Surgical techniques. Aortic arch and deep hypothermic circulatory arrest: real-life suspended animation

Transposition of the left vertebral artery during endovascular stent-graft repair of the aortic arch

OBJECTIVES

The aim of this study was to present our experience with the management of isolated left vertebral artery during hybrid aortic arch repairs with thoracic endovascular aortic repair completion.

METHODS

This is a single-center, observational, cohort study. Between January 2007 and December 2018, 9 patients (4.5%) of 200 who underwent thoracic endovascular aortic repair were identified with isolated left vertebral artery. The isolated left vertebral artery was the dominant vertebral artery in 4 cases and entered the Circle of Willis to form the basilar artery in all cases. Isolated left vertebral artery transposition was performed in 2 patients during open ascending/arch repair before thoracic endovascular aortic repair completion. In 4 patients, isolated left vertebral artery transposition was performed concomitant with carotid-subclavian bypass during thoracic endovascular aortic repair completion ("zone 2" thoracic endovascular aortic repair). Primary outcomes were early (<30 days) and late survival, freedom from aortic-related mortality, and isolated left vertebral artery patency.

RESULTS

Primary technical success was achieved in all cases. Isolated left vertebral artery-related complication occurred in 1 patient (Horner syndrome). Immediate thrombosis, vagus/recurrent laryngeal nerve palsy, lymphocele, and chylothorax were never observed. Postoperative cerebrovascular accident or spinal cord injury was not observed. Median follow-up was 15 months (range, 3-72). We did not observe aortic-related mortality during the follow-up. Aortic-related intervention was never required. Both isolated left vertebral artery and carotid-subclavian bypass are still patent in all patients with no sign of anastomotic pseudoaneurysm or stenosis.

CONCLUSIONS

Although isolated left vertebral artery is not a frequent occurrence, it is not so rare. It may pose additional difficulties during hybrid aortic arch surgical repairs, but isolated left vertebral artery transposition was feasible, safe, and a durable reconstruction.

Deep hypothermic circulatory arrest: Alternative strategies for cerebral perfusion. A review article

Deep hypothermic circulatory arrest is an essential tool in the surgeon’s armamentarium. There are essentially three strategies to address cerebral ischemia during arrest periods. Early surgical case series pioneered the option of complete anoxia with deep hypothermia. Subsequent innovators introduced the concept of retrograde perfusion of the cerebral vessels through the venous system, and others have advocated the use of selective and non-selective antegrade perfusion of the cerebral arteries. Clinical studies assessing outcomes of the three approaches are compromised by small patient numbers, retrospective design and surgeon bias.

In this review, the authors will briefly discuss the conceptual basis of these strategies and the literature comparing these approaches in terms of key neurologic outcomes. The importance of this topic will emphasize the key role the perfusion community plays in establishing guidelines for best practice in circulatory arrest to go forward with education and research in this area.

Temperature dependence of cerebral blood flow for isolated regions of the brain during selective cerebral perfusion in pigs

BACKGROUND

Hypothermic circulatory arrest (HCA) and antegrade selective cerebral perfusion (ASCP) are utilized for cerebral protection during aortic surgery. However, no consensus exists regarding optimal ASCP-temperature showing a tendency toward higher values during the last years. This study investigates regional changes of cerebral blood flow (CBF) during ASCP at two temperatures.

METHODS

In this blinded study, 20 pigs (35 to 37 kg) were randomized to two groups. Animals were cooled to 10 minutes of HCA followed by 60 minutes of ASCP. Afterward the animals were perfused at 25 degrees C and 30 degrees C according to the study group. Fluorescent microspheres were injected at seven time points during the experiment to calculate total and regional CBF. Hemodynamics, cerebrovascular resistance (CVR) and cerebral metabolic rate of oxygen (CMRO(2)) were assessed. Tissue samples from the cortex, cerebellum, hippocampus, and pons were taken for microsphere count.

RESULTS

The CBF and CMRO(2) decreased significantly (p < 0.002) during cooling in both groups; it was significantly higher throughout ASCP in the 30 degrees C versus the 25 degrees C group (p = 0.0001). These findings were similar among all brain regions, certainly at different levels. The CBF increased significantly (p = 0.002) during the early period of ASCP for analyzed regions and decreased significantly (p = 0.034) below baseline after 60 minutes of ASCP, reaching critical levels in the hippocampus and neocortex. The hippocampus turned out to have the lowest CBF, while the pons showed the highest CBF. Thirty minutes and more ASCP provides less CBF compared with baseline values at both temperatures.

CONCLUSIONS

Antegrade selective cerebral perfusion improves CBF in all regions of the brain for a limited time. Our study characterizes the brain specific hierarchy of blood flow during ASCP. These dynamics are highly relevant for clinical strategies of perfusion.

Optimal temperature for selective cerebral perfusion

OBJECTIVE

Although combinations of hypothermic circulatory arrest and antegrade selective cerebral perfusion are used for cerebral protection during arch surgery, there is no consensus regarding the optimal temperature during selective cerebral perfusion. This study explored the effect of different temperatures during selective cerebral perfusion on cerebral metabolism and neurologic outcome.

METHODS

In this blinded study, 40 pigs (19-21 kg) were randomized into 4 groups after 30 minutes of hypothermic circulatory arrest at 20 degrees C. During a 60-minute interval of selective cerebral perfusion, with flow regulated to maintain a perfusion pressure of 50 mm Hg, pigs were perfused at 10 degrees C, 15 degrees C, 20 degrees C, and 25 degrees C. Fluorescent microspheres enabled calculation of cerebral blood flow during perfusion and recovery. Hemodynamics, intracranial pressure, cerebrovascular resistance, and oxygen consumption were also monitored. Behavioral scores were obtained for 7 days after surgery.

