A patient being prepared for cryoprotectant perfusion
at Alcor's facility in Scottsdale, Arizona.
For a more detailed and technical pressentation of this subject, see Alcor Human Cryopreservation Protocol (PDF).
The purpose of cryonics is to preserve life. Alcor therefore intervenes in the dying process at the earliest moment that is legally possible. If proper procedures are followed immediately after the heart stops, then legal death need not impact the biology of cryonics or its prospects for success. For further information concerning this issue see Cardiopulmonary Support in Cryonics.
It is customary practice in medicine to discontinue care of terminal patients, and declare legal death, when the heart stops beating. The several minutes of time between when the heart stops and the brain dies (by conventional criteria) provides a window of opportunity for Alcor to artificially restore blood circulation and preserve brain viability even though a patient is legally deceased. Cryonics cases in which life support techniques are promptly used to maintain brain viability after the heart stops are considered to be ideal cases.
Alcor strongly encourages members who are terminally ill to relocate to cooperative hospice facilities in Scottsdale, Arizona. If relocation is not possible, Alcor may deploy equipment and a transport team to a remote location. As a dying patient's condition becomes critical, Alcor personnel wait nearby on a 24-hour basis. This is called "standby." When the heart stops beating, an independent nurse or physician pronounces legal death, and the Alcor team begins life support procedures as described below.
The patient is placed in an ice water bath, and blood circulation and breathing are artificially restored by a heart-lung resuscitator (HLR). The HLR, or "thumper," is a mechanical device used in emergency medicine to perform CPR. In cryonics, the term CPS (cardiopulmonary support) is used instead of CPR because the intent is to provide life support, not cardiac resuscitation. Because cryonics patients are legally deceased, Alcor can use methods that are not yet approved for conventional medical use. This enables Alcor to use new technologies that can support the brain longer and more effectively than traditional CPR. In particular, the combination of simultaneous compression-decompression CPS and rapid cooling are known to be especially effective for protecting the brain during cardiac arrest.
Intravenous lines are also established, and protective medications are administered. These include:
These drugs help maintain blood pressure during CPS, and protect the brain from "reperfusion" injury. Anesthesia reduces brain oxygen consumption, which further protects the brain.
If the patient is in a hospital where the administration is unwilling to allow cryonics procedures, the patient is moved to an alternate location while CPS and cooling are maintained without interruption. Femoral arteries and veins are surgically accessed and the patient is placed on cardiopulmonary bypass. This means that blood is circulated through a portable heart-lung machine (pictured below) that takes over the function of the patient's own heart and lungs. External CPS is no longer necessary, and is discontinued.
Within minutes, a heat exchanger in the heart-lung machine reduces the patient's temperature to a few degrees above the freezing point of water. Blood is also replaced with an organ preservation solution that is specially designed to support life at low temperature. If the patient is located outside of Arizona, they are packed in ice for air shipment to Alcor's facility in Scottsdale, Arizona.
This treatment is similar to procedures used by transplant surgeons
to support the life of organs moved around the country for transplant, except
that Alcor's procedures are applied to whole patients. Remarkably, studies show
that whole animals can
survive up to three hours of cold storage on ice using existing medical
longer periods can be survived if the preservation solution is continuously
circulated. The MHP2 preservation solution used by Alcor was developed in 1984
during pioneering experiments in which animals
were successfully recovered after 4 hours of bloodless perfusion at +4°C.
After large blood vessels are surgically accessed, Alcor's Air Transportable Perfusion kit (ATP), shown in the photo below, is able to quickly cool the patient to temperatures at which oxygen is no longer necessary. The ATP also replaces blood with an organ preservation solution that supports life at low temperature (note the solution reservoir in the case on the left). See our online PDF manual (1.4 megs).
At Alcor major blood vessels are connected to a perfusion circuit by a physician or veterinary surgeon. The preferred vascular access points are the aortic arch and right auricle of the heart, which are accessed by thoracic surgery (median sternotomy). Traditionally, neuropreservation patients have been treated by this same procedure, except that the descending aorta was clamped. In 2000, Alcor began treating neuropreservation patients by directly accessing the carotid and vertebral arteries. This requires careful surgical transection of the spinal column because vertebral arteries are located within the column.
A base perfusate similar to the preservation solution used during transport is circulated through the patient at a temperature near 0°C (the freezing point of water) for several minutes. This washes out any remaining blood. The cryoprotectant concentration is then linearly increased over 2 hours to one half the final target concentration. This slow introduction minimizes osmotic stress, and allows time for the cryoprotectant concentration to equilibrate (become the same) inside and outside cells. A rapid increase to the final concentration is then made, and the final concentration is held until the venous outflow concentration equals the target concentration (approximately one hour). Temperature, pressure, and cryoprotectant concentration data are continuously monitored and acquired by computer.
The status of the brain is visually monitored through two small holes in the skull made using a standard neurosurgical tool (14 mm Codman perforator). This permits verification of brain perfusion by dye injection, and observation of the osmotic response of the brain. A healthy brain slightly retracts from the skull in response to cryoprotectant perfusion. An injured brain swells, indicating that the blood-brain barrier has been compromised. This injury is often seen in patients who suffered a long period of untreated cardiac arrest.
