Intrathecal meperidine for labor analgesia: preliminary communication

The authors administered intrathecal meperidine 10 mg to 10 healthy laboring women to determine its analgesic quality, onset, duration, and side-effect profile. When patients requested pain relief, we injected 10 mg preservative-free meperidine in 1 ml normal saline through a 32 gauge spinal catheter. We administered a second dose of meperidine 10 mg if analgesia was inadequate at 10 min. Additional doses of intrathecal meperidine or bupivacaine were administered on request. All patients received local anesthetic intrathecally or by infiltration for delivery. Eight patients were pain-free following meperidine 10 mg, the other 2 patients were comfortable after the second 10 mg meperidine dose. Three patients did not request further labor analgesics and delivered 58, 66 and 244 min following their initial injection of intrathecal meperidine. The mean duration of analgesia in the other 7 patients was 136 +/- 58 (mean +/-SD) min. Six of the 10 women in the study delivered vaginally; 3 spontaneously and 3 with vacuum or forceps assistance. Four patients delivered by cesarean section for failure to progress. Side-effects (which were easily treated) consisted of: pruritus (n = 1), vomiting (n = 2), hypotension (n = 2) and changes in fetal heart rate pattern (n = 5). All infants were vigorous and had good Apgar scores at birth. In conclusion, intrathecal meperidine is a promising labor analgesic, but the effect of meperidine on maternal blood pressure, fetal heart rate pattern, and the progress of labor need to be determined.

Are combined spinal-epidural catheters reliable?

The combined spinal-epidural (CSE) technique can rapidly relieve labor pain. However, the location of the epidural catheter is initially uncertain. In an emergency, this untested catheter may fail to provide adequate anesthesia. This study compared the efficacy of catheters placed as a part of an epidural or needle-though-needle CSE technique in laboring women. Patients requesting pain relief received either epidural (n=601) or CSE (n=1061) analgesia. All patients had a 20 gauge, closed tip multi-holed polyamide catheter. (B. Braun Medical, Inc.) inserted 2-8 cm into the epidural space. Catheters were tested to rule out intrathecal and intravascular location. Then, epidural patients received 10-20 ml local anesthetic +/- opioid in divided doses. CSE patients received and infusion of 0.083% bupivacaine with opioid at 10-15 ml/h. Of the 1495 catheters that were adequately tested, those inserted as part of a CSE technique were more likely to produce bilateral sensory change and adequate analgesia than were those inserted without prior spinal analgesia (98.6% vs 98.2%, P<0.02). Stand-alone epidural catheters were more likely to produce neither sensory change nor analgesia than those inserted as part of CSE technique (1.3% vs 0.2%, P<0.02). The only catheters that failed completely and were not intravascular were stand-alone epidural catheters. In this clinical setting, catheters inserted as part of a CSE technique had a high probability of being in the epidural space and functioning appropriately.

Blocks of limited haplotype diversity revealed by high-resolution scanning of human chromosome 21

Global patterns of human DNA sequence variation (haplotypes) defined by common single nucleotide polymorphisms (SNPs) have important implications for identifying disease associations and human traits. We have used high-density oligonucleotide arrays, in combination with somatic cell genetics, to identify a large fraction of all common human chromosome 21 SNPs and to directly observe the haplotype structure defined by these SNPs. This structure reveals blocks of limited haplotype diversity in which more than 80% of a global human sample can typically be characterized by only three common haplotypes.

Combined spinal-epidural versus epidural labor analgesia

BACKGROUND

Despite the growing popularity of combined spinal-epidural analgesia in laboring women, the exact role of intrathecal opioids and the needle-through-needle technique remains to be determined. The authors hypothesized that anesthetic technique would have little effect on obstetric outcome or anesthetic complications.

METHODS

Data were prospectively collected from 2,183 laboring women randomly assigned to have labor analgesia induced with either 10 microg intrathecal sufentanil with or without 2.0 mg bupivacaine (n = 1,071) or 10 microg epidural sufentanil and 12.5-25.0 mg bupivacaine (n = 1,112). Immediately after induction, a continuous epidural infusion of 0.083% bupivacaine plus 0.3 microg/ml sufentanil was begun in all patients and continued until delivery. Labor was managed by nurses, obstetricians, and obstetric residents who were unaware of the anesthetic technique used.

RESULTS

Anesthetic technique lacked impact on our primary outcome: mode of delivery or labor duration. Infants whose mothers were allocated to the combined spinal-epidural group had a slightly higher umbilical artery carbon dioxide partial pressure (54.2 +/- 10.4 vs. 53.2 +/- 10.2 mmHg). However, only achieving at least 5 cm cervical dilation before induction of analgesia and having a cesarean delivery were independent risk factors for elevated umbilical artery carbon dioxide partial pressure. The frequencies of accidental dural puncture, failed epidural analgesia, headache, and epidural blood patch were low and similar in the two groups.

CONCLUSIONS

Labor progress and outcome are similar among women receiving either combined spinal-epidural or epidural analgesia. The difference in neonatal outcome appears related to the presence of confounding variables. The combined spinal-epidural technique is not associated with an increased frequency of anesthetic complications. Either technique can safely provide effective labor analgesia.

Does epinephrine improve the diagnostic accuracy of aspiration during labor epidural analgesia?

Aspiration reliably detects almost all IV multiorifice epidural catheters. Although a supplemental epinephrine 15-microg test dose may detect the rare IV catheter that does not yield blood on aspiration, false-positive epinephrine responses may cause some women to unnecessarily undergo repeat epidural catheter insertion. We evaluated 532 consecutive eligible patients requesting neuraxial labor analgesia. Patients were excluded if they had a contraindication to epinephrine or if they received intrathecal sufentanil/bupivacaine. Multiorifice catheters were inserted 4-6 cm into the epidural space as part of an epidural (n = 305) or combined spinal-epidural (n = 270) technique. We used aspiration, a lidocaine/epinephrine test dose, and bolus injection or infusion of dilute bupivacaine/sufentanil solutions to systematically determine IV, intrathecal, or epidural catheter location. Aspiration alone detected 47 of 48 intravascular catheters. There were 10 positive epinephrine responses: 2 were true positives, 7 were falsely positive (subsequent local anesthetic injection/infusion produced bilateral sensory change and analgesia), and 1 catheter was removed without further testing. Aspiration detected almost all intravascular catheters. Although the epinephrine test dose did detect one catheter that proved to be in a blood vessel, 87.5% of positive responses occurred in women without intravascular catheters.

