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Ann Thorac Surg 2003;76:1198-1202
© 2003 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, University of Vienna, Vienna, Austria
b Department of Cardiothoracic and Vascular Anaesthesia, University of Vienna, Vienna, Austria
Accepted for publication April 8, 2003.
* Address reprint requests to Dr Fleck, Department of Cardiothoracic Surgery, Leitstelle 20A, AKH Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
e-mail: t9204604{at}hotmail.com
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Abstract |
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METHODS: Between January 1997 and January 2003, 160 consecutive patients (130 type A dissections [81%] and 30 elective atherosclerotic aneurysms [19%]) had surgical repair with DHCA for a thoracic aortic aneurysm limited to the ascending aorta. From those, 40 patients (25%) underwent DHCA alone, whereas in 13 patients (8%) antegrade cerebral perfusion and in 103 patients (64%) retrograde cerebral perfusion was used for further brain protection.
RESULTS: The overall incidence of TND was 18% (28 of 160) with a significant association between duration of circulatory arrest and the incidence of TND (13.8% in DHCA < 30 minutes versus 37.9% in DHCA > 40 minutes; p < 0.05). Furthermore the severity of TND was directly associated with the duration of circulatory arrest and age. In contrast, however, the use of retrograde cerebral perfusion had no influence on the incidence of TND, (p < 0.05). Intensive care unit stay as well as hospital stay were prolonged in the patients with TND (intensive care unit 14.3 ± 14.2 days versus 10.8 ± 13.7 days, p < 0.05; hospital stay 15.6 ± 10.1 days versus 11.4 ± 7.9 days, p < 0.05).
CONCLUSIONS: Duration of DHCA, regardless of whether retrograde cerebral perfusion was used, was the most important predictor of the incidence of transient neurologic dysfunction in patients who had replacement of the ascending thoracic aorta. The occurrence of TND leads to impaired functional recovery as well as prolonged intensive care unit and hospital stay.
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Introduction |
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However, among the leading disadvantages of this technique are hypothermia-associated coagulopathy, prolongation of the procedure through cooling and rewarming, and the time limitation imposed by circulatory arrest (CA), with 40 minutes considered the upper limit for brain protection [5]. These limitations led to the exploration of alternative methods for cerebral protection, with retrograde and antegrade cerebral perfusion being the most encouraging [6, 7].
With increasing clinical experience, we noticed that two forms of neurologic injury occur after operations that require periods of CA. The first form is permanent neurologic dysfunction, which correlates with brain computed tomography and therefore is likely to be embolic in origin, and a second form, which is a more subtle and diffuse injury manifests as transient neurologic dysfunction (TND).
Although several studies focused on long-term outcome and the risk of late reoperation, only a few studies investigated the incidence of TND on the duration of DHCA [8, 9].
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Material and methods |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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On admission 19 patients (15%) had signs of hemodynamic compromise, and 7 patients (5%) required preoperative resuscitation because of hemodynamic instability. Free blood in the pericardium was seen in 75 patients (47%). Concomitant aortic valve insufficiency was present in 22 patients (14%).
Twelve patients (9%) presented with new neurologic symptoms on admission. In only 2 patients (2%) did these signs persist after the operation.
Operative management
Details of the operative technique have been described previously [10]. The main criterion for use of CA was the presence of an intimal tear in the aortic arch, which necessitates replacement of the aortic arch.
In brief, all patients received 1 g methylprednisolone before initiation of DHCA. Topical head cooling was accomplished during DHCA. The chest was entered through a median sternotomy in all patients. Standard cardiopulmonary bypass was established femorocaval in 147 patients (92%), and the right subclavian artery was used in the remaining 13 patients (8%). Before initiating CA, the average esophageal and rectal temperatures were 12.1C and 12.3C respectively. Cooling and warming periods were on average 69 minutes and 107 minutes, respectively. Whenever retrograde cerebral perfusion was used during the period of CA, flow rates were adjusted to maintain an average central venous pressure of 20 mm Hg, which correlates with a median flow rate of 250 mL/minute. Gelatin precoated Dacron prostheses were used as grafts in all patients (Vascutek Vascular prosthesis; Sulzer Medica, Renfrewshire, Scotland).
Neurologic evaluation
Whenever a patient developed signs of transient or permanent neurologic dysfunction, a neurologist was consulted. A stroke was suspected when patients were found to have new onset of focal deficits postoperatively, which was further confirmed by computed tomographic scanning or magnetic resonance imaging of the brain. Strokes were considered transient when symptoms resolved by the time of discharge, in contrast to permanent strokes, where deficits persisted at hospital discharge.
