Increasing maternal blood pressure with ephedrine increases uterine artery blood flow velocity during uterine contraction

BACKGROUND: During labor, ephedrine is widely used to prevent or to treat maternal arterial hypotension and restore uterine perfusion pressure to avoid intrapartum fetal asphyxia. However, the effects of ephedrine on uterine blood flow have not been studied during uterine contractions. The purpose of the study was to assess the effects of ephedrine on uterine artery velocities and resistance index using the Doppler technique during the active phase of labor. METHODS: Ten normotensive, healthy parturients with uncomplicated pregnancies at term received intravenous ephedrine during labor to increase mean arterial pressure up to a maximum of 20% above their baseline pressure. Peak systolic and end-diastolic Doppler flow velocities and resistance indices were measured in the uterine artery before and immediately after administration of bolus intravenous ephedrine and after ephedrine washout. Umbilical and fetal middle cerebral arterial resistance indices and fetal heart rate were also calculated. RESULTS: After ephedrine administration, mean arterial pressure increased by 17 +/- 4%. End-diastolic flow velocity in the uterine artery at peak amplitude of uterine contraction was restored to 74% of the value observed in the absence of contraction. The systolic velocity was totally restored, and the uterine resistance index was significantly decreased, compared with the values in the absence of contraction. Between uterine contractions, ephedrine induced similar but less marked effects. Fetal hemodynamic parameters were not altered by ephedrine administration. CONCLUSIONS: Bolus administration of intravenous ephedrine reversed the dramatic decrease in diastolic uteroplacental blood flow velocity and the increase in resistance index during uterine contraction, without altering fetal hemodynamic parameters. This suggests that the increase in uterine perfusion pressure during labor could in part restore uterine blood flow to the placenta during uterine contraction.     

Ephedrine and phenylephrine for avoiding maternal hypotension due to spinal anaesthesia for caesarean section. Effects on uteroplacental and fetal haemodynamics

The effects of i.v. vasopressors on Doppler velocimetry of the maternal uterine and placental arcuate arteries and the fetal umbilical, renal and middle cerebral arteries were studied during spinal anaesthesia in 19 healthy parturients undergoing elective caesarean section. Fetal myocardial function was investigated at the same time by M-mode echocardiography. The patients were randomized into two groups, to be given either ephedrine or phenylephrine as a prophylactic infusion supplemented with minor boluses if systolic arterial pressure decreased by more than 10 mmHg from the control value. Both the vasopressors restored maternal arterial pressure effectively. The ephedrine group showed no significant differences in any of the Doppler velocimetry recordings relative to the baseline values, but during the phenylephrine infusion the blood flow velocity waveform indices for the uterine and placental arcuate arteries increased significantly and vascular resistance decreased significantly in the fetal renal arteries. Healthy fetuses seem to tolerate these changes in uteroplacental circulation well, however, since the Apgar scores for the newborns and the acid-base values in the umbilical cord were within the normal range in both groups. The results suggest that some caution is required when selecting the specific vasopressor agent, the dosage and the mode of administration for the treatment of maternal hypotension secondary to spinal anaesthesia for caesarean section.     

The effects of ephedrine and etilefrine on uterine and fetal blood flow and on fetal myocardial function during spinal anaesthesia for caesarean section

The effects of two vasopressors, ephedrine and etilefrine, on blood flow in maternal uterine, fetal umbilical, middle cerebral and renal arteries and on fetal myocardial function were studied by colour Doppler and M-mode echocardiography techniques during spinal anaesthesia for caesarean section. There were 7 healthy pregnant women in each treatment group. The vascular resistance of maternal uterine arteries increased significantly after both of the vasopressors while the vascular resistance of the umbilical artery remained unchanged. Ephedrine decreased the blood velocity waveform indices in the fetal middle cerebral and renal arteries, increased fetal right ventricular contractility and decreased left ventricular inner end-diastolic dimension. Fetal heart rate was unchanged. Etilefrine caused no detectable changes in fetal haemodynamics or in fetal myocardial function. These findings demonstrate that vasopressors administered for the treatment of minor maternal arterial pressure fall produce vasoconstriction in the uterine circulation during spinal anaesthesia, yet healthy fetuses seem to tolerate these haemodynamic alterations well. On the other hand, ephedrine caused changes in fetal myocardial function and in the vascular resistance of fetal middle cerebral and renal arteries, which demonstrates the potential modifying effect of vasoactive drug given to the mother on fetal haemodynamics.     

