Highlights
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## Responding to cardiac arrest in high-rises

For out-of-hospital cardiac arrest occurring in high-rise residential buildings, the survival rate is lower for patients on higher floors, according to findings of a large retrospective database study from Ontario. The logistics of delivering emergency care in high-rise buildings may contribute to lower survival. **See Research, page [413](http://www.cmaj.ca/lookup/volpage/188/413)**

![Figure1](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/188/6/393/F1.medium.gif)

[Figure1](http://www.cmaj.ca/content/188/6/393/F1)

Response times for patients experiencing cardiac arrest on higher floors of residential buildings are longer than average, and emergency personnel find lower rates of shockable rhythms. These are some factors underpinning decreased survival within this group. Several measures may improve access and outcomes, including smartphone technology and training of local lay first responders. **See Commentary, page [399](http://www.cmaj.ca/lookup/volpage/188/399)**

## Danger of adding insulin to metformin

![Figure2](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/188/6/393/F2.medium.gif)

[Figure2](http://www.cmaj.ca/content/188/6/393/F2)

Adding insulin rather than a sulfonylurea to metformin for the treatment of diabetes was associated with a higher risk of hypoglycemia. This retrospective cohort based on the Veterans Health Administration database included 2948 patients who added insulin and 39 990 patients who added sulfonylurea to metformin therapy and had follow-up data for up to four years. Using propensity matching, the adjusted hazard ratio for a hypoglycemic event with insulin compared to sulfonylurea was 1.39 (95% confidence interval 1.12–1.72). This result calls into question the apparent equivalence of these choices in current guidelines, suggest the authors. **See Research, page [E104](http://www.cmaj.ca/lookup/volpage/188/E104)**

## Guidelines: screening for lung cancer

The Canadian Task Force on Preventive Health Care has updated its recommendations on screening for lung cancer. In contrast to its previous guidance, the task force now recommends using low-dose computed tomography to screen adults between 55 and 74 years of age who are at high risk for lung cancer (i.e., those who smoke or who quit smoking within the past 15 years and who have at least a 30 pack-year smoking history) on an annual basis for three consecutive years. The change in recommendation is based on a systematic review incorporating new evidence. **See Guidelines, page [425](http://www.cmaj.ca/lookup/volpage/188/425)**

## Acute low-back pain

A 46-year-old factory worker presents to his family physician with a one-week history of low-back pain. Does he require radiography or computed tomography imaging of his back? Should he stop working? Which medications should be considered? This Choosing Wisely Canada article reviews the literature on the management of acute low-back pain. **See Decisions, page [441](http://www.cmaj.ca/lookup/volpage/188/441)**

## Convulsions after concussion

![Figure3](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/188/6/393/F3.medium.gif)

[Figure3](http://www.cmaj.ca/content/188/6/393/F3)

A 17-year-old boy had convulsions immediately after falling on the ice and hitting his head while playing hockey. Is this a one-time event, or is he at risk of further seizures? Ellis and Wennberg explain the important differences between concussive convulsions and posttraumatic epilepsy and how these affect investigations, treatment and prognosis. **See Cases, page [443](http://www.cmaj.ca/lookup/volpage/188/443)**

## Endovascular thrombectomy in stroke

![Figure4](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/188/6/393/F4.medium.gif)

[Figure4](http://www.cmaj.ca/content/188/6/393/F4)

Endovascular thrombectomy with retrievable stents is the standard of care for patients with acute ischemic stroke from large-vessel occlusion, but there are several caveats, say Joundi and Boyle. These include the presence of substantial neurologic deficits, lack of an established infarct and the ability to provide rapid treatment within six hours of symptom onset. **See Five things to know about …, page [446](http://www.cmaj.ca/lookup/volpage/188/446)**

## Remission of thyroid tumour

A 67-year-old woman had a large thyroid tumour (lymphoma) and lymphadenopathy after treatment of her rheumatoid arthritis with sulfasalazine and methotrexate. The tumour and lymphadenopathy resolved after methotrexate treatment was discontinued. Physicians prescribing methotrexate for rheumatoid arthritis may wish to keep in mind its associations with lymphoproliferative disorders, say Watanabe and Kajiwara. **See Clinical images, page [447](http://www.cmaj.ca/lookup/volpage/188/447)**