Search

Maternal hypotension commonly occurs during spinal anesthesia for cesarean delivery, with a decrease of systemic vascular resistance recognized as a significant contributor. Accordingly, counteracting this effect with a vasopressor that constricts arterial vessels is appropriate, and the pure α-adrenergic receptor agonist phenylephrine is the current gold standard for treatment. However, phenylephrine is associated with dose-dependent reflex bradycardia and decreased cardiac output, which can endanger the mother and fetus in certain circumstances. In recent years, the older, traditional vasopressor norepinephrine has attracted increasing attention owing to its mild β-adrenergic effects in addition to its α-adrenergic effects. We search available literature for papers directly related to norepinephrine application in spinal anesthesia for elective cesarean delivery. Nine reports were found for norepinephrine use either alone or compared to phenylephrine. Results show that norepinephrine efficacy in rescuing maternal hypotension is similar to that of phenylephrine without obvious maternal or neonatal adverse outcomes, and with a lower incidence of bradycardia and greater cardiac output. In addition, either computer-controlled closed loop feedback infusion or manually-controlled variable-rate infusion of norepinephrine provides more precise blood pressure management than equipotent phenylephrine infusion or norepinephrine bolus. Thus, based on the limited available literature, norepinephrine appears to be a promising alternative to phenylephrine; however, before routine application begins, more favorable high-quality studies are warranted.

The Canadian Light Source booster synchrotron was originally commissioned in 2002 and has worked reliably for many years. However, the operating point was not the design operating point and the booster suffered from poor quantum lifetime at the extraction energy. The low quantum lifetime caused current loss of approximately 25% in the microseconds before extraction. We have recommissioned the booster using the design optics, and the current loss before extraction is now only 6%. In this paper, we discuss the measurements and simulations involved in our recommissioning work., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

In this paper, a 12 bit 500MS/s SHA-less ADC is described. The ADC has an integrated input buffer with a new linearization technique that improves its distortion. Eight pipeline stages with fully differential switched capacitor architecture follow the input buffer. Each of stage of the pipeline, excluding the last, consists of a low resolution flash ADC connected to a switched capacitor DAC and interstage residue amplifier(MDAC). A 0.18pm CMOS process with 3.3V/1.8V analog power supply is used in the design. This ADC achieves an SNR of 65dB and an SFDR of 82dB for sampling analog input frequencies up to 250MHz.