IMPLICATIONS

Epidural catheters may enter a blood vessel. Many clinicians use epinephrine to detect these catheters. Because aspiration alone detects almost all IV multiorifice catheters in laboring women, a subsequent epinephrine test dose may be unnecessary.

Anesthesia for reduction of uterine incarceration: report of two cases

We present two cases in which anesthesia was needed for the reduction of uterine incarceration. The first case was managed with a combined spinal/epidural technique and the second with a single intrathecal injection of opioid and low dose local anesthetic. The anesthetic issues pertinent to the reduction of an incarcerated uterus are discussed and the literature briefly reviewed.

The influence of epidural needle bevel orientation on spread of sensory blockade in the laboring parturient

Both asymmetrical sensory blockade and dural puncture are undesirable outcomes of epidural analgesia. Identifying the epidural space with the needle bevel oriented parallel to the longitudinal axis of the patient's back limits the risk of headache in the event of dural puncture. However, rotating the bevel to direct a catheter cephalad may risk dural puncture. We prospectively studied the effects of needle rotation on the success of labor epidural analgesia and on the incidence of dural puncture. One hundred sixty ASA physical status I or II laboring parturients were randomly assigned to one of four groups. The epidural space was identified with the bevel of an 18-gauge Hustead needle directed to the patient's left. It was then rotated as follows: Group 0 = no rotation, final bevel orientation left (n = 39); Group 90 = rotation 90 degrees clockwise, bevel cephalad (n = 43); Group 180 = rotation 180 degrees clockwise, bevel right (n = 36); Group 270 = rotation 270 degrees clockwise, bevel caudad (n = 42). A single-orifice catheter was inserted 3 cm, and analgesia was induced in a standardized fashion. Dural puncture was evenly distributed among the groups (4.4%). There were more dermatomal segments blocked, fewer one-sided blocks, and more patients comfortable at 30 min with the needle bevel directed cephalad. Using a catheter inserted through a needle oriented in the cephalad direction increases the success of epidural analgesia.

IMPLICATIONS

This prospective study shows that an epidural catheter inserted through a needle oriented in the cephalad direction increases the success of labor analgesia in the parturient. Carefully rotating the needle cephalad does not increase the risk of dural puncture, intravascular catheters, or failed blocks.

Intrathecal sufentanil dose response in nulliparous patients

BACKGROUND

Intrathecal sufentanil provides effective analgesia during the first stage of labor. A range of doses has been reported to provide adequate pain relief. This study determined the dose of intrathecal sufentanil that produced acceptable pain relief in 50% of nulliparous patients (ED50) who requested labor analgesia.

METHODS

With institutional review board approval, 50 nulliparous patients requesting spinal opioid labor analgesia were enrolled into this prospective, randomized, double-blinded study. Each patient was in spontaneous labor at <5 cm cervical dilation. Patients received one of the following doses of intrathecal sufentanil: 1, 2, 3, 5, or 10 microg in 3 ml preservative-free saline (n = 10 for each dose). Pain, pain relief, hemodynamic, respiratory, and side effect data were collected at times 0, 2, 5, 10, 15, 20, 25, and 30 min. Probit analysis of the number of patients in each group who requested additional pain medicine at 30 min was used to determine the ED50.

RESULTS

The groups were demographically similar. The ED50 of intrathecal sufentanil was 1.8 microg (SE, 0.6 microg; 95% CI, 2.96 to 0.54 microg). The incidence of side effects was similar among the groups.

CONCLUSIONS

This is the first study to determine the ED50 of intrathecal sufentanil in spontaneously laboring nulliparous patients. As dose-response curves are determined for other labor analgesics, future studies can compare equianalgesic doses or dose combinations.

The effect of maternal position on fetal heart rate during epidural or intrathecal labor analgesia

OBJECTIVE

This study was designed to determine the relationship between maternal position and the incidence of prolonged decelerations after epidural bupivacaine or intrathecal sufentanil analgesia for labor.

STUDY DESIGN

Laboring, healthy, term parturient women, with reassuring fetal heart rate tracings, requesting either epidural (n = 145) or intrathecal (n = 160) analgesia were randomly assigned to lie either supine with measured 30-degree left uterine displacement (n = 136) or in the left lateral decubitus position (n = 145). Patients received either intrathecal sufentanil, 10 microg, or epidural 0.25% bupivacaine, 13 mL. An obstetrician, unaware of patient position or type of anesthesia, examined the fetal heart rate tracings.

RESULTS

No demographic differences were noted among the groups. Prolonged decelerations occurred with equal frequency after epidural bupivacaine and intrathecal sufentanil (3.9%). Prolonged decelerations were not related to maternal position. No emergency cesarean deliveries were performed as a result of prolonged decelerations. Prolonged decelerations correlated with the frequency of contractions before induction of analgesia (P < .05). Fewer fetal heart rate accelerations were noted after intrathecal sufentanil than after epidural bupivacaine (P < .005). More ephedrine was used after epidural bupivacaine (P < .001). Patients who received epidural analgesia in the left lateral position were more likely to have an asymmetric block (P < .05).

CONCLUSIONS

The risk of prolonged deceleration after epidural bupivacaine or intrathecal sufentanil labor analgesia is unrelated to maternal position or analgesic technique.

Labor epidural analgesia without an intravascular "test dose"

BACKGROUND

This study prospectively evaluated the ability of aspiration to detect intravascular placement of multiple-orifice epidural catheters.

