Practice Perfect 657
Intravenous Fluids for the Podiatrist

At some time or other, every podiatrist has been responsible for managing intravenous (IV) fluids in their patients. For those of us with a surgical component to our practices, ordering IV fluids is an everyday part of practice. However, for many of us, this is an aspect of patient care that is ordered by rote or habit without much regard to the medical science behind it. As a quick refresher, here’s a short, high-yield review of IV fluids and the important considerations and recommendations to help our patients.

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Routine Fluid Maintenance – What a Normal Patient Needs and Why

Let’s first start with the bare minimum needs for our patients. For routine maintenance, our patients need the following1,3:

Water: 1600 mL/day total
Potassium, sodium, and chloride: ~ 1 mmol/kg/day
Glucose: 50-100 g/day to avoid starvation ketosis

The next important piece of information is to know where we lose water:

Urine: 500 mL
Skin: 500 mL
Respiration: 400 mL
Stool: 200 mL
Estimated Total Loss: 1600 mL/day

Obviously, all of these numbers will vary with significant increases in water loss in sick patients. For example, for every degree of body temperature over 37° C, water requirements increase by 100-150mL/day.3

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Fluid Therapy Defined

There are two main aspects to fluid therapy, maintenance and replacement. Maintenance therapy is what most of us are doing when we order fluids on preoperative patients about to undergo surgery. However, we should also keep in mind fluid replacement may be necessary in patients with acute illnesses such as sepsis, where dehydration is common.

Fluid Status

The first step, then, when initiating IV fluid therapy is careful assessment and monitoring of fluid status, including history and physical, clinical monitoring, and daily labs (in hospitalized patients).1

The physical examination of a patient for hydration status should include: pulses, blood pressure, capillary refill, jugular venous pressure, peripheral edema, pulmonary edema (fluid in the lungs), and postural hypotension.2

Signs of hypovolemia needing fluid resuscitation include2,3:

  • Systolic BP < 100mmHg
  • Heart rate > 90 bpm
  • Respiratory rate > 20 breaths/min
  • Capillary refill > 2 seconds
  • Cold extremities
  • Reduced skin turgor
  • Low urine output or concentrated urine
  • Low urine sodium concentration

Signs of hypervolemia:

  • Resting dyspnea
  • Paroxysmal nocturnal dyspnea
  • Orthopnea
  • Hypertension
  • Abdominal ascites
  • Extremity pitting edema
  • Jugular venous distention
  • Decreased oxygen saturation
  • Pleural effusions on AP chest radiographs
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Fluid Options

Recall that there are four types of fluids:

  1. Crystalloids (AKA saline) - Consists of saline and water in different concentrations. Normal saline (0.9% saline) is made from 9g of NaCl per 1 liter of water. Half normal saline (0.45% saline) is 4.5g of NaCl per 1 liter of water. Appropriate for maintaining both intravascular and extracellular volume.
  2. Balanced Crystalloids (AKA Ringer’s lactate) - Consists of sodium chloride, sodium lactate, potassium chloride, and calcium chloride in water. Quickly excreted from body, as opposed to normal saline.
  3. Glucose Solutions - Various concentrations of dextrose in water. These may be added to crystalloids.
  4. Colloids – Used in very specific situations where volume expansion is necessary. Generally, not a podiatric fluid option.

The Bottom Line: 0.9% saline and lactated ringers are both isotonic solutions, so are very similar to blood and both can be safely used in preoperative patients.

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What Rate of Infusion is Reasonable?

Based on the information discussed in the routine maintenance section above, in order to maintain fluid balance in an otherwise healthy, nonfebrile patient, the typical 100 cc/hour would give a patient 2400 mL of fluid/day, which is too much. However, keep in mind perioperative patients lose more fluid due to blood loss and an often baseline dehydration from being NPO. This would then be a reasonable rate in patients expected to restart oral fluids soon after surgery, but should be dropped to something more like 60-80 cc/hour (1440-1920 cc/day) if expected to remain in house longer. Don’t forget to monitor fluid status carefully in hospitalized patients, with the best method being monitoring fluid input and output and tracking weight.

According to the Daleks, the evil robots from the Science Fiction show Doctor Who, humans are “mostly bags of water,” and we can’t forget this very important situation in our patients who need intravenous fluid replacement.

Best wishes.

Jarrod Shapiro, DPM
PRESENT Practice Perfect Editor
jarrod@podiatry.com
References
  1. Gottenborg E, Pierce R. Clinical Guideline Highlights for the Hospitalist:The Use of Intravenous Fluids in the Hospitalized Adult. J Hosp Med. 2019 Mar;14(3):172-173.
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  2. NICE Guideline: Intravenous fluid therapy in adults in hospital. Published December 10, 2013.
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  3. Sterns R, Emmett M, Forman J. Maintenance and replacement fluid therapy in adults. UpToDate. Current through April 2019. Last accessed May 24, 2019.
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