1 PE’s As usual, please remember that these articles are not meant to be the final word on anything – instead, they‟re supposed to represent the kind of information passed on by a preceptor to a new ICU nurse. When (not if) you find mistakes, let us know, and we‟ll fix them right away. In the meantime, make sure to check with your own references at all times! We decided to have some fun with images this time around – if this makes the file a little tricky to handle, let us know, and we‟ll take them out. 1- What is an embolus? 2- What is an embolism? 3- What is a pulmonary embolism? 4- What are the bad things that result physiology-wise from a PE? 5- What are the two relevant concepts of badness (COBs) involved in problems with the lungs? 6- What is the confusing thing about the two COBs? 7- So then which one is the problem that happens after a PE? 8- What other bad things happen to people with PEs? 9- What is a DVT? 10- Why do people get DVTs? 11- Is it really true that you can get DVTs and PEs if you sit too long on the plane? 12- What does smoking have to do with it? 13- What does taking birth control pills have to do with it? 14- What if the patient has a cast on? Preventing PEs 15- Can DVTs be prevented? 16- What are air boots all about? 17- What about compression stockings? 18- What is SQ heparin all about? 19- Should my patieng get sq heparin if she also has air boots on? 20- Should my patient get air boots if she is already getting sq heparin? 21- Can sq heparin be bad? 22- Can air boots be bad? 23- Can putting someone on a heparin drip be bad? 24- Can a patient develop a DVT anywhere besides a leg? 25- Can air boots prevent DVTs that happen, say, in my patient‟s arm? 26- Does it have to be two air boots? 27- What about those little air boots that just squeeze the feet? Detecting DVTs 28- How do I know if my patient has a DVT? 29- What is Homan‟s sign? 30- What is a venogram? 31- What are LENIs? 32- Should my patient have LENIs before getting air boots applied? 33- What does d-dimer have to do with it? 2 34- How do I know if my patient has a PE? 35- Can you see a PE on a chest x-ray? 36- What is a VQ scan? 37- What is a pulmonary angiogram? Kinds of PEs 38- Are there different kinds of PEs? 39- What is a saddle embolus? 40- Are there different kinds of emboluses? Treating PEs 41- How are PEs treated? 42- How long does a patient have to stay on heparin for a PE to dissolve? 43- What does TPA have to do with it? 44- How is a big PE or a saddle embolus treated? 45- What is clot lysis all about? 46- What does coumadin have to do with it? 47- What are IVC filters all about? Other Kinds of Embolisms 48- What is an air embolus? 49- What does a patient with an air embolus look like? 50- An incredibly important point involving rapid IV boluses. 51- What should I do if I think my patient has just pulled in an air embolus? 52- What is a fat embolus? 53- What is an amniotic fluid embolus? Embolisms 1- What is an embolus? Um, it looks like your patient is about to get an Mbolus! M 3 2- What is an embolism? You just don‟t want to have things floating along in the bloodstream that aren‟t supposed to be there. Just not a nice thing – clots are the one you always think of, but anything that hangs together and moves along will do it: a big air bubble maybe, or a hunk of fat, or maybe a big blob of amniotic fluid, moving along the vessel… anything capable of holding its shape and plugging up the vessel, whether on the right side or the left. Meaning, on the venous side, or the…what? http://www.stanford.edu/group/neurology/stroke/images/embolic.jpeg 3- What is a pulmonary embolism? Clots, usually, and most often from the big veins in the upper legs. These guys break loose, float downstream through the venous system and end up making their way through the right side of the heart to - where? Apparently nasty PE events coming from the calves are much less frequent. Emboli can also develop in the arms, and around central line catheters. Question for the group: suppose your patient came in with a black big toe from an embolus. Where would that one have come from? 4- What are the bad things that result physiology- wise from a PE? Couple of things: - There‟s a loss of blood flow through part of the lung. Blood stops flowing through whatever part of the lung is normally perfused by the vessel that gets plugged by the embolus. This can produce a pulmonary infarct. If the PE is big enough, blood flow through the lungs will be obstructed so much that relatively little will make it through to the left side of the heart, producing what amounts to hypovolemic hypotension. - There‟s a loss of some gas-exchange in the affected part of the lung, because the little capillaries in the alveoli aren‟t being perfused. The air goes in and out just fine, but the capillaries aren‟t working. - So the air going in and out doesn‟t match up with the blood flow that‟s supposed to be there to meet it. - So let‟s see: air going in and out - let‟s call that …oh, pick something at random. How about “ventilation”? And perfusion - hmm. Let‟s call that “perfusion”. Do they match? No, they do not. A ventilation/perfusion (“V/Q”) mismatch. 