What are the causes of venous blisters

Air embolism

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Signs and symptoms

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In practice

Symptoms include:

In divers

Symptoms of arterial gas embolism include:
  • unconsciousness
  • Apnea
  • Vertigo
  • cramps
  • Tremors
  • Loss of coordination
  • Loss of control over bodily functions
  • deafness
  • paralysis
  • Extreme fatigue
  • Weakness in the extremities
  • Areas of abnormal sensation
  • Visual anomalies
  • Hearing abnormalities
  • Changes in personality
  • Cognitive impairment
  • Nausea or vomiting
  • Bloody sputum
  • Symptoms of other consequences of lung overextension, such as pneumothorax, subcutaneous, or mediastinal emphysema, may also be present.

Caused

surgery

During surgery and other medical procedures, small amounts of air often accidentally get into the bloodstream (e.g., a bladder entering an intravenous fluid line), but most of these air embolisms enter the veins and stop at the lungs, causing a venous air embolism, the showing any symptoms is very rare.

decompression sickness

A gas embolism is a diving disease that occurs in underwater divers who inhale gases at ambient pressure and can occur in two different ways:
  • Pulmonary barotrauma: Air bubbles can enter the bloodstream as a result of gross trauma to the lining of the lungs after a rapid ascent while holding the breath; the air held in the lungs expands to the point where the tissue ruptures (pulmonary barotrauma). This is easy to do because the lungs give little warning through pain until they burst. The diver usually comes to the surface in pain and fear and may foam or spit blood. Pulmonary barotrauma is usually obvious and can be very different from decompression sickness.
  • Decompression sickness (DCS): Inert gas bubbles form in the bloodstream when the gas dissolved under pressure in the blood during a dive is not given enough time to eliminate it when it is in solution. Symptoms can be subtle and imperceptible and can continue to develop for some time after surfacing.

Ventilator induced pulmonary barotrauma

Lung trauma can also cause air embolism. This can happen after a patient has been put on a ventilator and air is forced into an injured vein or artery, resulting in sudden death. Also, holding your breath when ascending from scuba diving can similarly force air into the pulmonary arteries or veins due to the pressure difference.

Direct injection

In clinical procedures, air can be accidentally injected directly into a vein or artery. The improper use of a syringe to meticulously remove air from the vascular tubes of a hemodialysis circuit can allow air to enter the vascular system. Venous air embolism is a rare complication in diagnostic and therapeutic procedures that require catheterization of a vein or artery. If significant embolism occurs, the cardiovascular, pulmonary, or central nervous systems can be affected. Interventions to remove or mitigate the embolism may include procedures to reduce the size of the bladder or remove air from the right atrium.

Other

There have been rare cases of air embolism caused by air entering the bloodstream from the uterus or by tears in the female genitals. The risk seems to be greater during pregnancy. Cases have been reported resulting from attempts to terminate pregnancy by injection. These appear to have been due to damage to the placenta, which allowed air to enter the bloodstream.

Risk factors

The patented foramen ovale in underwater divers is considered a risk factor for arterial gas embolism due to a shunt of otherwise asymptomatic venous bladders into the systemic arteries.

mechanism

An air embolism can occur whenever a blood vessel is open and there is a pressure gradient that favors the entry of gas. Since the circulatory pressure in most arteries and veins is higher than atmospheric pressure, air embolism is not common when a blood vessel is injured. In the veins above the heart, such as in the head and neck, the venous pressure can be less than atmospheric pressure, so that air can flow in if there is an injury. This is one reason surgeons need to be extra careful during brain surgery and why the head of the bed is tilted down when a central venous catheter is inserted or removed from the veins of the carotid or parotid artery. When air enters the veins, it travels to the right side of the heart and then into the lungs. This can narrow the blood vessels in the lungs, which increases the pressure in the right side of the heart. If the pressure rises high enough in a patient who is among the 20 to 30% of the population with a patented foramen ovale, the gas bubble can travel to the left side of the heart and on to the brain or coronary arteries. Such bubbles are responsible for the most serious symptoms of gas embolism. A venous or pulmonary air embolism occurs when air enters the systemic veins and is carried to the right side of the heart and from there into the pulmonary arteries, where it can lodge and block or reduce blood flow. Gas in the venous circuit can cause heart problems by blocking pulmonary circulation or creating an air lock that increases central venous pressure and decreases pulmonary and systemic arterial pressure. Experiments on animals show that the amount of gas required for this is quite variable. Case reports in humans suggest that injecting more than 100 mL of air into the venous system at a rate greater than 100 mL / s can be fatal. Very large and symptomatic amounts of venous air embolism can also occur during rapid decompression in severe diving or decompression sickness, where it can impair the circulation in the lungs and lead to shortness of breath and hypoxia. A gas embolism in a systemic artery known as a arterial gas embolism(AGE) is a more serious issue than in a vein, as a gas bubble in an artery can directly stop blood flow to an area supplied by the artery. The symptoms of 'AGE' depend on the area of ​​blood flow and can include stroke in cerebral arterial gas embolism (CAGE) or heart attack if the heart is affected. The amount of arterial gas embolism that causes symptoms depends on the location - 2 mL of air in the cerebral circulation can be fatal, while 0.5 mL of air in a coronary artery can cause cardiac arrest.

