Lidocaine/tetracaine patch (Rapydan) for topical anaesthesia before arterial access: a double-blind, randomized trial.

BACKGROUND: Arterial catheterization is painful and is associated with patient stress and anxiety. Analgesia is usually provided by subcutaneous injection of local anaesthetic. An alternative is topical anaesthesia, such as Rapydan which is a novel topical anaesthetic patch containing 70 mg each of lidocaine and tetracaine. We therefore tested the hypothesis that Rapydan patch analgesia is non-inferior to subcutaneous local anaesthetic. METHODS: Ninety patients undergoing elective major cardiac surgery were included in this prospective, double-blind clinical trial. Patients were randomly assigned to receive either a lidocaine/tetracaine patch, followed by subcutaneous injection 0.5 ml of normal saline solution, or placebo patch with subsequent subcutaneous injection of 0.5 ml of lidocaine 1%. Pain during arterial catheterization using 100-mm-long visual analogue scale (VAS) was the primary outcome. Other outcomes were pain during anaesthetic/saline injection and plasma tetracaine concentrations. RESULTS: VAS pain scores during arterial puncture were comparable in both groups and Rapydan was non-inferior to subcutaneous lidocaine. Pain scores at the time of subcutaneous injection were significantly lower (better) in patients assigned to the lidocaine/tetracaine patch than to lidocaine (P=0.001). Plasma tetracaine concentrations never exceeded the detection limit of 25 ng ml(-1) at any time in any patient. CONCLUSIONS: Both the lidocaine/tetracaine patch and subcutaneous injection of lidocaine provided comparable pain control during arterial catheter insertion. Subcutaneous lidocaine caused discomfort during injection, whereas the lidocaine/tetracaine patch required placement 20 min before the procedure. Given adequate time, the patch provided better overall analgesia by obviating the need for subcutaneous infiltration.

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).

Magnesium moderately decreases remifentanil dosage required for pain management after cardiac surgery.

BACKGROUND: Magnesium is a calcium and an NMDA-receptor antagonist and can modify important mechanisms of nociception. We evaluated the co-analgesic effect of magnesium in the postoperative setting after on-pump cardiac surgery. METHODS: Forty patients randomly received either magnesium gluconate as an i.v. bolus of 0.21 mmol kg(-1) (86.5 mg kg(-1)) followed by a continuous infusion of 0.03 mmol(-1) kg(-1) h(-1) (13.8 mg kg(-1) h(-1)) or placebo for 12 h after tracheal extubation. After surgery, remifentanil was decreased to 0.05 microg kg(-1) min(-1) and titrated according to a pain intensity score (PIS, range 1-6) in the intubated, awake patient and a VAS scale (range 1-100) after extubation. If PIS was > or =3 or VAS > or =30, the infusion was increased by 0.01 microg kg(-1) min(-1); if ventilatory frequency was < or =10 min(-1) it was decreased by the same magnitude. RESULTS: Magnesium lowered the cumulative remifentanil requirement after surgery (P<0.05). PIS > or =3 was more frequent in the placebo group (P<0.05). Despite increased remifentanil demand, VAS scores were also higher in the placebo group at 8 (2 vs 8) and 9 h after extubation (2 vs 7) (P<0.05). Dose reductions attributable to a ventilatory frequency < or =10 min(-1) occurred more often in the magnesium group (17 vs 6; P<0.05). However, time to tracheal extubation was not prolonged. CONCLUSIONS: Magnesium gluconate moderately reduced the remifentanil consumption without serious side-effects. The opioid-sparing effect of magnesium may be greater at higher pain intensities and with increased dosages.

Perfusion temperature during cardiopulmonary bypass does not affect serum S-100beta release.

BACKGROUND: The potentially harmful effects of normothermia on neurological outcome during cardiopulmonary bypass (CPB) are controversial. METHODS: In this study, we compared the early and late release patterns of S-100beta, a marker of cerebral injury, after normothermic and moderately hypothermic CPB. Forty-eight patients undergoing coronary artery bypass grafting were randomly assigned to either the normothermia (37 degrees C) or the hypothermia (32 degrees C) group. Serum S-100beta levels were measured until 24 h after CPB. Neurological examination was performed before and after surgery. RESULTS: With the exception of intraoperative blood glucose levels, there were no differences between groups. This also applied to peak S-100beta values (Gr-N: 3.5 +/- 1.9 microg/l; Gr-H: 3.5 +/- 3.4 microg/l) and values after 24 h (Gr-N: 0.32 +/- 0.16 microg/l; Gr-H: 0.35 +/- 0.28 microg/l). CONCLUSIONS: The similar pattern of S-100beta release without evident neurological complications in the normothermia group does not suggest an increase in cerebral injury during normothermic CPB.

