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Biomedical subjects

D H Chestnut

Publications and source records attributed to D H Chestnut.

At least 55 records · Page 3Linked to original sources
PubMed1990

Does ritodrine worsen maternal hypotension during epidural anesthesia in gravid ewes?

The purpose of this study was to determine whether prior administration ritodrine worsens maternal hypotension during epidural anesthesia in gravid ewes. Twenty-four experiments were performed in nine chronically instrumented animals between 0.8 and 0.9 of timed gestation. The experimental sequence included the following: 1) at time-zero, intravenous (iv) administration of ritodrine, 0.004 mg.kg-1.min-1, or normal saline (NS) for 2 h; 2) at 120 min discontinuation of ritodrine, and administration of a 500 ml iv bolus of NS over 15 min; and 3) at 135 min epidural injection of 2% lidocaine or NS. There were three groups of experiments: 1) iv ritodrine-epidural lidocaine (n = 9); 2) iv NS-epidural lidocaine (n = 8); and 3) iv ritodrine-epidural NS (n =7). Epidural injection of lidocaine resulted in a median sensory level of T9 in both the ritodrine-lidocaine and NS-lidocaine groups. At 165 min (i.e., 30 min after the epidural injection of lidocaine), maternal mean arterial pressure was 19 +/- 3% below baseline (P = 0.0001) in the ritodrine-lidocaine group and 22 +/- 7% below baseline (P = 0.0001) in the NS-lidocaine group (NS between groups). At 120 min ritodrine had increased maternal cardiac output 45 +/- 6% above baseline (P = 0.0001) in the ritodrine-lidocaine group and 39 +/- 6% above baseline (P = 0.0001) in the ritodrine-NS group. Cardiac output remained above baseline (P less than 0.01) after epidural injection of lidocaine in the ritodrine-lidocaine group. In contrast, in the NS-lidocaine group cardiac output was 13 +/- 5% below baseline (P = 0.005) at 150 min. Fetal arterial pH did not change significantly in either the ritodrine-lidocaine or ritodrine-NS group.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Epidural↗
PubMed1990

Continuous epidural infusion of 0.0625% bupivacaine-0.0002% fentanyl during the second stage of labor.

A randomized, double-blind, placebo-controlled study was performed to evaluate the analgesic efficacy and influence of continuing an epidural infusion of 0.0625% bupivacaine-0.0002% fentanyl during the second stage of labor in nulliparous women. When the cervix was fully dilated, coded study solution was substituted for the known bupivacaine-fentanyl solution. The study solution for 29 patients was 0.0625% bupivacaine-0.0002% fentanyl; 34 patients received saline placebo. The two groups had similar pain scores during the first stage of labor. During the second stage, pain scores were significantly higher in the saline-placebo group at each 30-min interval between 60 and 150 min after the diagnosis of full cervical dilation. Similarly, there was a significant difference between the two groups in global assessment of analgesia quality during the second stage, but the difference occurred in those patients with a second-stage duration of greater than or equal to 60 min. Among the women who delivered vaginally, eleven of 28 (39%) women in the bupivacaine-fentanyl group, versus five of 34 (15%) in the saline-placebo group, had surgical perineal anesthesia for vaginal delivery (P less than .05). Six of 28 (21%) women in the bupivacaine-fentanyl group, and five of 34 (15%) in the saline-placebo group, underwent instrumental vaginal delivery (P = NS). The median duration of the second stage of labor was 53 min (range = 5-283) in the bupivacaine-fentanyl group, and 63 min (range = 16-181) in the saline-placebo group (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Epidural↗
PubMed1990

Does indomethacin alter the hemodynamic response to magnesium sulfate infusion and hemorrhage in gravid ewes?

The purpose of this study was to determine whether indomethacin alters the maternal and fetal hemodynamic response to magnesium sulfate (MgSO4) infusion and hemorrhage in gravid ewes. We studied seven chronically instrumented animals between 0.8 and 0.9 of timed gestation. The experimental sequence included: 1) at time 0, indomethacin, 2 mg/kg, or vehicle only intravenously (IV) over 5 minutes; 2) at 60 minutes, MgSO4 4 g IV over 5 minutes; 3) at 65 minutes, MgSO4 infusion at 4 g/hour; 4) at 150 minutes, maternal hemorrhage, 20 mL/kg, over 60 minutes; and 5) at 215 minutes, reinfusion of maternal blood over 60 minutes. Each animal was studied with and without indomethacin. Indomethacin, but not vehicle only, transiently increased maternal and fetal mean arterial pressure (MAP), decreased maternal and fetal heart rate, and decreased maternal cardiac output. Magnesium sulfate significantly decreased uterine vascular resistance and increased uterine blood flow both with and without indomethacin. Hemorrhage significantly decreased maternal MAP, heart rate, cardiac output, and uterine blood flow in both groups. The magnitude of each change was similar between the groups. For example, at the end of hemorrhage, maternal MAP was 36 +/- 7% below baseline (P = .0001) with indomethacin and 41 +/- 2% below baseline (P = .0001) in the vehicle-only group (P = not significant between groups). Hemorrhage significantly decreased fetal heart rate, pH, and PO2, and increased fetal MAP and PCO2 in both groups. We conclude that indomethacin did not alter the maternal or fetal hemodynamic response to MgSO4 infusion and hemorrhage in gravid ewes.

