SEARCH · PubMed Health

Results for “phenylephrine”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

PubMedDate not supplied

Combination cyclopentolate and phenylephrine for mydriasis in premature infants with heavily pigmented irides.

PURPOSE: This study examined whether safe and effective mydriasis can be achieved in premature infants with heavily pigmented irides using combination cyclopentolate 0.2% and phenylephrine 1% eyedrops. METHODS: A prospective, randomized double-blind study was performed to compare combination cyclopentolate 0.2% and phenylephrine 1% eye-drops with triple instillation of tropicamide 0.5% and phenylephrine 2.5%. Twenty-eight consecutive babies with dark irides and birthweight <1600 g referred for screening for retinopathy of prematurity comprised the study population. Infants' eyes were randomly dilated twice with both regimens within a 2-week period. Blood pressure, heart rate, and pupil size were measured. RESULTS: Good mydriasis was achieved in both groups with no significant differences in pupil size or blood pressure (systolic, diastolic, or mean arterial pressures) over starting baseline values. Pulse rates decelerated below the baseline values in both groups, but these differences were not large. CONCLUSION: The single combination eyedrop of cyclopentolate 0.2% and phenylephrine 1% is as effective and safe a mydriatic for infants with dark irides as both tropicamide 0.5% and phenylephrine 2.5%.

Cyclopentolate↗

PubMed2004

Randomized double-blind study of phenylephrine 2.5% vs 10% on pupillary dilation.

PURPOSE: To compare the efficacy of phenylephrine 2.5% versus 10% on pupillary dilation, and also compare their side-effects. METHOD: Patients at the Eye Clinic Srinagarind Hospital were randomized into two groups. Patients in group 1 received 1% tropicamide and 10% phenylephrine, whereas those in group 2 received 1% tropicamide and 2.5% phenylephrine. Pupil diameter, blood pressure and heart rate were measured before and after eyedrop instillation. RESULTS: Five hundred and sixty four patients were randomized into 293 patients (group 1) and 271 patients (group 2), using simple random sampling method. Mean pupil diameters before instillation in group 1 were 4.43 +/- 1.13 mm in the right eye and 4.31 +/- 0.95 mm in the left eye, whereas those in group 2 were 4.45 +/- 1.0 mm in the right eye and 4.32 +/- 0.92 mm in the left eye. After the instillation, the mean pupil diameters in group 1 were 7.58 +/- 0.96 mm in the right eye and 7.60 +/- 1.03 mm in the left eye, whereas those in group 2 were 7.17 +/- 1.04 mm in the right eye and 7.07 +/- 1.06 mm in the left eye. The difference was statistically significant (P < 0.05). There was no significant difference in mean systolic and diastolic blood pressure after instillation between the two groups. However, the mean heart rate after instillation in group 1 was greater than the value in group 2 with statistically significant difference. CONCLUSION: Pupillary dilation with 1% tropicamide and 10% phenylephrine is more effective than 1% tropicamide and 2.5% phenylephrine with statistically significant difference. After single dose instillation, there was no significant difference in the mean blood pressure between the two groups.

Adolescent↗

PubMed1977

Influence of phenylephrine on levels of cyclic 3',5'-AMP in the heart of rats in vivo.

In the course of an investigation into the mode of action of phenylephrine using the radioimmunoisotope method, its influence on levels of cyclic 3'5'-AMP in the heart of rats was studied. Phenylephrine in the dose of 1 microgram/kg/min after five minutes lowered levels of this nucleotide by about 20%. Phenylephrine also inhibited the influence of theophyline, an inhibitor of phosphodiesterase which raises levels of c-AMP. The results suggest that the drop in c-AMP after phenylephrine is connected with lowered activity of adenyl cyclase, but do not exclude the possiblity of an interaction between theophylline and phenylephrine acting on phosphodiesterase, which could be referred to the observed effect.

Animals↗

PubMed1989

Topical phenylephrine for mydriasis affects rabbit retinal pigment epithelial transport.

