation (RACE) scale for stroke, or the Stroke Vision, Aphasia, Neglect assessment, should be used in patients with signs of stroke to assist with transport destination decision‐making [7, 8].
Skin
The skin may be used to estimate temperature, which may be increased in infection or heat illness and decreased in cold exposure, dehydration, or alcohol or barbiturate overdose. Rashes potentially indicating infection or allergic reaction should be noted. Track marks consistent with needle injections and drug overdose should be checked for. Signs of a previous suicide attempt, such as healed wrist scars, may be apparent. The undifferentiated patient should be log‐rolled and examined head to toe to observe for transdermal drug patches, insulin pumps, dialysis access, petechiae, occult puncture wounds, and other subtle findings.
Historical and environmental clues
As the situation permits, EMS personnel should systematically obtain from the scene as much information about the patient as possible. Because the patient often cannot provide an adequate history, EMS clinicians should seek additional information from alternative sources, such as bystanders, family, and physical surroundings. Important questions include the patient’s baseline health and past medical history, current prescribed medications, the rapidity of the onset of the symptoms, and any complaints voiced or signs exhibited by the patient. One particularly useful question is whether the patient ever had a complete loss of consciousness or seizure‐like activity.
EMS personnel should search common locations such as bathrooms, medicine cabinets, bedrooms, nightstands, and kitchens for clues about underlying illnesses or possible ingestions. A medical alert bracelet or necklace should be sought. Other household members with similar signs and symptoms, or the presence of multiple patients with AMS, or the presence of sick or deceased pets may point to a toxic environmental exposure such as carbon monoxide poisoning.
If a drug overdose or poisoning is suspected, EMS personnel should gather further pertinent information, including the route of exposure, the type of substance involved, and the time and amount of exposure. Empty pill containers, liquor bottles, syringes, and other drug paraphernalia can greatly facilitate later treatment decisions. In most cases, overdoses will occur by ingestion. If the exact amount of exposure or ingestion is not known, personnel should try to establish the maximum possible quantity. They should also note any actions taken by the patient or bystanders, including the administration of any “antidotes.”
Initial management
The focus of a care protocol for the patient with AMS is to secure the ABCs and rapidly identify and treat reversible conditions. Care for the AMS patient is largely supportive,