Georg Grubhofer

Complete revascularization in coronary artery bypass grafting with and without cardiopulmonary bypass.

BACKGROUND The feasibility of complete revascularization on the beating heart without cardiopulmonary bypass (CPB) as compared with the standard operation with CPB in elective low-risk patients with multivessel disease has not been clearly demonstrated in a prospective trial. METHODS Eighty selected low-risk patients were enrolled. In preoperative study with coronary angiography, the decision was made whether complete revascularization without CPB could be performed. Patients were randomly assigned to receive CABG either with (n = 40) or without CPB (n = 40). Randomization criteria were age, sex, and left ventricular ejection fraction. Completeness of revascularization as well as short- and mid-term clinical outcome in a 13.4 +/- 6.5 month follow-up period were monitored. RESULTS Twenty-six of 40 (65%) patients undergoing CABG without CPB underwent complete revascularization. In 5 of these patients (12.5%) suitable vessels were discarded for technical reasons and 9 patients (22.5%) were switched to CABG with CPB owing to the deeply intramyocardial course of target vessels (n = 5) or to hemodynamic instability (n = 4). In the group of patients operated on with CPB, 34 of 40 patients (85%) received complete revascularization. In 6 patients (15%) suitable vessels were discarded for technical reasons. Mean number of bypass grafts was 3.1 +/- 0.8 with CPB and 2.6 +/- 0.5 without CPB (p = 0.043). Clinical outcome and hospital stay were comparable in both groups. No patient died during the study period. No myocardial infarction was observed. Three patients undergoing CABG without CPB underwent successful PTCA 3 months after surgery. CONCLUSIONS CABG without the use of CPB is effective for complete revascularization in the majority of selected low-risk patients. Nevertheless, it has to be stated that the rate of incomplete revascularization in this early series of CABG without CPB is higher, and compromises the basic principle of complete revascularization.

Inhaled Nitric Oxide Reduces Pulmonary Vascular Resistance More Than Prostaglandin E1 During Heart Transplantation

Heart transplantation in patients with increased pulmonary vascular resistance is often associated with postbypass right heart failure. We therefore compared the abilities of prostaglandin E1 (PGE1) and inhaled nitric oxide to reduce pulmonary vascular resistance during heart transplantation. Patients undergoing orthotopic heart transplantation for congestive heart failure were randomly assigned to either a PGE1 infusion at a rate of 8 ng · kg· −1min−1 starting 10 min before weaning from cardiopulmonary bypass (CPB) (n = 34) or inhalation of 4 ppm nitric oxide starting just before weaning from CPB (n = 34). Both treatments were increased stepwise, if necessary, and were stopped 6 h postoperatively. Hemodynamic values were recorded after the induction of anesthesia, 10 and 30 min after weaning from CPB, and 1 h and 6 h postoperatively. Immediately after weaning from CPB, pulmonary vascular resistance was nearly halved in the nitric oxide group but reduced by only 10% in the PGE1 group. Pulmonary artery pressure was decreased approximately 30% during nitric oxide inhalation, but only approximately 16% during the PGE1 infusion. Six hours after surgery, pulmonary vascular resistance and pulmonary artery pressure were similar in the two groups. The ratio between pulmonary vascular resistance and systemic vascular resistance was significantly less in the nitric oxide patients at all postbypass times. In contrast, the pulmonary-to-systemic vascular resistance ratio increased approximately 30% in the patients given PGE1. Cardiac output, heart rate, mean arterial pressure, right atrial pressure, and pulmonary wedge pressure did not differ between the groups. Weaning from CPB was successful in all patients assigned to nitric oxide inhalation; in contrast, weaning failed in six patients assigned to PGE1 (P = 0.03). Implications: Nitric oxide inhalation selectively reduces pulmonary vascular resistance and pulmonary artery pressure immediately after heart transplantation which facilitates weaning from cardiopulmonary bypass.

