The vascular effect of cold injury

Endoscopic Palliative Therapies for Esophageal Cancer

Endoscopic palliation of dysphagia for patients with inoperable esophageal cancer is complex, highly dependent on local expertise, and best done in a multidisciplinary fashion. Systemic therapy is the standard of care because it has been shown to improve survival. Esophageal stenting has traditionally been the most used endoscopic modality. Some modalities such as laser and photodynamic therapy are rarely used. There has been an increasing amount of data on cryotherapy, especially for patients with mild-to-moderate dysphagia on systemic chemotherapy. This article will discuss the latest evidence guiding the palliation of esophageal cancer.

[Cryoablation - back again?]

CLINICAL ISSUE

Primary and secondary liver tumors often limit patient outcome and only a minority of patients are eligible for potential curative surgery. Minimally invasive treatments, such as radiofrequency ablation (RFA), microwave ablation (MWA) and cryoablation are alternative treatment options in a curative and palliative setting. One major limitation of RFA and MWA is the limited size of tumor ablation. Furthermore during the procedure the ablation size can only be roughly estimated using RFA and MWA.

STANDARD TREATMENT

RFA is the standard modality of minimally invasive tumor therapy. In comparison cryoablation is rarely used despite its advantages.

TREATMENT INNOVATIONS

Argon-helium-based cryoablation systems of the newest generation combine the advantage of small diameter applicators comparable with those of RFA and MWA systems with intrinsic advantages.

ACHIEVEMENTS

Cryoablation is a minimally invasive treatment option with advantages, such as virtually unlimited ablation size, real-time visualization using computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound and intrinsic analgesic effects. On the other hand it is not very time-efficient in comparison to MWA. Especially in liver metastases RFA is the preferred treatment option.

PRACTICAL RECOMMENDATIONS

Cryoablation is a fascinating treatment option in minimally invasive tumor treatment. It demonstrates good results in hepatocellular carcinoma within the Milan criteria and T1a renal cell carcinoma. Furthermore it is a well-established treatment modality for palliative pain management in bone tumors.

Immediate effect of kidney cryoablation on renal arterial structure in a porcine model studied by imaging cryomicrotome

PURPOSE

Injury to blood microvessels has a crucial role in effective cryoablation for renal masses. We visualized vascular injury induced by a clinically applied cryoablation instrument and established a microvascular diameter threshold for vascular damage.

MATERIALS AND METHODS

In 5 anesthetized pigs 1 kidney each was exposed and 3, 17 gauge cryoneedles were inserted in 1 pole. Tissue was exposed to freezing for 2 x 10 minutes with a 10-minute thaw between freezes. After nephrectomy the arteries were injected with fluorescence dyed casting material and the kidney was frozen to -20C and cut in 40 to 60 micron slices in the imaging cryomicrotome, where fluorescent images of the cutting plane of the bulk were obtained. This resulted in a 3-dimensional image of the arterial tree that was segmented, resulting in unbranched vessel segments. Histograms were constructed with the total segment length per diameter bin plotted as function of diameter.

RESULTS

The ablated zone was sharply demarcated on fluorescent and normal light images. Mean +/- SD diameter at the peak of the histogram from control areas was 152.4 +/- 5.3 micron. Compared to control areas the peak diameter of ablated areas was shifted to a larger diameter by an average of 25.4 +/- 2.6 micron.

CONCLUSIONS

Immediate renal cryoablation injury destroys arteries smaller than 180 micron. Branching structures of larger arteries remain anatomically intact and connected to vascular structures in surrounding tissue.

Cryosurgery: early ultrastructural changes in liver tissue in vivo

BACKGROUND

Experimental observations with regard to freezing in vitro cell lines and fluid systems led to the application of low temperatures to in vivo biological systems. For the first time, this report describes the cryosurgical response of liver parenchyma and the early ultrastructural cellular changes in liver tissue, i.e., cryosurgery, in vivo.

MATERIALS AND METHODS

Forty-eight animals were used for the experiment. The dogs were divided into four groups. In group A, the liver tissue was frozen to -80 degrees C and in group B, to -180 degrees C. Temperatures of -80 degrees C and -180 degrees C in contact with liver tissue was selected for cryosurgical exposure. For transmission electron microscopy, the specimens were taken immediately and 1 h after the finishing of the freeze-thaw cycles intraoperatively. Further, the next specimens were taken in 24 h, this time also intraoperatively.

RESULTS

The electronic microscopic analysis showed that, after local cryodestruction at temperatures of -80 degrees C and -180 degrees C, similar processes occurred within the liver tissue in the early postcryosurgical phase-immediately and 1 h after cryosurgical session. The hepatocytes in the center of the cryozone changed upon thawing. Ultrastructural changes in the hepatic cells, where the first signs of dystrophic processes had been noticed, were increased.

