Thick Fix: Should thickened liquids be recommended or are they just a quick fix?

George Barnes with editing and guidance from Dr. Ianessa Humbert

Thickened liquids have been a point of much contention. For the most part, they’re over-recommended and under-utilized. If a tree falls in the forest and there’s nobody around to hear it, does it make a sound? Similarly, do your recommendations have any value if nobody follows them in the first place? Of course, this isn't the case for everyone (but it is for most). While thickened liquids hold value, that value has been up on a pedestal for so long that many clinicians don’t even consider any other options first.  Let’s look at the research before we dive any deeper into thick liquid. 

The value of thickened liquids

Thickened liquids DO in fact have value in some circumstances. They have clear benefits that are well supported by the research including improved timing, control, sensation, and hydration, as well as reduced penetration and aspiration. This makes sense. Thin liquids are tough to swallow. We’ve all had them go down the wrong pipe from time to time. They are slippery and move fast through oropharynx which will have obvious implications on a patient with decreased bolus control and/or decreased laryngeal vestibule closure response time (bombs away!). Even in patients who don’t have a timing issue, as thin liquids speed down the oropharynx the bolus stretches out making it difficult to propel in one fell swoop. Thickened liquids, instead, are more cohesive so they keep their shape as they move down the oropharynx. This may mean increased residue for thin liquids- Something not always considered since intuition would make us think the opposite. 

Thickened liquids aren’t a panacea though. Thicker = heavier and a heavier bolus will naturally be more difficult to propel.  So there is a cutoff point as to when the benefits of thickened liquids start to decrease and the cons (increased residue) start to increase. Unfortunately, there is no agreement over where this cutoff point is and so we don’t know which viscosity is “best.” And don’t forget, not all thickener is created equal. Starch-based thickeners, for example, get thicker as they sit making their viscosity highly variable. On the other hand, gum-based thickeners are more stable and tend to be more cohesive, making them less likely to cause residue after the swallow. 

So yes, thickened liquids are an excellent choice to improve airway protection (especially gum-based or naturally thickened liquids) for some patients. BUT is the elimination (or even reduction) of airway compromise at all costs the end goal? Some argue not. And I’d agree. Research shows that there is no significant difference in pneumonia rates for patients with dysphagia who take thickened liquids and those who take thin with safety strategies. But this is only applicable to patients who are able to use safe swallow strategies and for patients who have a low risk of pneumonia. Then since thickened liquids can be helpful for some patients, we should be thoughtful about who we are recommending them for (and we should only make that decision under their guidance of an instrumental study). 

What does the patient think? 

First things first, what does the patient think of thickened liquids? And will they drink them? Sounds like a simple question, but it’s probably the most important one to ask when considering this intervention. Most patients dislike them and will not drink them (or at least not as much of them). Why not? They taste bad (as if you needed research to qualify that statement). BUT, there are a minority of patients who do prefer thickened liquids. Think about the patient who coughs on every sip of thin (no fun, right?). Dysphagia brings with it a high amount of anxiety and if we can reduce that anxiety by offering them thickened liquids, maybe that is the best choice.

But for most a recommendation for thickened liquids without a thoughtful discussion becomes a recommendation for no liquids at all (unless they can sneak some thin in from family or easily cajoled hospital staff). Without allowing them agency, we are essentially putting these patients in a sort of diet prison where they are barred from one of the most basic pleasures in life. Not to mention the impact this has on dehydration (actually maybe I will mention it…). 

Dehydration

Research shows that patients who drink thickened liquids have an increased risk of dehydration. Chicero, 2013 rejects the claim that this is secondary to changes in the bioavailability of water in thickened liquids. Instead, the study claims we are dehydrated because we drink less of it. Remember? Thickened liquids don’t taste good. Chicero goes on to tell us that it takes longer to drink thickened liquids and it makes you fuller faster.  Ever try chugging a milkshake? Do that eight times and your stomach may take out a restraining order against you.

On the other side of the coin lies the fact that some people are at increased risk of dehydration without thickened liquids. People with dysphagia are already at increased risk of dehydration. But the cause for dehydration is multifactorial, ranging from dependence on feeders to reduced thirst and polypharmacy in the elderly.  But don’t forget- Drinking thin liquids is hard, right? And for those with intact sensation, it is uncomfortable (because of increased coughing). Nobody wants to cough and choke their way through a glass of water, and so, they drink less of it. Thickened liquids may give people the opportunity for a safer, more comfortable way to consume liquids which has the obvious benefits of improving the opportunity for hydration. 

While this issue is mixed, what isn’t is the fact that our patients with dysphagia are at risk for dehydration and that risk may be increased when we thicken their liquids. Then at the very least we should be monitoring our patients for dehydration by following the lab work (preferably with the dietician) so that we are staying on top of this risk.

Bioavailability of medication 

Research shows that thickened liquids can actually impact the way your body processes medication. With a thicker viscosity, the breakdown of certain chemical compounds in the medication actually slows down; making it take longer for medication to enter the bloodstream. This, of course, has tremendous clinical implications for the patient, as many medications are time-released which will alter their effectiveness and possibly cause them to overlap with other medications. These effects can compound from day to day, the result of which is simply unknown, but can be significant. The impacts can escalate with our most vulnerable patients: The elderly. Geriatric patients process medications slower and tend to be on more medications in the first place. This is all the more relevant because the elderly also tend to be the ones who will need thickened liquids.

To thicken or not to thicken: That is the question

Thickened liquids certainly have their place in dysphagia management. As they say, don’t throw the baby out with the bathwater (Why do they say that?). Thickened liquids are crucial for certain patients, especially when used short-term after acute illness and during recovery. Preventing aspiration and respiratory compromise is that much more crucial for the acutely ill especially if fighting off another infection or if their lungs are already trying to heal from a respiratory disease process. Furthermore, many patients don’t mind them. Or even prefer them. For example, early in my career, I spent weeks doing pharyngeal strengthening exercises for a patient and eventually advanced him from nectar thick to thin liquid only to find that he actually enjoyed the taste of thickened liquids and decided to stay with them (they reminded him of a drink he used to have in Latin America). The issue here was that I didn’t take the time to have a thoughtful discussion about what the patient wanted in the first place (And I never made that mistake again).  

Thickened liquids aren’t a panacea, but they aren’t all bad either. In fact, they can be life-changing for certain patients, making it so they can safely take in fluids and more comfortably hydrate themselves. As long as thickened liquids are recommended under imaging (FEES or MBSS), they are a valuable tool to have handy for our patients (especially since research shows that silent aspiration is higher in thickened vs thin liquids).   

None of this takes away from the reality that our default has been and is still towards thickening liquids. A “thick fix” as I like to call it. We are putting our patients on thickened liquids without properly weighing the pros and cons with the patient and without the instrumental study needed to ensure efficacy. Worse, sometimes these patients are left in this diet jail for long periods of time without a proper re-assessment…for years. Our patients deserve better than the default. They deserve the thoughtful care we all want to provide. They deserve regular discussions about the many different options they have outside of thickened liquids. They have choices. And so do we. 

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Ianessa Humbert, Ph.D. is an accomplished scientist, professor, and highly sought-after speaker with expertise in swallowing and swallowing disorders. Based on hundreds of speaking invitations from around the world, the most common feedback from attendees continues to be “This is the first time a course has really forced me to think about what I’m doing”. Dr. Humbert’s teaching philosophy requires attendees to question everything they think they know before learning can begin.