Impact of retrograde cerebral perfusion on aortic arch aneurysm repair

OBJECTIVE Protection of the brain is a primary concern in aortic arch surgery. Retrograde cerebral perfusion is a relatively new technique used for cerebral protection during profound hypothermic circulatory arrest. This study was designed to compare, retrospectively, the outcome of 109 patients undergoing aortic arch operation with and without the use of retrograde cerebral perfusion. METHODS Fifty-five patients had profound hypothermic circulatory arrest alone, and 54 patients had supplemental cerebral protection with retrograde cerebral perfusion. Mean age was 61 +/- 13 years and 58 +/- 14 years, respectively (mean +/- standard deviation). Twenty-two preoperative and intraoperative characteristics, including age, sex, acuity, presence of aortic dissection, and aneurysm rupture, were similar in the 2 groups (P >.05). RESULTS Mean circulatory arrest times (in minutes) were 30 +/- 19 in the group without retrograde cerebral perfusion and 33 +/- 19 in the group with retrograde cerebral perfusion, respectively. chi(2) Analysis revealed that patients operated on with the use of retrograde cerebral perfusion had significantly lower hospital mortality (15% vs 31%; P =.04) and in-hospital permanent neurologic complications (9% vs 27%; P =.01). Retrograde cerebral perfusion failed to reduce the prevalence of temporary neurologic dysfunction (17% vs 18%; P =.9). Stepwise multiple logistic regression revealed that extracorporeal circulation time, age, and lack of retrograde cerebral perfusion were statistically significant independent risk factors for hospital mortality. The same analysis revealed that lack of retrograde cerebral perfusion was the only significant independent risk factor for permanent neurologic dysfunction. CONCLUSION Retrograde cerebral perfusion decreased the prevalence of permanent neurologic complications and the hospital mortality in patients undergoing aortic arch operations.

Cerebral oxygenation during cardiopulmonary bypass measured by near-infrared spectroscopy: Effects of hemodilution, temperature, and flow

OBJECTIVE To determine the effects of hemodilution, PaCO2, PaO2, arterial pressure, and temperature on cerebral oxygenation during mild hypothermic cardiopulmonary bypass (CPB). PARTICIPANTS Fourteen patients electively scheduled for cardiac surgery. INTERVENTIONS Oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), hemoglobin differential (Hb-diff = HbO2-Hb), and oxidized cytochrome aa3 (CtO2) were measured with near-infrared spectroscopy (NIRS) during CPB. RESULTS With onset of CPB, a significant decrease in HbO2 (median, -4.55 micromol/L; 25th to 75th percentile, -5.5 to -3.1; p < 0.05), Hb-diff (median, -3.88 micromol/L; 25th to 75th percentile, -4.7 to -1.9; p < 0.05), and CtO2 (median, -0.05 micromol/L; 25th to 75th percentile, -0.15 to 0; p < 0.001) occurred. The simultaneous decrease in arterial hemoglobin concentration (from 11.7 to 8.5 g/100 mL, p < 0.005) correlated significantly with changes in HbO2 (r2 = 0.71; p < 0.001), Hb-diff (r2 = 0.59; p < 0.005), and CtO2 (r2 = 0.57; p < 0.005). After 24 minutes of CPB, the largest decline in HbO2 (-5.03 micromol/L) and Hb-diff (-5.68 micromol/L) was recorded, whereas CtO2 showed no changes during cooling. During CPB, Hb and Hb-diff significantly correlated with the duration of CPB, PaO2 and PaCO2. CONCLUSIONS In early stages of CPB, a diminished cerebral oxygen supply was found, which may be caused by acute hemodilution. Despite an increased extraction of oxygen as demonstrated by the decrease in Hb-diff, cerebral energy balance reflected by CtO2 was maintained within a safe range during cooling. Because NIRS measures regional cerebral oxygenation, it is useful as an adjunct to global measures in the early noninvasive detection of cerebral hypoxia.

Randomized clinical trial comparing double-lumen tube and EZ-Blocker® for single-lung ventilation

BACKGROUND In several clinical situations, lung separation and single-lung ventilation (SLV) is essential. In these cases, the double-lumen tube (DLT) is the most widely used device. Bronchial blocker such as Univent or Arndt Blocker serves as an alternative. The EZ-Blocker(®) (EZ; AnaesthetIQ B.V., Rotterdam, The Netherlands) is a new device promising to exceed clinical performance of DLT. The aim of this study was to assess the clinical performance of EZ in comparison with conventional left-sided DLT. METHODS Forty adult patients undergoing elective thoracic surgery requiring thoracotomy and SLV were included in this study. The patients were randomly assigned to one of two groups: EZ (combined with conventional 7.5 or 8.5 mm single-lumen tube) or DLT (37 or 39 Fr left-sided DLT). Time for intubation procedure and time to verification of the correct position of EZ or DLT using fibreoptic bronchoscopy (FOB) were recorded. After surgery, a thoracic surgeon rated the quality of collapse of the lung (1-3 on a three-level scale). RESULTS Time for intubation using DLT 85.5 (54.8) s was significantly faster (P<0.001) than using EZ 192 (89.7) s, whereas time for bronchoscopy was not significantly different (P=0.556). Conditions of surgery were rated equally [DLT 1.3 (0.6) vs EZ 1.4 (0.6), P=0.681]. CONCLUSIONS Although time for intubation was longer with the EZ, the device proved to be an efficient and easy-to-use device. The EZ is a valuable alternative device to conventional DLT. Verification of the correct position of the EZ by FOB seems to be obligatory. This study was registered at http://www.clinicaltrials.gov (identifier: NCT01171560).