To evaluate the severity of TND, the patients were graded according to the clinical scale developed by Ergin and associates [5] (Table 2). No imaging studies were done because TND is not associated with any structural abnormalities in the brain detectable by conventional imaging methods.
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Results |
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The DHCA time was, on average, 33 minutes (12 to 107 minutes). In 82 patients (51%) DHCA duration was less than 30 minutes, whereas in the remainder (78 patients, 49%) DHCA exceeded 30 minutes, with 36 patients (22%) having CA time greater than 40 minutes and 20 patients (12%) with DHCA time greater than 50 minutes (Fig 1).
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The proximal aortic arch was replaced in 95 patients, and in the remainder (65 patients) repair was limited to the ascending thoracic aorta. Regarding the aortic valve, replacement with a composite graft was done in 21 patients (13%), whereas in 2 patients (1%) the aortic valve was replaced separately.
Twenty-nine concomitant procedures were done in addition to aortic operation, including coronary artery bypass grafting in 20 patients (13%) and stent graft placement in the proximal descending aorta in 13 patients (8%). Stent graft placement was accomplished on average in 4 minutes during the period of CA.
Early outcome
Twenty-three patients died in the postoperative period, for an overall hospital mortality rate of 14%. Four patients (17%) died after an elective repair, versus 19 patients (83%) who were operated on urgently for type A dissection. These findings were supported by statistical analysis which revealed a significant difference between patients operated on for dissection versus patients operated on for atherosclerotic aneurysm (p < 0.001). The leading cause of death was multiorgan failure in 8 patients (35%), followed by cardiac causes in 6 patients (26%), sepsis, bleeding, and stroke, and unknown causes in 2 patients (9%) each, and respiratory insufficiency in 1 patient (4%).
Indication for operation, namely dissection or enlarging diameter, had no influence on the development of TND with a p less than 0.001 in univariate analysis.
Median intensive care unit stay for the DHCA patients was on average 11.2 ± 13.9 days. Postoperative complications other than temporary neurologic dysfunction occurred in 28 patients, consisting of respiratory insufficiency in 18 patients (11%) followed by revision for bleeding in 17 patients (11%) and renal failure due to preoperative renal insufficiency in 10 patients (6%). Results of statistical analysis are listed in Tables 3 and 4.
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The prevalence of TND was strongly correlated with the duration of DHCA. Duration of less than 30 minutes resulted in an incidence of 14%, whereas with DHCA of more than 40 minutes the incidence increased to 38%. Details are elucidated in Table 3.
A significant difference in intensive care unit stay was seen in patients who sustained a TND. Patients with TND spent on average 14.3 ± 14.3 days in the intensive care unit, in contrast to patients without TND, who stayed only 10.8 ± 13.7 days (p < 0.05). Hospital stay was also prolonged in patients who developed TND, with an average discharge after 15.6 ± 10.1 days, whereas patients without neurologic sequelae could leave the hospital after 11.4 ± 7.9 days, (p < 0.05; Table 4). Furthermore, delayed functional recovery was noted in these patients, which was predominantly caused by impaired fine motor skills and gross deficit of short-term memory function.
Severity of TND was determined according to the scale of Ergin and associates [5], which graded the severity of TND into a five categories. According to this clinical scale, 7 patients (25%) had mild symptoms (grades 1 and 2), whereas the remaining 21 patients (75%) required treatment with psychotropic drugs because of overt psychoses and agitation (grades 3 to 5). For details refer to Table 2. There was a statistically significant correlation between the severity grade of TND and the duration of DHCA (p < 0.05) and increased age (p < 0.05), as can be seen in Table 5 and Figure 2.
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Symptoms of TND subsided after 36 to 100 hours, depending on the severity of symptoms, and all patients were discharged with no residual deficit.
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Comment |
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TopAbstractIntroductionMaterial and methodsResultsCommentReferences |
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DHCA improves visualization through a bloodless surgical field and allows a more radical exclusion of the aneurysm in the aortic arch. Furthermore, through obviating the need to clamp an atherosclerotic diseased aorta, it diminishes the risk of uncontrolled release of embolic particles. However, DHCA is associated with cerebral injury and postoperative neurologic deterioration and increases the risk of transient neurologic impairment. Studies suggest the safe period of circulatory arrest at an esophageal temperature of 10°C to be 40 minutes [5].
