Driver Down!

     It's already been a busy Friday evening when Attack One responds to a report of a "person down in a car." Passersby called 9-1-1 upon finding the man unconscious at the wheel of a car at a downtown intersection. Police arrived to find a man about 50 years of age, unresponsive, and opened the car door. They suspect he is intoxicated.

     The man, dressed in a set of work overalls, is unresponsive to painful stimuli. His skin is warm, but a pulse is not palpable at his wrist--in fact, the pulse oximeter does not even detect a pulse. Crew members smell no intoxicating beverages or any other distinctive smells. The man's pupils are midsize and react slowly.

     What is this?

     The man is unresponsive and apparently in shock. He has warm skin and reactive pupils, and is not diaphoretic. Stroking the bottoms of his feet produces a curling reaction in his toes. What would produce this type of clinical picture?

     The crew reassures the police that this does not appear to be an intoxication problem. They ask the officers for assistance in identifying the patient, contacting his relatives and securing the car. They need to expedite transport.

     There's still no response as the man is removed from the car, but he moans occasionally. He almost looks flushed. The crew ponders shock, without diaphoresis, with midsize pupils and an intact spinal cord. His skin is warm, but not so hot that the crew suspects him to be febrile. In the medic, there's no blood pressure detectable, and his skin is beginning to feel cold.

     Carbon monoxide poisoning could produce this profoundly altered level of consciousness. There's a carbon monoxide monitor available on Attack One, but the CO level in the automobile is found to be zero.

     Anaphylaxis? There are no obvious sting sites, but that's a clinical impression consistent with all his symptoms. A three-lead ECG reveals sinus tachycardia, with no obvious ST segment elevation (a very crude marker of acute MI in some patients). Whatever is going on, his perfusion is poor and getting worse. The crew initiates a large-bore IV (with no response from the patient), bolusing a liter of normal saline. The patient still looks poor, so they follow with an IV dose of diphenhydramine and subcutaneous epinephrine in the arm. The ED is contacted, and, given the paramedic's insistence that this appears to be a case of anaphylaxis, the emergency physician agrees to the medication protocol for anaphylactic shock.

     The Attack One crew administers a liter of saline prior to arrival in the ED. The patient remains unresponsive, and his pulse rate increases while his pulse oximeter probe cannot detect a readable signal.

Hospital Course
     As he enters the ED, the patient appears near death. His skin is ashen, he's still unresponsive, and his pulse rate has reached almost 140 despite the fluid and medications. He is breathing spontaneously with supplemental oxygen; his neck veins are flat, his lungs clear and his abdomen soft. The patient is assessed by the emergency physician, with the paramedic repeating the story about the initial appearance of skin flushing. That is not, however, the appearance of the patient now--his skin has grown cold and pale. If this is a severe anaphylactic reaction, the subcutaneous epinephrine isn't going to work with the skin's perfusion so compromised. Intravenous epinephrine will need to be administered through the line placed before the patient's cardiovascular collapse.

     The ED nurses prepare a solution of diluted epinephrine, and a small amount is administered to the patient. It produces no reaction, so a second dose is given. Almost immediately, the patient's skin begins to warm and colorize, and then he opens his eyes. In a scene that reminds the entire staff of a patient waking up from a hypoglycemic insulin reaction, the man asks where he is and what happened. After a few minutes, he asks to sit up and remove the oxygen mask.

     The patient temporarily develops a mild tremor, and his pulse remains about 120 bpm (his vascular system is now reacting to the epinephrine injected in his skin), but his other clinical problems resolve. The Attack One medics and ED staff quiz him regarding his past history and what may have caused his reaction.

     He says he's a healthy individual, on no medication and with no history of allergies. He had eaten a normal dinner around 1900 hours, then watched TV and got dressed for work. His night-shift position at the local newspaper started at 2300 hours, and he remembers driving to work, planning to arrive five minutes early. He was found about two blocks from his work site. He can only remember one new-product exposure, and that was a new shaving cream.

     Further inquiries reveal no other potential causes for the incident, and the patient is now feeling well and asking for food. He is getting up to urinate when his wife enters the ED with the police officers who had gone to pick her up. As she sees him up walking and talking, she expresses her gratitude, then asks, "Honey, did you tell them about taking one of my penicillin pills before you left for work?"

     All the puzzle pieces fall together.

Case Discussion
     The causes of profound shock must be related to the severe malfunction of the body's pump (the heart), distribution system (the arteries and veins) or control system (the brain and spinal cord). We often refer to these respective causes of shock as cardiogenic, distributive and neurogenic. Cardiogenic shock often manifests to the EMT with a patient who complains of chest pain, shortness of breath and fluid overload and has some history of heart disease. On examination, this patient often has diaphoretic skin, distended neck veins and rales in the lungs. Neurogenic shock presents with some history of trauma and signs of complete disruption of the spine. Distributive shock can be caused by sepsis, substances or severe allergic reactions. This patient was evaluated for all three, and the astute paramedic noted the early flushing of the skin. Septic patients often have a noticeable smell, and may have a fever that is palpable even through an EMT's gloves. The medic looked for a bee sting, which could have presented in an identical fashion. There was a search for other substances like carbon monoxide, but none were apparent.

     When the patient failed to respond to a fluid bolus, oxygen and diphenhydramine, subcutaneous epinephrine was administered. At about the same time, the patient's skin stopped perfusing; hence that dose of medicine was not absorbed. The worsening clinical state then forced providers to consider other methods to deliver epinephrine to the heart and blood vessels.

     Epinephrine is one of the medications that can be delivered by the widest number of routes. It is effective when administered intravenously, intramuscularly, on the tongue, into the bone marrow or down an endotracheal tube. This patient's worsening clinical state made intravenous the route of choice, and the emergency physician chose to dilute the dose to prevent side effects. Epinephrine is an extremely potent IV medication--and one that would produce profound skin damage if it accidentally leaked from the vein--so small doses must be used. Diluting the standard intravenous preparation of 1:10,000 by mixing one milliliter with 10 milliliters of saline produces an appropriate dose for administering 1–2 milliliters at a time through a good IV line. Like many other potent medications (Narcan, dopamine, atropine), the dosage of intravenous epinephrine should be just enough to produce the desired clinical effect in the patient. In this case, one milliliter of the diluted epinephrine, or one-tenth of a milligram of the drug, restored vascular tone, reversed the shock and woke the patient up.

     In North America, the most common substances causing profound anaphylaxis outside the hospital are bee venom, penicillin, nuts and shellfish. This patient was not able to give any information to the crew on initial assessment, and it required some investigative work to identify the cause of his reaction. Were it not for his wife arriving at the emergency department, the cause of this patient's near-death experience would have been unknown. Specifically asking for these four allergens in the patient's history can locate the source of the problem in the vast majority of these patients. This is critically important for prevention of future reactions.

     The prehospital provider must know the causes of profound shock that intersect with patients having severely altered levels of consciousness. Persons with this combination of problems require a quick and complete history and examination, and rapid movement to the hospital. Timely communication between the EMT and emergency physician is integral to complete evaluation of the patient and the best possible outcome.