Sivam Ramanathan

Optimization of Arterial Oxygenation during One-lung Anesthesia

The effects of different respiratory maneuvers on Pao2, Qs/Qt, and cardiac output were studied during one-lung anesthesia in 21 adult patients undergoing pulmonary surgery in lateral position with halothane-oxygen anesthesia using endobronchial intubation. The patients were divided into three groups. In group A (n = 11) seven different respiratory maneuvers were sequentially performed. When both lungs were ventilated (maneuver A) Pao2 and Qs/Qt were 376 ± 28 torr (mean ± SE) and 26 ± 2.33% (mean ± SE), respectively. Corresponding values were 155 ± 25 torr and 38 ± 1.5% when the upper lung was deflated (maneuver B) and 85 ± 11 torr and 44 ± 4% when PEEP (10 cm H2O) was added to the dependent lung with the upper lung remaining deflated (maneuver C). When the collapsed upper lung was insufflated with oxygen (7 L/min) with the lower lung receiving PEEP (maneuver D) Pao2 and Qs/Qt were 127 ± 29 torr and 38 ± 3%, respectively, 177 ± 34 torr and 37 ± 3.5% when the upper lung was insufflated with oxygen and lower lung ventilated without end-expiratory pressure (maneuver E). When the upper lung was insufflated with oxygen at 10 cm H2O pressure with the dependent lung ventilated with PEEP (maneuver F), Pao2 was 248 ± 41 torr and Qs/Qt was 31 ± 2% and finally, during insufflation of the upper lung at 10 cm H2O pressure while the lower lung was ventilated with zero end-expiratory pressure (maneuver G) Pao2 averaged 286 ± 49 torr and Qs/ Qt 28 ± 2.5%. Cardiac output was reduced only when the dependent lung was ventilated with PEEP and the deflated upper lung insufflated with oxygen with or without pressure. In group B (n = 5) the effects of only maneuver F on arterial oxygenation were evaluated 50, 95, and 140 minutes after the start of anesthesia. In group C (n = 5), only maneuver G was studied 50, 95, and 140 minutes after the start of anesthesia. The values for Pao2 and Qs/Qt did not differ from each other at these time intervals and were comparable with the values obtained during corresponding maneuvers in group A patients. It is concluded that arterial oxygenation can be optimized during one-lung anesthesia by oxygen insufflation of the upper deflated lung at 10 cm H2O pressure while the lower lung is ventilated with zero end-expiratory pressure.

Postdural Puncture Headache: A Randomized Comparison of Five Spinal Needles in Obstetric Patients

This prospective, blinded, randomized study compares the incidence of postdural puncture headache (PDPH) and the epidural blood patch (EBP) rate for five spinal needles when used in obstetric patients. One thousand two women undergoing elective cesarean delivery under spinal anesthesia were recruited. We used two cutting needles: 26-gauge Atraucan and 25-gauge Quincke, and three pencil-point needles: 24-gauge Gertie Marx (GM), 24-gauge Sprotte, and 25-gauge Whitacre. The needle for each weekday was chosen randomly. Cutting needles were inserted parallel to the dural fibers. The incidences of PDPH were, respectively, 5%, 8.7%, 4%, 2.8%, and 3.1% for Atraucan, Quincke, GM, Sprotte, and Whitacre needles (P = 0.04, &khgr;2 analysis), and the corresponding EBP rates in those with PDPH were 55%, 66%, 12.5%, 0%, and 0% (P = 0.000). The Quincke needle had a more frequent PDPH rate than the Sprotte or the Whitacre needle (P = 0.02) and a more frequent EBP rate than the GM, Sprotte, or the Whitacre needle (P = 0.01). The Atraucan needle had a more frequent EBP rate than the Sprotte or Whitacre needle (P = 0.05). Neither the PDPH rate nor the EBP rates differed among the pencil-point needles. The cost of EBP must be taken into consideration when choosing a spinal needle. We conclude that pencil-point spinal needles should be used for subarachnoid anesthesia in obstetric patients. Implications We compared the rates of postdural puncture headache and epidural blood patch (EBP) with five different spinal needles in obstetric patients undergoing cesarean delivery. The least expensive Quincke needle had the highest postdural puncture headache and EBP rates. Patient discomfort as well as the cost of an EBP must be considered when choosing a spinal needle. Our results support using pencil-point spinal needles in obstetric patients.