4 5- What are the two relevant concepts of badness (COBs) involved in problems with the lungs? Okay: the two concepts of badness: - COB #1 - Shunt: The bronchi are plugged up. Pneumonia (sputum), CHF (water), that kind of thing. What happens: blood goes past them, but doesn‟t exchange gas. That‟s “shunt”. The percent of blood that doesn‟t get to exchange gas is the “shunt fraction”. Maybe a whole lung lobe is plugged up - left lower lobe pneumonia, maybe? Then a whole lot of blood goes by alveoli with no gas in them. Big shunt. - COB #2 - Dead space: the blood vessels are plugged up. That‟s PE. This time the air goes in and out without obstruction, but there‟s no blood going by them, so all that alveolar space isn‟t being used. It‟s “dead” – “dead space”. (“Mr. Scott, head for the …no, I can‟t say it.”) 6- What’s the confusing thing about the two COBs? The confusing thing is that while the problem happens on one side: either the bronchial, or the vascular, the bad effect is described by what‟s happening on the other side. So – if you have a PE on the vascular side, you wind up with a big hunk of dead space on the bronchial side. And if you have a big pneumonia on the bronchial side, you wind up with a big shunt on the vascular side. Confusing. 7- So then which one is the problem that happens after a PE? Increased dead space. Air goes in and out, but the blood isn‟t going through the alveolar capillaries in that part of the lung. 8- What other bad things happen to people with PEs? Think about this for a second. Remember “preload”? (Half the audience screams and runs for the door. Ha! Locked! And no bathroom breaks either, Werner!) Preload is the volume arriving in one of the ventricles. The amount of blood. Got to have just the right amount of preload - not enough, and the BP drops; hypovolemia. Too much preload and the ventricle starts to get overloaded, and things start to back up - if this happens on the left side, you get CHF. (What if it happens on the right side? How come my shoes feel so tight?) Preload has to come from somewhere. For the right side of the heart, the volume comes from the venous system, right? Everything drains into the vena cavae, then into the RA, then the RV, and then - where? What about the left side? Where does the preload come from? Who said “lungs”? Very good. So - if a big PE comes along and blocks off, say, a whole lung, what happens to the blood supply to the left side of the heart? So what happens to the blood pressure? And what do you think the PA pressures might look like? Would you give this patient a lot of IV fluid to support her blood pressure? Or a pressor? Oh, and yeah - how do you think that might affect the patient‟s breathing? 5 Oh, and yeah #2: the patient could infarct that part of the lung too – but apparently that doesn‟t happen all of the time. 9- What is a DVT? “Deep Vein Thrombosis” : a big clot that forms in one of the big veins in one of the extremities. 10- Why do people get DVTs? Remember all that stuff about “the hazards of immobility”? That‟s one of „em. Think about it – were you evolved to sit in front of the tube with a bag of Doritos? No! – you‟re supposed to be foraging for roots and tubers and all, and chasing down the occasional antelope. So get going! 11- Is it really true that you can get DVTs and PEs if you sit too long on the plane? Apparently quite true and factual: the famous story is that Richard Nixon developed both while flying around doing the diplomatic thing. Couldn‟t have happened to a nicer guy. And what about those 18 minutes, huh? That whole thing about the secretary reaching around the desk like that was just total BS! And you know what else!? He offered a million dollars….okay! Okay. I know – it was a long time ago… He was a crook! And what the hell were we doing in the „Nam anyway, dammit? A year or so ago, one of the senior residents was trying to figure out if he should dose himself with Fragmin before flying to Thailand. I‟d just get up and walk around the plane… 12- What does smoking have to do with it? Definitely increases the risk of forming DVTs. I bet Nixon smoked… 13- What does taking birth control pills have to do with it? Combined with smoking – really increases the risk of producing thrombi. I saw a young woman in the surgical ICU once, years ago, who‟d infarcted her entire bowel. Hmm. Would that embolus have come from a DVT? Hmm. You think Nixon took…?