Comparing Doppler Ultrasonography and Cerebral Oximetry as Indicators for Shunting in Carotid Endarterectomy

To determine the thresholds of selective shunting in carotid endarterectomy during general anesthesia, we compared transcranial Doppler ultrasonography and cerebral oximetry (RSO2). During carotid cross-clamping, RSO2 and mean blood flow velocity in the middle cerebral artery (Vm, mca) was simultaneously monitored in 55 of 59 patients. A relative decrease in Vm, mca to <20% of preclamp velocity was the indication for selective shunting. Three patients were shunted, two because of criteria of Vm, mca and one in which Vm, mca measurements were impossible. No postoperative neurological deficits occurred. During cross-clamping, both Vm, mca (42 ± 16 vs 26 ± 12 cm/s;P < 0.001) and RSO2 (68 ± 7% vs 62 ± 8%;P < 0.01) decreased and a significant correlation between %Vm, mca and &Dgr;RSO2 was found (R2 =0.40;P = 0.003). Decreases in RSO2 >13% identified two patients later shunted; however, this threshold would have indicated unnecessary shunting in seven patients (false positives = 17%). Transcranial Doppler ultrasonography identified patients at risk for ischemia more accurately than RSO2. Relying on RSO2 alone would increase the number of unnecessary shunts because of the low specificity. Accepting higher decreases in RSO2 does not appear reasonable because it bears the risk of a low sensitivity. Implications Although cerebral oximetry was easy to apply but considerably unspecific (13% false positives), transcranial Doppler ultrasonography was more accurate in indicating the risk of cerebral hypoperfusion during carotid cross-clamping. Additionally, the improvement in cerebral blood flow velocity after inducing arterial hypertension might prevent cerebral hypoperfusion during cross-clamping.

Release of neuron-specific enolase and S100 after implantation of cardioverters/defibrillators.

ObjectiveRepeated induction of ventricular fibrillation with ensuing alterations in electroencephalogram and jugular venous oxygen saturation is common practice during insertion of transvenous implantable cardioverters/defibrillators. We investigated whether these functional changes are also associated with cerebral injury. DesignProspective study. SettingUniversity hospital. PatientsWe studied 45 patients undergoing implantable cardioverter/defibrillator insertion. Eleven patients with cardiac pacemaker implantation, which was performed in the same manner yet without the necessity to induce ventricular fibrillation, served as controls. Measurements and Main ResultsSerum neuron-specific enolase and S100 were determined before, immediately postoperatively, and 2 hrs postoperatively. In a randomly composed subgroup, neuron-specific enolase was also determined 6 and 24 hrs after surgery. Implantable cardioverter/defibrillator patients only showed an increase of both markers postoperatively. Median neuron-specific enolase values climbed from a preoperative 9.9 to 12.3 and 14.4 &mgr;g/L at 2 and 24 hrs after surgery, respectively. This increase was associated with the number of shocks and the cumulative time in circulatory arrest. The highest median S100 level (0.075 &mgr;g/L) was reached 2 hrs after the procedure. Neuron-specific enolase and S100 were extremely elevated (13.7 and 0.970 &mgr;g/L, respectively) in one patient after an extended episode of ventricular fibrillation. Plasma hemoglobin levels were in the normal range in implantable cardioverter/defibrillator patients throughout the observation period. ConclusionsApparently, even brief successive periods of global cerebral ischemia cause neuronal damage without obvious severe neurologic deficits. However, they may be related to subtle postoperative neurologic or cognitive dysfunctions that a number of implantable cardioverter/defibrillator patients exhibit after implantation.

