Monitoring in neuroanaesthesia: update of clinical usefulness.
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Anesthesia↗
Biomedical subjects
J Berré
Publications and source records attributed to J Berré.
Measurement of cerebral blood flow at the bedside.
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Argon↗
Enteral feeding with a solution enriched with antioxidant vitamins A, C, and E enhances the resistance to oxidative stress.
OBJECTIVE: To assess whether dietary supplementation with the antioxidant vitamins A, C, and E enhances parameters of oxidative stress and influences the course of critically ill patients. DESIGN: Prospective, randomized, double-blinded, placebo-controlled study. SETTING: Department of medicosurgical intensive care of an academic hospital. PATIENTS: Fifty-one patients expected to require at least 7 days of enteral feeding. Thirty-seven of these patients (age, 57 +/- 7 yrs; Simplified Acute Physiology Score II, 33 +/- 6 points) completed the study. INTERVENTIONS: Twenty patients were randomized to receive the formula supplemented with vitamins A (67 microg/dL), C (13.3 mg/ dL), and E (4.94 mg/dL), and 17 patients received an isocaloric and isonitrogenous control solution. MEASUREMENTS AND MAIN RESULTS: Plasma levels of antioxidant vitamins, lipid peroxidation (estimated by the malonyldialdehyde assay), and low-density lipoprotein (LDL), and erythrocyte resistance to experimental oxidative stress were determined on samples drawn two consecutive days before the initiation of feeding and at the end of the 7-day period. Clinical outcome measures included documented infection and intensive care unit and 28-day survival. Administration of the supplemented solution increased significantly the concentration of plasma beta-carotene (from 0.2 +/- 0.0 microg/mL to 0.6 +/- 0.1 microg/mL; p < 0.01) and plasma and LDL-bound alpha-tocopherol (from 6.0 +/- 0.4 microg/mL and 2.9 +/- 0.9 microg/mL to 9.7 +/- 0.5 microg/mL and 4.3 +/- 1.2 microg/mL, respectively; p < 0.05), and improved LDL resistance to oxidative stress by 21 +/- 4% (p < 0.05). No such change was observed in the control group. There was no significant difference in clinical outcome between the two groups. CONCLUSIONS: Supplemental antioxidant vitamins added to enteral feeding solutions are well absorbed. Dietary supplementation with vitamins A, C, and E is associated with an improvement in antioxidant defenses, as assessed by ex vivo tests.
APACHE↗
Is cerebral perfusion pressure a major determinant of cerebral blood flow during head elevation in comatose patients with severe intracranial lesions?
OBJECT: Head elevation as a treatment for lower intracranial pressure (ICP) in patients with intracranial hypertension has been challenged in recent years. Therefore, the authors studied the effect of head position on cerebral hemodynamics in patients with severe head injury. METHODS: The effect of 0 degrees, 15 degrees, 30 degrees, and 45 degrees head elevation on ICP, cerebral blood flow (CBF), systemic arterial (PsaMonro) and jugular bulb (Pj) pressures calibrated to the level of the foramen of Monro, cerebral perfusion pressure (CPP), and the arteriovenous pressure gradient (PsaMonro - Pj) was studied in 37 patients who were comatose due to severe intracranial lesions. The CBF decreased gradually with head elevation from 0 to 45 degrees, from 46.3+/-4.8 to 28.7+/-2.3 ml x min(-1) x 100 g(-1) (mean +/- standard error, p<0.01), and the PsaMonro - Pj from 80+/-3 to 73+/-3 mm Hg (p< 0.01). The CPP remained stable between 0 degrees and 30 degrees of head elevation, at 62+/-3 mm Hg, and decreased from 62+/-3 to 57+/-4 mm Hg between 30 degrees and 45 degrees (p<0.05). A simulation showed that the 38% decrease in CBF between 0 degrees and 45 degrees resulted from PsaMonro - Pj changes for 19% of the decrease, from a diversion of the venous drainage from the internal jugular veins to vertebral venous plexus for 15%, and from CPP changes for 4%. CONCLUSIONS: During head elevation the arteriovenous pressure gradient is the major determinant of CBF. The influence of CPP on CBF decreases from 0 to 45 degrees of head elevation.
