MRC2020: improvements to Ximdisp and the MRC image-processing programs.

The great success of single-particle electron cryo-microscopy (cryoEM) during the last decade has involved the development of powerful new computer programs and packages that guide the user along a recommended processing workflow, in which the wisdom and choices made by the developers help everyone, especially new users, to obtain excellent results. The ability to carry out novel, non-standard or unusual combinations of image-processing steps is sometimes compromised by the convenience of a standard procedure. Some of the older programs were written with great flexibility and are still very valuable. Among these, the original MRC image-processing programs for structure determination by 2D crystal and helical processing alongside general-purpose utility programs such as Ximdisp, label, imedit and twofile are still available. This work describes an updated version of the MRC software package (MRC2020) that is freely available from CCP-EM. It includes new features and improvements such as extensions to the MRC format that retain the versatility of the package and make it particularly useful for testing novel computational procedures in cryoEM.

Epidural hematoma following low molecular weight heparin prophylaxis and spinal anesthesia for cesarean delivery.

Epidural hematoma is a very uncommon complication of spinal anesthesia. Its incidence has been reported to be between 1:200 000-250 000 in the obstetric population following neuraxial anesthesia. Cesarean delivery increases the risk of maternal venous thromboembolism significantly and recommendations to decrease its incidence and morbidity have been developed. Strategies to decrease venous thromboembolism include pharmacologic prophylaxis with unfractionated or low molecular weight heparin. We report a case of spinal-epidural hematoma occurring in a parturient who received spinal anesthesia for a planned, repeat cesarean delivery after low molecular weight heparin thromboprophylaxis.

Use of transesophageal echocardiography for delivery of a parturient with severe pulmonary hypertension.

The anesthetic management of a parturient with severe pulmonary hypertension during labor and subsequent cesarean delivery is presented. Transesophageal echocardiography was used intraoperatively to manage the patient's hemodynamics, while pulmonary artery pressure monitoring was of little use. The benefits of transesophageal echocardiography for management of these patients are discussed.

Postcesarean epidural morphine: a dose-response study.

UNLABELLED: The purpose of this study was to describe the dose-response relationship of epidural morphine for postcesarean analgesia for quality of analgesia and relation to the side effects of pruritus, nausea, and vomiting. Sixty term parturients undergoing nonurgent cesarean delivery were enrolled and randomized to receive a single dose of epidural morphine after delivery (0,1.25, 2.5, 3.75, or 5 mg). A patient-controlled analgesia (PCA) device provided free access to additional analgesics. PCA morphine use and the incidence and severity of side effects were recorded for 24 h. Data were analyzed with analysis of variance, Student's t-tests, and chi(2) analysis. Nonlinear regression was used to describe a dose-response curve. PCA use differed significantly among groups (P < 0.001); PCA use was significantly greater in Group 0 mg than Groups 2.5, 3.75, and 5 mg (P < 0.05). PCA use was also significantly greater in Group 1.25 mg than Groups 3.75 and 5 mg (P < 0.05). Pruritus scores were significantly higher in all groups given epidural morphine than the control group (0 mg) (P < 0.05), but did not differ among the treatment groups (1.25-5 mg), although pruritus scores were significantly higher in treatment groups than in the control (P < 0. 05). No relation was found between epidural morphine dose and incidence or severity of nausea and vomiting. We concluded that, for optimal analgesia, augmentation of epidural morphine with systemic analgesics or other epidural medications may be necessary. IMPLICATIONS: Quality of analgesia increases as the dose of epidural morphine increases to at least 3.75 mg; increasing the dose further to 5 mg did not improve analgesia. Side effects were not dose related. For optimal analgesia, augmentation of epidural morphine with systemic analgesics or other epidural medications may be necessary.

Bupivacaine augments intrathecal fentanyl for labor analgesia.