JUSTIFICATIVA E OBJETIVOS: A hipotensão materna associada à raquianestesia no parto cesáreo é a complicação mais frequente e problemática, com sérios riscos para a mãe e comprometimento do bem-estar neonatal. Nesse contexto, o volume efetivo de cristaloides por via intravenosa como uma estratégia de prevensão ainda não foi estimado. MÉTODOS: Oitenta e cinco parturientes com estado físico ASA I/II submetidas à cesariana seletiva foram selecionadas e 67 mulheres elegíveis foram designadas para receber uma pré-carga de cristaloides com 2 mL de bupivacaína hiperbárica a 0,5% (10 mg) mais 50 µg de morfina. O volume de cristaloides foi determinado por um método sequencial up-and-down. Os cristaloides foram infundidos a uma taxa de 100 a 150 mL.min-1 antes da anestesia espinal. O volume inicial de cristaloides foi de 5 mL.kg-1. Os dados do efeito do volume foram ajustados para o modelo sigmoidal de máxima eficácia e a mediana do volume efetivo (VE50) e seu intervalo de confiança (IC) de 95% foram calculados usando a estimativa de máxima verossimilhança e a regressão logística de Firth corrigida. RESULTADOS: Sessenta e sete parturientes completaram o estudo e foram analisadas. Vinte e oito pacientes (41,8%) desenvolveram hipotensão, com queda da pressão arterial sistólica (PAS) superior a 20% do valor basal. O VE50 de cristaloides foi de 12,6 mL.kg-1 (IC 95%, 11,6 a 14,8 mL.kg-1). Com a correção de Firth, a probabilidade conjunta do volume efetivo de cristaloides a 13 mL.kg-1 foi de 50,2% (IC 95%, 30,0% a 83,1%). CONCLUSÕES: O VE50 estimado da pré-carga de cristaloides necessário para prevenir a hipotensão induzida por anestesia espinhal em parto cesáreo é de 13 mL.kg-1 (valor aproximado). Porém, a profilaxia ou terapia com vasoconstritores também deve ser preparada e administrada no momento oportuno. BACKGROUND AND OBJECTIVES: Spinal anesthesia-associated maternal hypotension in Cesarean delivery is the most frequent and troublesome complication, posing serious risks to mothers and compromising neonatal well-being. The effective volume of intravenous crystalloid as the preventive strategy in this context has not been estimated. METHODS: Eighty-five parturients with ASA physical status I/II undergoing elective Cesarean delivery were screened and 67 eligible women were assigned to receive pre-spinal crystalloid loading. Hyperbaric 0.5% bupivacaine 2 mL (10 mg) plus morphine 50 µg was given to all patients. The volume of crystalloid was determined by an up-and-down sequential method. The crystalloid was infused at a rate of 100-150 mL.min-1 prior to the spinal anesthetic injection. The initial volume of crystalloid was 5 mL.kg-1. Volume-effect data were fitted to a sigmoidal maximum efficacy model and the median effective volume (EV50) and corresponding 95% confidence interval (95% CI) were estimated using maximum likelihood estimation and logistic regression with Firth's correction. RESULTS: A total of 67 subjects completed the study and were analyzed. Twenty-eight (41.8%) patients developed hypotension with their systolic blood pressure (SBP) decreasing > 20% of baseline. The EV50 of crystalloid were 12.6 mL.kg-1 (95% CI, 11.6 to 14.8 mL.kg-1). With Firth's correction, the pooled probability of an effective preventive volume of crystalloid at 13 mL.kg-1 was 50.2% (95% CI, 30% to 83.1%). CONCLUSIONS: The estimated EV50 of the preloaded crystalloid required to prevent spinal anesthesia-induced hypotension in a Cesarean section is, approximately, 13 mL.kg-1. However, prophylactic or therapeutic vasoconstrictors should also be prepared and administered at an appropriate time. JUSTIFICATIVA Y OBJETIVOS: La hipotensión materna asociada a la raquianestesia en el parto por cesárea es la complicación más común y problemática, acarreando serios riesgos para la madre y para el compromiso del bienestar neonatal. En ese contexto, el volumen efectivo de cristaloides por vía intravenosa como una estrategia de prevención todavía no ha sido estimado. MÉTODOS: Fueron elegidas ochenta y cinco parturientes con estado físico ASA I/II sometidas a la cesárea selectiva, y 67 mujeres elegibles fueron designadas para recibir una precarga de cristaloides con 2 mL de bupivacaína hiperbárica al 0,5% (10 mg) más 50 µg de morfina. El volumen de cristaloides quedó determinado por un método secuencial up-and-down. Los cristaloides fueron administrados a una tasa de 100 a 150 mL.min-1 antes de la anestesia espinal. El volumen inicial de cristaloides fue de 5 mL.kg-1. Los datos del efecto del volumen se ajustaron para el modelo sigmoidal de máxima eficacia y la mediana del volumen efectivo (VE50). El intervalo de confianza (IC) de 95% fue calculado usando la estimación de máxima verosimilitud y la regresión logística de Firth para la corrección. RESULTADOS: Sesenta y siete parturientes completaron el estudio y fueron analizadas. Veinte y ocho pacientes (41,8%) desarrollaron hipotensión, con una caída de presión arterial sistólica (PAS) superior al 20% del valor basal. El VE50 de cristaloides fue de 12,6 mL.kg-1 (IC 95%, 11,6 a 14,8 mL.kg-1). Con la corrección de Firth, la probabilidad conjunta del volumen efectivo de cristaloides a 13 mL.kg-1 fue de 50,2% (IC 95%, 30,0% a 83,1%). CONCLUSIONES: El VE50 estimado de la precarga de cristaloides necesario para prevenir la hipotensión inducida por anestesia espinal en el parto por cesárea es de 13 mL.kg-1 (valor aproximado). Sin embargo, la profilaxis o terapia con vasoconstrictores también debe ser preparada y administrada en el momento oportuno.