A high level of body temperature (43°C) is needed for effective use of whole body hyperthermia. Such high level hyperthermia can only be safely used, taking into account a theory of developing post-aggressive hyperproteolysis.^1,2 Besides the control of proteolysis it is also necessary to apply a total phentanyl anesthesia, high-frequency artificial lung ventilation and maintain a high rate of heating.³ Clinical application of this method allows inducing the apoptosis of malignant cells, decreasing the viral load in HIV and HCV-infected patients also causing a general sanitary effect. Use of water immersion makes the technology noninvasive and “physiological”. Application of this developed whole body hyperthermia technology leads to a noticeable reduction of artificial ventilation time and practical exclusion of complications.^4-7

Introduction

It is known, that therapeutic opportunities of the thermal factor are used since ancient times. However, in the 20th century scientists and physicians have reached essential results in application of hyperthermia in treatment of oncological, immunological, viral and other diseases. Necessity of development and improvement of hyperthermic technologies was predetermined because of insufficient efficacy of commonly used surgical, pharmacological, immunobiological and other methods of treatment of dangerous (oncological, viral, immunological) diseases and detection of unknown clinical effects of a hyperthermia.

Those clinical significant effects are:

1. Destruction of malignant cells due to induction of necrobiosis and apoptosis by the thermal factor.
2. Elimination of tolerance of malignant cells to chemotherapy
3. Potentiation of medical effects of chemotherapy in combination with hyperthermia. It allows to reduce dosages of chemotherapy, decreasing damaging effect to the healthy tissues and keeping antineoplastic activity.
4. Acativation of immunomodulating effects of hyperthermia, increase of protective forces of the patient, which important and never occurs after chemo- and radiotherapy.

Necessity of High-Level Whole Body Hyperthermia

It is known that there are no universal solutions for technical realization of artificial hyperthermia and for choosing its rational temperature range. Different variants of local and whole body hyperthermia (wave, immersion and perfusional) should not be opposed to each other. It is necessary to take into account the concrete clinical situations to achieve the maximal medical effect.

Below we summarize arguments which were taken into account at studying and applying a high level (extreme) hyperthermia (up to 44.0°C).

First of all, it is important to reply: why is it necessary to achieve WBH above 43°C? The answer to this question is obvious not only for oncology, but also for those areas of medical practice where a selective cell damaging effect of heat is required. In particular, it is actual for oncological, virological and allergological practice, when it is necessary to initiate a necrobiosis and apoptosis of malignant cells, to suppress the HIV-infection or to destroy para-proteins and pathological antibodies.

Some inspiring results in this field have been already received. So E. Kano (1987)⁸ has established, that “… energy of activation of heat cell killing at temperatures from above 43.0°C and below 43.0°C is equal to 150 kcal / μ and 360 kcal / μ accordingly …” Thus, on the one hand it is possible “to examine” an organism of the cancer patient protractedly on its nonspecific resistance to temperature up to 41°C during 1-3 hours per hope that cancer cells in his organism appear less steady against the increased temperature. On the other hand, in conditions of adequate anesthetic protection, rapidly provide the 43.0-43.5-44.0°C level of hyperthermia and to start the biological mechanism of apoptosis in cancer cells. We shall note, that doctor Kano with colleagues within the next 10 years repeatedly confirmed reliability of the phenomenon registered by them certainly accepted by us in attention. Also it is necessary to note, that Mathe G. on XXIVth Congress in Rome (September 2001) also has confirmed, that “… apoptosis of cancer cells is started only at achievement of temperature in 43.0°C …”

The authority of these and other known scientists allows to consider that high level hyperthermia (above 43°C) is basic for oncological practice. Moreover, application of whole body hyperthermia in an interval of 40-42°C is fraught with a potential danger of dissemination of malignant cells and stimulation of their growth.

Risk Factors of Whole Body Hyperthermia Over 43°C and Pathogenetic Substantiation of Their Overcoming

It is known, that homoiothermic organisms “…are sheltered right at the threshold of thermal death…” Artificial realization of whole body hyperthermia even in an interval of 41.8-42.0°C is bound to the risk of development of dangerous complications. Those are:

• Thermal shock,
• Brain edema,
• Acute circulatory insufficiency,
• Hepato-renal syndrome,
• Acute respiratory distress syndrome (ARDS)
• Disseminated intravascular coagulation

The probability of occurrence of the specified complications is especially great in patients with oncological pathology; in elderly and senile age, when hyperthermia application is compelled on a background of multiple organ failure and the general bad state of health. In this connection at the 32^nd Congress in Okayama (1994)¹⁰ it was noticed, that whole body hyperthermia up to 43°C is desired for clinical practice, but mortality reaches a level of 17%.

