Term Pregnant Patients Research Articles

Immortalization and characterization of human myometrial cells from term-pregnant patients using a telomerase expression vector.

An examination of cellular processes involved in myometrial function has been greatly assisted by the use of human myometrial cells in primary culture. However, these cells can be used only for several passages before they senesce, and responses to various agents change with time in culture. The use of transformed cells is limited, as they can be polynucleated and can lose or gain chromosomes. We have developed three telomerase-immortalized cell lines from term-pregnant human myometrium to eliminate variability between passage numbers and allow genetic manipulations of myometrial cells to fully characterize signal pathways. These cells have a normal karyotype and were verified to be uterine smooth muscle by immunocytochemical staining for smooth muscle cell-specific alpha-actin and high affinity oxytocin antagonist binding sites. The three cell lines and the cells in primary culture from which they were derived were examined by cDNA microarray analysis. Of >10 000 expressed genes, there were consistent changes in the expression of approximately 1% in the three immortalized cell lines. We were unable to detect any significant differences between primary and immortalized cells in signal pathways such as epidermal growth factor-stimulated epidermal growth factor receptor phosphorylation, insulin-stimulated Akt phosphorylation, oxytocin and lysophosphatidic acid-stimulated extracellular signal-regulated kinase 1 and 2 phosphorylation, myosin light chain phosphorylation, and interleukin-1 induction of IkappaBalpha degradation. The immortalized cells should be useful for a range of studies, including high throughput analyses of the effects of environmental agents on the human myometrium.

Inducción electiva ambulatoria del trabajo de parto con misoprostol en pacientes de bajo riesgo: estudio clínico controlado

Introducción: la inducción electiva permite al obstetra intervenir en el embarazo a término de bajo riesgo, y tratar de disminuir potenciales efectos adversos y la ansiedad materna que puedan complicar el embarazo. El objetivo de esta investigación es determinar la seguridad y eficacia del misoprostol en la inducción electiva ambulatoria del trabajo de parto en pacientes con embarazo a término de bajo riesgo que acuden a la ESE, Clínica de Maternidad Rafael Calvo de Cartagena, Colombia.Metodología: se realizó un ensayo clínico con asignación aleatoria y controlado con placebo en pacientes embarazadas a término de bajo riesgo, que consultaron a la ESE en el período comprendido entre el 1 mayo de 2002 y el 1 de marzo de 2004; aquellas que cumplieron con los criterios de selección fueron distribuidas en tres grupos para recibir misoprostol hospitalario, ambulatorio y placebo. Los resultados se analizaron con ANOVA de dos vías para las variables continuas y Chi cuadrado en variables cualitativas.Resultados: ingresaron 20 pacientes en el grupo hospitalario, 20 en el grupo ambulatorio y seis en el grupo placebo. Hubo un menor tiempo en el inicio del trabajo de parto en el grupo de misoprostol ambulatorio. La incidencia de efectos adversos no fue relevante en los tres grupos.Conclusión: el misoprostol utilizado en la inducción electiva ambulatoria del parto es seguro y eficaz.

Thrombopoietin in normal pregnancy and preeclampsia

OBJECTIVE: In normal pregnancy and pregnancies complicated by preeclampsia it has been demonstrated that there is increased activation of platelets and the clotting and fibrinolytic system. We measured plasma levels of thrombopoietin, a major regulator of platelet production in these conditions. STUDY DESIGN: We compared the thrombopoietin plasma levels of healthy term pregnant patients ( n = 21) with those of healthy nonpregnant controls ( n = 17), as well as patients with severe preeclampsia ( n = 8) and the hemolysis, elevated liver enzymes, low platelets syndrome ( n = 6). RESULTS: Thrombopoietin levels in normal pregnant patients and pregnancies complicated by the hemolysis, elevated liver enzymes, low platelets syndrome were statistically significantly higher than thrombopoietin levels in nonpregnant controls. Data were analyzed with the Kruskal-Wallis one-way analysis of variance by ranks. CONCLUSIONS: This study is the first to report thrombopoietin levels in pregnancy. Thrombopoietin levels are significantly greater in pregnant patients and in pregnancies complicated by the hemolysis, elevated liver enzymes, low platelets syndrome compared with nonpregnant controls. (Am J Obstet Gynecol 1998;179:100-4.)

