Showing papers by "Mark D. Johnson published in 1990"

Method and apparatus for inducing anesthesia

Abstract: The present invention provides apparatus and methods for introducing spinal anesthesia directly into the subarachnoid space of a patient. One apparatus and method utilizes a small gauge spinal needle for penetrating the dura; the other utilizes a small gauge catheter with an internal stylet having a non-piercing pencil point to spread apart the filaments of the dura wall. An introducer having a rounded tip is also provided for guiding and supporting the spinal needle or catheter, as force is applied thereto, to cause the same to penetrate the dura.

The Prospective Use of Population Pharmacokinetics in a Computer-Driven Infusion System for Alfentanil

Abstract: Maitre et al. recently evaluated the accuracy of a set of previously determined population pharmacokinetic parameters for the opioid alfentanil using data from an earlier study in which the drug had been administered using a computer-controlled infusion pump (CCIP). The present study evaluated the accuracy of these same parameters in a CCIP prospectively in two groups of clinically dissimilar patients: 29 healthy female day surgery patients and 11 relatively older and less healthy male inpatients. In addition, another set of pharmacokinetic parameters, previously determined by Scott et al. in the CCIP in 11 male inpatients was also evaluated. The bias and inaccuracy were assessed by the median performance error (MDPE) and the median absolute performance error (MDAPE) in which the performance error was determined as the difference between measured and target serum concentration as a fraction of the target serum concentration. Unlike Maitre et al., the current study found a consistent bias in both populations. The MDPE was +53% and the MDAPE was 53%, with no difference between patient groups. In the 11 patients studied using the Scott et al. pharmacokinetic parameters, the MDPE was +1% and the MDAPE was 17%. The parameters of Scott et al. were further tested by simulating the serum concentrations that would have been achieved had they been used in the CCIP in the first 40 patients; results indicated MDPE of +2% and an MDAPE of 18%. Therefore, reasonably reliable and accurate target serum concentrations of alfentanil can be achieved using the pharmacokinetic parameters of Scott et al. in a CCIP.(ABSTRACT TRUNCATED AT 250 WORDS)

Spin‐polarized scanning tunneling microscope: Concept, design, and preliminary results from a prototype operated in air

Abstract: We describe the concept of the spin‐polarized scanning tunneling microscope. It consists of a ferromagnetic tip with saturated magnetization from which spin‐polarized electrons tunnel into a ferromagnetic sample which has its axis of magnetization aligned with that of the tip. When the magnetization of the sample is alternated periodically from parallel to antiparallel, a portion of the tunnel current is predicted to oscillate at the same frequency, with an amplitude linearly proportional to the average tunnel current. The construction of a prototype microscope, operated in air, is described. When the sample magnetization is alternated, a modulation of the tunnel current is observed at the same frequency. This signal satisfies criteria developed to characterize spin‐polarized tunneling. Spurious signals are also observed and their probable origins identified. A number of improvements are suggested that should eliminate the spurious effects.

Continuous Spinal Anesthesia With Combined Hyperbaric and Isobaric Bupivacaine in a Patient With Scoliosis

Abstract: We describe the anesthetic management of labor and cesarean delivery after failed epidural anesthesia using a continuous spinal technique with a combination of hyperbaric and isobaric local anesthetic solutions in a patient with severe kyphoscoliosis and congenital heart disease.

Chloroprocaine antagonism of epidural opioid analgesia: a receptor-specific phenomenon?

Abstract: Sixty healthy patients scheduled for elective cesarean delivery under epidural anesthesia were randomized to receive either lidocaine or 2-chloroprocaine as the primary local anesthetic agent. When patients first complained of postoperative pain in the recovery room, they were given either fentanyl 50 micrograms or butorphanol 2 mg, epidurally, in a randomized, blinded fashion. Postoperative analgesia, quantitated on a visual analogue scale, as well as time elapsed until first request for supplemental opioid, did not differ for patients receiving butorphanol after either 2-chloroprocaine or lidocaine anesthesia. In contrast, epidural fentanyl produced a shorter and lesser degree of sensory analgesia after 2-chloroprocaine use, whereas epidural fentanyl after lidocaine anesthesia provided pain relief similar to that seen in the butorphanol groups. Side effects were limited to somnolence with butorphanol and pruritus with fentanyl. No evidence of respiratory depression was seen in any patient. We conclude that 2 mg of butorphanol epidurally provides approximately 2 to 3 h of effective analgesia after cesarean delivery with either lidocaine or 2-chloroprocaine anesthesia. Epidural fentanyl seems to be antagonized when 2-chloroprocaine, but not lidocaine, is used as the primary local anesthetic agent. We suggest a possible mu-receptor-specific etiology for this effect.

Anaesthetic management of myocardial infarction in a parturient

Abstract: Myocardial infarction is encountered rarely during pregnancy, but when it occurs the event is life-threatening to both mother and fetus. Data on maternal and fetal outcome are limited, but overall maternal mortality approaches 35%, and 40% of deaths occur during the third trimester. We present a case of myocardial infarction occurring at 38 weeks gestation, and discuss the anaesthetic management of the problems encountered during labour and delivery.

Role of calcium in adrenergic neurochemical transmission in the aging heart.

