Carbon monoxide exposure from cooking in snow caves at high altitude.

OBJECTIVE: To determine the physiological consequences of acute CO exposure from cooking in snow caves at 3,200 m. We hypothesized that ambient CO and serum carboxyhemoglobin (COHb) levels would increase and that even low levels of COHb would be associated with symptoms of CO poisoning at high altitude. METHOD: This was a prospective observational study. Twenty-two healthy volunteers age 18 years or older were recruited during a winter camping trip at 3,200 m. Subjects filled out symptom questionnaires, and heart rate (HR), oxygen saturation (SaO2), serum COHb, and ambient CO were all measured before and after cooking inside snow caves. RESULTS: Median age of subjects was 32 years, and 87% were male. The median ambient CO level increased by 17 ppm (IQR, 2-27 ppm), P = .005. Mean serum COHb level rose from 0.3% (IQR, 0.2%-0.4%) to 1.2% (IQR, 0.7%-2.6%) after cooking, for a difference of 1% (IQR, 0.4%-2.3%), P < .001. There were no differences in symptom scores before and after cooking, and there was no significant effect on HR or SaO2. CONCLUSION: A single exposure to CO at 3,200 m increases ambient CO and COHb but not to clinically important levels. Further studies are needed to examine the risks of longer exposures at higher altitudes.

Chronic hypoxia diminishes pregnancy-associated DNA synthesis in guinea pig uteroplacental arteries.

Enlargement of the uterine artery (UA) during pregnancy is diminished in women residing at a high altitude. We asked whether chronic hypoxia alters the rise in DNA synthesis in uteroplacental vessels and, if so, whether the reduction is related to the intrauterine growth retardation (IUGR) observed under conditions of chronic hypoxia. We used bromodeoxyuridine (BrdU) labelling to measure DNA synthesis in all vascular layers of the UA, mesometrial arteries (MA), thoracic aorta and mesenteric artery of guinea pigs, residing throughout pregnancy at a low (1600 m) or high (3962 m) altitude. Pregnancy increased DNA synthesis throughout the UA at both altitudes, yet the maximal value was less at high than low altitude (P<0.05). Likewise, pregnancy increased DNA synthesis throughout the MA, yet at high altitude pregnancy elevated levels returned to non-pregnant values after 42 days of gestation, whereas at low altitude DNA synthesis continued to be elevated until near term. Fetal weights were lower (P=0.01) and placental/fetal weight ratios tended to be greater in high than low altitude, near term pups (P = 0.09). We conclude that a diminished growt response by the uteroplacental vasculature to pregnancy may contribute to the previously reported reduced uterine artery blood flow and resulting IUGR at high altitude.

Ultrasound-guided brachial and basilic vein cannulation in emergency department patients with difficult intravenous access.

STUDY OBJECTIVE: Emergency department patients who require intravenous access but lack peripheral intravenous sites frequently require central line placement. Blind percutaneous brachial vein cannulation has been proposed as an alternative in these patients but is associated with high failure and complication rates. We evaluated an ultrasound-guided approach to percutaneous deep brachial vein or basilic vein cannulation in ED patients with difficult intravenous access. METHODS: We prospectively enrolled ED patients who required intravenous access in whom there had been 2 unsuccessful attempts at establishing a peripheral intravenous line. Using a 7.5-MHz ultrasound probe, the deep brachial vein or basilic vein was identified and then cannulated with a 2-in, 18- to 20-gauge intravenous catheter. Time from probe placement to cannulation, number of attempts, and complications were recorded. RESULTS: One hundred one patients were enrolled, of whom 50 were injection drug users and 21 were obese. Cannulation was successful in 91 patients (91%) and accomplished on the first attempt in 73 (73%). The mean (+/-SD) time required for cannulation was 77 seconds (+/-129, range 4 to 600 seconds). The line infiltrated or fell out within 1 hour of cannulation in 8 (8%) patients. One patient reported severe pain. There were 2 (2%) cases of brachial artery puncture. CONCLUSION: Ultrasound-guided brachial and basilic vein cannulation is safe, rapid, and has a high success rate in ED patients with difficult peripheral intravenous access.

Mycobacterium malmoense infections in the United States, January 1993 through June 1995.

Mycobacterium malmoense is a nontuberculous mycobacterium rarely encountered in the United States. However, isolations of M. malmoense from 73 patients (11 in 1992, 35 in 1993, and 27 in 1994) were reported to the Centers for Disease Control and Prevention. We contacted state mycobacteriology laboratories and health care providers of patients whose M. malmoense isolations were reported from January 1993 through June 1995. To assign disease status for these patients, we used the criteria of the American Thoracic Society. Of 60 evaluable patients with disease status, only six (10%) had disease due to M. malmoense (five adults with pulmonary disease and one child with cervical lymphadenitis). We conclude that the number of patients with disease due to M. malmoense remains low. Increased isolation of this species may be due to the increased use of more sensitive and specific laboratory methods. For surveillance purposes, multiple M. malmoense isolates and age of younger than 10 years appear to be the best predictors for M. malmoense disease.

