CARDIAC SURGICAL EMERGENCIES
Injuries of the heart fortunately are not common. The heart is protected on all sides by the sturdy rib cage which affords protection from most blunt injuries to the chest. Penetrating wounds, such as from bullets and stabbing, may seriously injure the heart and great vessels. Large wounds may end rapidly in death by hemorrhage into the chest or externally. Smaller wounds may be less rapidly fatal; interference of the cardiac function may be by collection of blood in the pericardial sac, which restricts the heart movements, known as cardiac tamponade.
Early recognition and surgical correction are essential to save life. Operation entails approach to the heart by chest incision, evacuating the blood in the pericardial cavity, and repair of the heart wound. Urgent surgery often results in complete recovery. A great variety of other types of injuries of the heart and great vessels by penetrating objects may occur and many will be correctable by prompt operative intervention.
Cardiac arrest is the sudden cessation of the heart’s action. This may occur under several types of severe circulatory strain such as during major operation under general anesthesia. In this instance facilities are available for cardiac resuscitation, or cardiac massage. As previously mentioned, the brain can tolerate a lack of oxygen for no longer than 3 minutes. If there is prompt recognition of cardiac arrest, immediate opening of the chest and massaging the heart by a squeezing motion will continue the circulation. The heart then resumes its normal pumping action. This emergency operation is augmented by artificial respiration and various drugs. After the heart has resumed its own automaticity, the chest is closed and the circulation continues normally, often allowing completion of the primary operation. This is a dramatic and life-saving operation which rarely is necessitated but can be needed, so that all operating rooms are prepared for such.
HIGH BLOOD PRESSURE
Hypertension, or high blood pressure, is a disease affecting the heart and blood vessels. The main cause lies with the arteries. Blood pressure is controlled by the caliber of the smaller arteries, which may be influenced by several factors. The caliber of these vessels is controlled by the nerve supply to the muscle layer in the blood vessel walls. When the diameter of the vessels is made smaller, the pressure of the blood flow within the vessel is increased, and vice versa. Normally this is automatically controlled to increase the pressure and blood supply to regions of the body according to the oxygen needs with varying activity. In hypertension the arteries remain in constant constriction, thereby increasing the blood pressure throughout the body. In another type the caliber of the arteries may be decreased by hardening of the arteries (arteriosclerosis) with ageing. With some kidney diseases a toxin may cause constriction of the arteries with subsequent hypertension. In some hormonal diseases, such as overactive thyroid, the blood pressure may be increased.
In prolonged hypertension the heart works much harder to force the blood through the constricted arterial tree. Like any other muscle used excessively, the heart muscle enlarges in attempts to supply the tissue demands for oxygen. As the heart enlarges, the valves may be stretched and not sufficiently close the chamber’s outlets; the murmur of valve insufficiency occurs. This further taxes the work of the heart.
Complications of hypertension include the so- called stroke wherein the pressure in a vessel in the skull becomes so great that the vessel ruptures and bleeds into and around the brain.
Treatment of hypertension is most often by medical measures and restricted activity. Drugs are used in attempts to increase the caliber of the spastic blood vessels; these may act on the vessels themselves or on the automatic nerves to the vessels. Some cases of high blood pressure
may be benefited by surgical treatment, which is directed at disrupting the nerve supply to the spastic arteries. The vessels are then no longer constricted and the pressure returns to normal.