Bolus: a large dose of a substance given by injection for the purpose of rapidly achieving the needed therapeutic concentration in the bloodstream. (Merriam-Webster Dictionary Online)
Consider a case. You are called to see a patient.
68 year old lady.
Day one post-operative phase following right total hip replacement.
Documented Operating Room notes as ‘oozy’ operation.
Tachycardiac, hypotensive, dry mucous membranes ECG normal Sinus Tachycardia, normothermic. Moderate haemoserous loss via drain.
Decision made to give 500ml intravenous crystalloid bolus.
500ml is diligently dialled up on the infusion pump to the maximum flow rate (1000ml/hr) and ‘start’ is pressed.
Is this resuscitative fluid therapy? Is it a fluid challenge? Has the goal of therapy been defined?
Are we going to be able to assess for a significant response to these fluids?
As a critical care nurse I am amazed at how frequently in a ward context, compromised, hypotensive and clinically dry patients receive an infusion rather than the requested bolus. I am also equally as surprised that the prescribing medical officer, unless directly asked ‘how fast do you want it in?’ will not specify, yet when prescribing maintenance fluids, will diligently document a precise order of 42ml/hr.
This post is really intended to stimulate some thought about the logistics and human factors that dictate what version of an immensely common therapeutic action our patient receives.
As an in-hospital Medical Emergency Response Nurse, I am routinely employing the probing question of ‘how fast would you like that fluid administered?’ I also attach an addendum – ‘do you want it over half an hour, or would you like to pull it out of the pump so we can give it quicker, evaluate the response and you can work through some other things?’
In terms of practicalities in the delivery (lacking the presence of a medical or nursing student) – a pressure bag will free up a pair of hands from squeezing the IV fluids in by hand. In the absence of this purposefully designed solution, I have often used a manual BP cuff, wrapped firmly around the upper half of the bag and then pumped up.
Both of these options are great because you are able to observe the pressure registered by the cuff on inflation and have an estimation as to the amour of force being exerted to the forward flow against the patient’s own BP and tubing resistance. It is important to note, this does not absolve us from monitoring the patient’s response and observing the IV catheter site, but frees up a pair of trained hands to do some more meaningful (even if it is hold the patient’s hand and reassure them, explaining what is happening).
I have attached an list of my favourites for recommended reading/viewing below. These resources have all improved my understanding of the humble fluid bolus.
An elegantly simple description by Haney Mallemat @criticalcarenow
Excellent explanation of the details of a ‘Fluid Challenge’
A great compilation of evidence and FOAM links relating to assessment of fluid responsiveness.
A thought provoking and enigmatic discussion on fluids in sepsis from Paul Marik, nicely moderated by Scott Weingart @emcrit