| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Ann Thorac Surg 2003;76:S2210-S2215
© 2003 The Society of Thoracic Surgeons
a Emeritus Clinical Professor of Surgery, Wright State University Medical School, Dayton, Ohio, USA
* Address reprint requests to Dr DeWall, 421 Thornhill Rd, Dayton, OH 45419, USA.
Presented at the symposium, "Gibbon & His Heart-Lung Machine: 50 Years & Beyond," Philadelphia, PA, May 2, 2003.
Abstract
Open heart surgery was not possible before the early 1950s. The development of controlled cross-circulation at the University of Minnesota in 1953 was a major contributing factor toward operating safely on the interior of the heart. Cross-circulation required connecting a donor's arterial and venous blood vessels to those of a smaller recipient whose heart could then be opened for corrective surgery. At that time no mechanical system was available to serve the role of the donor. The need to replace the donor was recognized. The author describes his experience with the development of the helical reservoir bubble oxygenator, which replaced the donor in cross-circulation supported open heart surgery. Other sidelights of the author's experience during the early days of open heart surgery at the University of Minnesota Department of Surgery are also recounted.
Open heart surgery for human patients was envisioned by John H. Gibbon, Jr, in the early 1930s, achieving success in animals in 1937 using a heart-lung machine of his design [1]. The key to Dr Gibbon's success was the first availability of heparin, necessary for all heart-lung machines that subsequently appeared. World War II interrupted his work, which he resumed after the war. Doctor Gibbon redesigned his apparatus and used it for the world's first open heart clinical success in 1953 [2].
Background
As the author acknowledges the existence of many pump-oxygenator systems, it is not the intent here to review them all but only to recount his experience at the University of Minnesota Department of Surgery during the dawn of open heart surgery. Research on perfusion systems to study biological organs appeared in the literature from 1812 onward [3–5]. Such research demanded an increasing amount of attention in many of the world's laboratories after World War II.
The primary event that led to successful cardiopulmonary bypass for open heart surgery occurred in 1916 at the Johns Hopkins University. There Jay McLean, a medical student working in the laboratory of Dr William Howell, isolated an anticoagulant from a liver extract [6]. Doctor Howell called this substance heparin, the name derived from its hepatic tissue origin [7].
Doctor Charles Best, who was a codiscoverer of insulin and lived in Toronto, became aware of the development of heparin from Dr Howell. Doctor Best, along with his colleagues Drs Charles and Scott, proceeded to purify heparin and reported their research in 1927 [8].
Doctor John H. Gibbon, Jr, first considered the idea of a heart lung machine in 1931 and began research on a pump-oxygenator system in 1934 [1, 9]. Heparin for Dr Gibbon's research was supplied by Dr Best. Doctor Gibbon's first pump-oxygenator was a vertically oriented rotating cylinder in which blood filmed down its interior surface [1]. The Gibbon system was successfully used in 1937 to perfuse cats.
After World War II Dr Gibbon continued work with extracorporeal circulation using a newly designed parallel screen oxygenator. Doctor Gibbon achieved clinical success with his system in May of 1953 [2]. After WWII medica1 centers around the world experimented with their own versions of a pump-oxygenator system.
The University of Minnesota
Many children with congenital intracardiac defects were treated by the pediatric cardiologists at the University of Minnesota in the late 1940s and early 1950s. As these intracardiac defects could not be cured by the then available methods, the solution for a cure had to be a surgical one. Doctor Clarence Dennis of the University of Minnesota surgical staff accepted the challenge. A pump-oxygenator would be required. Doctor Dennis and his team devised a rotating screen oxygenator and experienced good success in animals. The first clinical trial with the Dennis system occurred in 1951 [10]. This effort failed. Subsequently Dr Dennis moved to New York to an academic position. The inspiration of Dr Dennis's work influenced others in the University of Minnesota surgery department.
All members of the University of Minnesota surgery department, faculty and residents, under the direction of the department chief Dr Owen Wangensteen were expected to conduct independent surgical research. Doctor C. Walton Lillehei chose to study cardiovascular problems. In 1952 Dr Morley Cohen, a surgical resident, began his surgical research in Dr Lillehei's laboratory. Their goal was to pursue development of techniques for open heart surgery.