Rabbit retinal pigment epithelium (RPE) has an alpha-1 adrenoreceptor that substantially reduces RPE short circuit current (Isc) when stimulated. Since phenylephrine is a potent alpha adrenergic agonist frequently used to obtain pupil dilation, we examined the effect of topically applied phenylephrine for pupil dilation on RPE transport. Naive black dutch-belted rabbits received either one drop of 10% phenylephrine applied at t = 0 and t = 30 min or one drop of 1% cyclopentolate applied at t = 30 min. At t = 50 min, RPE-choroid-sclera explants from these animals were sealed in an Ussing chamber. At t = 60-70 min, 1.4 X 10(-4) M epinephrine was introduced into both sides of the Ussing chamber. The change in Isc produced by epinephrine was measured. The Isc reduction in rabbits receiving phenylephrine was 26% (+/- 5% SD, n = 6). The Isc reduction in rabbits receiving cyclopentolate was 39% (+/- 6% SD, n = 5). These values are significantly different (P less than 0.02, student two-tail t-test). These results indicate that topical phenylephrine reached the RPE in vivo and prestimulated the alpha-1 adrenoreceptors.

Administration, Topical↗

PubMed1979

Effects of phenylephrine on transmural distribution of myocardial blood flow in regions supplied by normal and collateral arteries during cardiopulmonary bypass.

Cardiopulmonary bypass is frequently accompanied by decreased peripheral vascular resistance with resultant hypotension that is unresponsive to increased flow rates. Alpha adrenergic agonists are routinely used to increase peripheral vascular resistance and augment blood pressure. In this study, the effects of the alpha adrenergic stimulant phenylephrine on blood flow distribution during cardiopulmonary bypass in myocardium supplied by normal and collateral arteries were studied in eight mongrel dogs. Microsphere determinations of blood flow were made following augmentation of perfusion pressure with phenylephrine and were compared with intraoperative normotensive and hypotensive control levels. With systemic flow rates held constant, phenylephrine was infused in doses adequate to raise perfusion pressure to normotensive levels following hypotension. In the normal region (NR), blood flow was returned to normotensive control levels with flow favoring the subendocardium. In the region supplied by collateral vessels (CR), however, phenylephrine infusion failed to return flow to the normotensive control level in the subendocardial layer, and the flow imbalance present during hypotension was not corrected. An analogue model of the calculable resistances in the CR is presented, which indicates that phenylephrine increased resistance in the collateral vessels. Associated with this inflow restriction is decreased resistance or vasodilatation of the intramyocardial vessels supplied by collateral coronary arteries.

Animals↗

PubMedDate not supplied

A mechanism of action of phenylephrine on heart.

Phenylephrine exerted a positive chronotropic and inotropic effect on isolated, spontaneously beating, atria of reserpinised rabbits. Addition of phenoxybenzamine and phentolamine resulted in a depression of control contractile amplitude. Practolol, however, was devoid of this effect. The positive inotropic response to phenylephrine was significantly antagonised by all the three blockers used, while positive chronotropic response was annulled by phentolamine and practolol, but not with phenoxybenzamine. It is, therefore, suggested that phenylephrine exerts its cardiostimulant effects through mediation of both alpha and beta-1 adrenoceptors. A probable mechanism of action could be, that phenylephrine acts on some specific chemical group, shared by alpha and beta1 receptors. This specific group is probably blocked by both alpha and betaceptor antagonists separately, so phenylephrine becomes ineffective in presence of these antagonists.

Animals↗

PubMed1980

Comparison of the alpha-adrenergic agonists, phenylephrine and methoxamine in rabbit papillary muscles.

The positive inotropic effects of the alpha-adrenergic agonists, phenylephrine and methoxamine were compared in isolated rabbit papillary muscles. Phenylephrine in the presence of 10(-7)M propranolol produced a greater response than methoxamine. Antagonism by phentolamine was competitive for phenylephrine and apparently, noncompetitive for methoxamine. Based upon observed maximum following frequencies, 10(-4)M methoxamine had a greater cardiac depressant effect than 10(-4) phenylephrine. It was suggested that phenylephrine with a beta-adrenergic antagonist possessed advantages over methoxamine as an agonist for studying cardiac alpha-adrenergic receptors in rabbit papillary muscles.

Animals↗

PubMed1983

Antagonism and supersensitivity to phenylephrine-induced chronotropic responses.

