How much more coffee did I drink on my internal medicine rotation?

Internal medicine is much like an abusive relationship. There's a lot of fear and anger and sleepless nights during the whole experience but after you leave them you always look back with a weird amount of positivity. 

For a lot of medical school, students are treated (with pretty good reason) like barely functioning, hung-over hooligans who shouldn't be given a bag of sand to look after much less a living patient. Not so on your third year internal medicine rotation. Your patients are your responsibility, and nobody second guesses your management plans except to tweak it or give suggestions. For myself, it was the first time I threw on the big boy stethoscope. You feel like a real doctor. Besides that you learn an incredible amount and you work with some of the smartest residents and attending doctors in medicine. This really makes all the difference in an intense situation like an internal medicine ward - I had three very intelligent and patient senior residents who taught me a lot. Same goes for my three attending physicians. 

On the other hand though, my internal medicine rotation was the most grinding, gruelling marathon in which I've ever participated. Looking back I think I easily worked 100+ hours per week. My day started at 645AM when I would come in to Health Sciences Centre in Winnipeg to see my patients, check labs, make a plan, etc. We would round on patients (walk around, say hello, examine them, make orders, call consultants) until about 1130 and then in the afternoon we would write notes, do procedures and get some teaching from the senior medical resident. Sign-out rounds (sitting down and talking about what happened during the day for each patient and talking about any patients coming to the ward that night) were at 5PM and then anything else that hadn't been accomplished would be completed after that. 

630PM days were pretty normal unless you were on call in which case, saddle up, because you're here for the next 14ish hours. One person from the team would always stay on the ward overnight and for me it was always a special experience. When on call at Health Sciences, your night consisted of making sure no one died, pronouncing people who died, admitting new patients to the ward, writing orders for patients who needed medication changes, getting called to an imminently dying patient and if you were lucky maybe an hour or two of sleep. You then got to go home after presenting your patients on rounds the next morning and slept for the entire day (your post-call day). Wash, rinse and repeat the next day. Call, for me, was about every four days (on average - an important distinction).

Because of this most of my classmates, and myself, look back at these six weeks with an almost Stockholm Syndrome-like reverence. It's the most immersive learning experience I have ever had (and an overall positive one) but because the above is pretty typical of internal medicine residencies, it doesn't have a reputation for being a job with a balanced lifestyle. I once had a senior internal doctor tell me verbatim "nobody gives a shit about how well-rounded their doctor is, so study more", which seems harsh but if I was sick and in the hospital I would want this guy looking after me, no questions. Internal medicine docs have a reputation for being exceptionally smart and being great problem solvers, but they don't have a lot of hobbies.

Now let me backtrack a bit to be clear for those without a medical background. Internal medicine doctors essentially run every major hospital in any city in Canada - they're experts in diagnosis and treatment of diseases. They don't do surgical stuff but if you get admitted to hospital for something like a heart attack you see a cardiologist who is an internal medicine doctor.  Other internal doctors include those who do infectious disease, lungs, kidneys etc. - these are all internal medicine sub-specialists. Consultants are extremely important in patient care but to be fair to the internal medicine people, rotations on sub-specialty consulting services are much less intense from a time-commitment standpoint than CTU.

In Winnipeg, on the ground care is delivered by general internal medicine doctors through a general medicine ward or clinical teaching unit (CTU - medicine loves abbreviations). Any specialty involvement is as a consultant to the CTU team, with some exceptions (cardiology for example has its own ward at one of the major hospitals in Winnipeg). Medical students in third year are embedded as part of a team that runs the CTU, which means that they take care of patients directly, and I was one of these medical students about 8 months ago. 

But back to the question that started this post. CTU is a long, grinding experience. As a guy who needs to have coffee to avoid drooling in front of people on a normal day, the 26 hours that I would sometimes go without sleep really upped the ante on my caffeine addiction. I don't think my experience was all that atypical either. I would often hear my other classmates commiserate about what cup they were on that day when we all met for some group teaching session on our weekly half day off. So how bad (or good?) did my coffee drinking get during my CTU rotation?

