High pressure injection injuries are caused by liquids or gasses entering the body from a source, such as a hydraulic hose, exhibiting pressures of 600-12,000 psi. Damage to these hoses or connections can result in pinhole leaks in the equipment, from which the pressurized substance can be ejected at speeds comparable to that of a rifle bullet. Due to the pinhole size of the leak, in many cases, the injury is so small as to be completely painless until delayed tissue damage makes it obvious that something has happened. This is usually when hidden damage below the surface of the skin becomes so severe that it finally appears through the skin, or involves damage to the skin, in addition to the innocuous pinhole which is the only previous external sign of injury.

These types of injuries mainly occur on the hands and fingers, when an operator is handling the high pressure equipment. Even thick leather gloves afford no protection from a sufficiently pressurized source. Once the high pressure material penetrates the skin, it opens up a number of possibilities for damage. Most obvious is the injection of dangerous substances into the bloodstream, such as corrosives or poisons. Most injuries of this type are from high pressure grease guns. High pressure paint guns and diesel injection follow in a very distant second and third. Other materials include water, wax, paint thinner, cement(!), plastic, oil, and hydraulic fluid.

Additionally, the high pressure can result in tissue damage, destroying muscles and tearing blood vessels underneath the skin without anything other than an external pinhole mark where it entered. Even in the best of cases, like any laceration to the skin in non-sterile conditions (such as a job site), there is the risk of secondary bacterial infection, made more insidious by the fact that the victim may not have felt the penetration.

High pressure injection injuries can be extremely dangerous if treatment is not rendered quickly. Due to the potential for internal tissue damage, amputation may be the only option, especially if treatment is delayed for more than six hours, due to hidden gangrene or tissue necrosis or injected material spreading into other areas of the body. Depending on the type of material injected and extent of the damage, the specific treatment can vary widely. In some cases, the injection can be treated like any other puncture wound. In others, surgery may be required to remove the injected material, such as paint, from the body or repair damage to the underlying tissue. The most important thing to remember is that the amount of pain felt at the time of the injury is a poor indicator of how much damage has been done. The true extent of the damage is never obvious in these cases. Seek professional treatment immediately.

To avoid high pressure injection injuries, it is important to inspect equipment thoroughly to ensure there is no damage, such as cracking or holes. Safety attachments such as leak detectors are standard on many types of high pressure equipment, but they must be inspected as well to make sure they are working properly. Never attempt to locate a high pressure leak by passing your hand over the equipment to feel for the leak, and always wear the protective equipment designed for the job.

Medical Uses
Although uncontrolled high pressure injections can cause extreme tissue damage, this same principle is being explored for administering drugs painlessly and without needles. Although such devices have been in use for some time, such as the Jetgun injector used by the military, there are concerns regarding dosage control. Additionally, the process is not quite as painless as the system could potentially be, and is inadequate for people who need regular injections, such as diabetes sufferers. Ideally, the technology will someday reach the point of truly painless injections with accurate dosage control and without fear of transmitting blood-borne diseases between patients.

karma debt adds that, far from being painless, the Jetgun actually hurts worse than a traditional needle injection. The main advantage is its speed. Without a needle, the risk of blood contamination is minimal and the device contains a reservoir of medicine holding many doses. Without needing to swap needles, slowly depress a plunger, or refill a syringe for every injection, it becomes an efficient assembly line procedure.