Single bolus compared with a fractionated dose injection technique of bupivacaine for extradural Caesarean section: effect on uteroplacental and fetal haemodynamic state

We studied 26 healthy parturients undergoing elective Caesarean section, allocated randomly to receive extradural block with 0.5% plain bupivacaine in a double-blind manner in either a single bolus or fractionated doses. After a 3-ml test dose, an additional 20 ml of bupivacaine were given over a 5-min period in the single bolus group (n = 13) and over a 25-min period in the fractionated dose group (n = 13). We studied the effects of bupivacaine on blood flow velocities in the maternal placental and non-placental uterine and fetal umbilical arteries before and four times during establishment of extradural block using a pulsed colour Doppler technique. Median sensory block reached T3 in the single-dose group compared with T4 in the fractionated-dose group. Two subjects in each group required i.v. ephedrine to correct transient hypotension (systolic arterial pressure < 90 mm Hg). Blood flow velocity waveform indices of the uterine and umbilical arteries did not differ significantly within or between groups during the study. There was no significant difference in neonatal outcome, as assessed by Apgar scores and umbilical artery pH values. In conclusion, we observed no deterioration in uteroplacental circulation after administration of a single bolus dose of bupivacaine.      

Which vasopressor should be used to treat hypotension during magnesium sulfate infusion and epidural anesthesia?

Ephedrine restores and/or protects uterine blood flow and fetal well-being in laboratory animals. In contrast, alpha 1-adrenergic agonists worsen uterine blood flow and fetal condition. We previously demonstrated that magnesium sulfate (MgSO4) attenuates the detrimental effects of phenylephrine on uterine vascular resistance in gravid ewes. Therefore, we performed this study to determine whether ephedrine or phenylephrine better restores and protects uterine blood flow and fetal oxygenation during epidural anesthesia-induced hypotension in hypermagnesemic gravid ewes. Twelve chronically instrumented gravid ewes were each used for three experiments: 1) ephedrine, 2) phenylephrine, and 3) normal saline (NS)-control. For each experiment the protocol was as follows: 1) at time zero, intravenous infusion of MgSO4 was begun; 2) at 150 min a thoracic level of epidural anesthesia was achieved with 2% lidocaine; and 3) at 165 min, an intravenous infusion of ephedrine, phenylephrine, or NS was begun and continued through 195 min. Epidural anesthesia uniformly decreased maternal mean arterial blood pressure (MAP), heart rate, cardiac output, uterine blood flow, and fetal PO2 in each of the three groups. Both ephedrine and phenylephrine restored maternal MAP to baseline, as expected from the experimental design. Ephedrine significantly increased cardiac output and uterine blood flow when compared with NS-control, but phenylephrine did not. Phenylephrine significantly increased uterine vascular resistance when compared with NS-control, but ephedrine did not. As a result, fetal pH and PO2 were significantly greater during ephedrine infusion than during infusion of NS-control. Fetal pH was stable during ephedrine infusion, but it continued to decrease during phenylephrine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of volume preload on uteroplacental blood flow during epidural anaesthesia for Caesarean section

BACKGROUND AND OBJECTIVE: Epidural and spinal anaesthesia are the preferred mode of anaesthesia for Caesarean section. Volume preloading is recommended to prevent maternal hypotension and a reduction in uteroplacental blood flow, although positive effects of volume preloading on maternal cardiac output and arterial pressure are debatable. Doppler measurements of the umbilical artery beyond deriving pulsatility indices are not routinely performed. METHODS: After Institutional Review Board approval and written informed consent, 14 consecutiVe women with epidural anaesthesia for Caesarean section received either hydroxyethyl starch 500 mL or gelatine 500 mL. Haemodynamic variables monitored were maternal arterial pressure, maximal blood flow velocity and pulsatility indices of the uterine artery derived from Doppler measurements. CONCLUSIONS: Maternal arterial pressure and pulsatility indices in both groups did not change from baseline after intravenous colloid infusion. However, uterine blood flow increased significantly in both groups. The effectiveness of volume preloading may therefore be better described by changes in maximum uterine blood flow velocity than by pulsatility indices or maternal arterial pressure.     