Adolescent↗
Management of nutrition in European intensive care units: results of a questionnaire. Working Group on Metabolism and Nutrition of the European Society of Intensive Care Medicine.
OBJECTIVE: To describe the practical aspects of nutritional management in intensive care units (ICUs). DESIGN: A 49-item questionnaire was sent to the physician members of the European Society for Intensive Care Medicine. The issues addressed included: medical environment, assessment of nutritional status and current practice for enteral and parenteral nutrition. SETTING: 1608 questionnaires were sent in 35 European countries. ANALYSIS: The answers were pooled and stratified by country. RESULTS: 271 questionnaires were answered (response rate 17%). Assessment of nutritional status was generally based on clinical (99%) and biochemical (82%) parameters rather than on functional (24%), anthropometric (23%), immunological (18%) or questionnaire-based (11%) data. Two thirds of 2774 patients hospitalised in the corresponding ICUs at the time the questionnaire was answered were receiving nutritional support; 58% of those were fed by the enteral route, 23% by the parenteral route and 19% by combined enteral and parenteral. The preferred modality was enteral nutrition, instituted before the 48th h after admission, at a rate based on estimated caloric requirements. Specific and modified solutions were rarely used. Parenteral nutrition was less commonly used than enteral, although the practices differed between countries. It was mainly administered as hospital-made all-in-one solutions, at a rate based on calculated caloric requirements. CONCLUSIONS: European intensivists are concerned by the nutritional management of their patients. The use of nutritional support is common, essentially as early enteral feeding.
Critical Care↗
Induced hypertension after head injury.
The use of induced hypertension in head injury patients is controversial. We present the case of a 19-year-old man admitted with severe head trauma after a road accident and describe the beneficial effects that increasing arterial blood pressure had on the cerebral perfusion pressure, cerebral blood flow and jugular bulb oxygen saturation in this patient.
Adult↗
Cerebral blood flow velocity responses to hypoxia in subjects who are susceptible to high-altitude pulmonary oedema.
Cerebral blood flow increases on exposure to high altitude, and perhaps more so in subjects who develop acute mountain sickness. We determined cerebral blood flow by transcranial Doppler ultrasound of the middle cerebral artery at sea level, in normoxia (fraction of inspired O2, F(I)O2 0.21), and during 15-min periods of either hypoxic (F(I)O2 0.125) or hyperoxic (F(I)O2 1.0) breathing, in 7 subjects with previous high-altitude pulmonary oedema, 6 climbers who had previously tolerated altitudes between 6000 m and 8150 m, and in 20 unselected controls. Hypoxia increased mean middle cerebral artery flow velocity from 69 (3) to 83 (4) cm x s(-1) (P<0.001) in the controls, from 63 (3) to 75 (3) cm x s(-1) (P<0.001) in the high-altitude pulmonary-oedema-susceptible subjects, and from 58 (4) to 70 (4) cm x s(-1) (P<0.001) in the successful high-altitude climbers. Hyperoxia decreased mean middle cerebral flow velocity to 60 (3) cm x s(-1) (P<0.001), 53 (3) cm x s(-1) (P<0.01), and 49 (3) cm x s(-1) (P<0.01) in the controls, high-altitude pulmonary-oedema-susceptible, and high-altitude climbers, respectively. We conclude that a transcranial Doppler-based estimate of cerebral blood flow is affected by hypoxic and hyperoxic breathing, and that it is not predictive of tolerance to high altitude.
Adult↗
The Brussels sedation scale: use of a simple clinical sedation scale can avoid excessive sedation in patients undergoing mechanical ventilation in the intensive care unit.
