Introduction with a case
Physiology of sodium over-correction
Managing sodium over-correction: DDAVP vs. D5W
Rescue DDAVP strategy
Reactive DDAVP strategy
Proactive DDAVP strategy
- DDAVP (2 micrograms IV q8hr) is started immediately and continued until the sodium is close to normal.
- Sodium is corrected by infusing hypertonic solutions, primarily 3% saline. Of course, hypertonic bicarbonate could also be used, as discussed last week. For a patient requiring volume resuscitation, a large volume of normal saline could be used as well. The key point is that the sodium is increased by a direct effect of the infused solutions. This differs from approaches based on treatment of the underlying problem and waiting for the kidneys to excrete free water.
- Oral fluid intake must be restricted while on DDAVP.
- Potassium supplementation should be taken into account as this is osmotically equivalent to sodium (e.g. 40 mEq KCl tablet is roughly equivalent to ~80ml of 3% NaCl).
- Medications formulated in D5W should be avoided if possible, or otherwise taken into account (e.g. 100 ml of D5W will negate the effect of ~30ml of 3% NaCl)
- If volume overload occurs, this may be managed with furosemide.
An example of how this strategy would work for a patient with severe symptomatic hyponatremia is shown below. DDAVP is started immediately to block renal free water excretion. Boluses of hypertonic therapy are provided initially to improve symptoms and raise the sodium by ~5 mM. Given that the target rise in sodium over the first day is ~6 mM, after the initial increase in sodium, fluid intake is stopped for one day causing the sodium to be stable. Subsequently, an infusion of hypertonic saline is started to gradually increase the sodium to normal.
Contraindications to proactive DDAVP
Evidence supporting the proactive DDAVP strategy
Vaptans = The opposite of DDAVP
- Over-correction of sodium is usually due to recovery of normal renal physiology with excretion of water.
- DDAVP blocks renal excretion of water, allowing the sodium to be predictably manipulated using the Adrogue-Madias equation. This can be accomplished using three strategies:
- Rescue DDAVP strategy: If the sodium has already over-corrected, DDAVP may be combined with D5W to decrease the sodium.
- Reactive DDAVP strategy: If the sodium is rising at a dangerous rate, this may be temporarily halted with a combination of DDAVP and fluid restriction. This stops free water input and excretion, causing the sodium to be relatively stable over time.
- Proactive DDAVP strategy: For patients at high risk for osmotic demyelination syndrome, it may be safest to start DDAVP immediately. With this strategy, DDAVP prevents water excretion from the kidneys, so hyponatremia must be treated directly by infusing hypertonic fluids.
- Conivaptan and Tolvaptan may cause uncontrolled water excretion and over-correction of the sodium. This is not recommended.
- Hyponatremia in general
- Proactive DDAVP strategy
- 2014 European Consensus Guideline on Hyponatremia
- Sterns 2010: Explanation & example of proactive DDAVP strategy
- Sood 2013 : Largest case series of proactive DDAVP strategy.
- MacMillan 2015: Fresh systematic review of DDAVP in hyponatremia
Latest posts by Josh Farkas (see all)
- PulmCrit: Which patients admitted for pneumonia need MRSA coverage? - July 18, 2016
- PulmCrit Wee: Is piperacillin-tazobactam nephrotoxic? - July 9, 2016
- PulmCrit: What is the fragility index of the NINDS trial? - July 5, 2016