Experimental validation of the CompuFlo® epidural controlled system to identify the epidural space and its clinical use in difficult obstetric cases.

BACKGROUND: This prospective study was designed to validate the CompuFlo® device and to assess its use in difficult epidural placement. METHODS: In the first part of the study, 30 parturients requesting labor epidural analgesia were recruited. The block was performed by an expert anesthesiologist, with the Tuohy needle connected to the CompuFlo® device to evaluate the agreement between the anesthesiologist's reported sensation and the variation of pressure recorded by the CompuFlo®. In the second part of the study, 56 consecutive parturients, for whom at least two complete needle reinsertions were made by trainees during epidural placement for labor analgesia, were enrolled. CompuFlo® was used as a rescue tool for the subsequent attempt. RESULTS: In all cases epidural analgesia was successful and no complications were noted. There was a good correlation between the operator's feelings and the delta of pressure recorded by the CompuFlo®, for both identification of the ligamentum flavum and of the epidural space (Rho = 0.79; tau = 0.67). In the second part of the study, all the difficult blocks performed with the CompuFlo® were successful after a single attempt. The pressure curves of false loss-of-resistance were significantly different from the true loss-of-resistance (P <0.0001) DISCUSSION: CompuFlo® was validated as a tool to identify the epidural space. It may also assist trainees in successful epidural placement in difficult cases.

Effect of µ-opioid receptor A118G polymorphism on the ED50 of epidural sufentanil for labor analgesia.

BACKGROUND: A common polymorphism of the µ-opioid receptor gene (OPRM1, p.118A/G), which has been shown to effect the response to neuraxial opioids, occurs in 30% of Caucasian women. This double-blind up-down sequential allocation study was designed to examine the effect of p.118A/G on the ED50 of epidural sufentanil for labor analgesia. METHODS: Nulliparous women were recruited at 35 weeks of gestation (n=77) and genotyped for p.118A/G. Those subsequently requesting epidural labor analgesia were enrolled. Each woman received epidural sufentanil diluted with 0.9% saline to a volume of 5 mL. The initial sufentanil dose was 21 µg, with subsequent doses determined by the response of the previous patient (testing interval 1 µg). Efficacy was accepted if the visual analogue score decreased to <10mm on a 100-mm scale within 30 min of drug administration. RESULTS: Twenty patients were excluded, leaving 57 women from whom data were analyzed: 33 in Group A (wild-type A118 homozygotes) and 24 in Group G (heterozygotes and homozygotes G118). The ED50 for epidural sufentanil was 25.2 µg in Group A (95% CI 23.2-26.4) and 20.2 µg in Group G (95% CI 14.2-23.6) (P=0.03). The potency ratio for epidural sufentanil in Group G compared to Group A was 1.25 (95% CI 1.00-1.64). CONCLUSION: Women carrying the variant allele of p.118A/G of OPRM1 (G118) had a lower ED50 for epidural sufentanil given for early labor analgesia than women homozygous for the wild-type allele.

Multidimensional evaluation of pain during early and late labor: a comparison of nulliparous and multiparous women.

BACKGROUND: Labor pain has a sensory and an affective component. This study was undertaken to evaluate whether the quality and intensity of the cognitive descriptors of labor pain may be influenced by parity and stage of labor. METHODS: One hundred and eighty-four parturients were divided into four groups according to parity (nulliparous and multiparous women) and stage of labor (early and late) and were given a modified version of the short-form McGill Pain Questionnaire that included the 23 most frequently reported labor pain descriptors. In addition, parturients were asked to report intensity of pain on a visual analogue pain scale and using the present pain intensity index. RESULTS: The most frequent descriptors used were cramping, pulling, hot, stinging, aching, heavy, tiring, exhausting and unbearable. The descriptors, "tiring" and "exhausting", were used primarily by nulliparous women (P <0.001). The intensity of "cramping", "stinging" and "aching" was greater in nulliparous women (P <0.0001) and the intensity of "heavy", "stinging", and "aching" increased as labor progressed in both groups (P <0.001). Mean intensity of pain increased as cervical dilation increased in both nulliparous and multiparous women. The visual analogue pain scale and present pain intensity index were strongly correlated (tau=0.63; P <0.0001). Low fetal station was associated with greater pain scores in nulliparous women (P<0.026). CONCLUSIONS: Affective and cognitive components of labor pain are frequently communicated with a restricted number of pain descriptors and may be affected by obstetric variables. An understanding of labor pain in a multidimensional framework provides the basis for a woman-centered approach to labor pain management.

