Subcutaneous infusion, or hypodermoclysis, is a method in which fluids are infused into the subcutaneous space via small-gauge needles. Clysis means the introduction of large amounts of fluid into the body usually by parenteral injection to replace that lost. So hypodermoclysis means via subcutaneous tissue and phleboclysis means via the vein.
After the fluid is infused subcutaneously, it is diffused into the circulation.
Hypodermoclysis was first described in 1865 for treating dehydration in patients with cholera. It is a good alternative to venous infusion in infants, children, and adults, particularly elderly adults in whom venous access is difficult.
Advantages of Hypodermoclysis
Subcutaneous infusion offers several advantages
- Simple, economic alternative means of infusion for patients with difficult IV access.
- Does not require specialized expertise, quick to do
- May be used in multiple settings, including home, nursing home, hospice care, and other settings
- Reduces the risk of pressure sores and deep vein thrombosis.
- Fewer systemic complications (like thrombophlebitis, sepsis, pulmonary edema, and hyponatremia) than IV infusion.
- More comfortable than IV administration
- Has not been shown to cause septicemia or systemic infection
Disadvantages of Hypodermoclysis
- It is slower. The usual rate only 1 mL per minute. Thus about 3 liters can be given in 24 hours spread over two sites.
- It is not a good path for the administration of electrolytes, nutrition additives, and medications
- Edema at infusion site is common
- Risk of local reactions
Indications of Subcutaneous Infusion
Subcutaneous infusion or hypodermoclysis may be indicated for patients who are unable to take adequate fluids orally, who are mildly to moderately dehydrated and in whom it is difficult or impractical to insert an intravenous line.
The main use of subcutaneous fluids has been in geriatric and palliative medicine settings.
It can, however, be used in multiple settings, including the emergency department, hospital, outpatient clinic, nursing home, long-term care, hospice, and home.
It can be used in following situations
- Mild to moderate dehydration/ malnutrition when oral/enteral intake is insufficient;
- No IV access [ not possible, tolerated, or desirable]
- Risk of dehydration when oral intake is not tolerated;
- Bridging technique for patients with difficult IV access while IV access is being attempted;
- Rapid and large fluid infusion required- collapse, shock, severe electrolyte disturbance or major dehydration.
- The patient may be at increased risk of pulmonary congestion or edema, such as severe congestive heart failure.
- Clotting disorders are another contraindication
- Decreased tissue perfusion
- Compromised skin integrity or evidence of skin infection;
- Generalized edema.
Technique of Subcutaneous Infusion
- Solution bag
- Tube with a drip chamber
- 21- or 23-gauge long-tube butterfly needle
- Povidone-iodine solution or alcohol skin preparation
- Sterile occlusive dressing.
Sites of Subcutaneous Fluid Infusion
- Upper chest
- Above the breast
- Over an intercostal space
- Scapular area.
- Outer aspect of the upper arm.
- Select the infusion site.
- Assemble fluid and tubing. Prime line with selected fluid and hyaluronidase if to be used [see below]
- Prepare the site
- Insert needle, bevel up, into subcutaneous tissue at a 45- to 60-degree angle.
- Secure needle and tubing with an occlusive dressing.
- Start the drip at the rate prescribed
Subcutaneous fluids can be delivered by gravity or infusion pump. Fluid is typically infused continuously over 24 hours at a rate of 62 mL/h (approximately 1500 mL in total ) for an average-size adult. With two sites, it could go up to 3 liters.
Needles should be changed every 24 hours to reduce the risk of skin infection. Infusion sets should also be changed but have been left in place for much longer periods without complications [4.7 days]
To date, subcutaneous infusion has typically been used for short-term (≤10 days.) and fluid with osmolarity in the range of 280–300 mOsm/L is expected to be best tolerated.
Usually, normal saline (0.9 percent) is infused, but 0.45 percent saline, one-third saline with two-thirds glucose 5 percent, or 5 percent glucose alone or with normal or half-normal saline have been given.
Hyaluronidase is sometimes administered before or concurrent with subcutaneously infused fluids to increase the rate of absorption. Hyaluronan reduces the viscosity of the hyaluronic acid gel component of subcutaneous tissue and promotes permeability of the connective tissue matrix, leading to enhanced absorption. Few recent studies have doubted its significance.
Adverse Effects of Hypodermoclysis
Local Edema and Other Reactions
Local edema is most common of the adverse effects. Some local edema is normal and typically resolves within hours of stopping the infusion. Erythema, pain, and ecchymosis may accompany.
Continuous pain is rare and may indicate insertion of the needle in the muscle.
Infections are rare.
There is a small risk of blood vessel puncture; however, bleeding is rare in patients with normal coagulation. Any inadvertent IV infusion due to blood vessel puncture should not pose a safety concern as products for subcutaneous infusion are also approved for iv infusion.
This happens due to necrosis of tissue due to inappropriate fluid administered result which may include
- Markedly hypertonic or hypotonic fluids
- High concentration of KCl
The risk of fluid overload is with every type of fluid replacement and not just hypodermoclysis.
This overload may cause regional edema, heart failure, and pulmonary edema.
Slower infusion and infusion of smaller volumes reduce the risk.