Sally Snader

Johns Hopkins Medicine, Baltimore, Maryland, United States

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Publications (6)48.04 Total impact

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    ABSTRACT: During head-up tilt (HUT), patients with chronic fatigue syndrome (CFS) have higher rates of neurally mediated hypotension (NMH) and postural tachycardia syndrome (POTS) than healthy controls. The authors studied whether patients with CFS were also more likely to have abnormal cerebral blood flow velocity (CBFV) compared with controls in response to orthostatic stress. Transcranial Doppler monitoring of middle cerebral artery (MCA) CBFV was performed during 3-stage HUT prospectively in 26 patients with CFS and 23 healthy controls. At the same time, continuous monitoring of arterial blood pressure (BP), heart rate (HR), endtidal CO2 (ET-CO2) were performed. Results are reported as mean +/- SD. NMH developed in 21 patients with CFS and in 14 controls (P = .22). POTS was present in 9 CFS patients and 7 controls (P = .76). Supine HR was higher in CFS patients, but all other hemodynamics and CBFV measures were similar at baseline. The median time to hypotension did not differ, but the median time to onset of orthostatic symptoms was shorter in those with CFS (P < .001). The CBFV did not differ between groups in the supine posture, at 1 or 5 minutes after upright tilt, at 5 or 1 minute before the end of the test, or at termination of the test. Mean CBFV fell at termination of tilt testing in those with CFS and controls. ET-CO2 was lower at termination of the test in those with CFS versus controls (P = .002). The results of this study are not consistent with the hypothesis that patients with CFS have a distinctive pattern of MCA CBFV changes in response to orthostatic stress.
    Journal of Neuroimaging 01/2003; 13(1):57-67. DOI:10.1177/1051228402239719 · 1.82 Impact Factor
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    ABSTRACT: Neurocardiogenic syncope is the most common cause of acute loss of consciousness in adults. The present study attempted to identify neuroendocrine and hemodynamic changes before syncope that could therefore play a pathophysiologic role. Twenty-five patients referred for chronic orthostatic intolerance had plasma catecholamines measured serially; 21 patients during tilt-table testing (evoking syncope in 13) and 4 others with spontaneous syncope while supine. Forearm blood flow was measured by impedance plethysmography. All 12 patients with blood sampled before tilt-induced syncope had progressive, marked increases in plasma epinephrine levels (mean 11 times baseline, p <0.0001) before syncope. Simultaneously obtained norepinephrine levels increased to a much smaller extent than did epinephrine levels ("sympathoadrenal imbalance"). In the same patients, forearm vascular resistance decreased by 21% before syncope. Proportionate changes in forearm vascular resistance before syncope correlated negatively with those in the epinephrine:norepinephrine ratio (r = -0.75, p = 0.005). Patients without syncope had forearm vasoconstriction and no sympathoadrenal imbalance during tilt. Patients with syncope while supine also had sympathoadrenal imbalance before loss of consciousness. Sympathoadrenal imbalance precedes tilt-evoked and spontaneous neurocardiogenic syncope and correlates with concurrent skeletal muscle vasodilation. Sympathoadrenal imbalance may contribute to hemodynamic derangements precipitating neurocardiogenic syncope.
    The American Journal of Cardiology 01/2003; 91(1):53-8. DOI:10.1016/S0002-9149(02)02997-1 · 3.43 Impact Factor
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    ABSTRACT: Background and Purpose. During head-up tilt (HUT), patients with chronic fatigue syndrome (CFS) have higher rates of neurally mediated hypotension (NMH) and postural tachycardia syndrome (POTS) than healthy controls. The authors studied whether patients with CFS were also more likely to have abnormal cerebral blood flow velocity (CBFV) compared with controls in response to orthostatic stress. Methods. Transcranial Doppler monitoring of middle cerebral artery (MCA) CBFV was performed during 3-stage HUT prospectively in 26 patients with CFS and 23 healthy controls. At the same time, continuous monitoring of arterial blood pressure (BP), heart rate (HR), end-tidal CO2 (ET-CO2) were performed. Results are reported as mean ± SD. Results. NMH developed in 21 patients with CFS and in 14 controls (P = .22). POTS was present in 9 CFS patients and 7 controls (P = .76). Supine HR was higher in CFS patients, but all other hemodynamics and CBFV measures were similar at baseline. The median time to hypotension did not differ, but the median time to onset of orthostatic symptoms was shorter in those with CFS (P < .001). The CBFV did not differ between groups in the supine posture, at 1 or 5 minutes after upright tilt, at 5 or 1 minute before the end of the test, or at termination of the test. Mean CBFV fell at termination of tilt testing in those with CFS and controls. ET-CO2 was lower at termination of the test in those with CFS versus controls (P = .002). Conclusions. The results of this study are not consistent with the hypothesis that patients with CFS have a distinctive pattern of MCA CBFV changes in response to orthostatic stress.
