- Email: [email protected]
S-100B Release during Carotid Endarterectomy under Local Anesthesia
S-100B Release during Carotid Endarterectomy under Local Anesthesia Marko Aleksic, Joerg Heckenkamp, Viktor Reichert, Michael Gawenda, and Jan Brunkwall, Cologne, Germany
The neuronal protein S-100B has been found to be an indicator of cellular brain damage. The aim of the study was to evaluate whether cross-clamping of the carotid artery for carotid endarterectomy (CEA) under local anesthesia is associated with the same S-100B release pattern as during general anesthesia, where an increase in S-100B concentration in the jugular vein blood of 120% has been reported. In 45 consecutive patients undergoing CEA under local anesthesia, serum S-100B samples were drawn before surgery (T1), before carotid cross-clamping (T2), before cerebral reperfusion (T3), after reperfusion but before the end of surgery (T4), and 6 hr postoperatively (T5). At T1 and T5, blood samples were drawn only from the radial artery. Intraoperatively (T2-T4), samples were collected from the internal jugular vein additionally. S-100B levels were determined using an immunoluminometric assay (LIAISONÒ Sangtec 100; Sangtec, Bromma, Sweden). In eight patients, it was necessary to insert an intraluminal shunt because of signs of cerebral ischemia. In the remaining 37 patients, median carotid clamping time was 40 min. There were no neurological complications. There were no differences in baseline S100B levels regarding gender and symptomatology. Median baseline (T1) and postoperative (T5) S-100B levels were identical (0.077 mg/L). All blood samples from the jugular vein showed significantly higher median S-100B levels than the corresponding arterial blood samples. Only slight increases of 13% and 18% were found during cross-clamping (T3) compared to the first intraoperative measurement (T2) in the venous and arterial samples, respectively, which was followed by decreases of 5% and 18%, respectively (T3-T4). S-100B release did not differ at any time point between patients who needed and patients who did not need a shunt, in either the arterial or the venous blood samples. During uncomplicated CEA under local anesthesia, there is no relevant increase of S-100B. These results are different from those reported when CEA is done under general anesthesia.
INTRODUCTION S-100 is a dimeric, calcium-binding, low-molecular weight protein. Its ß-ß monomer (S-100B) is mainly
Presented at the Ninth Annual Meeting on Surgical Research, Frankfurt, Germany, September 19-21, 2005, and at the Twenty-first Annual Meeting of the German Society of Vascular Surgery, Stuttgart, Germany, September 21-24, 2005. Division of Vascular Surgery, Department of Visceral and Vascular Surgery, University of Cologne, Cologne, Germany. Correspondence to: Marko Aleksic, MD, Division of Vascular Surgery, Department of Visceral and Vascular Surgery, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany, E-mail: Marko. [email protected] Ann Vasc Surg 2007; 21: 571-575 DOI: 10.1016/j.avsg.2007.04.002 Ó Annals of Vascular Surgery Inc. Published online: May 23, 2007
located in glial and Schwann cells,1 but S-100B has also been detected in extracerebral tissues like melanocytes, chondrocytes, adipocytes, histiocytes, and lymphatic cells.2 The serum concentration of S-100B is increased when the central nervous system is damaged as it leaks from the injured cells into the cerebrospinal fluid (CSF) and secondarily across the impaired blood-brain barrier into the systemic circulation.3,4 In head injuries, for example, S-100B serum concentrations positively correlate with the severity of the brain damage and the neurological outcome.5,6 On the contrary, normal S-100B levels could be used to exclude relevant brain damage and thereby spare unnecessary radiological examinations in minor head trauma if a quick analysis was only available.7,8 An increase of S-100B during serial 571
572 Aleksic et al.
measurements also precedes secondary complications in neurocritical care patients.9 Moreover, elevated S-100B levels are found in all kinds of cerebral damage, like cerebral infarction,10,11 hypoxia following cardiopulmonary arrest,12 and resuscitation.13 In cardiac surgery, an increased S-100B concentration is reported to be associated with perioperative neurological complications such as stroke and postoperative neuropsychological dysfunction.14,15 Carotid endarterectomy (CEA) for internal carotid artery (ICA) stenosis is related to a risk of cerebral complications as well,16 but only a small number of studies have been published so far which evaluate the perioperative pattern of S-100B release. When performed under general anesthesia, a significant increase of serum S-100B concentration was observed during carotid cross-clamping, indicating relevant global cerebral ischemia.17 Patients undergoing CEA under local anesthesia are monitored clinically, which arguably results in a more appropriate shunt insertion compared to other, less sensitive methods of neuromoitoring, like somatosensory evoked potentials (SSEP), electroencephalography, or ICA stump pressure. Therefore, it is hypothesized that the potential cerebral damage is less in awake patients, leading to lower S-100B levels. To clarify this, perioperative S-100B serum levels were measured in patients undergoing CEA under local anesthesia and compared with data given in the literature.