The cryoprotectant solution Alcor uses to prevent freezing is a mixture of chemicals developed by mainstream cryobiologists for long-term banking of transplantable organs. The solution has been specifically validated for structural preservation of the brain. At the end of perfusion, these chemicals are present at a concentration of approximately 60%. In tissues adequately penetrated by the solution, the small amount of remaining water is not able to freeze. Instead of freezing, tissues vitrify when they are cooled to cryogenic temperatures. Variable penetration of the solution appears to result in a combination of vitrification and partial freezing in various body tissues, but total vitrification (ice-free preservation) of the brain, at least under ideal conditions.
After cryoprotective perfusion, patients are cooled under computer control by fans circulating nitrogen gas at a temperature near -125°C. The goal is to cool all parts of the patient below -124°C (the glass transition temperature) as quickly as possible to avoid any ice formation. This requires approximately three hours, at the end of which the patient will have "vitrified" (reached a stable ice-free state). The patient is then further cooled to -196°C over approximately two weeks.
Patients are monitored by sensitive "crackphone" instruments during this long cooling period to detect fracturing events that tend to occur when large objects are cooled below the glass transition temperature. Contrary to media reports, fracturing is not a result of mishandling. It is a universal problem for large organs cooled to liquid nitrogen temperature. The federal government recently awarded $1.3 million dollars to specifically study the problem of fracturing during cryopreservation.
Currently Alcor patients are stored under liquid nitrogen at a temperature of -196°C. The liquid nitrogen is held in vacuum-insulated dewars that require replenishment every few weeks. Liquid nitrogen is used because it is inexpensive and reliable.
Alcor is currently experimenting with an alternative "vapor phase" storage system that would retain the safety and reliability advantages of liquid nitrogen, but allow patients to be maintained at controlled temperatures warmer than liquid nitrogen. This will reduce or eliminate fracturing injury.
Unfortunately not all Alcor members can be reached at the moment their heart stops. In cases of sudden illness or serious injury, blood circulation may stop for hours before any cryonics procedures are possible. If a physician determines that an Alcor member in cardiac arrest cannot be resuscitated by current technology (i.e. declares legal death), the most important actions are administration of heparin (a drug that prevents blood clotting) followed by chest compressions to circulate the heparin, cooling with ice, and prompt shipment on ice to Alcor. Alcor will cooperate with local funeral directors in making these arrangements. Alcor will also negotiate with authorities to limit the extent of any autopsy that may be required. (Alcor recommends that all members execute a Religious Objection to Autopsy).
The application of cryonics to patients who are clinically dead is perhaps the single most misunderstood aspect of cryonics. How can cryonics help someone who is clinically dead? The answer is that life and death are not binary "on-off" states. For cells, organs, and people, death is a process, not an event.
For example, the brain is commonly believed to "die" after 5 minutes without oxygen at normal body temperature. This is a myth. Brains have been revived after one hour of warm cardiac arrest, and living human brain cells have been recovered after 4 hours and even 8 hours of clinical death at normal temperature. What really happens is that after 5 minutes without oxygen, chemical changes occur in the brain that cause blood vessels to swell when circulation is restored. Without special interventions, this swelling eventually stops the restored blood flow, resulting in the death of all brain cells hours later. The practical result is that a brain that is deprived of oxygen for more than 5 minutes is usually doomed to die within hours. But doomed is not the same as dead.
The biological changes known to occur in the first hours following cardiac arrest are fundamentally minor and reversible in principle. Technology already exists that could recover people after more than 5 minutes of cardiac arrest, although it is seldom used. The conventional medical research value of donated brain tissue and living brain cells recovered from post-mortem donors further highlights the minor nature of brain changes in the early hours of clinical death.
Ultimately the difference between life and death for a cell, an organ, or an organism reduces to a difference in how atoms are arranged inside it. It therefore seems certain that future medicine capable of diagnosis and repair at a molecular level will be able to resuscitate people after longer periods of clinical death than medicine can today. How much memory and personality would survive repair and healing after hours of cardiac arrest is not currently known.
Cryopreservation of clinically dead patients is double speculation. First, as with all cryonics cases, it is assumed that the cryopreservation process will someday be reversible. Second, it is assumed that future medicine will be able to successfully recover people after long periods of cardiac arrest. Alcor therefore encourages members to reduce their risk profile for heart attack and stroke, and relocate close to Alcor during serious illness if possible. If despite these precautions a member experiences unattended cardiac arrest, Alcor will still proceed with cryopreservation unless a member indicates otherwise in their paperwork.
Cryonics should never be confused with funeral arrangements. Alcor rarely accepts cases involving legal death of a non-member. The combination of strong emotion, false hope, unfamiliarity with cryonics, low probability of success, and high cost of cryonics without life insurance make accepting such cases ethically difficult. People who think they may someday be interested in cryonics should therefore investigate cryonics now. Waiting until cryonics is needed almost always means it won't be available.
For Alcor members who have chosen to be cryopreserved under poor conditions if necessary, there is a final ethical point. As long as resuscitation medicine remains an unfinished science, it is unethical to use the label "dead" as a basis to dismiss cryonics. Calling someone "dead" is merely medicine's way of excusing itself from resuscitation problems it cannot fix today. This makes people feel better about abandoning the patient and making the unwarranted assumption that nobody could ever fix the problem. Cryonics, in contrast, is conservative care that acknowledges that the real line between life and death is unclear and not currently known. It is humility in the face of the unknown. It is the right thing to do.