Three-Dimensional Method for Determination of Amniotic Fluid Volume in Intrauterine Pockets

Background: Although current ultrasound techniques provide a linear (amniotic fluid index; AFI) or two-dimensional area index of amniotic fluid (AF), these indices have limited correlation with actual AF volume. We sought to quantify the three-dimensional volume of ultrasound-identified AF pockets, as assessed by the AFI and two-dimensional area methods. The BVI 2500 (Bladder Volume Instrument 2500; Diagnostic Ultrasound Corp., Redmond, WA) has been used to quantify the volume of residual urine in the bladder.Instrument and Method: The BVI 2500 (Diagnostic Ultrasound Corp.) ultrasound uses a rotating 2-MHz transducer, computer-defined fluid interface, and computer integration of 12 cross-sectional images to calculate three-dimensional fluid volume. After providing written informed consent, 14 term pregnant patients (36–42 weeks) were evaluated using the BVI 2500 and an Ultramark 8 sector scan (Advanced Technology Laboratory, Bothell, WA). The largest vertical fluid pocket in each quadrant of the abdomen was identified with the sector scan, and vertical and horizontal measurements for AFI and two-dimensional area were recorded. Simultaneous AF volume measurements of each pocket were performed three times with the bladder volume instrument, and maximum values were used. Three-dimensional volume, two-dimensional area, and AFI values were compared by correlation analysis, with P ≤ .05 considered statistically significant.Experience: Among all patients, the average (± standard deviation) AFI was 7.6 ± 4.1 (range 1.5–16.4) cm, and the average two-dimensional area was 30.9 ± 21.1 (range 4.3–81.3) cm2. This corresponded to an average three-dimensional volume of 215 ± 134 (range 23–497) cm3. Three-dimensional volume correlated highly with both AFI (r = 0.9; P < .001) and two-dimensional area (r = 0.86; P < .001). One AFI centimeter was equivalent to a volume of 30 cm3.Conclusion: There are highly significant linear correlations of three-dimensional amniotic fluid volumes with AFI and two-dimensional area. The four pockets used in AFI determination account for only 50% of total AF volume. Three-dimensional determinations may aid in clinical assessments of AF volume.

Intrathecal Neostigmine for Post-Cesarean Section Analgesia

Intrathecal (IT) neostigmine produces analgesia in animals and humans and enhances systemic opioid analgesia.To examine the safety of IT neostigmine for eventual use in obstetrics, we studied 24 healthy, term pregnant patients scheduled to receive elective cesarean section using a combined spinal-epidural anesthetic. Using an open-label, dose-ranging design, patients received either IT placebo or neostigmine 10, 30, or 100 micro g in a 1-mL solution of 5% glucose in normal saline followed in 15 min by 2% epidural lidocaine for cesarean section. Neostigmine did not affect fetal heart rate tracings or Apgar scores. The women received patient-controlled analgesia intravenous morphine postoperatively. Compared with the glucose control, neostigmine produced a dose-independent reduction in postoperative morphine use. Cumulative average 24-h morphine use was 82 +/- 7 mg for women receiving IT placebo and 50 +/- 8 mg for women receiving IT neostigmine (P < 0.003). Hourly morphine use was significantly reduced in the neostigmine groups for 10 h postoperatively. These data indicate that IT neostigmine can produce 10 h of post-cesarean section analgesia without adverse fetal effects and support cautious further prospective study. (Anesth Analg 1997;84:1269-75)

