Rules of the Trade

By Tony Dajer|Wednesday, December 01, 1993
The first rule is, Trust no one.

The fourth-year surgery resident threw two lanky arms behind his head and leaned far back in his swivel chair. I stood before him on the morning of the first day of my very first clinical rotation, in my fresh white jacket, bristling with ophthalmoscope, otoscope, reflex hammer, and stethoscope--armed and, in my new boss’s likely opinion, very dangerous. From that moment on, he would be instantly liable for every mistake I made. He squinted at me with eyes vaguely amused but as focused as cross hairs.

The next two rules are, Do it yourself and No excuses, he continued, letting his southern accent slip in for effect the way airline pilots do. Those are easy. Trust no one is the big one. Just because someone tells you something, even if they’re the chief of surgery--hell, even if they’re me--doesn’t mean you should go off and believe them. Make your own damn diagnoses. Question your own grandmother. Twice. And then maybe, just maybe, you won’t kill too many patients.

In the dozen years since then, it seems I’ve been hit over the head again and again by the wisdom drawled out to me by that very smart surgery resident. And no matter how many times it happens, it always takes me by surprise.

Cardiac arrest! ETA two minutes.

The emergency room had been quieting down after a day of about average mayhem when the call came over the code phone, our direct link with the ambulances.

Doctors and nurses pushed themselves back onto their feet. Within seconds a half-dozen white-clad bodies had coalesced around the resuscitation slot. Intravenous bags were hung; the crash cart, piled high with the intubation equipment, defibrillators, and drugs we might need, was wheeled into place; the intubation tubes--plastic breathing tubes we might have to insert into the patient’s windpipe--were laid out. I glanced over at Lynn, the other attending physician.

I’ll intubate if you run the heart equipment, I said.

Sure, she smiled. You always go for the strong-arm stuff.

As I tried to think of a good comeback, the emergency room doors burst open. We stepped back. Blue uniforms and a stretcher whizzed past. Arms flew. Words shot out like bursts of Morse code.

Rate 40.

Eighteen-gauge left antecubital.

Respiratory rate?

Twelve-lead ECG, please.

In all the tumult, through the forest of backs, what first caught my eye was the patient’s left hand. Where I’d expected the pasty, bloodless digits of a cardiac arrest victim, I saw five well-manicured fingers, two diamond rings set off by a golden tan, and a delicate, half-turned wrist extending from under a sheet.

What the heck is she doing here? I wondered aloud. After all, young women aren’t supposed to have cardiac arrests.

I squeezed through the crowd to the head of the stretcher, since it was my job to intubate if necessary. But instead of a patient in extremis, I found an attractive woman of about 40 avidly following the conversation between Lynn and a bow-tied gentleman.

Lynn caught my eye, then shrugged as if to say, Beats me. She turned back to the bow tie.

So you’re Mrs. Petty’s doctor?

That’s right, the man answered.

And what exactly happened today?

A younger man stepped forward. I can answer that.

Okay, and who are you? Lynn asked.

Mr. Petty.

Great. So please tell us.

Mr. Petty wore a checked shirt, open at the collar. His black hair looked a bit mussed. He leaned toward Lynn with the harried expression of a traveler whose flight has just been canceled.

Look, he began. My wife has a history of low potassium. She’s been vomiting and has had diarrhea for two days now. She can’t keep her potassium supplements down. We’ve been through this before and I know what she needs. And that’s potassium. IV. Now.

The doctor piped up: I checked her level two days ago. It was 2.8. Very low.

Thanks, doctor, that’s certainly helpful, Lynn answered, her voice neutral.

A normal blood potassium level is 3.5 to 5.0 milliequivalents per liter of blood. (An equivalent is the amount of a substance that can combine with eight grams of oxygen or one gram of hydrogen.) Potassium is also found in large quantities in gastric fluids and stool; in Mrs. Petty’s case, with vomiting and diarrhea on top of already low levels, the obvious fear was that her potassium could be dropping to a lethal low.

Still, the story jarred. The same young, otherwise healthy women who aren’t supposed to have cardiac arrests also aren’t supposed to be walking around with low potassium. That’s why Lynn felt a little corroboration was in order.

So what’s caused Mrs. Petty’s low potassium? she asked.

Mr. Petty began to look visibly annoyed. Listen, she’s had every test known to medicine, he replied, with real heat in his voice. And no one knows. But her doctor is right here and he’s telling you that’s her diagnosis. What are you waiting for?