METHODS

Multiple-orifice, 20-gauge epidural catheters were inserted in 1,029 laboring women. Catheters were observed and aspirated for blood or cerebrospinal fluid before they were tested with 2 ml local anesthetic. If the results of this test were negative (no spinal anesthesia), the authors induced and maintained labor analgesia with a dilute local anesthetic and opioid solution. Patients with bilateral sensory change and effective labor analgesia had a "positive" epidural catheter. Women with unilateral block, inadequate analgesia despite some sensory change or those who delivered before being adequately assessed had "equivocal" catheters. Patients with neither analgesia nor sensory change had "negative" catheters.

RESULTS

Aspiration and observation identified 60 intravenously placed catheters. Six catheters, which were placed initially in a blood vessel, were withdrawn until aspiration was negative, and then the anesthetic was infused. Four of these catheters were positive and two were still positioned intravascularly. Two other catheters may have been intravenously placed despite negative results of aspiration. The incidence of false-negative results of aspiration was 0 to 2 of 1,085 (upper limit of 95% CI, 0.2% to 0.4%). No patient showed any signs or symptoms of local anesthetic toxicity.

CONCLUSIONS

Under the conditions of this study, which include using multiple-orifice catheters and dilute solutions of local anesthetic and opioid, aspiration and incremental drug injection alone safeguard against the risks of intravenously positioned local anesthetics. These results should not be extrapolated to other clinical settings without further study.

Intrathecal sufentanil (5 vs. 10 microg) for labor analgesia: efficacy and side effects

BACKGROUND AND OBJECTIVES

Despite growing popularity, there are few studies examining the relative efficacy of different doses of intrathecal sufentanil for labor analgesia. This prospective, randomized, double-blind study compared the efficacy and side effects of 5 and 10 microg intrathecal sufentanil.

METHODS

Sixty-three healthy, laboring, term parturients < or =5 cm cervical dilation participated in this study. In a randomized, double-blind fashion, patients received 5 or 10 microg intrathecal sufentanil as part of a combined spinal epidural technique. Patients rated pain, itching, nausea, and sedation on verbal analog scales before and every 10 minutes after drug injection. We also recorded maternal blood pressure and peripheral oxygen saturation before and every 10 minutes after drug injection. Before and 30 and 60 minutes after drug injection, we measured maternal end-tidal CO2.

RESULTS

Both doses of sufentanil provided adequate analgesia. Although 10 microg sufentanil produced slightly more profound analgesia, the duration of pain relief did not differ between the two groups. Both drug doses were associated with significant increases in itching and end-tidal CO2. The 10-microg dose was associated with more sedation and a greater decrease in SaO2.

CONCLUSIONS

Both 5 and 10 microg intrathecal sufentanil provided adequate labor analgesia. Both doses were associated with measurable spinal (itching) and supraspinal (sedation, respiratory depression) side effects.

Maternal and fetal effects of isoproterenol in the gravid ewe

Detection of the intravascular placement of epidural catheters is an important but difficult task. In this study, we evaluated maternal and fetal hemodynamic responses to intravenous (i.v.) and epidural injection of isoproterenol (ISO), a proposed chronotropic test dose, in gravid ewes. Near-term, chronically instrumented, gravid ewes with single fetuses were studied at least 48 h after surgery. We continuously recorded maternal heart rate (MHR), systemic and pulmonary blood pressures, uterine blood flow (UBF), and fetal blood pressure and heart rate. Maternal cardiac output was measured by thermodilution. In random sequence, each ewe (n = 11) received i.v. injections of saline, epinephrine (EPI) 15 microg; ISO 4, 16, and 80 microg; or epidural (n = 9 ewes) injections of saline, ISO 4 microg and ISO 40 microg. All variables returned to baseline between experiments. Sections of lumber spinal cord were harvested from five animals for later histopathological study. I.v. ISO caused a dose-related increase in MHR. Cardiac output also increased transiently after all doses of ISO but not after EPI. Maternal diastolic blood pressure decreased after ISO 16 and 80 microg. UBF decreased significantly for 120 s after EPI 15 microg. Epidural ISO did not significantly change maternal systemic or pulmonary blood pressure, cardiac output, or UBF. The 40-microg dose increased MHR significantly. No histopathological changes were seen in three ISO-exposed and two control spinal cords. I.v. ISO reliably induces maternal tachycardia in nonstressed gravid ewes. Unlike EPI, I.v. ISO lacks a statistically significant effect on UBF. However, ISO seems to be rapidly absorbed from the epidural space. Identifying the source of maternal tachycardia after epidural injection of a large dose of ISO could be difficult. If the absence of histopathological change is confirmed, ISO represents an alternative to EPI as a chronotropic test dose.

Efficacy and financial benefit of an anesthesiologist-directed university preadmission evaluation center

STUDY OBJECTIVE

To study the effectiveness of an anesthesiologist-directed preadmission evaluation center (PEC) in our institution.

DESIGN

I: Preoperative test costs were measured on two sets of patients undergoing same-day surgery. II: Rate of cancellation was measured on all patients undergoing same-day surgery in a subsequent one-year time period.

SETTING

The PEC, short procedure unit, and same-day admission unit of a university hospital.

PATIENTS

I: 3,062 male and female patients undergoing same-day surgery between January 1, 1992, and August 31, 1992. II: 9,454 male and female patients undergoing same-day surgery between July 1, 1993, and June 30, 1994.

INTERVENTIONS

Age, ASA physical status, type of surgery performed, and tests ordered were recorded in two groups of same-day surgical patients. Group S had testing primarily ordered by surgeons, augmented by the anesthesiologists in the PEC. Group A had testing primarily ordered by the anesthesiologists in the PEC, but surgeons could still order tests they felt necessary. On the day of surgery, the attending anesthesiologist recorded any additional testing that was required or would have altered intraoperative management. In a follow-up study, cancellations of same-day surgical patients were recorded for a one-year period.