Sedation is an important component of patient comfort in the intensive care unit (ICU), especially in those undergoing mechanical ventilation. Sedation that is too light or too deep can have important consequences, and therefore assessment of the degree of sedation should be an important part of patient management. Although there are many methods available to assess the degree of sedation, none is ideal. Therefore, we developed a new sedation scale and analysed its clinical impact in the management of patients undergoing mechanical ventilation. The study comprised two consecutive phases. In the first phase, the medical team did not use a sedation scale. In the second phase, the medical staff used the new sedation scale, comprising five levels, depending on the perceived degree of sedation: levels 1 and 2 = oversedation; levels 3 and 4 = correct sedation; and level 5 = undersedation. There were no significant differences in mean or highest levels between patients in the two phases (mean 2.89 (SD 0.11) vs 2.67 (0.13), P = 0.22; highest 3.16 (0.11) vs 3.10 (0.14), P = 0.78). However, the lowest level was significantly greater in patients in the second phase than in those in the first phase (2.61 (0.11) vs 2.16 (0.13); P = 0.011), indicating that the number of patients with excessive sedation was significantly reduced with the introduction of this scale. Thus the use of this scale can have a real clinical impact for patients undergoing mechanical ventilation, principally by avoiding excessive sedation.
Procedural Sedation↗
An evidence-based approach to round tables and consensus conferences.
In current clinical practice, it is important to be able to evaluate the evidence supporting each of our actions. Physicians can no longer rely on tradition or habit; however, with the increasing number of journals available, it is impossible for the practicing clinician to keep abreast of all the relevant literature. One valuable method of gathering and summarizing the latest information and opinions is the use of round tables and consensus conferences. Published reports of round table and consensus conference findings can be invaluable in guiding the clinician.
Consensus Statements as Topic↗
Beta-blocking agents can increase PaO2.
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Adrenergic beta-Antagonists↗
Cerebral CO2 vasoreactivity evaluation with and without changes in intrathoracic pressure in comatose patients.
It is well established that cerebral blood flow (CBF) is sensitive to variations in arterial PCO2 (PaCO2) and can be influenced by changes in jugular venous return due to elevated intrathoracic pressure. Therefore, we compared cerebral CO2 vasoreactivity when PaCO2 was altered either by changing inspired PCO2 or tidal volume. In addition, we sought to determine if noninvasive transcranial Doppler ultrasonography can be used instead of invasive CBF measurement to determine cerebral CO2 vasoreactivity. In 36 mechanically ventilated patients in coma due to acute brain lesion, we evaluated CBF by continuous jugular thermodilution, middle cerebral artery flow velocity (Vm) by transcranial Doppler ultrasonography, intracranial pressure (ICP; in only 23 of them) by intraventricular catheter, systemic and pulmonary hemodynamic variables, and arterial and jugular bulb blood gases. Measurements were taken at four levels of PaCO2 (25, 30, 35, and 40 mmHg) by modifying in a random order either tidal volume or inspired PCO2. Cerebral, pulmonary, and systemic hemodynamic changes were similar in magnitude during both methods of altering PaCO2. From the highest to the lowest PaCO2, CBF decreased from 61+/-7 to 36+/-4 ml/min/100 g (p < 0.001, mean +/- SE), Vm from 89+/-7 to 65+/-5 cm/s (p < 0.001), and ICP from 29+/-2 to 12+/-2 mmHg (p < 0.001), but cerebral perfusion pressure remained constant, ranging from 65+/-3 to 67+/-4 mmHg (p = NS). Arteriojugular oxygen content difference increased from 3.2+/-0.2 to 5.7+/-0.4 ml/dl (p < 0.001). Eleven of the 20 patients with a preserved CBF response to CO2 survived to 6 months, whereas only two of the 16 patients with an altered response were alive at 6 months (p < 0.05). When compared with CBF by jugular thermodilution, the rates of sensitivity and specificity of transcranial Doppler ultrasonography to detect impaired cerebral CO2 vasoreactivity were 69% and 65%, respectively. In conclusion, the reduction of PaCO2 from 40 to 25 mmHg by modifying either tidal volume or inspired PCO2 resulted in similar effects on cerebral, pulmonary, and systemic circulations. Cerebral CO2 vasoreactivity is of prognostic value in brain-injured patients when determined using CBF but may be misleading when evaluated using velocities measured by transcranial Doppler ultrasonography.
Acute Disease↗
Dobutamine increases cerebral blood flow velocity and jugular bulb hemoglobin saturation in septic patients.