Right atria from rats were analyzed for chronotropic responses to phenylephrine in face of various drugs and procedures. Propranolol, 10(-8) M, produced a competitive antagonism against the agonist which concentration-effect curve was closely similar to that obtained from reserpinized animals. Prazosin, but not phentolamine (both 10(-6) M) showed inhibition of the phenylephrine-induced changes in heart rate, as judged by their -log EC50. Either of the alpha-adrenoceptor antagonists exhibited a greater steepness in the curve slope with respect to control. The simultaneous exposure of tissues to phentolamine and propranolol proved to effectively antagonize the chronotropic effect of the agonist. This held true for phentolamine assayed in atria from reserpine-pretreated rats. Previous incubation of tissues with papaverine, 10(-5) M, brought about supersensitivity to phenylephrine which was thoroughly inhibited by either phentolamine or propranolol. These results strongly suggest that beta-adrenoceptor stimulation of heart rate by phenylephrine takes place indirectly via norepinephrine release. There is also alpha 1-adrenoceptor stimulation (blocked by prazosin). Finally, it is hypothesized that supersensitivity develops by papaverine-enhanced Ca2+ influx, since numerous evidences are against a phosphodiesterase inhibition-dependent cAMP accumulation mechanism triggered by papaverine in the presence of phenylephrine.

Animals↗

PubMedDate not supplied

Interactions between sympathomimetic agonists and blocking agents: cardiac effects of phenylephrine and isoproterenol.

In the isolated rat atria the effects of phenylephrine (alpha-agonist) and isoproterenol (beta-agonist) on the contractile force and heart rate were studied either in presence or not of alpha- and/or beta-blockade. Phentolamine 10(-6) M and propranolol 10(-8) M were used as alpha- and beta-antagonists, respectively. The chronotropic dose-response curves were made in both spontaneously beating atria while inotropic effects were derived from left atria driven at 1 Hz, 5 msec and voltage about 20 percent above threshold. Both agonists induced an inotropic effect that could be significantly blocked by phentolamine, propranolol and both antagonists given together. The chronotropic dose-response curve of isoproterenol (pD2 = 10.70 +/- 0.11) was blocked by phentolamine (pD2 = 9.27 +/- 0.08, p less than 0.001) and propranolol (pD2 = 9.21 +/- 0.19, p less than 0.001). Contrarily, pentolamine was unable to shift to the right the chronotropic dose-response curve for phenylephrine (pD2 = 6.48 +/- 0.07 and 6.63 +/- 0.10, respectively). This action of phenylephrine on the heart rate was significantly blocked by propranolol (pD2 = 6.21 +/- 0.13, p less than 0.05) and by propranolol plus phentolamine (pD2 = 6.07 +/- 0.04, p less than 0.001). From the present results it is concluded that in the rat's atrial myocardium there exist alpha- and beta-adrenoceptors mediating the positive inotropic effect of isoproterenol and phenylephrine. Yet, the chronotropic action seems to behave in a different way: while isoproterenol triggered either type of receptors; phenylephrine is only mediated by beta-adrenoceptors.U

Animals↗

PubMed1994

Effect of phenylephrine on hemodynamics and splenic dimensions in horses.

Pharmacologically induced splenic contraction might be useful during certain medical or surgical procedures in horses. The effects of phenylephrine, an alpha 1-adrenergic receptor agonist, on hemodynamic function and splenic dimensions were examined in 6 healthy adult horses. Phenylephrine infusion (1, 3, or 6 micrograms/kg of body weight/min for 15 minutes) resulted in a dose-related increase in mean pulmonary artery pressure; right atrial pressure; systolic, mean, and diastolic arterial pressures; and packed cell volume (P = 0.0001). Concurrent decreases in heart rate and specific cardiac output (P = 0.0001) were detected, but stroke volume did not vary significantly. The rate-pressure product was increased only at the highest phenylephrine dosage (P = 0.012). Bradycardia was observed at all dosages during drug infusion, and second-degree atrioventricular block was detected in 88% of horses during infusion. Phenylephrine administration caused dose-dependent splenic contraction, as detected by ultrasonographic measurements of splenic area and thickness (P = 0.0001). At the 3- and 6-micrograms/kg/min infusion rates, splenic area was reduced to 28 and 17% of baseline measurement, respectively. Splenic dimensions had returned to baseline values by 35 minutes after the end of infusion. Infusion of phenylephrine at a dosage of 3 micrograms/kg/min for 15 minutes can be used to induce splenic contraction in horses.

Animals↗

PubMed1994

Effects of phenylephrine on membrane currents in single smooth muscle cells of taenia caeci.