MEASUREMENTS AND MAIN RESULTS

I: With the exception of complete blood counts with differentials, significantly fewer tests were ordered in Group A than Group S. These changes produced an average cost savings of $20.89 per patient. There were no recorded cancellations or apparent alterations in intraoperative management attributable to inadequate testing. II: Of the 9,454 same-day procedures from 7/1/93 to 6/31/94, 66 were cancelled on the day of the procedure. None of the patients seen in the PEC were cancelled due to causes possibly preventable by a PEC, unlike the cases of 4 patients who had not been evaluated in teh PEC and were cancelled.

CONCLUSION

A PEC, in which the anesthesiologist primarily orders preoperative tests and approves patients' readiness for surgery, is both an efficient and cost-effective system.

Baricity, needle direction, and intrathecal sufentanil labor analgesia

BACKGROUND

Intrathecal sufentanil relieves labor pain but centrally mediated side effects are common. Preventing rostral spread of intrathecal sufentanil should limit these side effects. Both direction of the lateral opening of a pencil-point needle and drug baricity modify the spread of intrathecal local anesthetics. This randomized, prospective, double-blind study examines the effects of these variables on intrathecal sufentanil labor analgesia.

METHODS

Forty laboring, full-term parturients, whose cervixes were dilated less than 5 cm and who requested analgesia for labor were enrolled. Combined spinal epidural analgesia was induced in patients in the sitting position. They were allocated to receive 10 micrograms intrathecal sufentanil diluted with either normal saline or dextrose with the aperture of the pencil-point needle directed cephalad or caudad during drug injection. Thus there were four groups of ten patients: dextrose up, dextrose down, saline up, and saline down. Sufentanil was diluted with normal saline to a concentration of 10 micrograms/ml. The study drug was made by mixing 1 ml sufentanil solution with either 1 ml 10% dextrose or 1 ml normal saline. Visual analog scores for pain, pruritus, nausea, and pain relief were recorded before and 5, 10, 15, and 30 min after drug injection.

RESULTS

Baricity, but not needle orientation, influenced pain relief and pruritus. Sufentanil in dextrose produced less itching but also less analgesia. Nine of 20 women in the dextrose groups compared with 1 of 20 in the saline groups requested additional analgesia by 30 min.

CONCLUSIONS

Little or no labor analgesia developed for patients receiving sufentanil with dextrose. A supraspinal action may contribute to intrathecal sufentanil's analgesic efficacy.

The dermatomal spread of epidural bupivacaine with and without prior intrathecal sufentanil

Clinicians often use a technique combining intrathecal sufentanil and epidural bupivacaine to provide labor analgesia. This study determines the effect of 27- or 24-gauge dural puncture and intrathecal sufentanil 10 micrograms on the dermatomal spread of epidural bupivacaine. Healthy laboring women received no dural puncture (n = 77) (no puncture group [NPG]) or dural puncture with a 27-gauge Whitacre needle (n = 33) or a 24-gauge Sprotte needle (n = 37) and intrathecal sufentanil 10 micrograms (dural puncture group [DPG]) before epidural injection of 13 mL bupivacaine 0.25%. More dermatomes were anesthetized in the DPG, 16.6 +/- 7.5 vs 13.6 +/- 6.6 in the NPG (P < 0.02). More patients in the DPG had sensory blockade T-4 or higher (17 of 70 DPG patients vs 8 of 77 NPG patients; P < 0.05). No patient in either group showed clinical evidence of respiratory compromise. In conclusion, epidural bupivacaine anesthetized more dermatomes when administered 104 +/- 42 min after dural puncture and intrathecal sufentanil 10 micrograms than when given without prior dural puncture and intrathecal injection.

Labour analgesia. A risk-benefit analysis

The pain associated with labour can be severe. The ideal labour analgesic does not exist and systemic opioids provide little relief. Nausea, vomiting and sedation are common adverse effects of systemic opioids. Paracervical block can relieve only the pain of the first stage of labour. The duration of analgesia obtained using paracervical block is limited and repeat blocks increase the risk of direct fetal injection. Epidural analgesia effectively relieves labour pain. The insertion of an epidural catheter can provide continuous analgesia throughout labour. In addition, the catheter can be used to provide surgical anaesthesia, should operative delivery be required. Epidural local anaesthetics commonly produce maternal hypotension and motor blockade. However, opioids potentiate the effect of epidural local anaesthetics. Thus, concomitant epidural opioid injection allows the use of lower concentrations of local anaesthetics, decreasing the frequency and severity of hypotension and motor blockade. Epidural analgesia has other, potentially catastrophic, adverse effects but, with safe clinical practice, these problems are extremely rare. Intrathecal injection of opioids or local anaesthetics also effective labour analgesia. However, no single intrathecal drug or drug combination reliably provides analgesia for the duration of labour. Many clinicians use both intrathecal and epidural analgesia as a combined spinal-epidural technique. This approach provides the rapid onset of intrathecal drugs and the flexibility of continuous epidural block. Fetal heart rate decelerations occasionally follow the use of any of the above labour analgesic techniques. Most studies of the aetiology of fetal heart rate decelerations have focused on factors unique to each analgesic technique. However, the similar timing and appearance of fetal bradycardia suggests a common cause. Induction of maternal analgesia may transiently alter the balance between factors encouraging and inhibiting uterine contraction. A temporary increase in the uterotonic effects of endogenous or exogenous oxytocin may then produce a tetanic uterine contraction with subsequent decrease fetal oxygen delivery and resultant fetal bradycardia. Regardless of aetiology, these bradycardias are transient and should not produce maternal or fetal morbidity. Much controversy surrounds the effects of analgesia, especially epidural block, on the course and outcome of labour. Various studies have reported that epidural analgesia slows labour, increases the incidence of malposition of the fetal head, increases the need for forceps delivery and increases the risk of caesarean delivery. Most of the studies reporting these effects are retrospective and nonrandomised. More careful studies suggest that specific anaesthetic techniques (i.e. local anaesthetic-opioid mixtures) or obstetrical management can limit or eliminate these 'risks' of epidural labour analgesia.

A comparison of meperidine and lidocaine for spinal anesthesia for postpartum tubal ligation

BACKGROUND AND OBJECTIVES

This study compares the anesthetic potency, duration, and side effects of subarachnoid meperidine and lidocaine for postpartum tubal ligation.

