Assessment of cerebral oxygen balance during deep hypothermic circulatory arrest by continuous jugular bulb venous saturation and near-infrared spectroscopy

OBJECTIVE: The purpose of this study was to compare jugular venous bulb saturation (SjvO(2)) and regional cerebral oximetry (rSO(2)) by near-infrared spectroscopy (NIRS) during procedures with deep hypothermic circulatory arrest (DHCA). DESIGN: Prospective observational study. SETTING: Academic hospital. PARTICIPANTS: Patients undergoing aortic reconstructive surgery with DHCA from July 2001 to January 2005. INTERVENTION: The authors examined cerebral oxygenation by continuous NIRS monitoring and by blood gas analysis of intermittently sampled jugular bulb blood (SjvO(2)). Data were obtained during various stages of the procedure in 29 patients. NIRS measurements were compared with SjvO(2). MEASUREMENTS AND MAIN RESULTS: NIRS and SjvO(2) trends were similar. Overall, cerebral venous oxygen saturation obtained from NIRS was lower compared with SjvO(2) (p < 0.05), especially during periods of low temperature. The mean correlation between NIRS and SjvO(2) was 0.363, and the individual correlations varied from -0.11 to 0.91. The low mean correlation was because of a high degree of variability in the NIRS data between patients. CONCLUSION: It was concluded that NIRS does not closely correlate with SjvO(2) in this patient population. Cerebral oximetry measured by NIRS could not replace jugular bulb saturation as an intraoperative marker of adequate metabolic suppression.     

Comparative effects of propofol versus fentanyl on cerebral oxygenation state during normothermic cardiopulmonary bypass and postoperative cognitive dysfunction

BACKGROUND: The purpose of this study was to examine the comparative effects of propofol and fentanyl on cerebral oxygenation during normothermic cardiopulmonary bypass and postoperative cognitive dysfunction. METHODS: One hundred eighty patients scheduled for elective coronary artery bypass grafting were randomly divided into two groups: propofol group (n = 90) and fentanyl group (n = 90). After induction of anesthesia, a fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to monitor jugular venous oxygen hemoglobin saturation continuously. Hemodynamic measurements and arterial and jugular venous blood gases were measured at seven time points. All patients underwent a battery of neurologic and neuropsychological tests on the day before the operation and at 6 months after the operation. RESULTS: Cerebral desaturation (defined as a jugular venous oxygen hemoglobin saturation value less than 50%) during cardiopulmonary bypass was more frequent in the fentanyl group than in the propofol group. Cerebral desaturation time (duration when jugular venous oxygen hemoglobin saturation was less than 50%) and the ratio of cerebral desaturation time to total cardiopulmonary bypass time in the fentanyl group differed significantly from those in the propofol group (fentanyl group: 27 +/- 14 minutes, 20% +/- 9%; propofol group: 18 +/- 11 minutes, 14% +/- 7%, respectively, p < 0.05). There was no significant difference in postoperative cognitive dysfunction at 6 months after operation between the two groups (propofol group: 5 of 77, 6%; fentanyl group: 5 of 75, 7%). CONCLUSIONS: Propofol preserved cerebral oxygenation state estimated by jugular venous oxygenation during cardiopulmonary bypass compared with the fentanyl group. However, propofol did not affect postoperative cognitive dysfunction.     

Use of Cerebral Oximetry to Monitor Brain Oxygenation Reserves for Skull Base Surgery

We used cerebral oximetry based on near-infrared re-emittance spectroscopy for noninvasive evaluation of the cerebral regional oxygen saturation (rSO₂) to preoperatively assess patients with skull base tumors and giant arterial aneurysms, for whom possible occlusion or partial resection of the internal carotid artery was considered. Monitoring cerebral oxygen saturation was performed during both endovascular (balloon) and open surgical test occlusions of the internal carotid artery. The presence (or absence) of changes in the cerebral oxygen saturation served as a criterion of the patient's tolerance to permanent occlusion of the internal carotid artery. In all cases the curves of saturation accurately corresponded to the clinical condition of the patients, primarily to the developing of neurological signs. Cerebral oximetry was an extremely informative and reliable technique for fast, easy, and noninvasive detection of changes in brain blood circulation. Generally, cerebral oximetry serves as a valuable adjunct in detection of brain tolerance to the occlusion of major arterial vessels and in monitoring the condition of the brain in regard to its oxygenation and perfusion.     

