Robert J. Demeter

Comparison of the effects of pindolol and atenolol on hemodynamic function in systemic hypertension

A randomized double-blind study was performed on a group of mild hypertensive patients (WHO class I) to compare the hemodynamic effects of pindolol and atenolol. Blood pressure (BP) was monitored with a mercury gauge sphygmomanometer, while cardiac function and peripheral arterial flows were measured by the noninvasive technique of bioelectric impedance. After a 2-week washout period, patients with a diastolic BP greater than 95 mm Hg but less than 114 mm Hg were randomized into the pindolol (29 patients) or atenolol (28) treatment groups. Patients were treated with 1 of the 2 drugs in an incremental fashion for 12 weeks. Cardiovascular function was measured after the washout period and at the end of the 12-week treatment period. Baseline hemodynamics were similar in both groups. The 2 drugs were equally effective in lowering both systolic and diastolic BP. Hemodynamically, pindolol lowered BP by decreasing total peripheral resistance (-406 +/- 145 dynes.s.cm-5) while atenolol decreased cardiac index (-0.2 +/- 0.1 liters/min/m2) associated with a decrease in heart rate (-12 +/- 2 beats/min). Regarding peripheral vascular beds, pindolol lowered arm vascular resistance (-198 +/- 72 mm Hg/liter/min) and leg vascular resistance (-73 +/- 25 mm Hg/liter/min), especially when subjects who did not respond to pindolol were excluded from the analysis. Both arm (5.5 +/- 5.4% increase above baseline) and leg (1.2 +/- 4.4% increase above baseline) arterial flow indexes were maintained with pindolol. Conversely, atenolol decreased the arm arterial flow index (-9,8 +/- 5.6% decrease below baseline), but not significantly and with no change in resistance (+54 +/- 62 mm Hg/liter/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of noninvasive bioelectric impedance to predict cardiac output in open heart recovery

Cardiac outputs (CO) measured by bioelectric impedance (Z) and thermodilution (TD) were compared in ten stable, non-ventilated male coronary artery bypass patients (mean age 59 +/- 12 years) in an open heart recovery unit. The measurements were obtained blindly in three sequential body positions (supine, 45 degrees, final supine) using either a calculated value for resistivity (p) (based upon hematocrit with blood sampled at the time of the study) to estimate CO(Z), or assumed values of p = 135.5 omega cm and p = 150 omega cm. The results indicate high correlations between the two measurement methods (range: r = 0.97 to 0.99) in the initial supine position for all resistivity conditions followed by a progressive decline when body position was changed to 45 degrees and supine (range: r = 0.74 to 0.90). The highest overall correlations and closest absolute mean cardiac output values were obtained when p was calculated from actual hematocrit values obtained at the time of the study. Applying a two-way ANOVA to assess the simultaneous effects of method (TD vx. Z) and position change (supine, 45 degrees, supine), no significant main effects or interactions were found when cardiac output values were estimated using the calculated measurement of p. However, significant main effects of method were found when p was assumed to be either 135.5 omega cm (p > or = 0.005) or 150.0 omega cm (p > or = 0.0001), with impedance showing a tendency to overestimate cardiac output. In conclusion, our findings suggest that impedance is a valid method to estimate cardiac output in this subpopulation of patients in open heart recovery provided that p is calculated at the time the study is performed.

Use Of Noninvasive Bioelectric Impedance To Predict Cardiac Output After Open Heart Surgery

Ten stable male non-ventilated coronary artery bypass patients (mean age 59 f 12 years) were comparatively studied with thermodilution (T.D.) and bioelectric impedance (Z) 24-48 hrs. post surgery, in the Open Heart Recovery (OHR) Unit. Cardiac outputs (CO) were compared, after blinded measurements were obtained in three sequential positions (supine, 45 degree head-up tilt and supine). (Z) cardiac outputs were compared to (T.D.) using the actual value for resistivity @) of blood (sampled at the time of the study) and assumed values of 135.5 ohm-an and 150 ohm-an. The results indicate high correlations (range = .W to 99) in the initial supine position for all resistivity conditions followed by a progressive dedine when body position is changed to 45 degrees and supine (range = .74 to 30). The highest overall correlations and closest mean CO values were obtained when (p) was measured. Signifcant (p<.02) mean differences between 2 and T.D. were observed when (p) was assumed to be 150 ohm-cm. In this spedic group of patients, impedance CO is highly correlated to T.D. CO with mean values not significantly different when (p) is measured or assumed to be 135.5 ohm-cm, yet absolute mean values are closest when (p) is not assumed.