Humidity and the anesthetized patient.

Damage to the ciliated cells of the tracheobronchial tree and incidence of postoperative pulmonary complications were measured ured by point-scoring systems in 202 patients who breathed dry and humidified anesthetic gases for 225±78 min. The incidence of postoperative pulmonary complications decreas

The Pall ultipor breathing circuit filter-an efficient heat and moisture exchanger

The Pall bacterial filter was tested as a potential heat and moisture exchanger on a model patient, placed on a circle absorber system, and clinically. The laboratory study was conducted during mechanical ventilation at a V of 6 L/min with fresh gas inflows of 1,3 and 6 L/min. The model patient introduced carbon dioxide into the circuitry at a rate of 200 ml/min. The resistance of the filter was tested before and after each experiment. With all fresh gas inflows, absolute humidity increased from around 19 mg H2O/L at the start of experimentation to about 27 mg H2O/L within 30 mm. Maximum humidities reached were 28 ± 0.7 mg H2O/L, 27.6 ± 0.5 mg H2O/L, and 27.7 ± 0.5 mg H2O/L within 3 hr, with fresh gas inflows of 1, 3, and 6 L/min, respectively. Variations in inspired humidity were also assessed at minute volumes of 4 and 5 L/min with fresh gas inflows of 6 and 3 L/min. Increases in percent dead space were negligible when the filter was inserted between the model patients (assumed to weigh between 70–40 kg) and the circuit. There was no statistically significant increase in pressure with gas flows of 50 L/min when the instrument was dry (0.02 ± 0.001 cm H2O/L-min−1) or when it was wet (0.02 ± 0.002 cm HzO/L-min−1). The clinical study was conducted on ten adult anesthetized patients breathing through the bacterial filter and ten controls. The loss of body temperature was 0.2°C when the filter was used and 1.5°C when the filter was not used. Arterial blood gas tensions were within normal limits when the bacterial filter was used as a humidifier.

Labour analgesia with intrathecal fentanyl decreases maternal stress

PurposeLumbar epidural analgesia (LEA) decreases maternal stress as measured by maternal circulating plasma catecholamine concentrations. Intrathecal fentanyl (ITF) provides effective labour analgesia but its effect on maternal epinephnne (Epi) and norepinephnine (NE) concentrations is not known. This study assesses whether ITF reduces maternal stress in the same manner as conventional LEA.MethodsTwenty-four healthy women in active labour received either 25 μ/g ITF (n = 12) or epidural lidocaine 1.5% (n = 12) for analgesia. Venous blood samples were collected before anaesthesia and at five minute intervals for 30 mm following anaesthesia for the measurement of plasma Epi and NE by high performance liquid chromatography. Maternal blood pressure (BP), heart rate (HR), visual analog scores (VAS) to pain and pruntus were recorded at the same time.ResultsBoth ITF and LEA decreased pain VAS scores, maternal BP, and plasma Epi concentrations with only minimal effects on plasma NE concentrations. Intrathecal fentanyl (ITF) and LEA reduced plasma epi to a similar extent, with ITF reducing the levels slightly faster than LEA. Intrathecal fentanyi(ITF) and LEA reduced plasma Epi concentrations by 52% and 51%, respectively (P value < 0.01).ConclusionWe conclude that ITF is as effective as LEA in producing pain relief in the labounng patient. Intrathecal Fentanyl (ITF) is also capable of reducing maternal plasma epmephnne concentration, thus avoiding the possibly deleterious side effects of excess amounts of this catecholamme during labour.RésuméObjectifL’analgésie épidurale lombaire (AÉL) diminue le stress maternel déterminé par le dosage des concentrations plasmatiques de catécholamines. Le fentanyl sous-arachnoïdien (FSA) procure une analgésie efficace pendant le travail mais on ne connaît pas son influence sur les concentrations maternelles d’épinéphnne (ÉPI) et de norépinéphnne (NÉ). Cette étude visait à déterminer si le FSA diminuait le stress de la même façon que l’AÉL.MéthodesVingt-quatre partunentes bien portantes en travail ont reçu pour l’analgésie soit du FSA 25 μg (n = 12) soit de la lidocaïne épidurale 1,5% (n = 12). Des échantillons de sang veineux ont été recueillis avant l’anesthésie et à des intervalles de cinq minutes pendant 30 min après l’anesthésie dans le but de mesurer l’ÉPI et la NF plasmatiques par Chromatographie en phase liquide à haute performance. En même temps, la pression artérielle (PA). la fréquence cardiaque et les scores d’une échelle visuelle analogique (ÉVA) pour la douleur et le prurit étaient enregistrés.RésultatsLe FSA et l’AÉL diminuent les scores d’ÉVA, la PA et les concentrations d’ÉPI avec des effets minimes sur les concentrations plasmatiques de NÉ. Le FSA et l’AÉL réduisent également l’ÉPI plasmatique. mais la réduction est un peu plus rapide avec le FSA. Le FSA et l’AÉL diminuent respectivement les concentrations de 51% et 52% (P < 0,01).ConclusionLe FSA est aussi efficace que l’AÉL pour soulager la douleur chez la partunente en travail. Le fentanyl sous-arachnoïdien diminue aussi les concentrations maternelles d’épinéphnne. protégeant ainsi la partunente en travail des effets nocifs de concentrations excessives de catécholamines.