The effects of regional anaesthesia for caesarean section on maternal and fetal blood flow velocities measured by doppler ultrasound

We studied the effects of spinal anaesthesia (Group S), epidural anaesthesia (Group E), and combined spinal and epidural anaesthesia (Group SE), on maternal and fetal blood flow in 24 healthy parturients (n = 8/group) with uncomplicated singleton pregnancies using Doppler technique. Prior to the induction of anaesthesia, the patients were prehydrated with balanced electrolyte solution 15 ml kg^-1 over a period of 15 min. After the induction of regional anaesthesia, the systolic blood pressure was maintained within 15% limits of the preoperative values using prophylactic etilefrine infusion in Groups S and SE. The flow velocity waveforms of the maternal femoral artery, the main branch of the uterine artery (placental side), the foetal umbilical and middle cerebral arteries were recorded by Doppler technique before and after prehydration as well as after onset of T7 analgesia and the pulsatility indices (PI) were derived. Rapid intravenous prehydration had no effects on uteroplacental or fetal circulation as indicated by unaltered uterine, umbilical, and fetal middle cerebral artery Pis. After the onset of T7 analgesia, the uterine artery PI was increased in Group S indicating increased uterine vascular resistance while no changes occurred in Groups E and SE. No adverse effects were observed on the neonates as indicated by the Apgar score and the umbilical artery and vein acid–base status in any of the groups.     

Divergent effects of ephedrine and phenylephrine on cardiovascular hemodynamics of near-term fetal sheep exposed to hypoxemia and maternal hypotension

BACKGROUND: We hypothesized that the administration of ephedrine and phenylephrine for maternal hypotension modifies cardiovascular hemodynamics in near-term sheep fetuses. METHODS: At 115-136 days of gestation, chronically instrumented, anesthetized ewes with either normal placental function or increased placental vascular resistance after placental embolization were randomized to receive boluses of ephedrine (n = 12) or phenylephrine (n = 12) for epidural-induced hypotension after a short period of hypoxemia. Fetal cardiovascular hemodynamics were assessed by Doppler ultrasonography at baseline, during hypotension and after vasopressor treatment. RESULTS: During hypotension, fetal PO(2) decreased and proximal branch pulmonary arterial and pulmonary venous vascular impedances increased. Additionally, in the embolized fetuses, the time-velocity integral ratio between the antegrade and retrograde blood flow components of the aortic isthmus decreased. These parameters were restored to baseline conditions by ephedrine but not by phenylephrine. With phenylephrine, weight-indexed left ventricular cardiac output and ejection force decreased in the non-embolized fetuses, and the proportion of isovolumetric contraction time of the total cardiac cycle was elevated in the embolized fetuses. CONCLUSIONS: After exposure to hypoxemia and maternal hypotension, ephedrine restored all fetal cardiovascular hemodynamic parameters to baseline. Phenylephrine did not reverse fetal pulmonary vasoconstriction or the relative decrease in the net forward flow through the aortic isthmus observed in fetuses with increased placental vascular resistance. Moreover, fetal left ventricular function was impaired during phenylephrine administration.     

A comparison of the hemodynamic effects of paracervical block and epidural anesthesia for labor analgesia

