Resection of a large, high-flow arteriovenous malformation during hypotension and hypothermia induced by a percutaneous cardiopulmonary support system. Case report

Transvenous Approach to Intracranial Arteriovenous Malformations

A compartmental conceptualization of intracranial arteriovenous malformations (AVMs) allows recognition of feeding arteries, an intervening plexiform nidus, and draining veins. AVM therapy involves eliminating the nidus, which is the source of hemorrhage, without compromising normal arterial and venous drainage of the brain. Traditional methods of AVM therapy through microsurgery and endovascular embolization involve arterial devascularization, with preservation of AVM venous drainage, until the nidus is excluded. The transvenous approach in treating vascular malformations was popularized by successful treatment models for dural arteriovenous fistulas. More recently, high-flow intracranial AVMs are being managed with transvenous endovascular approaches, although this novel technique has its challenges and perils. We review the current literature on transvenous AVM therapy and highlight its role for AVM therapy in the present day.

Cardiopulmonary bypass as an adjunct for the noncardiac surgeon

The use of cardiopulmonary bypass (CPB) in noncardiac surgical settings has been increasingly developed and has greatly benefited noncardiac surgeon. A few years after the advent of CPB as well as profound hypothermic circulatory arrest in the early years, it was employed by neurosurgeons in cerebrovascular surgery and by general thoracic surgeons in carinal tumor resection. Indications for CPB were extended and modified year after year. It has facilitated not only the surgical management by surgeons of lesions that cannot be managed safely and effectively by conventional techniques, or conventional techniques carry significant risks to the patient, but also the preservation of the viability of multiple organ procurement, the practice of isolated limb perfusion for the treatment of malignancies of the extremities, and emergent cardiopulmonary resuscitation. Owing to the complications arising from CPB and profound hypothermic circulatory arrest, such as postoperative bleeding, coagulopathy, and neurologic deficits, efforts have been made to avoid these common hazards. Thus, innovative techniques including extracorporeal membrane oxygenation, percutaneous cardiopulmonary support, venovenous bypass, normothermic CPB, and minimally invasive approaches have emerged and played an important role as alternatives of standard CPB in decreasing morbidity and mortality and improving survival.

Neuroprotection in hypothermia linked to redistribution of oxygen in brain

Hypothermia improves the outcome of acute ischemic stroke, traumatic injury, and inflammation of brain tissue. We tested the hypothesis that hypothermia reduces the energy metabolism of brain tissue to a level that is commensurate with the prevailing blood flow and hence allows adequate distribution of oxygen to the entire tissue. To determine the effect of 32 degrees C hypothermia on brain tissue, we measured the sequential changes of physiological variables by means of PET in pigs. Cerebral blood flow and oxygen consumption (cerebral metabolic rate of oxygen) declined to 50% of the baseline in 3 and 5 h, respectively, thus elevating the oxygen extraction fraction to 140% of the baseline at 3 h. The results are consistent with the claim that cooling of the brain to 32 degrees C couples both energy metabolism and blood flow to a lower rate of work of the entire tissue.

Cerebral hemodynamics and metabolism in patients with cerebral arteriovenous malformations: an evaluation using positron emission tomography scanning

OBJECT

The purpose of this study was to evaluate cerebral hemodynamic and metabolic features in patients with arteriovenous malformations (AVMs) by using positron emission tomography (PET) scanning.

METHODS

Twenty-four patients with supratentorial cerebral AVMs participated in PET studies in which 15O inhalation steady-state methods were used. The authors recorded the values of regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), the regional oxygen extraction fraction (rOEF), and the regional cerebral metabolic rate of O2 (rCMRO2) at three designated regions of interest (ROIs) in each patient. These ROIs included perilesional (ROI-p), ipsilateral remote (ROI-i), and contralateral symmetrical (ROI-c) brain regions. To identify the factors that exert a direct effect on the hemodynamics of brains affected by AVM, we also separated the lesions according to their size and flow type shown on angiograms, and grouped the patients according to the presence or absence of progressive neurological deficits. We then compared the PET parameters at different ROIs in individual patients and evaluated the mean values obtained for all 24 patients according to AVM flow type and size, and the presence or absence of progressive neurological deficits.

CONCLUSIONS

Overall, mean rCBV and rOEF values were significantly higher in ROI-p than in ROI-c (p = 0.00046 and p = 0.015, respectively). No significant differences were seen between the ROI-i and ROI-c with respect to rCBF, rCBV, and rOEF. Mean rCMRO2 values were similar in the three ROIs; however, the mean rCBF was significantly lower in the ROI-p than in the ROI-c in patients with high-flow AVMs (p = 0.019), large AVMs (p = 0.017), and progressive neurological deficits (p = 0.021). Furthermore, the mean rOEF values were significantly higher in the ROI-p than in the ROI-c in patients with high-flow AVMs (p = 0.005), large AVMs (p = 0.019), and progressive neurological deficits (p = 0.017). The PET studies revealed hemodynamic impairment characterized by decreased rCBF and increased rOEF and rCBV values in the ROI-p of patients with large, high-flow AVMs regardless of whether they exhibited progressive neurological deficits.

Resection of a large arteriovenous fistula of the brain using low-flow deep hypothermic cardiopulmonary bypass: technical case report

OBJECTIVE AND IMPORTANCE

We present the second report in the literature on the use of low-flow hypothermic cardiopulmonary bypass to aide in the surgical resection of a large intraparenchymal arteriovenous fistula.

CLINICAL PRESENTATION

The patient was a 46-year-old man who was found to have a left sylvian arteriovenous fistula with a giant varix during a workup for chronic left frontal headaches and was referred to our center for management. A cardiac workup revealed a cardiac output of 9 L per minute.

INTERVENTION

Endovascular embolization of the lesion was initially attempted without success because of the high flow within the lesion and the large diameter of the feeding arteries. We then planned combined and staged endovascular and surgical approaches to gradually eliminate the fistula. Endovascular embolization, both transarterial and transvenous, could not be performed because of the high flow in the fistula. Despite the stepwise reduction of flow during the course of several weeks via surgical exposures and arterial ligations, the fistula remained difficult to remove because of its size and the turgor of the varix. Once hypothermic low-flow circulatory bypass was used, however, decompression of the sac allowed access to the afferent vasculature.

CONCLUSION

The use of low-flow hypothermic circulatory bypass can facilitate the surgical extirpation of certain large intraparenchymal arteriovenous fistulas.

[Radiosurgery of cerebral arteriovenous malformations. Therapeutic strategies]

Modalities of management of arterio-venous malformations are discussed according to natural history and size of lesion, patient clinical status, and potential side effects of available techniques (microsurgery, radiosurgery, ambolization). Clinical cases illustrate this discussion.