Monitoring of intracranial pressure and cerebral hemodynamics by transjugular dural sinus catheterization

Cerebral venous sampling may be useful in the evaluation of cerebral damage. A catheter was successfully inserted 18 cm deep from the right internal jugular vein into the transverse sinus in a 38 year old man with B-mode ultrasound guidance to measure pressure and sample blood. Transverse sinus venous oxygen saturation (StvO₂) was lower than normal ranges (55% - 75%) for jugular venous oxygen saturation (SjvO₂). At the time spontaneous cardiac rhythm was restored, transverse sinus pressure increased briefly to 26 mmHg [more than 15 mmHg higher than normal intracranial pressure (ICP)]. This case suggests that catheterization of the dural sinus may be accomplished with B-mode ultrasound guidance and that the catheter can be used to monitor ICP and cerebral hemodynamics.     

Time course of changes in jugular venous oxygen saturation during hypothermic or normothermic cardiopulmonary bypass in patients with diabetes mellitus

BACKGROUND: Preexisting diabetic mellitus is a risk factor determining postoperative neurological disorders. The present study assesses the effects of normothermic and hypothermic cardiopulmonary bypass (CPB) on jugular venous oxygen saturation (SjvO2)in patients with preexisting diabetic mellitus. METHODS: Sixteen diabetic patients who underwent elective coronary artery bypass grafting surgery were randomly divided into two groups: Group DN (n=8, diabetic patients) underwent normothermic CPB (>35 degrees C), and group DH (n=8, diabetic patients) underwent hypothermic CPB (32 degrees C). Controls were 16 age-matched non-diabetic patients (normothemic group, CN: n=8; hypothemic group, CH: n=8). A 4.0 F fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to continuously monitor SjvO2 values. Hemodynamic parameters and arterial and jugular venous blood gases were measured seven times. RESULTS: Cerebral desaturation, which was defined as SjvO2 values below 50%, was observed during normothermic CPB in diabetic patients (at the onset of CPB: 46+/-3%, at 20 min after onset of CPB: 49+/-3%, means+/-SD, respectively). No cerebral desaturation occurred in diabetic and control patients during hypothermic CPB. CONCLUSIONS: Patients with preexisting diabetes mellitus experienced cerebral desaturation during normothermic CPB.     

Erweitertes zerebrales Monitoring mit transkranieller Doppler-Sonographie und zerebrovenöser Oxymetrie während einer Reanimation

This case report describes cerebral monitoring of intracranial haemodynamics using transcranial Doppler sonography (TCD) and jugular bulb oxygen saturation (SjO₂) by fiberoptic jugular bulb oximetry during cardiac arrest following cardiac surgery involving cardiopulmonary bypass (CPB). CPB for aortic valve replacement and coronary artery bypass grafting was performed in a 63-year-old patient previously operated upon for heart disease. Mean blood flow velocity was measured in the middle cerebral artery using a bidirectional 2?MHz TCD system. SjO₂ was measured using a fiberoptic thermodilution catheter placed in the right jugular bulb via the right internal jugular vein under radiographic control. At the end of the operation, low cardiac output syndrome and cardiac arrest occurred, which required reopening of the thorax and cardiopulmonary resuscitation (CPR) until CPB could be resumed. Following extrathoracic cardiac resuscitation, systolic “spikes”, loss of the diastolic flow profile, and no increase in SjO₂ were recorded by the monitors, indicating cerebral circulatory arrest. However, a normal flow profile with increasing diastolic portions and an increase in SjO₂ to 52% were seen following optimisation of the open thorax cardiac resuscitation. This monitoring may be able to give information to optimise therapy during CPR to avoid ischaemic cerebral injury.     

Ist die hirnvenöse Sauerstoffsättigung ein Maß für die zerebrale Durchblutung?