Acid-Base Equilibrium↗
PubMed1989

Effect of exogenous prostacyclin on central and uterine hemodynamics in the chronically instrumented pregnant guinea pig before and after indomethacin administration.

The effect of prostacyclin before and after pretreatment with indomethacin was studied in the chronically instrumented pregnant guinea pig. Twenty-six animals were studied between 45 and 65 days' gestation. Prostacyclin (6.25, 12.5, 25, 50, and 125 micrograms/kg/min) produced a dose-dependent decrease in arterial pressure (r = -0.915, p less than 0.0001) and uterine artery blood flow velocity, as measured by a miniaturized Doppler flow probe (r = -0.850, p = 0.0001), and an increase in heart rate (r = 0.745, p = 0.0335). Uterine resistance increased at each dose, with 125 micrograms/kg/min generating an increase greater than all others (p less than 0.02). The hypotensive effect of prostacyclin was blunted by indomethacin (p = 0.018). Rather than blunting the expected changes in the remaining parameters, pretreatment with indomethacin followed by prostacyclin significantly decreased uterine blood flow velocity further and increased uterine resistance. We conclude that prostacyclin infusion can have adverse effects on uterine blood flow and that these are altered by pretreatment with a prostaglandin synthetase inhibitor. Prostacyclin should be avoided in women with preeclampsia until further animal studies are available.

Animals↗
PubMed1989

Intravenous administration of d-tubocurarine and pancuronium in fetal limbs.

The purpose of this study was to assess the effects of intravenous administration of d-tubocurarine and pancuronium in fetal lambs. Eighteen experiments were performed in seven chronically instrumented pregnant ewes between 0.8 and 0.9 of timed gestation. Each fetus received 6 ml of study drug intravenously at 1.2 ml/min over 5 minutes (d-tubocurarine 3.0 mg/kg, pancuronium 0.5 mg/kg, or saline solution control). Pancuronium (n = 7) significantly increased both fetal heart rate and mean arterial pressure. d-Tubocurarine (n = 5) significantly decreased both fetal heart rate and mean arterial pressure. Saline solution control (n = 6) did not significantly alter fetal heart rate or mean arterial pressure. The present study suggests that pancuronium is preferable to d-tubocurarine for those intrauterine procedures when an increase in fetal heart rate is desired.

Animals↗
PubMed1989

Does furosemide alter the hemodynamic response to rapid intravascular transfusion of the anemic fetal lamb?

The purpose of this study was to define the hemodynamic response to rapid intravascular transfusion of the anemic fetal lamb and to determine whether furosemide alters that response. Sixteen experiments were performed in nine chronically instrumented gravid ewes between 0.8 and 0.9 of timed gestation. On day 1 of each experiment, each fetus was subjected to hemorrhage (40 ml/kg of estimated fetal weight) over 1 hour. On day 2, plasma was withdrawn from the stored fetal blood until the hematocrit was approximately 70%, and the packed red blood cells were returned to the fetus intravenously over 10 minutes. Each fetus received either furosemide (2 mg/kg) or control saline solution intravenously at time zero and again at 5 minutes. The order of experiments was randomly determined for each animal. Hemorrhage resulted in a similar decrease in fetal hematocrit in the two groups. The mean +/- SEM fetal hematocrit before hemorrhage was 38 +/- 3% in the furosemide group (n = 8) and 36 +/- 2% in the control group (n = 8). On day 2, the mean +/- SEM fetal hematocrit before transfusion was 28 +/- 2% in the furosemide group and 25 +/- 1% in the control group. There was no significant difference between groups in the fetal hemodynamic response to transfusion. At the end of the transfusion, the fetal central venous pressure had increased from 4.9 +/- 0.5 to 6.2 +/- 0.5 mm Hg in the furosemide group (p = 0.01) and from 3.9 +/- 0.2 to 5.8 +/- 0.3 mm Hg in the control group (p = 0.0001). Fetal mean arterial pressure increased from 42 +/- 1 to 50 +/- 1 mm Hg in the furosemide group (p = 0.0001) and from 40 +/- 1 to 46 +/- 1 mm Hg in the control group (p = 0.0007). Fetal heart rate decreased from 187 +/- 2 to 169 +/- 5 beats/min in the furosemide group (p = 0.004) and from 188 +/- 4 to 170 +/- 5 beats/min in the control group (p = 0.0008). Transfusion did not significantly change fetal pH in either group. At 120 minutes, the fetal PO2 had increased from 17 +/- 1 to 19 +/- 1 mm Hg in the furosemide group (p = 0.03) and from 19 +/- 1 to 21 +/- 2 mm Hg in the control group (p = 0.05). We conclude that rapid transfusion of the anemic fetal lamb resulted in modest increases in fetal central venous pressure and mean arterial pressure.(ABSTRACT TRUNCATED AT 400 WORDS)