Estimation of the minimum motor blocking potency ratio for intrathecal bupivacaine and lidocaine.

BACKGROUND: The up-down sequential allocation model has been adapted to investigate a variety of clinical and pharmacological issues in neuraxial anaesthesia including the estimation of relative potency ratios for analgesia and motor block of the most commonly used epidural and intrathecal local anaesthetics. The aim of this study was to establish the median effective doses (ED50) for motor block with intrathecal lidocaine and bupivacaine and to define the relative motor blocking potency ratio. METHODS: In this prospective, randomised, double blind, parallel group, up-down sequential allocation study, we enrolled 71 parturients undergoing elective caesarean section under combined spinal-epidural anaesthesia. The women received either intrathecal lidocaine 2% w/v or bupivacaine 0.5% w/v. The initial dose was 4 mg for bupivacaine and 12 mg for lidocaine. Subsequent doses were determined by the outcome in the previous parturient, according to the up-down sequential allocation technique. The end point was the occurrence of any motor block in either lower limb within 5 min. RESULTS: The intrathecal ED50 for motor block was 13.7 mg for lidocaine (95% CI, 13.1 to 14.4) and 3.4 mg for bupivacaine (95% CI, 2.6 to 4.1) (P<0.0001) and the relative motor blocking potency ratio was 4.1 (95% CI 3.3 to 5.2). CONCLUSIONS: Intrathecal bupivacaine was 4.1 times more potent than lidocaine for motor block.

Expectant fathers' experience during labor with or without epidural analgesia.

BACKGROUND: For men the worst aspect of childbirth is witnessing their partner in pain. The aim of this study was to investigate fathers' attitudes towards labor and delivery with and without epidural analgesia. METHOD: The study was performed using a questionnaire that included yes/no, multiple choice or 6-point ordinal scale answers. Expectant fathers whose partners were nullipara between 36 and 38 weeks of gestation were recruited and the questionnaires were administered on the day after the birth. To investigate paternal anxiety during labor, the State part of the State-Trait Anxiety Inventory was used. RESULTS: The questionnaire was completed by 243 fathers. Sixty percent (145) of the parturients received epidural analgesia and 40% (98) did not. Paternal characteristics were comparable. Fathers whose partners did not receive epidural analgesia felt their presence as troublesome and unnecessary (P<0.001). The presence of maternal epidural analgesia increased threefold paternal feelings of helpfulness and was associated with a greater involvement (P<0.001) and less anxiety and stress (P<0.001). Median (range) State-Trait Anxiety Inventory score was respectively 75 (50-80) and 30 (20-60) in fathers whose partners did not or did receive epidural analgesia (P<0.0001). Maternal analgesia greatly increased paternal satisfaction (P<0.0001). CONCLUSION: Epidural analgesia reduces paternal anxiety and stress and increases paternal involvement, participation and satisfaction with the experience of childbirth.

Sensory assessment of epidural block for Caesarean section: a systematic comparison of pinprick, cold and touch sensation.

BACKGROUND AND OBJECTIVE: Comparisons between the profile of regional blocks are difficult to make because different methods of testing are used among the studies. The aims of this prospective study were to describe the profile of epidural block by using a scoring system to evaluate the density of the block as assessed by the loss to pinprick, cold and touch sensation; to evaluate the extent of differential block and to determine whether there is any relationship between these three modalities of testing. METHODS: We studied 85 parturients undergoing elective Caesarean delivery with epidural anaesthesia with pH adjusted lidocaine 2% with epinephrine 1:400,000 and sufentanil 10 microg. Assessment of sensory block was done in each dermatomal level bilaterally for loss to pinprick, cold and light touch sensation and the density of the block was evaluated on an ordinal scale every 5 min for 20 min and thereafter at 30 and 40 min. RESULTS: We observed a two dermatomes differential block between the complete loss of cold sensation being cephalad and the complete loss of both pinprick and light touch sensation being caudal. We established a significant correlation between the scores used to assess the density of the block in the three different modalities by considering the pinprick score as reference (Spearman's rank correlation is 0.94, P<0.001 for pinprick vs. cold, 0.97, P<0.001 for pinprick vs. light touch). CONCLUSIONS: By scoring the density of the block on an ordinal scale, knowing the level of the block to pinprick allows one to predict the level of the block to touch and vice versa.

