M. Bahar

Neurotoxicity after spinal anaesthesia induced by serial intrathecal injections of magnesium sulphate An experimental study in a rat model

We have previously demonstrated in a rat model that the lumbar intrathecal injection of 0.02 ml 6.3% magnesium sulphate, a concentration iso‐osmolar with rat plasma, produces a state of spinal anaesthesia and general sedation which reversed completely after 6 h, without evidence of neurotoxicity, immediately or during the week thereafter. Using the same model and five groups of six animals in each, we administered the same volume and concentration of magnesium sulphate and compared its clinical effects with those of 0.02 ml 12.6% magnesium sulphate, 0.02 ml 2% lignocaine and 0.02 ml 0.9% sodium chloride solution, given as a series of 15 injections on alternate days for a period of 1 month. The animals were then killed and their spinal cords and meninges examined histologically. No significant differences were noted in the times of onset, durations of sensory and motor blockade and the times to full recovery throughout the entire period of 1 month’s observation in the animals receiving intrathecal 6.3% magnesium sulphate. In the group receiving 12.6% magnesium sulphate, the time of onset of sensory and motor blockade was shorter and the duration of both parameters was significantly longer than in the former group. Full clinical recovery and resumption of normal eating and drinking took place in both groups throughout the entire series of 15 successive intrathecal injections. Identical, mild, uniform histopathological changes in the spinal cord were seen in all the five groups, including the group in which only the intrathecal catheter was implanted. The complete recovery and benign consequences of repeated intrathecal injections of iso‐osmolar magnesium sulphate in a rat model indicate a lack of neurotoxicity and provide an impetus for further trials in larger animal species, before initial clinical trials of this substance, given intrathecally, in humans.

Characteristics of maternal heart rate patterns during labor and delivery.

OBJECTIVE To find patterns characteristic of maternal heart rates recorded by an electronic fetal monitor and compare them with concomitant fetal heart rate (FHR) patterns. METHODS Maternal heart rates and FHRs during active labor and delivery were simultaneously recorded in 26 parturients with singleton pregnancies in vertex presentation. The FHRs were obtained by an external ultrasound transducer or via a spiral scalp electrode and maternal heart rates by a triple‐wire cable with electrocardiographic electrodes attached to the chest. Representative tracings of 30–60 minutes duration were selected from all stages of labor and after delivery of the placenta. Quantitative assessments were carried out under guidelines from the National Institute of Child Health and Human Development after blinding the source of these tracings. Patterns were compared by appropriate statistical analyses. RESULTS Baseline maternal heart rates were significantly lower and their variability significantly higher than FHRs during all stages of labor. Maternal heart rates showed no decelerations; the proportion of tracings with accelerations increased as labor advanced, most of them coinciding with uterine contractions or bearing down efforts. The FHRs had both decelerations and accelerations. However, tracings with only accelerations (and no decelerations) were observed in decreasing frequency as labor advanced. Maternal accelerations had higher amplitudes and longer durations than fetal accelerations, especially in the second stage of labor. CONCLUSION Maternal heart rate patterns recorded by electronic fetal monitors closely resemble fetal patterns. Baseline “fetal bradycardia,” the absence of decelerations in the second stage of labor, and marked accelerations coinciding with uterine contractions may suggest a maternal heart rate rather than an FHR recording.

The lateral recumbent head-down position decreases the incidence of epidural venous puncture during catheter insertion in obese parturients.