Influence of Anthropometric Variables on the Spread of Epidural Anesthesia

To the Editor: Previous studies performed during general surgery or cesarean section reported [1,2] or refuted [3,4] the influence of anthropometric variables such as height, weight, and age on the spread of epidurally administered anesthetics. In term pregnant patients, a reduction of volume injected is usually recommended [1], and considerable volume ranges have been reported to block a fixed dermatomal level. To improve the safety of epidural anesthesia used for cesarean section, we investigated the influence of other anthropometric variables on the spread of epidural anesthesia. Footprints have been used by paleontologists for retrospective anthropometric analysis of the human skeleton [5], and skeletal measurement has been used by De Nguyen et al. [6] to determine ideal body weight. Sixty ASA grade I consenting near-term pregnant patients, after approval from the hospital ethical committee, were included in this study. Height, weight before pregnancy, weight before anesthesia, the length of the foot from the tip of the first toe to the back of the heel, and wrist perimeter were recorded. Body mass index (BMI) was calculated (BMI = weight in kg/height in m2). Epidural puncture was performed with the patient in the sitting position via the midline approach at the L2-3 interspace. After negative aspiration and negative results from a 3-mL test dose (2% lidocaine with epinephrine 1/80,000), 15 mL of lidocaine 1.6%, with epinephrine 1/200,000, and fentanyl 100 micro gram were injected through a catheter inserted 3 cm into the epidural space. The upper level of anesthesia was determined by absence of pain in response to pinprick and was correlated to anthropometric variables using a Spearman test. Twenty percent of patients were obese according to BMI (>30 using the weight at term). Despite the same volume injected, the upper level of anesthesia ranged from T10 to T1 Figure 1. The mean number of blocked spinal segments at maximum extent of anesthesia was 17 +/- 1.6 SD. The only anthropometric measurement to correlate with the level of block was age (r = 0.39; P < 0.003). The block was adequate for cesarean section in 58 of 60 patients.Figure 1: Number of parturients (n) for each upper level of anesthesia (T = thoracic) obtained after injection of 15 mL lidocaine 1.6% in the epidural space.In conclusion, only age was found to correlate with the spread of anesthesia, but its coefficient of determination, r2 = 0.16, indicates that this variable is not more useful than those previously published. In this group, we failed to demonstrate any benefit of using new variables such as wrist perimeter or foot length on the spread of epidural anesthesia. Despite the use of a standardized technique, there was a large variation in the spread of anesthesia, and several uncontrollable factors affect the spread of local anesthetic within the epidural space. D. Chassard, MD J. Krichen, MD K. R. Berrada, MD M. Guiraud, MD B. Bryssine, MD P. Bouletreau, MD Anesthesia Department, Hotel Dieu, 69002 Lyon, France

Influence of Anthropometric Variables on the Spread of Epidural Anesthesia

To the Editor: Previous studies performed during general surgery or cesarean section reported [1,2] or refuted [3,4] the influence of anthropometric variables such as height, weight, and age on the spread of epidurally administered anesthetics. In term pregnant patients, a reduction of volume injected is usually recommended [1], and considerable volume ranges have been reported to block a fixed dermatomal level. To improve the safety of epidural anesthesia used for cesarean section, we investigated the influence of other anthropometric variables on the spread of epidural anesthesia. Footprints have been used by paleontologists for retrospective anthropometric analysis of the human skeleton [5], and skeletal measurement has been used by De Nguyen et al. [6] to determine ideal body weight. Sixty ASA grade I consenting near-term pregnant patients, after approval from the hospital ethical committee, were included in this study. Height, weight before pregnancy, weight before anesthesia, the length of the foot from the tip of the first toe to the back of the heel, and wrist perimeter were recorded. Body mass index (BMI) was calculated (BMI = weight in kg/height in m2). Epidural puncture was performed with the patient in the sitting position via the midline approach at the L2-3 interspace. After negative aspiration and negative results from a 3-mL test dose (2% lidocaine with epinephrine 1/80,000), 15 mL of lidocaine 1.6%, with epinephrine 1/200,000, and fentanyl 100 micro gram were injected through a catheter inserted 3 cm into the epidural space. The upper level of anesthesia was determined by absence of pain in response to pinprick and was correlated to anthropometric variables using a Spearman test. Twenty percent of patients were obese according to BMI (>30 using the weight at term). Despite the same volume injected, the upper level of anesthesia ranged from T10 to T1 Figure 1. The mean number of blocked spinal segments at maximum extent of anesthesia was 17 +/- 1.6 SD. The only anthropometric measurement to correlate with the level of block was age (r = 0.39; P < 0.003). The block was adequate for cesarean section in 58 of 60 patients.Figure 1: Number of parturients (n) for each upper level of anesthesia (T = thoracic) obtained after injection of 15 mL lidocaine 1.6% in the epidural space.In conclusion, only age was found to correlate with the spread of anesthesia, but its coefficient of determination, r2 = 0.16, indicates that this variable is not more useful than those previously published. In this group, we failed to demonstrate any benefit of using new variables such as wrist perimeter or foot length on the spread of epidural anesthesia. Despite the use of a standardized technique, there was a large variation in the spread of anesthesia, and several uncontrollable factors affect the spread of local anesthetic within the epidural space. D. Chassard, MD J. Krichen, MD K. R. Berrada, MD M. Guiraud, MD B. Bryssine, MD P. Bouletreau, MD Anesthesia Department, Hotel Dieu, 69002 Lyon, France

