[Neuraxial Morphine for Postoperative Analgesia after Caesarean Deliveries]. / Neuroaxiale Gabe von Morphin nach Sectio caesarea: ein Update.

The use of neuraxial morphine, in combination with nonopioid analgesic regimens for postoperative analgesia after Caesarean deliveries is common practice, especially in the Anglo-American world. Neuraxial morphine offers a longer-lasting superior analgesia than intravenous opioids or patient-controlled analgesia. If neuraxial anaesthesia is being used for a caesarean delivery, it may be recommended to concomitantly administer neuraxial morphine for the postoperative analgesia.A low dose of neuraxial morphine in a healthy parturient bears a low morbidity and mortality risk. The optimal frequency, duration and modality of respiratory monitoring for patients at low risk for respiratory depression is dependent on the dose of morphine administered and the patient-specific and obstetric risk profile.

C-Shaped Scotoma after Complicated Cesarean Section: A Case of Acute Macular Neuroretinopathy.

Acute macular neuroretinopathy (AMN) is a rare retinal disease that produces transient or permanent visual impairment and occurs predominantly in young, Caucasian women of childbearing age. It is often characterized by wedge-like macular lesions. Although the cause of AMN is unknown, recent research suggests a microvascular etiology. Various vascular pathologies, including post-viral illness, oral contraceptives, and use of vasoconstrictive agents, have been associated with AMN. We present a case of a woman with C-shaped visual field defects in both eyes after inadvertent exposure to intravenous high-dose epinephrine during onset of spinal anesthesia. At present, only 8 cases of AMN after exposure to epinephrine have been described in literature. To our knowledge, this is the first case of AMN that presented following epinephrine injection during childbirth.

Cerebrospinal fluid levels of tau and phospho-tau-181 proteins during pregnancy.

OBJECTIVES: During pregnancy various interactions occur between structural alterations of the maternal brain and placental metabolism. The aim of the present study was to investigate whether cerebrospinal fluid concentrations of tau and phospho-tau-181 protein vary during normal pregnancy and in women with preeclampsia and HELLP syndrome. STUDY DESIGN: We measured cerebrospinal fluid biomarkers, tau and phospho-tau-181 protein levels in 90 pregnant women electively assigned for regional anaesthesia during pregnancy or for cesarean section using enzyme-linked immunosorbent assays. RESULTS: Cerebrospinal fluid concentrations for tau and phospho-tau-181 in 66 women with normal pregnancy were 308.5±117.3pg/mL and 50.5±16.7pg/mL, respectively. Blood pressure, liver function, clotting activity and kidney function were significantly different in eleven women with preeclampsia and HELLP syndrome. The weight of the newly born (p<0.001; HR: 0.998), the weight of the placenta (p=0.018) and concentrations for phospho-tau-181 (p=0.043; HR: 1.211) correlated significantly with the disease. CONCLUSION: Mean concentrations of cerebrospinal fluid tau and phospho-tau-181 protein during pregnancy were evaluated. Phospho-tau-181 protein concentrations correlated with placental function supporting the hypothesis that altered expression of neuronal factors during pregnancy may affect development of the placenta.

Head position angles to open the upper airway differ less with the head positioned on a support.

INTRODUCTION: The aim of the study was to assess the effects of positioning the head on a support on "head position angles" to optimally open the upper airway during bag-valve mask ventilation. METHODS: We ventilated the lungs of anesthetized adults with a bag-valve mask and the head positioned with (n = 30) or without a support (n = 30). In both groups, head position angles and ventilation parameters were measured with the head positioned in (1) neutral position, (2) in a position deemed optimal for ventilation by the investigator, and (3) in maximal extension. RESULTS: Between groups ("head with/without a support") and between head positions within each group, head position angles and ventilation parameters differed (P < .0001, respectively). However, head position angles and ventilation parameters between head positions differed less "with a support" (P < .001), and ventilation parameters improved with a support compared with the head-without-a-support group (P < .001). CONCLUSIONS: In the head-with-a-support group, when compared with the head-without-a-support group, head position angles differed less, indicating a decreased potential for failure during bag-valve mask ventilation with the head on a support. Moreover, in the head-with-a-support group, ventilation parameters differed less between head positions, and ventilation improved. These findings suggest a potential benefit of positioning the head on a support during bag-valve mask ventilation.

Effects of cholesterol on surface activity and surface topography of spread surfactant films.

