Wound irrigation is the steady flow of a solution across an open wound surface to achieve wound hydration, to remove deeper debris, and to assist with the visual examination. The irrigation solution is meant to remove cellular debris and surface pathogens contained in wound exudates or residue from topically applied wound care products. Compared to swabbing or bathing, wound irrigation is considered to be the most consistently effective method of wound cleansing. 
Normal wound healing is characterized by 3 interrelated phases: inflammatory, proliferative or fibroplastic, and remodeling. In normal wound healing, infectious microorganisms, foreign debris, and necrotic tissue are removed from the wound during the inflammatory phase due to vascular and cellular responses to trauma. However, weaknesses in the body’s inflammatory response can cause deficits in its ability to overpower surface microorganisms. This can lead to delayed angiogenesis and granulation tissue formation, as well as infection. Contaminating microorganisms can upset collagen synthesis and modify matrix metalloproteinases, leading to anoxia and impeding neutrophil and macrophage function.
Combined with debridement, irrigation is a critical step in facilitating progression from the inflammatory to proliferative phase of wound healing by removing debris that can impede the healing process. When performed properly, wound irrigation can aid in wound healing from the inside tissue layers outward to the skin surface. It may also help prevent premature surface healing over an abscess pocket or infected tract.  The goal of irrigation is to clean the wound while avoiding trauma to wound bed and minimizing risk of driving bacteria further into the wound bed.
Key considerations - Selecting an irrigation solution
Choosing an appropriate solution is a critical step in wound irrigation. Solutions intended for topical use include topical cleansers, antibiotics, antifungals, antiseptics and anesthetics. Ideally, an irrigant should be isotonic, nonhemolytic, nontoxic, transparent, easy to sterilize, and inexpensive. Unfortunately, such a solution does not yet exist. Current literature generally favors use of normal saline. Many antiseptics and antibiotics have been employed, but the ideal additive is the subject of debate. Cytotoxicity of the solution should certainly be considered. In particular, antiseptic solutions, such as povidone-iodine, chlorhexidine, and hydrogen peroxide, may be toxic to tissues and may negatively influence acute wound healing. Some conventional topical irrigants are discussed below.
Normal saline is isotonic and the most commonly used wound irrigation solution due to safety(lowest toxicity) and physiologic factors. A disadvantage is that it does not cleanse dirty, necrotic wounds as effectively as other solutions. Similar wound infection rates have been reported with potable tap water versus saline in adult and pediatric populations. [3, 4] It is important to note the date of opening a saline container, as bacterial growth in saline may be present within 24 hours of opening the container.
Prepared by distillation, sterile water is nonpyrogenic and contains no antimicrobial or bacteriostatic agents or added buffers. It is often used in irrigation, particularly in developing countries, as a less expensive alternative to isotonic saline. Sterile water is hypotonic and may cause hemolysis and will be readily absorbed by the tissues during surgical procedures; therefore, its use under such conditions is not recommended. Water toxicity may result when excess volumes are used.
Potable water is recommended in the event that normal saline or sterile water are not available. Its use is particularly attractive in austere environments. In fact, a few studies have shown potable water to be as effective at reducing bacterial counts as normal saline.
Commercial wound cleansers
Commercial wound cleansers are increasingly used in irrigation. Detergent irrigation is meant to remove, rather than kill, bacteria and has seen promising results in animal models of the complex contaminated musculoskeletal wound.  Due to the surfactant content in cleansers, less force is required to remove bacteria and cellular debris. Thus, cleansers may be best suited for wounds with adherent cellular debris or in dirty, necrotic wounds. Trigger sprays can help direct the cleanser more effectively and safely. Cleansers typically contain preservatives to slow growth of bacteria, molds, and fungi, and extend product shelf life.
Povidone iodine is a broad spectrum antimicrobial solution effective against a variety of pathogens including Staphylococcus aureus. However, similar wound infection rates have been reported in adult and pediatric populations with saline irrigation versus 1% povidone-iodine. [3, 4] A disadvantage is its cytotoxicity to healthy cells and granulating tissues. The solution dries and tends to discolor skin. It may also cause local irritation to the periwound skin.
A 3% solution of hydrogen peroxide is a commonly used wound antiseptic. However, few studies report on its efficacy in wound healing and as an antiseptic, and its use remains controversial. While some studies have shown hydrogen peroxide to be cytotoxic to healthy cells and granulating tissues, other animal and human studies have shown no negative effect on wound healing. [6, 7] Several studies have also shown hydrogen peroxide to be ineffective in reducing bacterial count.  The American Medical Association summarized that the effervescing cleansing action of hydrogen peroxide may act as a chemical debriding agent to help lift debris and necrotic tissue from the wound surface when used at full strength  If used, irrigation with normal saline after full-strength hydrogen peroxide use is recommended. Use of hydrogen peroxide is not recommended in wounds with sinus tracts.