Prevention and precaution

If an open foramen ovale (PFO) is suspected, an echocardiographic examination can be performed to diagnose the defect. In this test, very fine bubbles are introduced into a patient's vein by stirring saline in a syringe to create the bubbles and then injecting them into a vein in the arm. A few seconds later, these bubbles will be clearly visible on the ultrasound image as they travel through the patient's right atrium and right ventricle. At this point, the bubbles can be watched directly as they traverse a septal defect, or a patented foramen ovale can be temporarily opened by asking the patient to perform the Valsalva maneuver while the bubbles travel through the right heart - an action , which opens the foramen flap and shows how the bubbles get into the left heart. Such bubbles are too small to cause harm when tested, but such a diagnosis can alert the patient to potential problems caused by larger bubbles that form during activities such as underwater diving, where bubbles can grow during decompression. A PFO test can be recommended for divers who want to expose themselves to a relatively high decompression load during technical deep diving.

diagnosis

As a general rule, any diver who has inhaled pressurized gas at any depth and surfaced unconscious shortly after surfacing or showing neurological symptoms within about 10 minutes of surfacing will have arterial gas embolism. The symptoms of arterial gas embolism may be present, but they can be masked by environmental factors such as hypothermia or pain from other obvious causes. A neurological examination is recommended if there is a suspicion of an overstretch injury to the lungs. Symptoms of decompression sickness may look very similar to and be confused with symptoms of arterial gas embolism, but treatment is essentially the same. Distinguishing between gas embolism and decompression sickness can be difficult for injured divers, and both can occur at the same time. In many cases, history of decompression sickness can be eliminated and the occurrence of symptoms of other pulmonary overextension injuries would increase the likelihood of gas embolism.

treatment

A large air bubble in the heart (as can occur in certain trauma where the air can freely access large veins) leads to a constant "machine noise". It is important to immediately position the patient in the Trendelenburg position (head down) and on the left side (left lateral pressure ulcer position). The Trendelenburg position keeps a left ventricular air bubble away from the coronary artery ostia (which are located near the aortic valve) to prevent air bubbles from entering the coronary arteries and clogging them (which would cause a heart attack). The positioning of the left lateral pressure ulcer helps trap the air in the nondependent segment of the right ventricle (where it is more likely to remain rather than entering and occluding the pulmonary artery). The left lateral bedsore position also prevents air from passing through a potentially open foramen ovale (present in up to 30% of adults) into the left ventricle, from where it could then embolize into the distal arteries (which may cause occlusive symptoms such as a Stroke). The administration of high percentage oxygen is recommended for both venous and arterial air embolism. This is supposed to counteract ischemia and accelerate the reduction in bubble size. In a venous air embolism, the Trendelenburg position or left lateral positioning of a patient with an airlock obstruction of the right ventricle can move the air bubble in the ventricle and allow blood to flow under the bladder. Hyperbaric therapy with 100% oxygen is recommended for patients with clinical features of arterial air embolism because it accelerates the removal of nitrogen from the bladders by solution and improves tissue oxygenation. This is particularly recommended in the case of cardiopulmonary or neurological involvement. Early treatment has the greatest benefit, but it can be effective as early as 30 hours after the injury.

Treatment of divers

Oxygen first aid treatment is useful for suspected gas embolism or for divers who have made rapid ascents or missed decompression stops. Most fully closed-circuit resuscitators can deliver sustained high concentrations of oxygen-rich breathing gas and could be used as an alternative to open-circuit oxygen-only breathing apparatus. However, pure oxygen from an oxygen cylinder through a non-rebreathing mask is the optimal way to provide oxygen to a patient with decompression sickness. Recompression is the most effective, albeit slowest, treatment for gas embolism in divers. Usually this is done in a recompression chamber. With increasing pressure, the solubility of a gas increases, whereby the bubble size is reduced by accelerated absorption of the gas into the surrounding blood and tissue. In addition, the volumes of the gas bubbles decrease in inverse proportion to the ambient pressure, as described by Boyl's law. In the overpressure chamber, the patient can reach a depth of 18 msw at ambient pressure. Breathe 100% oxygen. Under hyperbaric conditions, oxygen diffuses into the bladder, displacing the nitrogen from the bladder and into the solution in the blood. Oxygen bubbles are more easily tolerated. The diffusion of oxygen in blood and tissue under hyperbaric conditions supports areas of the body that can no longer be supplied with blood if the arteries are blocked by gas bubbles. This will help reduce ischemic injuries. The effects of hyperbaric oxygen also counteract the damage that can occur during reperfusion of previously ischemic areas; this damage is mediated by leukocytes (a type of white blood cell).

Complications

High incidence of relapse after hyperbaric oxygen treatment due to delayed cerebral edema.

Epidemiology

With regard to the epidemiology of air embolism, it is noted that the intraoperative Period has the highest incidence. For example, the incidence of VAE in neurological cases is up to 80%, and the incidence of OBGYN surgery can increase to 97% in VAE (vascular air embolism). In divers, the incidence rate is 7 / 100,000 per dive.

Other organisms

Air embolisms generally occur in the xylem of vascular plants because a drop in hydraulic pressure leads to cavitation. The falling hydraulic pressure is caused by water stress or physical damage. A number of physiological adjustments are made to prevent and recover from cavitation. The cavitation can be prevented from spreading through the narrow pores in the walls between the vessel elements. The herbal xylem juice can be diverted through connections around the cavitation. Water loss can be reduced by closing the stomata of the leaves to reduce perspiration, or some plants create positive xylem pressure from the roots. When the xylem pressure increases, the cavitation gases can dissolve again.
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