To answer this question, I had to do the one thing every medical student hates to do more than anything else. I had to look at my Royal Bank of Canada credit card statement. The great thing about banking with RBC is that along with monstrous, soul-crushing debt, it provides me the ability to download expenditure data into a CSV file through my online banking. They're also kind enough to mark all expenditures on the statements as negative just to remind you that you owe them this money. A $2.00 expenditure is not just marked as $2.00, but as -$2.00.

Because I never had any time to sleep, I definitely didn't have the time to go get cash from an ATM and all of my coffees were bought via credit or debit card. From this I can pick out all the dates that I went to the Starbucks or Tim Hortons or Subway or the hospital cafeteria in a four-month period around the time I was on  the CTU at Health Sciences. Because I also know how much I spent, I can also tell about what size the coffee was. I have converted all of this into a rough estimate of the  daily caffeine content that I purchased using nutritional information from menus on company websites. I also had to make some guesses about how much coffee I purchased because of some bills that included snacks or other purchases that didn't exactly line up to an amount that would direct me to a coffee size. For these instances I've tried to give a conservative estimate of the amount of caffeine I consumed. 

The important thing in posing this question though, is how my coffee intake changed with regard to a comparator. I can easily tell you what my coffee intake was over my time on CTU, but if I was already drinking the same amount before the rotation, it doesn't really demonstrate anything about the intensity of CTU. To use some lingo I picked up in medical school, my "treatment" period then is my time on CTU and what a treatment it was. My "control" period is just before and just after my CTU rotation. In total this comprises the period of June until the end of September.

To give some context, the three weeks prior to CTU I did my rotation through Children's Hospital in Winnipeg on one of the paediatrics wards, which in itself was a whole bag of laughs. But this was at least similar to the ward work at Health Sciences except with less call. The period after CTU I went on vacation (thanks for taking me Mom!) for two weeks and then did four weeks of emergency medicine at a community hospital in Winnipeg. The emergency medicine schedule is usually an 8 or 9 hour shift and then you're done - any patients still around you pass on to the next ER doctor. While they both have their own idiosyncrasies, for the purposes of this exercise we'll call them typical of my coffee routine during medical school outside of CTU. 

So lots of writing but lets latte the stats do the talking. During the four month period I bought coffee 84 times. Of these, 49 purchases were during the CTU or treatment period whereas 35 were in the control period. While only comprising 6 of the 16 weeks in the time period my CTU rotation was responsible for 58% of the total coffee purchases in this timeframe. Comparing the percentage of all of my purchases (coffee or otherwise) in the treatment period shows a similar effect that CTU had on my life. Coffee comprised 66% of all transactions I made during this treatment period. In contrast coffee comprised 35% of all of my purchases during the control period. All very suggestive about CTU's effect.

In terms of coffee loyalty, this data reveals me as a true Starbucks man. Over the whole period, the vast, vast majority of coffee I bought was from Starbucks. Over 73% of my total coffee purchases were at Starbucks, with Subway coming in a distant second at 10.7%, and really that's only because I bought a sandwich at the same time and was too lazy to make a separate trip to Starbucks. For those not in the know, Guildy's and Pedway (now defunct) are/were two cafeteria-style restaurants at Health Sciences Centre.

If we confine examination to the treatment period on CTU, Starbucks purchases rise to over 95% of my total coffee purchases. This sharp increase was because all of these other coffee places couldn't really compete with Starbucks for scheduling reasons. Starbucks was open all night and everyone else wasn't, and that's when I got the majority of my coffee on CTU. I would've drank week-old coffee grounds strained through a worn hairnet on some of those nights so how much my slavish loyalty says about Starbucks is debatable. I also have no idea how doctors function on CTUs without a 24-hour coffee shop nearby.

Slavish devotion to Starbucks in one picture?

Moving onto a more in-depth analysis of how much coffee I consumed above my baseline level because of CTU, below is the time-series of total coffee consumption during the four months. There are two figures here, and the second is more confusing than the first but they're essentially the same graph. The first figure is a time series of my total caffeine consumption purchased during the four-month period. This also has a gap when I went on vacation (and didn't pay for anything - thanks again Mom!).

