Optically Stimulated Luminescence Dating Supports Central Arctic Ocean CM-scale Sedimentation Rates

This paper presents new results from Optically Stimulated Luminescence (OSL) dating on a sediment core raised from the crest of the Lomonosov Ridge in the central Arctic Ocean. There has been much debate about dating sediment cores from the central Arctic Ocean and by using an independent absolute dating technique we aim to test whether or not relatively fast, cm-scale/ka, sedimentation rates were typical of Arctic’s Pleistocene depositional mode. On the basis of mainly paleomagnetic reversal stratigraphy, many previous studies suggest mm-scale/ka sedimentation rates. A common feature in these studies is that the first down core paleomagnetic negative inclination is consistently interpreted as the Brunhes/Matuyama boundary at about 780 ka. Our OSL dating results indicate that this assumption is not generally valid, and that the first encountered negative inclination represents younger age excursions within the Brunhes Chron, implying reinterpretation of many published core studies where paleoenvironmental reconstructions have been made for the central Arctic Ocean. Our dating results furthermore corroborates a correlation of the uppermost 2–3 m of the Lomonosov Ridge cores to a well-dated core located off the Barents-Kara Sea margin that in turn is correlated to cores in the Fram Strait. Valuable information on the paleoceanographical evolution in the Arctic Ocean from MIS 6 to the Holocene is given through this correlation of records from the central Arctic Ocean to records off the Eurasian continental margin

Paleomagnetic Chronology of Arctic Ocean Sediment Cores: Reversals and Excursions -The Conundrum

Chronologies of Arctic Ocean sediment cores are mainly based on interpretation of paleomagnetic inclination records. The first paleomagnetic chronology assigned zones with negative inclinations to polarity reversals (Steuerwald et al, 1968) because geomagnetic excursions at that time were a novel observation and had only been reported from lavas. Arctic Ocean sedimentation rates were thus established to be in the mm/ka-range. A general recognition of excursions as real features of the geomagnetic field emerged more than three decades later, and presently there is still no consensus regarding the number (or name), duration and age of global synchronous excursions within the Brunhes Chron. Assigning inclination records to polarity reversals or excursions is an ambiguous exercise without independent age information. Based on independently derived time frames, 11 negative inclination intervals in core 96/12-1pc from the Lomonosov Ridge were assigned to reported excursions resulting in cm/ka deposition rates (Jakobsson et al, 2000). However, the detail of the excursional stratigraphy in this core is problematic. The absence of two (three?) excursions in the upper 2 m of core (base MIS5) was tentatively suggested to reflect pDRM-erasing in this sandy part of the core, while the short extent of the inferred pre-Brunhes Matyuama Chron remains unaccounted for. We have recently retrieved a relative paleointensity record from a parallel core (96/B6-1pc) for alternative dating control and assessment of stratigraphic completeness and uniformity of deposition. This study indicated the presence of a hiatus of the order of 200 ka (Løvlie et al 2002). We present a paleointensity record from core 96/12-1pc and will address identification of depositional hiatuses and their significance in understanding the paleomagnetic record in Arctic Ocean core

Circulatory collapse following epidural bolus for Caesarean section a profound vasovagal reaction? A case report

AbstractIntroductionReduced blood pressure is commonly seen associated to spinal anaesthesia for Caesarean section and efforts to reduce its occurrence and its magnitude is common practice. Cardiovascular collapse requiring cardio-pulmonary resuscitation after putting the spinal/epidural block for Caesarean section is however a rare but most dramatic event.Presentation of caseWe describe a case with sudden short loss of circulation, circulatory collapse, short after start of emergency Caesarean section in top up epidural anaesthesia (3+12ml ropivaciane 7.5mg/ml), requiring CPR. The neonate was delivered during CPR with Apgar 1, 10, 10 at 1, 5 and 10min. Circulation was restored following 60–90s of CPR and administration of 0.5mg adrenaline. No cardioversion was administered sinus rhythm was regained spontaneously. The mother and child had a further uncomplicated course. No signs of cardiac damage/anomaly, emboli, septicaemia, pereclampisa or local anaesthetic toxicity was found. The patient had prior to the decision about Caesarean section had fever and was subsequently relatively dehydrated.DiscussionThe patient had a fast return of sinus rhythm following birth of the child, without cardioversion. None of common causes for cardiac arrest was found and the patient an uncomplicated post Caesarean section course. The combination of epidural induced sympathetic block and reduced preload possibly triggered a Bezold-Jarisch reflex with a profound vasovagal reaction.ConcluiosnA structured plan for the handling of cardiovascular crisis must be available wherever Caesarean section are performed. Adequate volume loading, left tilt and vigilant control of circulation following regional block performance is of outmost importance

Multi-modal-analgesia for pain management after Hallux Valgus surgery: a prospective randomised study on the effect of ankle block

