Nitrogen embolus as a complication of hepatic cryosurgery

New Trends in the Surgical Treatment of Colorectal Cancer Liver Metastases

Colorectal cancer is one of the most common solid tumors affecting people around the world. A significant proportion of patients with colorectal cancer will develop or will present with liver metastases. In some of these patients, the liver is the only site of metastatic disease. Thus, surgical treatment approaches are an appropriate and important treatment option in patients with liver-only colorectal cancer metastases. Resection of colorectal cancer liver metastases can produce long-term survival in selected patients, but the efficacy of liver resection as a solitary treatment is limited by two factors. First, a minority of patients with liver metastases have resectable disease. Second, the majority of patients who undergo successful liver resection for colorectal cancer metastases develop recurrent disease in the liver, extrahepatic sites, or both. In this paper, in addition to the results of liver resection for colorectal cancer metastases, we will review the results of cryoablation, heat ablation, and hepatic arterial chemotherapy using a surgically implanted pump. Each of these surgical treatment modalities can produce long-term survival in a subset of patients with liver-only colorectal cancer metastases, whereas systemic chemotherapy used alone rarely results in long-term survival in these patients. While surgical treatments provide the best chance for long-term survival or, in some cases, the best palliation in patients with colorectal cancer liver metastases, it is clear that further improvements in patient outcome will require multimodality therapy regimens.

Microbubbles

Gas embolism is a known complication of various invasive procedures, and its management is well established. The consequence of gas microemboli, microbubbles, is underrecognized and usually overlooked in daily practice. We present the current data regarding the pathophysiology of microemboli and their clinical consequences. Microbubbles originate mainly in extracorporeal lines and devices, such as cardiopulmonary bypass and dialysis machines, but may be endogenous in cases of decompression sickness or mechanical heart valves. Circulating in the blood stream, microbubbles lodge in the capillary bed of various organs, mainly the lungs. The microbubble obstructs blood flow in the capillary, thus causing tissue ischemia, followed by inflammatory response and complement activation. Aggregation of platelets and clot formation occurs as well, leading to further obstruction of microcirculation and tissue damage. In this review, we present evidence of the biological and clinical detrimental effects of microbubbles as demonstrated by studies in animal models and humans, and discuss management of the microbubble problem with regard to detection, prevention, and treatment.

MR-guided interstitial cryotherapy of the liver with a novel, nitrogen-cooled cryoprobe

The purpose of the study was to test a newly developed, MR-compatible, liquid nitrogen-cooled cryoprobe. The probe has an outer diameter of 3.5 mm and was specifically developed for percutaneous, MR-guided, interstitial cryotherapy. The probe was inserted percutaneously into the livers of 10 rabbits. The cryotherapy procedure was monitored with a surface coil in a 1.5 Tesla magnet using a gradient echo sequence. Follow-up examinations were performed 3 and 7 days after the freezing procedure using T1- and T2-weighted spin echo sequences. At 7 days the animals were sacrificed and the cryolesions were examined histologically. The cryoprobe enabled artifact-free MR imaging of the "iceball" formation during freezing of the rabbit liver. After 1 min of freezing, the iceball at the tip of the probe showed an average maximum diameter of 10.8 mm. No bleeding complications were observed during or after the freezing procedure. Histologic examination 7 days after cryotherapy confirmed that the liver lesions were the same size as had been predicted by the images of the acute iceball. This new, percutaneously inserted, MR-compatible, liquid-nitrogen cooled cryoprobe allows accurate, artifact-free MR imaging of interstitial cryotherapy.

Cryosurgical ablation of unresectable hepatic tumors

Ultrasound-guided hepatic cryosurgery is a potential treatment option for select patients with unresectable tumors. Intraoperative placement of cryoprobes and monitoring of tumor freezing with ultrasonography produce complete remission in 22% to 29% of patients with unresectable metastatic colorectal tumors to the liver. Perioperative nurses should be knowledgeable about cryosurgical techniques and be prepared to participate in this innovative treatment modality to provide optimal care to surgical patients.

Treatment of colorectal cancer: hepatic metastasis

Almost one-third of patients dying from colorectal cancer have tumor limited to the liver. Systemic chemotherapy is the appropriate palliative management of patients with metastases to the liver and other sites. For many patients with isolated hepatic metastases, systemic chemotherapy is also the most appropriate treatment. However, results with systemic chemotherapy indicate that one-third or less of patients will respond to such treatments, and long-term survival is rare. In this report we provide information concerning the natural history of colorectal hepatic metastases, followed by the expected benefits with systemic chemotherapy. This information provides background for the regional therapeutic strategies of surgical resection, cryosurgery, and hepatic artery chemotherapy. We discuss the selection factors appropriate for such treatments, morbidity and mortality, and the potential long-term benefits of such approaches. The last section focuses on surgical considerations in hepatic resection and hepatic artery chemotherapy.

Gas Embolism: Part I. Venous Gas Emboli

Gas emboli syndromes occur in many different settings, and their medical significance ranges from being life-threatening emergencies to being totally innocuous. We discuss venous gas embolization in Part I of this review, and it can result from a variety of traumatic, diagnostic, therapeutic, and surgical interventions. The pathophysiological consequences depend on where the gas bubbles impact and obstruct the circulation—by creating an “air lock” in the right ventricle, by obstruction of pulmonary arterioles, and sometimes with passage into the arterial circulation (so called paradoxical emboli). Various monitoring techniques are available and are known to be useful in high-risk patients. Nevertheless, the diagnosis can be difficult to establish. Myriad and generally nonspecific clinical manifestations may be present; the patient may often exhibit signs and symptoms suggestive of other acute cardiopulmonary or central nervous system events. The classically described “mill-wheel murmur” is actually a rare finding, and it is transient at best. There are no specific diagnostic tests available, and clinicians, must depend on a high level of suspicion in the appropriate settings. Rapid identification of the problem, with prevention of further gas entry into the venous circulation, should be a routine measure. The left lateral decubitus position, administration of 100% oxygen, and hyperbaric oxygenation should all be considered, and they have been shown to be effective treatment modalities.

Surgical options in the treatment of hepatic metastasis from colorectal cancer

Current data indicate that liver resection is the only available treatment that regularly produces long-term survival with possible cure in patients with metastatic colorectal carcinoma to the liver. Although a number of clinical or pathologic factors predicts a poor outcome, the only absolute contraindications to liver resection are general health incompatible with recovery from major hepatic resection or clear evidence of wide dissemination of disease. Important areas for future study include the potential role of adjuvant regional chemotherapy after resection and cryoablation of "close" margins. For patients with unresectable disease, operative therapy also plays an important role. Multiple operative modalities hold promise in palliative treatment in the setting of clinically incurable disease. It is imperative that a large randomized trial of regional chemotherapy be performed allowing no crossover and with mortality as an endpoint. Additionally, the role of cryoablation begs systematic investigation to ensure proper use of this modality.