Vitrification perfusion circuits should be monitored for the following parameters:
2. Air emboli
3. Reservoir level
5. Concentration of the vitrification solution.
Computerized perfusion systems, have been around for decades, in the form of heart-lung machines. Though these may not turn out to be the ideal systems to build on, for vitrification perfusion, I think they are at least worth looking at. In speaking with people involved in cryonics, I’m not sure many people realize exactly what a heart-lung machine is, or does.
Typically, a heart-lung machine consists of 3-5 pumps that are monitored, and servo-controlled, by a computer. The computer is usually about the same size and shape as one of the pumps. The pumps, along with the computer are positioned on a rolling base that also accommodates a monitor, as well as holders for various perfusion components, (reservoirs, oxygenators, filters, etc.).
Cables are connected between the computer and the pumps. Desired parameters are entered into the computer. For instance, the computer can be set to alarm if pressure in a circuit exceeds 150mmHg, (or any other set value) and/or to turn off one of the pumps and clamp the associated lines, if the pressure in that pump’s circuit exceeds a higher value, (such as 200mmHg). Defaults for values such as these are simple to program, and easy to adjust, or override, during a case, if necessary.
The computer is not restricted to monitoring the perfusion circuit; you can monitor a variety of inputs such as patient temperatures and pressures.
There are pumps designed to deliver increasing/decreasing concentrations of certain solutions, such as the cardioplegia solutions used to stop the heart, during open-heart surgery. This may be of use, in the ramping of the vitrification solution concentration.
Someone who is familiar with Alcor has taken a lot of time to graciously explain to me why that company has approached their circuit the way they have. At this point, I feel they are doing what is best for their institution, given the history, their goals, their budget, and a few other factors. However, I think even they would agree that, if they were starting at “Square One,” and they could afford to write a check for a new heart-lung machine, they might take a different route.
I feel starting with a heart-lung machine that will measure, display and respond to four of the five desired parameters is a lot more practical than started from scratch. I have not priced heart-lung machines, recently, but I would estimate the cost of a new one with quite a few whistles and bells, to be in the neighborhood of 100,000K. That’s probably not as much as it would cost to have someone buy all the components and program a comparable system. Also, it is often possible to get used, or refurbished, models for much less. I think this course of action is at least worth exploring for companies that are just beginning to work toward the goal of vitrification.
***Please note: This article contains ideas and suggestions based on my education and my decade of experience as a clinical perfusionist in heart surgery. I have not participated in any cryonics procedures, and I have a lot to learn about the vitrification process. I am open to any, and all, constructive comments and criticisms.