BACKGROUND: Both paracervical block (PCB) and epidural analgesia are sometimes associated with hemodynamic effects potentially harmful to the well-being of the fetus. Our study was designed to test the hypothesis that PCB would have a more profound effect on maternal and fetal blood flow than epidural analgesia. METHODS: Forty-four healthy primiparous parturients were randomized to receive either PCB (n=21) or epidural analgesia (n= 23) with 25 or 30 mg of bupivacaine, respectively, for labor analgesia. Maternal blood pressure and fetal heart rate were recorded. Blood flow was measured using a color Doppler device. The blood flow measurements consisted of assessment of the pulsatility indices (PI) of the right maternal femoral artery and the main branch of the uterine artery (placental side), the umbilical artery and the fetal middle cerebral artery. The measurements were performed before administration of analgesia and approximately 15-20 min later after the onset of analgesia. RESULTS: Both methods provided in general good analgesia, but rescue medication was required more often after PCB. Epidural analgesia decreased maternal blood pressure more than PCB and the PI of maternal femoral artery decreased after onset of epidural analgesia, indicating epidural-induced vasodilation. The PI of the uterine artery increased after the onset of PCB, indicating vasoconstriction of this artery. No significant adverse effects or differences in the well-being of the newborn were observed, as indicated by similar Apgar scores and pH-status. CONCLUSION: There were small differences in the effects of PCB and epidural analgesia on uteroplacental circulation as well as on maternal hemodynamics. PCB may have a vasoconstrictive effect on the uterine artery. This and the fact that the parturients required rescue analgesia more frequently after PCB than after epidural block speaks for the feasibility of the latter in obstetrics.     

Effects of normovolaemic haemodilution on middle cerebral artery blood flow velocity and oxygen delivery

BACKGROUND AND OBJECTIVE: Assessment of the effects of normovolaemic haemodilution on middle cerebral artery blood flow velocity with transcranial Doppler ultrasonography, intracranial pressure, cerebral perfusion pressure, arterial oxygen content and cerebral oxygen delivery. METHODS: Normovolaemic haemodilution was induced in rabbits under general anaesthesia, and the haematocrit was allowed to decrease to 30% in Group 1 (n = 6) and to 20% in Group 2 (n = 6). Peak systolic and diastolic velocities, mean blood flow velocity, and pulsatility and resistance indices of the middle cerebral artery were measured by transcranial Doppler ultrasonography. Changes in intracranial pressure, cerebral perfusion pressure, arterial oxygen content and cerebral oxygen delivery were also assessed. RESULTS: In Group 2, middle cerebral artery blood flow velocity increased from 0.4 +/- 0.01 to 0.51 +/- 0.02 m s(-1) after the induction of normovolaemic haemodilution (P = 0.04), while arterial oxygen content decreased from 16.2 +/- 0.1 to 8.5 +/- 0.1 mLdL(-1) (P = 0.002). The decrease in cerebral oxygen delivery from 6.5 +/- 0.2 to 4.3 +/- 0.2 was also significant (P = 0.02). However, no associated changes in intracranial pressure and cerebral perfusion pressure could be demonstrated. CONCLUSIONS: Normovolaemic haemodilution resulted in an increase in the mean blood flow velocity of the middle cerebral artery. However, this increase did not compensate for the consequences of the altered oxygen delivery to the brain when the haematocrit was reduced to 20%.     

Comparison of metaraminol and ephedrine infusions for maintaining arterial pressure during spinal anesthesia for elective cesarean section

BACKGROUND: Although ephedrine is usually recommended as the first-line vasopressor in obstetrics, its superiority over other vasopressors has not been proven in humans. METHODS: In a double-blind study, the authors randomized women having elective cesarean section with spinal anesthesia to receive an intravenous infusion of ephedrine, starting at 5 mg/min (n = 25), or metaraminol, starting at 0.25 mg/min (n = 25), titrated to maintain systolic arterial pressure in the target range 90-100% of baseline. Umbilical cord gases, maternal hemodynamics, uterine artery puLsatility index, and Apgar scores were compared. RESULTS: Systolic arterial pressure was maintained more closely in the target range in the metaraminol group compared with the ephedrine group. In the metaraminol group, umbilical arterial pH was greater (median and interquartile range, 7.31 and 7.31-7.33 vs. 7.24 and 7.14-7.29; P < 0.0001), and umbilical venous pH was greater (7.36 and 7.35-7.38 vs. 7.33 and 7.26-7.34; P < 0.0001) compared with the ephedrine group. No patient in the metaraminol group had umbilical arterial pH less than 7.2, compared with nine patients (39%) in the ephedrine group (P = 0.0005). Apgar scores were similar between groups. Changes in uterine artery pulsatility index were similar between groups. CONCLUSIONS: When used by infusion to maintain arterial pressure during spinal anesthesia for cesarean section, metaraminol was associated with less neonatal acidosis and more closely controlled titration of arterial pressure compared with ephedrine.     