    Journal of neuroimaging: official journal of the American Society of Neuroimaging 12/2002; 13(1):57 - 67. DOI:10.1111/j.1552-6569.2003.tb00158.x · 1.82 Impact Factor
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    ABSTRACT: Patients with chronic fatigue syndrome (CFS) are more likely than healthy persons to develop neurally mediated hypotension (NMH) in response to prolonged orthostatic stress. To examine the efficacy of fludrocortisone acetate as monotherapy for adults with both CFS and NMH. Randomized, double-blind, placebo-controlled trial conducted between March 1996 and February 1999. Two tertiary referral centers in the United States. One hundred individuals aged 18 to 50 years who satisfied Centers for Disease Control and Prevention criteria for CFS and had NMH provoked during a 2-stage tilt-table test. Eighty-three subjects had adequate outcome data to assess efficacy. Subjects were randomly assigned to receive fludrocortisone acetate, titrated to 0.1 mg/d (n = 50) or matching placebo (n = 50) for 9 weeks, followed by 2 weeks of observation after discontinuation of therapy. Proportion of subjects in each group with at least a 15-point improvement on a 100-point global wellness scale. Baseline demographic and illness characteristics between the groups were similar; CFS had been present for at least 3 years in 71%. Using an intention-to-treat analysis, 7 subjects (14%) treated with fludrocortisone experienced at least a 15-point improvement in their wellness scores compared with 5 (10%) among placebo recipients (P =.76). No differences were observed in several other symptom scores or in the proportion with normal follow-up tilt test results at the end of the treatment period. In our study of adults with CFS, fludrocortisone as monotherapy for NMH was no more efficacious than placebo for amelioration of symptoms. Failure to identify symptomatic improvement with fludrocortisone does not disprove the hypothesis that NMH could be contributing to some of the symptoms of CFS. Further studies are needed to determine whether other medications or combination therapy are more effective in treating orthostatic intolerance in patients with CFS.
    JAMA The Journal of the American Medical Association 02/2001; 285(1):52-9. DOI:10.1001/jama.285.1.52 · 30.39 Impact Factor
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    ABSTRACT: To determine the immunogenicity and safety of heptavalent pneumococcal polysaccharide vaccine (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F) conjugated to CRM(197) (7-valent conjugate pneumococcal vaccine [7VPnC]) among infants with sickle cell disease (SCD) and a comparison group of infants without SCD (non-SCD). Two cohorts of infants were enrolled and received open-label doses of 7VPnC vaccine; infants enrolled before 2 months of age received 7VPnC vaccine at 2, 4, and 6 months of age followed by 23-valent pneumococcal polysaccharide vaccine (PS-23) at 24 months of age for those infants with SCD (schedule A), and infants enrolled between 2 and 12 months of age received 7VPnC at 12 months of age followed by PS-23 at 24 months of age for infants with SCD (schedule B). Safety data were collected for 3 days after each dose of vaccine. Antibody concentrations were measured to each of the 7VPnC serotypes by enzyme-linked immunosorbent assay before each vaccine dose and 1 month after the last 7VPnC dose and the PS-23 vaccine dose. Forty-five infants (34 SCD and 11 non-SCD) were vaccinated according to schedule A and 16 infants (13 SCD and 3 non-SCD) according to schedule B. The 7VPnC vaccine was highly immunogenic for all serotypes among infants with and without SCD who received 3 doses of vaccine according to schedule A: depending on serotype, 89% to 100% achieved antibody concentrations above.15 microg/mL and 56% to 100% achieved antibody concentrations above 1.0 microg/mL. Among infants immunized according