Changes in tissue oxygen tension, venous saturation, and Fick-based assessments of cardiac output during hyperoxia.

BACKGROUND: Hyperoxemia (arterial oxygen tension >100 mm Hg) may occur in critically ill patients and have effects on mixed venous saturation (SvO2 ) and on Fick-based estimates of cardiac output (CO). We investigated the effect of hyperoxemia on SvO2 and on assessments of CO using the Fick equation. METHODS: Yorkshire swine (n = 14) were anesthetized, intubated, and paralyzed for instrumentation. SvO2 (co-oximetry) and tissue oxygen tension (tPO2 , implantable electrodes) in brain and myocardium were measured during systematic manipulation of arterial oxygen tension (PaO2 ) using graded hyperoxia (fraction of inspired oxygen 0.21 → 0.8). Secondarily, oxygen- and carbon dioxide-based estimates of CO (FickO2 and FickCO2 , respectively) were compared with measurements from a flow probe placed on the aortic root. RESULTS: Independent of changes in measured oxygen delivery, cerebral and myocardial tPO2 increased in proportion to PaO2 , as did SvO2 (P < 0.001 for all). Based on mixed model analysis, each 100 mm Hg increase in PaO2 resulted in a 4.8 ± 0.9% increase in SvO2 under the conditions tested. Because neither measured oxygen consumption, arterial oxyhemoglobin saturation or cardiac output varied significantly during hyperoxia, changes in SvO2 resulted in successively increasing errors in FickO2 during hyperoxia (34% during normoxia, 72% during FiO2 0.8). FickCO2 lacked the progressively worsening errors present in FickO2 , but correlated poorly with CO. CONCLUSION: SvO2 acutely changes following changes in PaO2 even absent changes in measured DO2 . This may lead to errors in FickO2 estimates of CI. Further work is necessary to understand the impact of this phenomenon in disease states.

Oxygen delivery using engineered microparticles.

A continuous supply of oxygen to tissues is vital to life and interruptions in its delivery are poorly tolerated. The treatment of low-blood oxygen tensions requires restoration of functional airways and lungs. Unfortunately, severe oxygen deprivation carries a high mortality rate and can make otherwise-survivable illnesses unsurvivable. Thus, an effective and rapid treatment for hypoxemia would be revolutionary. The i.v. injection of oxygen bubbles has recently emerged as a potential strategy to rapidly raise arterial oxygen tensions. In this report, we describe the fabrication of a polymer-based intravascular oxygen delivery agent. Polymer hollow microparticles (PHMs) are thin-walled, hollow polymer microcapsules with tunable nanoporous shells. We show that PHMs are easily charged with oxygen gas and that they release their oxygen payload only when exposed to desaturated blood. We demonstrate that oxygen release from PHMs is diffusion-controlled, that they deliver approximately five times more oxygen gas than human red blood cells (per gram), and that they are safe and effective when injected in vivo. Finally, we show that PHMs can be stored at room temperature under dry ambient conditions for at least 2 mo without any effect on particle size distribution or gas carrying capacity.

Perioperatively Inhaled Hydrogen Gas Diminishes Neurologic Injury Following Experimental Circulatory Arrest in Swine.

This study used a swine model of mildly hypothermic prolonged circulatory arrest and found that the addition of 2.4% inhaled hydrogen gas to inspiratory gases during and after the ischemic insult significantly decreased neurologic and renal injury compared with controls. With proper precautions, inhalational hydrogen may be administered safely through conventional ventilators and may represent a complementary therapy that can be easily incorporated into current workflows. In the future, inhaled hydrogen may diminish the sequelae of ischemia that occurs in congenital heart surgery, cardiac arrest, extracorporeal life-support events, acute myocardial infarction, stroke, and organ transplantation.

Responsive monitoring of mitochondrial redox states in heart muscle predicts impending cardiac arrest.

Assessing the adequacy of oxygen delivery to tissues is vital, particularly in the fields of intensive care medicine and surgery. As oxygen delivery to a cell becomes deficient, changes in mitochondrial redox state precede changes in cellular function. We describe a technique for the continuous monitoring of the mitochondrial redox state on the epicardial surface using resonance Raman spectroscopy. We quantify the reduced fraction of specific electron transport chain cytochromes, a metric we name the resonance Raman reduced mitochondrial ratio (3RMR). As oxygen deficiency worsens, heme moieties within the electron transport chain become progressively more reduced, leading to an increase in 3RMR. Myocardial 3RMR increased from baseline values of 18.1 ± 5.9 to 44.0 ± 16.9% (P = 0.0039) after inferior vena cava occlusion in rodents (n = 8). To demonstrate the diagnostic power of this measurement, 3RMR was continuously measured in rodents (n = 31) ventilated with 5 to 8% inspired oxygen for 30 min. A 3RMR value exceeding 40% at 10 min predicted subsequent cardiac arrest with 95% sensitivity and 100% specificity [area under the curve (AUC), 0.98], outperforming all current measures, including contractility (AUC, 0.51) and ejection fraction (AUC, 0.39). 3RMR correlated with indices of intracellular redox state and energy production. This technique may permit the real-time identification of critical defects in organ-specific oxygen delivery.

