Regional cerebrovascular reactivity to carbon dioxide during cardiopulmonary bypass in patients with cerebrovascular disease

In patients with cerebrovascular disease, hypercarbia may cause redistribution of regional cerebral blood flow from marginally perfused to well-perfused regions (intracerebral steal), as evidenced by regional cerebral blood flow studies during carotid endarterectomy. During hypothermic cardiopulmonary bypass, the pH-stat method of acid-base management produces relative hypercarbia. To determine whether pH-stat management produces relative hypercarbia. To determine whether pH-stat management induces intracerebral steals, we investigated nine patients with cerebrovascular disease undergoing coronary artery bypass grafting. During hypothermic cardiopulmonary bypass, arterial carbon dioxide tension was varied in random order between 40 mm Hg and 60 mm Hg (uncorrected for body temperature). Regional cerebral blood flow was measured by clearance of 133 xenon injected into the arterial inflow cannula. Nasopharyngeal temperature (26.8 degrees-28.0 degrees +/- 2.2 degrees-3.0 degrees C), perfusion flow rate (2.14-2.18 +/- 0.70-0.73 L/min/m2), mean arterial pressure (67-68 +/- 6-9 mm Hg), arterial carbon dioxide tension (302-308 +/- 109-113 mm Hg), and hematocrit (23% +/- 4%) were maintained within narrow limits in each patient during arterial carbon dioxide tension manipulation. Global mean cerebral blood flow values were similar to previously reported values in patients free of cerebrovascular disease; patients in this study averaged 15.2 +/- 2.5 ml/100 gm/min at an arterial carbon dioxide tension of 46.1 +/- 8.4 mm Hg and 25.3 +/- 6.1 ml/100 gm/min at an arterial carbon dioxide tension of 71.1 +/- 11.8 mm Hg. Carbon dioxide reactivity, defined as mean global cerebral blood flow (in ml/100 gm/min) divided by arterial carbon dioxide tension (in mm Hg), was similar in the region having the lowest regional cerebral blood flow and in the brain as a whole. No patient developed evidence of an intracerebral steal at the higher arterial carbon dioxide tension. During hypothermic cardiopulmonary bypass, higher levels of arterial carbon dioxide tension, such as those associated with the pH-stat management technique, are apparently not associated with potentially harmful redistribution of cerebral blood flow in patients with cerebrovascular disease.     

Morphologic characterization of osteoblast-like cell cultures isolated from newborn rat calvaria

Summary Two methods for harvesting osteoblast-like cell populations from newborn (10 days) rat calvaria were compared. The first one consisted in culturing the periosteum-free bones and then trypsinizing the cells on the bone surface. The second one involved the migration of the osteoblasts on glass fragments before trypsinization. Since the plating efficiency, the proportion of alkaline phosphatase-positive cells, the population doubling time, and the calcium deposition were more adequate, the second method was used to further characterize the behavior of the cultures. During the first week of culture, the cells featured shapes similar to those observedin vivo on the surface of periosteum-free calvaria. They formed multilayers and, in the presence of ascorbic acid, synthetized an organic matrix containing exclusively type I collagen. Later, small amounts of type III collagen appeared. The cells were embedded in the matrix and progressively acquired the morphologic phenotype of osteocyte-like cells. The matrix mineralized in the presence of β-glycerophosphate. The technique of dropinoculation (high concentration of cells in a small volume of medium) promoted the multilayer formation and the achievement of large mineralized plates (about 1 cm²) in 3 weeks of culture.     

Transcanal cochlear implantation under monitored anesthesia care.