Procedures used for dissociation of taenia caeci smooth muscle cells usually damage alpha 1-adrenoceptors. This paper describes modes of isolation under which alpha 1-adrenoceptors of taenia caeci do not lose their function. It has been found that antioxidants (dithiothreitol or taurine) are able to protect receptors from injury caused by digestive enzymes. A high concentration of bovine serum albumin also protects receptors from enzyme injury if a relatively specific enzyme (collagenase Type XI, Sigma) is used. Phenylephrine (10 mcmol/l) studied both in muscle strips using the double sucrose gap method and in isolated smooth muscle cells using whole cell current clamp conditions substantially hyperpolarized the smooth muscle membrane. This hyperpolarization was blocked by pretreatment of the tissues or cells by prazosin (1 mcmol/l). Phenylephrine (1-50 mcmol/l), under whole cell patch clamp conditions, enhanced the frequency and amplitude of spontaneous transient outward currents (STOCs), which were voltage- and temperature-dependent, and elicited a low amplitude sustained outward current. Phenylephrine (10 mcmol/l) reduced the inward and enhanced the outward component of the total whole cell current evoked by voltage steps from the holding potential of -50 mV to -10 mV. Under experimental conditions when only calcium current was recorded, phenylephrine significantly enhanced its amplitude. These results are in favor of the assumption that phenylephrine induced hyperpolarization is at least partially the consequence of calcium influx, which activates potassium conductance.

Action Potentials↗

PubMed1994

Effects of losartan (DuP753) and enalaprilat on the mean arterial pressure response to phenylephrine.

BACKGROUND: We have found that low-dose infusion of angiotensin II (Ang II) selectively potentiates the mean arterial pressure (MAP) response to phenylephrine in pentobarbital-anesthetized rabbits. OBJECTIVE: To examine whether endogenous Ang II levels in normotensive rabbits maintained on a normal-salt diet exert a potentiating effect on the MAP response to phenylephrine. METHODS: We compared the effects of enalaprilat (0.3 mg/kg per min for 5 min bolus, 1 mg/kg per h infusion), losartan (DuP753; 4 mg/kg bolus, 2 mg/kg per h infusion) and vehicle administration on the MAP response to infusions of phenylephrine that were increased incrementally (2.5, 5 and 10 micrograms/kg per min). RESULTS: Enalaprilat decreased MAP significantly, whereas no maintained change was observed with losartan or vehicle. Phenylephrine infusions elevated MAP significantly and dose-dependently in all of the rabbits studied, but this effect was attenuated significantly in the rabbits given losartan compared with in those given vehicle or enalaprilat. The heart rate responses were not significantly different among the three groups. CONCLUSION: We conclude that inhibition of the renin-angiotensin system at two distinct sites results in different MAP responses to phenylephrine infusion.

Angiotensin II↗

PubMed1977

Influence of temperature and frequency on the positive inotropic action of phenylephrine in the isolated rabbit papillary muscle.

On the isolated papillary muscle of the rabbit the maximal developed tension induced by phenylephrine bia alpha-adrenoceptors was not affected by changing the temperature, while the basal developed tension of the muscle was significantly increased or decreased by lowering the temperature from 37 degrees C to 32 degrees C or by raising it to 42 degrees C, respectively. When the temperature was lowered from 37 degrees C to 32 degrees C in the muscle stimulated at a frequency of 0.5 Hz, the dose-response curve for phenylephrine via alpha-adrenoceptors was shifted to the left (delta pD2-0.47), while that for phenylephrine via beta-adrenoceptors was also shifted to the left to a similar extent (delta pD2=0.43). When the temperature was raised from 37 degrees C to 42 degrees C, the dose-response curve for phenylephrine via alpha-adrenoceptors was markedly shifted to the right (delta pD2=1.58), whereas that via beta-adrenoceptors was not affected at all by this elevation of the temperature (delta pD2=0.04). The change of the stimulation frequency affected chiefly the intrinsic activity of phenylephrine but not the affinity of the drug for alpha-adrenoceptors expressed as the pD2-value.

Animals↗

PubMed1998

Cocaine and lidocaine with phenylephrine as topical anesthetics: antimicrobial activity against common nasal pathogens.