METHOD

Twenty healthy, unpremedicated postpartum women gave written informed consent to participate in this randomized double-blind study. After intravenous infusion of 200 mL physiologic salt solution, patients received subarachnoid injections from either lidocaine 70 mg in 7.5% glucose or meperidine 60 mg in saline while lying in the right lateral position. Heart rate, blood pressure, sensory and motor block, pain, nausea, and pruritus were recorded at intervals for up to 12 hours after injection. The time to first postoperative analgesic was also recorded.

RESULTS

There were no differences between the groups in demographics, heart rate, or blood pressure at any time. Sensory or motor block developed slightly faster in the lidocaine group. One patient in each group required general anesthesia owing to inadequate sensory block. Beginning at 60 minutes, meperidine patients experienced more pruritus (P < .05). Lidocaine patients had more postoperative pain (P < .01) and required supplemental analgesia 83.3 +/- 32.7 minutes after induction versus 447.6 +/- 184.0 minutes in the meperidine group. No patient's oxygen saturation fell below 95%. Patients expressed equal satisfaction with both agents.

CONCLUSION

Subarachnoid meperidine and lidocaine both provide adequate anesthesia for postpartum tubal ligation. Meperidine provided longer postoperative analgesia.

Advance prediction of hypotension at cesarean delivery under spinal anesthesia

Cardiovascular responses to supine inferior vena cava compression might predict hypotension risk during elective cesarean delivery using spinal anesthesia. In this pilot study we investigated 27 women before operation by taking blood pressure and heart rate measurements for 5 min in the left lateral position, 5 min supine, and then performed one further reading in the left lateral position and one sitting. Anesthesia with hyperbaric bupivacaine was rigorously standardised. A pre-operative 'supine stress test', combining an increase in maternal heart rate of greater than 10 beats/min or leg flexion movements while supine, was analysed. A positive supine stress test (SST) was 4.1 times more frequent in those with severe systolic hypotension below 70% of baseline (12 out of 16 women) than in those without (2 out of 11 women), with a sensitivity of 75% (95% C.I. 48% to 93%) and specificity of 82% (95% C.I. 48% to 98%). A positive test was associated with twice as much vasopressor use as a negative test (30.7 +/-/14.5 mg versus 13.5 +/-/ 9.9 mg; P = 0.0014). Unlike the SST, cardiovascular responses to the change from recumbent to sitting (tilt test) were not useful as a predictor of hypotension.

Ilioinguinal iliohypogastric nerve blocks--before or after cesarean delivery under spinal anesthesia?

Preoperative local anesthetic blockade of somatosensory pathways involved with skin incision and other noxious perioperative stimuli may "preempt" or attenuate the postoperative pain response. Since the Pfannenstiel incision lies within the L1 dermatome, bilateral ilioinguinal, iliohypogastric nerve blocks (IINBs) should provide analgesia after low transverse cesarean section. We designed this study to compare the analgesic effect of IINBs placed before or after cesarean delivery. Forty-six patients undergoing cesarean delivery with spinal anesthesia were enrolled. Patients were randomly assigned to one of three groups: Before, After, or None. Bilateral IINBs were placed with 0.5% bupivacaine, 10 mL to each side. Twenty-two patients had IINBs placed before surgery (11 failed blocks), 12 had blocks placed after surgery, and 12 had no block. Morphine, through a patient-controlled analgesia (PCA) pump, provided additional postoperative analgesia. A blinded observer assessed 24-h morphine use as well as patient satisfaction and pain scores ("incisional" and "overall") for 96 h. Although there were no consistent differences in pain scores among the groups, patients in the After group occasionally reported more pain than those in the Before and None groups. Patient satisfaction and morphine use did not differ among the groups. We conclude that there is no benefit to ilioinguinal nerve blocks, either before or after surgery, in patients who receive spinal anesthesia for elective cesarean delivery. Our finding of increased pain in the After group is perplexing and requires confirmation.

Does continuous intravenous infusion of low-concentration epinephrine impair uterine blood flow in pregnant ewes?

BACKGROUND AND OBJECTIVES

Bolus intravenous injection of epinephrine can decrease uterine blood flow. This study examined the effects of intravenous infusion of epinephrine on uterine blood flow in the gravid ewe.

METHODS

Maternal and fetal vascular catheters and a maternal electromagnetic uterine artery flow probe were implanted in 10 near-term gravid ewes. After recovery, saline, 0.125% bupivacaine, 0.125% bupivacaine with 1:200,000 epinephrine, 0.125% bupivacaine with 1:400,000 epinephrine, and 0.125% bupivacaine with 1:800,000 epinephrine were infused into the maternal superior vena cava. Drugs were infused at 10 mL/h for 30 minutes and then at 20 mL/h for an additional 30 minutes. Animals also received an intravenous bolus of epinephrine 15 micrograms. Throughout all infusions, maternal heart rate, systemic and pulmonary blood pressures, uterine blood flow, cardiac output, and acid-base balance were measured, as well as fetal heart rate, blood pressure, and acid-base balance.

RESULTS

Epinephrine 15 micrograms decreased uterine blood flow to 68 +/- 14% of baseline (mean +/- SD). Infusion of all solutions had no effect on any measured hemodynamic variable.

CONCLUSIONS

In gravid ewes, intravenous infusion of < or = 1.67 micrograms/min epinephrine altered neither maternal hemodynamics nor uterine blood flow. To the extent that sheep data can be extrapolated to humans, these results suggest that continuous intravenous infusion of epinephrine in local anesthetic solutions is safe if the epidural catheter should enter a blood vessel during the infusion.

Spinal anesthesia for cesarean delivery. A comparison of two doses of hyperbaric bupivacaine

BACKGROUND AND OBJECTIVES

Hyperbaric local anesthetic pools in the thoracic spinal curvature in supine patients. The authors hypothesized that patients receiving 12 or 15 mg of hyperbaric bupivacaine would achieve similar levels of sensory block but the spinal anesthetic would be denser and longer lasting in patients receiving the 15 mg dose.