PATIENT POPULATION AND METHODS Forty-five consecutive patients who underwent elective CEA were enrolled in this study. The indication for surgery was a symptomatic or asymptomatic high-grade (>70%) ICA stenosis, and all operations were performed under local anesthesia. Heparin (5,000 IU) was administered intravenously before clamping of the carotid vessels. An intraluminal shunt was only inserted when the patient showed signs of cerebral ischemia like hemiplegia or unconsciousness during carotid cross-clamping. A standard endarterectomy and DacronÒ (DuPont, Wilmington, DE) patch plasty was performed in all but two patients, one of whom underwent an eversion endarterectomy and the other, an endarterectomy with primary closure. Postoperatively, the patients were referred to the intensive care unit for routine overnight monitoring. The radial artery was catheterized for hemodynamic monitoring, allowing blood samples for S-
Annals of Vascular Surgery
100B measurements to be drawn before introducing local anesthesia (T1), after exposition of the carotid artery before cross-clamping (T2), following endarterectomy before cerebral reperfusion (T3), after reperfusion before the end of surgery (T4), and 6 hr postoperatively (T5). During surgery, samples were additionally collected from the ipsilateral internal jugular vein at the time periods T2-T4. All specimens were centrifuged at 3,000 rpm at room temperature for 10 min. The supernatant was frozen and stored at 70 C until analysis. S-100B serum levels were measured using a commercially available, monoclonal two-site immunoluminometric assay (LIAISONÒ Sangtec 100; Sangtec, Bromma, Sweden). Statistical analysis was performed by SPSS software (version 11.0; SPSS, Chicago, IL). Descriptive data are presented as median and range, and the groups were compared by chi-squared test, MannWhitney U-test, or Kruskal-Wallis test to assess differences of continuous parameters between the groups when appropriate. Differences between arterial and venous blood samples and between different time points were analyzed by Wilcoxon’s test for paired nonparametric parameters. P < 0.05 was considered statistically significant.
RESULTS Patient Characteristics There were 12 female and 33 male patients with a median age of 70 years (range 57-91). Twentythree patients were neurologically asymptomatic (51%), whereas 14 had had transient ischemic attacks (TIA, 31%) and eight suffered from a stroke (18%) before surgery. All these patients were neurologically stable. No new neurological complications developed intra- or postoperatively. In eight patients (18%), a shunt insertion became necessary because of signs of cerebral ischemia which occurred immediately during test cross-clamping, and after shunting all patients neurologically returned to normal. In the remaining 37 patients who did not need a shunt, the median carotid clamping time was 40 min (range 20-65). S-100B during CEA The median S-100B levels at different time points at the two locations (radial artery or jugular vein) are summarized in Table I. There was no difference at T1 with respect to the preoperative diagnosis (asymptomatic 0.071 mg/L, range 0.042-0.321 mg/
Vol. 21, No. 5, 2007
S-100B release during CEA 573
Table I. Serum S-100B concentrations (median and range in mg/L) at different time points in the internal jugular vein and the radial artery T1
T2
T3
T4
T5
Arterial 0.077 (0.042-0.321) 0.082 (0.039-0.427) 0.097 (0.051-0.448) 0.092 (0.04-0.429) 0.077 (0.038-0.374) (radial) Venous Not done 0.121 (0.055-1.742) 0.137 (0.063-1.267) 0.112 (0.047-1.006) Not done (jugular)
L; TIA 0.102 mg/L, range 0.042-0.105 mg/L; stroke 0.093 mg/L, range 0.048-0.1 mg/L; P ¼ 0.498) or sex (male 0.076 mg/L, range 0.042-0.321 mg/L; female 0.093 mg/L, range 0.052-0.208 mg/L; P ¼ 0.424). S-100B levels were identical pre- (T1) and postoperatively (T5). Intraoperatively (T2, T3, and T4), S-100B levels were significantly higher in the jugular vein than in the radial artery blood samples (each P < 0.001). There were low but significant increases in the arterial S-100B level (P < 0.001) as well as in the venous level (P ¼ 0.001) during carotid crossclamping (from T2 to T3) of 18% and 13%, respectively. The relative decreases in S-100B concentration during reperfusion (T3 to T4) of 5% and 18%, respectively, was not significant in the arterial (P ¼ 0.979) but was significant in the venous (P ¼ 0.002) samples. There were no differences in S-100B levels at any time points between patients needing a shunt or not, in either arterial or venous blood (Table II).
DISCUSSION This study investigating S-100B release during CEA under local anesthesia revealed two main findings. First, S-100B concentrations were constantly higher in jugular venous compared to radial arterial samples. This indicates that the release came from the brain and was not a general release. Such a gradient between venous and arterial blood samples has been reported in patients with severe head injury, too.18,19 Jugular venous concentration might also better reflect momentary neuronal damage due to systemic dilution of S-100B after pulmonary circulation and rapid elimination in the kidneys.20 Baseline and postoperative S-100B concentrations did not differ in this study, which further supports the assumption of a transient release of S-100B during CEA. Second, there was only a slight S-100B increase observed during carotid cross-clamping, with lower absolute values than in patients being operated upon under general anesthesia. Jaranyi et al.17
reported an increase of 120% (0.169-0.374 mg/L) in jugular venous samples but no changes in peripheral venous blood during carotid cross-clamping. In those uncomplicated cases without the use of a shunt, the elevated levels returned to normal after declamping. In our study, however, the increase in S-100B was only 18%, suggesting less neuronal injury in awake patients. A similar pattern of release was found in arterial blood samples taken also during CEA under general anesthesia but with a fourfold increase of S-100B during carotid clamping (0.05-0.21 mg/L).21 In the present study, the corresponding overall increase during cross-clamping was only 13% in arterial samples, without any differences between shunted and nonshunted patients. Thus, the pattern of S-100B release was unchanged when the perioperative cerebral perfusion was sufficient, either primarily or after restoration within minutes by shunt placement. In a recent publication, during carotid artery stenting S-100B levels were also measured, which remained stable throughout the procedure; this was explained by the absence of carotid crossclamping and therefore uninterrupted cerebral blood flow.22 However, patients under general anesthesia needing a shunt, based on intraoperative SSEP monitoring, showed the same increase of S100B as those not needing a shunt. Consequently, the fact of carotid cross-clamping itself or temporary cerebral perfusion impairment does not simply account for these controversial observations. Rather, differences regarding the sensitivity of neuromonitoring methods with potentially subsequent delays in shunt placement have to be discussed. Another study done in patients undergoing CEA in general anesthesia, with no information on the source of the serum, presented an increase at the end of surgery and not during clamping of the carotid artery, which persisted until the first postoperative day.23 New perioperative ischemic strokes which could have contributed to these findings did not occur, though, so the reason for this different timing of S-100B release compared to the majority of studies remains obscure.
