Protocols for avoidance of the effects of hyperoxia exist in fields where oxygen is breathed at higher-than-normal partial pressures, including underwater diving using compressed breathing gases, hyperbaric medicine, neonatal care and human spaceflight. These protocols have resulted in the increasing rarity of seizures due to oxygen toxicity, with pulmonary and ocular damage being mainly confined to the problems of managing premature infants. In recent years, oxygen has become available for recreational use in oxygen bars. The US Food and Drug Administration has warned those who have conditions such as heart or lung disease not to use oxygen bars. Scuba divers use breathing gases containing up to 100% oxygen, and should have specific training in using such gases. Classification
The effects of oxygen toxicity may be classified by the organs affected, producing three principal forms:
Central nervous system, characterised by convulsions followed by unconsciousness, occurring under hyperbaric conditions;
Pulmonary (lungs), characterised by difficulty in breathing and pain within the chest, occurring when breathing increased pressures of oxygen for extended periods;
Ocular (retinopathic conditions), characterised by alterations to the eyes, occurring when breathing increased pressures of oxygen for extended periods.Central nervous system oxygen toxicity can cause seizures, brief periods of rigidity followed by convulsions and unconsciousness, and is of concern to divers who encounter greater than atmospheric pressures. Pulmonary oxygen toxicity results in damage to the lungs, causing pain and difficulty in breathing. Oxidative damage to the eye may lead to myopia or partial detachment of the retina.
An acute hemolytic transfusion reaction (AHTR), also called immediate hemolytic transfusion reaction, is a life-threatening reaction to receiving a blood transfusion. AHTRs occur within 24 hours of the transfusion and can be triggered by a few milliliters of blood. The reaction is triggered by host antibodies destroying donor red blood cells. AHTR typically occurs when there is an ABO blood group incompatibility, and is most severe when type A donor blood is given to a type O recipient. Signs and symptoms
Early acute hemolytic transfusion reactions are typically characterized by fever, which may be accompanied by rigors (chills). Mild cases are also typically characterized by abdominal, back, flank, or chest pain. More severe cases may be characterized by shortness of breath, low blood pressure, hemoglobinuria, and may progress to shock and disseminated intravascular coagulation. In anesthetized or unconscious patients, hematuria (blood in the urine) may be the first sign of AHTR. Other symptoms include nausea, vomiting, and wheezing. Causes
The most common cause of acute hemolytic transfusion reaction is ABO incompatibility, which is typically due to human error that results in a recipient receiving the incorrect blood product. Rarely, other blood type incompatibilities can cause AHTR, the most common of which is Kidd antigen incompatibility. Rh, Kell, and Duffy antigen incompatibility have also been implicated in AHTR. Mechanism
Antibodies against A and B blood groups (isohemagglutinins) present in the recipients blood destroy the donor red blood cells.