METHODS

Twenty eight healthy term parturients scheduled for elective cesarean delivery randomly received 12 or 15 mg hyperbaric 0.75% bupivacaine in 8.25% dextrose. Patients were in the right lateral position during drug injection and were then positioned supine with left uterine displacement on a horizontal operating table. A blinded anesthesiologist assessed the dermatome level of sensory analgesia to pinprick every 2 minutes for 20 minutes, then every 15 minutes until the sensory level regressed to T10.

RESULTS

The mean level of sensory anesthesia was 2.2 spinal segments higher in patients receiving 15 mg versus 12 mg hyperbaric bupivacaine (24.8 +/- 3.7 versus 22.6 +/- 1.4 spinal segments; P = .031). Regression to T10 occurred more quickly in the 12 mg than in the 15 mg group (140.0 +/- 16.5 versus 162.1 +/- 33.8 minutes, P = .046). Patient height did not correlate with the maximum number of spinal segments blocked in either group. All patients had adequate surgical anesthesia.

CONCLUSIONS

Parturients receiving 15 mg of hyperbaric bupivacaine developed a higher mean level and longer duration of sensory analgesia than those receiving 12 mg.

Complications of labor analgesia: epidural versus combined spinal epidural techniques

Both epidural and combined spinal epidural (CSE) analgesia can provide maternal pain relief during labor. Currently, there are few data comparing the risks and complications of these two techniques. We recorded the incidence and severity of anesthetic-related complications in 1022 laboring parturients. Ninety-eight women opted for either no or parenteral analgesia, 388 chose epidural, and 536 requested CSE analgesia. Women choosing CSE analgesia most often received an intrathecal injection of sufentanil 10 micrograms at the time of epidural catheter insertion. The epidural catheters were then dosed as needed as the intrathecal analgesia waned. Women who received CSE analgesia were more likely to itch (41.4% vs 1.3%) or complain of nausea (2.4% vs 1.0%) or vomiting (3.2% vs 1.0%) than those receiving solely epidural analgesia. Patients who requested only epidural analgesia were more likely to suffer an unintended dural puncture (4.2% vs 1.7%). Fewer than 10% developed hypotension with either technique. The risk of headache was the same with both anesthetics (4%-10%) and did not differ from the incidence of headache in women not receiving neuraxial analgesia (10%-14%). Six patients required epidural blood patch for moderate to severe postural headache. Four of these women suffered a dural puncture with the 18-gauge Hustead epidural needle. The other two women had reportedly uncomplicated epidural and CSE analgesia. These data suggest either neuraxial analgesic technique can safely relieve the pain of labor. CSE analgesia is a safe alternative to epidural analgesia for labor and delivery.

Do patient variables influence the subarachnoid spread of hyperbaric lidocaine in the postpartum patient?

BACKGROUND AND OBJECTIVES

Age, height, weight, body mass index (weight/height2), and vertebral column length may affect the subarachnoid spread of local anesthetics. Little information exists concerning the relationship between these variables and the spread of hyperbaric lidocaine. The authors studied the influence of patient demographics on the block produced by hyperbaric lidocaine in women undergoing postpartum tubal ligation.

METHODS

Within 48 hours of vaginal delivery, the authors studied 44 ASA class 1-2 women agreeing to spinal anesthesia for postpartum tubal ligation. Before induction of anesthesia, the authors weighed each patient, measured her height and vertebral column length, and calculated body mass index. In a standardized manner, the authors induced spinal anesthesia with 5% lidocaine 75 mg. An observer, blinded to the measured variables, evaluated loss-of-temperature sensation and loss-of-sensation of sharpness to pinprick bilaterally every 5 minutes for 30 minutes and again at 45 and 60 minutes.

RESULTS

There was no correlation between age, weight, body mass index, vertebral column length, or time from delivery to placement of the block, and the spread of sensory block after subarachnoid injection of hyperbaric lidocaine. Only height weakly correlated with the spread of block (r2 = 0.15).

CONCLUSIONS

While height may have some small influence on the spread of sensory block, the variation in spread of block within patients of the same height is large. The data suggest that adjusting the dose of local anesthetic injected based on differences in patient height would provide no clinically significant benefit.

Subarachnoid labor analgesia. Fentanyl and morphine versus sufentanil and morphine

BACKGROUND AND OBJECTIVES

To compare the duration of pain relief and incidence of side effects using two subarachnoid administered drug combinations for labor analgesia: fentanyl 25 micrograms with morphine 0.25 mg or sufentanil 10 micrograms with morphine 0.25 mg.

METHODS

Thirty healthy term primagravid patients with cervical dilation < or = 5 cm consented to participate in this prospective, randomized, double-blind study. Patients received the assigned drug combination subarachnoid with simultaneous epidural catheter placement using a double needle technique. The authors recorded blood pressure and patient's rated pain, nausea, and pruritus using 10-cm visual analog scales at 0, 5, 10, 15, 20, 25, 30, and every 30 minutes until the patient requested additional analgesia.

RESULTS

The onset of analgesia was rapid in both groups. The mean duration of analgesia was similar; 114 +/- 55 minutes in the fentanyl and morphine group and 134 +/- 79 minutes in the sufentanil and morphine group. The sufentanil and morphine group experienced more severe pruritus (P = .015).

CONCLUSIONS

Both fentanyl and morphine and sufentanil and morphine provide adequate labor analgesia for about 2 hours. Patients who receive sufentanil experience more severe pruritus.

The incidence of herpes simplex virus labialis after cesarean delivery

Epidural and subarachnoid opioids have been associated with the development of oral herpes simplex lesions. Because of this risk, some anesthesiologists avoid neuraxial morphine in parturients with a history of herpes simplex virus labialis. When we began using neuraxial opioids for analgesia after cesarean delivery, we did not see any increased incidence of facial lesions. To confirm this impression, we studied 357 consecutive parturients presenting for elective or emergent cesarean delivery between 1 December 1989 and 27 June 1990. The women received spinal, epidural, or general anesthesia. Two hundred and one women received either spinal or epidural morphine, the remaining 156 parturients received only systemic opioids for postoperative analgesia. An investigator saw each patient daily until discharge. Only 11 patients (3%) developed oral lesions while hospitalized. None of these women had severe lesions. Neuraxial morphine did not increase the risk of labial lesions significantly (3.5% vs. 2.6%). Despite published data to the contrary, we found no correlation between neuraxial morphine and the risk of facial herpes virus lesions in women after cesarean delivery. We offer patients the option of neuraxial morphine for analgesia after cesarean delivery despite any history of oral herpes lesions.