574 Aleksic et al.
Annals of Vascular Surgery
Table II. Serum S-100B concentrations (median and range in mg/L) grouped by shunt necessity Shunt
T1 T2 T2 T3 T3 T4 T4 T5
arterial arterial venous arterial venous arterial venous arterial
0.095 0.099 0.108 0.107 0.147 0.097 0.117 0.094
(0.042-0.157) (0.046-0.143) (0.072-0.158) (0.065-0.159) (0.073-0.385) (0.048-0.153) (0.053-0.184) (0.042-0.168)
There are some limitations to the present study. The small sample size naturally does not allow us to draw firm conclusions. Moreover, a randomized controlled study which ideally compares S-100B release during CEA under local and general anesthesia would provide the most reliable results. Nevertheless, it seems appropriate to discuss absolute S100B concentrations, which were measured in the present study using a commercial assay in a laboratory practising internal validation processes, in the context of the results given in the literature. It cannot be ruled out that a peak in release between two time periods could have taken place without being caught by our sampling. Serial measurements with shorter intervals would be required to answer this question. The analysis and interpretation of S-100B levels are complex, exemplified by differences in blood and CSF concentration with values <0.5 mg/L in serum and simultaneously >2 mg/L in CSF.24 S-100B has a rather high molecular weight of approximately 20,000 daltons, which prevents free diffusion through the undisturbed blood-brain barrier. However, once the blood-brain barrier is disrupted, S-100B can be detected in serum.25,26 After territorial middle cerebral artery infarctions, for example, serum S-100B concentrations increased to peak levels of 1.8 ± 3.3 mg/L within 3 days.10 A correlation between infarct volume and S-100B levels with the highest concentration (4.1 mg/L) in a large (328 mL) infarct has been described.11 Therefore, severe brain injury is well reflected by S-100B serum levels, whereas its predictive value is rather limited in carotid surgery when only clear but rare neurological complications like strokes are recognized. Other modalities to determine postoperative cerebral lesions, like computed tomographic or magnetic resonance imaging scans, which were not applied in any of the previous studies, might better correlate the value of S-100B to brain injury. In addition, the impact of extracerebral release on S-100B concentration remains unclear. In patients
No shunt
P
0.076 0.076 0.13 0.096 0.132 0.09 0.112 0.077
0.738 0.376 0.531 0.622 0.949 0.823 0.912 0.687
(0.042-0.321) (0.039-0.427) (0.055-1.742) (0.051-0.448) (0.063-1.267) (0.04-0.429) (0.047-1.006) (0.038-0.374)
who suffered from multiorgan trauma without cerebral injury, high S-100B serum levels have been attributed to injured soft tissue.27 The serum level ranged 2-10 mg/L after bone fractures, whereas it was lower after thoracic contusions without fractures (0.5-4 mg/L). In comparison, patients who died from severe head injury had similar median serum S-100B concentrations of 2.7 mg/L.5 Patients who develop stroke during CEA may also exhibit variable S-100B levels. Rasmussen et al.28 report normal and constant values (0.01 mg/L) in one patient but increasing levels with a maximum of 0.58 mg/L at 48 hr postoperatively in another patient, although both had hemiparesis and cerebral infarctions revealed by computed tomography. In summary, this study showed changes in S100B concentration in systemic and particularly jugular venous blood samples during CEA under local anesthesia. The observed increase during cross-clamping was less pronounced compared to data obtained from carotid surgery under general anesthesia. The concentration pattern did not differ between patients who needed a shunt and those who did not. However, in uncomplicated CEA under local anesthesia S-100B release is too marginal to provide further information in terms of surgery-related cerebral damage. The general clinical significance of S-100B in CEA has still to be determined since the literature is diverse in terms of study design and results.
We thank Dr. B. Krause, Laboratoriumsmedizin Dortmund for his help with and interest in performing this study.
REFERENCES 1. Tiu SC, Chan WY, Heizmann CW, Schafer BW, Shu SY, Yew DT. Differential expression of S100B and S100A6(1) in the human fetal and aged cerebral cortex. Brain Res Dev Brain Res 2000;119:159-168.
