Kevin Loughlin
Boston, Massachusetts, United States

When one reflects on the landmark advances of medicine in the 20th century, there is no shortage of achievements. The introduction of antibiotics, the use of numerous vaccines, organ transplantation, the multimodality treatment of cancers, the understanding of the genetic basis of many diseases, the prevention and treatment of cardiac disease are just a partial list of achievements.

However, not to mention the advent of intensive care units in most medium sized and large hospitals would be an important oversight. Like so many medical milestones, the birth of the intensive care unit was not the work of a single individual or institution. The intensive care unit was, in large measure, a response to the perceived need of better care and outcomes for a variety of illnesses.

Dwight Harken was born in Osceola, Iowa in 1910. His father was a physician and Harken graduated from Harvard College and Harvard Medical School. (Figure 1) He received thoracic surgery training at Bellevue Hospital and in London and when World War II started, he joined the United States Army Medical Corps.

A defining moment in Harken’s life occurred during the D-day invasion on June 6, 1944.¹ He was faced with a badly wounded soldier during the landings and an X-ray showed a metallic foreign body lodged in his heart. He quickly opened the chest and discovered that the foreign body was in the right ventricle. In a letter to his wife, he described his successful removal of the fragment despite one of the sutures going through one of the fingers of his surgical gloves.¹ Over the next 10 months, he would remove bits of shrapnel from 134 soldiers without a fatality. These included 78 foreign bodies from the great vessels and 56 from the heart itself.

After the war, he continued his career as a thoracic surgeon and in 1948, Francis D. Moore, the new surgeon-in-chief at Peter Bent Brigham Hospital, recruited him to be chief of thoracic and cardiac surgery. With the underpinning of his wartime experience, Harken turned his attention to mitral valve disease. He developed a technique where an incision would be made in the atrium providing direct access to the mitral valve. Using his finger, he manually widened the valve opening to improve blood flow and then he would close the incision of the atrium.² However, the early results were dismal; the first six patients died. When the seventh patient survived, he published the results in the New England Journal of Medicine.³

In the next few years, Harken expanded his experience with both mitral valve and aortic valve disease. To put his experience in the proper context, it should be acknowledged that both anesthesiology and blood banking were in their nascent stages. It was not until April 5,1951 that Clarence Dennis at the University of Minnesota introduced cardiopulmonary bypass during an operation to close an atrial septal defect.⁴

Harken continued to push the surgical envelope of early cardiac surgery, but he never lost his appreciation for patient care. This concern resulted in two landmark achievements beyond the operating theater. In January 1951, Harken gathered four patients who had undergone cardiac surgery at Peter Bent Brigham Hospital. They shared their experience with heart surgery and Harken immediately recognized the value of patient support groups. This led him to start the Mended Hearts Group which was a model for many other patient support groups which would soon follow.

Perhaps even more important than the Mended Hearts, was Harken’s recognition of the need for dedicated intensive care units. Harken was well aware of the intraoperative and postoperative morbidity of cardiac surgery in the 1940s and 1950s. This motivated him to organize the first intensive care unit in North America in 1951 at the Brigham. It coincided with the increased availability and sophistication of monitoring devices. His vision for an intensive care unit was captured in his words, “ We can impact patient care, not just 24 hours later, we can do it hour to hour and minute to minute. And if we do that, the patients will do better,”.⁵

At the same time that Dwight Harken and his associates were confronting the challenges of early cardiac surgery in Boston, Danish physicians were dealing with a polio epidemic in Copenhagen. In 1952, when the epidemic occurred, hundreds of victims experienced respiratory failure. This resulted in over 300 patients requiring artificial ventilation for several weeks. Over 1000 medical and dental students were recruited to hand ventilate these patients via tracheostomies.⁶ Soon after, Bjorn Ibsen, the anesthesiologist who had advocated that positive pressure ventilation should be the treatment of choice during the epidemic, established the first intensive care unit (ICU) in Europe. Many consider him the “father” of intensive care. (Figure2)

In the decades that followed, the establishment of ICUs expanded throughout the world. Concurrent with this expansion was the development of a myriad of monitoring devices that started with pH, pCO2 and O2 electrodes and continued with increasingly complex technology. The technological advances provided a synergy that enabled more intensive monitoring of sick patients.

The ongoing acceptance of ICUs is a necessary component of modern, sophisticated medical care and gave rise to the new subspeciality of “intensivists.” These were physicians who were specifically trained in aspects of critical care medicine, often with fellowship certification, to care for critically ill patients with a myriad of pathological conditions.

The specialization that began with “intensivists” continued with dedicated ICU nurses. Further expansion continued with the establishment of neonatal ICUs in many large hospitals in order to provide care for critically ill newborns. The most recent tangible benefit of ICUs appeared during the Covid pandemic.⁷ Without the access to intensive care units throughout the world, the devastation caused by Covid would have been significantly worse.

Medical progress is a complex phenomenon. It is usually the confluence of individuals recognizing a health care challenge and responding to it. It is often not the response of a single individual, but a team of physicians identifying a health care threat and seeking a solution. So it was with the birth of the ICU in the mid twentieth century. Dwight Harken in Boston and Bjorn Ibsen in Copenhagen faced dissimilar challenges-heart surgery and polio, but the necessity of confronting these challenges resulted in the establishment of intensive care units which has changed the practice of medicine. It can be persuasively argued that the establishment of intensive care units was one of the major advances of 20th century medical care.

References

1. Tilney NL. A Perfectly Striking Departure: Surgeons and Surgery at the Peter Bent Brigham Hospital. Science History Publications/USA, Sagamore Beach 2006, pp 203-204
2. Dr. Dwight E. Harken. icardio.ca/en/episode-3-dr-dwight-e-harken January 18, 2025 accessed 8/2/2026
3. Harken DE, Ellis LB, Ware PF, Norman LR. The surgical treatment of mitral stenosis. I-Valvuloplasties. NEJM 1948; 239 (22): 801-809
4. Jepson BM, Mackay-Bajack S, Moller JH. The First Cardiac Operation Using Cardiopulmonary Bypass. Am. Thorac. Surg. 2017; 103: 339-340
5. The Mended Hearts. https://TheMendedHearts.Harnessgiving.org/donate. Accessed 7/31/2026
6. Kelly FE, Fong K, Hirsch N, Nolan JP. Intensive care medicine is 60 years old: The history and future of the intensive care unit. Clin. Med. (Lond) 2014; 14 (4): 376-379
7. Basem J, Roth AF, White RS et al. Patient care in rapid-expansion intensive care units during COVID-19 pandemic crisis. BMC Anesthesiol. 2022; 22: 209-220