It’s quite simple really. All you have to do is inject 3 cc of air directly into the right atrium of your unsuspecting experimental animal. Yep. It’s as simple as that. And how to do that short of wielding an air-filled syringe and stabbing it directly into the sweet spot?
The handy-dandy device pictured here is a stopcock. It’s used as a valve to allow one catheter to be connected to more than one thing. We use many stopcocks in my study—on the arterial line to allow connection to the blood-pressure-heart-rate-machine-thing with an extra port for blood draws, on the venous line to allow connection to the central-venous-pressure-machine-thing with an extra port for infusion of valium for sedation, and another stopcock on the same venous line to allow saline injection for measurement of cardiac output with the other port used for blood draws. And that’s not even the half of them apparently.
We measure cardiac output using the thermodilution method in which cold saline is injected into the right atrium and the change in temperature measured. I’ve run this measurement many times before in all of my previous failed (for other reasons) experiments. I always double and triple check all of the stopcocks before injecting saline. And I did no different today before starting my measurements.
Here’s what I was thinking as I was taking my readings:
Okay. First reading: 1322 ml/min. That’s a little high (but in the realm of normal for this animal). Let’s run another one…
Uh. Why is there only a flat line tracing (as opposed to the usual curve) and no reading? Well, not to fear. This has also happened before (or maybe not…what I meant was that the cardiac output machine has done funky things before). Let’s just run it again.
Still a flat line.
Hmm…why is the respiratory-machine-thing alarming? Well, that also happens a lot because this animal likes to breathe against the ventilator and the normals are set at human values.
Let’s just hit that “silence alarm†button.
Hmm…why does it say “apnea (which means that breathing has stopped)?†That’s a little odd. But that’s also happened before—when someone stepped on the line connecting the animal to the respiratory-machine-thing. [looks to see if someone is stepping on line] No one’s stepping on the line.
Crap. Are my lack of cardiac output reading and this apnea related? The apnea did seem to start right after that second attempt at a cardiac output reading. Can’t be, because that means I did something wrong and I triple checked all the stopcocks and I flushed out the saline injection line before using it…
At this point, Collaborator-doctor-man finally notices that there just might be a real problem (the alarms go off a lot in our experiments—we’ve become quite adept at hitting that “silence alarm†button). He glances over at the cardiac output machine setup and notices the problem: the stopcock attached to the very end of the saline bag was in the closed position. Which means that no saline was being drawn into the injector-thing. Which means that the injector-thing was injecting AIR instead of saline into the animal when I tried to take my cardiac output readings. Which means I gave the animal an air embolus that probably went straight to its lungs. Which was why it was apneic. Which means that I so just ruined my entire experiment by killing the animal.
The irony. We’re always so careful to flush out every single line with plenty of saline and to check our syringes twice to avoid little tiny air bubbles because the animal we work with is quite sensitive to air emboli. And here I am, injecting not a little tiny bubble or even two, but 3 whole cc of air into the poor animal. All because some weirdo decided to put a stopcock at the end of that saline bag. Who would do such a thing anyway? Leaving it in the closed position no less? It’s almost as if my major professor snuck in when our backs were turned and sabotaged me just so that he can torture me a little longer. I wouldn’t put it past him. Well, I learned my lesson here. Stopcocks are not my friends.
Related posts:
- air embolus: 2, me: 0Oh, the irony. My experiments were going so well (only because I changed models). I guess I was ripe for a failure. But why did it have to be by air embolus again? Last time, it was the stopcock of doom. This time, it was our Swan-Ganz catheter. It's inserted into the heart and pulmonary artery to read pulmonary artery and pulmonary artery wedge pressures as well as cardiac outputs. To be able to get to where it needs to be, there's a tiny inflatable balloon at the end that makes it easier for the catheter to be caught by blood flow that takes it into the right ventricle. Well, our little inflatable balloon got a hole in it so that every time we injected it to fill it up with air, we were actually pumping our animal up with many tiny deadly air bubbles. The thing is, we didn't even know we had a problem until I did some bloodwork and got a venous oxygen saturation of 16% (normal is anywhere between 60 and 100 in my particular animal and the lowest I've seen it during our shock state is probably 50%). So yeah. Fun....
- these experiments may not be a complete loss after allMaybe I've been inhaling too much waste isoflurane the last couple of days, but I seem to be deluding myself into believing that these failed experiments of mine are actually useful in the most minute way. You see, I prepare all of the monitors, IVs, and catheters for these experiments, which has taught me how to do such things and what to check when I'm trying to explain an anomalous reading. Not only that, but I've gotten plenty of experience with reading pressure curves to guide the placement of a Swan-Ganz catheter. I also know what to watch out for when an animal is under anesthesia. But most importantly, I've learned how to not freak out and freeze when something goes wrong. Not so long ago, I accidentally pulled a stopcock out on a pressure line and froze, letting blood ooze out from the line onto the ground until the surgeon fixed it for me. Yesterday, I forgot to close a stopcock and blood started oozing back precipitously into the line. But instead of panicking and freezing, I traced the problem to the stopcock and closed it myself, leaving no one the wiser. And today, as I was helping the surgeon introduce a catheter into the external jugular vein, he turned away and the catheter popped out, resulting in a nice stream of blood shooting straight out (surprising considering it was a vein). While he freaked out for a second, I merely pulled back on the ties around the vessel...
- if you want to finish grad school in a decent amount of time…Do NOT work with animal models. Animals are highly variable. You'll get inconsistent results. Or no results. Or results that don't make sense. If all I had to do was run gels to get my PhD, I would be done by now. But, no, I'm working with animals. And I spoke too soon last week when I thought I saw the light at the end of the tunnel. Because now my experiments aren't working even though I'm doing the same thing that worked just last week. And I'm so tired from being on my feet all day. And dealing with cardiac arrest and resuscitation. All to have it not work out anyway. I think I'm going to go cry myself to sleep now....
Related posts brought to you by Yet Another Related Posts Plugin.
0 Response to “how to really quickly irreversibly ruin your experiment”