Can hypocapnia reduce cerebral embolization during cardiopulmonary bypass?

BACKGROUND: Cerebral embolization is a major cause of central nervous dysfunction after cardiopulmonary bypass. Experimental studies demonstrate that reductions in arterial carbon dioxide tension (PaCO2) can reduce cerebral embolization during cardiopulmonary bypass. This study examined the effects of brief PaCO2 manipulations on cerebral embolization in patients undergoing cardiac valve procedures. METHODS: Patients were prospectively randomized to either hypocapnia (PaCO2 = 30 to 32 mm Hg, n = 30) or normocapnia (PaCO2 = 40 to 42 mm Hg, n = 31) before aortic cross-clamp removal. With removal of the aortic cross-clamp embolic signals were recorded by transcranial Doppler ultrasonography for the next 15 minutes. RESULTS: Despite significant differences in PaCO2, groups did not differ statistically in total cerebral emboli counts. The mean number of embolic events was 107 +/- 100 (median, 80) in the hypocapnic group and 135 +/- 115 (median, 96) in the normocapnic group, respectively (p = 0.315). CONCLUSIONS: Due to the high between-patient variability in embolization, reductions in PaCO2 did not result in a statistically significant decrease in cerebral emboli. In contrast to experimental studies, the beneficial effect of hypocapnia on cerebral embolization could not be demonstrated in humans.

Diltiazem versus nitroglycerin for myocardial protection following coronary artery bypass grafting as assessed by dobutamine stress echocardiography.

BACKGROUND: Perioperative infusion of the calcium channel antagonist diltiazem reduces the occurrence and extent of postoperative myocardial ischemia. However, recent reports also mention nitroglycerin as the drug of choice to prevent conduit spasm after coronary bypass grafting. The diagnosis of myocardial ischemia in the perioperative setting is still problematic. Dobutamine stress echocardiography (DSE) is an established technique that combines inotropic stimulation with real-time myocardial imaging and delineates normal and abnormal regional contraction patterns. We assessed the perioperative anti-ischemic effects of diltiazem and nitroglycerin during hemodynamic stress using DSE. METHODS: 50 adult patients were included in a prospective randomized study. Diltiazem or nitroglycerin was used from the onset of extracorporeal circulation until 24 h postoperatively. Dobutamine stress echocardiography was performed in a stepwise fashion 2 to 3 h after elective coronary artery bypass grafting. RESULTS: In 42 of 49 patients, dobutamine stress echocardiography either reached a level of 40 micrograms/kg/min dobutamine or achieved the target heart rate. One patient improved in terms of segmental wall motion abnormalities and three patients developed new abnormalities without corresponding electrocardiographic changes. Analysis of ischemia-sensitive parameters showed lower creatine kinase MB (p = 0.032) and troponin I levels (p = 0.1) in the diltiazem group 24 h postoperatively. Heart rate was significantly lower in the diltiazem group (p = 0.0003). CONCLUSIONS: Under conditions of hemodynamic stress, DSE revealed no significant difference between diltiazem and nitroglycerin with regard to renewed ischemia.

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.

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 DeltaRSO2 was found (R(2) = 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.

Pulsatility does not change cerebral oxygenation during cardiopulmonary bypass.

