Tasty Morsels of Critical Care 060 | The post cardiac surgery patient

4 Apr

Welcome back to the tasty morsels of critical care podcast.

Oh chapter 26 devotes a whole chapter to this and for those of us in cardiac units the arrival of several post cardiac surgery patients a day in your unit is a routine part of the day. At least it was pre-pandemic anyhow. As such it presents a fairly predictable work load and patient cohort for your ICU. Given the bewildering number of conditions that can present to a mixed ICU on a given day, knowing that you have a couple of hearts moving along the production line provides a degree of predictability to the workflow.

The scheduled, usually elective nature of cardiac surgery lends itself to large scale outcome prediction and indeed, cardiac surgery has found its outcomes examined very closely over the past few decades. Outcomes are often examined in great detail and are more likely than most patient cohorts to be reflected onto the hospital and even individual surgeons.

Today we’ll focus mainly on the routine cardiac surgery patient and some of the common significant issues you’ll see.

Before we look at any specific cardiac surgeries, it is worth addressing the hand over. There is frankly a lot of information to assimilate and sift through. You will often be receiving handover from the anaesthesia team but also trying to tease out information from the surgeons almost simultaneously. Key points of information to glean are:

  • pre surgical state, including what the heart looked like on TOE pre bypass – eg. is the ventricle good or bad at baseline
  • what was done and how the plumbing stands as of now
  • bypass time, cross clamp time
  • how did separation from bypass go – are they on 2 pressors and 2 inotropes and some nitric? or have they arrived on some propofol and a tincture of noradrenaline and a big sticky label saying “extubate me”
  • heart rhythm and presence and need for pacing (indeed if not being used is it at least on backup?)
  • what did the heart look like on TOE following the surgery – is the valvular lesion fixed? are they, dare i use the terrible phrase, “underfilled”
  • products given and current state of reversal and need for protamine
  • where the drains are and what they’re doing (are they just mediastinal or are they pleural too? Was that 400mls of red stuff there when you left theatre or has it just appeared)

Contra to most ICU patients, cardiac surgery patients often benefit from a bit of the salty water stuff. Likely driven by rewarming induced vasodilation and hypothermia induced diuresis they can be hypovolaemic. It doesn’t take them long to transition to the more conventional ICU patient where fluid does nothing but increase the oedema but in the first 6-12 hours fluid resuscitation often has a role.

Episodes of hypotension are common and the major concerning causes are going to be surgical bleeding or tamponade. The drains that you checked at handover are both diagnostic and therapeutic. A big gush of blood from the drain and hypotension usually points to the problem while at the same time relieving any potential tamponade. Significant bleeding might be >200ml/hr in the first hour or two and >100ml/hr after that.

Unfortunately blood can clot focally around the heart causing a focal tamponade. This can be a bit trickier to diagnose as one might imagine, and indeed some form of imaging is often needed to make the diagnosis. Oh is very down on the utility of TTE in cardiac surgery patients and while of course you aren’t going to get all the windows, a good sonographer can usually answer many of the key questions. That being said if the patient is crashing you often need a TOE to look at the tricky spots like behind the LA where clots have tendency to form obstructing LA inflow. Both surgical bleeding and tamponade are surgical issues that once diagnosed should prompt a return to theatre. Any major issues with shock in the first 12-24 hrs should always have “return to theatre” somewhere on the list of possibilities. Finally for tamponade don’t forget the CVP. While much maligned in general critical care, when it comes to cardiac surgical patients the CVP provides some nice screening information for issues like tamponade and RV function

Atrial fibrillation is common everywhere in the ICU and it is unsurprisingly common in the cardiac surgery population. Its incidence comes in somewhere around 20%. Much of it occurs beyond the first 24 hrs, often when they have left my particular unit. Causes are numerous and much of the basics will happen automatically with correction of potassium and magnesium. It remains unclear what the best way is to manage cardiac surgery related a fib, but the usual suspects of beta blockers and amiodarone are the commonest interventions with vitamin A leading the way, particularly when they’re still a bit sick and shocked and ventilated, and beta blockers playing more of a role once the tube is out and the pressors are gone. Cardioversion is probably not the way to go for these patients.

Interestingly I just read an RCT that suggesting leaving the pericardium open a small bit at the end of surgery reduced the rates of post op a fib from 30% to 17% with no significant consequences. It was single centre and may well disappear into the midst of unreproducible research but would be a nice move if it turns out.

Reading:

Oh Chapter 26

 

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