Surgeon-controlled mivacurium administration during elective Caesarean section

We have compared the dose requirements and recovery characteristics of a continuous mivacurium infusion given by the anaesthetist to maintain 95-100% block at the hand muscles with that of a surgeon-controlled, on-demand dosing technique based on the direct assessment of abdominal muscle tone during elective Caesarean section. Twenty-four full term pregnant patients were included. A rapid-sequence induction using thiopentone 3-5 mg.kg-1 and succinylcholine 1 mg.kg-1 was used. Anaesthesia was maintained with fentanyl, N2O and isoflurane 0.5%. The mechanomyographic response of the adductor pollicis muscle to supramaximal train-of-four (TOF) ulnar nerve stimulation was recorded. Muscle relaxation was achieved initially with mivacurium 0.1 mg.kg-1 followed either by a continuous infusion of mivacurium to maintain 95-100% block at the adductor pollicis muscle (n = 12) or by surgeon-controlled relaxation (SCR) technique using a syringe pump for patient-controlled analgesia to administer on-demand doses of mivacurium 0.05 mg.kg-1 (n = 12). The lockout interval was three minutes and the maximum hourly dose of mivacurium allowed was 0.6 mg.kg-1. The total doses of mivacurium (mean +/- SD) were 23.2 +/- 10.4 and 12.4 +/- 3.5 mg in the infusion and SCR groups, P < 0.01. On-demand, surgeon-controlled doses of mivacurium were injected at a mean of T1 42.3 +/- 36%. At the end of surgery, T1 and TOF ratio were respectively 16.7 +/- 13%, 5 +/- 10% and 48 +/- 37%, 30 +/- 24% in the infusion and SCR groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Vertebral column length and spread of hyperbaric subarachnoid bupivacaine in the term parturient.

Patient height is considered an important determinant of the dose of spinal anesthesia. However, the relationship between body height and the level of sensory anesthesia with a fixed dose of spinal anesthetic has not been clearly documented. Recent evidence suggests no correlation between height or weight of parturients and spread of spinal anesthesia. Vertebral column length rather than body height may be more important in determining anesthetic spread. We studied the correlation between vertebral length measured from C7 to the level of the iliac crest (IC) and to the sacral hiatus (SH) and the sensory anesthetic level after the subarachnoid administration of 12 mg hyperbaric bupivacaine in term pregnant patients. There was no correlation between patient height, weight or body mass index and sensory anesthesia level. However, a significant correlation existed between vertebral length measured from C7 to IC (r = 0.32, p = 0.025) or to SH (r = 0.38, p = 0.006) and the level of anesthesia.

Pre-Eclamptic and Healthy Term Pregnant Patients Have Different Chronotropic Responses to Isoproterenol

Pre-Eclamptic and Healthy Term Pregnant Patients Have Different Chronotropic Responses to Isoproterenol

Pre-Eclamptic and Healthy Term Pregnant Patients Have Different Chronotropic Responses to Isoproterenol

Assistant Professor of AnesthesiologyAssociate Professor of AnesthesiologyInstructor in AnesthesiologyAssistant Professor in Obstetrics and GynecologyProfessor of Pharmacology (Biostatistics) Department of Anesthesiology Jefferson Medical College 111 South 11th Street Philadelphia, Pennsylvania 19107

Cardiac output in women undergoing cesarean section with epidural or general anesthesia

Cardiac output during cesarean section and for 24 hours after delivery was estimated by using a noninvasive ultrasonic Doppler technique and was compared between term pregnant patients who underwent either epidural or general anesthesia. Cardiac output peaked by 36.7% and 26.3% of baseline values at 15 and 30 minutes after delivery, respectively, with epidural anesthesia and by 28% and 17.2%, respectively, with general anesthesia. From 60 minutes to 24 hours after delivery, cardiac output in both groups remained elevated at preoperative levels. This study demonstrates a similar pattern of increase in cardiac output with epidural and general anesthesia and a return by 60 minutes to preoperative levels, which persisted for up to 24 hours after delivery. The applicability of this noninvasive technique can be extended in various circumstances during pregnancy, labor, delivery, and the postpartum period to further define cardiac output in pregnancy. (Am J Obstet Gynecol 1989;160:1178-84.)