The arteriovenous oxygen content difference (avDO₂) of the brain is dependent on O₂ consumption (CMRO₂) and cerebral blood flow (CBF). With unchanging arterial O₂ content, avDO₂ is inversely related to cerebral venous O₂ saturation (SO₂). Measurement of SO₂ in the jugular bulb not only provides information about the O₂ balance of the brain, but may give an important estimation of CBF if a clinically useful correlation is proven. The aim of the present study was to verify this aspect. Methods. Sixty-two male patients undergoing coronary revascularisation were investigated. The study was approved by the local Ethical Committee and each patient gave written informed consent on the preoperative day. At four points during the perioperative course arterial and cerebral venous SO₂ and CBF were measured. Cerebral venous blood was sampled from a catheter in the superior bulb of the right internal jugular vein. CBF was measured using the argon wash-in technique. All sampled data were pooled and evaluated. Results. As expected from theory, cerebral venous SO₂ and avDO₂ showed a close linear relationship (r=?0.892). However, only a weak hyperbolic relationship was found between cerebral venous SO₂ and CBF. In addition, no direct correlation between CMRO₂ and SO₂ in the jugular bulb could be demonstrated. Conclusions. In this clinical study, a close relationship between cerebral venous SO₂ and CBF was not found. This was primarily due to the high variability of cerebral O₂ uptake. Changes in cerebral venous SO₂ may therefore not be used as an estimate of perioperative changes in CBF.     

Arterial and venous contributions to near-infrared cerebral oximetry

BACKGROUND: Cerebral oximetry is a noninvasive bedside technology using near-infrared light to monitor cerebral oxygen saturation (Sco2) in an uncertain mixture of arteries, capillaries, and veins. The present study used frequency domain near-infrared spectroscopy to determine the ratio of arterial and venous blood monitored by cerebral oximetry during normoxia, hypoxia, and hypocapnia. METHODS: Twenty anesthetized children aged < 8 yr with congenital heart disease of varying arterial oxygen saturation (Sao2) were studied during cardiac catheterization. Sco2, Sao2, and jugular bulb oxygen saturation (Sjo2) were measured by frequency domain near-infrared spectroscopy and blood oximetry at normocapnia room air, normocapnia 100% inspired O2, and hypocapnia room air. RESULTS: Among subject conditions, Sao2 ranged from 68% to 100%, Sjo2 from 27% to 96%, and Sco2 from 29% to 92%. Sco2 was significantly related to Sao2 (y = 0. 85 x -17, r = 0.47), Sjo2 (y = 0.77 x +13, r = 0.70), and the combination (Sco2 = 0.46 Sao2 + 0.56 Sjo2 - 17, R = 0.71). The arterial and venous contribution to cerebral oximetry was 16 +/- 21% and 84 +/- 21%, respectively (where Sco2 = alpha Sao2 + beta Sjo2 with alpha and beta being arterial and venous contributions). The contribution was similar among conditions but differed significantly among subjects (range, approximately 40:60 to approximately 0:100, arterial:venous). CONCLUSIONS: Cerebral oximetry monitors an arterial/venous ratio of 16:84, similar in normoxia, hypoxia, and hypocapnia. Because of biologic variation in cerebral arterial/venous ratios, use of a fixed ratio is not a good method to validate the technology.     

Cerebral autoregulation is impaired in patients resuscitated after cardiac arrest

Background : Cerebral autoregulation is important to maintain a constant perfusion in the face of changes in blood pressure. It is reported to be impaired in pathologic states, including hypertension, cerebral infarction, and head injury. However, it is not clear whether cerebral autoregulation is impaired in resuscitated patients after cardiac arrest. Methods : Cerebral autoregulation in comatose patients after cardiac arrest was assessed by using an indirect method of cerebral blood flow (CBF). Eight patients who had cardiac arrest outside of the hospital and were successfully resuscitated in the emergency room were included in this study. A catheter was inserted percutaneously into the right internal jugular vein and positioned so that the tip was in the jugular bulb. Mean arterial pressure (MAP) was changed to a value of 30% lower or higher than baseline MAP by infusing trimethaphan or methoxamine, respectively. At each MAP level, arterial and jugular bulb venous blood gases were measured, and arterial-jugular bulb venous oxygen content difference (AVDO₂) was calculated. Results : The 1/AVDO₂ (CBFI) and oxygen saturation of jugular bulb venous blood (S_jvO₂) significantly decreased at the lower MAP level, and significantly increased at the higher MAP level. The ratio of the CBFI at the lower MAP level to the CBFI at baseline (CBFI-L/CBFI-B) inversely correlated with the S_jvo₂ at baseline. Conclusions : Assuming that the cerebral metabolic rate of oxygen does not change during the interventions in MAP, the changes of CBFI and S_jvO₂ seen after the decrease or increase in MAP indicate that cerebral autoregulation was impaired in these resuscitated patients. The degree of the impairment of cerebral autoregulation may be secondary to the degree of brain injury caused by the cerebral ischemia accompanying cardiac arrest.     