A 1952 report by Drs Andreasen and Watson [11] found that a dog could survive for one-half hour without clinical harm with only the blood flow to its heart from its azygos vein. Their observation was called the azygos factor. Doctors Lillehei and Cohen realized that this information could be applied to their research. The azygos blood flow represented about 10% of a normal resting cardiac output.
Doctor Cohen's research used a portion of the dog's own lung as an oxygenator. For a pump he chose a common laboratory pump that could be calibrated to deliver a balanced blood flow between the arterial and venous circulation of his laboratory model. He cannulated a pulmonary vein through the left atrial appendage to remove an amount of arterial blood equal to 10% of a dog's resting cardiac output. The blood was pumped into the systemic arterial system of the animal. Venous blood in a like amount was removed from the dog's vena cava and pumped into its pulmonary artery. Both cavae were occluded at their junction with the heart. This method established complete circulatory bypass of the dog's heart to permit open heart surgery [12].
Doctor Cohen's wife was pregnant when the autologous lung oxygenator studies neared completion. The maternal fetal placental connection suggested to Dr Cohen that this relationship represented an ideal blood donor recipient patient support system (personal communication with Dr Cohen). Doctor Cohen discussed with Dr Herbert Warden the possibility of joining the arterial and venous systems of two dogs through plastic conduits. The blood inflow and the outflow would be controlled with a calibrated pump. The recipient animal received 10% of that animal's normal resting cardiac output from the donor animal. This two-dog relationship became known as controlled cross-circulation [13].
Doctor Warden became Dr Cohen's successor as director of Dr Lillehei's laboratory when Dr Cohen advanced to another level of his residency in mid 1953. Doctors Cohen and Warden discussed the proposed controlled cross-circulation with Dr Lillehei who approved of the experiments. Doctor Warden developed the laboratory studies on controlled cross-circulation as his major research project. When time permitted Dr Cohen helped Dr Warden on these experiments until I began working for Dr Warden.
After extensive investigations into the physiologic parameters observed with the laboratory cross-circulation studies including sham open heart surgical procedures the material was presented to a faculty committee. The committee agreed that controlled cross-circulation was ready for clinical application.
Doctor Lillehei performed the first open heart surgery that used the support of controlled cross-circulation on March 24, 1954. The patient, who survived, was a 13-month-old child with a ventricular septal defect. A total of 45 patients with congenital heart disease were operated upon with the aid of controlled cross-circulation [14]. Blood flow supplied to these patients was calculated to be 30% to 40% of the patient's resting output.
Development of the helical reservoir pump-oxygenator
The following account relates to my participation in the open heart surgery program at the University of Minnesota. While I was serving a military internship from mid 1952 to mid 1953 one of my patients was a young seaman with severe rheumatic valvular heart disease. No cure existed at that time for such a problem. That caused me to think of the heart as a pump with internal valves. Pumps with internal valves had existed for hundreds of years. Why could not the heart be opened and the valves repaired as with any other pump?
I returned to my home in Minneapolis in 1953 after completing my internship to work in a general practice. I recalled the plight of my patient with rheumatic valvular heart disease. Solutions for the repair of such diseased valves had not been devised. Not knowing how to approach a malfunctioning heart valve problem, I carved a prototype flutter valve out of plaster of Paris. I did not know what to do with this valve until I thought of talking to one of my medical school teachers, Dr Richard Varco, the chief of heart surgery at the University of Minnesota.
I went to the University and was directed by Dr Varco's secretary to the operating room suite. There Dr Varco had just finished a case. He kindly received me and we sat on a litter outside of his operating room. I showed him my plaster valve while we discussed valve surgery. Doctor Varco said he would help me work on my proposed problem and he arranged for me to meet with Dr C. Walton Lillehei who had an animal laboratory with emphasis directed toward heart surgery.
In February of 1954 I met with Dr Lillehei who brought me to his animal laboratory. There I was introduced to Dr Herbert Warden. After some discussion they offered me the opportunity to join them in the laboratory to work on heart problems. Doctor Warden, who was a surgery resident in his laboratory rotation, directed the laboratory and was well along with his studies on controlled cross-circulation. Doctor Lillehei mentioned to me that since all of the residency appointments for the year had been filled there was no money for another surgical resident. He said that the surgical research fund had money to pay me as an animal attendant. Since I was interested in laboratory medicine and had not considered myself a surgery resident candidate to be employed as an animal attendant was perfectly acceptable. An animal attendant had an advantage over a surgical resident. The pay was much better.