Topical anesthetics are commonly used in the evaluation of nasal pathology. The anesthetics routinely used, 4% lidocaine with phenylephrine, or 4% cocaine, have been demonstrated to have varying inhibitory effects on bacterial cultures. The present study examined the antimicrobial activity of these topical anesthetics used in nasal procedures. The pathogens used were Branhamella catarrhalis, Enterobacter sp., Haemophilus influenzae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pneumoniae. Organisms were against two-fold serial dilutions of stock preparations of 4% lidocaine with 0.25% phenylephrine, 0.25% phenylephrine, 0.1% methylparaben, 250 mg/ml ampicillin, and 4% cocaine. The minimum inhibitory concentration and minimum bactericidal concentration for each of the solutions were obtained. The bacteria studied varied gently in their susceptibility to lidocaine with phenylephrine versus cocaine: Cocaine consistently exhibited greater antimicrobial activity than lidocaine. Phenylephrine and methylparaben showed slight antimicrobial activity. These topical anesthetics have slight bactericidal activity against nasal pathogens, which can sometimes lead to false-negative results. Otolaryngologists should recognize the possible antimicrobial effects of topical anesthetics when culturing specimens. This is especially important when the specimen will be used for guidance of antimicrobial therapy, as in the case of the critically ill patient who requires aspiration for organism-specific therapy. Further studies, specifically in vivo experiments, are needed to determine if use of the drugs produces a significant change in the ability to culture organisms from these sites. This type of study would, however, be difficult to perform, since most patients requiring aspiration are already on high-dose antibiotics that would inhibit the growth of most microorganisms. A modified aspiration technique using a less concentrated topical anesthetic will likely be required to increase the chances of obtaining positive cultures.

Administration, Topical↗

PubMed1998

The influence of experimental hyperlipidemia on the time course of contractility during simulated ischaemia and reperfusion and responsiveness to phenylephrine of rat heart papillary muscle.

The aim of this study was to examine the influence of simulated ischaemia on the contractility and responsiveness to phenylephrine of rat isolated papillary muscle in standard diet fed (SD) and hyperlipidemic diet fed (HLD) rats. The following parameters were measured: force of contraction (Fc), rate of rise (+dF/dt) and rate of fall (-dF/dt) of force of contraction, time to peak contraction (ttp) and relaxation time at 10% of total amplitude of contraction (tt10). The baseline values of Fc and +dF/dt, but, not -dF/dt, were significantly lower in HLD group than in SD group. Tissues from HLD rats were more sensitive to ischaemia regarding Fc, +dF/dt and -dF/dt. Moreover, reprefusion completely reversed the effects of ischaemia only in SD rats, but not in HLD rats, regarding Fc and +dF/dt. In contrast, a recovery of -dF/dt during reperfusion occurred only in the HLD group. In SD rats, phenylephrine (10 and 30 microM) had no effect on the contractility or induced megative inotropic effects (100 and 300 microM). Propranolol (1 microM), a non-selective blocker of beta-adrenoceptors, had no effects on this action. Chloroethylclonidine (CEC) (1 microM), a selectivw blocker of alpha 1b-adrenoceptor subtype, but not WB-4101(2-((2,6-dimethoxyphenoxyethyl)amino-methyl-1,4-benzodioxane), a selective blocker of alpha 1a adrenoceptor subtype, abolishes the negative inotropic action of phenylephrine. In HLD rats, phenylephrine had positive inotropic action (10 and 30 microM). The results indicate that hyperlipidemic diet in rats leads to the suppression of force of contraction and velocity of contraction, but not velocity of relaxation of isolated heart muscle. Under such a condition, heart muscle is more sensitive to ischaemia, but has better responsiveness to phenylephrine after ischeamia-reperfusion period.

Adrenergic alpha-Agonists↗

PubMed1999

Noninvasive assessment of the cardiac baroreflex: response to downward tilting and comparison with the phenylephrine method.