Use of cerebral oximetry to detect and manage cerebral desaturation with a rapidly expanding neck hematoma

BACKGROUND: We report a case in which cerebral oximetry was used to successfully demonstrate when cerebral oxygen saturation is dangerously low. METHODS: In a 60-year-old-man with end-stage multiple myeloma and hyperviscosity syndrome, a rapidly expanding hematoma developed after insertion of an internal jugular central venous catheter. As the hematoma expanded, the patient became lethargic and disoriented (Glasgow Coma Score of E2/M4-5/V2-ETT). His platelet count was 17,000.mm(-3), hemoglobin was 4.5 g/dl, partial thromboplastin time was 51 s, and his international ratio was 1.7. Although carotid pulses became unpalpable, blood pressure and heart rate remained stable. Cerebral oximeter probes positioned on the patient's forehead showed that cerebral oxygen saturation was 22-26% bilaterally. The surgery team was advised to surgically evacuate the hematoma. RESULTS: The hematoma was evacuated and a small needle hole in the right internal jugular vein adjacent to the central-venous catheter was found and repaired. Cerebral oxygen saturation increased to 56-58% within 1 h and stabilized near 60%. The patient awoke with normal cognitive function. CONCLUSION: This case demonstrates how cerebral oximetry can be used to give quantitative evidence of cerebral hypoxia, thus showing that immediate surgical intervention is necessary.     

Slow rewarming improves jugular venous oxygen saturation during rewarming

BACKGROUND: There have been many studies regarding the etiology of postoperative cognitive dysfunction after coronary artery bypass graft (CABG) surgery. Although its etiology remains unresolved, one possible factor related to postoperative cognitive dysfunction is a reduced internal jugular venous oxygen hemoglobin saturation (SjvO2) during the rewarming period. The purpose of this study was to examine the effect of rewarming rates on SjvO2 during rewarming. METHODS: One-hundred patients scheduled for elective CABG surgery were randomly divided into two groups; control group (0.48 +/- 0.09 degrees C, n = 50), slow rewarming group (0.24 +/- 0.09 degrees C, n = 50). After the induction of anesthesia, a fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to monitor SjvO2 continuously. Hemodynamic parameters, arterial and jugular venous blood gases were measured at nine time-points. RESULTS: Cerebral desaturation (defined as a SjvO2 value below 50%) during rewarming was more frequent in the control group than in the slow group. Cerebral desaturation time (duration when SjvO2 was less than 50%) and the ratio of the cerebral desaturation time to the total CPB time in the control group differed significantly from those in the slow group (control group: 17 +/- 11 min, 12 +/- 4%, slow group: 10 +/- 8 min, 7 +/- 4%, respectively, P < 0.05). There was no significant difference in mini-mental state examination on the day before the operation nor at 1 month after the surgery among four values (the day before the operation: control group; 48 +/- 8, slow group; 48 +/- 7, at one month after the surgery: control group; 46 +/- 7, slow group; 45 +/- 9). CONCLUSIONS: A slow rewarming rate could reduce the chance of a decrease in SjvO2 during rewarming.     

Balloon pump-induced pulsatile perfusion during cardiopulmonary bypass does not improve brain oxygenation.