Sinusoidal Fetal Heart Rate Pattern Associated with Butorphanol Administration

One hundred nineteen fetal heart rate monitor tracings from term-pregnant patients in labor were reviewed by two independent observers to test the hypothesis that Stadol administration to mothers does not result in sinusoidal fetal heart rate pattern. There was agreement with regard to the interpretation of the tracings in 106 instances. Fifty-one patients received intravenous Stadol for narcotic analgesia. Seventy-five percent of these patients demonstrated a transient sinusoidal fetal heart rate pattern after Stadol administration. In a small number of patients, this pattern recurred either with or without additional Stadol treatment. In contrast, patients who did not receive Stadol therapy (N = 55) demonstrated a significantly lower incidence of sinusoidal fetal heart rate pattern (13%), the duration of which was significantly shorter than that seen in the former group. From these we conclude that Stadol therapy during labor is strongly associated with the appearance of sinusoidal fetal heart rate pattern. There were no short-term maternal or neonatal adverse sequelae. In the absence of other fetal heart rate signs suggestive of fetal distress, the presence of sinusoidal fetal heart rate pattern after Stadol administration does not indicate fetal hypoxia.

The effect of endocervical PGE 2-gel (Prepidil™) gel on plasma levels of 13,14-dihydro-15-keto-PGE 2 (PGEM) in women at term

Term pregnant patients undergoing preinduction cervical softening were randomized to receive no treatment (controls) or 0.5 mg PGE 2-triacetin gel (Prepidil™ gel) endocervically. Plasma samples containing PGEM collected 4 hrs post-treatment and converted to the stable bicyclo degradation product (bicyclo-PGEM) were assayed by RIA. Positive clinical effect (responders) during 12 hrs after treatment (Bishop score increase≥3, in labor or delivered) were assessed. All evaluations were blind. In nonresponders (n=35), the means of the bicyclo-PGEM variables (mean, maximum, area under the curve) were all about 18% higher in gel-treated patients (n=6) than controls (n.s.). In responders (n=38), the variables were all about 80% higher in gel-treated women (n=32) than controls (p<.01). In controls (n=35), the responders (n=6) had 50% higher levels than nonresponders (n.s.). In the gel-treated women (n=38), responders (n=32) had about 140% higher levels than nonresponders (<.01). The results suggest that both exogenous and endogenous bicyclo-PGEM were measured. Differences in pairwise comparisons suggest that there may be substantially less exogenous bicyclo-PGEM in the gel nonresponders than in gel responders or substantially more endogenous bicyclo-PGEM in gel responders than in control-responders.

Succinylcholine Pharmacodynamics in Peripartum Patients

Leighton, B. L.; Cheek, T. G.; Gross, J. B.; Apfelbaum, J. L.; Shantz, B. B.; Gutsche, B. B.; Rosenberg, H. Author Information

Succinylcholine pharmacodynamics in peripartum patients.

Serum cholinesterase activity decreases 30% during pregnancy and remains depressed during the postpartum period. However, succinylcholine recovery is not prolonged in term-pregnant patients. This contrasts with results obtained in other patients with decreased serum cholinesterase activity. To better understand this paradox, the authors compared serum cholinesterase activity and recovery from succinylcholine, 1 mg/kg, in nonpregnant (with and without oral contraceptive use), in term-pregnant, and in postpartum patients. Serum cholinesterase activity was lower in both term-pregnant (3.66 +/- 0.39 U/ml, means +/- SE) and postpartum (2.84 +/- 0.35 U/ml) patients than in nonpregnant patients not taking oral contraceptives (5.01 +/- 0.33 U/ml, P less than 0.05). Cholinesterase activity in postpartum patients also was significantly lower than in nonpregnant patients taking oral contraceptives (4.81 +/- 0.63, P less than 0.05). In contrast, the time to 25% twitch-height recovery did not differ between term-pregnant (470 +/- 56 s) and nonpregnant patients taking (499 +/- 29 s) or not taking (501 +/- 21 s) oral contraceptives, but was significantly increased in postpartum patients (685 +/- 22 s, P less than 0.001). The similar duration of action of succinylcholine in term-pregnant patients (with decreased serum cholinesterase activities) and nonpregnant patients may be related to the increased volume of distribution of succinylcholine at term.