OBJECTIVES: We studied the relation between changes in systolic blood pressure and RR interval during downward tilting in comparison with assessment of baroreflex sensitivity (BRS) measured by the phenylephrine method (Phe-BRS) and with measures of heart rate variability (HRV). BACKGROUND: The method most extensively used for assessing BRS involves bolus injections of phenylephrine. Several noninvasive methods proposed to assess BRS have not been widely applied in the clinical setting. METHODS: Sixteen healthy male volunteers were studied (mean age +/- SD 27.5+/-4.6 years). Arterial blood pressure using tonometry and electrocardiogram was simultaneously recorded. After 20 min of 70 degrees upright tilting, the table was returned to supine position at a speed of 3.2 degrees/s. Subsequently, BRS was assessed using an intravenous bolus injection of phenylephrine (2 to 3 microg/kg). Heart rate variability under resting conditions also was analyzed. RESULTS: In all subjects, a beat to beat systolic blood pressure increase associated with corresponding RR interval lengthening was observed during downward tilting as well as during phenylephrine administration. During both testing procedures, these two variables showed linear correlation, and the slope of regression line during downward tilting (DT-BRS) correlated significantly with Phe-BRS (r = 0.79, p = 0.0003). The DT- and Phe-BRS also correlated significantly with the high frequency component of resting HRV (r = 0.70, p = 0.0023 for DT-BRS; r = 0.58, p = 0.0185 for Phe-BRS). CONCLUSIONS: We conclude that in a small homogeneous group DT-BRS provided an assessment of reflex cardiac vagal function comparable to that obtained by the phenylephrine method.

Adult↗

PubMed2004

ACL deficiency impairs the vasoconstrictive efficacy of neuropeptide Y and phenylephrine in articular tissues: a laser speckle perfusion imaging study.

Sympathetic-derived neuropeptide Y (NPY) helps regulate inflammatory responses in injury and disease, is a vasoconstrictor, and stimulates angiogenesis. Rupture of the anterior cruciate ligament (ACL) is a common clinical presentation that results in tissue inflammation, hyperemia, and angiogenesis in the intact medial collateral ligament (MCL). This study is the first to examine the vasoregulatory role of NPY in ACL-deficient knee joints by using the newly developed technique of laser speckle perfusion imaging (LSPI). MCL blood flow was measured in two groups of adult rabbits: unoperated control (n = 6), and 6-wk ACL transected (n = 5). Under anesthesia, the MCL was surgically exposed and tissue blood flow was imaged at high resolution using LSPI. NPY was applied to the MCL vasculature in topical boluses of 100 mul (dose range 10(-14) to 10(-9) mol), and the alpha-adrenoceptor agonist phenylephrine was applied in doses of 10(-14), 10(-10), and 10(-7) mol. In control rabbits, topical administration of NPY or phenylephrine produced dose-dependent vasopressor responses (maximal effect at 10(-9) mol NPY and 10(-7) mol phenylephrine). In ACL-transected knees, there was little or no vasoconstrictive response to NPY at any dose. The response to phenylephrine was significantly reduced compared with control ligaments. Possible causes of the reduced vasoconstrictive response to NPY in the MCL after 6 wk of ACL deficiency include development of tolerance to the peptide due to a prolonged increase in sympathetic nerve activity or change in the distribution or functionality of the NPY Y(1) receptors. Chronic ACL deficiency leads to profound and protracted hyperemia in associated articular tissues. Abrogation of a vasoconstrictor response to both NPY and phenylephrine in the MCL indicates that ACL deficiency induces major changes in the vascular physiological homeostasis.

Animals↗

PubMed1986

Aqueous vs viscous phenylephrine. I. Systemic absorption and cardiovascular effects.

We studied 30 patients undergoing vitreoretinal surgery to compare the systemic absorption and cardiovascular effects of 2.5% aqueous and 2.5% viscous (21 cp) ophthalmic solutions of phenylephrine hydrochloride. No significant differences were noted in the plasma levels or changes in blood pressure between the two groups, although there was a tendency toward higher mean plasma levels and blood pressures in groups receiving 2.5% aqueous phenylephrine hydrochloride. Maximum plasma levels were achieved within the first 20 minutes following topical application of phenylephrine eye drops, irrespective of the nature of the vehicle. This finding emphasizes the importance of monitoring these patients, especially those at high risk for any adverse cardiovascular effects during the first 20 to 30 minutes following instillation of phenylephrine eye drops. The patients in our study were supine and under general anesthesia. Therefore, there was no effect by lid blinking, the lacrimal pump, or gravity, which would ordinarily increase absorption by the nasal mucosa through the nasolacrimal system. By eliminating these variable factors, such as lid blinking, the study was performed in a stable and controlled manner, but the results may not be directly applicable to an upright awake patient.

Adult↗