Oxygen Transfer from Mother to Fetus During Cesarean Section Under Epidural Anesthesia

The correlation between maternal PaO2 levels and umbilical vein (UV) and umbilical artery (UA)PO2 levels was studied in 40 healthy patients undergoing elective cesarean sections under lumbar epidural anesthesia. Patients were divided into four equal groups. Each group inhaled oxygen at a FIO2 of 0.21, 0.47, 0.74 (in nitrogen), or 1.0. Maternal arterial samples and fetal UV and UA samples were collected at the time of delivery. Maternal PaO2 levels increased from 96 +/- 4 (1 SE) torr during exposure to to a FIO2 of 0.21 to 232 +/- 6, 312 +/- 16, and 423 +/- 6 torr while breathing FIO2 of 0.47, 0.74 and 1.0, respectively. UV PO2 levels increased from 28 +/- 1 to 36 +/- 1.5, 41 +/- 1.3 and 47 +/- 1.2 torr in the hyperoxic groups. UA PO2 levels increased from 15 +/- 0.7 to 19 +/- 0.8, 21 +/- 0.3, and 25 +/- 1.8 torr, respectively. Oxygen saturation and blood O2 contents increased in maternal and fetal blood. Maternal arterial, UV, and UA base excess values in the hyperoxic groups were significantly higher than in the normoxic groups. There was no difference in 1- or 5-minute Apgar scores between the normoxic and hyperoxic groups. It is concluded that maternal hyperoxia improves fetal oxygen stores and acid-base status during cesarean section under epidural anesthesia.

Effect of Epidural Analgesia with Ambulation on Labor Duration

BackgroundAmbulatory epidural analgesia (AEA) is a popular choice for labor analgesia because ambulation reportedly increases maternal comfort, increases the intensity of uterine contractions, avoids inferior vena cava compression, facilitates fetal head descent, and relaxes the pelvic musculature, all of which can shorten labor. However, the preponderance of evidence suggests that ambulation during labor is not associated with these benefits. The purpose of this study is to determine whether ambulation with AEA decreases labor duration from the time of epidural insertion to complete cervical dilatation. MethodsIn this prospective, randomized study, 160 nulliparous women with AEA were randomly assigned to one of two groups: AEA with ambulation and AEA without ambulation. AEA blocks were initiated with 15–20 ml ropivacaine (0.07%) plus 100 &mgr;g fentanyl, followed by a continuous infusion of 0.07% ropivacaine plus 2 &mgr;g/ml fentanyl at 15–20 ml/h. Maternal measured variables included ambulation time, time from epidural insertion to complete dilatation, stage II duration, pain Visual Analogue Scale scores, and mode of delivery. APGAR scores were recorded at 1 and 5 min. Results are expressed as mean ± SD or median and analyzed using the t test, chi-square, or the Mann–Whitney test at P ≤ 0.05. ResultsThe ambulatory group walked 25.0 ± 23.3 min, sat upright 40.3 ± 29.7 min, or both. Time from epidural insertion to complete dilatation was 240.9 ± 146.1 min in the ambulatory group and 211.9 ± 133.9 min in the nonambulatory group (P = 0.206). ConclusionAmbulatory epidural analgesia with walking or sitting does not shorten labor duration from the time of epidural insertion to complete cervical dilatation.

