Blood flow acceleration in the carotid and brachial arteries of healthy volunteers: respective contributions of cardiac performance and local resistance

Summary— The influence of local resistance and cardiac performance on peripheral blood acceleration was investigated in 14 healthy male volunteers. Steady and pulsatile flow was studied in the brachial and in the common carotid arteries, ie, two territories that exhibit marked differences in resistive characteristics. Instantaneous blood velocity (V), mean blood velocity (V_m) and artery diameter (D) were evaluated at rest by an ultrasonic range-gated pulsed Doppler flowmeter using a double transducer probe, thus allowing the calculation of mean blood flow (Q). Mean local resistance (R) was obtained by dividing the mean arterial pressure by Q. The peak value of the local acceleration of the blood was obtained by computer-assisted calculation of the first derivative of instantaneous blood velocity (G_max = +dV/dt_max). Peak aortic blood acceleration (GAo) was simultaneously measured from the suprasternal notch using a pulsed Doppler velocity meter. In the brachial and the common carotid arteries, G_max was of a similar magnitude (551 ±30 and 555 ± 44 cm/s², respectively) despite major differences in the respective D, V_m, Q and R values. In neither artery was there a relationship between G_max and either resting Q or R. At the brachial artery level, G_max was positively related to GAo ( r = 0.79, P = 0.0008). At the common carotid artery level, there was a weak, although non significant relationship between G_max and GAo ( P = 0.08). Our results indicate that the local acceleration of peripheral blood flow in the brachial artery is related rather to upstream central impulse than to downstream hemodynamics, and suggest some regional differences in the hemodynamic determinants of the local acceleration of peripheral blood flow.     

Effects of an angiotensin converting enzyme inhibitor, ramipril, on intracranial circulation in healthy volunteers. off.

1. The effects of a single oral dose (10 mg) of ramipril on (a) systemic haemodynamics (arterial pressure, cardiac output), (b) carotid artery haemodynamics (blood flow and diameter, pulsed Doppler technique), (c) intracranial haemodynamics (middle cerebral artery mean blood velocity, transcranial Doppler technique), and (d) renin-angiotensin system (plasma converting enzyme and renin activities) have been investigated and compared with those of a placebo during the 24 h period following administration in a randomized, double-blind and cross-over study performed in six healthy volunteers. 2. Ramipril induced a strong and sustained inhibition of plasma converting enzyme activity (-96% at 4 h, -63% at 24 h) and an increase in plasma renin activity (+993% at 8 h). 3. As compared with placebo, ramipril did not significantly affect arterial blood pressure, heart rate, cardiac output and total peripheral resistance. 4. Ramipril significantly increased carotid blood flow (by 27% at 8 h) without significantly changing carotid artery diameter, indicating, given the unchanged arterial pressure, an arteriolar vasodilation in the carotid territory. 5. The middle cerebral artery mean blood flow velocity underwent spontaneous modifications during the placebo period but these changes were not affected by ramipril. This lack of influence of ramipril on intracranial haemodynamics suggests that the drug-induced arteriolar vasodilation and increase in carotid blood flow only concern the extracranial, musculo-cutaneous part of the carotid territory.     

A 3-level prognostic classification in septic shock based on cortisol levels and cortisol response to corticotropin

CONTEXT: The hypothalamic-pituitary-adrenal axis is a major determinant of the host response to stress. The relationship between its activation and patient outcome is not known. OBJECTIVE: To evaluate the prognostic value of cortisol levels and a short corticotropin stimulation test in patients with septic shock. DESIGN AND SETTING: Prospective inception cohort study conducted between October 1991 and September 1995 in 2 teaching hospital adult intensive care units in France. PARTICIPANTS: A total of 189 consecutive patients who met clinical criteria for septic shock. INTERVENTION: A short corticotropin stimulation test was performed in all patients by intravenously injecting 0.25 mg of tetracosactrin; blood samples were taken immediately before the test (T0) and 30 (T30) and 60 (T60) minutes afterward. MAIN OUTCOME MEASURES: Twenty-eight-day mortality as a function of variables collected at the onset of septic shock, including cortisol levels before the corticotropin test and the cortisol response to corticotropin (delta max, defined as the difference between T0 and the highest value between T30 and T60). RESULTS: The 28-day mortality was 58% (95% confidence interval [CI], 51%-65%) and median time to death was 17 days (95% CI, 14-27 days). In multivariate analysis, independent predictors of death (P < or = .001 for all) were McCabe score greater than 0, organ system failure score greater than 2, arterial lactate level greater than 2.8 mmol/L, ratio of PaO2 to fraction of inspired oxygen no more than 160 mm Hg, cortisol level at T0 greater than 34 microg/dL and delta max no more than 9 microg/dL. Three groups of patient prognoses were identified: good (cortisol level at T0 < or = 34 microg/dL and delta max > 9 microg/dL; 28-day mortality rate, 26%), intermediate (cortisol level at T0 34 microg/dL and delta max < or = 9 microg/dL or cortisol level at T0 > 34 microg/dL and delta max > 9 microg/dL; 28-day mortality rate, 67%), and poor (cortisol level at T0 > 34 microg/dL and delta max < or = 9 microg/dL; 28-day mortality rate, 82%). CONCLUSION: Our data suggest that a short corticotropin test has a good prognostic value and could be helpful in identifying patients with septic shock at high risk for death.     