To preserve neurologic function and to extend the duration of CA, several adjuncts, particularly antergrade or retrograde cerebral perfusion, were implemented to further enhance cerebral protection. Retrograde cerebral perfusion was implemented to abbreviate the side effects of long circulatory arrest times; flushing of embolic material, cerebral metabolic support as well as enhanced maintenance of cerebral hypothermia are the supposed mechanisms [6]. However, the benefit of retrograde cerebral perfusion remains to be proven. In our study as well as in studies by others, the use of retrograde cerebral perfusion failed to decrease the incidence of TND [11–13].
In contrast, antegrade cerebral perfusion, as described by Kazui and associates [14], was associated with improved cerebral recovery and could be used with moderate hypothermia. In a recent study by Hagl and colleagues [11], they showed reduced TND rates after implementation of antegrade cerebral perfusion, which suggested optimized blood supply to the brain with this technique. Using alternative cannulation sites, such as the subclavian artery, one can obviate the potential complication of accidental embolization during manipulation of the arch vessels. Therefore it can be assumed that the use of antegrade cerebral perfusion may be beneficial for prolonged circulatory arrest times [15].
Our overall mortality rate of 14% compares favorably with that in other similar series [7, 11]. The presence of TND had no influence on mortality; among the 31 patients who died, only 2 had symptoms of TND (p > 0.99).
The prevalence of major complications with lethal outcome is consistent with earlier reported series, with cardiac failure leading the list, followed by multiorgan failure and sepsis. The remaining causes were refractory bleeding, major stroke, and respiratory insufficiency.
Transient neurologic dysfunction as defined by Ergin and associates [5] consists of postoperative confusion, agitation, delirium, prolonged obtundation or transient parkinsonism with negative results of brain computed tomography, and resolution of symptoms at the time of discharge.
Recent data are in line with previous findings by Griepp and associates [12] showing a linear correlation between duration of CA and the occurrence of TND. Those findings are supported by the results from our study, in which the duration of DHCA emerged as the dominant factor in predicting TND. A marked increase of TND correlated with DHCA times greater than 30 minutes. Reich and colleagues [16] demonstrated that CA times more than 25 minutes and advanced age are associated with deficits in memory and fine motor skills and prolonged hospital stay.
Temporary neurologic dysfunction is almost certainly related to cerebral ischemia time. Anoxic cell injury occurs inevitably after 30 minutes of CA at 15°C. The hippocampus, which is the locus for acquisition of new information, is most vulnerable to ischemia and is particularly sensitive to anoxic injury because of its high metabolic demand [17]. In older patients more than 60 years of age, the relation is markedly pronounced [9]. In our patient cohort we found more patients with TND who were more than 60 years old (17 of 29, 59%) compared with those younger than that (12 of 29, 41%).
In our study population the occurrence of TND resulted in delayed functional recovery mainly because of impaired fine motor function and short-term memory loss, which consequently led to increased intensive care unit and hospital stay. Considering the fact that 77% of the patients with TND required treatment with psychotropic drugs because of the severity of agitation and psychoses, we consider it mandatory that increased effort should be undertaken to limit arrest duration, especially in people more than 60 years of age.
The major limitation of the study was the retrospective design, which mandates caution when interpreting the results. All effort was undertaken to avoid selection bias as well as possible confounding factors because of the different patient populations and treatment options.
We conclude that duration of DHCA was the most important predictor of postoperative transient neurologic dysfunction in patients who had replacement of the ascending thoracic aorta. However, the high prevalence of transient neurologic dysfunction necessitates further research to refine the protective methods to prevent this subtle brain injury.
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This article has been cited by other articles:
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  E. S. Krahenbuhl, F. F. Immer, M. Stalder, L. Englberger, F. S. Eckstein, and T. P. Carrel Temporary neurological dysfunction after surgery of the thoracic aorta: a predictor of poor outcome and impaired quality of life Eur. J. Cardiothorac. Surg., June 1, 2008; 33(6): 1025 - 1029. [Abstract] [Full Text] [PDF]
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 D. D. Doblar Intraoperative Transcranial Ultrasonic Monitoring for Cardiac and Vascular Surgery Seminars in Cardiothoracic and Vascular Anesthesia, June 1, 2004; 8(2): 127 - 145. [Abstract] [PDF]
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