BACKGROUND: Whether pulsatile flow offers substantial advantages for brain protection during cardiopulmonary bypass is controversial. The purpose of this study is to determine whether differences exist between pulsatile and nonpulsatile bypass concerning the effects on internal jugular venous saturation and on the state of regional cerebral oxygenation during normothermia. METHODS: Twenty-two patients undergoing elective coronary artery bypass grafting were randomly divided into 2 groups: group 1 (n = 11) received nonpulsatile perfusion during cardiopulmonary bypass and group 2 (n = 11) received pulsatile perfusion during bypass. We used an intra-aortic balloon pump to generate pulsatility. A spectrophotometric probe (INVOS 3100R, Somanetics, Troy, Mich) was used to assess the state of regional cerebral oxygenation. A 4F fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to monitor jugular venous oxygen saturation. Hemodynamic variables, arterial and jugular venous blood gases, and regional cerebral oxygenation were measured at 7 times points. RESULTS: In both groups, jugular venous oxygen saturation decreased at the early stage of the cardiopulmonary bypass (P =.03). Five patients in group 1 and 6 in group 2 had a jugular venous oxygen saturation of less than 50%. In both groups, the regional cerebral oxygenation value decreased during cardiopulmonary bypass (P =.04). CONCLUSIONS: The present results showed that pulsatility generated through the use of intra-aortic balloon pumping did not produce any beneficial effects on jugular venous oxygen saturation and regional cerebral oxygenation at normothermia.     

Oxygen saturation monitoring

Pulse-oximeter is described as the most important technological proceeding for monitoring the patients' safety during anesthesia, after surgery and in emergency. This opinion was widely confirmed in the 1990s when pulse-oximeter has been definitively introduced in the standard for base monitoring in the OR and has been proposed for routinary use also in the ICU. In this paper we consider the importance, in the cardiovascular, respiratory and brain parameters monitoring, of continuous oximetry of mixed venous blood (SVO2) and blood venous saturation in the internal jugular vein (SjvO2).     

The association of high jugular bulb venous oxygen saturation with cognitive decline after hypothermic cardiopulmonary bypass

This study was conducted to investigate whether jugular bulb venous oxygen saturation (SjVO(2)) predicted cognitive decline after cardiac surgery with hypothermic cardiopulmonary bypass (CPB). We studied 35 patients undergoing cardiac surgery. After the induction of anesthesia, a 5.5F fiberoptic oximetry catheter was retrogradely inserted into the jugular bulb, and SjVO(2) and other cerebral oxygenation variables were analyzed before, during, and after CPB. At each point, an oxyhemoglobin dissociation curve was drawn, and the P(50) value of jugular bulb venous blood was calculated by computer analysis. Cognitive function was assessed with the revised version of Hasegawa's Dementia Scale and the Benton Revised Visual Retention Test before and early after the operation. In 15 patients (the Decline group), cognitive function was declined after surgery, whereas it remained unchanged in 20 patients (the Normal group). SjVO(2) was significantly higher and cerebral oxygen extraction was significantly lower before and during CPB in the Decline group than in the Normal group (P < 0.05). The oxygen pressure at an oxygen saturation of 50% was significantly lower before and after CPB in the Decline group than in the Normal group (P < 0.05). Logistic regression analysis showed that high SjVO(2) was a predictor of cognitive decline after cardiac surgery. We conclude that high SjVO(2) was associated with cognitive decline after cardiac surgery with hypothermic CPB. IMPLICATIONS: Jugular bulb venous oxygen desaturation has been suggested as a predictor of cognitive decline after cardiac surgery. However, the clinical value of jugular bulb venous oxygen saturation (SjVO(2)) may be limited during hypothermic cardiopulmonary bypass (CPB) when oxygen affinity to hemoglobin is increased. This study shows that high SjVO(2) before and during hypothermic CPB is a predictor of subsequent cognitive decline.     

Arterial and Venous Contributions to Near-infrared Cerebral Oximetry

Background: Cerebral oximetry is a noninvasive bedside technology using near-infrared light to monitor cerebral oxygen saturation (Sco2) in an uncertain mixture of arteries, capillaries, and veins. The present study used frequency domain near-infrared spectroscopy to determine the ratio of arterial and venous blood monitored by cerebral oximetry during normoxia, hypoxia, and hypocapnia.