OBJECTIVE: Given the associated risk of general anesthesia in elderly patients with cardiovascular disease, the authors set out to determine the feasibility of transcanal cochlear implantation under local anesthesia with monitored anesthesia care. METHODS: A 70-year-old man with a history of coronary artery bypass grafting, diabetes mellitus, and an American Society of Anesthesiologists Class III cardiac status underwent cochlear implantation under local with monitored anesthesia care. RESULT: With the described technique and regimen of intravenous remifentanil and dexmedetomidine, the patient tolerated the 60-minute procedure without tachycardia, hyper- or hypotension, or cardiac ischemia. CONCLUSION: Cochlear implantation using the pericanal electrode technique performed under local anesthesia with monitored anesthesia care is possible in patients at risk for undergoing general anesthesia for cochlear implantation.     

Nefopam, a Nonsedative Benzoxazocine Analgesic, Selectively Reduces the Shivering Threshold in Unanesthetized Subjects

Background: The analgesic nefopam does not compromise ventilation, is minimally sedating, and is effective as a treatment for postoperative shivering. The authors evaluated the effects of nefopam on the major thermoregulatory responses in humans: sweating, vasoconstriction, and shivering.

Methods: Nine volunteers were studied on three randomly assigned days: (1) control (saline), (2) nefopam at a target plasma concentration of 35 ng/ml (low dose), and (3) nefopam at a target concentration of 70 ng/ml (high dose, approximately 20 mg total). Each day, skin and core temperatures were increased to provoke sweating and then reduced to elicit peripheral vasoconstriction and shivering. The authors determined the thresholds (triggering core temperature at a designated skin temperature of 34[degrees]C) by mathematically compensating for changes in skin temperature using the established linear cutaneous contributions to control of each response.

Results: Nefopam did not significantly modify the slopes for sweating (0.0 +/- 4.9[degrees]C [middle dot] [mu]g-1 [middle dot] ml; r2 = 0.73 +/- 0.32) or vasoconstriction (-3.6 +/- 5.0[degrees]C [middle dot] [mu]g-1 [middle dot] ml; r2 = -0.47 +/- 0.41). In contrast, nefopam significantly reduced the slope of shivering (-16.8 +/- 9.3[degrees]C [middle dot] [mu]g-1 [middle dot] ml; r2 = 0.92 +/- 0.06). Therefore, high-dose nefopam reduced the shivering threshold by 0.9 +/- 0.4[degrees]C (P < 0.001) without any discernible effect on the sweating or vasoconstriction thresholds.     

Teaching with a Video System Improves the Training Period but Not Subsequent Success of Tracheal Intubation with the Bullard Laryngoscope

Background: The Bullard laryngoscope is useful for the management of a variety of airway management scenarios. Without the aid of a video system, teaching laryngoscopy skills occurs with indirect feedback to the instructor. The purpose of this study was to determine if use of a video system would quicken the process of learning the Bullard laryngoscope or improve the performance (speed or success) of its use.

Methods: Thirty-six anesthesia providers with no previous Bullard laryngoscope experience were randomly divided into two groups: initial training (first 15 intubations) with looking directly through the eyepiece (n = 20), or with the display of the scope on a video monitor (n = 16). The subjects each then performed 15 Bullard intubations by looking directly through the eyepiece.

Results: There was not an overall significant difference in laryngoscopy or intubation times between the groups. When only the first 15 intubations were considered, the laryngoscopy time was shorter in the video group (26 +/- 24) than in the nonvideo group (32 +/- 34;P < 0.04). In the first 15 patients, there were fewer single attempts at intubation (67.9%vs. 80.3%;P < 0.002) and more failed intubations (17.2%vs. 6.0%;P < 0.0001) in the nonvideo group.     

Inhibitors of urinary stone formation in 40 recurrent stone formers

The excretion of four inhibitors of urinary stone formation (zinc, magnesium, citrates and glycosaminoglycans (GAG) was studied in 20 normal controls and 40 recurrent calcium stone formers who were placed on a fixed diet restricted in calcium, oxalates and purines. We were unable to show any abnormality in the excretion of Zn, Mg or GAG. In 11 patients, a low level of urinary citrate was a significant feature that was associated in most cases with a urinary pH value above 6. Citrate concentration (per litre) and output (per 24 h) were found to be lower than in the controls in 19 and 33% respectively of the determinations. The overall ratio of average urinary citrate concentration in patients and controls was 0.56, a figure in agreement with previous data.     