OBJECTIVE: To evaluate the effects of dobutamine on cerebral hemodynamics in septic patients with stable hemodynamic status. DESIGN: Open-label, prospective study. SETTING: Multidisciplinary department of intensive care in a university hospital. PATIENTS: Fourteen mechanically ventilated septic patients with altered mental status and stable hemodynamic status. INTERVENTIONS: Dobutamine infusion, in incremental doses of 2 micrograms/kg/min every 10 mins, for < or = 10 micrograms/kg/min. MEASUREMENTS AND MAIN RESULTS: Mean flow velocity in the right middle cerebral artery, as measured by transcranial Doppler, increased from 68 +/- 6 (SEM) cm/sec at baseline to 80 +/- 7 cm/sec (p < .001) with 10 micrograms/kg/min of dobutamine. Cerebral arterial-venous oxygen content difference and cerebral oxygen extraction ratio concurrently decreased from 4.1 +/- 0.2 to 3.4 +/- 0.3 mL/dL (p < .05) and from 46 +/- 3% to 36 +/- 4% (p < .05), respectively. Dobutamine also increased cardiac index from 3.8 +/- 0.3 to 6.3 +/- 0.5 L/min/m2 (p < .001) and systemic oxygen delivery (DO2) from 497 +/- 35 to 817 +/- 55 mL/min/m2. Mean arterial pressure increased slightly from 77 +/- 3 mm Hg to a maximum value of 86 +/- 4 mm Hg (p < .05). Relative changes in mean flow velocity were better correlated with cardiac index (r2 = .52, p < .001) than with arterial pressure (r2 = .20; p < .001). Cerebral DO2 (estimated by the product of mean flow velocity and arterial oxygen content) increased by 12% with dobutamine, whereas estimated cerebral oxygen consumption (VO2) did not. CONCLUSION: These measurements of middle cerebral artery flow velocity and jugular bulb oximetry suggest that dobutamine increases cerebral blood flow but not cerebral VO2 in stable septic patients.
Adult↗
Estimation of cerebral blood flow at bedside by continuous jugular thermodilution.
The Kety-Schmidt technique can be regarded as the reference method for the measurement of cerebral blood flow (CBF). However, the method is somewhat cumbersome for routine use in the intensive care unit (ICU) at the beside. The continuous thermodilution technique developed many years ago for the measurement of coronary sinus blood flow can be applied for the measurement of jugular blood flow (JBF). However, the measurement of JBF by thermodilution has never been validated using the Kety-Schmidt reference method. We first validate the continuous thermodilution in vitro by comparison with a volumetric flow. The thermodilution method is accurate for flows between 50 and 900 ml min-1 with a mean difference volumetric-thermodilution flow of -1 +/- 18 ml min-1 (mean +/- SD), and precise with a coefficient of variability ranging between 1.21% and 2.50%. In vivo accuracy was assessed by comparing in 15 comatose patients CBF measured using the Kety-Schmidt (CBFKS) method and estimated from JBF measured by thermodilution (CBFTH) at four levels of arterial PaCO2 (25, 30, 35, and 40 mm Hg). The mean difference CBFKS-CBFTH is -0.9 +/- 3.6 ml min-1 100 g-1. In vivo precision of the method was good, with a coefficient of variability of 4.1% in mean. We conclude that jugular continuous thermodilution technique is a reliable method for estimating CBF at the bedside. This technique allows repeated measurements jugular bulb blood sampling for brain metabolic studies.
Adult↗
Doppler assessment of hypoxic pulmonary vasoconstriction and susceptibility to high altitude pulmonary oedema.