Bioconversion of arachidonic acid in human pregnant uterine cervix.

The in vitro conversion of [14C]arachidonic acid by endocervical mucosa and cervical tissue specimens obtained in first trimester (9-12 w) and term pregnant patients (37-39 w) was studied in whole-cell homogenates. All radiolabelled products of the arachidonic acid cascade were extracted, purified and separated utilizing silicic acid chromatography, thin-layer chromatography and reversed phase partition chromatography and identified with radio-gas chromatography and gas chromatography-mass spectometry. Both types of tissue produced PGF2 alpha and PGE2, as well as TxB2. In cervical tissue specimens there was a significant increase in the production of all these three prostaglandins as the pregnancy progressed, whereas no such difference was seen in homogenates of endocervical mucosa. In both endocervical mucosa and cervical tissue specimens there was a highly significant increase in the production of a so-far unknown compound(s), in samples from term patients as compared with samples from first-trimester patients. The possible participation of this metabolite of [14C]arachidonic acid in the regulation of cervical ripening is discussed.

Antioxytocic and antiprostaglandin-releasing effects of oxytocin antagonists in pregnant rats and pregnant human myometrial strips.

There is now increasing evidence that both oxytocin (OT) and prostaglandin (PG) play a role in term as well as preterm labor. OT stimulates myometrial contractions and uterine PG release. Specific OT antagonists, therefore, may be of value in the treatment of preterm labor. Recently, we have synthesized two highly potent OT antagonists, [1-penicillamine, 4-threonine]OT ([Pen1, Thr4]OT) and [1-penicillamine, 2-phenylalanine, 4-threonine]OT ([Pen1, Phe2, Thr4]OT). We have determined their antioxytocic activity in 21- to 22-day-pregnant rats and on isolated human myometrial strips obtained from term pregnant patients at caesarean section for childbirth. We also studied their effects on PG synthesis and OT-stimulated PG synthesis on uterine slices from pregnant rats. We found that the two OT antagonists were effective inhibitors of the OT responses in pregnant rats and on pregnant human myometrial strips. The two OT antagonists had no agonistic activity on PG release at a dose range that was antioxytocic. When administered together with OT, the PG-releasing action of OT was inhibited. Thus, [Pen1, Thr4]OT and [Pen1, Phe2, Thr4]OT are effective inhibitors of both the uterotonic and PG-releasing actions of OT. The potentials of OT antagonists as tocolytic agents for the treatment of preterm labor should be explored.

Epidural space pressures during pregnancy

The epidural space pressure in the lumbar region was monitored and recorded in 21 full term pregnant patients, before and during labour and 6-12 hours postpartum, in different positions. The pre-labour epidural pressure was found to be above atmospheric in all patients, being highest when supine, and lowest in the lateral position. Three patients with twin pregnancy showed a greater rise in epidural space pressure in the supine position even with the use of lateral tilt, compared with patients with single fetus pregnancy. It is suggested that the epidural space pressure in the full term pregnant patient is closely related to the degree of inferior vena caval obstruction imposed by the gravid uterus. It is also suggested that when the patient is aware of a uterine contraction, the synchronous rise of the epidural space pressure with the contraction is a result of reflex increase in abdominal muscle tone. With established epidural block, and the parturient unaware of a contraction, such a rise was minimal, and was replaced by a drop in pressure in patients with a single fetus who developed loss of muscle power. The magnitude of the drop in the epidural space pressure immediately after delivery was found to be related to the duration of labour and to the mode of delivery. Epidural pressures measured 6-12 hours after delivery were comparable in all patients.

Lumbar epidural anaesthesia and sensory profiles in term pregnant patients.

Sensory profiles of lumbar epidural anaesthesia were studied in 57 patients, during active labour. The local anaesthetics used were chloroprocaine three per cent with and without epinephrine, chloroprocaine two per cent, bupivacaine 0.25 per cent and a mixture of chloroprocaine three per cent and bupivacaine 0.5 per cent. A common pattern of spread was found for all local anaesthetic solutions with the onset of the block affecting the dermatomes innervated by the thinnest nerve roots (T12L1). There was a percentage of failure to block the thickest nerve root (S1). Inguinal and suprapubic discomfort ("missing segment") occurred when S1 was not blocked. Under the conditions of this experiment, the addition of bupivacaine to chloroprocaine did not increase the duration of the blockade significantly.