Hyperkalemia is an elevated level of potassium (K+) in the blood. Normal potassium levels are between 3.5 and 5.0 mmol/L (3.5 and 5.0 mEq/L) with levels above 5.5 mmol/L defined as hyperkalemia. Typically hyperkalemia does not cause symptoms. Occasionally when severe it can cause palpitations, muscle pain, muscle weakness, or numbness. Hyperkalemia can cause an abnormal heart rhythm which can result in cardiac arrest and death.Common causes of hyperkalemia include kidney failure, hypoaldosteronism, and rhabdomyolysis. A number of medications can also cause high blood potassium including spironolactone, NSAIDs, and angiotensin converting enzyme inhibitors. The severity is divided into mild (5.5–5.9 mmol/L), moderate (6.0–6.4 mmol/L), and severe (>6.5 mmol/L). High levels can be detected on an electrocardiogram (ECG). Pseudohyperkalemia, due to breakdown of cells during or after taking the blood sample, should be ruled out.Initial treatment in those with ECG changes is salts, such as calcium gluconate or calcium chloride. Other medications used to rapidly reduce blood potassium levels include insulin with dextrose, salbutamol, and sodium bicarbonate. Medications that might worsen the condition should be stopped and a low potassium diet should be started. Measures to remove potassium from the body include diuretics such as furosemide, potassium-binders such as polystyrene sulfonate and sodium zirconium cyclosilicate, and hemodialysis. Hemodialysis is the most effective method.Hyperkalemia is rare among those who are otherwise healthy. Among those who are  hospitalized, rates are between 1% and 2.5%.
An air embolism, also known as a  gas embolism, is a blood vessel blockage caused by one or more bubbles of air or other gas in the circulatory system. Air can be introduced into the circulation during surgical procedures, lung over-expansion injury, decompression, and a few other causes. Air embolisms may also occur in the xylem of vascular plants, especially when suffering from water stress. Divers can develop arterial gas embolisms as a consequence of lung over-expansion injuries. Breathing gas introduced into the venous system of the lungs  due to pulmonary barotrauma will not be trapped in the alveolar capillaries, and will consequently be circulated to the rest of the body through the systemic arteries, with a high risk of embolism. Inert gas bubbles arising from decompression are generally formed in the venous side of the systemic circulation, where inert gas concentrations are highest, these bubbles are generally trapped in the capillaries of the lungs where they will usually be eliminated without causing symptoms. If they are shunted to the systemic circulation through a patent foramen ovale they can travel to and lodge in the brain where they can cause stroke, the coronary capillaries where they can cause myocardial ischaemia or other tissues, where the consequences are usually less critical. The first aid treatment is to administer oxygen at the highest practicable concentration, treat for shock and transport to a hospital where therapeutic recompression and hyperbaric oxygen therapy are the definitive treatment.