Extracorporeal whole body hyperthermia treatment of HIV patients, a feasibility study

Thermal distribution, physiological effects and toxicities of extracorporeally induced whole-body hyperthermia in a pig model

Background

Extracorporeally induced whole‐body hyperthermia (eWBH) might be a beneficial treatment in cancer patients. Objectives of this pig study were to assess thermal distribution, (patho‐)physiological effects, and safety of eWBH with a new WBH device.

Methods

Fourteen healthy adult pigs were anesthetized, mechanically ventilated, and cannulated; 12 were included in the analysis. Blood was heated in 11 pigs (one pig served as control) using a WBH device (Vithèr Hyperthermia B.V.) containing two separate fluidic circuits and a heat exchanger. Temperature was monitored on nine different sites, including the brain. Core temperature (average of 4 deep probes) was elevated to 42°C for 2 hr.

Results

Elevation of core body temperature to 42°C took on average (± standard deviation) 38 ± 8 min. Initially observed temperature spikes diminished after lowering maximal blood temperature to 45°C. Hereafter, brain temperature spikes never exceeded 42.5°C, mean brain temperature was at highest 41.9°C during maintenance. WBH resulted in increased heart rates and decreased mean arterial pressures. The vast amounts of fluids required to counter hypotension tended to be smaller after corticosteroid administration. Hemodialysis was started in three animals (potassium increase prevention in two and hyperkalemia treatment in one). Severe rhabdomyolysis was observed in all pigs (including the control). All animals survived the procedure until planned euthanasia 1, 6, or 24 hr post procedure.

Conclusion

Fast induction of eWBH with homogenous thermal distribution is feasible in pigs using the Vithèr WBH device. Severe hemodynamic disturbances, rhabdomyolysis, and hyperkalemia were observed.

Cerebral pathophysiology and clinical neurology of hyperthermia in humans

Deliberate hyperthermia has been used clinically as experimental therapy for neoplastic and infectious diseases. Several case fatalities have occurred with this form of treatment, but most were attributable to systemic complications rather than central nervous system toxicity. Nonetheless, demyelating peripheral neuropathy and neurological symptoms of nausea, delirium, apathy, stupor, and coma have been reported. Temperatures exceeding 40 degrees C cause transient vasoparalysis in humans, resulting in cerebral metabolic uncoupling and loss of pressure-flow autoregulation. These findings may be related to the development of brain edema, intracerebral hemorrhage, and intracranial hypertension observed after prolonged therapeutic hyperthermia. Furthermore, deliberate hyperthermia critically worsens the extent of histopathological damage in animal models of traumatic, ischemic, and hypoxic brain injury. However, it is unknown whether these findings translate to episodes of spontaneous fever in neurologically injured patients. In a clinical setting fever is a strong prognostic marker of a patient's primary degree of neuronal damage, and a causal relation with long-term functional neurological outcome has not been established for most types of brain injury. Furthermore, in the neurosurgical intensive-care unit fever is extremely common whereas antipyretic therapy is only poorly effective. Therefore maintaining strict normothermia may be an impossible goal in many patients. Although there are several physiological arguments for avoiding exogenous hyperthermia in neurologically injured patients, there is no evidence that aggressive attempts at controlling spontaneous fever can improve clinical outcome.

pKa of Fentanyl Varies With Temperature: Implications for Acid-Base Management During Extremes of Body Temperature

OBJECTIVE

The pKa of fentanyl has not been measured previously at varying extremes of body temperature. The goal of this laboratory investigation was to test the hypothesis that the pKa of fentanyl changes with temperature.

DESIGN

The investigation involved measuring the pKa values of aqueous fentanyl at varying temperatures.

SETTING

The investigation was conducted in a controlled laboratory environment.

PARTICIPANTS

No human or animal subjects were involved.

INTERVENTIONS

Because no live subjects were involved in the investigation, no interventions were necessary.

MEASUREMENTS AND MAIN RESULTS

This paper reports the effect of temperature on the pKa of fentanyl. The pKa of aqueous fentanyl was measured at 15 degrees C, 25 degrees C, 37 degrees C, 42 degrees C, and 47.5 degrees C by potentiometric titration in 0.01 mmol/L of potassium chloride after extensive degassing. Data were analyzed using the least squares method with an appropriately fitting equation. The pKa of fentanyl was found to change in a similar manner to the neutral point of water at varying temperatures.

CONCLUSIONS

This finding has implications for the bioavailability of fentanyl at extremes of body temperature in association with the clinical acid-base management of the patient. Clinical implications for differing methods of intraoperative acid-base management at varying temperatures are discussed.

Heat shock proteins: novel therapeutic tools for HIV-infection?

Heat shock proteins (Hsps), cyclophilins (Cyps) and FK binding proteins (FKBPs) form a family of intracellular chaperone molecules that facilitate protein folding and assembly. These stress proteins are selectively expressed in cells in response to a range of stimuli, including heat, lymphokine and microbial/viral infections. This review discusses the role of stress proteins in the HIV-1 viral life cycle, with regard to the development of specific Hsp-based therapeutic strategies against HIV-1 infection. Cumulative findings are cited implicating CypA, Hsp27, Hsp70 and FKBPs in host cell and viral activation, viral entry, assembly or formation of infectious virions. Biological response modifiers that show specific high-affinity interactions with Cyp, FKBPs and Hsps, including cyclosporins, FK-506 and cyclopentenone prostaglandins respectively, may block HIV-1 replication and infection, providing novel HIV-1 therapeutic strategies. Moreover, Hsp binding to viral complexes can enhance antiviral immunity, including natural killer (NK), antibody-dependent (ADCC), gamma delta T-cell and cytotoxic T-lymphocyte (CTL) activities against HIV-1 infected cells. The ability of Hsps to interact with HIV-1 viral proteins, combined with their inherent adjuvant and immunogenic properties indicates that Hsps may also serve as vehicles for antigen delivery and the design of AIDS vaccines.