However our experience in whole body hyperthermia over 43°C with more than 500 patients, who successfully and repeatedly undergone this procedure with no complications and multiple organ failure, is a basis to assert about a basic opportunity of safe extreme hyperthermia.

Below there are some pathogenetic positions by which we were guided during development and perfection of high level whole body hyperthermia (43.5-44.0°C).

It is known, that “…during cell reactions to damaging agents, plasmic proteins undergo the reversible structural changes keeping nuclear composition invariable...”¹¹ Such changes are happen by turns of nuclear groups around the single bonds.

The essence of conformational changes of proteins is in redistribution of binding energy which can result in breaks of existing and establishment of weak bonds supporting secondary, tertiary and quaternary structure of a protein molecule.¹²

It is known, that the spatial structure of a protein molecule is supported by various forces. Hydrogen bridges are established between oxygen of carbonyl groups of one amino acid with the imine nitrogen of another (N-H …. O=C). They basically support the secondary structure of protein molecules. Covalent disulfide bonds (-S-S-) can participate in architectonics of tertiary structure. Influence of hydrophilic and hydrophobic sites of a protein molecule on an arrangement of water in their nearest environment creates quaternary structure determining stability of a protein macromolecule.

It is also known, that the temperature maximum of stability of the most of proteins is much lower than a temperature of their vital optimum. Hence, the rise of temperature over an optimum should reduce stability of the protein molecules. And, the rise of temperature is more intensively destabilizing the periphery, the most reactive parts of macromolecules which are remote from an internal hydrophobic nucleus globule.

Process of denaturation is more or less a complete destruction of quaternary, tertiary and secondary structure without hydrolytic splitting of peptide bonds. Increased temperature, in comparison with others well-known denaturation agents (urea, alcohol, acetamide) is the most universal “destructor” of macromolecular structures. Certainly, increasing a temperature, depending on its level and time of exposure, macromolecule changes occur step-by-step: from light disturbances of a stereochemical configuration to the formation of more or less chaotic clews of polypeptide bonds with a complete loss of function (Fig. 1).

Figure 1

The process of reversible temperature disintegration of protein structure.

If the disturbances in macromolecular structure are incomplete, the termination of heating and decrease of temperature to an initial level enables renaturation. Restoration of initial, native structure and renewal of function is considerably longer than damage and depends on both a depth of reversible denaturation and the type of protein macromolecule.

In our experience, after heating the patient up to 44°C, a process of functional restoration of various protein structures lasts from 2 till 8-16 hours. In this period, meeting the certain conditions, the structure and function of protein macromolecule are gradually restored. However, the given pattern has an exception relevant to the unique enzyme trypsin. It is known, that this enzyme with rather simple structure and small molecular weight, can completely restore its structure and function within 10-15 min. after heating up to 43-44°C! Thus, a dangerous pathogenetic situation appears. A huge amount of partially denaturated proteins (substratum) and an increase in active, nonspecific exo-endoproteinase (trypsin). Not without reason, Lehninger¹³ and Szent-Gyorgyi compared it to a “spring” or a “zipper”. Proteinases also are denaturising agents. They destruct not only complicated structures but also even peptide bonds, breaking a primary structure of protein. The high activity of proteolysis in an overheated organism causes accumulation of a plenty of oligopeptides inducing endotoxemia. In other words, for many protein structures: the high temperature causes partial denaturation, and proteolysis destroys macromolecules (Fig. 2).

Figure 2

Participation of trypsin in hyperthermic proteolysis.

In our opinion, a pathogenetic pattern mentioned above, is the one of key positions that should be taken into account for safe performance of extreme whole body hyperthermia. We established, that the phenomenon of hypertrypsinemia is a typical, nonspecific reaction of an organism to any stress and shock (Fig. 3).

Figure 3

Activity of trypsin in blood of rats at 1 hour after aggression.

The data given in Figure 3, shows that high trypsin activity in blood of experimental animals was registered within 1 hour after any stress. We revealed, that the source of trypsinemia are the zymogenic granules of the pancreas, from which the shock enzyme “evades” into the bloodstream and causes a hyperproteolysis and endotoxemia. Hence, at anaesthetic management of high-level artificial hyperthermia is necessary to prevent hypertrypsinemia and to control proteolysis.

What Are Possible Ways to Suppress the Activity of Trypsin during Hyperthermia?

It appears to be a problem because polyvalent proteinase inhibitors, commonly used in clinical practice, have a protein nature and denaturise at high temperature. In other words, the target was an alternative way of proteinase inhibition.