BACKGROUND: fentanyl has been shown to be an effective analgesic for labor; this study investigated the analgesic effect of low-dose bpivacaine added to intrathecal fentanyl for labor analgesia METHODS: Ninety parturients in active labor who requested regional analgesia were randomized to receive an intrathecal injection of either fentanyl, 25 microg; bupivacaine, 1.25 mg, with fentanyl, 25 microg; or bupivacaine, 2.5 mg, with fentanyl, 25 microg, as part of a combined spinal-epidural technique. Visual analog pain scores were recorded before and at intervals after injection until the patient requested further analgesia. Maternal blood pressure and fetal heart rate were recorded before and at intervals after injection. Lower-extremity muscle strength was tested before and 30 min after injection; anesthetic level to cold sensation and the presence and severity of pruritus were recorded. RESULTS: Duration of analgesia was longer in the group receiving bupivacaine, 2.5 mg, and fentanyl, 25 microg, than the group receiving plain fentanyl (108 vs. 92 min; P < 0.05). Onset of analgesia was faster in both groups receiving bupivacaine compared with plain fentanyl (P < 0.05). No differences in muscle strength after injection were found in any group, although anesthetic levels to cold were documented in all patients in the bupivacaine groups, and 21 of 30 in the plain fentanyl group. Baseline fetal heart rates did not change after injection in any group, and maternal blood pressure was unchanged. CONCLUSIONS: The addition of 2.5 mg isobaric bupivacaine to 25 microg fentanyl for intrathecal labor analgesia modestly increases duration and speeds onset of analgesia compared with plain intrathecal fentanyl.

The incidence of fetal heart rate changes after intrathecal fentanyl labor analgesia.

UNLABELLED: We performed a retrospective review to compare the incidence of new fetal heart rate abnormalities after institution of either intrathecal fentanyl or conventional epidural labor analgesia. In chronological order, the first 100 parturients in active labor who had received epidural analgesia and had recorded fetal heart rate (FHR) traces for 30 min before and after injection were identified, as were the first 100 parturients who had received intrathecal fentanyl analgesia. A perinatologist blinded to the anesthetic technique evaluated each recording and identified any changes in the FHR between the before and after tracings. The incidence of new "negative" (implying worsened fetal status) changes was 6% in the epidural group and 12% in the intrathecal group (P > 0.05, not significant). There were no differences in incidence or degree of blood pressure change, need for cesarean delivery, neonatal outcome, parity, or oxytocin use. No parturient required urgent or emergent cesarean delivery, and all changes resolved within the 30-min observation period. A much larger study would be required to determine whether this six percentage point difference represents a true difference between groups, and its clinical significance. IMPLICATIONS: We compared the incidence of fetal heart rate changes after two techniques of labor analgesia. Both techniques were associated with a low (6%-12%) incidence of changes, but a much larger series would be required to determine whether this represents a true difference. No difference in neonatal outcome was found.

Dose-response relationship of intrathecal morphine for postcesarean analgesia.

BACKGROUND: This series investigated the quality of analgesia and the incidence and severity of side effects of intrathecal morphine for post-cesarean analgesia administered over a dose range of 0.0-0.5 mg. METHODS: ONE hundred eight term parturients undergoing cesarean delivery at term and given spinal anesthesia were randomized to receive a single dose of intrathecal morphine (0.0, 0.025, 0.05, 0.075, 0.1, 0.2, 0.3, 0.4, or 0.5 mg). A patient-controlled analgesia (PCA) device provided free access to additional analgesics. PCA morphine use, incidence and severity of side effects, and need for treatment interventions were recorded for 24 h. Data were analyzed with analysis of variance and linear regression analysis for trends among groups. RESULTS: Patient-controlled analgesia use differed significantly between groups; PCA use was higher in the control group than in groups receiving 0.075, 0.1, 0.3, 0.4, or 0.5 mg. Twenty-four-hour PCA morphine use was 45.7 mg lower (95% CI, 4.8-86.6 mg lower) in the 0.075-mg group than the control group. There was no difference in PCA morphine use between the 0.075- and 0.5-mg groups (95% CI, 36.8 mg lower to 45.0 mg higher); despite a fivefold increase in intrathecal morphine dose, PCA morphine use remained constant. There was no difference between control and treatment groups or among treatment groups with respect to nausea and vomiting. Pruritus and the need for treatment interventions increased in direct proportion to the dose of intrathecal morphine (linear regression, P = 0.001 and P = 0.0002, respectively). CONCLUSIONS: These data indicate there is little justification for use of more than 0.1 mg for post-cesarean analgesia. For optimal analgesia, augmentation [corrected] of intrathecal morphine with systemic opioids may be necessary.