Vol. 21, No. 5, 2007
2. Haimoto H, Hosoda S, Kato K. Differential distribution of immunoreactive S100-alpha and S100-beta proteins in normal nonnervous human tissues. Lab Invest 1987;57:489-498. 3. Persson L, Hardemark HG, Gustafsson J, et al. S-100 protein and neuron-specific enolase in cerebrospinal fluid and serum: markers of cell damage in human central nervous system. Stroke 1987;18:911-918. 4. Shashoua VE, Hesse GW, Moore BW. Proteins of the brain extracellular fluid: evidence for release of S-100 protein. J Neurochem 1984;42:1536-1541. 5. Raabe A, Grolms C, Sorge O, Zimmermann M, Seifert V. Serum S-100B protein in severe head injury. Neurosurgery 1999;45:477-483. 6. Rothoerl RD, Woertgen C, Holzschuh M, Metz C, Brawanski A. S-100 serum levels after minor and major head injury. J Trauma 1998;45:765-767. 7. Ingebrigtsen T, Romner B, Marup-Jensen S, et al. The clinical value of serum S-100 protein measurements in minor head injury: a Scandinavian multicentre study. Brain Inj 2000;14:1047-1055. 8. Biberthaler P, Mussack T, Wiedemann E, et al. Evaluation of S-100b as a specific marker for neuronal damage due to minor head trauma. World J Surg 2001;25:93-97. 9. Raabe A, Kopetsch O, Woszczyk A, et al. S-100B protein as a serum marker of secondary neurological complications in neurocritical care patients. Neurol Res 2004;26:440-445. 10. Buttner T, Weyers S, Postert T, Sprengelmeyer R, Kuhn W. S-100 protein: serum marker of focal brain damage after ischemic territorial MCA infarction. Stroke 1997;28: 1961-1965. 11. Missler U, Wiesmann M, Friedrich C, Kaps M. S-100 protein and neuron-specific enolase concentrations in blood as indicators of infarction volume and prognosis in acute ischemic stroke. Stroke 1997;28:1956-1960. 12. Bottiger BW, Mobes S, Glatzer R, et al. Astroglial protein S100 is an early and sensitive marker of hypoxic brain damage and outcome after cardiac arrest in humans. Circulation 2001;103:2694-2698. 13. Mussack T, Biberthaler P, Kanz KG, Wiedemann E, GippnerSteppert C, Jochum M. S-100b, sE-selectin, and sP-selectin for evaluation of hypoxic brain damage in patients after cardiopulmonary resuscitation: pilot study. World J Surg 2001;25:539-544. 14. Ueno T, Iguro Y, Yamamoto H, Sakata R, Kakihana Y, Nakamura K. Serial measurement of serum S-100B protein as a marker of cerebral damage after cardiac surgery. Ann Thorac Surg 2003;75:1892-1898. 15. Ali MS, Harmer M, Vaughan R. Serum S100 protein as a marker of cerebral damage during cardiac surgery. Br J Anaesth 2000;85:287-298.
S-100B release during CEA 575
16. Bond R, Rerkasem K, Rothwell PM. Systematic review of the risks of carotid endarterectomy in relation to the clinical indication for and timing of surgery. Stroke 2003;34: 2290-2301. 17. Jaranyi Z, Szekely M, Bobek I, Galfy I, Geller L, Selmeci L. Impairment of blood-brain barrier integrity during carotid surgery as assessed by serum S-100B protein concentrations. Clin Chem Lab Med 2003;41:1320-1322. 18. Raabe A, Menon DK, Gupta S, Czosnyka M, Pickard JD. Jugular venous and arterial concentrations of serum S100B protein in patients with severe head injury: a pilot study. J Neurol Neurosurg Psychiatry 1998;65:930-932. 19. McKeating EG, Andrews PJ, Mascia L. Relationship of neuron specific enolase and protein S-100 concentrations in systemic and jugular venous serum to injury severity and outcome after traumatic brain injury. Acta Neurochir Suppl 1998;71:117-119. 20. Usui A, Kato K, Abe T, Murase M, Tanaka M, Takeuchi E. S-100ao protein in blood and urine during open-heart surgery. Clin Chem 1989;35:1942-1944. 21. Mussack T, Biberthaler P, Geisenberger T, et al. Assessment of early brain damage in carotid endarterectomy: evaluation of S-100B serum levels and somatosensory evoked potentials in a pilot study. World J Surg 2002;26:1251-1255. 22. Mussack T, Hauser C, Klauss V, et al. Serum S-100B protein levels during and after successful carotid artery stenting or carotid endarterectomy. J Endovasc Ther 2006;13:39-46. 23. Godet G, Watremez C, Beaudeux JL, Meersschaert K, Koskas F, Coriat P. S-100beta protein levels do not correlate with stroke in patients undergoing carotid endarterectomy under general anesthesia. J Cardiothorac Vasc Anesth 2001;15:25-28. 24. Gao F, Harris DN, Sapsed-Byrne S, Standfield NJ. Nerve tissue protein S-100 and neurone-specific enolase concentrations in cerebrospinal fluid and blood during carotid endarterectomy. Anaesthesia 2000;55:764-769. 25. Kapural M, Krizanac-Bengez L, Barnett G, et al. Serum S100beta as a possible marker of blood-brain barrier disruption. Brain Res 2002;940:102-104. 26. Kanner AA, Marchi N, Fazio V, et al. Serum S100beta: a noninvasive marker of blood-brain barrier function and brain lesions. Cancer 2003;97:2806-2813. 27. Anderson RE, Hansson LO, Nilsson O, Dijlai-Merzoug R, Settergren G. High serum S100B levels for trauma patients without head injuries. Neurosurgery 2001;48:1255-1260. 28. Rasmussen LS, Christiansen M, Johnsen J, Gronholdt ML, Moller JT. Subtle brain damage cannot be detected by measuring neuron-specific enolase and S-100beta protein after carotid endarterectomy. J Cardiothorac Vasc Anesth 2000;14:166-170.
