In the ICU blood tests are usually done at least once a day. They measure such things as how the kidneys are working, cardiac markers (to make sure the heart is healthy) and levels of potassium (K+) and calcium (Ca++) as well as other elements. These are some of the indicators of how the body is working and can show the intensive care specialist how well a patient’s body is coping with their illness. Intra-arterial and intravenous lines (tubes placed in arteries and veins) are often used to monitor the body and, once established, allow rapid, reliable and pain-free access for repeated blood tests. Some conditions will require multiple repeated blood testing every few hours.

Patients with critical illness commonly develop problems with their hearts and circulation. Various factors are involved, some related to the primary disease while others are secondary effects. Problems include changes in: the distribution and volume of body fluid, the condition of the blood vessels and the ability of the heart to pump blood around the body. Treatment for cardiovascular problems may include fluids therapy and a wide range of medicines to control the heart rate, cardiac function and blood pressure.

Respiratory failure occurs when the respiratory system is no longer able to provide enough oxygen requirements or remove enough carbon dioxide from the body. Hypoxia (not enough oxygen is reaching the tissues) may occur unless there are interventions. Large amounts of carbon dioxide may also build up in respiratory failure. Mechanical Ventilation This is the use of a ventilator (sometimes called a life support machine) to do the breathing for a patient experiencing respiratory failure. The ventilator fills the lungs with air, thereby providing oxygen to, and removing carbon dioxide from, the body via the lungs. Usually the ventilator delivers oxygen directly into the airway of the patient. This is done using an endotracheal tube which is a plastic tube that is passed through the mouth into the larynx (the top of the trachea or windpipe). Conscious patients are usually given a medication to make them sleepy or unconscious and a muscle relaxant to help them relax while the tube is inserted. Sometimes people may require a ventilator for a long time. If this is the case a tracheostomy (when an opening is made in the trachea) is performed and the endotracheal tube inserted into the opening. For many very ill patients mechanical ventilation lasting only hours or a few days is enough and, after normal breathing is established, the ventilator can be removed. Unfortunately, a patient whose underlying disease is long-term may become dependent on the ventilator. Their continuing need for mechanical ventilation may be total i.e. 24 hours a day, or it may be limited i.e. only during sleep or occasionally through the day. Noninvasive Positive Pressure Ventilation Some patients may receive ventilation without needing intubation, with the breathing support being delivered via a sealed mask applied to the face. However noninvasive ventilation is useful only in some circumstances and in some patients. Acute Respiratory Distress Syndrome (ARDS) This is a life-threatening condition. It results from any illness that causes widespread inflammation of the lungs. In ARDS, fluid builds up in the air sacs of the lungs (alveoli) and other lung tissue. When the air sacs fill with fluid, the lungs can no longer fill properly with air and the lungs become stiff. This makes breathing difficult. The main symptom of ARDS is severe shortness of breath. This may develop within minutes or gradually over a few days. A doctor may confirm a diagnosis of ARDS by: a chest x-ray arterial blood gas analysis, which measures the oxygen content in blood. Treatment depends on the underlying cause but may include a breathing machine (mechanical ventilation) until the lungs heal.

A nasogastric tube is often inserted at the same time as the endotracheal tube. The nasogastric tube is inserted into the stomach via the nose. This tube ensures that patients receive the necessary nutrition while they are in the Intensive Care Unit.

Kidney (or renal) failure is when a patient’s kidneys are unable to remove wastes and excess fluid from the blood. The likelihood that the kidneys will get better depends on what caused the kidney failure. Kidney failure is divided into two general categories, acute and chronic. In acute (or sudden) kidney failure, when kidneys stop functioning due to a sudden stress, they might be able to start working again. However, when the damage to the kidneys has been continuous and has worsened over a number of years, as in chronic renal failure (CRF), then the kidneys often do not get better. When CRF has progressed to end stage renal disease (ESRD), it is considered irreversible or unable to be cured. There are a number of causes of acute renal failure and in intensive care patients there is often more than one factor that contributes to its development.

Patients with coronary artery disease can have arteries that are blocked or narrowed, meaning blood flow to parts of the heart is poor or non-existent. Coronary artery bypass surgery (CABG) is a surgical procedure that uses veins or arteries from elsewhere in the body e.g. the leg to create a detour around the blocked coronary artery to improve or restore blood flow to the heart muscle. The procedure involves making a cut through the front of the chest and breast bone (sternotomy) so the surgeons can operate directly on the heart. During the procedure the patient's heart is stopped and replaced by an external heart-lung bypass machine. Once the surgery is complete the heart is restarted and the heart-lung machine removed, the breast bone is joined back together and the chest wound sewn up. The operation can take between 3-5 hours.