Epidural labor analgesia and neonatal sepsis evaluation rate: a quality improvement study.

Labor epidural analgesia (LEA) is allegedly associated with maternal fever and an increase in the newborn sepsis work-up (SWU) rate. In this study, we evaluated whether LEA causes an increase in the SWU rate compared with a Control group given parenteral narcotics for labor pain. Maternal and neonatal data were collected prospectively for a continuous quality improvement database. Odds ratios were calculated by using multiple logistic regression for various triggers for SWU in the neonate. Of the 1177 primiparous women and their neonates studied, 922 women received LEA and 255 women received parenteral analgesics. A small but statistically significant increase in maternal and neonatal temperatures occurred in parturients receiving LEA. The SWU rates were 7.5% in the LEA group and 9.4% in the Controls (not significant). Triggers identified for SWU were birth weight (odds ratio = 116, P = 0.000), gestational age (odds ratio = 86.6, P = 0.000), meconium aspiration and respiratory distress requiring intubation (odds ratio = 8.6, P = 0.000), hypothermia at birth (odds ratio = 7.1, P = 0.001), maternal Group B &bgr;-hemolytic streptococcal colonization (odds ratio = 6, P = 0.000), and preeclampsia or hypertension (odds ratio = 3.5, P = 0.03). There was no association between LEA and SWU.

Exposure to Halothane and Enflurane Affects Learning Function of Murine Progeny

This study was conducted to assess the learning function of murine progeny born of mothers that had received either 1 % or 2% halothane or 2% or 4% enflurane, on days 6 and 10 or days 14 and 17 of gestation. Their timed performance at the age of 6 to 7 weeks was compared in a maze with that of control mice of similar ages that had not been exposed to anesthetics prenatally. All mice exposed to halothane in utero performed poorly at first, especially the group with mothers exposed to 2% halothane on days 14 and 17 of pregnancy. By the 10th training period, the performance of all mice improved but remained significantly slower than control mice. The offsprings of mice exposed to enflurane also performed poorly on the first training period, but between the fifth and seventh training periods, made statistically significant progress. However, they too remained slower in maze performance than control mice. Although blood pressure and arterial blood gas studies were only performed on two pregnant mice, data obtained suggest that the anesthetics did not have sufficient effect on respiration to affect our results. Second generation offspring, born to dams exposed to 2% halothane in utero late in pregnancy and sired by normal unexposed males, were also consistently slower than control mice, indicating a possible genetic effect induced by the anesthetic.

Maternal and Fetal Effects of Prophylactic Hydration with Crystalloids or Colloids before Epidural Anesthesia

Prophylactic intravenous hydration decreases the incidence and severity of hypotension due to obstetric epidural anesthesia. This study assesses whether infusion of normal serum albumin (NSA) offers any advantages over Ringers lactate (RL) solution. Sixty patients scheduled for elective cesarean sections were divided into three equal groups. Group 1 received 1200 ml of RL; group 2, 700 ml of RL plus 500 ml of 5% NSA; and group 3, 1000 ml of RL plus 200 ml of 25% NSA. In group 1, the concentrations of serum albumin (SA) decreased from 3.5 ± 0.3 (mean ± SD) to 3 ± 0.2 g/dL (P < 0.01) and plasma oncotic pressure (POP) from 20 ± 3 to 17 ± 3 ton (P < 0.005) immediately after hydration. In group 2, SA remained unchanged, but POP decreased from 21 ± 2 to 19 ± 2 torr (P < 0.005). In group 3, SA increased from 3.6 ± 0.5 to 3.9 ± 0.3 g/dL (P < 0.01) and POP from 19 ± 2 to 21 ± 2 ton (P < 0.0025). Neither SA nor POP levels differed among the groups 24 h later; however, both SA and POP were significantly lower than preinfusion values in all groups at 24 h. The incidence of maternal hypotension, neonatal Apgar scores, and acid-base status also were comparable among the groups (X2 analysis). Because low POP may predispose to postoperative pulmonary morbidity, the incidence of this complication was studied in the mothers by using a point scoring system (based on the presence of symptoms and physical signs) and also by measuring AaDO2 gradients. Neither pulmonary morbidity scores nor AaDO2 gradients differed significantly in the three groups. It is concluded that both crystalloid and colloid prehydration produce equally satisfactory maternal and fetal outcomes.