The neuronal protein S-100B has been found to be an indicator of cellular brain damage. The aim of the study was to evaluate whether cross-clamping of the carotid artery for carotid endarterectomy (CEA) under local anesthesia is associated with the same S-100B release pattern as during general anesthesia, where an increase in S-100B concentration in the jugular vein blood of 120% has been reported. In 45 consecutive patients undergoing CEA under local anesthesia, serum S-100B samples were drawn before surgery (T1), before carotid cross-clamping (T2), before cerebral reperfusion (T3), after reperfusion but before the end of surgery (T4), and 6 hr postoperatively (T5). At T1 and T5, blood samples were drawn only from the radial artery. Intraoperatively (T2-T4), samples were collected from the internal jugular vein additionally. S-100B levels were determined using an immunoluminometric assay (LIAISONÒ Sangtec 100; Sangtec, Bromma, Sweden). In eight patients, it was necessary to insert an intraluminal shunt because of signs of cerebral ischemia. In the remaining 37 patients, median carotid clamping time was 40 min. There were no neurological complications. There were no differences in baseline S100B levels regarding gender and symptomatology. Median baseline (T1) and postoperative (T5) S-100B levels were identical (0.077 mg/L). All blood samples from the jugular vein showed significantly higher median S-100B levels than the corresponding arterial blood samples. Only slight increases of 13% and 18% were found during cross-clamping (T3) compared to the first intraoperative measurement (T2) in the venous and arterial samples, respectively, which was followed by decreases of 5% and 18%, respectively (T3-T4). S-100B release did not differ at any time point between patients who needed and patients who did not need a shunt, in either the arterial or the venous blood samples. During uncomplicated CEA under local anesthesia, there is no relevant increase of S-100B. These results are different from those reported when CEA is done under general anesthesia.
INTRODUCTION S-100 is a dimeric, calcium-binding, low-molecular weight protein. Its ß-ß monomer (S-100B) is mainly
Presented at the Ninth Annual Meeting on Surgical Research, Frankfurt, Germany, September 19-21, 2005, and at the Twenty-first Annual Meeting of the German Society of Vascular Surgery, Stuttgart, Germany, September 21-24, 2005. Division of Vascular Surgery, Department of Visceral and Vascular Surgery, University of Cologne, Cologne, Germany. Correspondence to: Marko Aleksic, MD, Division of Vascular Surgery, Department of Visceral and Vascular Surgery, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany, E-mail: Marko. [email protected] Ann Vasc Surg 2007; 21: 571-575 DOI: 10.1016/j.avsg.2007.04.002 Ó Annals of Vascular Surgery Inc. Published online: May 23, 2007
located in glial and Schwann cells,1 but S-100B has also been detected in extracerebral tissues like melanocytes, chondrocytes, adipocytes, histiocytes, and lymphatic cells.2 The serum concentration of S-100B is increased when the central nervous system is damaged as it leaks from the injured cells into the cerebrospinal fluid (CSF) and secondarily across the impaired blood-brain barrier into the systemic circulation.3,4 In head injuries, for example, S-100B serum concentrations positively correlate with the severity of the brain damage and the neurological outcome.5,6 On the contrary, normal S-100B levels could be used to exclude relevant brain damage and thereby spare unnecessary radiological examinations in minor head trauma if a quick analysis was only available.7,8 An increase of S-100B during serial 571
572 Aleksic et al.
measurements also precedes secondary complications in neurocritical care patients.9 Moreover, elevated S-100B levels are found in all kinds of cerebral damage, like cerebral infarction,10,11 hypoxia following cardiopulmonary arrest,12 and resuscitation.13 In cardiac surgery, an increased S-100B concentration is reported to be associated with perioperative neurological complications such as stroke and postoperative neuropsychological dysfunction.14,15 Carotid endarterectomy (CEA) for internal carotid artery (ICA) stenosis is related to a risk of cerebral complications as well,16 but only a small number of studies have been published so far which evaluate the perioperative pattern of S-100B release. When performed under general anesthesia, a significant increase of serum S-100B concentration was observed during carotid cross-clamping, indicating relevant global cerebral ischemia.17 Patients undergoing CEA under local anesthesia are monitored clinically, which arguably results in a more appropriate shunt insertion compared to other, less sensitive methods of neuromoitoring, like somatosensory evoked potentials (SSEP), electroencephalography, or ICA stump pressure. Therefore, it is hypothesized that the potential cerebral damage is less in awake patients, leading to lower S-100B levels. To clarify this, perioperative S-100B serum levels were measured in patients undergoing CEA under local anesthesia and compared with data given in the literature.