BACKGROUND: To determine the effect of pulsatility during cardiopulmonary bypass (CPB) on cerebral oxygenation, we measured oxyhaemoglobin (HbO2), deoxyhaemoglobin (Hb) and oxidised cytochrome aa3 (CtO2) with near-infrared spectroscopy (NIRS) in 14 patients electively scheduled for cardiac surgery. METHODS: Cerebral oxygenation was measured during steady state CPB at a core temperature of 32 degrees C. Non-pulsatile flow and pulsatile flow were performed for 10 min each. RESULTS: After 14 min of CPB, HbO2, Hb and CtO2 were significantly below prebypass values. HbO2 and CtO2 did not alter with changing flow patterns. Hb significantly increased both during the period of nonpulsatile (median: -0.7 vs. 0.25 micromol/l; P<0.05) and pulsatile flow (median: 0.25 vs. 0.5 micromol/l; P<0.001). This increase was independent of flow pattern. CONCLUSIONS: Neither oxygenated haemoglobin, nor intracellular oxygenation, represented by CtO2, indicated a beneficial effect of pulsatile perfusion during hypothermic CPB. These results, however, are only valid for short time effects within 10 min before rewarming from CPB and patients without flow-limiting stenoses of the carotid artery.

Inhaled nitric oxide reduces pulmonary vascular resistance more than prostaglandin E(1) during heart transplantation.

UNLABELLED: Heart transplantation in patients with increased pulmonary vascular resistance is often associated with postbypass right heart failure. We therefore compared the abilities of prostaglandin E(1) (PGE(1)) 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 PGE(1) infusion at a rate of 8 ng. kg. (-1)min(-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 PGE(1) group. Pulmonary artery pressure was decreased approximately 30% during nitric oxide inhalation, but only approximately 16% during the PGE(1) 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 PGE(1). 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 PGE(1) (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.

A comparison of the monitors INVOS 3100 and NIRO 500 in detecting changes in cerebral oxygenation.

BACKGROUND: Measurements of cerebral haemoglobin oxygenation of 2 near-infrared spectroscopy devices (INVOS 3100 and NIRO 500) were compared during and after hypocapnia. METHODS: Fifteen awake, healthy volunteers, who hyperventilated to obtain end-tidal CO2 (EtCO2) values of approximately 20 mmHg, were studied. During hyperventilation and 8 min thereafter, EtCO2, INVOS 3100 (RSO2 = regional cerebral oxygenation) and NIRO 500 recordings (HbO2 = oxyhaemoglobin, Hb = deoxyhaemoglobin, Hb-diff = HbO2-Hb, CtO2 = oxidised cytochrome oxidase aa3) were analysed. RESULTS: Hyperventilation induced a significant decline in EtCO2 from 30.5 to 14.7 mmHg (P < 0.001) and RSO2 from 67.1% to 62.7% (P = 0.025). At hypocapnia, only Hb (+1.61 +/- 0.48 mumol/L; P < 0.001) and Hb-diff (-3.01 +/- 2.0 mumol/L; P < 0.001) indicated a decline in cerebral haemoglobin oxygenation. Within 8 min after hyperventilation, both EtCO2 and RSO2 normalised to values insignificantly different from baseline. In contrast, Hb and Hb-diff remained significantly different (Hb: +2.52 +/- 1.28 mumol/l; P < 0.001, Hb-diff: -4.31 +/- 4.0 mumol/L; P < 0.001). A correlation with EtCO2 was found for RSO2 (R = 0.35; P < 0.001) and CtO2 (R = 0.42; P < 0.001). All volunteers were continuously awake and none presented clinical symptoms of cerebral hypoxia. CONCLUSION: Changes in cerebral haemoglobin oxygenation state were reflected more accurately by INVOS 3100 than NIRO 500. The cause may be the different technology of the monitors, since INVOS 3100 eliminates the contribution of extracranial oxygenation.

Systemic blood pressure and cerebral blood flow velocity during carotid surgery.

BACKGROUND: To evaluate the effect of mean arterial blood pressure (MAP) on cerebral perfusion during carotid surgery, we investigated blood flow velocity in the middle cerebral (Vs,mca) using transcranial Doppler ultrasonography (TCD). METHODS: During carotid crossclamping, treatment included either phenylephrine-induced hypertension without shunting (Group XC; n = 11) or insertion of a shunt (Group S; n = 12). RESULTS: Increasing MAP in Group XC before crossclamping (81 + /-13 mmHg to 107 +/- 12 mmHg) caused an increase of Vs,mca (59 +/- 17 cm/s to 75 +/- 20 cm/s; p < 0.001). During crossclamping without a shunt, Vs,mca was not dependent on MAP, and was reduced (mean 47 +/- 24 cm/s) in relation to preclamp values. In Group S, Vs,mca was always dependent on MAP and the preclamp velocity was maintained (before shunt: 75 +/- 26 cm/sec; during shunt: 79 +/- 30 cm/sec). CONCLUSIONS: Although we found an impaired cerebral autoregulation, Vs,mca was independent of MAP during carotid crossclamping. Thus, TCD measurements have to be interpreted with caution during crossclamping, and the effect of induced hypertension has to be confirmed with more invasive measures of cerebral blood flow.