Lynn is one of the toughest doctors I know. Threatening her would normally buy you a speedy one-way ticket out of the emergency room, complete with a security guard escort. But the paramedics had told us that Mrs. Petty had already come close to coding--ER shorthand for a cardiac arrest--once. And Mr. Petty wasn’t budging. Since Mrs. Petty’s heart was possibly just minutes away from stopping, Lynn decided it wasn’t worth taking him on. She frowned, then turned to Eileen, the closest nurse.

Let’s mix 40 milliequivalents of potassium in each IV bag and make them run at a total of 30 an hour.

Thirty an hour? Eileen replied. She was one of the most experienced nurses in the emergency room. Isn’t ten per hour usually the limit?

Yup, Lynn said. But this isn’t a usual case.

Eileen pursed her lips. Whatever you say, Doc.

In five minutes the potassium was running into Mrs. Petty’s veins. Everyone relaxed.

Lynn walked over to the doctors’ counter and began writing out the chart. I joined her.

A bit insistent, wasn’t he? I nodded toward Mr. Petty.

Lynn looked up. Well, he was probably right. It sounds like they’ve been through a lot. Here, look at this.

She handed me Mrs. Petty’s electrocardiogram. Unlike the spikes we like to see, the first few heartbeat tracings looked scary. They were alarmingly wide and wandering. Then, further on, there came a run of near- normal ones. Oh, good, I thought. Then I froze. Something was very wrong here.

The electrocardiogram reflects the electrical activity in the upper and lower chambers of the heart. It records three things: the initial electric burst that makes the atria, or upper chambers, contract; the spread of the contraction to the ventricles, or lower chambers; and the recovery period when the heart is recharged, readying itself for the next contraction. That part of the tracing, called the T wave, should be a gentle hump.

But on Mrs. Petty’s ECG, the T wave was tall and peaked, like a bedouin’s tent being yanked up by its tip.

Lynn! I exclaimed. Look!

What? She put her pen down.

The T waves. Here. I jammed my finger into the paper. They’re peaked, not flat.

Lynn blinked, and both our brains slammed on the brakes.

Yeah, I said carefully, putting her thoughts into words, her potassium isn’t low. It’s high. Very high.

The heart, like every other muscle, works on electricity, on the movements of charged particles across membranes. But unlike the others, it has a built-in stimulator and self-contained circuitry. Cut all outside nerve connections to the heart and it keeps on beating (albeit without its usual speedups and slowdowns); do the same to a thigh muscle and it’s paralyzed forever. The heart does this through specialized pacemaker cells that spontaneously fire and then reset themselves, without any outside interference.

To fire, the pacemaker cells take advantage of their natural voltage. Eons ago, in a feat of microengineering, our one-celled ancestors developed a molecular damming system to harness the electrically charged ions dissolved in the seas around them. Today the cells in our heart are mainly concerned with two positively charged ions: potassium and sodium. In essence, the cell membrane employs infinitesimally small pumps to hoard potassium inside the cell and eject sodium from it. But because sodium is pumped out faster than potassium is pumped in, and because potassium tends to leak out of the cell anyway, the interior of the cell has less positive charge than the exterior--in other words, the inside has a negative charge relative to the outside. In the pacemaker cells, when this difference in voltage reaches a critical level, channels in the cell’s membrane pop open to let sodium rush in. The resulting dramatic shift in the cell’s voltage results in an electric current, which almost instantly spreads to the rest of the heart’s muscle cells. They contract in forceful symmetry, and the result is a heartbeat.

Maintaining the right potassium level is critical to the system. Normally the ratio of potassium concentration inside the cell to its concentration outside is about 30 to 1. Any change can cause trouble. If the blood level gets too low--as Mr. Petty and the bow-tied doctor thought had happened to Mrs. Petty--the ionic imbalance can actually build up beyond the critical level, and the pacemaker cell will freeze like a pistol cocked too far back. No pacemaker signal means no heartbeat. If the blood’s potassium level gets too high--as I now thought was happening to Mrs. Petty--the pacemaker cell can’t generate enough voltage to fire a full- bodied signal. The heartbeat will eventually peter out to a lethal standstill.

Since both extremes can lead to the same outcome--cardiac arrest- -the only way to tell if a patient’s potassium is too high or too low (short of measuring the blood level directly, which can take a while) is to look at the electrocardiogram. The difference can be found in the T wave, which is peaked when the potassium is high but not when it’s low. In all fairness, at these extremes the ECG is often so abnormal that it can be tricky for an emergency room doctor to pick out the telltale high or low signs; it can take an expert to correctly interpret a very abnormal ECG. And if you’re not a cardiologist and you have a husband and a doctor shouting in your ear that the potassium in fact is low, that they’d measured it only two days before, and that you’d better do as they say, trying to pick out the subtleties can be like trying to sift wheat from chaff in a sandstorm.