PATIENT POPULATION AND METHODS Forty-five consecutive patients who underwent elective CEA were enrolled in this study. The indication for surgery was a symptomatic or asymptomatic high-grade (>70%) ICA stenosis, and all operations were performed under local anesthesia. Heparin (5,000 IU) was administered intravenously before clamping of the carotid vessels. An intraluminal shunt was only inserted when the patient showed signs of cerebral ischemia like hemiplegia or unconsciousness during carotid cross-clamping. A standard endarterectomy and DacronÒ (DuPont, Wilmington, DE) patch plasty was performed in all but two patients, one of whom underwent an eversion endarterectomy and the other, an endarterectomy with primary closure. Postoperatively, the patients were referred to the intensive care unit for routine overnight monitoring. The radial artery was catheterized for hemodynamic monitoring, allowing blood samples for S-
Annals of Vascular Surgery
100B measurements to be drawn before introducing local anesthesia (T1), after exposition of the carotid artery before cross-clamping (T2), following endarterectomy before cerebral reperfusion (T3), after reperfusion before the end of surgery (T4), and 6 hr postoperatively (T5). During surgery, samples were additionally collected from the ipsilateral internal jugular vein at the time periods T2-T4. All specimens were centrifuged at 3,000 rpm at room temperature for 10 min. The supernatant was frozen and stored at 70 C until analysis. S-100B serum levels were measured using a commercially available, monoclonal two-site immunoluminometric assay (LIAISONÒ Sangtec 100; Sangtec, Bromma, Sweden). Statistical analysis was performed by SPSS software (version 11.0; SPSS, Chicago, IL). Descriptive data are presented as median and range, and the groups were compared by chi-squared test, MannWhitney U-test, or Kruskal-Wallis test to assess differences of continuous parameters between the groups when appropriate. Differences between arterial and venous blood samples and between different time points were analyzed by Wilcoxon’s test for paired nonparametric parameters. P < 0.05 was considered statistically significant.
RESULTS Patient Characteristics There were 12 female and 33 male patients with a median age of 70 years (range 57-91). Twentythree patients were neurologically asymptomatic (51%), whereas 14 had had transient ischemic attacks (TIA, 31%) and eight suffered from a stroke (18%) before surgery. All these patients were neurologically stable. No new neurological complications developed intra- or postoperatively. In eight patients (18%), a shunt insertion became necessary because of signs of cerebral ischemia which occurred immediately during test cross-clamping, and after shunting all patients neurologically returned to normal. In the remaining 37 patients who did not need a shunt, the median carotid clamping time was 40 min (range 20-65). S-100B during CEA The median S-100B levels at different time points at the two locations (radial artery or jugular vein) are summarized in Table I. There was no difference at T1 with respect to the preoperative diagnosis (asymptomatic 0.071 mg/L, range 0.042-0.321 mg/
Vol. 21, No. 5, 2007
S-100B release during CEA 573
Table I. Serum S-100B concentrations (median and range in mg/L) at different time points in the internal jugular vein and the radial artery T1
T2
T3
T4
T5
Arterial 0.077 (0.042-0.321) 0.082 (0.039-0.427) 0.097 (0.051-0.448) 0.092 (0.04-0.429) 0.077 (0.038-0.374) (radial) Venous Not done 0.121 (0.055-1.742) 0.137 (0.063-1.267) 0.112 (0.047-1.006) Not done (jugular)
L; TIA 0.102 mg/L, range 0.042-0.105 mg/L; stroke 0.093 mg/L, range 0.048-0.1 mg/L; P ¼ 0.498) or sex (male 0.076 mg/L, range 0.042-0.321 mg/L; female 0.093 mg/L, range 0.052-0.208 mg/L; P ¼ 0.424). S-100B levels were identical pre- (T1) and postoperatively (T5). Intraoperatively (T2, T3, and T4), S-100B levels were significantly higher in the jugular vein than in the radial artery blood samples (each P < 0.001). There were low but significant increases in the arterial S-100B level (P < 0.001) as well as in the venous level (P ¼ 0.001) during carotid crossclamping (from T2 to T3) of 18% and 13%, respectively. The relative decreases in S-100B concentration during reperfusion (T3 to T4) of 5% and 18%, respectively, was not significant in the arterial (P ¼ 0.979) but was significant in the venous (P ¼ 0.002) samples. There were no differences in S-100B levels at any time points between patients needing a shunt or not, in either arterial or venous blood (Table II).
DISCUSSION This study investigating S-100B release during CEA under local anesthesia revealed two main findings. First, S-100B concentrations were constantly higher in jugular venous compared to radial arterial samples. This indicates that the release came from the brain and was not a general release. Such a gradient between venous and arterial blood samples has been reported in patients with severe head injury, too.18,19 Jugular venous concentration might also better reflect momentary neuronal damage due to systemic dilution of S-100B after pulmonary circulation and rapid elimination in the kidneys.20 Baseline and postoperative S-100B concentrations did not differ in this study, which further supports the assumption of a transient release of S-100B during CEA. Second, there was only a slight S-100B increase observed during carotid cross-clamping, with lower absolute values than in patients being operated upon under general anesthesia. Jaranyi et al.17
reported an increase of 120% (0.169-0.374 mg/L) in jugular venous samples but no changes in peripheral venous blood during carotid cross-clamping. In those uncomplicated cases without the use of a shunt, the elevated levels returned to normal after declamping. In our study, however, the increase in S-100B was only 18%, suggesting less neuronal injury in awake patients. A similar pattern of release was found in arterial blood samples taken also during CEA under general anesthesia but with a fourfold increase of S-100B during carotid clamping (0.05-0.21 mg/L).21 In the present study, the corresponding overall increase during cross-clamping was only 13% in arterial samples, without any differences between shunted and nonshunted patients. Thus, the pattern of S-100B release was unchanged when the perioperative cerebral perfusion was sufficient, either primarily or after restoration within minutes by shunt placement. In a recent publication, during carotid artery stenting S-100B levels were also measured, which remained stable throughout the procedure; this was explained by the absence of carotid crossclamping and therefore uninterrupted cerebral blood flow.22 However, patients under general anesthesia needing a shunt, based on intraoperative SSEP monitoring, showed the same increase of S100B as those not needing a shunt. Consequently, the fact of carotid cross-clamping itself or temporary cerebral perfusion impairment does not simply account for these controversial observations. Rather, differences regarding the sensitivity of neuromonitoring methods with potentially subsequent delays in shunt placement have to be discussed. Another study done in patients undergoing CEA in general anesthesia, with no information on the source of the serum, presented an increase at the end of surgery and not during clamping of the carotid artery, which persisted until the first postoperative day.23 New perioperative ischemic strokes which could have contributed to these findings did not occur, though, so the reason for this different timing of S-100B release compared to the majority of studies remains obscure.