Abstract: The effect of modification of extracellular Ca2+ concentration ([Ca2+]0), the administration of the neuronal Ca2+ channel blocker, omega-conotoxin, and the calcium (Ca2+) ionophore, ionomycin, were examined in the isolated heart of male Fisher-344 rats 6 and 24 months of age. Hearts with the right cardiac sympathetic nerve intact were isolated and perfused with Krebs-Ringer solution containing cocaine (10(-6) M) to block uptake 1, metanephrine (10(-6) M) to block uptake 2 and yohimbine (3 X 10(-6) M) to prevent alpha 2 receptor inhibition of Ca2+ influx. The nerve was stimulated with frequencies of 2, 6 and 12 Hz for 1 min and NE output was determined by high-performance liquid chromatography/electrochemical methods. Effluent of hearts from 6-month-old rats contained higher levels of NE than effluent of hearts from 24-month-old rats at all frequencies of stimulation when perfused with either normal (1.2 mM), low (0.3 mM) or high (4.8 mM) [Ca2+]0. Even when high [Ca2+]0 was used to make more Ca2+ available, the amount of NE in the effluent of 24-month-old animal hearts was only approximately 54% of that found in the effluent of 6-month-old animal hearts perfused with normal [Ca2+]0. omega-Conotoxin caused a greater decrease in NE release in the older preparations suggesting that the neuronal Ca2+ channels of older preparations are more susceptible to blockade than those of younger preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

The Effect of Epidural Sufentanil on Shivering and Body Temperature in the Parturient

Abstract: Temperature regulation is primarily controlled by the thermoregulating centers in the hypothalamus (1). Thermoreceptors in the skin and spinal cord provide afferent signals to the thalamus and hypothalamus. In addition, central thermoreceptors are sensitive to local core temperature. Stimulation of receptors in the anterior hypothalamus initiates anti-increase (in temperature) responses (vasodilation, sweating), whereas stimulation of the posterior hypothalamic receptors initiates the anti-decrease responses of vasoconstriction, epinephrine release, and shivering (2). Narcotics alter body temperature in animals (3). Possible mechanisms for this include centrally mediated alteration of thermogenesis (4) and peripheral effects altering the distribution of and rate of change of body heat (5). We have observed in a preliminary report a decrease in body temperature and a reduction in shivering in postpartum patients who received epidural sufentanil after epidural lidocaine anesthesia for cesarean delivery (6). To determine the effect of different doses of epidural sufentanil on body temperature, we undertook a randomized double blind study in patients undergoing cesarean delivery.

Continuous Spinal Anesthesia With Combined Hyperbaric and Isobaric Bupivacaine in a Patient With Scoliosis

Abstract: We describe the anesthetic management of labor and cesarean delivery after failed epidural anesthesia using a continuous spinal technique with a combination of hyperbaric and isobaric local anesthetic solutions in a patient with severe kyphoscoliosis and congenital heart disease.

Precordial Doppler Monitoring and Pulse Oximetry During Cesarean Delivery: Detection of Venous Air Embolism

Abstract: Venous air embolism (VAE) is a potential but rare complication of cesarean delivery that can be associated with morbidity and death. Uterine sinuses are susceptible to the entrance of air during cesarean delivery. To define the incidence of VAE and its relation to arterial oxygen saturation (SaO2) and consequent electrocardiographic (ECG) changes, a prospective study was undertaken in which precordial Doppler monitoring was conducted during cesarean delivery. Concomitant, SaO2 and ECG were recorded in 78 patients. Fifty-one of 78 (65%) of the subjects had Doppler changes consistent with VAE. Of these, 37 patients (72%) showed a decreased SaO2, (average decline 5.2%). The remainder of the patients with Doppler changes showed no SaO2 change. Twenty of the patients with Doppler changes and decreased SaO2 complained of chest pain and dyspnea. Three of these patients exhibited ECG changes including ST segment depression. Although all ECG changes resolved spontaneously without sequelae, the potential clearly existed for life threatening embolic events. Thus, precordial Doppler monitoring of cesarean delivery patients demonstrated a surprisingly high incidence of Doppler changes consistent with VAE. Some episodes were associated with a significant reduction in SaO2 and rarely with ECG changes.

Reversal of Bupivacaine Epidural Anesthesia by Intermittent Epidural Injections of Crystalloid Solutions

Abstract: This study was designed to determine whether epidural motor blockade could be reversed by postoperative injections of crystalloid solutions via the epidural catheter. Twenty-seven patients (ASA physical status I, nonlaboring) had epidural anesthesia with 0.75% bupivacaine for elective cesarean delivery. Postoperatively, patients were randomized to receive three 15-mL injections (over 30 min) of crystalloid solutions (normal saline or Ringer's lactate) or no treatment (control) via the epidural catheter. Degree of motor and sensory blockade was evaluated with an investigator blinded to treatment group. Rate of resolution of sensory blockade was not different among groups. However, time for resolution of motor blockade was more than twice as long in the control group than in either treatment group (control = 178 ± 70 min vs Ringer's lactate = 84 ± 44 min, normal saline = 70 ± 38 min, P = 0.001). The data suggest that unwanted motor blockade due to epidural anesthesia can be reversed by epidural injections of crystalloid solutions.

Anesthetic management of a parturient with myotonia dystrophica: a case report.

Abstract: We report the case of a 22-year-old parturient with myotonia dystrophica. She underwent two separate intraabdominal surgical procedures in one day, both under lumbar epidural anaesthesia. Management was directed toward prevention of shivering, a known trigger of myotonic crises. Measures used included warm ambient atmosphere, warmed IV fluids, warming blankets and administration of epidural sufentanil, an opioid recently ascribed as an inhibitor of shivering in parturients.

Ferrari et al. reply.

Abstract: A reply to the comment on flux pinning energies in high-{ital T}{sub {ital c}} superconductors is given. The extraction of flux-pinning energies from different types of measurements remains a highly contorversial issues. (AIP)