…nah. 14- What if the patient has a cast on? Definitely a problem – a little prophylaxis is obviously the way to go, since detecting a DVT in a casted extremity is going to be difficult. Ortho nurses: should I take an aspirin every day if I get casted for a broken leg? Broken arm? 6 Preventing PEs 15- Can DVTs be prevented? This is really the key to the whole thing. So many people develop DVTs, and so many DVTs and PEs never get caught because they‟re so “silent”, that really the only thing to do is to use preventive measures in almost every admission who‟s undergone surgery, or who is stuck in bed for other reasons for more than a day or two. Then again, it turns out that less than half of patients who look like they‟re having a PE, actually do have a PE. But you‟d hate to be wrong! 16- What are air boots all about? (What do you mean, “Not those!” - I like those!) Air boots apparently work really well – so well that there‟s a separate little category that you‟ll see on physician‟s admitting notes: “Prophylaxis” – by which they mean: “Routine prevention of awful things.” Like PEs – air boots or subq heparin bid are routine, along with something to prevent gastric stress: carafate maybe, or some kind of acid-production blocking med. Actually I think they‟re getting away from heparin now, as fragmin apparently works better, doesn‟t provoke the HIT thing, only needs to be given once a day, and can even substitute for systemic heparin treatment. Cool. I don‟t know enough about fragmin and all those LMW heparins. The air boot concept is easy: squeeze the calves every now and then, keep the blood moving through the veins, prevent it from standing in one place (“venous stasis”), and prevent the formation of DVTs. Somebody seems to be making a lot of dough on this one. Actually I think it was an entrepreneurial spinoff from some people at MIT… Hard to find a picture of those things we all work with. We did find an article on the website of one of the major health insurance companies, indicating that they required these for patients immoblized after surgery, trauma, etc. Now you know they work! A weird thing is that some studies are apparently showing that even one air boot is effective in preventing DVTs – even a single air boot applied to one arm. Doesn‟t seem to make sense on the face of it. 17- What about compression stockings? Cute!. Wish those were my legs! Wait - those are my legs! 7 Apparently these guys just don‟t do the job very well by themselves, although you can get real fancy ones custom-made that will help a lot. Are they called Jobst stockings? Somebody actually sat down and figured out that proper stockings increase the velocity of venous return by some enormous amount. I remember that at one point you weren‟t a really cool SICU nurse until you‟d had your own pair custom-made… 18- What is SQ heparin all about? Right – 5000 units subq, q 12 hours, apparently reduces the chances of DVT by 50%. Whoa – looks like a lot of heparin there, mate! Maybe time to change to fragmin, anyhow. 19- Should my patient get sq heparin if she also has air boots on? I‟ve had house officers tell me that patients need one or the other, but not both. The trick is to make the right choice. 20- Should my patient get air boots if she is already getting sq heparin? See question 19. 21- Can sq heparin be bad? Sure – the HIT thing can apparently be provoked just by going into the patients‟ room and saying the word “heparin”. Seriously – you‟ll see platelet counts drop drastically even in response just to the subq stuff, or the small amount that gets infused through the central line flushes. Put these patients on a no-heparin diet. 22- Can air boots be bad? Absolutely yes – if the patient has a pre-existing DVT, and you slap on the boots, and compress those legs, and dislodge those clots… yowza! I put the question to one of the senior residents a week or so ago: “Hey Ermintrude, listen, do you just go ahead and slap airboots on patients routinely when you don‟t think they have pre- existing DVTs?” Answer: “Yah – if vee don‟t sink zey‟ve got any pre-eggzisting DVT, vee joost shlap „em on.” Dutch, she was, I think… 8 What if the patient never got the boots put on in the first place after admission – what if the nurse forgot, or never got to it, or the team never ordered them, and you came on a couple of days later and said: “Uh, hey - shouldn‟t this guy have air boots on or something?” Would you go ahead and put them on? 23 – Can putting someone on a heparin drip be bad? Absolutely yes. Doing almost anything to, or for a patient involves the possibility that something bad might happen – a “negative outcome”. Your patient has CAD, and is started on a baby aspirin