574 Aleksic et al.
Annals of Vascular Surgery
Table II. Serum S-100B concentrations (median and range in mg/L) grouped by shunt necessity Shunt
T1 T2 T2 T3 T3 T4 T4 T5
arterial arterial venous arterial venous arterial venous arterial
0.095 0.099 0.108 0.107 0.147 0.097 0.117 0.094
(0.042-0.157) (0.046-0.143) (0.072-0.158) (0.065-0.159) (0.073-0.385) (0.048-0.153) (0.053-0.184) (0.042-0.168)
There are some limitations to the present study. The small sample size naturally does not allow us to draw firm conclusions. Moreover, a randomized controlled study which ideally compares S-100B release during CEA under local and general anesthesia would provide the most reliable results. Nevertheless, it seems appropriate to discuss absolute S100B concentrations, which were measured in the present study using a commercial assay in a laboratory practising internal validation processes, in the context of the results given in the literature. It cannot be ruled out that a peak in release between two time periods could have taken place without being caught by our sampling. Serial measurements with shorter intervals would be required to answer this question. The analysis and interpretation of S-100B levels are complex, exemplified by differences in blood and CSF concentration with values <0.5 mg/L in serum and simultaneously >2 mg/L in CSF.24 S-100B has a rather high molecular weight of approximately 20,000 daltons, which prevents free diffusion through the undisturbed blood-brain barrier. However, once the blood-brain barrier is disrupted, S-100B can be detected in serum.25,26 After territorial middle cerebral artery infarctions, for example, serum S-100B concentrations increased to peak levels of 1.8 ± 3.3 mg/L within 3 days.10 A correlation between infarct volume and S-100B levels with the highest concentration (4.1 mg/L) in a large (328 mL) infarct has been described.11 Therefore, severe brain injury is well reflected by S-100B serum levels, whereas its predictive value is rather limited in carotid surgery when only clear but rare neurological complications like strokes are recognized. Other modalities to determine postoperative cerebral lesions, like computed tomographic or magnetic resonance imaging scans, which were not applied in any of the previous studies, might better correlate the value of S-100B to brain injury. In addition, the impact of extracerebral release on S-100B concentration remains unclear. In patients
No shunt
P
0.076 0.076 0.13 0.096 0.132 0.09 0.112 0.077
0.738 0.376 0.531 0.622 0.949 0.823 0.912 0.687
(0.042-0.321) (0.039-0.427) (0.055-1.742) (0.051-0.448) (0.063-1.267) (0.04-0.429) (0.047-1.006) (0.038-0.374)
who suffered from multiorgan trauma without cerebral injury, high S-100B serum levels have been attributed to injured soft tissue.27 The serum level ranged 2-10 mg/L after bone fractures, whereas it was lower after thoracic contusions without fractures (0.5-4 mg/L). In comparison, patients who died from severe head injury had similar median serum S-100B concentrations of 2.7 mg/L.5 Patients who develop stroke during CEA may also exhibit variable S-100B levels. Rasmussen et al.28 report normal and constant values (0.01 mg/L) in one patient but increasing levels with a maximum of 0.58 mg/L at 48 hr postoperatively in another patient, although both had hemiparesis and cerebral infarctions revealed by computed tomography. In summary, this study showed changes in S100B concentration in systemic and particularly jugular venous blood samples during CEA under local anesthesia. The observed increase during cross-clamping was less pronounced compared to data obtained from carotid surgery under general anesthesia. The concentration pattern did not differ between patients who needed a shunt and those who did not. However, in uncomplicated CEA under local anesthesia S-100B release is too marginal to provide further information in terms of surgery-related cerebral damage. The general clinical significance of S-100B in CEA has still to be determined since the literature is diverse in terms of study design and results.
We thank Dr. B. Krause, Laboratoriumsmedizin Dortmund for his help with and interest in performing this study.
REFERENCES 1. Tiu SC, Chan WY, Heizmann CW, Schafer BW, Shu SY, Yew DT. Differential expression of S100B and S100A6(1) in the human fetal and aged cerebral cortex. Brain Res Dev Brain Res 2000;119:159-168.
