The Debate Over Graft Storage Methods
For years, hair transplant (HT) surgeons have debated the best medium for short-term storage of hair-bearing grafts during the period prior to placement in the recipient area, and the temperature at which the medium should be maintained.
Normal saline (NS), lactated Ringer’s solution, and others have been utilized, at room temperature and at varying degrees of coldness.
The importance of this may be reflected in graft survival and yield, in post-operative effluvium, and in graft retention. However, it remains unclear as to the most advantageous protocol for ex vivo storage of hair-bearing grafts.
How Tissues Behave Outside the Body
It is well known that tissues continue to consume energy in metabolic processes, as well as to create waste products when excised from living organisms and placed in aqueous solutions.
This, of course, may quickly deplete energy stores and create increasing levels of free radicals, along with a decrease in pH as an acidic environment develops.
Prior studies have shown that cells become metabolically quite inactive at temperatures of 4 degrees Celsius or lower.
It has also been shown that buffered saline solution (BSS) maintains a constant pH over time (with or without tissue, up to 5 hours), as opposed to plain normal saline, which reveals a drop in pH quickly and continues to decline as a function of time independent of temperature or the presence of graft tissue.
Problems with Room Temperature Saline
There are a number of reasons to consider avoiding the use of saline as a storage solution for hair-bearing grafts in hair transplant surgery.
One is the drop in pH that occurs over time with room temperature saline. This may have a deleterious effect on graft survival and eventual yield; the lack of metabolic slow-down observed with room temperature solutions is another consideration.
Although cold storage solutions markedly decrease the metabolic activity of tissues, the cold saline solution causes paralysis of sodium-potassium active transport channels; the end result of this phenomenon is a net influx of water and resultant cellular edema, or swelling.
If unchecked, this may lead to lysis or bursting of the cell.
The Cellular Swelling Problem
To elaborate on the above, let us consider the membrane pump, which maintains the intracellular concentration of potassium many times above that in the extracellular space (outside the cell).
It also maintains the concentration of sodium many times lower than that outside. All other ions are sequestered in a similar manner in order to maintain electrical and osmotic balance.
When the ion pump mechanism is perturbed by, for example, decreased temperature, the electrical and osmotic gradients are disrupted.
As a result, water enters the cell, attracted by solutes and colloidal materials; then, electrically charged ions follow in an attempt to normalize the trans-membrane potential.
The resultant hypertonic state leads to even more water passively crossing into the cell, and cellular edema exists.
Specialized Cold Storage Solutions
These phenomena discussed above have led to the development of various hypothermic cell preservation solutions.
These are designed to be used exclusively in a cold environment.
Studies comparing human hair follicles stored in saline and in a cold tissue solution (Hypothermosol or HTS) showed a significant improvement in viability of the Hypothermosol tissues, both in terms of metabolic activity during recovery, and in terms of cell membrane integrity.
Specialized cold tissue storage media such as HTS are designed to achieve several goals in which saline-type solutions cannot; that is, to minimize swelling, maintain ionic balance across cell membranes, prevent acidosis, prevent free radical formation, or quench free radicals, and to provide high-energy substrates upon reperfusion.
It is well established that the reperfusion period, during which ischemic tissues have blood flow restored, is most critical for the viability and survival of grafted tissues.
Our Graft Chilling System
We have developed a technique that utilizes circulating coolant to maintain our hair-bearing grafts in cold HTS during a time out of the body.
Preliminary observation suggests that yields post-hair transplants may be superior using this technique.
The set-up is relatively simple. A pump circulates cold water via inflow and outflow conduits.
These conduits communicate by way of a “capillary bed” arrangement of sorts; it is above this “bed” that the graft containers are placed.
Pre-chilled Hypothermosol is placed in the containers (eg, Petri dishes) and monitored to the desired temperature, which in our facility is 2 to 4 degrees Celsius.
The temperature is monitored continuously with a laser thermometer directed into the solution.
The Optimal Temperature Range
We have learned that the optimal temperature for maintaining tissues is about 2 to 4 degrees Celsius.
This is easily maintained with our apparatus (as our continual monitoring reveals), and the inclusion of Hypothermosol as the medium of choice.
Further studies will be needed to evaluate the clinical efficacy of this promising technique.
ForHair’s Specific Protocol and Equipment
Temperature Control Device
At ForHair, we use the Cole Instruments Graft Chilling Plate to maintain precise temperature control throughout procedures.
Unlike ice-based systems that can fluctuate as ice melts, the electric chilling device maintains a constant temperature between 2-4°C for the entire duration of surgery.
The device allows dial-in control to specific temperatures, ensuring grafts never experience thermal shock from sudden temperature changes.
Step-by-Step Storage Protocol
Pre-procedure preparation: Hypothermosol solution is pre-chilled to target temperature (2-4°C) before graft extraction begins.
During extraction: Grafts are immediately placed in chilled Hypothermosol in sterile petri dishes positioned on the graft chilling plate.
Continuous monitoring: Laser thermometer checks solution temperature every 15-30 minutes to verify a consistent 2-4°C range.