The dose-response relation of intrathecal fentanyl for labor analgesia.

BACKGROUND: This study determined the dose-response relation of intrathecal fentanyl for labor analgesia and described the onset, duration, and quality of analgesia when used as the sole analgesic. METHODS: Eighty-four parturients in active labor who requested analgesia were randomized to one of seven treatment groups. They received 5-45 microg intrathecal fentanyl as part of a combined spinal-epidural technique. Visual analog pain scores were recorded before and at intervals after injection patients requested additional analgesia. The occurrence and severity of pruritus, nausea, and vomiting were also recorded. Maternal blood pressure was recorded before injection and at intervals after injection. Fetal heart rate was recorded before and 30 min after injection. RESULTS: By 5 min after injection, pain scores were significantly different among groups (P < 0.001). Mean duration of analgesia increased to 89 min as the dose increased to 25 microg. Maternal diastolic blood pressure was significantly lower 10 and 30 min after injection. There was no difference among groups in the incidence of pruritus; nausea and vomiting were uncommon. Fetal heart rates did not change after injection. A dose-response curve indicates that the median effective dose of intrathecal fentanyl for labor analgesia is 14 microg (95% confidence interval, 13-15 microg). CONCLUSIONS: Intrathecal fentanyl produces rapid, profound labor analgesia with minimal side effects. These data indicate that there is little benefit to increasing the dose beyond 25 microg when it is used as the sole agent for intrathecal labor analgesia.

Near ultraviolet radiation (UVA and UVB) causes a formamidopyrimidine glycosylase-dependent increase in G to T transversions.

In contrast to far-UV (< 290 nm) DNA damage, a large fraction of the DNA damage caused by near-UV is oxygen-dependent, suggesting the involvement of reactive oxygen species (ROS). The oxidized base 8-oxo-7,8-dihydroguanine (GO) is characteristic of ROS-induced DNA damage and is removed by Fapy (formamidopyrimidine) glycosylase. We have recently shown that Escherichia coli strains deficient in Fapy glycosylase (fpg) are hypersensitive to the lethal effects of UVA but not far-UV (UVC), suggesting lesions recognized by this enzyme may be important premutagenic or lethal lesions generated by near-UV radiation. In this study, we have found that while the far-UV-induced mutation rates of Fapy-deficient and wild-type strains were similar, near-UV (UVA and UVB) was hypermutagenic to a Fapy-deficient strain, causing a dose-dependent increase in induced mutation relative to wild type (up to five-fold at 200 kJ/m2). Using a plasmid back mutation assay, the predominant near-UV-induced mutations in both wild-type and Fapy-deficient strains were found to be C-->T transitions and G -->T transversions. The former is probably due to replicative bypass of pyrimidine dimers or (6-4) photoproducts that are known to be generated by near-UV, whereas the latter may be due to mispairing of GO lesions with adenine during replication. Consistent with this, the frequency of near-UV-induced G-->T transversions was 16-fold higher in a Fapy-deficient strain than a wild-type strain.

Role of Fapy glycosylase and UvrABC excinuclease in the repair of UVA (320-400 nm)-mediated DNA damage in Escherichia coli.

In contrast to the damage caused by far-UV, the damage caused by UVA (320-400 nm) is largely oxygen dependent, suggesting near-UV-mediated DNA damage involves reactive oxygen species. The DNA repair enzymes that recognize oxidized bases may, therefore, be an important part of the cell's near-UV defense repertoire. To evaluate the relative importance of Fpg (Fapy) glycosylase (an enzyme known to remove oxidized bases) and the DNA damage-inducible UvrABC excinuclease in recovery from near-UV-induced stress, we have constructed fpg- and uvrA- derivatives of Escherichia coli and tested the response (survival) of these strains to both UVA and far-UV radiation. Relative to control strains, the fpg- derivatives were found to be consistently more sensitive to the lethal effects of UVA, but not far-UV radiation. In contrast, uvrA- mutants were more sensitive than control strains to both UVA and far-UV radiation. Thymine dimers, known to be produced by far-UV and corrected by UvrABC, were not generated by the UVA fluences used in this study, suggesting that some other UVA-induced lesion(s) is recognized and repaired by this excinuclease.