PurposeThe unintentional and unrecognized cannulation of an extradural vein is a potentially serious complication of an epidural anesthetic. The present study was undertaken to assess the incidence of blood vessel puncture related to epidural catheterization in three different body positions, in a cohort of morbidly obese parturients, following the completion of a similar study published in 2001 from which such parturients were excluded.MethodsThe study was conducted in 450 (three groups of 150) morbidly obese, obstetric patients undergoing continuous epidural analgesia during labour. Epidural catheterization was performed on patients randomized to the sitting, lateral recumbent horizontal, or lateral recumbent head-down position.ResultsThere was a lower incidence of vessel cannulation when this procedure was performed in the lateral recumbent head-down position [1.3%; body mass index (BMI): 37.0] than in the lateral recumbent horizontal [12.9%; BMI: 38.0] and in the sitting position [12.0%; BMI: 38.0]. The incidence of accidental subarachnoid puncture was 2%, 1.3% and 2% respectively, in these same positions.ConclusionAdoption of the lateral recumbent head-down position for the performance of lumbar epidural blockade, in labour at term, reduces the incidence of lumbar epidural venous puncture in these obese parturients.RésuméObjectifLa canulation accidentelle et inaperçue d’une veine extradurale est une complication grave possible de l’anesthésie épidurale. Nous avons voulu évaluer l’incidence de ponction vasculaire reliée à la cathétérisation épidurale selon trois différentes positions du corps de parturientes avec obésité morbide, pour donner suite à une étude similaire publiée en 2001 et de laquelle ces parturientes avaient été exclues.MéthodeL’étude a été menée chez 450 (trois groupes de 150) patientes d’obstétriques très obèses devant subir une analgésie épidurale continue pendant le travail obstétrical. La cathétérisation a été réalisée chez les patientes randomisées pour adopter la position assise, décubitus latéral ou Trendelenburg latéral.RésultatsL’incidence de canulation vasculaire était plus faible en position de Trendelenburg latéral [1,3 %; indice de masse corporelle (IMC): 37,0] qu’en décubitus latéral [12,9 %; IMC: 38,0] ou en position assise [12,0%; IMC: 38,0]. L’incidence de ponction sousarachnoïdienne était de 2 %, 1,3 % et 2 % respectivement, dans ces mêmes positions.ConclusionL’adoption de la position de Trendelenburg latéral pour réaliser le bloc épidural lombaire, au terme du travail, réduit l’incidence de ponction veineuse épidurale lombaire chez ces patientes obèses.

Spinal anaesthesia with midazolam in the rat

PurposeThis study examined in an animal model whether intrathecal midazolam, alone or with fentanyl, can achieve anaesthesia sufficient for laparotomy, comparable to lidocame. Effects on consciousness and whether anaesthesia was segmental were also examined. The haemodynamic and respiratory changes were compared with those of intrathecal lidocame or intrathecal fentanyl alone.MethodsSixty Wistar strain rats, with nylon catheters chronically implanted in the lumbar subarachnoid theca, were divided into six groups. Group 1 (n = 12) received 75 μL intrathecal lidocame 2%. Group 2 (n = 12) received 75 μL intrathecal midazolam 0.1 %. Group 3 (n = 12) received intrathecal 37.5 μL midazolam 0.1 %, plus 37.5 μL fentanyl 0.005%. Group 4 (n = 12) received intrathecal 50 μL fentanyl 0.005%. Group 5 (n = 6) received 75 μL midazolam 0.1 %iv. Group 6 (n = 6) received halothane 0.6% in oxygen by inhalation.ResultsBoth groups that received intrathecal midazolam, alone or combined with fentanyl, developed effective segmental sensory and motor blockade of the hind limbs and abdominal wall, sufficient for a pain-free laparotomy procedure. Neither of these groups, unlike the group that received intrathecal lidocame, developed a reduction in blood pressure or change in heart rate at the time of maximal sensory or motor blockade, nor were there changes in the arterial blood gases or respiratory rate.ConclusionMidazolam. when injected intrathecally. produces reversible, segmental, spinally mediated antinociception, sufficient to provide balanced anaesthesia for abdominal surgery.RésuméObjectifUn modèle animal a servi à examiner si le midazolam sous-arachnoïdien seul ou avec du fentanyl pouvait produire une anesthésie comparable à celle de la lidocaïne et suffisante pour une laparotomie. Les effets sur la conscience ainsi que les caractéristiques segmentaires de l’anesthésie ont aussi été étudiés. Les changements hémodynamiques et respiratoires ont été comparés à ceux de la lidocaïne et du fentanyl sous-arachnoïdiens seuls.MéthodesSoixante rats de souche Wistar porteurs de cathéters sous-arachnoïdiens implantés ont été répartis entre six groupes. Le groupe I (n= 12) recevait 75 μL de lidocaïne sous-arachnoïdienne, le groupe 2 (n= 12) recevait 75 μL de midazolam sous-arachnoïdien. le groupe 3 (n= 12) recevait 37,5 μL de midazolam et 37,5 μL de fentanyl 0.005% sous-arachnoïdiens, le groupe 4 (n= 12) recevait 50μL de fentany 10,005% sous-arachnoïdien, le groupe 5 (n = 6) recevait 75 μL de midazolam intraveineux, le groupe 6 recevait de l’halothane 0,6% en oxygène par inhalation.RésultatsLes deux groupes qui avaient reçu du midazolam sous-arachnoïdien seul ou combiné au fentanyl ont eu une anesthésie efficace segmentaire sensitive et motrice du train posténeur et de la paroi abdominale suffisante pour une laparotomie. Aucun de ces groupes, contrairement au groupe qui avait reçu de la lidocaïne sous-arachnoïdienne, n’a présenté de chute de pression arténelle ou de changements de la fréquence cardiaque au moment du block sensitif et moteur maximum ni d’altérations de la gazométne arténelle et de la fréquence respiratoire.ConclusionLe midazolam sous-arachnoïdien produit une bloc nociceptif réversible, segmentaire, d’ongine rachidienne, suffisant pour procurer une anesthésie équilibrée et adéquate pour une chirurgie abdominale.