Searching for a pharmacological preparation, capable to inhibit the activity of trypsin, the attention was drawn to clinical application of formaldehyde, described in V.V. Kovanov's works (1980-1982).¹⁴ It was established later, that formaldehyde blocks the action of proteolytic enzymes of trypsin type and can essentially reduce a proteolytic activity of the blood. As intravenous introduction of formaldehyde is not permitted by the pharmacopoeia, an alternative variant of its application was found. It lies in the application of hexamethylenetetramine which is commonly used in medical practice. This preparation introduced to the blood can split into formaldehyde and ammonia, on condition that liver and kidneys are functioning normally.

Considering the above arguments, hexamethylenetetramine can be validly used in patients with a hyperactivity of trypsin. Using this preparation a relevant decrease of trypsin activity from levels of 2.34-9.72 MED to 0.2-0.3 MED was noted.

The optimum doze of hexamethylenetetramine (80 mg/kg) and its half-time excretion (4-6 hours) were found empirically using recommendations of the pharmacopoeia.

It is a very important point of a problem, taking into account an essential circumstance: most frequently antiproteinase preparations used in medical practice (Trasilol, Contrical, Gordox, etc.) are ineffective in trypsinemia and absolutely not effective at high temperature.¹⁵ It happens because the specified polyvalent trypsin inhibitors have protein structure and are subjected to disintegration by temperature. On the contrary, the formaldehyde formed in blood at hydrolysis of hexamethylenetetramine, keeps the antiproteinase properties even at 44°C.

Thus, one of the basic conditions of a safe whole body extreme hyperthermia (> 43°C) was met by a maximal suppression of proteolytic activity in blood. This became possible in view of the concept about a negative role of postaggressive trypsinemia and the finding of an alternative way to inhibit the trypsin activity.

Technological and Anaesthetic Features of Whole Body Severe Hyperthermia

To achieve a condition of controlled whole body extreme hyperthermia, we use a simple variant of immersion-convectional for physical heating of a patient's body. Patient is under general anaesthesia, heating with a water, warmed up to 44.0-47.0°C. The process of active physical heating is carried out in a special bath, for example “CHIRANA” (Fig. 4).

Figure 4

A general view of active immersion-convectional heating of the patient.

The patient's body and extremities immersed in warmed water except the head. No cranio-cerebral hypothermia is performed during the process of heating. Process of active heating should be fast enough (0.2-0.5°C/min.). Registration of the body temperature of the patient is made with thermal sensors, installed in a gullet. Process of heat transfer is reached by the relevant peripheral vasodilatation and hyperkinetic reaction of circulatory system. That provides equalization of a temperature gradient between peripheral and the central organs. After achievement of a necessary level of hyperthermia, the process of heating stops and the patient is taken from a bath. The further process of normothermia restoration occurs passively and usually lasts 35-45 minutes. The specified method of whole body hyperthermia is achieved under conditions of special anaesthetic protection, whose goal is prevention of probable complications. To avoid such complications it is necessary to meet a number of indispensable conditions:

1. Special preprocedural preparation
2. Total intravenous anaesthesia
3. Control of proteolysis
4. Application of high-frequency artificial lung ventilation
5. Maintenance of high rate of active heating
6. Special monitoring of homeostasis.

Clinically relevant effects of whole body hyperthermia technology (43-44°C), can be illustrated by the following facts:

1. Disappearance of multiple melanoma metastases in liver (Fig.5).
2. Fast decrease of HIV-1 RNA plasma concentration in HIV-infected patient (Fig. 6).
3. Removal of abstinence syndrome and total elimination of physical addiction in patients with drug abuse (Heroin, Methadone).
4. Elimination of an allergen (chloropicrin) and circulating immune complexes from the plasma of a patient with atopic bronchial asthma (Fig. 7).
5. Normalization of lung function parameters in a patient with atopic bronchial asthma (Fig. 8).

Figure 5

Disappearance of multiple melanoma metastases in liver.

Figure 6

Fast decrease of HIV-1 RNA plasma concentration in HIV-infected patient.

Figure 7

Elimination of an allergen (chloropicrin) and circulating immune complexes from the plasma of a patient with atopic bronchial asthma.

Figure 8

Normalization of lung function parameters in a patient with atopic bronchial asthma.

Conclusion

Until now the relevant negative activity of proteolysis was not taken into account when handling a problem of endotoxication caused by extreme thermal exposure. Developing of trypsin inhibition method during thermal exposure can exclude endotoxication and significantly decrease a number of hyperthermic complications. Further clinical trials are warranted.

References

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