By Nicholas Miller
Altered mental status is a generalized term for any form of altered state of consciousness. Acute AMS is a clear indicator that something is wrong with the patient.
The causes of AMS are virtually unlimited; however, nearly all of those causes can be classified into four major problem categories — fuel, ignition, transport and exchange. Understanding these categories and how they cause AMS will aid the EMS practitioner in quickly identifying the root cause of the patient’s acute AMS.
The brain requires a tremendous amount of energy to function in its normal healthy state. The energy source for all cells, including those in the brain, is adenosine triphosphate (ATP). Think of ATP as a fully charged battery that rapidly goes dead when used. The body must constantly recharge ATP batteries to maintain all body functions. The body burns glucose to provide the energy needed to recharge adenosine diphosphate (ADP), dead batteries, into ATP charged batteries.
The body accomplishes this through a series of biochemical reactions including glycolysis, the Krebs cycle and the electron transfer chain. If all of these complicated reactions were oversimplified into one big reaction, the net result would look something very similar to a BioLite wood-burning camping stove, which is capable of charging a smartphone.
The BioLite wood burning camp stove camping stove uses fuel, oxygen and an ignition source to create the energy needed to recharge electronic equipment. Just as the stove burns wood to recharge electronic batteries, the body does the same thing to charge its ATP batteries to maintain healthy brain function.
Like the stove, the body also needs fuel, oxygen and an ignition source. In the camp stove model, the fuel is wood, the oxygen comes from the air and the ignition source is a match or electric spark. The combustion of the wood creates smoke and ashes. The heat released during combustion generates electricity, which is conducted to the batteries in the device.
In the case of the human body, the stove is the mitochondria in each cell. Sugar is the fuel, usually in the form of glucose. Oxygen comes from the air we breathe. Thiamine is the essential igniter required to start the fire. Glucose burns or is converted into waste products. Carbon Dioxide is the smoke and water is the ashes. The burning of sugar creates electrons that travel down the power cord of the electron transport chain to recharge ATP. The net result is that ATP is produced and these fully charged batteries keeps the brain and body functioning.
Remove any piece from the equation and a wood fire will not burn. The same is true for the body. Take away the sugar, oxygen or the ignition source and the body cannot create ATP. An electronic device can go several hours before its batteries are depleted. The brain however, can only go a few minutes before it succumbs to irreversible damage.
Acute altered mental status is often the first clinical sign that something has disrupted this perpetual recharging of ATP. The EMS provider needs to rapidly identify which part or parts of the process have been disrupted and provide immediate interventions to correct the situation. Here are the four areas to identify the root cause of acute AMS.
1. Fuel problem
Inadequate fuel is the easiest problem to identify and correct. The fuel is glucose, so a glucose level should be obtained. Normal glucose levels are 70-120 dg/mL. Levels below this indicate hypoglycemia. The treatment is glucose, either in the form of oral glucose or intravenous dextrose.
2. Ignition problem
The stove needs a spark to start the fire. Thiamine (vitamin B1) is the critical ignition source for the body. The body does not make thiamine on its own so it must get it from food. Malnourished patients, including chronic alcoholics, may not have adequate thiamine to burn glucose. This is why thiamine was once part a coma cocktail given to patients with acute AMS patients of unknown origin. Some EMS services require that thiamine be administered to a patient any time glucose is administered.
3. Transport problem
A stove will not load itself with wood or give itself oxygen. A person has to collect fuel and load it into the stove. They must also make sure there is adequate oxygenated air for the stove by fanning the flames. The body is no different.
The cardiovascular system transports oxygen and glucose to all the cells. The blood and blood vessels acts as a light rail system carrying the oxygen in special cars of hemoglobin, with the sugar riding alongside in cars of plasma. The heart supplies the power that moves all the cars around the track of vasculature.
Once the sugar arrives at its destination, it is able to enter the cell only if the gatekeeper insulin is present. Insulin unlocks the doors of the cell wall and lets sugar enter the mitochondria.
Waste products such as carbon dioxide and water are removed by the same transport system. Any disruption of this transport system — the fluid, pump or container — will result in AMS.
Hypovolemia and exsanguination, a fluid disruption, prevents oxygen from reaching target cells. Vital signs and skin turgor are critical assessments. Neurological assessments, such as the FAST stroke assessment, look for disruptions in cerebral blood flow, either from an aneurysm, traumatic injury or thrombolytic stroke. Use a rapid trauma assessment to identify traumatic causes of fluid loss. Stop fluid loss, if possible, and replace fluid appropriately to mitigate the disruption.
The heart is responsible for pumping the oxygen and glucose rich blood to the cells. Perform a 12-lead ECG on all acute AMS patients to rule out pump failure or disruption. Follow current AHA BLS and ACLS guidelines to treat cardiac issues.
The blood vessels that contain the blood have the ability to expand or constrict to meet hemodynamic needs. There are many types of injury and illness capable of disrupting the container.
A spinal cord injury can cause blood vessels to become instantly dilated, creating a relative hypovolemia. Vessels can also become leaky in the presence of histamine that is released during the inflammatory or healing processes. Sepsis and anaphylaxis can result in massive histamine release, causing fluids to shift from the intercellular and intravascular to the interstitial third space. This also results in significant hypovolemia. Patients will often require repeated 20 mL/kg boluses of isotonic fluids. If illness or sepsis is suspected, a lactate level should be obtained for faster identification.
4. Exchange problem
A stove must be able to let in adequate oxygen to burn fuel and have a way to release the smoke from the combustion process. If oxygen cannot get in the stove or smoke cannot get out, the fire goes out.
Likewise in the body, oxygen and carbon dioxide must be able to come in and out via the processes of ventilation and respiration. EMS practitioners must assess the patient for adequate gas exchange.
Assess for adequate airway and breathing to make sure oxygen can enter the body. Pulse oximetry can indicate whether there is enough oxygen reaching red blood cells. Lung sounds will indicate issues such as obstruction from fluid, mucus or bronchoconstriction.
Patient history is important to determine possible sources of obstruction or asphyxiation such as asthma, congestive heart failure, pneumonia or drowning. Other asphyxiants include organophosphates, cyanide and carbon monoxide. Treatment focuses on removing the obstruction and getting oxygen to the cells.
Waveform capnography, to measure end tidal carbon dioxide and identify inadequate ventilation, can indicate adequate cellular exchange and exhalation of carbon dioxide. For example, COPD patients have difficulty exhaling carbon dioxide. They have the classic pink puffer signs of pursed lips, pink skin and an expanded barrel chest. They also have elevated carbon dioxide levels and a shark fin waveform indicating bronchoconstriction. Bronchodilators and positive pressure ventilation, such as CPAP, BiPAP or via BVM, will aid in removal of excess carbon dioxide and improving adequate gas exchange.
Understanding how the body creates, processes and transports energy aid the EMS provider in quickly making a differential diagnosis of acute altered mental status and appropriately managing the cause.