Intrathecal sufentanil labor analgesia: the effects of adding morphine or epinephrine

Intrathecal opioids can provide labor analgesia. We attempted to prolong the duration of intrathecal sufentanil analgesia by adding epinephrine or morphine. Forty-one healthy, term nulliparae with cervical dilation < 5 cm participated in this double-blind, randomized protocol. Using a combined spinal and epidural technique, we gave intrathecal injections of either sufentanil 10 micrograms, sufentanil 10 micrograms plus epinephrine 200 micrograms, or sufentanil 10 micrograms plus morphine 250 micrograms. At baseline and every 5 min for 30 min thereafter, we recorded arterial blood pressure and asked the patients to rate their pain, nausea, and pruritus on visual analog scales. The women continued to rate these variables every 30 min until they requested additional analgesia. They then received 10 mL of 0.25% bupivacaine via the epidural catheter, and rated the above variables every 30 min until they requested additional epidural drug injection. Both morphine and epinephrine prolonged the duration of sufentanil analgesia. Only morphine prolonged analgesia after the first dose of epidural bupivacaine. However, because women in the morphine group experienced significantly more side effects throughout the study period, we do not recommend intrathecal morphine for labor analgesia.

Comparison among intrathecal fentanyl, meperidine, and sufentanil for labor analgesia

This study compared the analgesic efficacy of intermittent injections of intrathecal fentanyl (10 micrograms), meperidine (10 mg), or sufentanil (5 micrograms) administered to 65 parturients during the first stage of labor. The groups did not differ in onset or duration of effective analgesia. The meperidine group, however, had significantly lower pain scores once cervical dilation progressed beyond 6 cm. Side effects included mild pruritus and nausea. After intrathecal drug injection, variable decelerations of the fetal heart rate increased in the fentanyl and meperidine groups. All neonates had a 5-min Apgar score of 7 or more. We conclude that intermittent intrathecal injections of fentanyl, meperidine, or sufentanil can provide adequate first-stage labor analgesia. Meperidine appears to provide more reliable analgesia as the first stage of labor progresses.

Histamine release following intrathecal administration of morphine for cesarean section

We present a case of unusually profound, prolonged hypotension after induction of spinal anesthesia for cesarean section. The patient, a healthy parturient at 26 weeks gestation, received 0.75% bupivacaine, 15 mg and morphine, 0.15 mg by subarachnoid injection. Systolic blood pressure rapidly fell to below 80 mmHg despite left uterine displacement, 10 l of balanced saline solution, ephedrine 210 mg and phenylephrine 1000 microg. At the end of the operation we noted a pruritic, erythematous, circumscribed, raised rash, consistent with urticaria, over the patient's trunk, legs, arms and face. This rash persisted for 2 days. We postulate that the excessive hypotension following spinal anesthesia in this parturient was the result of intrathecal morphine induced histamine release.

Continuous spinal anesthesia after unintentional dural puncture in parturients

Headache after unintentional dural puncture with 17- or 18-gauge needles represents a significant source of anesthetic-induced maternal morbidity. We performed this study to determine whether inserting a catheter into the subarachnoid space after dural puncture can significantly alter the incidence of headache. Thirty-five women, requesting labor analgesia, suffered a dural puncture during attempts to identify the epidural space using an 18-gauge Hustead needle (bevel oriented parallel to the longitudinal axis of the back). Subsequently, the anesthesiologist inserted a 20-gauge polyamide catheter into the CSF and provided continuous spinal anesthesia throughout labor and delivery. A second group of 21 women suffered dural puncture with the same epidural technique but without subarachnoid catheter insertion. These women subsequently received lumbar epidural anesthesia. After delivery, we visited all women daily until discharge and questioned them about the presence and severity of headache. Neither the incidence of headache nor the need for therapeutic blood patch differed significantly between the two groups of women. No other anesthetic related complications ensued. Continuous spinal anesthesia after unintentional dural puncture does not decrease the incidence of headache in parturients.

The air test as a clinically useful indicator of intravenously placed epidural catheters

The authors performed a clinical trial in 313 patients in labor to determine the safety and efficacy of an air test for unintentional intravenous placement of epidural catheters. Following routine aspiration for blood and cerebrospinal fluid, 1 ml of air was injected through each epidural catheter while heart tones were continually monitored with a Doppler ultrasound probe placed over the maternal precordium. In 281 patients, Doppler heart tones did not change following air injection (negative air test). All but eight of these patients developed an adequate level of analgesia following anesthetic administration, and no patients with negative air tests developed signs or symptoms of local anesthetic toxicity (false-negative rate, 0%; 95% confidence limits, 0.0-1.1%). Doppler heart tone changes followed air injection in 22 cases (positive air test). In 16 of these, intravenous catheter position was subsequently shown by aspiration of blood from the catheter or by the use of test doses consisting of local anesthetics with or without epinephrine. In six cases, adequate levels of analgesia developed despite a positive air test (false-positive rate, 2%; 95% confidence limit, 0.7-4.3%). None of the 303 patients receiving the air test developed any complications attributable to the injection of air (95% confidence limits, 0.0-1.0%). The authors conclude that air, with precordial Doppler detection, is a safe and effective test for identifying intravenously located epidural catheters.