Subarachnoid fentanyl augments lidocaine spinal anesthesia for cesarean delivery.

BACKGROUND AND OBJECTIVES: Fentanyl at doses of 6.25 microgram or more, when to hyperbaric bupivacaine for spinal anesthesia for cesarean delivery, has been reported to markedly increase the duration of analgesia. In this study, subarachnoid fentanyl 15 micrograms was evaluated as the sole adjunct to hyperbaric lidocaine spinal anesthesia in parturients undergoing cesarean delivery at term, to determine its effect on the duration of analgesia and side effects perioperatively. METHODS: Twenty-eight parturients scheduled for elective cesarean delivery at term were randomized to one of two groups in a prospective, double-blind fashion. Patients in group F received 15 micrograms fentanyl in addition to 80 mg hyperbaric lidocaine for subarachnoid anesthesia, while patients in group N received 0.3 mL normal saline in addition to 80 mg hyperbaric lidocaine. Visual analog pain scores were recorded preoperatively and at regular intervals until the first patient request for additional analgesia. The occurrence of side effects (nausea, vomiting, pruritus, shivering) was recorded at intervals for 4 hours postinduction. All patients received patient-controlled analgesia after delivery, and analgesic requirements for 24 hours postinduction were recorded. RESULTS: There was no difference between groups with respect to visual analog pain scores intraoperatively. The mean duration of effective analgesia was increased in the patients receiving fentanyl from 71 minutes to 101 minutes (Student's t-test, P < .01). No difference was observed between groups with regard to 4-hour or 24-hour analgesic requirements. Patients in group F were significantly less likely to experience nausea (Fisher's exact test, P < .05) and vomiting (chi-square test, P < .05) in the immediate perioperative period, but no differences were noted between groups in the incidence of pruritus or shivering. CONCLUSIONS: The addition of fentanyl 15 micrograms to hyperbaric lidocaine for subarachnoid anesthesia for cesarean delivery increases the duration of effective analgesia by approximately 30 minutes compared to plain hyperbaric lidocaine, and provides a protective effect regarding nausea and vomiting in the perioperative period.

Maternal electrocardiographic changes in the peripartum period.

Continuous electrocardiographic monitoring was performed in 20 term parturients during labor, vaginal delivery, and recovery. Mean duration of monitoring was 13.37 h. Sinus tachycardia was seen in all parturients (mean maximum heart rate=138); in 8 patients (40%), maximum heart rate was not attained until 0.5-5 h after delivery. Eight patients exhibited premature ventricular contractions or supraventricular tachycardia. ST-segment depression was noted in 3 patients (15%); in all 3, this was concurrent with maximum heart rate, was not associated with any symptoms, and occurred in the post-partum period.

Coagulation studies in the preeclamptic parturient: a survey.

STUDY OBJECTIVE: To delineate current practice with regard to how coagulation status is evaluated before induction of regional anesthesia in the preeclamptic parturient, with the goal of defining appropriate testing. DESIGN: A confidential survey was mailed to the chairmen of all 113 anesthesiology residency training programs in the United States listed in the American Medical Association's American Medical Graduation Education guide, to be passed on to the director of obstetric anesthesia. SETTING: Academic institutions providing obstetric anesthesia services in the United States. INTERVENTIONS: Following the original study, there was no additional follow-up or intervention. MEASUREMENTS AND MAIN RESULTS: The 21-question survey explored institutional characteristics such as the number of deliveries, the use of regional anesthesia, and the laboratory tests required prior to placement of a regional anesthetic in the mildly or severely preeclamptic parturient under two degrees of operative urgency. In the 74 programs entered into the analysis, we found that regional anesthesia was used in the majority of cesarean sections and more than half of the vaginal deliveries. In an urgent situation, most of the programs required no test of coagulation status in the mild preeclamptic parturient and only a platelet count in the severe preeclamptic parturient. CONCLUSIONS: In the majority of academic programs in the United States, we found that the evaluation of coagulation status in the preeclamptic parturient was based primarily on a platelet count. A review of the literature supports this pattern of testing.