Ann Robinson’s research reviews—10 September 2021

How much oxygenation is just right for critically ill patients?

This randomised trial seeks to answer the Goldilocks question: how much oxygenation is just the right amount for patients in intensive care units (ICUs)? Hyperoxaemia (too much oxygen in the blood) has reportedly been associated with increased organ dysfunction in critically ill patients. However, in this Dutch trial of 400 patients in ICUs who had evidence of a systemic inflammatory response (a group who may be expected to benefit from supplemental oxygen), randomisation to low-normal oxygenation levels (8-12 kPa) didn’t result in a statistically significant reduction in organ dysfunction compared with a matched group whose oxygenation levels were kept in a high-normal range (14-18 kPa). Both low and high oxygenation groups had similar rates of acute kidney failure (10% v 11%) and acute myocardial infarction (2.9% v 3.6%). The study wasn’t designed to provide a definitive answer on optimal targets for oxygen therapy in critically ill patients, which is a question that urgently needs further study.

JAMA doi:10.1001/jama.2021.13011

Reassuring data on safety of Pfizer and Moderna vaccines

The safety profile of mRNA covid vaccines is under particular scrutiny with the proposed roll-out to younger people, for whom the risks of covid-19 itself are small. The vast interim surveillance data from 6.2 million people in the US, who combined received 11.8 million doses of an mRNA vaccine (Pfizer or Moderna), are reassuring. Serious adverse health events were no greater for individuals in the three weeks after vaccination than they were in the same group from three to six weeks after vaccination. Additional follow-up is needed, and rare or late vaccine related events may not have become evident in this trial period and design.

JAMA doi:10.1001/jama.2021.15072

No gender divide in thyroid cancer

Traditional teaching is that thyroid cancer is more common among women than men—but is it? This cohort study found that the incidence of small (≤2 cm diameter) papillary thyroid cancer (PTC) was indeed 4.39 times greater in women than men, but the incidence of more lethal types of thyroid cancer and mortality showed little or no gender difference. Similarly, subclinical thyroid cancers showed no gender divide. PTCs make up 90% of all thyroid cancers and, at post mortem, equal numbers were found among men and women. So women are possibly being overdiagnosed with small PTCs, and men are probably being underdiagnosed. This could be because women present more readily or doctors are more likely to suspect thyroid cancers in female patients. Either way, this study shows that thyroid cancer is equally likely to kill men and women. And that, just because we learnt something at medical school, doesn’t mean it’s true.

JAMA Intern Med doi:10.1001/jamainternmed.2021.4804

Hope over experience

Depression often coexists with heart failure and worsens outcomes. This single-blind randomised effectiveness trial found that a 12 month blended collaborative care programme delivered by nurses on the phone to treat both depression and heart failure didn’t have an impact on hospital admissions or mortality. However, it did improve mental health related quality of life scores to a small extent compared with enhanced usual care, which was a collaborative approach to heart failure alone or usual care provided by doctors. Subjects were recruited while in hospital, and results may have been different if patients with less severe heart failure had been included. The programme to tackle heart failure and depression together makes perfect sense, but perhaps it needs face to face contact rather than phone calls to make a greater impact. The trial was called Hopeful Heart, but the disappointing results belie its optimistic title.

JAMA Intern Med doi:10.1001/jamainternmed.2021.4978

Lowering blood pressure in 60-80 year olds

What’s the ideal blood pressure for older people? This large, well designed Chinese study of 60-80 year olds with hypertension found that intensive treatment (target systolic blood pressure of 110-129 mm Hg) resulted in a lower incidence of cardiovascular events than standard treatment (target systolic blood pressure of 130-149 mm Hg). During a median follow-up period of 3.34 years, primary outcome events (a composite of stroke, acute coronary syndrome, acute decompensated heart failure, coronary revascularisation, atrial fibrillation, or death from cardiovascular causes) occurred in 3.5% of the intensive treatment group compared with 4.6% of the standard treatment group. Interestingly, safety and renal outcomes were similar in both groups, although there was, inevitably, more hypotension in the intensively treated group. Reassuringly, the increased hypotension didn’t translate into higher rates of dizziness, syncope, or fractures. The concept that aggressive treatment of high blood pressure in older people seems to be safe (not affecting the kidneys or causing fractures from falls) and protective against outcomes such as stroke is potentially of great clinical significance.

N Engl J Med doi:10.1056/NEJMoa2111437

Alcohol and paroxysmal atrial fibrillation

This finding won’t be popular. Individual episodes of atrial fibrillation were associated with higher odds of recent alcohol consumption according to this prospective case-crossover study of individuals with known paroxysmal atrial fibrillation. The study was funded by the US National Institute on Alcohol Abuse and Alcoholism. Subjects wore a continuous ECG monitor and transdermal ankle alcohol sensor (like a tag) for four weeks and pushed a button on the ECG recorder whenever they had an alcoholic drink. Fingerstick blood tests also corroborated the self recording of alcohol intake. Of the 100 participants (mostly male and white with a mean age of 64 years), 56 had at least one episode of atrial fibrillation in the four weeks, and an episode was associated with twofold higher odds of one alcoholic drink, and threefold higher with two or more drinks in the previous four hours. Of course, there may be confounders: for example, you may drink more when stressed, and the apparent association between alcohol and atrial fibrillation may not be generalisable to, for instance, younger people. But it’s also very possible that if you have known paroxysmal atrial fibrillation, you’d be well advised to go easy on the alcohol.  

Ann Intern Med doi:10.7326/M21-0228

Ann Robinson is an NHS GP and health writer and broadcaster