every day, and comes in with a GI bleed. Common? – no. Possible? - sure! And will you see things like that? Absolutely. And the docs sweat that one all the time: “If I put this patient on heparin, what are the chances that she‟ll spontaneously bleed into her head?” Low. Has it ever happened? Sure. Can you predict it? You can try – this stuff gets refined all the time. Stay current, y‟all. 24- Can a patient develop a DVT anywhere besides a leg? Arms for sure – I think that the doppler studies can see them, and I know that we‟ve heparinized, or argatroban-ized patients for them. Anticoagulated them. 25- Can air boots prevent DVTs that happen, say, in my patient’s arm? That seems to be what the studies are saying – so I guess so. 26- Does it have to be two air boots? I know I‟ve seen people with only one boot on – was that because they had a DVT in the other leg, and the idea was to prevent more from forming? Wouldn‟t they have been heparinized for that DVT? 27- What about those little air boots that just squeeze the feet? Yeah – did you see those at the NTI too? Was it hot in Texas, I tell you what? That Riverwalk thing was pretty nice, but that whole business about the free dinner with a lecture didn‟t work out so well. Which classes did you…what? Oh! Sorry! Yeah, we saw these little gadgets at the National Teaching Institute in San Antonio (I got this totally corny Alamo belt buckle, I wear it everywhere), which only compressed the feet, and the company rep claimed that the studies showed that they worked as well as the long boots do. Sounded good, looked a little funny. Anybody seen these in use? Jayne says that these are used on really large patients, because their calves are too large for the standard boots. Detecting DVTs 28- How do I know if my patient has a DVT? This is a very tricky business. Not only do lots of other things act like DVT: leg cramps, strains, sprains, all that stuff, but many DVTs and their subsequent PEs don‟t ever get diagnosed at 9 all. There are studies that show that only something like a third of patients that you might think have a DVT, actually have a DVT. This needs to be carefully looked at, because you don‟t want to be anticoagulating people who don‟t need it, but you don‟t want to not treat someone who needs it. 29- What is Homan’s sign? Homan‟s sign is the thing where you gently pull the patient‟s foot north towards her head, and ask if she‟s having pain in her calf. Apparently not really useful. 30- What is a venogram? This is a dye study that is considered the “gold standard” for DVT testing. Nowadays however they try do Lower Extremity Non-invasive Testing, which is an ultrasound procedure. Apparently quite accurate. Always good to try and avoid exposure to contrast dye. Why? 31- What are LENIs? “Lower Extremity Non-Invasives” – a kind of ultrasound testing that tries to look for DVTs – apparently a pretty effective and accurate test, although there are sometimes problems seeing the deeper veins. 32- Should my patient have LENIs before getting air boots applied? I can remember when this was the rule – nowadays if there‟s no reason to think that the patient has an active DVT, the usual plan is to just put them on a bedrest patient routinely. 33- What does d-dimer have to do with it? Jayne says that d-dimer goes up whenever there‟s a clotting process going on somewhere in the body. So yes, d-dimer will go up if a patient has a DVT or a PE, and you will see the spec sent when they‟re doing the workup, but the d-dimer can also go up if the patient has recently had surgery, or maybe has a tumor process going on. It‟s not much of a specific signal by itself, but when added to the workup it helps narrow things down. Detecting PEs 34- How do I know if my patient has a PE? Even though the whole picture can be really hard to sort out, some things usually don‟t look right. - The patient may have chest pain without ischemic EKG changes. (Jayne: “You‟d look for the EKG changes that go with right heart strain.” Well, see? - now that‟s a CNS for you, right there. Smarty. My smarty.) It makes sense though – if the right side of the heart is trying to pump through a partially obstructed lung, it‟s going to be working harder than it normally would. Actually, only about 20% of PE patients show right-heart-strain EKG changes. (I looked up that last one – you have to look things up when you‟re talking to Jayne..) 10 - The patient will probably be short of breath. Makes sense. - And tachypneic. And tachycardic. - Even the most expert practitioner can be completely fooled one way or the other. 