CONCLUSIONS

Our new insights prove on the cell level that suddenly and progressively damaged liver cells in the postcryosurgical zone lead to aseptic cryoaponecrosis and then to aseptic cryoapoptosis of vital normal tissue. The vascular capillary changes and circulatory stagnation demonstrate together with cryoaponecrosis and cryoapoptosis the anti-angiogenesis mechanisms, which are some of the main mechanisms of biological tissue injury following the low temperature exposure.

Cryoablation and resection influences patient survival for soft tissue sarcomas: impact on survivorship and local recurrence

Cryosurgical ablation has been used successfully for treating various carcinomas and bone tumors; however, few studies report the use of cryosurgery followed by tumor resection for the treatment of soft tissue sarcomas. We evaluated local recurrence, progression of disease, histologic necrosis from the cryoablation, complications, patient survival, and functional outcomes using this approach. We retrospectively reviewed 38 patients with no prior treatment for their neoplasm who underwent cryosurgery followed by wide excision of soft tissue sarcomas. Three patients developed local recurrence. Sixteen patients had evidence of more than 95% tumor necrosis, and 11 of these had 100% histologic necrosis. We observed a difference in overall survival and disease-free survival based on the adequacy of freezing process. Patients with more than 95% necrosis had a survival rate of 94% at 2 years and 86% at 5 years, while those with less than 95% necrosis survived 53% at 2 years and 34% at 5 years. Complications included transient neuropraxia (13%), superficial wound infections (8%), and seroma (21%). Cryosurgical ablation appears a safe and effective method of devitalizing tumor cells of soft tissue sarcomas.

Focal cryogen insults for inducing segmental osteonecrosis: computational and experimental assessments of thermal fields

Orthopaedic management of femoral head osteonecrosis is a common clinical problem for which there presently is no good solution. Current animal models are inappropriate to study potential new solutions, since it has been difficult to replicate the natural history of structural collapse seen in the human disorder. Recently, progression to collapse was obtained for cryogenically induced osteonecrosis in emus, although the lesions involved were imprecisely controlled in terms of size or location. A new cryo-insult probe is here reported for the purpose of delivering well-prescribed local thermal insults in this new animal model, while minimizing damage to non-targeted regions. Finite element analysis was used to elucidate the influence of operator-controlled parameters upon the temporal/spatial variation of the thermal field. The numerical formulation includes convective heat transfer attributable to tissue bed perfusion. The computational results agreed closely with the results of thermocouple recordings in a companion bench-top experiment. The cryo-insult probe successfully produced segmental lesions in the emu model of sizes comparable to the computed freeze front diameters.

Cryosurgical ablation of soft tissue sarcomas: a phase I trial of feasibility and safety

BACKGROUND

Cryosurgery is a therapeutic method of treating neoplastic tissue by freezing in situ to achieve devitalization. Cell death results from exposure to severe cold (below -40 degrees C for at least 1 minute) as well as from the process of freezing and thawing, which disrupts cellular integrity. Modern cryosurgical technique involves insertion of hollow probes into the tumor, through which circulating liquid nitrogen and gaseous nitrogen can achieve tissue and tumor freezing and thawing for tumor control. Cryoablation is now a recognized approach to the treatment of various malignant tumors, and it is generally well tolerated. This method has been used only sporadically to date in the treatment of patients with soft tissue sarcomas.

METHODS

The purpose of this study was to assess the feasibility and safety of cryosurgical ablation of soft tissue sarcomas utilizing a cryoprobe system. Twelve patients with soft tissue tumors of the extremity were included in this Institutional Review Board-approved protocol. Cryoablation was performed by inserting cryoprobes into the tumors, through which liquid nitrogen and gaseous nitrogen were pumped to achieve two freeze/thaw cycles. The entire process was monitored with intraoperative ultrasonography. All patients had subsequent resection of the residual tumor. Patients were monitored clinically and metabolically for toxicity.

RESULTS

Cryoablation was successfully performed on all 12 patients. Complications included peripheral nerve palsy (in 3 patients) and serous wound drainage (in 3 patients). There were no cases of wound infection, deep venous thrombosis, pulmonary embolism, wound dehiscence, skin slough, or metabolic abnormalities. All 3 cases of peripheral nerve palsy showed signs of recovery, 2 within 1 week and 1 within 4 months.

CONCLUSIONS

Cryosurgical ablation of soft tissue sarcomas is technically safe and feasible. This method can be used in conjunction with other modalities in the treatment of patients with these tumors. The complications associated with cryoablation of sarcomas are minor or transient, and the procedure is well tolerated by patients. The role of cryosurgery in the management of soft tissue sarcomas needs to be elucidated as more data regarding its safety and effectiveness become available.