The second figure is a time series of each rotation with the origin being the initial day I was on the rotation. Day 0 is the first day I began each rotation and for example, day 40 is the last day I spent on CTU (a total of six weeks with some gaps for weekends). This allows comparisons of how my caffeine intake changed as each rotation progressed.

Time series of caffeine intake

Caffeine intake by rotation where day 0 is the first day on rotation

Now what can we say about each of the control periods on emergency medicine and paediatrics? Statistically they are exactly the same. I drank an average of 325mg of purchased caffeine each day while I was on paediatrics wards. After CTU, on emergency medicine I consumed about 300mg of caffeine per day.

Where it gets interesting is during the treatment period. What's particularly interesting to me about these two graphs is that you can literally pick out the days that I was on call for the CTU. The spikes in use of caffeine correspond to the evenings I was on call. The saw-tooth pattern is a result of getting a lot of coffee the night I was on call and then a couple on the morning that I was post call. I would go for a coffee at about 0300 or 0400 and then again just before rounds at 0800. After this I would go home, have greasy post-call breakfast, and sleep. This would mean that on these post-call days I would have maybe two coffees to try and get myself through rounds in the morning.

The trend in caffeine intake also is indicative of how sleep-deprived I was during my CTU rotation. During my first two or three weeks I was probably on call every two to three days, which made for a giant, increasing sleep deficit. The escalating caffeine doses during these first three weeks demonstrates this. Notably, neither my paediatrics wards or emergency medicine rotation display similar behaviour. Then in week three or four of CTU I had a glorious period when I didn't have any call. I caught up on sleep and reduced my coffee intake significantly. In the final two weeks, I had significantly less coffee intake except for my final day when I bought a giant group-sized Starbucks coffee lug to share with the nursing and ward staff as a thank-you. I drank about 5 cups of coffee of this mostly because I was post-call on my last day before vacation (thanks Mom!) and was trying to ride the euphoria.

Explaining this relative decrease in caffeine consumption during weeks 5 and 6 may be related to how well CTU in Winnipeg teaches you to do an internal medicine history and physical. If I remember correctly, I managed to get more sleep during this period because I was able to recognize what I was looking for with the brief information I was given as the patient was transferred to the ward. This is graphical evidence, in coffee form, of exactly what internal medicine docs want medical students to get out of a CTU rotation. They want to teach you to be thorough but efficient when you deal with complex patients. You pick this up after a couple weeks of the CTU routine.

Overall, this analysis would suggest that I consumed 678mg of caffeine per day on my CTU rotation. This is significantly above the control periods that I discussed earlier. The standard deviation of my caffeine consumption went up significantly as well, suggesting that not only did I increase my caffeine use, but CTU also caused my intake to become much more spread out. On days when I consumed purchased caffeine I consumed a lot, but on days when I didn't, I consumed way less caffeine. During my CTU I approximately doubled my daily caffeine intake from about 300mg to 678mg of caffeine. A Starbucks "Grande" coffee has approximately 330mg of caffeine in it, so I was taking in an additional one of these each day because of CTU. 

Its important to remember though that the total caffeine intake on CTU that's shown here is likely an underestimate of my total intake. It doesn't take into account any times that I brought in a travel mug and had more coffee than the normal "Grande" that I usually purchased. In a pathetic attempt to limit how much coffee I was consuming at one point I consciously tried to buy Starbucks Refreshers to avoid coffee. These have some caffeine that is not accounted for here. In addition it must be noted this does not include any coffee I brought from home and I did this a lot when I was on CTU. I never thought I'd be desperate enough to drink powdered coffee packaged in Africa, but then I never had been on a CTU before this year.

The perceptive among my three readers will also note another fact about these time-series. This is essentially a graph of my 2014 summer slipping away in cups of coffee. I began paediatrics wards on June 1st and ended internal medicine wards on August 1st.

I often feel a twinge of regret looking back on a summer that I spent indoors on hospital wards but, baby, if you just take me back, I'll forget everything internal medicine.