to schedule B, a single dose of 7VPnC vaccine resulted in antibody concentrations above.15 microg/mL in 53% to 92% by serotype and above 1.0 microg/mL in 31% to 71% by serotype. A single dose of PS-23 resulted in dramatic increases in the antibody concentrations to all serotypes regardless of 1- or 3-dose priming. There was no difference in the reactogenicity of the 7VPnC vaccine between those with and without SCD. There were no serious reactions to the 7VPnC or PS-23 vaccines, even among those with high antibody concentrations before immunization. Infants with SCD respond to 7VPnC vaccine with antibody concentrations that are at least as high as infants without SCD. Infants immunized with 7VPnC vaccine at 2, 4, and 6 months of age developed antibody concentrations in the same range as those achieved among infants without SCD enrolled in a large trial that demonstrated vaccine efficacy against invasive disease. Significant rises were seen in antibody concentrations to all 7VPnC serotypes after the PS-23 booster in children receiving schedule A or B.
    PEDIATRICS 12/2000; 106(5):965-72. · 5.30 Impact Factor
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    ABSTRACT: Objectives. To determine the immunogenicity and safety of heptavalent pneumococcal polysaccharide vaccine (serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F) conjugated to CRM197 (7-valent conjugate pneumococcal vaccine [7VPnC]) among infants with sickle cell disease (SCD) and a comparison group of infants without SCD (non-SCD). Design. Two cohorts of infants were enrolled and received open-label doses of 7VPnC vaccine; infants enrolled before 2 months of age received 7VPnC vaccine at 2, 4, and 6 months of age followed by 23-valent pneumococcal polysaccharide vaccine (PS-23) at 24 months of age for those infants with SCD (schedule A), and infants enrolled between 2 and 12 months of age received 7VPnC at 12 months of age followed by PS-23 at 24 months of age for infants with SCD (schedule B). Safety data were collected for 3 days after each dose of vaccine. Antibody concentrations were measured to each of the 7VPnC serotypes by enzyme-linked immunosorbent assay before each vaccine dose and 1 month after the last 7VPnC dose and the PS-23 vaccine dose. Results. Forty-five infants (34 SCD and 11 non-SCD) were vaccinated according to schedule A and 16 infants (13 SCD and 3 non-SCD) according to schedule B. The 7VPnC vaccine was highly immunogenic for all serotypes among: infants with and without SCD who received 3 doses of vaccine according to schedule A: depending on serotype, 89% to 100% achieved antibody concentrations above .15 mug/mL and 56% to 100% achieved antibody concentrations above 1.0 mug/mL. Among infants immunized according to schedule B, a single dose of 7VPnC vaccine resulted in antibody concentrations above .15 mug/mL in 53% to 92% by serotype and above 1.0 mug/mL in 31% to 71% by serotype. A single dose of PS-23 resulted in dramatic increases in the antibody concentrations to all serotypes regardless of 1- or 9-dose priming. There was no difference in the reactogenicity of the 7VPnC vaccine between those with and without SCD. There were no serious reactions to the 7VPnC or PS-23 vaccines, even among those with high antibody concentrations before immunization. Conclusions. Infants with SCD respond to 7VPnC vaccine with antibody concentrations that are at least as high as infants without SCD. Infants immunized with 7VPnC vaccine at 2, 4, and 6 months of age developed antibody concentrations in the same range as those achieved among infants without SCD enrolled in a large trial that demonstrated vaccine efficacy against invasive disease. Significant rises were seen in antibody concentrations to all 7VPnC serotypes after the PS-23 booster in children receiving: schedule A or B.
    Pediatrics 11/2000; 106(5):965-972. DOI:10.1542/peds.106.5.965 · 5.30 Impact Factor