High-output left ventricular failure after dextran use in an operative hysteroscopy

High-output left ventricular failure occurred in a patient after a difficult case of hysteroscopic lysis of adhesions using dextran as a distension medium. The excessive dissection in the uterine wall, the long duration of the operation, and the large volumes of dextran probably caused intravasation of dextran into the systemic circulation inducing a significant shift of fluids from the third space. This was possibly assisted by the large volume of fluids given intravenously in a 45-kg patient initiating the reported sequence of events.

Lateral recumbent head-down posture for epidural catheter insertion reduces intravascular injection

Purpose: The unintentional and unrecognized cannulation of an extradural vein is a potentially serious complication of an epidural anesthetic. The present study was undertaken to assess the incidence of blood vessel puncture related to epidural catheterization performed in three different body positions. —Methods: The study was conducted in 900 (three groups of 300) obstetric patients undergoing continuous epidural analgesia during their labour and who were randomly allocated to three groups. Epidural catheterization was performed with patients in the sitting, lateral recumbent horizontal, or lateral recumbent head-down position.Results: There was a lower incidence of vessel cannulation when this procedure was performed in the lateral recumbent head-down position (2%) than in the lateral recumbent horizontal (6%) and in the sitting position (10.7%).Conclusion: Adoption of the lateral recumbent head-down position for the performance of lumbar epidural blockade, in labour at term, reduces the incidence of lumbar epidural venous puncture.RésuméObjectif: La canulation accidentelle et passée inaperçue d’une veine péridurale représente une complication potentiellement dangereuse de l’anesthésie épidurale. La présente étude évalue l’incidence de ponction vasculaire reliée au cathétérisme péridural réalisé selon trois positions corporelles différentes.Méthode: L’étude a été menée auprès de 900 patientes en obstétrique, trois groupes de 300 réparties au hasard, qui recevaient une analgésie épidurale pendant le travail. La mise en place d’un cathéter péridural a été réalisée en position assise, allongée sur le côté ou allongée sur le côté et tête vers le bas.Résultats: L’incidence de ponction vasculaire est plus faible, 2%, en position allongée avec la tête vers le bas, puis de 6% en position allongée sur le côté et de 10,7% en position assise.Conclusion: Pendant le travail dans le cas d’une grossesse à terme, l’adoption de la position allongée sur le côté et tête vers le bas, pour l’administration d’un bloc épidural, réduit l’incidence de ponction veineuse.

An investigation of the possible neurotoxic effects of intrathecal midazolam combined with fentanyl in the rat