BACKGROUND: Subjects with previous high altitude pulmonary oedema may have stronger than normal hypoxic pulmonary vasoconstriction. Susceptibility to high altitude pulmonary oedema may be detectable by echo Doppler assessment of the pulmonary vascular reactivity to breathing a hypoxic gas mixture at sea level. METHODS: The study included 20 healthy controls, seven subjects with a previous episode of high altitude pulmonary oedema, and nine who had successfully climbed to altitudes of 6000-8842 m during the 40th anniversary British expedition to Mount Everest. Echo Doppler measurements of pulmonary blood flow acceleration time (AT) and ejection time (ET), and of the peak velocity of the tricuspid regurgitation jet (TR), were obtained under normobaric conditions of normoxia (fraction of inspired oxygen, FIO2, 0.21), of hyperoxia (FIO2 1.0), and of hypoxia (FIO2 0.125). RESULTS: Hypoxia decreased AT/ET by mean (SE) 0.06 (0.01) in the control subjects, by 0.11 (0.01) in those susceptible to high altitude pulmonary oedema, and by 0.02 (0.02) in the successful high altitude climbers. Hypoxia increased TR in the three groups by 0.22 (0.06) (n = 14), 0.56 (0.13) (n = 5), and 0.18 (0.1) (n = 7) m/s, respectively. However, AT/ET and/or TR measurements outside the normal range, defined as mean +/- 2 SD of measurements obtained in the controls under hypoxia, were observed in only two of the subjects susceptible to high altitude pulmonary oedema and in five of the successful high altitude climbers. CONCLUSIONS: Pulmonary vascular reactivity to hypoxia is enhanced in subjects with previous high altitude pulmonary oedema and decreased in successful high altitude climbers. However, echo Doppler estimates of hypoxic pulmonary vaso-constriction at sea level cannot reliably identify subjects susceptible to high altitude pulmonary oedema or successful high altitude climbers from a normal control population.
Adult↗
Effects of dobutamine and prostacyclin on cerebral blood flow velocity in septic patients.
PURPOSE: Both dobutamine and prostacyclin (PGI2) have been used to increase oxygen delivery in septic patients, but their effects on cerebral blood flow have not been well studied. METHODS: In 10 septic patients with altered mental status, stable hemodynamic status, and normal lactatemia, we investigated the effects of successive infusions of dobutamine at 5 micrograms/kg/min and PGI2 at 5 ng/kg/min on mean blood flow velocity in a middle cerebral artery, using transcranial Doppler flowmetry. RESULTS: Mean flow velocity increased with dobutamine (from 52 +/- 4 to 62 +/- 6 cm/s, P < .005) but not with PGI2 (from 55 +/- 5 to 57 +/- 5 cm/s, P = not significant). Each substance significantly increased cardiac index. Dobutamine increased arterial pressure from 85 +/- 6 to 91 +/- 5 mm Hg (P < .05), but PGI2 decreased it from 87 +/- 6 to 77 +/- 5 mm Hg (P < .005). With each agent, mean flow velocity was correlated with cardiac index (r = .51, P < .001) but not with arterial pressure. PGI2 reduced PaO2 from 103 +/- 10 to 82 +/- 6 mm Hg (P < .005). Cerebral oxygen delivery (estimated by the product of mean flow velocity and arterial oxygen content) increased by 19% with dobutamine but remained unchanged with PGI2. CONCLUSIONS: Dobutamine and PGI2 at the administered doses exert different effects on arterial pressure and middle cerebral artery flow velocity in septic patients. According to these data, dobutamine increases cerebral oxygen delivery more than PGI2.
Adult↗
Relationship of middle cerebral artery blood flow velocity to intensity during dynamic exercise in normal subjects.
Cerebral blood flow has been reported to increase during dynamic exercise, but whether this occurs in proportion to the intensity remains unsettled. We measured middle cerebral artery blood flow velocity (vm) by transcranial Doppler ultrasound in 14 healthy young adults, at rest and during dynamic exercise performed on a cycle ergometer at a intensity progressively increasing, by 50 W every 4 min until exhaustion. Arterial blood pressure, heart rate, end-tidal, partial pressure of carbon dioxide (PETCO2), oxygen uptake (VO2) and carbon dioxide output were determined at exercise intensity. Mean vM increased from 53 (SEM 2) cm.s-1 at rest to a maximum of 75 (SEM 4) cm.s-1 at 57% of the maximal attained VO2 (VO2max), and thereafter progressively decreased to 59 (SEM 4) cm.s-1 at VO2max. The respiratory exchange ratio (R) was 0.97 (SEM 0.01) at 57% of VO2max and 1.10 (SEM 0.01) at VO2max. The PETCO2 increased from 5.9 (SEM 0.2) kPa at rest to 7.4 (SEM 0.2) kPa at 57% of VO2max, and thereafter decreased to 5.9 (SEM 0.2) kPa at VO2max. Mean arterial pressure increased from 98 (SEM 1) mmHg (13.1 kPa) at rest to 116 (SEM 1) mmHg (15.5 kPa) at 90% of VO2max, and decreased slightly to 108 (SEM 1) mmHg (14.4 kPa) at VO2max. In all the subjects, the maximal value of vm was recorded at the highest attained exercise intensity below the anaerobic threshold (defined by R greater than 1). We concluded that cerebral blood flow as evaluated by middle cerebral artery flow velocity increased during dynamic exercise as a function of exercise intensity below the anaerobic threshold.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Relationship between oxygen uptake and oxygen delivery in septic patients: effects of prostacyclin versus dobutamine.