The value of a second transurethral resection in evaluating patients with bladder tumours

OBJECTIVES: To evaluate the usefulness of a second transurethral resection for superficial and muscle-invasive bladder tumours. METHODS: A review of the literature relevant to repeat resection for bladder tumours was conducted using Medline Services. RESULTS: Transurethral resection of the bladder has two shortcomings: underestimating clinical stage, and overlooking other lesions. A second transurethral resection, when performed 2-6 weeks after the initial resection, corrects clinical staging errors in 9-49% of cases and detects residual tumour in 26-83% of cases. A second resection is particularly warranted for T1 tumours since 2-28% of them prove to be muscle-invasive, thus requiring a change in management. For muscle-invasive tumours, a second resection may be performed only if bladder sparing is being considered, as it helps to exclude the presence of tumour sites contra-indicating conservative treatment. CONCLUSIONS: A second transurethral bladder resection may be warranted for T1 tumours, and for invasive tumours when a bladder preservation is planned.     

Glucocorticoids and sepsis

Although systemic inflammation is the hallmark of sepsis, the use of glucocorticoids remained controversial during many years. Gluco-corticoids exert key actions during sepsis, interacting with metabolism, immune and cardiovascular systems. Glucocorticoid insufficiency is common during sepsis and may result from insufficient production of cortisol or peripheral tissues resistance. Thus, recent randomised trials showed that a replacement therapy with long course of low dose corticosteroids reduced mortality from septic shock. Improvement in survival may result from reduced duration of shock, alleviation of the systemic inflammatory response, and reduction in the number and intensity of organs dysfunction. This article summarises why, when and how glucocorticoids should be used in the management of septic shock.     

Cardiovascular response to dopamine and early prediction of outcome in septic shock: a prospective multiple-center study

OBJECTIVES: To compare mortality rates between dopamine-sensitive (Dopa-S) and dopamine-resistant (Dopa-R) septic shock patients, the latter group defined by a mean arterial pressure <70 mm Hg despite the use of 20 mug/kg/min dopamine. DESIGN: A human, prospective observational, multiple-center, clinical trial. SETTING: Ten intensive care units from ten hospitals. PATIENTS: 110 patients with septic shocks. INTERVENTIONS: Following volume resuscitation, patients were treated by a rapid increase in dopamine infusion from 10 to 20 mug/kg/min. If mean arterial pressure remained <70 mm Hg, dopamine treatment was promptly switched to norepinephrine or epinephrine. MEASUREMENTS AND MAIN RESULTS: Dopamine sensitivity, arterial gas, lactate, and organ system failure scores were measured at admission and after 6, 12, 24, 48, 72, 96, and 120 hrs. The overall 28-day mortality rate was 54% for the entire population under study. In multivariate analysis, independent predictors of death were dopamine resistance (odds ratio, 9.5; 95% confidence interval, 3-25), arterial lactate >3.5 mmol/L (odds ratio, 1.75; 95% confidence interval, 1.06-2.55), and Sepsis-related Organ Failure Assessment score >10 (odds ratio, 1.40; 95% confidence interval, 1.07-2.12). Of the 110 patients studied, 66 were observed to be resistant to dopamine (60%). In the Dopa-S group, the 28-day mortality rate was 16% (seven of 44 patients) compared with 78% (52 of 66 patients) in the Dopa-R group (p = .0006). The capacity of dopamine resistance to predict death was associated with a sensitivity of 84% and a specificity of 74%. At 24 hrs, the association of dopamine resistance to a lactate level >3.5 mmol/L improved the prognostic value (sensitivity, 90%, specificity, 92%). CONCLUSIONS: Dopamine sensitivity is associated with decreased mortality rate. Early recognition of dopamine resistant septic shock could allow for better screening of patients with an ominous prognosis.