Functional and structural characteristics of the glycosaminoglycans of the bladder luminal surface

The glycosaminoglycan layer of bladder has been proposed to play a crucial role in protecting the bladder from harmful substances in urine. Rats were partially cystectomized to determine whether bladder glycosaminoglycans are routinely eluted from the bladder surface in detectable quantities. Cystectomy produced no detectable qualitative or quantitative changes in excreted GAG thereby showing that most urinary glycosaminoglycan originates in the kidney and not from the bladder. Damaging the glycosaminoglycan layer by a dilute acid wash, however, leads to a consistent decrease in the output of urinary GAG which recovers to normal at the same rate as the layer regenerates. This suggests that the newly exposed sites tightly bind urinary GAG. We suggest that such binding may be a component of the normal physiological defense mechanism of the bladder. The bladder glycosaminoglycan layer was isolated, dilute acid being used to elute ionically-bound material and brief trypsinization to elute intercalated proteoglycans from the luminal surface. The GAG from the luminal surface, which was present at a density of one chain per 50 nm.2 of bladder surface, was quite different in composition from that isolated from the whole bladder.     

Deaths of heroin users in a general practice population

Recent evidence suggests that heroin users in the UK are 16 times more likely to die than otherwise expected, although causes of death are varied. The present investigation examines deaths of heroin users at a large Scottish general practice over a four-year period prior to 1 July 1985. A mortality rate of 9.72 per 1000 heroin-user patients per year was observed, roughly half that previously reported, although this difference did not prove to be statistically significant. A higher proportion of the observed deaths were attributed to heroin, and fewer to the misuse of other drugs, and it is speculated that this may reflect the practice's policy of not prescribing opiates to heroin users. Factors associated with heroin-user deaths are examined and areas identified where general practitioners may help to avert some of these deaths.     

Does the extent of lymph node dissection influence outcome in patients with stage I non-small-cell lung cancer?

OBJECTIVE: To assess the therapeutic effect of the extent of lymph node dissection performed in patients with a stage pI non-small-cell lung cancer (NSCLC). METHODS: We analysed data on 465 patients with stage I NSCLC who were treated with surgical resection and some form of lymph node sampling. The median number of lymph node sampled was 10 and the median number of ipsilateral mediastinal lymph node stations sampled was two. We chose to define a procedure that harvested 10 or more lymph nodes and sampled two or more ipsilateral mediastinal stations as a lymphadenectomy, by contrast with sampling when one or both criteria were not satisfied. The effect of the surgical techniques: lymph node sampling (LS; n=207) vs. lymphadenectomy (LA; n=258) on 30-day mortality and overall survival were investigated. RESULTS: A total of 6244 lymph nodes was examined, including 4306 mediastinal lymph nodes. The mean (+/-SD) numbers of removed lymph nodes were 7+/-6.1 per patient following LS vs.18.6+/-9.3 following LA (P=0.001). An average mean of 1+/-0.90 mediastinal lymph node station per patient was sampled following LS vs. 2.7+/-0.8 following LA (P<10(-6)). Overall 30-day mortality rates were 2.4 and 3.1%, respectively. LA was disclosed as a favourable prognosticator at multivariate analysis (Hazard Risk: 1.43; 95% Confidence Interval: 1.00-2.04; P=0.048), together with younger patient age, absence of blood vessels invasion, and smaller tumour size. CONCLUSIONS: Importance of lymph node dissection affects patients outcome, while it does not enhance the operative mortality. A minimum of 10 lymph nodes assessed, and two mediastinal stations sampled are suggested as possible pragmatic markers of the quality of lymphadenectomy.