Sodium hypochlorite (ie, Dakin’s solution) has been classically used in pressure ulcers with necrotic tissue to help control infection. Sodium hypochlorite is known to have a bactericidal effect against most organisms commonly found in open wounds. It is occasionally used over cancerous growths to control bacteria and minimize odor. However, the solution is known to be cytotoxic to healthy cells and granulating tissues, and its use is not recommended for periods longer than 7-10 days.
Key considerations - Selecting method of solution delivery to the wound
The ideal irrigation technique and pressure required for optimal outcome are still undetermined in the literature.  Equipment used for irrigation includes bulb syringes, piston syringes, pressure canisters, whirlpool agitator, whirlpool hose sprayer, irrigation fluid in plastic containers with a pour cap or nozzle, and pulsed lavage (eg, jet lavage, mechanical lavage, pulsatile lavage, mechanical irrigation, high-pressure irrigation).
Continuous irrigation is the uninterrupted stream of irrigant to the wound’s surface. Pulsed irrigation is the intermittent or interrupted pressurized delivery of an irrigant, typically measured by the number of pulses per second. Power-pulsed lavage is a wound irrigation system that uses an electrically powered pump system to deliver a high volume of irrigation solution under pressure. Outcomes of pulsed versus continuous pressure appear to be similar.
Advantages of pressurized canisters compared to traditional methods of irrigation include speed, simplicity and cost-effectiveness. Semirigid ampoules and pressurized canisters also allow practitioners to irrigate wounds without the risk of needle-stick injuries. Disadvantages include the reliability of canisters and difficulties in warming contents to consistent ambient temperature.
Key considerations - Choosing a sufficient pressure
The amount of pressure used in wound irrigation appears to be a determining factor in successful wound cleansing, yet a paucity of well-supported literature exists regarding optimal irrigant pressure. High pressure is often used to describe acute wound irrigation; however, pressure parameters have varied within this definition. For the purposes of this discussion, high-pressure lavage, usually performed using syringes and needles, is 35-70 pounds per square inch (psi), and low-pressure irrigation is 1-15 psi, as defined by the American College of Surgeons. 
Seminal studies of high-pressure pulsating jet lavage (70 psi) indicated it is more effective in reducing bacterial populations and removing necrotic tissue and foreign particles versus bulb syringe and other low-pressure systems. [11, 12] However, especially in chronic wounds, high pressure irrigation systems have been shown to damage granulation and epithelial tissue or cause discomfort to the patient. In all wounds, high pressure may also drive bacteria into deeper compartments, causing increased risk of infection, particularly in highly vascularized areas such as the scalp and face.
Complications of high-pressure irrigation in acute bone and joint surgery include visibly damaged bone, intramedullary seeding of bacteria, and delayed healing of the fracture by lavage of the fracture zone.  With high-pressure lavage, a possibility exists of pushing surface contaminants into the mucosal epithelium.
Original Agency for Health Care Policy and Research (AHCPR) guidelines describe safe and effective irrigation pressures as being 4-15 psi, based on a series of different studies. [12, 14, 15] Pressures greater than 15 psi may cause wound trauma and drive bacteria further into wounds. These authors recommend using a 35-mL piston syringe with an 18-gauge or 19-gauge tip for irrigation. A syringe with an attached 19-gauge needle typically delivers an output pressure range of 11-31 psi; however, the end pressure that reaches the wound could be as low as 8 psi. [16, 17]
Studies suggest that pressures of 8-12 psi are strong enough to overcome adhesive forces of bacteria; [3, 17] however, maintaining consistent pressure across the tissue beds has long been challenging to control. Owens et al concluded from a controlled animal study that use of a low-pressure device and saline solution to irrigate wounds is the best choice in maintaining bacteria clearance longer than 48 hours.  Earlier versus later (3 hours versus 12 hours) irrigation in a contaminated wound model has also been reported to result in superior bacterial removal. 
Although current evidence appears to support greater advantages with low-pressure wound irrigation, pressures lower than 4 psi have been found to be insufficient in removing surface pathogens and debris. Needle and syringe-generated pressures of 13 psi have been found to be more effective in reducing inflammation and infection when compared to a bulb syringe.  Manually squeezing punctured containers of irrigation fluid is inadequate for pressure irrigation. In general, wound soaking without suction is not effective in cleaning contaminated wounds and may increase wound bacterial counts.
In summary, the benefits of higher pressures in reducing bacterial count, dirt, and tissue debris in heavily contaminated wounds may outweigh the risk of tissue injury. In relatively clean wounds, the potential damage of tissue resulting from high-pressure irrigation may outweigh the benefits. 