Anemia, Hemolytic↗
PubMed1989

Effect of pregnancy on uterine and carotid artery response to norepinephrine, epinephrine, and phenylephrine in vessels with documented functional endothelium.

The effect of pregnancy on arterial sensitivity to vasoconstrictors is controversial. Some of the controversy may reflect methodologic differences. Vessel reactivity in vitro is altered by both the tension placed on the segment and the presence or absence of functional endothelium. We investigated the effect of pregnancy on guinea pig uterine and carotid arteries to norepinephrine, epinephrine, and phenylephrine. Each vessel segment was stretched to the optimal point along its length-tension curve, and functional endothelium was documented by acetylcholine-stimulated relaxation. A significant dose-response relationship was observed in each vessel for each agent (each p less than 0.0001). Pregnancy was demonstrated to be associated with a significant reduction in both uterine artery response and sensitivity to norepinephrine, epinephrine, and phenylephrine. However, there was no consistent pregnancy-associated effect on carotid artery response and sensitivity.

Animals↗
PubMed1989

The effect of intravenously administered 2-chloroprocaine upon uterine artery blood flow velocity in gravid guinea pigs.

The purpose of the present study was to assess the effect of intravenously administered 2-chloroprocaine upon uterine artery blood flow velocity (UBFV) in gravid guinea pigs. Ten experiments were performed in ten chronically instrumented animals between 0.7 and 0.9 of timed gestation. Each animal received four solutions of 2-chloroprocaine in random order: 1) 0.67 mg/kg; 2) 1.34 mg/kg; 3) 2.0 mg/kg; and 4) 1.34 mg/kg, with epinephrine 0.2 microgram/kg. Six animals received a fifth solution, 0.2 ml of saline control. 2-Chloroprocaine 1.34 mg/kg significantly increased maternal mean arterial pressure (MMAP) at 30 s after injection, and 2-chloroprocaine 2.0 mg/kg significantly increased MMAP through 2 min. 2-Chloroprocaine 1.34 mg/kg, with epinephrine 0.2 microgram/kg, also significantly increased MMAP through 2 min. No other solution significantly altered MMAP. 2-Chloroprocaine 2.0 mg/kg significantly decreased UBFV at 30 s after injection. 2-Chloroprocaine 1.34 mg/kg, with epinephrine 0.2 microgram/kg, significantly decreased UBFV through 2 min. No other solution significantly altered UBFV. The authors conclude that iv administration of 2-chloroprocaine with epinephrine significantly decreased UBFV in pregnant guinea pigs. In contrast, only the largest dose (i.e., 2.0 mg/kg) of 2-chloroprocaine alone transiently decreased UBFV. These data suggest that, in doses up to 1.34 mg/kg, 2-chloroprocaine alone may not decrease uterine blood flow when used as a marker for intravenous injection in obstetric patients.

Anesthetics, Local↗
PubMed1989

The influence of pH-adjusted 2-chloroprocaine on the quality and duration of subsequent epidural bupivacaine analgesia during labor: a randomized, double-blind study.

A randomized, double-blind study was performed to determine whether pH-adjustment of 2-chloroprocaine hastens the onset of epidural analgesia, and improves the quality and duration of subsequent epidural bupivacaine analgesia during labor. One milliliter of either 8.4% sodium bicarbonate or normal saline was added to a 30-ml vial of 2% 2-chloroprocaine. At 0, 5, and 7 min, each patient received 2, 5, and 3 ml of 2-chloroprocaine, respectively. At 22 min, any patient who did not yet have satisfactory analgesia received an additional 5 ml of 2-chloroprocaine. At 35, and, again, at 36 min, each patient received 5 ml of 0.25% bupivacaine. The median onset of 2-chloroprocaine analgesia was slightly more rapid in the bicarbonate group than in the saline-control group (12 versus 14 min, P less than .05). Two of 31 women in the bicarbonate group, versus 10 of 31 women in the saline-control group, required an additional 5 ml of 2-chloroprocaine at 22 min to achieve satisfactory analgesia (P = .01). There was no significant difference between groups in median duration of subsequent bupivacaine analgesia (60 min in each group) or mean (+/- SD) dosage of bupivacaine during the first stage of labor (64 +/- 43 versus 72 +/- 57 mg). Also, there was no significant difference between groups in pain scores over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia, Epidural↗
PubMed1989

Anesthetic management for obstetric hysterectomy: a multi-institutional study.