Vol. 21, No. 5, 2007
2. Haimoto H, Hosoda S, Kato K. Differential distribution of immunoreactive S100-alpha and S100-beta proteins in normal nonnervous human tissues. Lab Invest 1987;57:489-498. 3. Persson L, Hardemark HG, Gustafsson J, et al. S-100 protein and neuron-specific enolase in cerebrospinal fluid and serum: markers of cell damage in human central nervous system. Stroke 1987;18:911-918. 4. Shashoua VE, Hesse GW, Moore BW. Proteins of the brain extracellular fluid: evidence for release of S-100 protein. J Neurochem 1984;42:1536-1541. 5. Raabe A, Grolms C, Sorge O, Zimmermann M, Seifert V. Serum S-100B protein in severe head injury. Neurosurgery 1999;45:477-483. 6. Rothoerl RD, Woertgen C, Holzschuh M, Metz C, Brawanski A. S-100 serum levels after minor and major head injury. J Trauma 1998;45:765-767. 7. Ingebrigtsen T, Romner B, Marup-Jensen S, et al. The clinical value of serum S-100 protein measurements in minor head injury: a Scandinavian multicentre study. Brain Inj 2000;14:1047-1055. 8. Biberthaler P, Mussack T, Wiedemann E, et al. Evaluation of S-100b as a specific marker for neuronal damage due to minor head trauma. World J Surg 2001;25:93-97. 9. Raabe A, Kopetsch O, Woszczyk A, et al. S-100B protein as a serum marker of secondary neurological complications in neurocritical care patients. Neurol Res 2004;26:440-445. 10. Buttner T, Weyers S, Postert T, Sprengelmeyer R, Kuhn W. S-100 protein: serum marker of focal brain damage after ischemic territorial MCA infarction. Stroke 1997;28: 1961-1965. 11. Missler U, Wiesmann M, Friedrich C, Kaps M. S-100 protein and neuron-specific enolase concentrations in blood as indicators of infarction volume and prognosis in acute ischemic stroke. Stroke 1997;28:1956-1960. 12. Bottiger BW, Mobes S, Glatzer R, et al. Astroglial protein S100 is an early and sensitive marker of hypoxic brain damage and outcome after cardiac arrest in humans. Circulation 2001;103:2694-2698. 13. Mussack T, Biberthaler P, Kanz KG, Wiedemann E, GippnerSteppert C, Jochum M. S-100b, sE-selectin, and sP-selectin for evaluation of hypoxic brain damage in patients after cardiopulmonary resuscitation: pilot study. World J Surg 2001;25:539-544. 14. Ueno T, Iguro Y, Yamamoto H, Sakata R, Kakihana Y, Nakamura K. Serial measurement of serum S-100B protein as a marker of cerebral damage after cardiac surgery. Ann Thorac Surg 2003;75:1892-1898. 15. Ali MS, Harmer M, Vaughan R. Serum S100 protein as a marker of cerebral damage during cardiac surgery. Br J Anaesth 2000;85:287-298.
S-100B release during CEA 575
16. Bond R, Rerkasem K, Rothwell PM. Systematic review of the risks of carotid endarterectomy in relation to the clinical indication for and timing of surgery. Stroke 2003;34: 2290-2301. 17. Jaranyi Z, Szekely M, Bobek I, Galfy I, Geller L, Selmeci L. Impairment of blood-brain barrier integrity during carotid surgery as assessed by serum S-100B protein concentrations. Clin Chem Lab Med 2003;41:1320-1322. 18. Raabe A, Menon DK, Gupta S, Czosnyka M, Pickard JD. Jugular venous and arterial concentrations of serum S100B protein in patients with severe head injury: a pilot study. J Neurol Neurosurg Psychiatry 1998;65:930-932. 19. McKeating EG, Andrews PJ, Mascia L. Relationship of neuron specific enolase and protein S-100 concentrations in systemic and jugular venous serum to injury severity and outcome after traumatic brain injury. Acta Neurochir Suppl 1998;71:117-119. 20. Usui A, Kato K, Abe T, Murase M, Tanaka M, Takeuchi E. S-100ao protein in blood and urine during open-heart surgery. Clin Chem 1989;35:1942-1944. 21. Mussack T, Biberthaler P, Geisenberger T, et al. Assessment of early brain damage in carotid endarterectomy: evaluation of S-100B serum levels and somatosensory evoked potentials in a pilot study. World J Surg 2002;26:1251-1255. 22. Mussack T, Hauser C, Klauss V, et al. Serum S-100B protein levels during and after successful carotid artery stenting or carotid endarterectomy. J Endovasc Ther 2006;13:39-46. 23. Godet G, Watremez C, Beaudeux JL, Meersschaert K, Koskas F, Coriat P. S-100beta protein levels do not correlate with stroke in patients undergoing carotid endarterectomy under general anesthesia. J Cardiothorac Vasc Anesth 2001;15:25-28. 24. Gao F, Harris DN, Sapsed-Byrne S, Standfield NJ. Nerve tissue protein S-100 and neurone-specific enolase concentrations in cerebrospinal fluid and blood during carotid endarterectomy. Anaesthesia 2000;55:764-769. 25. Kapural M, Krizanac-Bengez L, Barnett G, et al. Serum S100beta as a possible marker of blood-brain barrier disruption. Brain Res 2002;940:102-104. 26. Kanner AA, Marchi N, Fazio V, et al. Serum S100beta: a noninvasive marker of blood-brain barrier function and brain lesions. Cancer 2003;97:2806-2813. 27. Anderson RE, Hansson LO, Nilsson O, Dijlai-Merzoug R, Settergren G. High serum S100B levels for trauma patients without head injuries. Neurosurgery 2001;48:1255-1260. 28. Rasmussen LS, Christiansen M, Johnsen J, Gronholdt ML, Moller JT. Subtle brain damage cannot be detected by measuring neuron-specific enolase and S-100beta protein after carotid endarterectomy. J Cardiothorac Vasc Anesth 2000;14:166-170.