Pregnancy stimulation of DNA synthesis and uterine blood flow in the guinea pig.

Pregnancy stimulates DNA synthesis in uterine artery smooth muscle cells. Unknown is whether DNA synthesis increases in all layers of the vessel wall in uterine or nonuterine vessels, the distribution and time course of the proliferative response in relation to the rise in uterine blood flow, and the extent to which a pregnancy-induced rise in DNA synthesis can be mimicked by chronic estradiol treatment. To measure DNA synthesis, we implanted bromodeoxyuridine (BrdU, 400 mg) s.c. for 14-d periods in three nonpregnant, nine pregnant, three vehicle, and five estradiol (2.5 mg/14 d)-treated guinea pigs. Uterine blood flow was measured in four nonpregnant and 18 pregnant animals using radiolabeled microspheres. Pregnancy stimulated DNA synthesis in the adventitia, media, and intima of the uterine artery, radial artery (the vessels deriving from the main uterine artery and entering the uterine wall), and uterine vein but not in the aorta or mesenteric artery. Maximal uterine artery medial area and labeling indices in all layers of the uterine artery, uterine vein, and the radial artery adventitia were attained by mid-pregnancy (d 28-42 of the guinea pig's 63-day gestation), whereas DNA synthesis increased progressively until term in the radial artery media and intima. The greatest rise in uterine artery blood flow (y) occurred after peak proliferation in the uterine artery and in concert with radial artery medial and intimal proliferation (y = 1.99 x 10(0.023x) where x is day postconception). 17beta-Estradiol treatment for 14 d in ovariectomized guinea pigs increased DNA synthesis in the radial artery adventitia and tended (p = 0.08) to increase labeling indices in the media of all vessels examined but did not fully reproduce the effects of pregnancy. We concluded that pregnancy-related, possibly hormonal stimuli prompted growth in all layers of the uterine artery wall by mid-pregnancy and served to initiate a rise in uterine blood flow. The resultant increase in flow and shear stress likely stimulated DNA synthesis in the radial artery which helped sustain the rise in flow near term.

Pregnancy-stimulated growth of vascular smooth muscle cells: importance of protein kinase C-dependent synergy between estrogen and platelet-derived growth factor.

Dramatic smooth muscle cell (SMC) growth occurs in the uterine artery during pregnancy. The potential for pregnancy-associated growth may also exist at other vascular sites. We tested the hypothesis that increased growth of uterine artery SMC isolated from pregnant (vs. nonpregnant) guinea pigs would be detectable in culture, that pregnancy-associated phenotypic changes would also be found in nonuterine vascular cells (aortic SMC), and that the enhanced growth would be dependent on estrogen, peptide growth factors like platelet-derived growth factor (PDGF), and protein kinase C (PKC). Growth responses were measured by [3H]-thymidine incorporation and cell counts. Uterine artery SMC from pregnant guinea pigs grew to a higher plateau density with serum stimulation, had increased spontaneous DNA synthesis and persistent growth following serum with-drawal, and were more responsive to 3-30 ng/ml PDGF-BB than nonpregnant cells. Aortic SMC from pregnant animals also grew to a higher plateau density and had enhanced responsiveness of PDGF-BB. This increased response to PDGF-BB by pregnant uterine artery and aortic SMC (40-233% increase over nonpregnant PDGF result) was reproduced in nonpregnant cells by pretreatment for 1-24 h with 17-beta(beta)-estradiol (30-100 nM). Neither the pregnancy-induced difference nor the estradiol pretreatment was associated with increased PDGF-BB binding activity. The synergistic effect of 17 beta-estradiol was partially (62%) reproduced with 17-alpha(alpha)-estradiol, an isomer which does not bind the estrogen receptor. This suggested that 17 beta-estradiol modulates the PDGF-BB response by both estrogen-receptor- and nonreceptor-mediated mechanisms. To test if the estrogen effects were dependent on PKC, two different antagonist strategies (3 microM dihydrosphingosine and phorbol-ester-induced downregulation) were applied prior to 17 alpha- or beta-estradiol and blocked the enhanced responses to PDGF. The synergistic effect of 17 beta-estradiol on PDGF was then reproduced by 1 h pretreatment with the cell-permeable PKC activator, 10 nM PMA. We conclude that pregnancy stimulates increased growth of uterine and aortic SMC in vitro which is dependent on estrogen, PDGF, and PKC and may be important in vascular remodeling during pregnancy.