Preparation and anesthetic properties of propofol microemulsions in rats

BACKGROUND: The lipophilicity of propofol has required dispersion in a soybean macroemulsion. The authors hypothesized that the anesthetic properties of propofol are preserved when reformulated as a transparent microemulsion rather than as a turbid macroemulsion and that the dose-response relation can be selectively modified by altering the microemulsion's surfactant type and concentration. METHODS: Microemulsions of propofol were formulated using purified poloxamer 188 (3%, 5%, 7%), and sodium salt of fatty acids (C(8), C(10), C(12)) in saline and characterized using ternary/binary diagrams, particle sizing, and stability upon dilution. Rats received propofol (10 mg . kg(-1) . min(-1)) as either a microemulsion or a conventional macroemulsion to determine these end points: induction (dose; stunned; loss of lash reflex, righting reflex, withdrawal to toe pinch) and recovery (recovery of lash, righting, withdrawal reflexes). After a 14-day recovery period, rats were crossed over into the opposite experimental limb. RESULTS: Forty-eight microemulsions (diameter, 11.9-47.7 nm) were formulated. Longer carbon chain length led to a marked increase in the volume of diluent necessary to break these microemulsions. All rats experienced anesthetic induction with successful recovery, although significantly greater doses of propofol were required to induce anesthesia with microemulsions irrespective of surfactant concentration or type than with macroemulsions. The sodium salt of C10 fatty acid microemulsion required the greatest dose and longest time for anesthetic induction. CONCLUSION: Propofol microemulsions cause induction in rats similar to that from macroemulsions. The surfactant concentration and type markedly affect the spontaneous destabilization and anesthetic properties of microemulsions, a phenomenon suggesting a mechanism whereby dose-response relation can be selectively modified.     

Subjective assessment and cardiovascular response to ischemic pain in young, healthy women users and non-users of oral contraceptives

Experimental pain was introduced in women volunteers, some of whom were taking oral contraceptives. Pain perception and tolerance were the same, regardless of oral contraceptive use. All responded to the introduction of pain with increasing heart rate (HR), blood pressure (BP) and the product of systolic pressure, HR and the left ventricular ejection time (LVET). The users had a more consistent response pattern, and their reported levels of pain were positively and highly correlated with the changes in pre-ejection period (PEP) and the ratio PEP/LVET. Non-users had more variable systolic time interval (STI) responses.     

How ominous is an abnormal scan in bronchogenic carcinoma?

Bone, brain, and liver radioisotope scans as prognostic indicators were studied in a series of 162 patients with primary bronchogenic carcinoma. One or more scans positive for metastasis reliably predicted death in less than six months. An abnormal bone scan was most significant (P less than .001). Reliability in predicting less than one year's survival in abnormal liver and brain scans was P less than .05 for both. Patients with two normal scans were found to have a 50% six-month survival expectation. Brain scans added little information, as they would have predicted a different prognosis for only three of 114 patients who received them.     

Is ECG monitoring in the operating room cost effective?

ECG monitoring during anesthesia detects many arrhythmias, even in healthy patients. The clinical significance of these arrhythmias is uncertain. However, a conservative analysis of the cost of ECG monitoring in the USA reveals that the prevention of cardiac arrests occurring in 1 of 3,500 cases is quite cost effective. Routine ECG monitoring for all anesthetics in the USA is recommended.     

Do Vaccination Strategies Implemented by Nursing Homes Narrow the Racial Gap in Receipt of Influenza Vaccination in the United States?

OBJECTIVES: To determine whether the racial inequity between African Americans and Caucasians in receipt of influenza vaccine is narrower in residents of nursing homes with facility‐wide vaccination strategies than in residents of facilities without vaccination strategies. DESIGN: Secondary data analysis using the National Nursing Home Survey 2004, a nationally representative survey. SETTING: One thousand one hundred seventy‐four participating nursing homes sampled systematically with probability proportional to bed size. PARTICIPANTS: Thirteen thousand five hundred seven randomly sampled residents of nursing homes between August and December 2004. MEASUREMENTS: Receipt of influenza vaccine within the last year. Logistic regression was used to examine the relationship between facility‐level influenza immunization strategy and racial inequity in receipt of vaccination, adjusted for characteristics at the resident, facility, state, and regional levels. RESULTS: Overall in the Untied States, vaccination coverage was higher for Caucasian and African‐American residents; the racial vaccination gaps were smaller (<6 percentage points) and nonsignificant in residents of homes with standing orders for influenza vaccinations (P=.14), verbal consent allowed for vaccinations(P=.39), and routine review of facility‐wide vaccination rates (P=.61) than for residents of homes without these strategies. The racial vaccination gap in residents of homes without these strategies were two to three times as high (P=.009, P=.002, and P=.002, respectively). CONCLUSION: The presence of several immunization strategies in nursing homes is associated with higher vaccination coverage for Caucasian and African‐American residents, narrowing the national vaccination racial gap.     

Temperature-related differences in mean expired pump and arterial carbon dioxide in patients undergoing cardiopulmonary bypass

OBJECTIVE: To investigate the relationship between arterial carbon dioxide (PaCO(2)) and mean expired pump CO(2) during cardiopulmonary bypass (PeCPBCO(2)) in patients undergoing cardiac surgery with CPB during steady state, cooling, and rewarming phases of CPB. DESIGN: Consenting patients, prospective study. SETTING: University-affiliated hospital. PARTICIPANTS: Twenty-nine patients. INTERVENTIONS: Patients aged 22 to 81 years were enrolled. An alpha-stat acid-base regimen was performed during CPB. The PeCPBCO(2) was measured by an infrared multigas analyzer with the sampling line connected to the scavenging port of the oxygenator. Values for PaCPBCO(2) from the arterial outflow to the patient and PeCPBCO(2) during CPB at various oxygenator arterial temperatures were collected and compared. Data were analyzed by analysis of variance with 1-way repeated measures and post hoc pair-wise Tukey testing when appropriate. The differences between PaCPBCO(2) and PeCPBCO(2) were linearly regressed against temperature. A p value <0.05 was considered significant. MEASUREMENTS AND MAIN RESULTS: Three to 5 data sets during CPB were collected from each patient. The mean gradient between PaCPBCO(2) and PeCPBCO(2) was positive 12.4 +/- 10.0 mmHg during the cooling phase and negative 9.3 +/- 9.9 mmHg during the rewarming phase, respectively. On regression of the data, the difference between PaCPBCO(2) and PeCPBCO(2) shows a good correlation with the change in temperature (r(2) = 0.79). The arterial CO(2) +/- x mmHg can be predicted by the formula PaCPBCO(2) = (-2.17x + 69.2) + PeCPBCO(2), where x is temperature in degrees C. CONCLUSIONS: Monitoring the mean expired CO(2) value from the CPB oxygenator exhaust scavenging port with a capnography monitor provides a continuous and noninvasive data source to aid in sweep flow CPB circuit management during CPB.