Pulmonary surfactant forms a monolayer of lipids and proteins at the alveolar air/liquid interface. Although cholesterol is a natural component of surfactant, its function in surface dynamics is unclear. To further elucidate the role of cholesterol in surfactant, we used a captive bubble surfactometer (CBS) to measure surface activity of spread films containing dipalmitoylphosphatidylcholine/1-palmitoyl-2-oleoylphosphatidylcholine/1-palmitoyl-2-oleoylphosphatidylglycerol (DPPC/POPC/POPG, 50/30/20 molar percentages), surfactant protein B (SP-B, 0.75 mol %), and/or surfactant protein C (SP-C, 3 mol %) with up to 20 mol % cholesterol. A cholesterol concentration of 10 mol % was optimal for reaching and maintaining low surface tensions in SP-B-containing films but led to an increase in maximum surface tension in films containing SP-C. No effect of cholesterol on surface activity was found in films containing both SP-B and SP-C. Atomic force microscopy (AFM) was used, for the first time, to visualize the effect of cholesterol on topography of SP-B- and/or SP-C-containing films compressed to a surface tension of 22 mN/m. The protrusions found in the presence of cholesterol were homogeneously dispersed over the film, whereas in the absence of cholesterol the protrusions tended to be more clustered into network structures. A more homogeneous dispersion of surfactant lipid components may facilitate lipid insertion into the surfactant monolayer. Our data provide additional evidence that natural surfactant, containing SP-B and SP-C, is superior to surfactants lacking one of the components, and furthermore, this raises the possibility that the cholesterol found in surfactant of warm-blooded mammals does not have a function in surface activity.

In vitro and in vivo intrapulmonary distribution of fluorescently labeled surfactant.

OBJECTIVE: To determine the distribution of endotracheally administered surfactant at the alveolar level in an animal model of acute respiratory distress syndrome. DESIGN: Prospective, randomized animal study. SETTING: Research laboratory of a university hospital. SUBJECTS: Seventy-one male Sprague-Dawley rats, weighing 330-370 g. INTERVENTIONS: To measure surfactant distribution in vitro, a glass trough mimicking dichotomic lung anatomy was used to determine the spreading properties of bovine lung surfactant extract supplemented with fluorescent Bodipy-labeled surfactant protein B. To measure surfactant distribution in vivo, rats were anesthetized, and lipopolysaccharide was aerosolized (12 mg/kg body weight) to induce lung injury resembling acute respiratory distress syndrome; in control rats, buffered saline was aerosolized. Twenty-four hours later rats were anesthetized, tracheotomized, and mechanically ventilated (peak airway pressure = 20 mbar; positive end-expiratory pressure = 6 mbar; inspiration time = expiration time = 0.6 sec; Fio2 = 50%). Surfactant (bovine lung surfactant extract, supplemented with fluorescent Bodipy-labeled surfactant protein B; 50 mg/kg body weight) was applied as a bolus; in control rats, saline was administered as a bolus. Rats were ventilated for 5, 15, 30, or 60 mins (n = 8 or 9 for each group). Then, lungs were excised and sliced. Lung slices, divided into aerated (open), underinflated (dystelectatic), or collapsed (atelectatic) alveolar areas, were examined by both light and fluorescence microscopy. RESULTS: In vitro experiments revealed that surfactant spread independent of glass trough geometry and lowered the surface tension to equilibrium values (25 mN/m) within a few seconds. In vivo experiments showed that administered surfactant distributed preferentially into underinflated and aerated alveolar areas. Furthermore, surfactant distribution was not affected by length of mechanical ventilation. CONCLUSIONS: When conventional mechanical ventilation was used in lipopolysaccharide-induced lung injury, surfactant preferentially distributed into underinflated and aerated alveolar areas. Because surfactant rarely reached collapsed alveolar areas, methods aiding in alveolar recruitment (e.g., open lung concept or body positioning) should precede surfactant administration.

Multilayer formation upon compression of surfactant monolayers depends on protein concentration as well as lipid composition. An atomic force microscopy study.

The determinants for the formation of multilayers upon compression of surfactant monolayers were investigated by compressing films, beyond the squeeze-out plateau, to a surface tension of 22 millinewtons/m. Atomic force microscopy was used to visualize the topography of lipid films containing varying amounts of native surfactant protein B (SP-B). These films were compared with films containing synthetic peptides based on the N terminus of human SP-B: monomeric mSP-B-(1-25) or dimeric dSP-B-(1-25). The formation of typical hexagonal network structures as well as the height of protrusions were shown to depend on the concentration of SP-B. Protrusions of bilayer height were formed from physiologically relevant concentrations of 0.2-0.4 mol % (4.5-8.5 wt %) SP-B upwards. Much higher concentrations of SP-B-(1-25) peptides were needed to obtain network structures, and protrusion heights were not equal to those found for films with native SP-B. A striking observation was that while protrusions formed in films of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/1,2-dipalmitoyl-sn-glycero-3-(phospho-rac-(1-glycerol)) (DPPG) (80/20) had single bilayer thickness, those formed in DPPC/1-palmitoyl-2-oleoyl-sn-glycero-3-(phospho-rac-(1-glycerol)) (80/20) had various heights of multilayers, whereas those seen in DPPC/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/DPPG (60/20/20) were mainly of bilayer height. For the first time direct observations by atomic force microscopy show (i) that a certain minimal concentration of SP-B is required for the formation of layered protrusions upon film compression, (ii) that protrusion height depends on whether the phospholipids contain an unsaturated fatty acyl chain, and (iii) that protrusion height also depends on whether the unsaturated acyl chain is present in phosphatidylcholine or in phosphatidylglycerol.