Methods: Twenty anesthetized children aged < 8 yr with congenital heart disease of varying arterial oxygen saturation (Sao2) were studied during cardiac catheterization. Sco2, Sao2, and jugular bulb oxygen saturation (Sjo2) were measured by frequency domain near-infrared spectroscopy and blood oximetry at normocapnia room air, normocapnia 100% inspired O2, and hypocapnia room air.

Results: Among subject conditions, Sao2 ranged from 68% to 100%, Sjo2 from 27% to 96%, and Sco2 from 29% to 92%. Sco2 was significantly related to Sao2 (y = 0.85 x -17, r = 0.47), Sjo2 (y = 0.77 x +13, r = 0.70), and the combination (Sco2 = 0.46 Sao2 + 0.56 Sjo2 - 17, R = 0.71). The arterial and venous contribution to cerebral oximetry was 16 +/- 21% and 84 +/- 21%, respectively (where Sco2 = [alpha] Sao2 + [beta] Sjo2 with [alpha] and [beta] being arterial and venous contributions). The contribution was similar among conditions but differed significantly among subjects (range, [almost equal to] 40:60 to [almost equal to] 0:100, arterial:venous).     

Measuring brain tissue oxygenation compared with jugular venous oxygen saturation for monitoring cerebral oxygenation after traumatic brain injury

Jugular bulb oximetry is the most widely used method of monitoring cerebral oxygenation. More recently, measurement of brain tissue oxygenation has been reported in head-injured patients. We compared the changes in brain tissue oxygen partial pressure (PbO2) with changes in jugular venous oxygen saturation (SjVO2) in response to hyperventilation in areas of brain with and without focal pathology. Thirteen patients with severe head injuries were studied. A multiparameter sensor was inserted into areas of brain with focal pathology in five patients and outside areas of focal pathology in eight patients. A fiberoptic catheter was inserted into the right jugular bulb. Patients were hyperventilated in a stepwise manner from a PaCO2 of approximately 35 mm Hg to a PaCO2 of 22 mm Hg. There was no significant change in cerebral perfusion pressure or arterial partial pressure of oxygen with hyperventilation. In areas without focal pathology, there was a good correlation between changes in SjVO2 and PbO2 (deltaSjVO2 and deltaPbO2; r2 = 0.69, P < 0.0001). In areas with focal pathology, there was no correlation between deltaSjVO, and APbO2 (r2 =0.07, P = 0.23). In this study, we demonstrated that measurement of local tissue oxygenation can highlight focal differences in regional cerebral oxygenation that are disguised when measuring SjVO2. Thus, monitoring of PbO2 is a useful addition to multimodal monitoring of patients with traumatic head injury. IMPLICATIONS: Brain oxygenation is currently monitored by using jugular bulb oximetry, which attracts a number of potential artifacts and may not reflect regional changes in oxygenation. We compared this method with measurement of brain tissue oxygenation using a multiparameter sensor inserted into brain tissue. The brain tissue monitor seemed to reflect regional brain oxygenation better than jugular bulb oximetry.     

Zerebrale Oxymetrie

The determination of cerebral oxygen saturation (S_cO₂) by means of near-infrared spectroscopy allows non-invasive assessment of the cerebral oxygen delivery and demand ratio in the frontal cortex region. Studies in cardiac as well as non-cardiac patients have shown that maintaining S_cO₂ in the preoperative range reduces the incidence of postoperative cognitive dysfunction and general morbidity; however, S_cO₂ is not only reflective of cerebral but also of systemic oxygen balance, is inversely related to cardiopulmonary function and has prognostic relevance in cardiac surgery patients. This suggests that cerebral oximetry is not only useful for neurological but also for hemodynamic monitoring and preoperative risk stratification of cardiac surgery patients.     