Mechanisms of tissue injury in cryosurgery

As the modern era of cryosurgery began in the mid 1960s, the basic features of cryosurgical technique were established as rapid freezing, slow thawing, and repetition of the freeze-thaw cycle. Since then, new applications of cryosurgery have caused numerous investigations on the mechanism of injury in cryosurgery with the intent to better define appropriate or optimal temperature-time dosimetry of the freeze-thaw cycles. A diversity of opinion has become evident on some aspects of technique, but the basic tenets of cryosurgery remain unchanged. All the parts of the freeze-thaw cycle can cause tissue injury. The cooling rate should be as fast as possible, but it is not as critical as other factors. The coldest tissue temperature is the prime factor in cell death and this should be -50 degreesC in neoplastic tissue. The optimal duration of freezing is not known, but prolonged freezing increases tissue destruction. The thawing rate is a prime destructive factor and it should be as slow as possible. Repetition of the freeze-thaw cycle is well known to be an important factor in effective therapy. A prime need in cryosurgical research is related to the periphery of the cryosurgical lesion where some cells die and others live. Adjunctive therapy should influence the fate of cells in this region and increase the efficacy of cryosurgical techniques.

Changes in adrenergic nerves and tissue perfusion after freezing injury to the ear skin of rabbits

The aim of the present study was to investigate by a combined trypan blue and catecholamine fluorescence technique the sequential changes in cutaneous adrenergic nerves, the distribution of blood flow, and vascular permeability at the demarcation line that occurred after experimental cold injury. Nine New Zealand white rabbits weighing 4.0-4.4 kg had frostbite induced by pressing the bottom of a glass bottle 2 cm in diameter filled with liquid nitrogen against the shaved skin of the ear. All the rabbits were anaesthetised with ketamine hydrochloride (Ketamine) and xylazine hydrochloride (Rompun). Specimens were taken one and three days, and two weeks after frostbite. Control samples were taken from the opposite normal ear. Trypan blue was injected into a saphenous vein just before the specimens were taken. The specimens were always taken in the same way and selected so that the probable demarcation line of the frostbite ran across the middle. The glyoxylic acid-induced fluorescence method was used to show the adrenergic nerves. There were no adrenergic nerves around the vessels and no arteriovenous anastomoses in the central area of the injury after one day, but catecholamines had started to accumulate in the adrenergic nerve endings at the margins of the injured area. This accumulation was still more obvious three days after frostbite. Some fluorescent regenerating adrenergic nerves could already be seen at the probable demarcation line two weeks after frostbite. There was increased trypan blue fluorescence near the margin of the injured area after one day, indicating extravasation and vascular damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cryothermia during cold cardioplegia on epicardial and intramural coronary arteries

Cryosurgery is playing an increasingly important role in the surgical treatment of various supraventricular and ventricular tachyarrhythmias. The short-term and long-term effects of cryogenic injury on epicardial and intramural coronary arteries were studied in 22 dogs. Transmural cryolesions encompassing a posterolateral branch of the circumflex coronary artery were produced in the inferior left ventricular wall during extracorporeal circulation and cold cardioplegic arrest. The mean epicardial cryolesion area +/- standard deviation was 10.4 +/- 1.8 cm2. The mean epicardial coronary artery diameter +/- standard deviation measured 1.2 +/- 0.4 mm. At 6 hours, no important structural changes were noted in any of 6 dogs. At 48 hours, 1 of 2 epicardial coronary arteries showed recent thrombus. At 1, 3, and 6 months, the epicardial coronary arteries were occluded due to thrombosis and intimal hyperplasia in 13 of 14 dogs. A limited degree of recanalization was observed. At all follow-up intervals, the intramural coronary arteries exhibited a histologic pattern similar to that of the epicardial coronary arteries. It is concluded that the exposure of major epicardial coronary arteries to cryoinjury during cold cardioplegic arrest should be avoided where possible.

The process of freezing and the mechanism of damage during hepatic cryosurgery

Experiments were performed to correlate the structures of liver tissue frozen during cryosurgery, liver frozen at various constant cooling rates, and unfrozen, dried normal liver. The results show that during freezing of tissue ice forms and propagates along the vascular system, expanding during freezing at low cooling rates. This expansion occurs over most of the region frozen during cryosurgery and may be one of the mechanisms of damage to tissue during cryosurgery.