Maximum hold time: Grafts remain in cold storage for no more than 90 minutes before implantation, though most are placed within 45-60 minutes.
Temperature verification: Any temperature deviation beyond 1-2°C triggers immediate adjustment of chilling plate settings.
Quality Assurance Metrics
We track graft viability through several measurable endpoints. Graft survival rate is assessed at 12 months post-procedure through standardized photography and follicular unit counts.
Transection rates during extraction are monitored in real-time, with our CIT technique maintaining under 3% transection versus 8-15% industry average.
Post-operative shedding patterns are documented through patient follow-up at months 1, 3, 6, and 12 to identify any abnormal effluvium that might suggest storage-related damage.
Current Evidence on Cold Storage vs Room Temperature
What Research Actually Shows
Studies by Kim demonstrated that normal saline at 4°C showed no improvement in graft health unless grafts remained out of the body for more than 6 hours.
However, grafts stored beyond 6 hours showed decreased survival regardless of temperature.
Beehner’s research found that cold storage in normal saline improved survival rates of grafts that experienced crush injury during handling.
More recent studies by Beehner comparing Hypothermosol with ATP versus normal saline showed improved graft survival across multiple storage timeframes, from 2 hours up to 96 hours.
Limitations of Current Data
Most published research on cold storage focuses on major organ transplantation (kidneys, liver, heart) rather than hair follicles specifically.
Hair follicle studies remain limited in sample size and have not been independently reproduced across multiple centers.
No standardized protocol exists for defining “graft survival” consistently across different practices, making comparative studies difficult.
The interaction between storage solution type, temperature, and ischemia time remains incompletely understood for follicular units.
Safety Considerations and Contraindications
When Cold Storage May Not Be Appropriate
Grafts from patients with certain blood disorders or clotting abnormalities may respond differently to hypothermic storage.
Body hair grafts may have different temperature tolerance than scalp grafts due to structural differences, though this hasn’t been systematically studied.
Patients undergoing procedures lasting under 2 hours with minimal graft hold time may see negligible benefit from specialized cold storage.
Potential Risks of Temperature Extremes
Temperatures below 2°C risk ice crystal formation within cells, causing mechanical damage to cell membranes.
Temperatures above 8°C with intracellular solutions (like Hypothermosol) may not provide sufficient metabolic suppression.
Rapid temperature fluctuations can cause additional cellular stress beyond steady-state cold storage.
Device and Solution Regulatory Status
Hypothermosol is FDA-cleared as a hypothermic storage solution for cells and tissues under the original manufacturer’s guidelines.
The Cole Instruments Graft Chilling Plate is classified as a temperature control device for surgical use.
Normal saline and lactated Ringer’s solutions are approved for general medical use but not specifically indicated for follicular storage.
Frequently Asked Questions
Why don’t all hair transplant surgeons use cold storage?
The evidence for cold storage in hair transplants isn’t as definitive as it is for organ transplantation. Many experienced surgeons achieve good results with room-temperature saline, especially when graft hold times stay under 2-3 hours, but this is not the case with most hair transplants. Cold storage may provide more benefit in longer procedures or when grafts experience handling trauma.
How much does cold storage actually improve results?
We don’t have large-scale comparative studies with statistical significance. Early observations in our practice suggest potential improvements in yield, but individual results vary. The real benefit may be in reducing risk during longer procedures rather than dramatically boosting survival in all cases.
Can patients tell if cold storage was used?
Not directly. The potential benefits show up months later in overall graft survival rates and density achieved. There’s no way for a patient to visually confirm cold storage was used during their procedure.
Is Hypothermosol better than regular saline for storage?
Research on other tissue types suggests yes, but hair follicle-specific studies are limited. Hypothermosol is designed to prevent the cellular swelling that occurs when you combine cold temperatures with extracellular solutions like saline. However, it costs significantly more than saline (roughly $58 per procedure vs $4 for saline).
What happens if the temperature drops below 2°C?
Ice crystal formation can occur below freezing, which damages cell membranes. Even temperatures between 0-2°C may cause cellular stress. This is why continuous monitoring with precise temperature control devices matters more than ice-based cooling.
Should I specifically request cold storage for my procedure?
Discuss this with your surgeon. If your procedure involves a large number of grafts , extended surgery time, or you’re undergoing a repair procedure, cold storage protocols may offer additional protection. For smaller, shorter procedures, the benefit may be minimal.
Medical Disclaimer
This article is for educational purposes only and does not constitute medical advice.
Individual results from hair transplant procedures vary based on patient factors, including age, hair characteristics, extent of hair loss, and overall health.
The graft storage methods described represent our clinical approach but have not been validated through large-scale randomized controlled trials.
Patients should discuss specific storage protocols and expected outcomes during consultation with a qualified hair restoration surgeon.
Hypothermosol and other specialized storage solutions are used off-label for hair follicle storage, as they are primarily indicated for other cell and tissue types.
References and Further Reading
For more detailed information on temperature and holding solutions for hair follicles, see our comprehensive article: Optimal Holding Solution and Temperature for Hair Follicle
Additional technical specifications for the Cole Instruments Graft Chilling Device: Product Information