A competency matrix for global oral health.

The Lancet Commission on Education of Health Professionals for the 21(st) Century calls for enhancing health education for the needs and challenges of the 21st century to improve health status globally. To complement the Lancet report, this article makes recommendations for including core global health competencies in the education of health care professionals and specific groups of the public who are relevant to oral health in a global context in order to tackle the burden of oral diseases. Experts from various professional backgrounds developed global oral health competencies for four target groups: Group 1 was defined as dental students, residents/trainee specialists (or equivalent), and dentists; Group 2 was community health workers, dental hygienists, and dental therapists (or the equivalent); Group 3 was health professionals such as physicians, physician assistants, nurses, nurse practitioners, and pharmacists; and Group 4 was non-health professionals in the public arena such as parents, teachers, decision makers, key opinion leaders, and health and consumer advocates. Key competencies for members of each of the four target groups are presented in a matrix. The suggested competency matrix shows that many other health professions and groups in society have potentially crucial roles in the prevention, control, and management of oral diseases globally. Workforce models including a wider range of professionals working together as a team will be needed to tackle the burden of oral diseases in an integrated way in the broader context of non-communicable diseases. Further discussion and research should be conducted to validate or improve the competencies proposed here with regard to their relevance, appropriateness, and completeness.

Computer-controlled delivery versus syringe delivery of local anesthetic injections for therapeutic scaling and root planing.

BACKGROUND: The authors conducted a study to compare administration of local anesthetic using a computer-controlled delivery device with an aspirating syringe for therapeutic scaling and root planing. The anterior middle superior alveolar, or AMSA, injection was compared with other maxillary injections. METHODS: Twenty healthy adults with moderate periodontal disease participated in this single-blind crossover study. Subjects were evaluated by a trained examiner and were treated by experienced dental hygienists. Subjects provided written and verbal pain ratings via a visual analog scale, or VAS, and a verbal rating scale, or VRS. AMSA injections were compared with syringe-delivered injections--greater palatine, or GP, and nasopalatine, or NP, blocks, and anterior superior alveolar and middle superior alveolar injections--in maxillary quadrants. Bleeding and changes in attachment were evaluated after one month. RESULTS: VAS and VRS scores for AMSA were significantly lower for computer-controlled delivery when compared with NP injections and combined maxillary injections (VAS scores) and with GP and combined maxillary injections (VRS scores). Mean injection times were similar for both groups. Mean gains in attachment were equal, 0.19 millimeters for quadrants anesthetized using computer-controlled injections and 0.22 mm for syringe injections. CONCLUSIONS: Subjects reported having less pain with GP and NP injections delivered using the computer-controlled device, and total injection time was similar to that required for syringe injections. Both techniques provided adequate anesthesia for therapeutic scaling and root planing. Clinical Implications. The two anesthetic delivery techniques were therapeutically equivalent for mandibular injections, and the AMSA injection has clinically significant advantages for maxillary injections.

New curriculum in dentistry for Tanzania: competency-based education for patient and population health (2008-2011).

From 2008 to 2011, the School of Dentistry at Muhimbili University of Health and Allied Sciences in Tanzania revised and then initiated implementation of a curriculum to improve the educational process for, and competence of, its graduates. As an increasing body of research demonstrates the detrimental effects of oral diseases on health and the interrelationships between oral and systemic diseases (including HIV and diabetes), the importance of dentistry education grows. We describe the population oral health problems in Tanzania, the need to enhance the dental workforce, and the process of curricular reform to meet these needs. This reform included transition to a competency-based curriculum featuring teaching methods that will enhance the effectiveness of the education and performance of graduates in traditional and new roles. We conclude with lessons for Tanzania and for health professions educational institutions elsewhere, as well as for public health-care planners concerned about linking health professions education to improving population health in resource-poor countries.

Effectiveness of a transmucosal lidocaine delivery system for local anaesthesia during scaling and root planing.

OBJECTIVE: This study compared the efficacy of transmucosal anaesthetic patches containing lidocaine (46.1 mg/2 cm(2)) to placebo for local anaesthesia during quadrant scaling and root planing using periodontal clinical indices and patient perception of pain. MATERIAL AND METHODS: Forty healthy adults with moderate periodontal disease and moderate subgingival calculus were scaled at weekly intervals, two quadrants randomized to treatment patches and two quadrants randomized to placebo patches. Bleeding, probing depths and attachment levels were evaluated prior to treatment and 1 month after quadrant scaling was completed. Subjects completed 100 mm visual analogue pain scales 15 min. after patch placement and at the end of treatment, and were asked for verbal assessment of perceived pain. RESULTS: Subjects' verbal ratings demonstrated consistently greater pain relief with active patches than placebo (p<0.0001). Visual analogue scales demonstrated significantly greater pain relief with the treatment patches after 15 min. (p=0.0003) and at the end of treatment (p=0.0149). Efficacy of periodontal therapy was equivalent for treatment and control groups. No adverse events were observed; localized minimal gingival irritation was noted in three subjects. CONCLUSION: Transmucosal lidocaine patches provided sufficient anaesthesia for therapeutic quadrant scaling and root planing procedures.