Asystole

Last call night, I had a very terrifying incident. At around 3am (when things happen around here), the resident and I had to put in a central line for one of our patients. A central line is an IV that goes into one of the larger vessels: the internal jugular vein in the neck, the subclavian vein under the collar bone, or the femoral vein in the groin. It is used to monitor the volume status of a patient and deliver certain medications that are toxic in peripheral intravenous lines.

The procedure, while standard and common, has its risks which include arterial cannulation (putting a needle in the artery instead of the vein as the two run together) and pneumothorax (putting a needle into the lung, causing it to collapse). We minimize that risk using ultrasound to see the vessels in the neck. The resident and I gowned up, prepped the neck, and began the procedure. After a few attempts, I was unable to cannulate the internal jugular vein (I think I'm too timid; up close, the needle looks huge). Although we visualized the anatomy by ultrasound, it was not easy.

Then the resident attempted the central line. After a try, she managed to get blood flow back. I was relieved, but when she unscrewed the syringe from the needle, pulsatile blood spurted back. It was not venous; it was arterial. We pulled out the needle and held pressure. Holding pressure for 10 minutes at 3:45AM feels like forever.

Suddenly, the monitor began to beep. We looked up, and I panicked. The heart rate was reading 30 beats per minute, and then it disappeared. She was asystolic; she had flatlined; her heart had, at least according to our monitors, stopped beating. In retrospect, the telemetry strip showed only a five second pause, but it felt like hours. In a classroom or on a test, I would know what to do, but here, I was stunned, petrified. But the resident responded in stride, asking for atropine, a drug to speed up the heart. She also figured out the cause of the asystole; by holding pressure, she was giving the patient "carotid massage." The carotid sinus contains baroreceptors that measure pressure; by pushing on the artery to tamponade bleeding, she had tricked the sinus to thinking the pressure was really high and the body responded by dropping the pressure and slowing the heart (parasympathetic response). This surge of hormones had slowed and possibly stopped the heart.

By releasing the pressure, the heart beat returned. The nurse had also given a bit of atropine as well. The patient ended up doing fine; there were no lasting complications beyond the arterial cannulation. But it taught me a good lesson, the anesthesia mantra that vigilance is necessary at all times.