Significance of retrograde diastolic uterine artery blood flow during regional anesthesia in instrumented pregnant sheep

Background: We studied the interactions between uterine and placental hemodynamics during maternal hypotension in chronically instrumented fetal sheep. In addition, we investigated maternal hemodynamic characteristics, fetoplacental hemodynamics and fetal acid–base status when a retrograde diastolic uterine artery blood flow pattern is present during maternal hypotension. Methods: Invasive maternal and fetal hemodynamic parameters, uterine (Q_UtA) and placental (Q_UA) volume blood flows and acid–base values were examined in 24 chronically instrumented sheep at baseline and during epidural‐induced maternal hypotension at 117–132 (term 145) days of gestation. Uterine artery blood flow velocity waveforms were obtained by Doppler ultrasonography. Results: Maternal hypotension decreased Q_UtA without affecting Q_UA. During hypotension, eight out of 24 sheep demonstrated a retrograde diastolic blood flow velocity waveform pattern in the uterine artery. Maternal systolic, diastolic and mean arterial blood pressures were significantly lower in the retrograde group than in the antegrade group. No statistically significant differences in Q_UtA, Q_UA and fetal blood gas values were detected between the two groups during hypotension. Conclusions: An acute decrease in uterine artery volume blood flow during maternal hypotension is not compensated by increased placental volume blood flow. A retrograde diastolic blood flow pattern in the uterine artery is related to lower maternal arterial pressures, especially during diastole. A uterine artery retrograde diastolic blood flow pattern does not have any additional detrimental short‐term effects on fetal acid–base status.     

Comparison of Metaraminol and Ephedrine Infusions for Maintaining Arterial Pressure during Spinal Anesthesia for Elective Cesarean Section

Background: Although ephedrine is usually recommended as the first-line vasopressor in obstetrics, its superiority over other vasopressors has not been proven in humans.

Methods: In a double-blind study, the authors randomized women having elective cesarean section with spinal anesthesia to receive an intravenous infusion of ephedrine, starting at 5 mg/min (n = 25), or metaraminol, starting at 0.25 mg/min (n = 25), titrated to maintain systolic arterial pressure in the target range 90-100% of baseline. Umbilical cord gases, maternal hemodynamics, uterine artery pulsatility index, and Apgar scores were compared.

Results: Systolic arterial pressure was maintained more closely in the target range in the metaraminol group compared with the ephedrine group. In the metaraminol group, umbilical arterial p H was greater (median and interquartile range, 7.31 and 7.31-7.33 vs. 7.24 and 7.14-7.29;P < 0.0001), and umbilical venous p H was greater (7.36 and 7.35-7.38 vs. 7.33 and 7.26-7.34;P < 0.0001) compared with the ephedrine group. No patient in the metaraminol group had umbilical arterial p H less than 7.2, compared with nine patients (39%) in the ephedrine group (P = 0.0005). Apgar scores were similar between groups. Changes in uterine artery pulsatility index were similar between groups.     

Randomized trial of bolus phenylephrine or ephedrine for maintenance of arterial pressure during spinal anaesthesia for Caesarean section

Thirty-eight healthy women undergoing elective Caesarean section under spinal anaesthesia at term were allocated randomly to receive boluses of either phenylephrine 100 micrograms or ephedrine 5 mg for maintenance of maternal arterial pressure. The indication for administration of vasopressor was a reduction in systolic pressure to < or = 90% of baseline values. Maternal arterial pressure (BP) and heart rate (HR) were measured every minute by automated oscillometry. Cardiac output (CO) was measured by cross-sectional and Doppler echocardiography before and after preloading with 1500 ml Ringer lactate solution and then every 2 min after administration of bupivacaine. Umbilical artery pulsatility index (PI) was measured using Doppler before and after spinal anaesthesia. The median (range) number of boluses of phenylephrine and ephedrine was similar; 6 (1-10) vs 4 (1- 8) respectively. Maternal systolic BP and CO changes were similar in both groups, but the mean [95% CI] maximum percentage change in maternal HR was larger in the phenylephrine group (-28.5 [-24.2, - 32.9]%) than in the ephedrine group (-14.4 [-10.6, -18.2]%). As a consequence atropine was required in 11/19 women in the phenylephrine group compared with 2/19 in the ephedrine group (P < 0.01). Mean umbilical artery pH [95% CI] was higher in the phenylephrine group (7.29 [7.28-7.30]) than in the ephedrine group (7.27 [7.25-7.28]). The results of the present study support the use of phenylephrine for maintenance of maternal arterial pressure during spinal anaesthesia for elective Caesarean section.      

