Alden H. Harken, MD
and Brian C. George, MD
You are in the operating room, in the emergency room, or maybe on the floor. Somebody says “I can’t get a blood pressure.”
You look at the cardiac monitor and there is still electrical activity apparent.
1. List the 6 H’s and 6 T’s.
2. Assume that you cannot rule out tension pneumothorax as the cause. Where and how should you decompress it?
3. Assume that you cannot rule out cardiac tamponade as the cause. What are the landmarks you use to do a pericardiocentesis?
4. Assume that you cannot rule out hypovolemia as the cause. When would you decide to stop treatment of the patient?
PULSELESS ELECTRICAL ACTIVITY
1. Pulseless electrical activity (PEA) has multiple causes, which you should memorize. During an emergency is not the time to be consulting a reference card (see Table 32-1).
Table 32-1. The Causes of PEA, Organized as the 6 H’s and 6 T’s
Regardless of cause, it doesn’t make any difference whether the patient arrives in the emergency department (ED) with no blood pressure or whether your patient abruptly loses a blood pressure in the operating room—you start with the same “ABC” emergency protocol. You should automatically do the following:
• Begin bag mask ventilation and start the process of intubating the patient. If the patient is already intubated (eg, in the OR), check the tube.
• Check the monitor. While pulseless, PEA still implies a cardiac rhythm. If the rhythm strip displays ventricular fibrillation (VF), proceed directly to asynchronous cardioversion (see the Ventricular Tachydysrhythmia Chapter 29).
• Place 2 large-bore IVs and give some crystalloid.
From this point on, management diverges based on your index of suspicion for each of the possible causes. In general, however, if you cannot rule out a given possibility, then you should empirically treat before you’ve made the diagnosis—if you wait to be sure, you’ve waited too long.
Let’s continue the case for some of the more complex yet common scenarios.
2. In this scenario, let’s assume that your patient is a 70-year-old veteran with a 100-pack/year smoking history. He is undergoing a laparoscopic right colectomy for cancer. At the beginning of the case the anesthesiologist despairs of a peak inspiratory pressure of 45 mm Hg. The cancer is partially obstructing, so you decide to proceed anyway. Midway through the case, the patient loses his pressure. The monitor reveals a heart rate of 130. The tube looks OK. (With an open abdomen, you would feel the aorta in order to confirm hypotension.) You should give 500 mL of LR. Try to listen for breath sounds. Then insert a #18 needle directly up through the diaphragm (if the abdomen is open) or high in the midaxillary (not midclavicular) line. You don’t need to connect the needle to anything. Your patient is already on positive pressure ventilation so you cannot produce a pneumothorax. This patient has bought himself a chest tube on the side that produces a gratifying “whoosh” of air.
3. Let’s pretend you are stat paged to the cath lab where your cardiology colleagues have placed some stiff catheters into the right ventricle of a middle-aged man. The patient is under the sheets, and the only history you get is that the monitor reveals a heart rate of 120 and he abruptly lost his blood pressure. The cardiac silhouette has not gotten any bigger during fluoroscopy.
After ensuring that the patient’s airway is patent and that the patient is breathing (A and B), you should perform a pericardiocentesis. This is performed by inserting a long #18 (spinal) needle immediately below the xiphoid while aiming for the patient’s left shoulder. If you get air, pull back and try again a little more medially. (If you are in the OR and already in the abdomen, you may more easily access the pleural and pericardial spaces directly across the diaphragm.) If you obtain blood, remove about 20 mL and squirt some on the sheets. If the blood clots on the sheets, you are in the right ventricle. If the blood does not clot, it represents defibrinated blood that was in the pericardial space.
Removing only 20 mL should make a huge hemodynamic difference (see Figure 32-1). Conceptually, let’s take some impermissible physiological leaps: by removing 20 mL of pericardial fluid, you permit an additional 20 mL of ventricular end-diastolic filling. The augmented left ventricular end-diastolic volume (LVEDV) translates into 20 mL of additional stroke volume. An additional 20 mL SV × heart rate of 100 equals an increased cardiac output of 2 L! The good news is that you have helped your patient a lot. The bad news is your patient only needs to reaccumulate another 20 mL in order to get back into trouble.
Figure 32-1. The pressure in the pericardial space remains low with increasing volume until the elastic limits of the pericardium are attained, at which point the pressure soars (A). Note that only a 20 mL volume difference produces a big increase in pressure at the elastic limit. A chronic pericardial effusion (B), however, can stretch gradually, with negligible increase in pressure.
4. In this scenario, let’s pretend that the patient is a young, healthy-appearing biker who has rolled his bike at high speed on the interstate. Your crack paramedic team rings down: “No vitals in the field” on arrival in the ED. There is a big diagnostic fork in the road.
Fork A: The nurses slap on EKG leads, indicating a sinus tachycardia of 140 and no BP (PEA). On fast exam there is minimal or no ventricular motion. You should “call the code.” A massive amount of epidemiological data confirms negligible “walkout of the hospital” survival following “blunt trauma with no vitals in the field.”
Fork B: The fast exam reveals vigorous ventricular contractility and a belly full of blood. You should activate the massive transfusion protocol on the way to the operating room.
TIPS TO REMEMBER
When you are stat paged, your destination determines your differential diagnosis. The most likely problems differ when you are called to the ED, the OR, the cath lab, or the dialysis unit.
The three most common causes of PEA are hypovolemia, tension pneumothorax, and cardiac tamponade. All three respond to volume.
The diagnosis of tamponade is not made by x-ray or ultrasound. Tamponade is not an “imaging” diagnosis.
A “pericardial effusion” becomes “pericardial tamponade” when the patient can no longer compensate in order to maintain ventricular filling. Eventually such patients go into PEA arrest.
Similarly, a “spontaneous pneumothorax” becomes a “tension pneumothorax” when the patient can no longer compensate, venous return falls, and once again the patient cannot maintain ventricular filling.
1. You are in the OR performing an open procedure when your patient goes into PEA arrest. The first thing you should do is which of the following?
A. Obtain a rhythm strip.
B. Decompress the bilateral chest through the diaphragm.
C. Obtain a CXR.
D. Check the ET tube position.
2. You are in the OR performing a laparoscopic procedure when your patient goes into PEA arrest. You decide to decompress the chest. You should place a #18 needle in which of the following positions?
A. In the midaxillary line above the nipples
B. In the midclavicular line as close to the clavicle as possible
C. Through the diaphragm
1. D. ABC—airway comes first.
2. A. The diaphragm can be surprisingly high when a patient is supine—and especially when the abdomen is insufflated for a laparoscopic procedure. Don’t place the needle in the midclavicular line as there is a risk of hitting the subclavian.