RESULTS

Cerebral blood flow decreased significantly ( P < .002) during cooling in all groups: it was significantly higher throughout selective cerebral perfusion in the 20 degrees C to 25 degrees C versus the 10 degrees C to 15 degrees C group ( P = .0001) and remained higher during recovery ( P = .0001). Oxygen consumption decreased significantly with cooling ( P = .0001), remained low during perfusion, and rebounded with rewarming but was significantly lower at 10 degrees C to 15 degrees C than at 20 degrees C to 25 degrees C throughout selective cerebral perfusion ( P = .003) and after CPB was discontinued ( P = .001). Postoperative behavioral scores were significantly better after selective cerebral perfusion at 10 degrees C to 15 degrees C than at 20 degrees C to 25 degrees C ( P = .001).

CONCLUSIONS

This study suggests that selective cerebral perfusion at 10 degrees C to 15 degrees C provides better cerebral protection than selective cerebral perfusion at 20 degrees C to 25 degrees C, even though oxygen consumption remains low for hours after selective cerebral perfusion at 10 degrees C to 15 degrees C. Prompt return of metabolism to baseline levels after hypothermic circulatory arrest/selective cerebral perfusion does not necessarily predict superior behavioral outcome.

Technical advances in total aortic arch replacement

BACKGROUND

We compared the effects of using hypothermic circulatory arrest (HCA) alone, HCA combined with selective cerebral perfusion (SCP), and use of SCP with a trifurcated graft (T) on outcome after aortic arch repair.

METHODS

One hundred fifty patients, median age 66 years (range, 27 to 85), underwent total arch replacement between 1988 and 2002; 75 were female. We retrospectively compared the results of three patient groups roughly comparable with regard to preoperative risk factors: 45 patients using HCA beginning in 1988; 67 patients using HCA/SCP beginning in 1994; and 38 patients utilizing a trifurcated arch graft in conjunction with SCP through the axillary artery (HCA/SCP/T) since 2000. The groups were well matched with regard to median age (66, 68, and 66 years), urgency (emergent 11%, 13%, 5%; urgent 24%, 9%, 18%; and elective 64%, 78%, 76%), and several other known risk factors (p = not significant).

RESULTS

An adverse outcome-hospital death or permanent stroke-occurred in 14%: in 16% with HCA, in 16% with HCA/SCP, and in 8% with HCA/SCP/T. Transient neurologic dysfunction among patients surviving without stroke was lower with HCA/SCP/T (11%) than with HCA (33%) or HCA/SCP (17%). Mean duration of HCA was 52 +/- 16 minutes with HCA alone versus 45 +/- 10 minutes with HCA/SCP and 31 +/- 7 minutes with HCA/SCP/T (p < 0.0001 for groups HCA and HCA/SCP combined versus HCA/SCP/T). Mean duration of SCP was 57 +/- 25 minutes with HCA/SCP versus 62 +/- 24 minutes with HCA/SCP/T (p = not significant). Comparison of the groups of patients who had comparable preoperative risk factors for adverse outcome showed a trend toward lower adverse outcome and transient neurologic dysfunction rates using HCA/SCP/T; a significant reduction in respiratory (p < 0.001), infectious (p = 0.015) and cardiac (p = 0.005) complications in HCA/SCP/T compared with the earlier groups; and significantly shorter durations of intensive care (p < 0.0001) and hospitalization (p = 0.004).

CONCLUSIONS

Our results suggest that HCA/SCP is superior to HCA alone for preventing cerebral injury during operations on the aortic arch. By further reducing embolic risk as well as duration of HCA, HCA/SCP/T with axillary artery cannulation may be the optimal technique for averting adverse outcomes, reducing complications, and shortening hospital stay after aortic arch repair.

Cerebral physiology and outcome after hypothermic circulatory arrest followed by selective cerebral perfusion

BACKGROUND

This study explored the impact of an interval of hypothermic circulatory arrest (HCA) preceding selective cerebral perfusion (SCP) on cerebral physiology and outcome. This protocol allows use of SCP during aortic surgery without the threat of embolization inherent in balloon catheterization of often severely atherosclerotic cerebral vessels.

METHODS

In this blinded study, 30 pigs (20 to 22 kg) were randomized after cooling to 20 degrees C. Pigs in the HCA-CPB group (n = 10) underwent 30 minutes of HCA followed by 60 minutes of total body perfusion (CPB); HCA-SCP pigs (n = 10) underwent 30 minutes of HCA followed by 60 minutes of SCP, and SCP pigs (n = 10) had 90 minutes of SCP without prior HCA. Fluorescent microspheres enabled calculation of cerebral blood flow during perfusion and recovery. Hemodynamics, intracranial pressure, cerebrovascular resistance, and cerebral oxygen consumption were also monitored. Daily behavioral scores were obtained for 7 days postoperatively.

RESULTS

In all groups, cerebral oxygen consumption fell significantly with cooling (p < 0.0001), remained low during perfusion, and rebounded promptly with rewarming; cerebral oxygen consumption was significantly (p = 0.027) greater during SCP than during HCA-CPB. Cerebral blood flow was significantly higher throughout SCP in the HCA-SCP group (p < 0.0001) than with CPB. Cerebrovascular resistance during SCP and HCA-SCP was significantly lower (p = 0.036) than during CPB. Behavioral scores were significantly better with SCP than with HCA-CPB throughout recovery, but did not differ between SCP and HCA-SCP.

CONCLUSIONS

This study suggests that a short period of HCA preceding SCP provides global cerebral protection comparable to continuous SCP, implying that in clinical practice, a short period of HCA to reduce risk of embolization will not compromise the superior cerebral protection provided by SCP.