The cardiovascular, pulmonary, and ocular hypotensive effects of 0.2% brimonidine.

OBJECTIVE: To compare the cardiovascular, pulmonary, and ocular hypotensive effects of 0.2% brimonidine tartrate with those of 0.5% timolol maleate, 0.25% betaxolol suspension, and brimonidine vehicle. DESIGN AND PATIENTS: A single-center, double-masked, randomized, crossover study of 24 young, healthy men. INTERVENTIONS: Baseline heart rate, blood pressure, respiratory rate, and intraocular pressure were recorded at hour 0. At hour 2, heart rate, blood pressure, respiratory rate, and forced expiratory volume in 1 second were measured and a 15-minute treadmill test performed. Hour 0 measurements were repeated at hour 4. On four subsequent visits, we instilled one drop of a study medication into each eye after the baseline measurements at hour 0. RESULTS: Timolol reduced resting (-5.3 to -6.5 beats/min, P < or = .004) and exercise-induced heart rate (-4.3 to -13.6 beats/min; P < or = .022) compared with brimonidine, betaxolol suspension, and brimonidine vehicle. At hour 4, brimonidine reduced resting systolic blood pressure compared with all other study medications (-5.2 to -7.3 mm Hg; P < or = .024). Timolol reduced systolic blood pressure during exercise and brimonidine reduced systolic blood pressure during recovery more than betaxolol suspension and brimonidine vehicle (-5.1 to -7.7 mm Hg; P < or = .033; and -5.4 to -6.0 mm Hg; P < or = .002, respectively). Mean respiratory rate and forced expiratory volume in 1 second were not significantly altered by any study medication. At hour 4, brimonidine lowered intraocular pressure as well as timolol and better than betaxolol suspension (-1.9 mm Hg; P < .001) or brimonidine vehicle (-1.8 mm Hg; P < .001). CONCLUSIONS: The cardiopulmonary effects of 0.2% brimonidine were limited to a slight reduction in systolic blood pressure during recovery from exercise and at 4 hours after instillation. The ocular hypotensive effect of brimonidine was comparable to that of timolol and greater than that of betaxolol suspension in this patient population.

Cardiovascular and intraocular pressure effects and plasma concentrations of apraclonidine.

We performed a double-masked, crossover study comparing the cardiovascular and intraocular pressure effects of 0.5% and 0.25% topical apraclonidine hydrochloride and 0.5% timolol maleate in 20 healthy female volunteers. The contralateral effects of unilateral apraclonidine and the plasma concentrations of apraclonidine were also assessed. All measurements were done 2, 5, and 8 hours after drop instillation. A 15-minute treadmill test was performed after the 2-hour measurements. All three active medications lowered intraocular pressure comparably. There was no significant contralateral intraocular pressure effect seen with apraclonidine. The apraclonidine plasma concentrations were variable and unrelated to the amount of intraocular pressure lowering and cardiovascular parameters measured. Apraclonidine did not affect blood pressure or heart rate any differently than placebo. Timolol, however, blunted exercise-induced tachycardia. There were no significant differences in pupillary diameters or interpalpebral fissure widths among treatment groups.

External cardiac compression. A randomized comparison of mechanical and manual techniques.

To compare the effectiveness of manual and mechanical chest compression during cardiopulmonary resuscitation, 50 patients who suffered cardiac arrest were randomly allocated to receive manual or mechanical chest compression. Randomization was performed after failure of initial resuscitative measures but within ten minutes after the onset of cardiac arrest (mean, 6.4 +/- 1.2 min). Ten patients from each group survived longer than one hour following resuscitation. Three from the mechanical group and two from the manual group were eventually able to leave the hospital. Thus mechanical compression appears comparable with manual compression when manual compression is performed under ideal conditions. Mechanical chest compression may be employed when trained personnel are not readily available or where manual compression is technically difficult to perform.