Highlights
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**Urgent air transport of patients** 

Critical events occur in 1 out of 20 patients during urgent air–medical transport. In a population-based cohort study involving nearly 20 000 patients, Singh and colleagues found that procedures for airway management and new hypotension accounted for most of the critical events. Female sex, assisted ventilation or hemodynamic instability before transport, and increased duration of transport were independent predictors of critical events. **See Research, page** [579](http://www.cmaj.ca/lookup/volpage/181/579?iss=9)

Criteria to decide which patients require urgent air transport are widely available, but the data on which these criteria are based are limited, says Isakov. Large cohort studies such as the one described by Singh and colleagues will remain the main source of evidence to inform us of this service. **See Commentary, page** [569](http://www.cmaj.ca/lookup/volpage/181/569?iss=9)

![Figure1](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/181/9/561/F1.medium.gif)

[Figure1](http://www.cmaj.ca/content/181/9/561/F1)

Image courtesy of © 2009 Jupiterimages Corp.

**Crack cocaine and HIV infection** 

Rates of HIV transmission could be reduced among injection drug users if their smoking of crack cocaine is considered as an independent risk factor, say DeBeck and colleagues. In their study involving 1048 injection drug users in Vancouver, 137 acquired HIV infection during the follow-up phases. The risk of HIV seroconversion among participants who were daily smokers of crack cocaine increased over time. **See Research, page** [585](http://www.cmaj.ca/lookup/volpage/181/585?iss=9)

Implementation of harm-reduction programs should address the unique needs of people who smoke crack cocaine as part of a comprehensive HIV prevention strategy, say Celentano and Sherman. The distribution of “crack kits” to this population may have the potential to reduce HIV transmission, they add. **See Commentary, page** [571](http://www.cmaj.ca/lookup/volpage/181/571?iss=9)

**Air pollution and appendicitis** 

Some cases of appendicitis may be triggered by short-term exposure to air pollution, suggest Kaplan and colleagues. In their 7-year study, they estimated the odds of appendicitis relative to short-term increases in concentrations of selected pollutants among 5191 adults admitted to hospital with appendicitis. Their findings need to be replicated in other populations, they caution. **See Research, page** [591](http://www.cmaj.ca/lookup/volpage/181/591?iss=9)

![Figure2](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/181/9/561/F2.medium.gif)

[Figure2](http://www.cmaj.ca/content/181/9/561/F2)

Image courtesy of © 2009 Jupiterimages Corp.

**Series on asthma** 

The avoidance of some risk factors, such as smoking during pregnancy and exposure to occupational sensitizers, can be strongly encouraged in the management of asthma. In the first of a 7-part series, Subbarao and colleagues discuss the rising prevalence of asthma and risk factors associated with the condition. **See Review, page [E181](http://www.cmaj.ca/lookup/volpage/181/E181?iss=9)**

**Don’t pass the salt, please** 

The reduction of sodium in our diets could mean a reduction in serious health problems and mortality rates, say Mohan and colleagues. Government, industry and health professionals all have important roles to play in the reduction of dietary sodium. **See Analysis, page** [605](http://www.cmaj.ca/lookup/volpage/181/605?iss=9)

![Figure3](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/181/9/561/F3.medium.gif)

[Figure3](http://www.cmaj.ca/content/181/9/561/F3)

Image courtesy of © 2009 Jupiterimages Corp.

**Cerebellar syndrome and metronidazole** 

Sarna and colleagues describe 2 patients who developed a cerebellar syndrome after being given metronidazole. Their conditions improved after the medication was stopped. **See Practice, page** [611](http://www.cmaj.ca/lookup/volpage/181/611?iss=9)

**Yellow nail syndrome** 

A 58-year-old woman had yellow fingernails and toenails, intermittent cough and edema. **See Clinical images, page** [614](http://www.cmaj.ca/lookup/volpage/181/614?iss=9)