Key considerations - Using sufficient volume
Increased volume improves wound cleansing to a point, but optimal volume in wound irrigation remains largely understudied. Volumes of 50-100 mL per centimeter of laceration length or per square centimeter of a wound are commonly reported in the literature. [3, 20]
Importantly, irrigation volume should be determined according to wound characteristics and degree of contamination. In the case of more contaminated wounds, the wounds should be irrigated until all visible debris is removed. Copious amounts of potable tap water or saline should be used for irrigation and decontamination of chemical burns. 
Key considerations - Precautions and protection against splashback
Irrigation, particularly high pressure, can splash and spread bacteria to surrounding areas and people. The use of a plastic shield at the end of the irrigating syringe reduces this hazard. Where needed, a face shield, mask, and protection over scrubs is advised. IV sites and other open areas should be protected from splashing.
Most wounds should be irrigated initially and at each dressing change. All wound surfaces should be irrigated, which may require opening wound edges and flaps for exposure. Wounds should be irrigated again upon re-examination.
Precautions and contraindications
Pulsed lavage should not be performed over exposed blood vessels, nerves, tendons, or bone.
Pulsed lavage should not be performed in the presence of active, profuse bleeding (precautionary measures for patients on anticoagulation medication).
Improper technique may harm the wound bed.
Patients with sensory impairment are unable to provide accurate feedback needed to guide the clinician if improper technique is used.
Hydrodebridement is the synchronous application of an irrigant in tandem with debridement. Particularly in the presence of thick exudate, slough, or necrotic tissue, hydrodebridement may aid in cleansing and mechanical debridement. Both low-pressure and high-pressure methods of hydrodebridement have been used to optimize the effects of debridement, reduce bioburden, and manage exudate—all integral parts of wound bed preparation.
An emerging application of low-pressure hydrodebridement is in tandem with negative-pressure wound therapy (NPWT). Some NPWT systems are equipped with technology that allows automatic instillation of topical solutions to be delivered and removed from the wound site during NPWT. This technology is indicated for patients who would benefit from vacuum-assisted drainage and controlled delivery of topical wound treatment solutions and suspensions over the wound bed. NPWT can be used with a range of solutions intended for topical use, including cleansers, antibiotics, antifungals, antiseptics, and anesthetics. Regular instillation of topical solutions during NPWT can assist with wound cleansing, irrigation, pain, and removal of infectious material.  See the image below.
Instilling solutions with NPWT increases the viscosity of the wound fluid and allows more efficient removal through the reticulated open-cell foam dressing and into the canister. Solutions are delivered continuously or at timed intervals, and are gravity fed, or intermittently pumped into the wound, depending upon the NPWT system. Wounds with significant debris and bacterial contamination can be irrigated when needed at increased pressures (fluid delivered at 8-12 psi such as with a 35 mL syringe and a 19-gauge angiocatheter) during NPWT dressing changes.
NPWT with solution instillation has been advocated in cases of diffuse or extensively treated osteomyelitis, large areas of postdebrided exposed bone or joint, and in cases of critical bacterial colonization levels as an alternative to antibiotic-impregnated beads when appropriate.  Anecdotal evidence suggests topical solution instillation may enhance the efficacy of NPWT in cases of high levels of exudate and slough content, as well as acute traumatic wounds or wounds acutely debrided due to infected hardware or soft tissue. [23, 24] However, large controlled studies are needed to substantiate the effects of solution instillation with NPWT.
Although topical antibiotics are commonly used in wound infection prophylaxis and treatment, well-controlled research supporting optimal topical antibiotic treatment regimens is lacking. In addition, risk of antibiotic resistance is an ongoing concern in the practice of topical antibiotic use. The overall effectiveness of topical antibiotics is a subject of hot debate that is beyond the scope of this article. The authors support short-term use of appropriate topical antibiotic solutions, such as vancomycin, bacitracin, and silver-based solutions (silver nitrate) with NPWT in wounds that require antimicrobial therapy for management. Continuous hydrocleansing has been reported to impede formation of biofilms that allows bacteria to adhere to wound surfaces.  Evidence suggests these biofilms gain resistance to antimicrobial treatments over time and that selected topical antibiotics may be most effective within 24 hours of sharp debridement. 
Solutions that contain hydrogen peroxide or alcohol should not be used with NPWT reticulated open-cell foam. Also, according to manufacturer’s guidelines, instillation of fluids into thoracic or abdominal cavities is not recommended due to the potential risk of altered core body temperature and fluid retention within the cavity. In addition, topical wound solutions should not be infused into wounds with unexplored tunnels or undermining because the solutions may enter into unintended cavities.