Epidural test dose with levobupivacaine and ropivacaine: determination of ED(50) motor block after spinal administration.

BACKGROUND: When a test is required to detect a possible intrathecal catheter, many would seek to use the same local anaesthetic as that used for epidural analgesia. The rapid onset of inappropriate motor block after a local anaesthetic administered epidurally implies intrathecal spread. Because of claims of greater sensory-motor separation, or because of reduced potency compared with bupivacaine, the efficacy of the new local anaesthetics in intrathecal testing has been questioned. The aim of this study was to establish the feasibility of a test dose for an inadvertent intrathecal catheter using ropivacaine and levobupivacaine, and to establish the dose required. METHODS: Sixty women undergoing elective Caesarean section with a combined spinal- epidural technique were enrolled into this prospective, double-blind sequential allocation study. The women were randomized to receive plain levobupivacaine 0.5% or ropivacaine 0.5% intrathecally. The dose was determined according to up-down sequential allocation. The end-point was any evidence of lower limb motor block within 5 min of injection. RESULTS: The ED(50) motor block at 5 min was 4.8 mg (95% CI, 4.49, 5.28) for levobupivacaine and 5.9 mg (95% CI, 4.82, 6.98) for ropivacaine (95% CI difference, 0.052, 1.98) (P=0.04). The estimated ED(95) motor block was 5.9 mg (95% CI 5.19, 6.71) for levobupivacaine and 8.3 mg (95% CI, 6.30, 10.44) for ropivacaine. The potency ratio between the two drugs was 0.83 (95% CI, 0.69, 0.99). CONCLUSIONS: Both local anaesthetics produce evidence of motor block within 5 min of intrathecal injection and could serve as tests of intrathecal administration. Derived ED(95) values suggest 10 mg doses should be effective, but this study did not measure predictive value. Ropivacaine is less potent for motor block than levobupivacaine by a factor of 0.83 (P<0.04).

Epidural levobupivacaine, ropivacaine and bupivacaine in combination with sufentanil in early labour: a randomized trial.

BACKGROUND AND OBJECTIVE: To evaluate the efficacy, delay and duration of analgesia of three equianalgesic epidural doses of levobupivacaine, ropivacaine and bupivacaine during the first stage of labour. METHODS: One hundred and twenty-nine healthy primigravida in spontaneous labour who requested epidural analgesia were enrolled in a randomized observer-blinded study. Parturients were allocated to receive epidural levobupivacaine 0.0625%, ropivacaine 0.1% or bupivacaine 0.06259%. Sufentanil 10 microg was added to all solutions; the total volume of epidural solution was 20 mL. Pain was measured using a 100 mm visual analogue pain scale immediately before the epidural block, and at 5, 10, 15, 20 and 30 min thereafter. Motor block was evaluated using a modified Bromage scoring system. The adequacy of motor function for ambulation was also evaluated. Delay of analgesia was the time interval between the injection of the solution and the first painless contraction. Duration of analgesia was the time from the first painless contraction to the parturients' requests for further analgesia. RESULTS: Twelve parturients failed to complete the study. Eleven parturients had inadequate analgesia (four in Group Levobupivacaine, four in Group Ropivacaine and three in Group Bupivacaine; P > 0.05). Data was analysed from 34 parturients in Group Levobupivacaine, from 37 in Group Ropivacaine and from 35 in Group Bupivacaine. There were no differences in the delay of analgesia or in the number of parturients who were able to walk unaided. Levobupivacaine and ropivacaine produced more prolonged analgesia than bupivacaine (114 and 119 min, respectively, versus 89 min; P < 0.01). CONCLUSIONS: During early labour, equipotent low concentrations of levobupivacaine, ropivacaine and bupivacaine, all with the addition of sufentanil 10 microg, produced similar pain relief and motor block, but levobupivacaine and ropivacaine produced a longer lasting analgesia. About 10% of parturients had inadequate analgesia with a single bolus of the tested solutions.

