Intensive Care and Life Support

Intensive care is defined as the medical treatment of patients with serious reversible conditions, generally with a significant element of respiratory failure, who are judged to be capable of recovery.

The Crimean War (1853-1856) saw the start of modern nursing, pioneered by Florence Nightingale. The traditional hospital ward, with beds in rows alongside the walls was (and still is) known as a Nightingale ward. A system of progressive patient care was established in which the sickest patients were segregated and placed in the area immediately adjacent to the nursing station. In the 1940s and 1950s special areas were developed for the care of, for example, postoperative thoracic surgical or neurosurgical patients.

By the 1960s, the concept of general intensive care, or therapy, units evolved, often from anesthetist-led postoperative recovery units. The first general intensive therapy units (ITUs) were opened in the U.K. in 1966. At about the same time, coronary care units (CCUs), generally for postoperative heart surgery patients, were opened in the U.S. and the U.K. Since hospitals had been traditionally organized under a somewhat rigid hierarchical structure, the concept of multidisciplinary care with physicians, anesthetists, nurses, physiotherapists and biochemists working together was a novel one.

The impetus for these units included:
1. The increasing ability to keep patients alive using ventilators and other mechanical devices
2. Increasing understanding of the metabolic changes occurring in critical illness and the ability to monitor these changes
3. The means to treat them
4. The improvement in anesthesiology techniques that allowed complex surgery to be performed on very ill patients

Management of the systemic inflammatory response syndrome, previously referred to under the generic term ‘‘shock,’’ gradually became better understood. Treatment of acidosis, fluid and blood replacement, and cardiovascular support with medication became the basis of intensive care. Some of the advances made possible by the isolation and treatment of patients in these specialized high technology environments define intensive care and life support.

Ventilators. The poliomyelitis epidemics of the 1930s had seen wards of patients ‘‘breathing’’ with the help of ‘‘iron lungs.’’ The polio virus affected the neurological system and caused paralysis of the muscles (thus the early name of the disease, infantile paralysis), including those that make it possible to breathe.

The iron lung was a bulky and cumbersome device: the patient’s upper body was inside an airtight chamber in which alternate negative and positive pressures were created by a system of bellows, enabling the influx and expulsion of air from the lungs. The machine was developed by Harvard University engineer Philip Drinker and Louis Shaw in 1928. Because of iron lungs, innumerable lives were saved during the polio epidemics of the 1930s and 1940s.

The supervision of these patients was almost entirely in the hands of medical students who worked a shift system. Although outdated by the development of positive pressure ventilators after World War II, 300 of these devices were amazingly still in use in the U.S. in 1985. The success of this rather primitive equipment was all the more remarkable when it is remembered that the modern, noninvasive techniques of oximetry (the measurement of blood oxygen levels) had not been invented.

In 1946 a ‘‘pneumatic balance’’ breathing machine was described, and the Bird and Cape respirators of 1955 onward were based on this concept. Inspiratory gas flow is terminated when a preset pressure or flow is reached. Flow is generated by a mechanically driven piston, which delivers a volume of gas to the patient.

Positive pressure respirators of varying degrees of complexity became the norm in hospitals although ventilation modes became much more sophisticated. By the last decade of the century it was possible to vary the pressure throughout the respiratory cycle using different waveforms and frequencies to enable patients to interact much more with the ventilator depending on their individual needs.

Cardiopulmonary Bypass. As long ago as 1812, French physician Julien Jean- Cesar LeGallois suggested that it would be theoretically possible to replace the heart with a pump. This technique required the blood to be oxygenated (receive oxygen) while it was being pumped outside the body. By the end of the nineteenth century, primitive film and bubble oxygenators had been developed.

In 1916 Jay McLean, a medical student at Johns Hopkins University in Baltimore, discovered heparin, a blood component that prevents the clotting. This discovery solved the problem of blood clotting in extracorporeal circulation. In 1934, heart surgeon Michael DeBakey described the roller pump as a perfusion device. In 1944, Willem J. Kolff developed hemodialysis using a semipermeable membrane and extracorporeal blood circulation to remove impurities from the blood when the kidneys were unable to do so.