Factors Associated with Postoperative Cognitive Dysfunction in Patients Undergoing Cardiac Surgery

Purpose Central nervous system complications continue to be major causes of morbidity and mortality after cardiac surgery. The purpose of this study was to identify the risk factors for postoperative cognitive dysfunction after coronary artery bypass graft (CABG) surgery. Methods Eighty-eight patients scheduled for elective CABG were studied. After the induction of anesthesia, a fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb for the continuous monitoring of jugular venous oxygen hemoglobin saturation (SjvO₂). The hemodynamic parameters and arterial and jugular venous blood gases were measured during cardiopulmonary bypass (CPB). All patients underwent a battery of neurological and neuropsychological tests one day before the operation and at 6 months after the operation. Results The incidence of a cognitive decline at 6 months was 24/88 (27.3%). Greater age (P = 0.04), the presence of renal failure (P < 0.001), and diabetes mellitus (P < 0.001) were more frequent in the patients with postoperative cognitive dysfunction at 6 months after the operation than in patients without cognitive dysfunction. Age (odds ratio [OR], 1.4; 95% confidence interval [CI], 1.0–1.7; P = 0.04), diabetes mellitus (OR, 1.8; 95% CI, 1.2–2.4; P < 0.01), and presence of renal failure (OR, 2.8; 95% CI, 2.4–4.3; P < 0.01) were associated with cognitive impairment at 6 months postoperatively. However, there was no relationship between the presence of atherosclerosis in the ascending aorta and postoperative cognitive dysfunction after CABG surgery. Conclusions A greater age, diabetes mellitus, and renal failure were found to be risk factors for development of cognitive impairment at 6 months after CABG with CPB.     

Prediction of cognitive dysfunction and patients' outcome following valvular heart surgery and the role of cerebral oximetry.

OBJECTIVE: Postoperative cognitive dysfunction (POCD) commonly develops after cardiac surgery affecting patients' outcome. Cerebral oximetry noninvasively measures regional cerebral oxygen saturation (rSO(2)) and significant correlation has been reported between intraoperative cerebral desaturation and POCD, as well as patients' outcome following coronary artery bypass grafting. However, evidence is limited in valvular heart surgery (VHS). We investigated the relationship of intraoperative rSO(2) values with POCD and length of postoperative hospitalization in patients undergoing VHS. METHODS: One hundred patients undergoing elective VHS were enrolled. Neurocognitive evaluation was performed with Mini-Mental State Examination, Trail-Making Test (Part A), and Grooved Pegboard Test at 1 day before and 7th day after surgery. During surgery, rSO(2) was continuously monitored and the incidence and duration of decrease in rSO(2) values for five consecutive minutes were recorded as follows; (1) decrease in absolute rSO(2) values to less than 50%, (2) 40%, and (3) a 20% decrease compared to baseline value. RESULTS: Twenty-three patients (23%) demonstrated POCD. We could not observe any significant differences in either the incidence or duration of decrease in rSO(2) values between patients with and without POCD. Low education level and higher baseline temperature had significant correlation with POCD. Patients with cerebral desaturation required significantly longer postoperative hospitalization. CONCLUSION: In patients undergoing VHS, POCD could not be predicted with cerebral oximetry. However, patients with intraoperative cerebral desaturation required significantly longer postoperative hospitalization and cerebral oximetry appears to be promising in terms of monitoring the brain as the index organ for systemic perfusion and improving patients' outcome.     

Hypothermie et protection cérébrale après traumatisme crânien. Influence des gaz du sang

The usefulness of therapeutic hypothermia is highly debated after traumatic brain injury. A neuroprotective effect has been demonstrated only in experimental studies: decrease in cerebral metabolism, restoration of ATP level, better control of cerebral edema and cellular effects. Despite negative multicenter clinical studies, therapeutic hypothermia is still used to a better control of intracranial pressure. However, important issues need to be clarified, particularly the level and duration of hypothermia, the depth and modalities of sedation. A clear understanding of blood gases variations induced by hypothermia is needed to understand the cerebral perfusion and oxygenation changes. It is essential to recognize and to use hypothermia-induced physiological hypocapnia and alkalosis under strict control of cerebral oxygen balance (jugular venous saturation or tissue PO₂) and also to take into account the increased affinity of hemoglobin for oxygen. Management of post-traumatic intracranial hypertension using hypothermia, directed by intracranial pressure level, and consequently for long duration, is potentially beneficial but needs further clarification.