[Levobupivacaine in obstetric analgesia and anaesthesia]. / La levobupivacaina in anestesia ed analgesia ostetrica.

METHODS: Published studies, including abstracts, has been reviewed and summarized. RESULTS: Studies in sheep have demonstrated no significant differences in pharmacokinetic and placental transfer of levobuvacaine when compared with bupivacaine. Clinical studies on cesarean section confirmed similar performance between these two drugs. No differences in onset time, sensory and motor block and efficacy of analgesia have been reported. Two multicentre studies on labor analgesia reported again similar analgesic efficacy with a trend toward less motor block in parturients receiving levobupivacaine. CONCLUSIONS: This review has shown that levobupivacaine has a similar efficacy and a similar maternal fetal safety to that of bupivacaine. Further studies are needed to determine if the chemical properties of the new agent may influence the sensory and motor characteristics of the block.

[Motor block determination for the identification of accidental spinal injection of levobupivacaine: a study on the minimum efficient test-dose (ED50)]. / Determinazione del blocco motorio per l'identificazione della somministrazione spinale accidentale di levobupivacaina: studio sulla minima dose-test efficace (ED50).

BACKGROUND: The aim of this study was to determine the ED50 for the dose of levobupivacaine 0,5% that, if given intrathecally will not cause total spinal anesthesia but will give a reliable and reproducible clinical sign to differentiate intrathecal from epidural injection. METHODS: Thirty women at term undergoing elective cesarean section under a combined spinal-epidural technique (CSE) were enrolled into this sequential allocation study. The dose in each test dose was determined by the response of the previous patient to the higher or lower dose in her test syringe, according to up-down sequential allocation. The exception to this was the first woman in each group, for whom the starting dose was chosen to be 4 mg. The end point was the occurrence of any motor block, in any side, within 5 minutes from intrathecal injection of the test dose. Test dose efficacy was assessed using a modified Bromage scale every minute for 5 minutes. The median effective dose of levobupivacaine was estimated from the up-down sequences using the formula of Dixon and Massey. RESULTS: The MAD of the test dose for levobupivacaine was of 4,8 mg (4,4 to 5,2; 95% C.I.). DISCUSSIONS: This study may help to determine the appropriate dose for a test dose for inadvertent spinal levobupivacaine.

[Prehydratation and anaesthesia in obstetrics: state of the art]. / Preidratazione ed anestesia in obstetricia. Stato dell'arte.

All epidural or spinal techniques using local anaesthetics causes some degree of sympathetic blockade resulting in peripheral vasodilatation and possibly hypotension or reduction in cardiac output. In the practical clinic, administration of fluids intravenously prior spinal and epidural anaesthesia is required to prevent maternal hypotension and fetal hypoxia. We evaluated in this review the efficacy of volume preloading on the incidence of hypotension after spinal or epidural anaesthesia for caesarean delivery. Randomized controlled trials investigating volume preloading before the initiation of obstetric anaesthesia were sought by using MEDLINE (1966-2001). The primary outcome was the incidence of hypotension. Secondary outcomes included: ephedrine use, Apgar scores, umbilical cord pH values, and maternal nausea and vomiting. Crystalloid preload was inconsistent in preventing hypotension, whereas colloid appeared to be effective in all studies. A colloid solution, such as hydro-xyethyl starch (HES) might be preferable considering the capacity to stay intravasculary for a longer period. Few differences in fetal outcomes or maternal nausea and vomiting were reported. Increasing central blood volume by using colloid decreases the incidence of hypotension before loco-regional anaesthesia for cesarean delivery. Implications. We performed a review to determine whether fluid loading reduced the incidence of low blood pressure after spinal or epidural anaesthesia for caesarean delivery. Although no technique totally eliminates the occurrence of hypotension, colloid administration (starch or gelatin containing fluids) was the most effective.