Skeletal light-scattering accelerates bleaching response in reef-building corals.

BACKGROUND: At the forefront of ecosystems adversely affected by climate change, coral reefs are sensitive to anomalously high temperatures which disassociate (bleaching) photosynthetic symbionts (Symbiodinium) from coral hosts and cause increasingly frequent and severe mass mortality events. Susceptibility to bleaching and mortality is variable among corals, and is determined by unknown proportions of environmental history and the synergy of Symbiodinium- and coral-specific properties. Symbiodinium live within host tissues overlaying the coral skeleton, which increases light availability through multiple light-scattering, forming one of the most efficient biological collectors of solar radiation. Light-transport in the upper ~200 µm layer of corals skeletons (measured as 'microscopic' reduced-scattering coefficient, µ'(S,m)), has been identified as a determinant of excess light increase during bleaching and is therefore a potential determinant of the differential rate and severity of bleaching response among coral species. RESULTS: Here we experimentally demonstrate (in ten coral species) that, under thermal stress alone or combined thermal and light stress, low-µ'(S,m) corals bleach at higher rate and severity than high-µ'(S,m) corals and the Symbiodinium associated with low-µ'(S,m) corals experience twice the decrease in photochemical efficiency. We further modelled the light absorbed by Symbiodinium due to skeletal-scattering and show that the estimated skeleton-dependent light absorbed by Symbiodinium (per unit of photosynthetic pigment) and the temporal rate of increase in absorbed light during bleaching are several fold higher in low-µ'(S,m) corals. CONCLUSIONS: While symbionts associated with low-[Formula: see text] corals receive less total light from the skeleton, they experience a higher rate of light increase once bleaching is initiated and absorbing bodies are lost; further precipitating the bleaching response. Because microscopic skeletal light-scattering is a robust predictor of light-dependent bleaching among the corals assessed here, this work establishes µ'(S,m) as one of the key determinants of differential bleaching response.

Rapid intraoperative localization of parathyroid glands utilizing methylene blue infusion.

OBJECTIVE: To review a single surgeon's experience utilizing an intraoperative methylene blue infusion (IMBI) to identify parathyroid glands during neck exploration for primary hyperparathyroidism. STUDY DESIGN AND SETTING: Retrospective review of 35 patients who underwent bilateral neck exploration utilizing an IMBI at a dose of 7.5 mg/kg following the induction of general anesthesia. RESULTS: All patients reverted to normocalcemia with a mean follow-up of 17 months. IMBI facilitated the identification of abnormal parathyroid tissue in 34/35 patients (97%). A dark blue-purple staining was observed in 33/37 stained adenomas (89%). Four adenomas and four hyperplastic glands stained a lighter shade of blue-green. Among 89 normal glands, 41(46%) stained a pale green-grey color. CONCLUSIONS: IMBI is a safe, readily available, cost-effective, and underutilized technique that facilitates rapid identification of parathyroid adenomas, helps distinguish normal glands from hyperplastic glands, and helps to locate ectopic glands. An overall reduction in operative time, especially for bilateral neck exploration, can be anticipated.

Painful paresthesiae are infrequent during brachial plexus localization using low-current peripheral nerve stimulation.

BACKGROUND: Considerable controversy exists over the relationship of paresthesia to nerve stimulation. The purpose of this study was to determine the frequency with which patients report paresthesia at the point that an acceptable motor response is obtained to low-intensity current electrical stimulation. METHODS: Low-intensity current nerve stimulation (0.6 mA, 200 microseconds, 2 Hz) was used to identify the brachial plexus in 64 consecutive patients having shoulder or arm surgery with an interscalene block. During nerve localization and while maintaining a motor response (0.20 mA-0.40 mA), the patients were queried regarding any radiating sensation or pain (paresthesia) in the shoulder or extremity on the side of the blockade. Sensory distribution of the block, motor strength of the arm muscles, and adequacy of anesthesia were used to assess the extent of blockade. RESULTS: Ninety-five percent of patients had satisfactory surgical anesthesia. None of the patients spontaneously reported having a paresthesia during nerve stimulation. However, on careful questioning, half of the patients (55%) reported electrical paresthesia, defined as dull tingling sensation traveling down to their hands and coinciding with the motor response. In addition, most patients (71%) spontaneously reported having a mild, radiating paresthesia on initial injection of local anesthetic. CONCLUSIONS: Painful paresthesiae should be infrequent when a low-stimulating current is used to identify the neural components of the brachial plexus and when the block needle is advanced slowly. Low-current intensity nerve stimulation can be used to achieve successful interscalene block with minimal discomfort to the patient.

Severe bradycardia during spinal and epidural anesthesia recorded by an anesthesia information management system.

BACKGROUND: Bradycardia and asystole can occur unexpectedly during neuraxial anesthesia. Risk factors may include low baseline heart rate, first-degree heart block, American Society of Anesthesiologists physical status 1, beta-blockers, male gender, and high sensory level. Anesthesia information management systems automatically record large numbers of physiologic variables that are combined with data input from the anesthesiologist to form the anesthesia record. Such large databases can be scanned for episodes of bradycardia. METHODS: To select spinal and epidural anesthetics that did not also involve general anesthesia, 57,240 automated anesthesia records were scanned. Obstetrical patients and patients younger than age 12 yr were excluded. The electronic records selected were then scanned for episodes of moderate (heart rate < 50 and >/= 40 beats/min) or severe (heart rate < 40 beats/min) bradycardia. RESULTS: A total of 6,663 cases (11.6%) met the inclusion criteria. Among the 677 cases of bradycardia (10.2%) were 46 cases of severe bradycardia (0.7%). In the final multivariate logistic regression analysis, baseline heart rate less than 60 beats/min (P