Things We Do for No Reason: The Use of Thickened Liquids in Treating Hospitalized Adult Patients with Dysphagia

Modifying oral liquid intake using thickened liquids has been the cornerstone of clinical practice in treating adults with dysphagia.^4,9-11 Water, a thin liquid with a low viscosity, flows rapidly from the mouth into the oropharynx. The rapid rate may be too fast for the patient’s pharyngeal muscles to compensate, thus allowing aspiration.¹⁰ Thickening the liquids is meant to slow the flow of liquids to allow more time for airway closure, which could potentially reduce the risk of aspiration.^10,11

The strongest evidence for thickened liquids originates from a study based on videofluoroscopy findings. Clave et al. studied patients with stroke or traumatic brain injury, patients with neurodegenerative diseases, and healthy volunteers using videofluoroscopy while swallowing liquid, nectar, and pudding boluses.¹¹ Of the 46 patients with stroke or traumatic brain injury, 21.6% had aspiration of liquid into the airway, but this incidence was reduced to 10.5% and 5.3% when the diet was modified to nectar and pudding, respectively. Of the 46 patients with neurodegenerative diseases, 16.2% had aspiration of liquid into the airway, which was reduced to 8.3% and 2.9% when given nectar and pudding boluses, respectively. Thus, thickened liquids significantly improved the videofluoroscopy results, leading to a presumptive decrease in the rate of respiratory complications. Other authors have reached similar conclusions in different settings and selected patient populations.⁹ These results, although mostly based on imaging findings and in only narrow populations, have been widely extrapolated to routine clinical practice.^1,9,12

Evidence against thickened liquids dates back to 1994, when a comparative effectiveness trial of stroke patients found that family instruction on appropriate compensatory swallowing techniques without the use of thickened liquids carried no increased risk of pneumonia, dehydration, malnutrition, or death when compared with thickened liquids.¹³ Recent evidence has established the risk for harm with thickened liquids. Specifically, patients assigned to thickened liquids in one study had a higher rate of dehydration (6%-2%), fever (4%-2%), and urinary tract infections (6%-3%) than those assigned to thin liquids.¹⁴ This is presumed to be related to poor fluid and nutritional intake resulting from the thickened liquids.^1,9,14

Patients’ perceived quality of life is also lower when on thickened liquids. Studies typically measured this using the validated Swallowing Quality of Life (SWAL-QOL), which is a quality-of-life and quality-of-care outcomes tool designed for patients with oropharyngeal dysphagia.^1,15 One study found that those started on thickened liquids had a significant reduction in their SWAL-QOL score by nearly 14 points (P < .05).¹⁵ Perhaps because of this reduced quality of life, patient compliance has been reported to be as low as 35% at five days.¹⁶

Several systematic reviews support allowing access to free water rather than limiting patients to thickened liquids in the setting of dysphagia. Gillman et al., Kaneoka et al., and Loeb et al. found no statistical difference in the risk of developing aspiration pneumonia in patients granted access to free water when compared to those with thickened liquids.^1,9,12,15 In the meta-analysis of Gillman et al. of 206 patients, there was no significant increase in the odds of having lung complications when allowing patients access to free water in comparison to thickened liquids (odds ratio 1.51, 95% confidence interval 0.2-100.03).¹ The meta-analysis of Kaneoka et al. showed no significant difference in the odds of developing pneumonia in patients with access to free water compared with thickened liquids in a sample of 135 patients (odds ratio 0.82, 95% confidence interval 0.05-13.42).¹² However, the systematic reviews of Gillman et al. and Kaneoka et al. included studies with stringent exclusion criteria, including impaired cognition and mobility limitations, which limits their applicability.^1,12