High-pressure hydrodebridement, or hydrosurgery, combines lavage and sharp debridement instrumentation. This technology is used to soften and mechanically debride devitalized tissue, often prior to reconstruction. Modern hydrosurgical devices project a high-velocity, razor-thin saline jet stream, capable of cutting tissue, across an operating window into an evacuation canister, creating a localized vacuum. The saline beam is aimed parallel to the wound so that the cutting mechanism is a highly selective form of tangential excision. Suction allows the surgeon to hold and cut targeted tissue while aspirating debris from the site. In this way, selective debridement of necrotic and damaged tissues is facilitated, and viable and peripheral tissue is spared.
Advantages of hydrosurgical tools are ease of use, precision, speed and safety in wound cleansing. Excision of contoured areas, web spaces, and facial structures may be improved with the technology. Hydrosurgery is most beneficial when the tissue to be removed is softer than the tissue that should remain intact. For example, debriding desiccated eschar in pressure sores covered with dry eschar is not effective.  Results of one study showed a significant increase in bacterial air contamination following debridement with a hydrosurgery tool; appropriate precautions should be taken.  Further controlled studies are required to investigate the cost-effectiveness of high pressure hydrodebridement in wound management.
When appropriate, the wound bed should be anesthetized before irrigation.
Wound decontamination, including brushing off any dry chemicals, should also be performed prior to irrigation.
Numerous wound irrigation techniques exist. Following is the equipment needed for syringe irrigation:
Waterproof trash bag
Gown, if indicated
Sterile water or normal saline solution
Soft rubber or plastic catheter
Materials as needed for wound care
Sterile irrigation and dressing set
Commercial wound cleaner
35-mL piston syringe with 19-gauge needle or catheter
Skin protectant wipe
Prepare irrigation solution and irrigation delivery device in the patient’s room. Using any solution that has been opened longer than 24 hours is not recommended. Place a waterproof trash bag near the patient’s bed. Turn down the top of the trash bag, creating a cuff, to provide a wide opening and prevent instruments or gloves from touching the bag’s edge.
Position the patient so the solution runs from the upper end of the wound downward. Place a waterproof bed pad and clean basin or irrigating pouch under the area to be irrigated.
Technique is as follows:
Assess the patient’s condition and identify any allergies, specifically to povidone-iodine or other topical solutions or medications.
Assess the wound, including the amount and character of drainage and the size and condition of the wound and surrounding tissue.
Irrigation should be performed using strict aseptic technique.
Wash hands. If necessary, wear a protective gown. Put on clean gloves.
If applicable, remove soiled dressing and discard with gloves.
Put on goggles, if needed.
The following is specific to piston syringe technique:
Hold the filled syringe just above the top edge of the wound and gently instill fluid into the wound, slowly and continuously until the syringe is empty. Be sure the solution flows from the clean to dirty area of the wound. Use enough force to flush out debris, but do not squirt or splash fluid. Irrigate all portions of the wound. Do not force solution into the wound’s pockets. Repeat irrigation procedure until the prescribed amount of solution is administered or the solution draining from the wound is clear.
Remove and discard disposable irrigation equipment in trash bag.
Clean the peri-wound area with normal saline solution; wipe intact skin with skin protectant wipe. Gently pat dry the wound’s edges, unless the wound should be covered with a wet-to-dry dressing (dry only surrounding skin). Work from cleanest to most contaminated part of wound.
The patient should be positioned comfortably to allow further drainage into the basin.
Apply dressings as ordered. 
Record the date and time of irrigation, amount and type of irrigant, appearance of the wound, sloughing tissue or exudate, amount of solution returned, skin care performed around the wound, dressings applied, and the patient's tolerance of the treatment.
Wound irrigation may cause excoriation and increased pain. Pressures over 15 psi may traumatize the wound and force bacteria back into the tissue.
Nearly all wounds are at risk for compromised healing owing to excessive exudation, edema, contaminants, and the presence of inflammatory mediators. Compromised wounds have the potential to develop complications, such as infection, which may lead to delayed wound healing, prolonged hospitalization, and more frequent readmissions.
It is generally believed that the wound advances from contamination to colonization when the bacteria on the wound's surface begin to replicate and increase their metabolic activity. Heavy bacterial bioburden increases the metabolic requirements, stimulates a proinflammatory environment, and encourages the in-migration of monocytes, macrophages, and leukocytes—all of which can negatively impact wound healing. Bacteria also secrete harmful cytokines, which can lead to vasoconstriction and decreased blood flow.
Thus, controlling or preventing infections is essential for the normal wound healing process to occur. Therefore, adequate management of these wounds with the help of negative pressure wound therapy irrigation can further enhance patient outcomes.