Patient variables and the subarachnoid spread of hyperbaric bupivacaine in the term parturient

To determine if age, height, weight, body mass index, or vertebral column length significantly influence the distribution of sensory analgesia or anesthesia after subarachnoid injection of hyperbaric bupivacaine, 52 women presenting for cesarean section were studied. All received 15 mg hyperbaric bupivacaine via subarachnoid injection at L-2 or L-3. Fifteen minutes after injection, while the women lay supine on a horizontal operating table, the maximum cephalad extent of sensory analgesia (loss of sensation of sharpness to pin prick) and anesthesia (loss of sensation of light touch) was determined. Age (20-42 yr), height (146.9-174.0 cm), weight (55.5-136.4 kg), body mass index (19.2-50.0 kg/m2), and vertebral column length (49.6-67.0 cm) did not correlate with the spread of sensory blockade. In conclusion, in parturients of age, height, weight, body mass index, and vertebral column length within the aforementioned ranges, it is not necessary to vary the dose of injected hyperbaric bupivacaine with changes in any of the patient variables studied.

Incidence of electrocardiographic changes during cesarean delivery under regional anesthesia

Serial electrocardiograms were obtained on 93 healthy ASA physical status I and II term parturients during nonemergent cesarean delivery under regional anesthesia. Electrocardiographic changes occurred in 44 of the 93 patients (47.3%); in 35 of these 44 patients, the changes were characteristic, or suggestive, of myocardial ischemia. Symptoms of chest pain, pressure, and dyspnea occurred in 15 of the 44 patients with electrocardiographic changes; no patient without electrocardiographic change developed symptoms of chest pain, pressure, or dyspnea. Small but statistically significant differences were noted in heart rate, diastolic and systolic arterial pressures, and rate-pressure product between the patients with electrocardiographic changes and those without. The authors speculate that myocardial ischemia is a likely cause of both the electrocardiographic changes seen in these patients and of the symptoms of chest pain and dyspnea that they sometimes experience.

Denitrogenation in pregnancy

This study measured nitrogen washout in ten pregnant and nine non-pregnant women to understand better how pregnancy effects denitrogenation. Nitrogen concentration was monitored continuously while the women breathed 100 per cent O2 for three minutes and took four deep breaths of 100 per cent O2 using a circle anaesthesia system and 8 L.min-1 fresh gas flow. Parturients achieved 95 per cent denitrogenation significantly (P less than 0.0005) faster than non-pregnant women (54.5 +/- 17.8 vs 110.8 +/- 35.7 sec). In parturients, denitrogenation for three minutes lowered expired N2 concentration to 1.0 +/- 0.2 per cent while four deep breaths lowered it to 5.1 +/- 1.7 per cent (P less than 0.0001). This difference, while statistically significant, is predicted to supply only 10-15 sec of extra protection against hypoxaemia, and thus is probably not clinically significant. The authors conclude that either two minutes of tidal breathing or four deep breaths of 100 per cent O2 provide adequate denitrogenation and similar protection against apnoeic hypoxaemia in normal parturients.

Isoproterenol is an effective marker of intravenous injection in laboring women

The purpose of this randomized, double-blind study was to determine if isoproterenol 5 micrograms iv produces a consistent, noticeable tachycardia in healthy, laboring women. Maternal heart rate, fetal heart rate, and uterine contractions were continuously recorded and maternal blood pressure was measured every minute for 10 min before and after each patient received either normal saline (NS group; n = 10) or isoproterenol 5 micrograms (ISO group; n = 10) iv. The data-collecting investigator and a nurse palpating the patient's radial artery determined which solution they thought had been administered. The authors analyzed the maternal heart rate tracings using baseline-to-peak (a greater than or equal to 25 beat/min maternal heart rate increase occurring within 120 s of drug injection and lasting greater than or equal to 15 s) and peak-to-peak (a greater than or equal to 10 beat/min increase in the maximum maternal heart rate during the 2-min postinjection over the maximum maternal heart rate during the 2 min preinjection) criteria for detection of an intravascular marker. Mean maternal heart rate in the ISO group was significantly higher than in the NS group 20, 30, 40, 50, and 60 s following the injection (P less than 0.01). The peak-to-peak criterion and the data-collecting investigator correctly classified all patients. Five ISO group patients were not identified by the baseline-to-peak criterion. The nurse palpating the mother's radial artery misidentified two patients. Systolic blood pressure was significantly higher in ISO group than in NS group patients 1 min (P less than 0.05) and 2 min (P less than 0.01) following drug injection. Diastolic and mean blood pressures did not change. No fetal distress occurred. Isoproterenol 5 micrograms is an effective marker of intravascular injection in laboring women; however, the safety and efficacy of epidural isoproterenol must be demonstrated in animals before isoproterenol can be incorporated in an epidural anesthesia test dose.

Evaluation of a continuous noninvasive blood pressure monitor in obstetric patients undergoing spinal anesthesia

A noninvasive blood pressure monitor (Finapres) that continuously displays the arterial waveform using the Penaz methodology has recently been introduced into clinical practice. We compared this device with an automated oscillometric blood pressure monitor (Dinamap 1846SX) in 20 patients during spinal anesthesia for nonemergency cesarean section according to a procedure suggested by the Association for the Advancement of Medical Instrumentation. After administration of the spinal anesthetic, the Finapres monitor produced systolic, mean, and diastolic pressure measurements greater than those of the Dinamap monitor (6.6 +/- 12.5, 3.3 +/- 10.4, and 7.2 +/- 9.8 mm Hg, respectively). In most patients, the Finapres measurements were similar to those determined by the Dinamap; however, in 4 patients, mean systolic differences were greater than 20 mm Hg. These patients did not differ from the others in age, height, weight, or baseline blood pressure, and the pressure values recorded by the Finapres monitor were substantially higher than those measured by auscultation in the labor room. In 30% of the patients, the offset between Dinamap and Finapres blood pressure measurements changed markedly over the course of the surgical procedure. The Finapres monitor occasionally stopped working and had to be restarted. In 1 patient (not included in this analysis), the Dinamap monitor was unable to determine the blood pressure due to patient shivering; this did not appear to interfere with the Finapres. We conclude that the Finapres monitor does not consistently provide blood pressure information equivalent to that of the Dinamap in obstetric patients undergoing spinal anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)