The influence of labor epidural analgesia on maternal,uteroplacental and fetoplacental hemodynamics in normotensive parturients: a prospective observational study

BackgroundEpidural analgesia provides sufficient analgesia during labor but can cause hypotension despite various prophylactic measures. We studied its effects on pre-placental, fetoplacental, and fetal hemodynamics using Doppler ultrasound. The primary endpoint was the pulsatility index of the umbilical artery at 30 min after establishing epidural analgesia. Secondary endpoints included maternal blood pressures and neonatal outcome data.MethodsWe included healthy parturients at a cervical dilation ≥2 cm, with or without a request for epidural analgesia (n=32 per group). Ultrasound studies of the uterine arteries, umbilical artery and fetal middle cerebral artery were performed before insertion of the epidural catheter, and 30, 60 and 90 min after; the same time-points were assessed in the non-epidural control group. Maternal blood pressure was measured by a continuous non-invasive arterial pressure monitor.ResultsUltrasound studies detected no significant differences in pulsatility indices over time in any blood vessel. In contrast to the control group, maternal blood pressures were significantly lower for all measures after the onset of analgesia compared with baseline values (mean systolic pressure decreased from 132.7 ± 15.9 mmHg to 123.1 ± 14.4 mmHg at 30 min, P=0.003). The mean pH value of the umbilical arterial blood was 7.29 (±0.06) in the epidural group versus 7.31 (±0.08) in the control group (P=0.33). The median Apgar score at 5 min was 10 in both groups.ConclusionsPre-placental, fetoplacental and fetal hemodynamics remained stable despite a statistically significant decrease in maternal blood pressure in laboring parturients receiving epidural analgesia.     

Cardiovascular effects and placental passage of dantrolene in the maternal-fetal sheep model

Using the chronic maternal-fetal sheep preparation, nine pregnant ewes were studied to determine the effects of intravenous dantrolene sodium on maternal and fetal physiology, with particular reference to its placental passage, and its effects on uterine blood flow and uterine tone. Two doses of dantrolene sodium were studied: 1.2 mg/kg and 2.4 mg/kg. After 2.4 mg/kg, maternal cardiac output increased 29% (P less than 0.05) after 1 min and returned to normal after 30 min. Maternal mean arterial pressure increased 13% after 1 min and remained significantly elevated (P less than 0.01) for 3 h. No significant changes (P greater than 0.05) were observed in maternal heart rate, uterine artery blood flow, or central venous pressure. Maternal arterial pH declined from 7.42 to 7.39 (P less than 0.01) after 1 min and returned to baseline values after 10 min. Fetal heart rate decreased 24% (P less than 0.01) after 3 min and returned to normal after 10 min; the mean fetal arterial pressure remained unchanged (P greater than 0.05). Fetal arterial pH declined from 7.29 to 7.27 (P less than 0.05) after 1 min and remained significantly decreased for 120 min. Similar changes of lesser magnitude and shorter duration were seen following the 1.2 mg/kg dose. Maternal levels of dantrolene were less than 3 micrograms/ml. Although an equilibrium between maternal and fetal plasma dantrolene concentrations was apparent at 5 min, the fetal levels of dantrolene were approximately 10% of the mother's. The results indicate that the administration of intravenous dantrolene at 1.2 mg/kg or 2.4 mg/kg has no clinically significant adverse effect on mother or fetus in the sheep model.     

Post-transplant renal artery stenosis: the hemodynamic response to revascularization.

