Hypodermoclysis (HDC, subcutaneous fluid infusions) has become a widely accepted route for parenteral hydration.
When parenteral hydration is indicated in dying patients, clinicians are generally faced with a decision to use HDC or intravenous (IV) hydration.

Advantages of HDC over IV
Starting and maintaining a subcutaneous infusion catheter is relatively pain-free; it is a simple procedure that can be done by trained patients or family caregivers. HDC provides greater potential sites for needle placement (arm, back, abdomen, thighs), and equipment costs are generally lower than with IVs. Subcutaneous catheters can be easily disconnected from IV tubing and re-used later, allowing a patient to receive intermittent fluid treatments. Portable infusion devices are not needed with HDC. HDC infusions may also cause less agitation in patients with dementia versus IV.

Disadvantages
HDC is limited by a continuous infusion rate of 1-2 ml/min or 1.5-3 L/day. Bolus infusions (up to 500 ml/hour) are possible with HDC, but often require hyaluronidase. Both HDC and IV infusions have similar rates of local adverse events (e.g., erythema, cellulitis) and lifespan of infusion site. HDC can be technically difficult in patients with substantial peripheral edema and in cachectic patients with little subcutaneous tissue.

Technique
- Equipment needed: Small butterfly needle (usually 22 gauge) or angiocatheter, skin preparation (alcohol or iodine), sterile occlusive dressing, solution bag (saline or saline-dextrose combination), tubing with drip chamber. The use of an electrolyte-free solution like 5% dextrose favours third-spacing risks that can cause tissue sloughing or, rarely, circulatory collapse.
- Procedure: After cleaning the local site, insert the needle bevel up into the subcutaneous tissue. Attach to fluid and tubing and cover with occlusive dressing. Select an infusion fluid and set drip rate or fluid bolus. Normal saline (NS) is typically used, although half-normal saline or 2/3 D5W in 1/3 NS have also been used. Drip rates can be set to 20-125 ml/hour with gravity (no pump required) or 1-2 ml/minute. Some patients may prefer drips set to gravity 24 hours per day at a low rate (e.g., 50 ml/hour), overnight hydration (e.g., 100 ml/hour), or intermittent fluid boluses (e.g., 500 ml).
The volume of infusion needed to keep acceptable levels of hydration in many palliative care patients is lower than healthy patients and postulated to be ~1 L/day.
Some change the site only when there are symptoms or needle displacement, while others choose a fixed time (e.g., every 3 or 7 days) or fluid volume (e.g., every 1.5 L) Teflon cannulas can be used for a week and are helpful for patients who have trouble maintaining a catheter site. Local anesthetic creams may be helpful during catheter placement to reduce discomfort, especially in children.

Recombinant human hyaluronidase is an enzyme that temporarily lyses the subcutaneous interstitial space to promote diffusion of fluid; it can be used for site discomfort or if a faster rate of absorption is desired. Doses of 150 U to 750 U given as steady push prior to the infusion can yield fluid rates of 380 to 520 ml/hour.

Uncommon local reactions include edema, local pain, or erythema. Rare complications include cellulitis and vascular puncture. Systemic complications such as pulmonary edema can occur with all types of artificial hydration.

See reference for more information.

Adapted from Kamal AH and Bruera E. Hypodermoclysis. Palliative Care Network of Wisconsin. Fast facts and concepts #220. Internet. Accessed on February, 2018.