On March 1, 1954, I began work under the direction of Dr Warden in Dr Lillehei's laboratory. Perfusion physiology of controlled cross-circu1ation was the emphasis of the laboratory work. Doctor Warden was an excellent teacher. My duties were to manage the perfusion pump and to help set up and conduct the experiments. After 8 months of cross-circulation studies by Dr Warden and to a limited extent by myself the procedure was transferred to the operating room for support of pediatric open heart clinical cases.
Doctor Lillehei's clinical program using controlled cross-circulation was the only open heart surgical program in the world. The program attracted many surgeons from the world's surgical clinics. The use of controlled cross-circulation had several advantages. The procedure worked, it was simple to set up, all of the blood contacting surfaces were steam sterilized and disposable, the procedure required a minimal blood prime and a minimal use of donated blood, and it was cost effective. As the world was still recovering from the aftermath of WWII, funding for health care was scarce.
The helical reservoir pump-oxygenator
One day after completing an open heart repair Dr Lillehei mentioned to me that it would be desirable to find a substitute for the donor in the cross-circulation procedures. A reliable heart-lung machine was needed. Doctor Lillehei suggested research on a heart-lung machine as a good project for me. He also mentioned that if the project appealed to me I should avoid library research on the subject in order to keep an open mind. Doctor Lillehei's other admonition to me was to avoid bubble oxygenator systems as they had a poor history for clinical success.
I began my research project on July 1, 1954, while continuing as perfusionist for the open heart cross-circulation procedures. Afternoons and evenings were reserved for my laboratory research. At the time I began my research two methods were apparent for the exposure of blood to an oxygen phase in an extracorporeal system. One system created a thin film of blood over a flat surface in an oxygen atmosphere. The other option created bubbles by channeling fine streams of oxygen into the blood. The use of membranes had not surfaced as feasible at this time.
Several variables influenced the oxygenation of blood in an extracorporeal system. These variables included (1) the thickness of the blood film either as a film over a flat surface or a film surrounding a gas phase—a bubble; the thickness of the blood film affects the time necessary for the oxygen to diffuse through the blood plasma to the red blood cells; the oxygen and hemoglobin reaction is almost instantaneous [15]; (2) the time of exposure of blood to the gas phase; (3) the pO2; (4) the pCO2; (5) the pH; (6) the temperature; and (7) the bubble size if a bubble system is to be considered—smaller bubbles retain carbon dioxide to a greater degree than larger bubbles.
Recalling Dr Lillehei's recommendation to avoid bubbles I explored a number of methods using filming techniques. All these efforts failed. As hyperbaric systems for the oxygenation of blood had not been tried I calculated that blood exposed to three atmospheres of oxygen would put six volumes percent of oxygen into the blood plasma. This is equivalent to a normal arteriovenous oxygen difference.
Doctor Lillehei suggested that I might find use for a polyvinyl chloride (PVC) hose such as used in the food industry. The use of a plastic material was fortuitous, as a PVC surface was much more compatible with blood than glass. It had been demonstrated that an uncoated glass surface was deleterious to blood clotting factors especially thromboplastin [16], therefore the avoidance of a glass container for an oxygenator was desirable.
My next objective was to produce a hyperbaric oxygenator. A thick film of blood was more manageable than a thin film. The hyperbaricity would easily overcome the thickness of the blood film. It was apparent that blood could be filmed by flowing down a long inclined tube. The thickness of the blood film could be controlled by the rate of input, the output, and the incline of the tube.
A 6-foot long, 1-inch internal diameter PVC tube was placed at a 45-degree angle and held on a supporting frame. An oxygen input device was placed between the middle and the lower third of the tube. Pressurized oxygen flushed the space above the blood flowing down the tube. A rubber cork at the bottom of the tube contained a port for the outflow of the oxygenated blood.
The top of the tube was capped with a rubber cork that contained a venous blood input port and an exhaust port for the removal of respiratory gases. The exhaust port contained a pressure gauge, which controlled the gas pressure within the oxygenator at three atmospheres. The blood-filled lower third of the tube served as a reservoir. An occluding pump maintained the blood flow in and out of the tube. Because the 6-foot long tube was cumbersome it was wrapped around a stand to make a helical oxygenator and reservoir.
