Water Work Made Easy

   My current medic class is just wrapping up its first quarter, with the major focus being the cardiology and pharmacology blocks of instruction that also include medical math and IV therapy. In days of old, it was not uncommon for a rig to have four choices of IV fluids: normal saline, lactated Ringer's, D5 and one-half normal saline. Nowadays, normal saline is pretty much the fluid of choice.

Tips for Drips

   Getting an accurate manual setting on an IV line in the back of a moving rig is challenging enough, even when the goal is just TKO, i.e., a rate that flows just enough to keep the vein open. The standard for a TKO IV line is one that flows between 25 and 50 cc/hr. These numeric parameters are certainly no coincidence, as they mirror the approximate amount of urine the kidneys excrete every hour. Having this match between in and out can be critical for a patient in acute pulmonary edema/congestive heart failure, when overhydration can worsen pulmonary edema to the point the patient is literally drowning from the inside out. These same TKO limits for an IV line can also be critical for a patient with rising ICP secondary to a head bleed, where extra fluid equates with extra edema/swelling, which can result in increased morbidity and mortality.

   In the pursuit of TKO, I've heard one drop every 6 seconds, one every 10, and the virtually impossible-to-set one every 15. Why? With 6-second increments, you are trying to catch a drop at 6, 12, 18, 24, 30, 36, 42, 48, 54 and 60 seconds on a watch with major increments set every 5 seconds and minor increments set every second. That is visually overwhelming. Going for one drop every 10 seconds is almost impossible to set and only delivers 6 cc/hour, while one drop every 15 seconds cuts the flow to 4 cc/hour. Both rates will almost certainly result in a clotted IV line.

   Truth be told, there are really only three viable choices when setting a flow rate on an IV with a 60-gtt microdrip set: one drop per second, one drop every 2 seconds and one drop every 5 seconds. These three settings deliver 60 cc/hour, 30 cc/hour and 12 cc/hour. The 60 cc/hour setting is slightly high, but arguably inconsequential (10 extra ccs spread over an hour), while the 12 cc/hour setting is a tad low, but certainly doable. The one drop every other second flow rate is arguably the easiest to set and delivers the middle ground for a TKO line.

The Battle of Boluses

   There is no shortage of data pointing to the dangers of overaggressive fluid therapy and the pursuit of "normotension" when resuscitating a trauma patient. The first of the two major issues is that of raising the patient's BP top to the point where they blow out the clots the body is trying to form to control bleeding. The second issue is often called the "Kool-Aid" syndrome of overhydration: The patient is bleeding dark red blood that transitions to medium red, light red, dark pink, medium pink, light pink and finally clear, resulting in a patient who has a great blood pressure, but succumbs to coagulopathies. As such, the model of permissive hypotension, whereby a pressure adequate to maintain perfusion is the goal, can be safely accomplished with small, serial boluses of fluid therapy.

   I believe that the best choices for serial bolus therapy are one of four choices: 200, 300, 400 or 500 cc. First off, the large hash marks on each 100-cc level on the IV bag are easy to monitor with just a quick glance up at the bag. Physiologically speaking, anything less than 200 ccs is unlikely to have much impact on raising the BP, especially with very fast heart rates (>150) where inadequate preload is the problem. By comparison, moving beyond the 500-cc mark (1/2 liter) can potentially move into the overhydration range, again putting your patient into pulmonary edema. Pulmonary edema comes with its own set of problems, but those problems increase if the cause is overhydration that now has to be removed with a diuretic like Lasix. When Lasix is the solution to the problem you've just created, you are looking at about 20 minutes before you start to see any effects. When you are dealing with a trauma patient, the Lasix may further contribute to fluid and electrolyte imbalances, especially potassium levels.

Conclusion

   A large dose of common sense is a key ingredient, both with setting IV drip rates and use of serial boluses. The second ingredient for success is paying excellent attention to detail with both interventions. Having your primary IV line clot off means you have to reestablish vascular access on your patient, which obviously takes time away from other assessments or interventions that are arguably more meaningful and beneficial. By the same right, inadvertently letting an IV line run away and raise the blood pressure to the point of blowing out clots and/or creating coagulopathies is clearly a dangerous, even potentially fatal mistake. Neither are components of quality prehospital care.

   Until next month...

   Mike Smith, BS, MICP, is program chair for the Emergency Medical Services program at Tacoma Community College in Tacoma, WA, and a member of the EMS World editorial advisory board.