OBJECTIVE: To compare the effects of prostacyclin (PGI2) and dobutamine on the relationship between oxygen delivery (DO2) and oxygen uptake (VO2) in stable septic patients. DESIGN: Prospective study using a crossover design with alternate order of medications. PATIENTS: Seventeen patients with documented sepsis and a stable hemodynamic status with normal blood lactate concentrations. Eleven patients were mechanically ventilated. Eight patients eventually died. INTERVENTIONS: DO2 and VO2 were calculated before and after a 20-min infusion of 5 ng/kg/min of PGI2 followed or preceded by 5 micrograms/kg/min of dobutamine. MEASUREMENTS AND MAIN RESULTS: Both medications increased cardiac output significantly. At the dose used, PGI2 infusion reduced mean arterial pressure from 90.8 +/- 16.8 to 81.5 +/- 17.3 mm Hg (p < .01) and PaO2 from 97 +/- 25 torr to 82 +/- 22 torr (from 12.9 +/- 3.3 to 10.9 +/- 2.9 kPa) (p < .01) and increased venous admixture from 17.5 +/- 0.6% to 23.8 +/- 8.2% (p < .01). Dobutamine had no significant influence on these variables. PGI2 increased DO2 by 19% (from 470 +/- 105 to 557 +/- 117 mL/min/m2, p < .01) while dobutamine increased DO2 by 27% (from 463 +/- 103 to 589 +/- 156 mL/min/m2, p < .01). PGI2 increased VO2 by 5% (from 148 +/- 38 to 155 +/- 36 mL/min/m2) while dobutamine increased VO2 by 10% (from 146 +/- 36 to 161 +/- 41 mL/min/m2, p < .01). Accordingly, there was an identical decrease in oxygen extraction with PGI2 (from 32.4 +/- 8.2% to 28.6 +/- 7.1%, p < .01) and dobutamine (from 32.4 +/- 8.3% to 28.5 +/- 7.8%, p < .01). The responses to these medications were similar in survivors and nonsurvivors. CONCLUSIONS: PGI2 and dobutamine at the doses used have similar effects on oxygen extraction in critically ill, septic patients, but dobutamine increases DO2 more consistently and is better tolerated than prostacyclin.
Aged↗
Addition of enoximone to adrenergic agents in the management of severe heart failure.
OBJECTIVE: To assess the hemodynamic effects of the addition of small bolus doses of the phosphodiesterase inhibitor enoximone to adrenergic therapy in patients with severe heart failure. DESIGN: Open label, prospective study. SETTING: Multidisciplinary department of intensive care in a university academic hospital. PATIENTS: Twelve surgical patients after cardiac surgery and ten medical patients with ischemic or dilated cardiomyopathy who had signs of altered tissue perfusion associated with a low cardiac index (less than 2.25 L/min/m2), despite adrenergic therapy. INTERVENTIONS: Small iv bolus doses of 0.25 mg/kg of enoximone. MEASUREMENTS AND MAIN RESULTS: This treatment resulted in significant increases in cardiac index and left ventricular stroke work index without significant changes in heart rate or mean arterial pressure. Furthermore, the effects of half this dose (i.e., 0.125 mg/kg), studied in 11 patients, demonstrated a significant drug-induced increase in mean (+/- SD) cardiac index (from 1.58 +/- 0.29 to 1.84 +/- 0.27 L/min/m2, p less than .01) without change in mean arterial pressure (from 74.5 +/- 12.1 to 76.5 +/- 12.6 mm Hg, nonsignificant). CONCLUSIONS: Direct iv injections of enoximone can significantly increase the cardiac index in critically ill patients treated by adrenergic agents for severe heart failure. The administration of small doses of enoximone is effective and has minimal effect on arterial pressure.
Adult↗