The heart has four major valves that act like gates to allow blood to flow in the correct direction. In some disease processes the valve can become narrow (stenosis) which means less blood can flow through it. The valve can also become ‘leaky’ which means the blood can flow both forwards and backwards. Both problems cause difficulties with blood flow and therefore the ability of the heart to function effectively. These valves can be replaced, using an artificial valve or a valve from a human donor or a pig. The procedure involves making a cut through the front of the chest and breast bone (sternotomy) so the surgeons can operate directly on the heart. During the procedure the patient's heart is stopped and replaced by an external heart-lung bypass machine. Part of the heart is then opened and the valve repaired or replaced. Once the surgery is complete the heart is restarted and the heart-lung machine removed, the breast bone is joined back together and the chest wound sewn up. The operation can take between 3-5 hours.

Congenital heart disease occurs from birth and can include structural defects and heart rhythm problems. the heart can have difficulty pumping efficiently because it is not completely developed. In some situations surgery can be performed on the young baby, infant or child but for others the surgery is left until adulthood. Congenital heart surgery can involve: repairing the abnormality e.g. repairing defects in the internal walls of the heart with stitches or a patch made from either the patient's own tissue or from an artificial source or a procedure that will make the patient more comfortable but that will not necessarily correct the defect e.g. inserting a tube to connect the major vessels to increase blood flow to the lungs.

An aneurysm is a weakness in the wall of a vessel that can cause a large bulging area. In an aortic aneurysm this bulge is in the aorta which is the main vessel that takes oxygenated blood to the body. Surgery can be performed to stop the aneurysm bursting. The procedure involves opening the chest allowing the part of the aorta with the aneurysm to be removed and replaced with an artificial graft. An alternative procedure leaves the chest closed and an artificial tube (stent) is inserted so the blood flows through the stent and bypasses the aneurysm. This procedure involves small incisions usually in the groin / thigh area.

Heart or lung transplant surgery can be performed on patients with end stage heart or lung failure with poor life expectancy. Often other treatments have already been considered or attempted prior to recommendation. Some patients are not suitable for transplant surgery. In heart surgery the patient is placed on a heart-lung bypass machine. The surgeon then removes the faulty heart, leaving part of the main vessels to attach the new donor heart to The new heart is placed where the old one was and reattached to the blood vessels. The new heart is restarted and the heart-lung bypass machine removed. Finally the chest is closed and sewn back together. The most common procedure for lung transplants is a single lung transplant. Here the faulty lung is collapsed, the blood vessels in the lung are tied off and the lung is removed at the bronchial tree. The donor lung is placed in the chest cavity, the blood vessels reattached and the lung re-inflated.

The ECMO machine is similar to the heart-lung bypass machine but it is used outside the operating theatres. The machine takes over the work of the heart and lung when the heart and lungs are so severely affected that they cannot function properly. The blood is pumped around an external circuit and through a membrane that removes carbon dioxide and adds oxygen, essentially acting like a lung. The aim of this therapy is to rest the body; it is not a treatment.

The ventricular assist device (VAD) is a mechanical device that can be used to partially or completely replace the function of a failing heart. The purpose of the device is to replace or assist cardiac function temporarily, although some devices are being designed that can be implanted permanently. Most patients using the devices are awaiting a heart transplant.

This involves the removal of a small, localised area of diseased tissue e.g. tuberculosis near the surface of the lung. Because the area is small, pulmonary structure and function are relatively unchanged after healing. Chest drainage is used post-operatively.

The removal of one or more lung segments (a bronchiole and its aveoli) when the disorder is limited to one or more segments. The remaining lung tissue over-expands to the fill the space of the removed segment. There is often a major air-leak and chest drainage is used post-operatively.

Removal of the entire lobe of a lung when there is e.g. a tumour, lung abscess or bleb. This also includes lymph node removal. After lobectomy some non-pathologic emphysema occurs. Remaining lung tissue over-expands to fill in the portion previously occupied by the resected lung. Chest drainage is used post-operatively.

Removal of an entire lung, e.g . in the presence of bronchogenic cancer. Once the lung is removed, the involved side of the thoracic cavity is an empty cavity. To reduce the size of this cavity, the phrenic nerve is severed or crushed on the affected side; this paralyses the diaphragm in an elevated position. Blood and serosanguineous fluid is allowed to accumulate in the cavity. This eventually consolidates, preventing mediastinal shift of the heart and remaining lung. Chest drains are placed post-operatively. These remain clamped.

Removal or the stripping off of a thick fibrous membrane (scar tissue) that develops over the visceral pleura. This constricts the lung and interferes with lung expansion.

This operation is to bypass diseased blood vessels above or below the knee. To bypass the blocked vessel, blood is redirected through either a healthy blood vessel that has been transplanted or a man-made graft material that is sewn to the diseased artery. Whenever possible the surgeon will choose an existing piece of vein taken from the same leg.

This procedure is performed to relieve lower limb ischaemia (poor blood supply). A bypass is created from the axillary artery under the arm to the femoral artery in the groin using a vascular prosthesis (synthetic graft) or a section of the saphenous vein.

The carotid artery is opened and plaque/blood clots that are obstructing the blood flow are removed.