A prospectively designed review of all obstetric hysterectomies performed in five university hospitals between November 1, 1984 and October 31, 1987 has been performed. There were 41,107 deliveries and 46 obstetric hysterectomies, an incidence of 0.11%. Twenty-five hysterectomies were elective and 21 were emergent. The indication for 11 of the 21 emergency hysterectomies was placenta previa and/or accreta. Women in the emergency group had greater intraoperative blood loss, were more likely to have intraoperative hypotension, and were more likely to receive donor blood than women in the elective group (P less than 0.05). Twelve patients (eight from the elective group and four from the emergency group) received continuous epidural anesthesia, and none required intraoperative induction of general anesthesia. There was no evidence that epidural anesthesia significantly affected blood loss, crystalloid replacement, or requirement for transfusion in the elective group. Abnormal placentation now represents a major indication for emergency obstetric hysterectomy. Furthermore, significant hemorrhage is more likely with emergency obstetric hysterectomy than with elective hysterectomy. Finally, elective cesarean hysterectomy is not a contraindication to performance of continuous epidural anesthesia.

Adult↗
PubMed1989

Subdural injection of local anesthetics and morphine: a complication of attempted epidural anesthesia.

We have reported a case of unintentional, roentgenographically proven cannulation of the lumbar subdural space. Injection of 13 ml of local anesthetic provided satisfactory anesthesia for cesarean section, and administration of 1 mg of morphine resulted in postcesarean analgesia for 22 hours. Subdural catheterization is a possible explanation for the occasionally irregular course of an apparent "epidural" anesthetic.

Adult↗
PubMed1989

Metoclopramide versus droperidol for prevention of nausea and vomiting during epidural anesthesia for cesarean section.

In a randomized, double-blind study, we compared the efficacy of metoclopramide hydrochloride with that of low-dose droperidol for prevention of nausea and vomiting during and after elective cesarean section with epidural anesthesia. Immediately after the umbilical cord was clamped, each patient received fentanyl (50 micrograms) and the study drug intravenously over 30 to 60 seconds. In one study group, 40 women received metoclopramide (15 mg); in the other group, 41 women received droperidol (0.5 mg). Twelve women (30%) in the metoclopramide group, versus eight (20%) in the droperidol group, had intraoperative, postdelivery nausea (P = NS). One woman (3%) in the metoclopramide group, versus two women (5%) in the droperidol group, had intraoperative, postdelivery vomiting (P = NS). During the first four postoperative hours, five women (12%) in each group complained of nausea. Three women (7%) in each group had postoperative vomiting. We conclude that metoclopramide (15 mg) and droperidol (0.5 mg) were similarly effective.

Adult↗
PubMed1988

Does the intravenous infusion of ritodrine or magnesium sulfate alter the hemodynamic response to hemorrhage in gravid ewes?

The purpose of this study was to determine whether the intravenous infusion of ritodrine or magnesium sulfate alters the hemodynamic response to maternal hemorrhage in gravid ewes. Twenty-seven experiments were performed in 12 chronically instrumented animals at 0.8 of timed gestation. Each animal was subjected to hemorrhage (20 ml/kg over 60 minutes) during infusion of ritodrine (0.004 mg/kg/min), magnesium sulfate (4 gm/hour), or saline solution control. Infusion of magnesium sulfate increased the mean (+/- SEM) maternal serum magnesium concentration to 4.8 +/- 0.2 mg/dl before hemorrhage and 5.3 +/- 0.3 mg/dl after hemorrhage. At the end of hemorrhage maternal mean arterial pressures were 63% +/- 4%, 82% +/- 2%, and 79% +/- 6% of baseline in the magnesium sulfate, ritodrine, and control groups, respectively. The maternal mean arterial pressure response in the magnesium sulfate group differed significantly from the maternal mean arterial pressure responses in the ritodrine and control groups (p less than 0.01). Fetal pH was decreased significantly only in the magnesium sulfate group (p = 0.0001). Fetal PO2 was decreased significantly in the magnesium sulfate and ritodrine groups (p less than 0.001) but not in the control group. We conclude that magnesium sulfate but not ritodrine, worsened the maternal hypotensive response to hemorrhage in gravid ewes.

Animals↗