Cardiac cryosurgery: regional myocardial blood flow of ventricular cryolesions

Cryosurgery is one of three methods introduced recently for the treatment of ventricular tachyarrhythmias. Cryothermic exposure ablates arrhythmogenic ventricular myocardium, and produces a dense fibrous scar with a sharp border to histologically normal tissue. Myocardial blood flow in the region of the cryolesion, however, has not been quantitated. The purpose of this study was to measure regional blood flow within and around the cryolesion in an attempt to identify ischemic zones that might become arrhythmogenic. Left ventricular cryolesions were created in eleven adult dogs. Two weeks later, the animals underwent radioactive tracer microsphere injection for quantitation of regional myocardial blood flow. The fibrotic cryolesion demonstrated a significantly depressed blood flow (0.44 +/- 0.07 ml/min/g) compared to blood flow in control tissue (1.36 +/- 0.12 ml/min/g) (P less than 0.001). A 1-mm strip of myocardium immediately adjacent to the cryolesion, as well as other myocardium surrounding and subjacent to the cryolesion, did not show a significant decrease in regional blood flow. The border between the fibrotic cryolesion and the surrounding myocardium is, therefore, sharply defined not only in terms of histology but also in regards to regional blood flow. These data lend further support to the safe clinical use of cryothermia in the treatment of refractory ventricular tachycardia.

Identification of vascular system in experimental carcinoma for cryosurgery--histochemical observations of lectin UEA-1 and alkaline phosphatase activity in vascular endothelium

Histopathologic and histochemical changes in experimental carcinomas following cryotreatment were observed to detect alkaline phosphatase (ALP) activity and UEA-1 lectin binding. Experimental carcinomas were induced in the hamster cheek pouch by topical application of 0.5% DMBA acetone solution twice a week. The cryoprobe at -60 degrees C was directly attached to the tumor surface for 90 sec. Histochemically, the tumor tissue following cryotreatment was completely destroyed in the surface area by the direct freezing and such cryonecrotic tumor tissue lacks stainability. Soon after cryotreatment and before cryonecrosis takes place, it has been observed that there is an intense dilatation of capillary vessels. Histochemically, high ALP activity was limited to capillary endothelium and to inflammatory cells. Lectin UEA-1 staining was usually found in both normal and neoplastic epithelial cells which were confined to capillary vessels. At 1 to 3 hr after cryotreatment, lectin UEA-1 binding was also positive in dilated endothelial cells of the frozen tissue as well as viable remaining neoplastic epithelia by freezing. ALP activity and UEA-1 binding disappeared in capillaries of cryonecrotic area in tumor tissues. Those findings suggest that biologic membrane changes in capillary endothelium of tumor stroma occur following cryotreatment.

Histologic and histochemical changes in experimental carcinomas following cryosurgery

Histologic and histochemical changes in experimental SCCs following cryosurgery were reported. Effects of cryosurgery on SCCs of hamster cheek pouch were classified into 3 zones; the superficial zone was the cryodestructive layer on which the cryoprobe had been attached directly to the SCC; the zone beneath this layer was the indirect cryodestructive layer; the 3rd zone was unaffected tissue in which the critical low temperature was never reached. In the superficial cryodestructive layer, tumor cells were destroyed completely and bleeding was found in the stroma. In the zone beneath it, neoplastic cells also showed morphologic and enzymatic changes indicating incomplete cellular destruction; dilatation of capillary vessels was also found. LDH isozyme pattern displayed a high level of LDH 5 in the non-treated SCC, and following cryosurgery, the high level of LDH 5 decreased and revealed an approximately normal LDH 5 pattern.

Cryosurgery for cardiac arrhythmias: acute and chronic effects on coronary arteries

The use of cryosurgery near major coronary arteries for the treatment of supraventricular and ventricular tachyarrhythmias has caused concern over the possible deleterious acute and chronic effects of cryothermia on vessel patency and integrity. The present study was designed to examine both the acute and chronic effects of cryothermia on major coronary vessels in an experimental model that simulates clinical conditions. In the acute phase of the study, 10 dogs underwent direct cryothermic exposure of the left anterior descending (LAD) coronary artery while coronary artery flow and regional myocardial blood flow were calculated. Direct cryothermic exposure of the LAD resulted in total cessation of LAD blood flow 20 +/- 4 seconds after institution of cryothermia. Arterial patency returned 29 +/- 8 seconds after termination of cryothermic exposure. In the second phase of this study, 16 dogs had cryolesions applied directly over the LAD at myocardial temperatures of 37 degrees C and during elective cardioplegic arrest at myocardial temperatures of 6 to 12 degrees C. In addition, cryothermia was applied directly to the coronary sinus in these animals. The animals were allowed to live either 48 hours, 2 weeks, or 6 months after the initial procedure, and the cryolesions and underlying vessels were examined histologically. Although coronary arteriography at 6 months showed all coronary arteries to be patent, microscopic examination revealed coronary intimal hyperplasia to be present in the majority of the coronary arteries at the site of the cryolesion, particularly if the cryolesion had been applied during hypothermic, cardioplegic arrest. Cryothermia had no effect on the coronary sinus. This study provides evidence for cryothermia-induced coronary arterial damage that may produce hemodynamically significant coronary artery stenosis and suggests that caution be exercised when it is necessary to create cryolesions in the vicinity of major coronary arteries.