35- Can you see a PE on a chest x-ray? Apparently hardly ever. 36- What is a VQ scan? This is one of those radiation-tagged-perfusion-nuclear-imaging jobs. The results are either “high” or “low” probability – in the case of a patient who is likely to having a PE, even a completely silent one, a suspicious VQ study has to be followed up with some other kind of confirming scan. Lately a lot of our patients have been going for a spiral CT with contrast to rule PE in or out. 37- What is a pulmonary angiogram? Wow, man - far out! “PLEASE DO NOT TAKE ANY OF THE BROWN ACID!” (I will personally send a nice present to anyone who can tell me who said that, and where.) This is apparently the gold standard diagnostic test at the current time. Go in there, inject some dye, light up the vasculature, do lots of fluoroscopy, and see if there are places where perfusion just isn‟t happening. Nice to avoid dye studies if possible – bad for the kidneys. Keep the mucomyst thing in mind whenever you hear the “dye” word. Kinds of PEs 38- Are there different kinds of PEs? Apart from where they‟re coming from, apparently it has mostly to do with how big they are, and how much lung they plug up. Bigger would be worse, I would guess. 39- What is a “saddle embolus”? (Mr. Ed – you want to handle this one?) This is the PE equivalent of an antero-lateral MI – the widower-maker. The (very large) clot goes and lodges itself at the bifurcation of the pulmonary artery. Ack! That‟s sort of the root of the pulmonary circulation, right there. These people are going to be in serious need of some serious treatment, seriously soon. Sometimes the surgeons will actually go in after a clot like this: “embolectomy”. A while back somebody told me about a clot that a surgeon pulled out of some patient‟s PA that was “the size of a carrot”. I hope he got better! The patient, too! 11 40- Are there other kinds of emboluses? Remember – anything that can hang together and move along the lumen of a vessel can be an embolus: clots for sure – what else? There are air emboli, fat emboli, amniotic fluid emboli…I seem to recall that bullets can do weird things if they get into blood vessels, although they don‟t usually come under the category. Lead embolus, maybe? More on these below. Treating PEs 41- How are PEs treated? Clot lysis and anticoagulation are the main things. (And maybe handgun control?) Heparin followed eventually by coumadin is apparently the way to go with anticoagulation, because it prevents the formation of additional clots – apparently where you have one clot, you have the high likelihood of making more – maybe many more. So anticoagulating the patient can save her life by preventing more clots from forming and being thrown into the lungs. Obviously the patient may have to be treated for hypoxia, right? You‟re an ICU nurse now. What should we do? 42- How long does a patient have to stay on heparin for a PE to dissolve? Trick question – heparin doesn‟t dissolve a clot. You eat up the clot yourself: you phagocytize it, or whatever. Chomp, chomp, little white cells! Apparently it can take up to a month to eat up a PE. “Anticoagulation, by preventing clot propagation, allows endogenous fibrinolytic activity to dissolve existing thromboemboli. The rate at which this process occurs is variable. Although complete clot lysis has been reported after as little as 7 days, resolution typically occurs over several weeks or months; in many patients, however, resolution is incomplete after several months.” http://www.chestjournal.org/cgi/content/full/115/6/1695 43- What does TPA have to do with it? Potentially lifesaving, potentially deadly. This one really takes some careful consideration, and I can‟t remember seeing it used in MICU patients more than a couple of times. I guess sometimes it‟s safer to intubate a person, heparinize her, and wait for the PE to get eaten up than it would be to give a fibrinolytic. Imagine if the person had a history of hemorrhagic stroke? Or recent surgery? Horrible to even think about… On the other hand, Jayne tells a story about a code she saw – big, nasty, chest-pumping, defibrillating, intubated code - nothing was working, just wailing away, and up pops the emergentologist, who says: “Give TPA – it might be a PE.” And it worked! And the patient went home! What did the big turtle say in “Finding Nemo”? – “Whoooaaaa!” 12 44- How is a big PE or a saddle embolus treated? Well, see, there you are: faced with your decision tree, right there. 