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.

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.

The contribution of extracranial blood oxygenation on near-infrared spectroscopy during carotid thrombendarterectomy.

To determine the contribution of extracranial oxygenation on regional cerebral oxygenation measured by an Invos 3100 near-infrared spectrometer, we measured oxygenation in blood drawn from both the facial vein (draining substantially blood from forehead areas) and the jugular venous bulb. There was no correlation between regional cerebral oxygenation and facial vein oxygenation (p = 0.35) but there was a significant correlation between regional cerebral oxygenation and jugular venous bulb oxygenation (p = 0.027). Linear regression analysis predicted a 3.6% change in regional oxygenation for every 10% change in jugular venous bulb oxygenation. We showed that extracranial tissue oxygenation had a negligible influence on the values recorded using near-infrared spectroscopy. Individual changes in jugular venous bulb oxygenation were poorly reflected. Data obtained by this near-infrared spectroscopy device are an unreliable guide to the adequacy of cerebral oxygenation.

Influence of prostaglandin E1 on tissue ischemia during surgical repair of the abdominal aorta.

OBJECTIVE: To evaluate tissue protection by PGE1 during leg ischemia in patients undergoing aortic surgery. DESIGN: Randomized, controlled prospective clinical trial. SETTING: Single university hospital. PARTICIPANTS: 19 consecutive patients undergoing abdominal aortic aneurysm repair. INTERVENTIONS: Patients received infusions of 30 ng/kg/min of PGE1 or saline. MEASUREMENTS AND MAIN RESULTS: Hemodynamic variables, lactate, creatine phosphokinase, and thromboxane B2 (TXB2) were measured. In the control group, the decrease in cardiac index (CI) after aortic cross-clamping (AXC) persisted until unclamping together with a decrease in femoral venous O2 content (CfvO2). In the PGE1 group, CI returned to baseline with a trend toward greater CfvO2 levels. During reperfusion in the PGE1 group, O2 consumption and lactate levels exceeded preclamp values. Pulmonary hypertension occurred equally in both groups but did not correlate with TXB2, which was not altered by surgery or by PGE1 infusion. CONCLUSIONS: Intraoperative PGE1 treatment offers no benefit and may exacerbate tissue ischemia during AXC by redistributing microcirculatory flow or limiting cellular oxygen utilization in a manner that overwhelms any possible protective effect.

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.

Improved cardiac performance and reduced pulmonary vascular constriction by epinephrine administration via a left atrial catheter in cardiac surgical patients.

Diminished left ventricular contractility and increased right ventricular afterload are issues in cardiac surgery. The usual administration of catecholamines (epinephrine) via the central venous (CV) catheter increases cardiac output, but also may increase pulmonary vascular constriction. Epinephrine was, therefore, administered via the left atrial (LA) catheter or the CV catheter in 8 cardiac surgery patients, each serving as his or her own control. The LA administration of epinephrine has an advantage with its immediate effect on the coronary circulation, while avoiding associated pulmonary vasoconstriction by passing through the systemic capillary bed before reaching the lung. It was found in this study that administration of epinephrine via an LA catheter increased the average cardiac output by 1.05 L/min, which was significantly (P < 0.05) greater than with administration via the CV catheter. With LA administration of epinephrine, systemic arterial pressure (systolic arterial pressure and diastolic arterial pressure) (SAP, DAP) were also elevated to a greater extent than by CV administration. On the other hand, pulmonary arterial pressures (systolic pulmonary arterial pressure and diastolic pulmonary arterial pressure) (SPAP, DPAP) were less elevated than by administration via the CV catheter. This produced increased coronary perfusion and a smaller increase in pulmonary vascular tone by LA administration in contrast to CV administration of epinephrine. It is concluded that epinephrine administration via an LA catheter improved myocardial performance and pulmonary perfusion due to direct entry of the agent into the coronary circulation and partial metabolism while passing through the systemic capillary bed before reaching the lung.