In previous work, midazolam was injected intrathecally and produced reversible, segmental, spinally mediated anti-nociception sufficient for abdominal surgery in a rat model. The neurotoxic effect of midazolam, alone or combined with fentanyl, injected intrathecally repeatedly on 15 occasions over a period of 1 month, was studied in the same model. We sought to establish whether this would produce neurological damage or neurotoxic injury. Histopathological examination of the excised spinal cord and paraspinal tissues was carried out. Thirty Wistar strain rats with nylon catheters chronically implanted in the lumbar subarachnoid space were divided into five groups: group 1 (n = 6) received 40 microL of midazolam 0.1%; group 2 (n = 6) received 40 microL of fentanyl 0.005%; group 3 (n = 6) received 20 microL of midazolam 0.1% plus 20 microL of fentanyl 0.005%; group 4 (n = 6) received 40 microL of lignocaine 2%; group 5 (n = 6) received 40 microL of phenol in water. All substances were injected through the implanted catheters. The neurological recovery of all the animals in the four groups that received intrathecal midazolam alone, fentanyl alone, midazolam plus fentanyl and lignocaine alone was similar and complete. There were no significant differences in the histological changes in the neural tissues of these groups, despite repeated application of the test substances. Group 5 demonstrated the typical neurolytic lesions of phenol when injected intentionally into the subarachnoid space.

Dextran 40 (Rheomacrodex) or Polygeline (Haemaccel) as an epidural patch for post dural puncture headache: a neurotoxicity study in a rat model of Dextran 40 and Polygeline injected intrathecally.

Background and objective: Although an epidural autologous blood patch is considered the most effective treatment for post dural puncture headache, which sometimes occurs following spinal or inadvertent spinal anaesthesia, there remains a need for alternative materials for epidural patches. We investigated the potential neurotoxicity of Dextran 40 (Rheomacrodex) and Polygeline (Haemaccel) used for this purpose in a rat model. Methods: Repeated boluses of 10% Dextran 40, 3.5% Polygeline or 0.9% saline were injected intrathecally over a period of 1 month in three groups of rats. Results: No behavioural or clinical derangements were observed in any of the three groups during this period. After sacrifice of the animals at the end of the experiment, no significant differences in the histopathological appearances of the spinal cords in the three groups were observed. No toxic effects diminishing viability of spinal cord cells were evident. Similarly, viability of renal, hepatic and peripheral blood mononuclear cells remained unaffected (98% ± 2%). Conclusions: No deleterious effects, clinical or cellular, were evident in this rat model when Dextran 40 or Polygeline were injected intrathecally. Thus, both substances can be considered as possible alternative materials for epidural patches.

Fluid preload before spinal anaesthesia in Caesarean section: the effect on neonatal acid-base status.

Background and objective: We evaluated the effect of two different preload solutions: (i) Ringers lactate (compound sodium lactate intravenous infusion BP) and (ii) 0.9% sodium chloride solution on the neonatal acid–base status of the newborn infants. The two standard regimens were compared to detect a possible difference. Methods: A 2 L crystalloid fluid bolus was administered immediately before spinal anaesthesia for elective Caesarean section in two groups of 20 healthy parturients, while rigorously maintaining maternal normotension. Results: No significant differences in the Apgar scores at 1 and 5 min, or infant well‐being were demonstrated in either of the two groups. The data show that umbilical artery PCO2 is lower in the Ringers lactate group and that pH is insignificantly higher by 0.03. Conclusions: The choice of Ringers lactate or saline for fluid preload does not have any effect on neonatal well‐being.

RETRACTED: Accidental venous and dural puncture during epidural analgesia in obese parturients (BMI > 40 kg/m2): three different body positions during insertion

STUDY OBJECTIVE To assess the frequency of blood vessel punctures in morbidly obese parturients [body mass index (BMI) > 40 kg/m(2)] during epidural catheterization, in three different body positions. DESIGN Prospective, randomized study. SETTING Delivery room of a university-affiliated hospital. PATIENTS 347 obese parturients (BMI > 40 kg/m(2)) undergoing continuous epidural analgesia during labor. INTERVENTIONS Patients were randomized to undergo epidural catheterization in the sitting, lateral recumbent horizontal, or lateral recumbent head-down positions. MEASUREMENTS AND MAIN RESULTS A lower frequency of epidural venous cannulation was noted when this procedure was performed in the lateral recumbent head-down position (4.8%) than in the lateral recumbent horizontal (11.6%) or sitting position (18.3%) (P = 0.001). Frequency of accidental subarachnoid puncture did not differ significantly (2.5%, 2.6%, and 3.7%), respectively. CONCLUSION Adoption of the lateral recumbent head-down position for the performance of lumbar epidural blockade in labor at term reduces the frequency of lumbar epidural venous puncture in obese parturients (BMI > 40 kg/m(2)).