Lynn squinted at the ECG strip.

But they swear it was low--2.8--two days ago. So where did all the potassium come from?

Beats me, I answered helpfully. Maybe she didn’t throw up all her supplements. Maybe she didn’t lose so much from the vomiting and diarrhea. Who knows? But these T waves look peaked, and if her potassium is high and we give her more, we’re going to kill her.

I hate when that happens, Lynn said, wincing.

Listen, why don’t you stop the potassium, and I’ll run the blood up to the lab myself and make them run it stat.

Check, boss. Lynn sent me off with a rueful wave.

Ten minutes later I was back. Mrs. Petty’s potassium level was 8.0--double the normal level. Lynn snatched the slip out of my hand and rushed over to Mr. Petty and Dr. Bow Tie.

Good thing we stopped the potassium! she announced. It was high; sky-high, in fact.

They greeted her with frowns.

No way. It must be a lab error, the husband said through clenched teeth.

Not a chance, Lynn replied, trying to keep her cool. The ECG looks like the potassium’s high, too. It all fits.

She’s never been high before. Send another sample.

What? Lynn spluttered.

Send another sample or I won’t let you treat her, Mr. Petty repeated, not giving an inch.

Oh, for Christ’s sake . . . Lynn looked truly exasperated.

The patient herself, though conscious, remained silent. Her eyelashes fluttered but her clear blue eyes never left her husband’s face. It was clear that he was in charge here. For a crazy split second it felt as though we were dealing with a hostage situation. Our choice was clear: we could have the security guards eject our patient’s entourage, or we could repeat the blood level. Lynn threw up her hands and grabbed a syringe. She quickly filled another lab tube and handed it to me. I reenacted my sprint to the lab. The result was exactly the same: 8.0.

Lynn went back into the lion’s den. She came out shaking her head.

They’ve given up on the IVs, she said, but they won’t let me give her anything to bring the potassium down.

What do you mean, they won’t let you bring it down? I stammered.

Just what I said. They won’t let me give her insulin, glucose, or calcium to bring it down. They still don’t believe us.

In a way, I could understand their predicament. Mr. and Mrs. Petty had probably been through a lot of tests, been bounced around the medical system, and still didn’t have a good explanation of just what was going on. They and their doctor were confused by what was going on here, and reacted to that by assuming we were making some sort of mistake. But how many more times were we supposed to check the potassium level?

Listen, I pleaded with Lynn, I saw a cardiac arrest from high potassium about a year ago. We tried everything but we couldn’t get him back. I really don’t want to see another. How about if you give her some bicarbonate to treat her acidosis--the bicarb should also help bring down the potassium level.

High potassium levels do, in fact, lead to a higher acidity in the blood, which is called acidosis. In response to all the extra potassium, the cells attempt an exchange--they pump out extra hydrogen ions and, in return, take in potassium. The hydrogen ions make the blood more acidic, which can be dangerous. An alkali such as sodium bicarbonate soaks up the hydrogen ions. It also helps the cells in their mission because they can then safely pump out more hydrogen ions and take up even more potassium.

Our strategy worked; over the next hour Mrs. Petty’s heart rhythm stabilized, and we were able to admit her to the cardiac unit. Dr. Bow Tie was nowhere to be found. Mr. Petty insisted on poring over all the texts in our small library--looking, presumably, for proof of where we’d gone wrong- -but he just kept poring. His wife was going to be fine.

Just before the end of my shift, Lynn and I sat down for a quick cup of coffee.

You know, she smiled, I’m not much for conspiracy theories, but it makes you wonder what Hitchcock would have thought.

Hmm. I pushed my chin into my chest in poor imitation of the famous silhouette. Yes. Very interesting. Rich wife. Large insurance policy . . .

And the best part, she picked up, is you get the docs to do her in.

Which, I added, doubles your take.

Lynn suddenly leaned forward. We’re just kidding, right?

Right, I answered, then shook my head to rid it of the sudden, disturbing notion. I didn’t really think Mr. Petty was trying to kill his wife. I didn’t think Dr. Bow Tie was his accomplice. This had just been a difficult, confusing case, and they were just difficult, aggressive people who liked to be in control.

In any case, Lynn continued, Mr. Petty darn near proved the old adage about not being your own doctor.

And the first rule, I said.

The first rule?

Just something a good doctor taught me. A long time ago.
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