Practical Use of Constant Rate Infusions (CRIs)(Elliot Kneba)

In this guest blog post Elliot discusses the practical use of constant rate infusions (CRIs). Watch the videos, and download the accompanying article by clicking the button below. The article discusses:

  • What CRIs are and when they can be useful
  • Setting up a CRI for infusion pump and syringe driver
  • Possible sources of error

Please share any questions or comments by emailing Elliot at or commenting below.

Trauma Refresher Series: Initial Patient Approach

I am very excited that this is the first blog post published on this site to have been provided by a collaborator!  My good friend Elliot Kneba has kindly agreed to share posts with us from time to time starting with a Trauma Refresher Series. However, before that, let me tell you a bit about Elliot in his own words:

"I am a small animal general and emergency practitioner based in Hertfordshire, UK. Before graduating from the Royal Veterinary College, London, I worked in Florida as a veterinary nurse in small animal general and referral practice. My professional interests include the use of ultrasound in the emergency setting, toxicology, trauma, analgesia and local and regional anaesthesia, as well as learning about how human factors affect the practice of medicine. I am a big believer in the power of veterinary Free Open Access Medical Education (vetFOAMed) and in social media community. 

You can contact me on Twitter as @vethologist or via email at"

Elliot Kneba

Elliot Kneba

Okay, so on with Elliot's first blog post...

If I think back on the cases that have stuck with and impacted me, a lot of them have been trauma patients. Blunt traumatic injuries (e.g. pulmonary contusions, pneumothorax, body wall rupture, skull fracture) are most common in dogs and cats and treating animals after trauma can be complicated and scary. Developing a structured and rehearsed approach to evaluating and prioritising their care can help address problems sooner, reduce missed injuries, and hopefully improve outcomes.

This article will cover one approach to the initial evaluation of trauma patients. It is listed in a continuous format with some interventions listed alongside their associated problems, but use your clinical judgement to decide if you should stop and institute certain treatments (most commonly fluid therapy, analgesia and/or oxygen supplementation) before completing your primary survey. Future articles will discuss treatment concepts for different types of injuries.

When dealing with the trauma patient, you have three initial goals:

  1. To identify and correct life-threatening injuries.
  2. To restore and maintain perfusion.
  3. To relieve pain*.

(*Other than for life-saving or unavoidable reasons, provide analgesia and allow sufficient time for it to work before subjecting the patient to significant movement or handling.)

Inguinal laceration in a cat - the exact cause was unknown.

Inguinal laceration in a cat - the exact cause was unknown.


This is a hands-on activity. You should use all of your senses - look, listen, and feel for injuries. This starts with determining the nature of the injury by obtaining a very brief history and checking the patient’s overall appearance, level of consciousness, and their position (lateral, sternal, any limb or spine flexion). You should then move on to assess for any major injuries that may kill the patient in the short-term. These include catastrophic hemorrhage, open thorax, major airway issues, and others, and if present their treatment should be your top priority. Once these are complete and any necessary interventions have been performed you can move to the Primary Survey, also known as the ABCDs - Airway, Breathing, Circulation, and Disability.

If the patient’s condition allows, place him/her on a warm, padded surface for their evaluation. Try to avoid leaving them on a cold table, as trauma patients are likely already hypothermic and may have compromised thermoregulation.


The goal is to assess for a patent airway, and if compromised, secure it by clearing any obstruction or by intubating the patient. Thankfully significant airway compromise is relatively rare in dogs and cats following trauma; some notable points are as follows:

  • Is there any crying, vocalisation, or whining? This indicates that the airway is patent.
  • Look, listen, and feel for air moving in and out of the patient. Is it moving appropriately? If you are unsure, or if the patient is very hairy, then palpating the thorax and feeling in front of the airway is helpful.
  • Check for obstructions and clear them if possible. Do not put anything into the mouth unless you can clearly visualise the airway, otherwise you risk pushing any obstruction further down. 
    • If fluid or foam is present, then bulb syringes, swabs, cotton applicators/Q-Tips, or suction can be used to remove it.
    • If there is swelling present then intubation or tracheotomy may be required; emergency tracheotomy is however rarely indicated.
  • Signs of a compromised airway include gagging/gasping, labored breathing, pawing at the mouth, drooling, abdominal breathing, extended head/neck with abducted legs (“Sphinx position”), restlessness, or central cyanosis (although this may be a delayed development so not a reliable indicator). 