I made an error in judgment with the hyperbaric system because I had not considered the effects of decompression. The blood must be decompressed to one atmosphere of pressure before it can be returned to the animal. Although the hyperbaric experiments did not provide a prototype for a practical pump-oxygenator, several observations proved useful. Upon decompression oxygen came out of solution and formed bubbles in the blood. As the decompressed blood flowed through and into the reservoir at the bottom third of the coiled tube, the lighter bubble containing blood would skim off the top layer leaving bubble-free blood that filled the lower third of the tube, the reservoir. The bubble-free blood in the reservoir proved to be safe when infused into the experimental animal.
Bubbles present a problem in any oxygenator system. To learn to manage bubbles seemed appropriate. My next efforts were to develop a bubble oxygenator system incorporating the useful observations from the hyperbaric system. This involved using a 2-foot long segment of hose placed in a vertical position. A rubber cork perforated by 18 no. 22 hypodermic needles was inserted into the base of the vertical tube, which would disperse oxygen into venous blood producing bubbles in contrast to foam. Foam was more difficult to remove from blood than larger bubbles. A second 3-inch long matching hose segment was closed at its lower end with a cork. The short hose segment was attached to the bottom of the vertical tube to direct oxygen flow through the hypodermic needles. A quarter-inch internal diameter conduit was placed through the lower chamber and into the vertical tube to emerge between the hypodermic needles. With the flow of oxygen venous blood bubbles formed at the base of the vertical tube, absorbed oxygen, and released carbon dioxide as it flowed to the top of the tube. An additional conduit served to connect the oxygenating or bubbling tube into the top of the helical reservoir, which now had filled two thirds or more of its length with the oxygenated blood.
Blood bubble contact with the plastic surfaces such as PVC had some debubbling effect. The helical reservoir served to eliminate any residual bubbles. Blood leaving the helical reservoir passed through a filter such as was used in donor transfusion bottles. Figure 1 illustrates a diagrammatic representation of the helical reservoir oxygenator.
|
The first configuration of the helical reservoir oxygenator was suitable only for patients less than 20 pounds. By serially increasing the systems dimensions patients of any size could be accommodated. Each increase in the system's size was tested in animal perfusions before being used clinically. This testing assured success at higher perfusion rates [18].
The first clinical use of the helical reservoir pump-oxygenator occurred on May 13, 1955. The patient was a 3-year-old boy with a ventricular septal defect. The procedure went well. The reservoir pump-oxygenator system quickly achieved worldwide acceptance. Several factors led to its popularity. These factors included the fact that it was cost effective, it could be assembled from inexpensive materials available in all parts of the world, and it could be steam sterilized and discarded after one use. There were no complicated surfaces to clean. Figure 2 shows the helical reservoir system before its use in the operating room.
|
As surgeons learned the pathophysiology of congenital heart disease and especially how to take care of the postperfusion patient a need developed for a system that did not have to be hand-made before each operation. The Travenol Division of Baxter Laboratories aided in the development of a presterilized disposable oxygenator and became its manufacturer [20]. Two sheets of PVC were fused together forming channels incorporating the helical reservoir concept and this was called the sheet oxygenator. Doctor Vincent Gott developed the sheet oxygenator program, illustrated in Figure 3.
|
|
|
|
Open heart surgery was not possible before the early 1950s. The development of controlled cross-circulation at the University of Minnesota in 1953 was a major contributing factor toward operating safely on the interior of the heart. Cross-circulation required connecting a donor's arterial and venous blood vessels to those of a smaller recipient whose heart could then be opened for corrective surgery. At that time no mechanical system was available to serve the role of the donor. The need to replace the donor was recognized. Here I have recounted my experience with the development of the helical reservoir bubble oxygenator, which replaced the donor in cross-circulation supported open heart surgery along with other sidelights of my experience during the early days of open heart surgery at the University of Minnesota Department of Surgery.
References
This article has been cited by other articles:
|
|
 |
|
  R. DeWall Cardiovascular Inventiveness Within the University of Minnesota Department of Surgery Ann. Thorac. Surg., June 1, 2005; 79(6): S2214 - S2216. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