45- What is clot lysis all about? As above: this stuff – not heparin – is what‟s going to dissolve that nasty PE. Apparently TPA and streptokinase work equally well, and the results in the initial studies were so impressive that sometimes the studies were stopped – almost everybody getting lysed was getting better, and everybody else was doing badly. The thing is, the stuff is so dangerous that they usually save it for patients who are having serious blood pressure trouble…why? Another neat thing about lysis is that it not only dissolves the clot that‟s made it to the lung, but the other ones hiding in the leg veins just waiting to break loose and make more trouble… We recently had a patient come in after a transatlantic flight, during which he apparently never moved a muscle, who went down in front of the stewardesses at the end of the flight. Hypoxic, hypotensive: he‟d developed several huge PEs. Looked terrible – got lysed. Got better! Extubated the next day – his wife was crying, he was crying (“I thought I was dead!”), we were practically all crying…big save! Here‟s a comprehensive reference article that was written by an ER doc at Jayne‟s hospital: http://www.remotemedicine.org/Paths/chestpain.pdf - an excellent and thorough resource. 46- What does coumadin have to do with it? If you‟ve got the kind of body that‟s going to produce a DVT/PE once, then the chances are that you‟re going to do it again. I‟m not sure what the study numbers are exactly, but I know that given a certain age, history, body habitus, etc., some people are going to go home on coumadin for life. 47- What are IVC filters all about? Here‟s an example of one of the filters that are sometimes placed in the IVC to trap thrombi before they can get to the lungs – this is a Greenfield filter, and that‟s either a clot or a red chili pepper that it‟s caught there. 13 Other Kinds of Embolisms 48- What is an air embolus? A big bubble of air injected into the circulation will travel along the vessels as a blob, and you can effectively plug off pulmonary circulation with big bubbles just as well as you can with clots. In the ICU you want to worry about this happening in connection with central lines, and a couple of main points should be made: - remember that at times the pressure inside the chest can go negative. If you have an uncapped port on a central line, it will suck air into the patient. - If you‟ve removed the PA line from one of the introducers with the little black membrane, then you need to remember that the membrane isn‟t airtight anymore, and unless you cover it with a tegaderm or insert an obturator, it will suck air into the patient. - If you remove a central line and forget to slap an air-occlusive dressing over the site, it may remain patent and suck air into the patient. Just don‟t let this happen. 49- What does a patient with an air embolus look like? Usually awful – like someone with a big PE. Blue, short of breath, chest pain – and what‟s that horrible sucking sound? That‟s if it goes to the lungs. Everybody see that nasty thing down there on the lower right? According to the U of Iowa‟s website, this is an image of somebody who managed to send an air embolus to his/her head. Left-sided-circulation embolus. Scuba diver maybe? Don‟t hold your breath on the way back up! Pwing! http://www.uiowa.edu/~c064s01/nr320%20copy.jpg Apparently the big risk for air embolism is during surgery – and it‟s pretty dangerous: something like 50cc can displace most of the blood on the right side of the heart, and 300c can be lethal. 50- An incredibly important point: rapid IV boluses. This raises a point that does come up fairly frequently in the MICU. Giving a rapid fluid bolus from a liter bag of saline involves putting the IV solution into one of the while compression bags that we use for arterial and central lines. Hold a liter bag of NS up to the light – how much air is in that bag? If you don‟t vent that air, the compression bag will pump it right into your patient. Don‟t let this happen. Spike the bag upside down and squeeze the air out through the tubing. Every time. 14 51- What should I do if I think my patient has just pulled in an air embolus? A little tricky – let‟s see if I can remember this right. What you want to do is try to trap the air in the RV in such a way that it won‟t get pumped out towards the lungs, so you‟re supposed to: - Get the person into trendelenburg position with the right side up, which will trap the air in the right atrium (ventricle?) and prevent it from getting into the circulation. - Apply oxygen. - Get the team. The maneuver is to try and aspirate the air from the RA (RV?) through a CVP line until no more can be removed. 52- What is a fat embolus? I‟ve never seen one, but I understand they happen sometimes after long bone fractures. 53- What is an amniotic fluid embolus? These are really rare - something like once in 20-30,000 deliveries, and I don‟t think we‟ve ever seen one come into the MICU. Deadly, however. The idea is that amniotic fluid gets injected into the systemic venous circulation, and from there makes its way to the lungs. I don‟t think I‟ve ever seen one, but once in a great while we do get an obstetrical patient into the MICU.