  • Check for signs of breathing? What are the rate and quality of breaths? Are the rate and quality appropriate and sufficient to sustain life? Are the breaths deep or shallow? Fast or slow? What is the effort (inspiratory, expiratory, or neither)? Is there any struggling?
  • Is the thorax compromised in any way (penetrating wounds, thoracic or abdominal wall rupture, diaphragm rupture, tension pneumothorax)? If so, cover any open wounds with plastic dressing, commercial vented chest seals, or cling film with cohesive bandage on top.
  • Are there any penetrating objects in the thorax? If so, secure them in place with bandage or dressing unless they are interfering with CPR.
  • Are there any penetrating wounds? Check for both exit and entry points.
  • If needed or possible, place the patient in sternal position to allow expansion of both sides of the thorax. Avoid dorsal recumbency where possible.


  • Although relatively rare in dogs and cats, it is nevertheless important to check the whole body for any massive or life-threatening external haemorrhage. Assess and control this before moving further.
  • Assess physical perfusion parameters. These include heart rate, pulse rate, peripheral pulse quality, mucous membrane colour and capillary refill time; mentation, extremity temperature and rectal temperature are also useful if less sensitive. Secondary measures such as blood pressure and blood lactate level may be helpful.
  • Address shock induced hypothermia. Prevent further heat loss and as far as practicable implement passive external rewarming. Cover the patient with insulating blankets (fleece, bubble wrap, foil emergency blankets), and place them somewhere warm, dry, and insulated.

Disability / Neurological Deficits

  • Assess level of consciousness. One helpful tool for this is the AVPU Scale, which uses a grading system to assess a patient’s responsiveness. A conscious and responsive patient would receive a grade of A, while a completely unresponsive patient would receive a U; note that the AVPU Scale remains to be more thoroughly investigated in human medicine and even more so in veterinary patients. For patients with more severely altered mentation (P or U), the modified Glasgow Coma Scale can also be used for a more complete assessment and to track changes in condition.
    • A) Alert: Spontaneously awake, normal body function
    • V) Voice: Responsive to voice commands or stimulation.
    • P) Pain: Responsive to painful stimuli.
    • U) Unresponsive: Not responsive to any stimuli.
  • Assess pupils. Are they equal, round, responsive to light? Is the pupillary light reflex synchronous? Any miosis or mydriasis?
  • Address increases in intracranial pressure (ICP) (Head Trauma) for which the Cushing’s Response is a delayed but reliable indicator: an increase in blood pressure and a reflex decrease in heart rate to compensate for raised intracranial pressure (see podcast episode on traumatic brain injury)
  • Assess for spinal cord injury and use spinal cord precautions if necessary.
    • Check for obvious injuries to the back and spinal cord. Is there any pain or tenderness along the vertebral column? Is there any history of any falls from a height (>4m) or road traffic accident?
    • Weakness or paralysis of one or more limbs, or lack of recognition of stimulus or painful stimuli are indicators of spinal cord injury.
    • Check for distraction injuries from trauma such as tail pull or hanging/strangling.
    • Injury to segments C3-C5 can cause respiratory compromise.

Other Comments

How you utilise your team during this time will depend on your staffing level and their training. If it is a single nurse and yourself then you will likely both be occupied during the initial exam and stabilisation period. However, if you have a larger team present, they can help you run diagnostics and collect monitoring equipment.

For any trauma patient, a baseline packed cell volume (PCV)/plasma total solids (TS), lactate, blood glucose, and basic biochemistry (urea, creatinine, ALT), can help assess the severity of trauma and allow you to monitor patient progress. Depending on the mechanism of injury, you may also want to check coagulation times and platelet count (including via peripheral blood smear examination) and perform blood typing.

If you have an ultrasound machine, then performing an abdominal (AFAST) and thoracic (TFAST) focused assessment with sonography for trauma (FAST) can be incredibly helpful, and use of an abdominal fluid scoring system for monitoring purposes has been described. Although much debated, survey radiography may have a role in the trauma patient as long as it is done safely, with minimal stress to the patient and at the appropriate time. If your facility has access to CT, it can be helpful with diagnosing injuries in patients with polytrauma, and can be performed in suitable cases with little or no sedation. There is much debate in human medicine around the appropriate use, some would say excessive use, of CT for screening in trauma patients but that is not for this post!

A cat with abdominal wall rupture after being hit by a car.

A cat with abdominal wall rupture after being hit by a car.


Remember, your priority is to assess and treat life-threatening injuries in the order of greatest threat to life. You must constantly reassess your patient and monitor your patient’s response to therapy, making any changes as needed during the stabilisation period. A full diagnosis of all conditions is not needed at this time. 

This may seem like a lot of information to remember in a stressful situation, but with practice drills (both with your team and by yourself), you can make evaluating a trauma patient as routine as any other physical exam. Recognising the human factors that influence decision making in emergencies can also improve your clinic’s care. Taking the time to do a short (5 minute) debrief with your team following initial management of a trauma patient is always a good idea. This time should be used to evaluate what went right and what could be improved upon. If someone made a mistake, they should be made to feel comfortable enough to talk about it without being criticised. This way, everyone can improve their practice and use every case as a learning experience. 