BACKGROUND: Percutaneous transluminal angioplasty and stenting are relatively noninvasive approaches to treat post-transplant renal artery stenosis. However, the real impact of this procedure on renal function recovery has never been quantitated precisely to date. METHODS: In eight consecutive renal transplant patients with renal graft artery stenosis, blood pressure, body weight, and anatomical, functional, and Doppler ultrasound parameters were evaluated before and one month after renal artery transluminal angioplasty and stenting. On both occasions, glomerular filtration rate and renal plasma flow were evaluated by inulin and paraaminohippuric acid renal clearances, and glomerular size-selective function was evaluated by the fractional clearances of neutral dextran macromolecules. RESULTS: The correction of renal artery stenosis, by normalizing renal vascular resistances, fully restored kidney perfusion and decreased arterial blood pressure, relieved water and sodium retention, restored an almost laminar arterial blood flow, and normalized vascular shear stress without appreciable effects on glomerular barrier size-selective function and proteinuria. Preangioplasty and postangioplasty renal resistive indices and peak systolic blood velocity estimated by Doppler ultrasounds were significantly correlated with the effective renal plasma flow and the blood velocity calculated at the site of stenosis. All patients were discharged without sequelae one or two days after angioplasty. CONCLUSIONS: Percutaneous transluminal angioplasty and stenting are safe and effective procedures to normalize the functional changes sustained by hemodynamically significant artery stenosis after renal transplantation. Doppler ultrasound scanning is a reliable and reproducible technique to monitor the renal functional response to vascular reperfusion.     

The hemodynamics of vacuum constriction erections: assessment by color Doppler ultrasound.

Duplex ultrasound with pulsed Doppler and color flow sonography were used to image the penis and conduct blood flow velocity studies in 5 patients. Cavernous body cross sectional area, cavernous artery diameters and peak systolic velocities were measured in the flaccid shaft, after transient exposure to negative pressure in a vacuum constriction device, and with a vacuum constriction device band applied to the tumescent shaft. We found that exposure to vacuum transiently increased central cavernous arterial blood flow velocities compared to baseline values in all patients. After a trial of a vacuum constriction device and application of the constricting band cavernous body cross sectional areas doubled. Despite increased cavernous arterial diameters in 4 of 5 patients and increased blood flow in all patients after vacuum-induced tumescence alone, we could not visualize arterial inflow in the penile shaft once the constricting band was in place. Color Doppler ultrasound can detect cavernous artery systolic flow as low as 2 to 9 cm. per second. Our data suggest that the erectile state maintained distal to the vacuum constriction device band is low flow and relatively ischemic.     

Effects of verapamil on uterine blood flow and maternal cardiovascular function in the awake pregnant ewe

Calcium entry blocking drugs may have a role in the treatment of maternal and fetal tachyarrhythmias, as well as for treatment of premature labor. This study was undertaken to assess the hemodynamic effects of verapamil in the awake pregnant ewe. Verapamil, 0.2 mg/kg administered intravenously over 3 min, resulted in the following maternal cardiovascular changes: transient (2 min) but significant decreases in systolic, diastolic, and mean blood pressures, and significant but equally transient increases in central venous pressure and mean pulmonary arterial pressure. Pulmonary capillary wedge pressure increased for 5 min. These results are consistent with the negative inotropic and peripheral vasodilating effects of verapamil. Cardiac output, systemic vascular resistance, and pulmonary vascular resistance were unaffected. Uterine blood flow decreased 25% at 2 min and remained significantly (7-18%) below control levels for 30 min after drug injection. The effects of verapamil on uterine blood flow suggest that it should be used with caution in cases where uteroplacental perfusion is compromised.     

Prevention of spinal hypotension associated with cesarean section by aortocaval compression--left 15 degree table tilt vs. uterine displacement by hand

Women undergoing elective cesarean delivery were randomly assigned to receive a spinal anesthesia in either the semi-lateral (group SL) position or the supine position with uterine displacement (group UD). After spinal injection, group SL patients were turned to a 15 degrees left lateral supine position, and group UD patients had uterine displacement by hand. Ephedrine 4 mg i.v. was administered in case of nausea/vomiting and/or hypotension, defined as a systolic blood pressure below 100 mmHg. Arm systolic arterial pressure and leg systolic arterial pressure were similar in both groups, but the lowest leg systolic arterial pressure until delivery was significantly lower in the UD group (P < 0.05). Mean ephedrine requirement was significantly less in the SL group (P < 0.05). Apgar scores did not differ, but umbilical artery pH values were significantly higher in patients of the group SL (P < 0.01).