MONITORING OF MEDIAN NERVE SOMATOSENSORY EVOKED POTENTIALS IN CAROTID SURGERY

The purpose of this study was to compare median somatosensory evoked potentials (SEP) in patients undergoing carotid endarterectomy (CEA) with routine shunting and nonshunting (excluding the option of selective shunting) and to evaluate the significance of a decrease in the amplitude of the cortically generated waveforms of the SEP and/or an increase in the central conduction time (CCT) on the one hand, and that of a loss of the cortical SEP, on the other. Somatosensory evoked potentials were recorded in 32 patients before, during, and after CEA with routine shunting or nonshunting. The N13 and N20 latency, the CCT, and the N20/P25 amplitude were evaluated. In addition, a meta-analysis of 15 previous studies was performed comprising a total of 3,136 patients. The intraoperative cortical SEP showed no differences between shunted and nonshunted patients, apart from the preclamping value of the N20/P25 amplitude which was lower in the nonshunted subjects. The number of patients with decreased and/or delayed cortical SEP (findings frequently used as criterion for selective shunting) was similar in the two study groups. A loss of the cortical SEP occurred in one patient operated on without an indwelling shunt. None of these patients had a new neurologic deficit after surgery. In the meta-analysis, the positive predictive value of decreased and/or delayed cortical SEP was extremely poor, that of absent cortical SEP was poor to moderate and the prevalence of new neurologic deficits was similar in patients undergoing CEA with routine shunting-nonshunting and those with selective shunting-nonshunting. Our study suggests that decreased and/or delayed cortical SEP are unreliable predictors of the neurological outcome of CEA patients and consequently an unsuitable criterion for selective shunting. The meta-analysis confirms this finding and shows that the neurologic outcome is not improved by using an indwelling shunt selectively based on SEP monitoring.

Effects of dobutamine versus insulin on cardiac performance, myocardial oxygen demand, and total body metabolism after coronary artery bypass grafting

OBJECTIVE The purpose was to study whether the hemodynamic benefit of a catabolic catecholamine (dobutamine) induces a certain oxygen cost for the myocardial energy demand and whether this effect would be less pronounced if an anabolic intervention, such as the administration of insulin, was used. DESIGN A prospective and randomized study. SETTING A university hospital. PARTICIPANTS Investigation of two comparable groups of cardiac patients. INTERVENTIONS The interventions were postoperative infusions of dobutamine, 7 micrograms/kg/min, and of insulin, 1.5 U/kg/h, respectively, over a period of 30 minutes. MEASUREMENTS AND MAIN RESULTS The effects of the interventions were measured using parameters relating to cardiac work and myocardial oxygen demand. Moreover, parameters relating to total body metabolism were also recorded. In the dobutamine group, cardiac index (CI) and left ventricular stroke work index (LVSWI) increased significantly (p < 0.05) during therapy by 30% and 40%, respectively. Cardiac effort index (CEI) and tension time index (TTI) also increased (p < 0.05) during therapy by 41% and 30%, respectively. However, in the insulin group, CI and LVSWI also increased (p < 0.01 and p < 0.05) during therapy, although to a lesser extent (16% and 14%), but CEI and TTI did not change at all during therapy. Total body CO2 production (VCO2) and O2 consumption (VO2) in the dobutamine group increased (p < 0.05) during therapy by 9% and 11%, respectively, whereas in the insulin group only CO2 production increased (p < 0.05) by 13%. O2 consumption remained unchanged in this group. CONCLUSIONS It is concluded that dobutamine as well as insulin administration increase cardiac performance. However, in contrast to dobutamine, insulin does not appear to increase myocardial oxygen demand. Therefore, the anabolic insulin administration may represent a more economic pattern of energy-consuming hemodynamic intervention than does the catabolic catecholamine administration.

Jugular venous bulb oxygen saturation depends on blood pressure during cardiopulmonary bypass.

BACKGROUND Central nervous system dysfunction after cardiopulmonary bypass is frequent and can be caused by inadequate cerebral perfusion and oxygenation. METHODS To test the effectiveness of cerebral autoregulation during cardiopulmonary bypass, we induced changes in the cerebral perfusion pressure by administering phenylephrine during moderate (29 degrees C) hypothermia. Using the Fick principle, we calculated relative changes in cerebral blood flow from changes in the jugular venous bulb oxygen saturation. RESULTS Increasing the cerebral perfusion pressure (from 47 +/- 8.2 to 93 +/- 16 mm Hg) induced increases in the jugular venous bulb oxygen saturation by 4.9% and a calculated increase in the cerebral blood flow by 19.9%, strongly suggesting impaired cerebral autoregulation. CONCLUSIONS Because cerebral autoregulation is impaired during cardiopulmonary bypass, phenylephrine is effective in increasing the cerebral blood flow and may contribute to the prevention of postoperative neurologic dysfunction, especially in patients who have a low jugular venous bulb oxygen saturation.