John H. Gibbon Jr., performed the first ‘‘open heart’’ surgery using a heart-lung machine in 1953. By 1994 it was estimated that over 650,000 open- heart operations were performed worldwide annually using cardiopulmonary bypass. These machines are not without problems, which include the amount of blood required during procedures and possible damage to the patient’s blood cells with subsequent inflammatory response syndrome. To avoid these complications, there has been a trend to perform ‘‘off-pump’’ surgery.

Aortic Balloon Counterpulsation. During severe cardiac ischemia (lack of oxygenated blood in the tissues) or after cardiac surgery, the heart muscle can fail and lack sufficient pumping action to maintain the circulation. While awaiting definitive treatment such as a transplant or the reversal of complications as in severe disorders of cardiac rhythm, aortic balloon counterpulsation can help stabilize the patient.

A balloon is positioned in the arch of the aorta, which, by precise timing of the cycle, can deflate while the left ventricle contracts (systole) forcing blood out through the arterial system, and inflate while the ventricle relaxes (diastole). This allows the maximum blood volume into circulation with each contraction and augments the coronary blood during relaxation. The device was introduced into clinical practice in 1976.

Acute Renal Failure. Modern understanding of acute renal failure (ARF) developed during the World War II years when large numbers of civilians developed renal failure following crush injuries due to collapsing buildings. As renal function failed and urinary output fell, it became apparent that too much fluid in the system was lethal. By restricting fluids to the ‘‘volume obligatoire’’ (i.e., just the replacement of fluid lost in perspiration and breathing), water intoxication could be avoided and renal function could recover. Following the development of dialysis techniques, ARF became somewhat more manageable.

Monitoring. Maintenance of the normal pH, or acid-base balance, of the blood is essential to health. As early as 1928, Laurence J. Henderson wrote ‘‘The condition known as acidosis is today hardly less familiar than anemia.’’ The recognition of the importance of metabolic balance and the steady progress in resuscitation from this time culminated in the automated intensive care and critical care units of the 1990s.

The patients admitted to an ICU frequently have metabolic reasons for acidosis, such as low blood pressure and lack of blood in the tissues secondary to shock, systemic infection, diabetic ketosis, or renal failure. In addition, these conditions are frequently complicated by respiratory problems, which exert a profound influence on maintenance of a normal pH because of the amount of carbon dioxide (CO2) normally expired.

The movements in pH initiated by these factors can often be in different directions. The biochemical basis for the understanding of acid-base balance was laid down between 1908 and 1920 when Henderson and K. A. Hasselbalch reported that measurement of the three variables, pH, pCO₂, and base deficit, was necessary to define acid-base status. Portable, easy-to-use blood gas machines that used blood from an arterial puncture gave rapid answers.

In-dwelling arterial or venous catheters enabled frequent monitoring of other electrolytes, notably sodium, potassium, and creatinine. Continuous oximetry and simultaneous pulmonary artery pressure recording by means of disposable fiber-optic catheters had become routine by 1970. Continuous monitoring of cardiac output could be achieved by placing a Doppler probe in the esophagus. All these devices provide valuable information relevant to fluid balance and cardiovascular drug support. In addition, the status of the central nervous system can be obtained by monitoring intracranial pressure and cerebral artery blood flow.

Antibiotics. Infection, and particularly septicemia in which infection has spread through the bloodstream, either as a cause of the presenting illness or as a secondary infection, has always been a problem in ICUs. It is also among the most serious problems. Since the introduction of penicillin in 1941, innumerable increasingly potent antibiotics have been developed, only to be overused and therefore made less and less effective because of acquired resistance by microorganisms.

Conclusion. Intensive care units are not cost-effective. The technology is only manageable by dedicated one- to-one nursing by highly trained staff and the availability of an equally well-trained team of medical and other specialists. By the 1980s it had become apparent that the unrelenting stress of providing intensive care could cause psychological problems in the care givers.

Research also looked at the effects on patients of sensory deprivation amid the array of technological equipment. The ability to sustain life in such an environment seemingly indefinitely had also raised questions about end-of-life care and decisions about resuscitation and life support that continued beyond the twentieth century.