<p>Abstract</p> <p>Background</p> <p>Pain and emesis are the two major complaints after day case surgery. Local anaesthesia has become an important part of optimizing intra and post-operative pain treatment, but is sometimes not entirely sufficient. The aim of the present study was to study the effect of adding an ankle block to a multi-modal analgesic approach on the first 24-hour-need for rescue analgesia in patients undergoing elective Hallux Valgus surgery.</p> <p>Type of study</p> <p>Prospective, randomized patient-blind study comparing ankle block with levo-bupivacaine, lidocaine and Saline placebo control.</p> <p>Methods</p> <p>Ninety patients were studied comparing ankle block (15 cc) using levo-bupivacaine 2.5 mg/ml, lidocaine 10 mg/ml or placebo (saline) on day-case elective Hallux Valgus surgery, supported by general anaesthesia in all cases. Primary study endpoint was number of patient's requiring oral analgesics during the first 24 post-operative hours.</p> <p>Results</p> <p>Ankle block had no effect on need for rescue analgesia and pain ratings during the 1^st24 postoperative hours, there was no difference seen between placebo and any of the two active local anaesthesia studied. The only differences seen was that both lidocaine and levo-bupivacaine reduced the intra-operative need for anaesthetic (sevoflurane) and that levo-bupivacaine patients had a lower need as compared to the lidocaine patients for oral analgesics during the afternoon of surgery.</p> <p>Conclusion</p> <p>Adding a single shot ankle block to a multi-modal pain management strategy reduces the need for intra-operative anaesthesia but has no major impact of need of rescue analgesics or pain during the first 24-hour after surgery.</p

Day surgery, variations in routines and practices a questionnaire survey

AbstractBackgroundDay surgery is expanding however little is known about every day practice and routines.MethodsA web-based questionnaire including 34 questions with fixed multiple choice responses around routine and practice for the perioperative handling of patients scheduled for day case surgery was send to 100 hospitals.ResultsThere was an overall response rate of 70%. Most centres had a dedicated day surgery unit (87%). Preoperative assessment routines, when, how and by whom varied. Patient self-assessment questionnaires were common practice (87%). Upper age limit was uncommon (10%), lower age limit common (77%), and fixed high body mass index-limitation showed a mixed pattern, mean 40%. Postoperative nauseas and vomiting-risk stratification varied mean 46%. Anxiolytic premedication was uncommon. Administration of oral analgesics varied, mean 70%; paracetamol (94%), NSAIDs (80%) and opioid (28%). Preferred general anaesthesia technique varied considerable. Laryngeal mask airway was consistently used. Management of pain while in hospital was consistently performed. A majority centres provided take-home analgesics “tablet-package” (69%) or as prescription (80%). Strong opioids to be taken at home were given or prescribed by 59% of units. Written information about the postoperative care was common practice (90%), written instruction about management of pain was less frequently provided (69%). Most hospitals (93%) had standardised discharge criteria, including demand of an escort (75%) and not being alone first postoperative night (81%).ConclusionsWe found that regime for day surgical anaesthesia practice varied between as well as within countries. There is obvious room for further research on how to achieve safe and cost-effective logistics and practice for day case surgery

Rates of Sedimentation in the Central Arctic Ocean

The Arctic Ocean is presently undergoing geoscientific investigations of the type that occurred during the late 1940\u27s through 1960\u27s in the Atlantic, Indian and Pacific oceans. Seismic reflection and refraction data are scarce in the Arctic Ocean and large areas are virtually unsampled with respect to piston or gravity coring. The vast majority of available cores are less than10 m in length and largely lack biostratigraphically useful calcareous and siliceous microfossils. No drill cores exist from the ridges or deep basins in the central Arctic Ocean. Considering the limited geophysical and geological data available, it is not surprising that current concepts about Arctic Ocean sedimentation rates are diverging. The main point of difference is whether or not strongly subdued rates of sedimentation persisted in the central Arctic Ocean during Plio-Pleistocene times. The low sedimentation rate scenario is based on age models suggesting Plio-Pleistocene rates that vary between about 0.04 and 0.4 cm/ka. This scenario is chiefly derived from cores raised from ridges in the Amerasian Basin and implies that the majority of cores presently available extend well into, or encompass the entire, Pliocene. The contrasting high sedimentation rate scenario is based on age models suggesting rates that vary from about one to a few cm/ka, derived from cores from ridges and basins in both the Amerasian and Eurasian parts of the central Arctic Ocean. The latter scenario implies that most short cores rarely extend beyond the Pleistocene. Early paleomagnetic chronologies of sediment cores retrieved from the Amerasian Basin were based on the assumption that zones with negative inclination represented genuine polarity reversals. The first encountered down-core zone with negative inclination was interpreted to be the Brunhes/Matuyama boundary. This approach yielded mm-scale Plio-Pleistocene sedimentation rates. Biostratigraphy, cyclostratigraphy, and OSL dating, subsequently have indicated that many of these negative inclination changes represent Brunhes geomagnetic excursions, thus providing cm-scale Pleistocene sedimentation rates. All longer-term, Cretaceouos through Cenozoic, sedimentation rates derived from seismic reflection and tectonic models of bedrock age are on the order of cm/ka