Finally, remember that dealing with emergencies can be very stressful for everyone involved, especially when both patient and pet carer are traumatised. Your adrenaline is pumping during the initial evaluation period, but after that you will experience an adrenaline crash. Once you are done, take the time to sit down for 5-10 minutes, make a cup of tea, listen to some music, or whatever relaxes you. The period immediately after seeing an emergency patient that is moderately-to-severely sick is not the ideal time to see another patient, as you will not be performing at your best. Look after yourself. However also remember that it is essential to ensure that the patient remains under close observation despite you stepping out for a short break; it is all too easy to get complacent and self-congratulatory on a job well done only for the patient to deteriorate unattended again!

I hope you find this article helpful. If you have any questions, comments, or concerns, do not hesitate to get in touch in the comment section below, contact us via the contact page,  tweet me @vethologist or email me at Thanks for taking the time to read my first post on this site!

Traumatic Subcutaneous Emphysema

This Patient Is Like a Balloon, What Should I Do?

“I wondered what you would do if you have a severe trauma case (such as with massive pneumothorax) and you discover that there is massive subcutaneous emphysema reaching from the thorax site all the way up to the head. Do you do anything about the emphysema?” (Sandy Karl)

I received this question from a Veterinary ECC Small Talker – thanks Sandy! – and thought I would share some thoughts. I am not going to reference any literature here, to be fair I don’t know if there are any clinical papers looking at this patient population. 

What I would say is that you need to make the decision with respect to surgical versus conservative management on an individual case basis based on factors such as:

  • The suspected source of air and severity of injury
  • The mechanism of trauma e.g. blunt trauma versus bite wounds
  • Other concurrent injuries that may be present
  • The patient's clinical status and stability for anaesthesia/surgery

And clearly some 'wait and see' cases may end up having surgery.

(Picture: Liron Hirsch)

(Picture: Liron Hirsch)

The underlying aetiology of the subcutaneous emphysema is important - if known. In her message Sandy mentions a patient with a pneumothorax. It is said that one of the most common causes of subcutaneous emphysema is rupture of the marginal alveoli, what some people refer to as the Macklin effect, secondary to blunt trauma. The air tracks up through the cervical tissue planes and you get subcutaneous emphysema. The majority of these blunt trauma cases resolve without any specific intervention.

If during this ‘wait and see’ period you feel that the subcutaneous emphysema is so severe as to be causing the patient significant morbidity or discomfort then you could drain some of it via needle aspiration/puncture, potentially at multiple sites. I would say however that if you find yourself wanting to do this more than once or maybe twice, it would probably be worth rethinking your approach to the case, reconsidering the source of the air leakage and whether a more definitive approach is needed. And certainly if you feel that the subcutaneous emphysema is sufficiently bad that you are thinking of placing a subcutaneous drain then I would definitely encourage you to reassess your overall management plan again first.

With respect to the underlying aetiology for subcutaneous emphysema then I think most people probably agree that bite wounds (‘tip of the iceberg’) or penetrating injuries should be surgically explored.

Diagnostic imaging is useful in trying to understand the extent and possible underlying cause of subcutaneous emphysema as well as concurrent injuries. For example rupture of the trachea may be apparent by an increase in distance between the individual tracheal rings, but it is also important to realise that even if there is a rupture there may be a pseudomembrane covering the rupture site. As a result you must be careful when anaesthetising these patients, have an appropriate length endotracheal tube and avoid IPPV.

Understanding the anatomy is important. Where has the subcutaneous emphysema come from? Directly from the pleural cavity? From the mediastinal structures? Also remember that the mediastinum is continuous with the retroperitoneum via the aortic hiatus, so you could get a patient with subcutaneous emphysema, pneumomediastinum and pneumoretroperitoneum. If this occurs the clinician should be thinking of causes of pneumomediastinum and ruling them out by appropriate tests e.g. endoscopy of the oesophagus etc. – and not exploring the abdomen!

The other thing to keep in mind is that you could have a patient with subcutaneous emphysema that then gives rise to pneumomediastinum due to tracking of air along the fascial planes, and potentially they could even get some degree of pneumothorax. Reminding yourself about the anatomy and the potential sources and routes of air is important in these cases especially as we don’t see these cases all that often.

All of that said my personal experience is that the patients – often cats – that have subcutaneous emphysema from blunt trauma typically just need conservative management, gentle handling and a tincture of time as far as the emphysema is concerned…but obviously each case has to be approached individually. Furthermore we do not necessarily always identify a specific cause for the emphysema, a specific source of air. Sometimes it is not felt in the patient's best interest to pursue the necessary investigations and he/she recovers without a definitive source being identified.

As always, I would really love to hear your thoughts and experiences here.

Have you seen many of these cases?
How often have you drained subcutaneous emphysema or seen others drain it
Any important points I have failed to mention?