Tasty Morsels of Critical Care

They dig into when to give blood and why transfusion targets matter in critical care. Storage lesions and how donated red cells change over time get a clear rundown. Important transfusion reactions and complications are reviewed. Evidence from trials across sepsis, surgery, GI bleed, and cardiac care is traced to practical haemoglobin targets and noted exceptions for massive bleeding and brain injury.

Welcome back to the tasty morsels of critical care podcast. Today we look at something we do fairly frequently in ICU, especially in the post COVID era: prone positioning or to use its preferred technical term: adult tummy time. This has been around for a long time but was uncommonly done in the pre COVID days and was always a talking point when it did happen. But then 2020 came and you’d spend significant portions of the day proning and supinating patients in the unit. Fair to say it’s something we should have a keen understanding of. Firstly we’ll talk about the physiology and potential mechanism of benefit behind proning. This comes from the proning chapter in Tobin’s mechanical ventilation textbook. Written by none other than the late, great Gattanoni. He argues that there are 3 mechanisms by which proning affects ventilation and oxygenation changes in inflation redistribution of ventilation redistribution of perfusion A lot of this comes from Gattanoni’s early work where they managed to do a whole bunch of CT scans on critically people with ARDS in both the supine and the prone position. Yes you heard that right they did the CT scan prone. The typical CT scan for many ARDS patients is a basal dorsal distribution of disease. One would think that flipping the patient might redistribute this atelectasis to the ventral surface. But what seems to happen is more of a homogenisation of the lung with an overall improved inflation of the lung tissue. No longer are you just hyperinflating the baby lung and doing nothing for the atelectatic lung. This should lead to better recruitment, better perfusion/ventilation matching, better oxygenation and in turn better clinical outcomes. There are some suggestions it may also aid secretion clearance which in a paralysed supine patient is obviously a problem. Proning (as we shall we see) does seem to improve outcomes but the precise mechanism is unclear. Improved oxygenation seems plausible but it may also be a reduction in VILI by having a more homogenous lung that is less prone to injury of the baby lung. Guerin (lead PROSEVA author) wrote a nice review article in 2020 highlighting that proning can make chest wall compliance worse. The anterior ventral wall is normally more mobile than the dorsal chest wall. When prone the ventral bit is now wedged and immobile against the bed hence the fall in chest wall compliance. However lung compliance is probably improved and now that the chest wall is moving less it’s probably increased diaphragmatic movement that recruits the bases. Overall compliance should improve. We turn now to the evidence base for proning our patients. This, like many critical care interventions, this  has a little bit of a narrative to it with some early trials lacking benefit followed by the paradigmatic trial that shapes practice. What follows is a brief summary of some of the important studies and is neither intended nor considered to be comprehensive. Back in the early noughties there were a flurry of RCTs looking at prone positioning in ARDS. The late and great Gattanoi was of course involved in some. The “dose” of proning was variable with sometimes only short periods like 6 hours being used. Results were variable and a 2011 meta analysis of 7 RCTs did not show a definitive mortality benefit but did suggest that those with the sicker lungs had a benefit Enter PROSEVA. A name, that if you’re going into an ICU viva, is probably something that you should keep in your head. This was 26 centres in France who were already experienced with proning. They took people with severe ARDS and randomised them to 16 hrs a day of proning vs no proning. They used mortality at 28 days as a primary outcome and they were looking for a 15% absolute reduction in mortality (which is pretty huge). It was, for obvious reasons, an open label trial. They enrolled 450 patients and found a 32% vs a 16% mortality favoring proning. It’s possible this trial found a benefit due to the dose – they proned for much longer than many of the other trials. It’s worth having some problems related to proning in your back pocket to pull out. The list of potential contraindications was initially quite long pre-COVID but it turns out that when your back is up against the wall we all became a little bolder with our proning. While you can prone the vast majority of patients it’s not going to be possible in those with unstable spinal injuries. One would think that abdominal surgery or advanced pregnancy might be a problem but you can usually work round this with some discussion with your surgeons. The main downsides (beyond the hassle factor) are related to safety. The facial oedema and skin injuries are not insignificant and no matter how careful you are some people just aren’t a great shape for proning. There is a chance that the ET tube can kink or dislodge either on the proning or on the head turns so you need to have a good plan in your head how to confirm this and get someone flipped back if they need it.   Reading Tobin Chapter 49 Deranged Physiology  Prone Position and Mechanical Ventilation Guerin, C. et al. Prone Positioning in Severe Acute Respiratory Distress Syndrome. New England Journal of Medicine 368, 2159–2168 (2013). Guérin, C. et al. Prone position in ARDS patients: why, when, how and for whom. Intens Care Med 46, 2385–2396 (2020).

Delve into the fascinating world of oesophageal balloons, innovative devices that aid in measuring pressures in critical care. Learn how these devices function like fancy NG tubes, providing crucial insights into pleural pressure. Discover their clinical applications, from titrating PEEP to assessing muscle contributions in respiratory injuries. Despite their potential, barriers like cost and compatibility keep them from routine use. Tune in for practical insights and a look at emerging research in respiratory mechanics.

Dive into the complexities of managing pulmonary embolism, focusing on high-risk cases. Explore the critical interventions like thrombolysis and anticoagulation strategies, as well as the nuances of using inotropes and fluids. Learn about the role of CPR, the risks of intubation, and the controversial nature of catheter therapies. Discover the potential of VA ECMO as rescue support and the challenges of surgical embolectomy. Insightful discussions highlight the importance of swift decision-making in critical care!

A focused dive into how to risk stratify pulmonary embolism in critically ill patients. It contrasts PEs found in the ICU with ED referrals and argues CT pulmonary angiography is key. It flags that many ICU PEs are small and clinically insignificant. It highlights the value of echocardiography, RV dysfunction markers, and rising lactate when deciding who needs aggressive treatment.

Dive into the intriguing world of hypertriglyceridemia-induced pancreatitis, where strikingly lipemic blood samples can be a diagnostic clue. Learn when to suspect this rare cause and how triglyceride levels directly correlate with the severity of pancreatitis. The discussion covers the toxic mechanisms of fatty acids and dives into acute management strategies, including nutrition adjustments and insulin use. Plus, explore plasmapheresis as a rapid triglyceride-lowering option, even as guidelines caution against its routine use in acute scenarios.

Dive into the critical world of acute liver failure, where understanding the distinction from acute-on-chronic liver failure is crucial for diagnosis and management. Discover the main presentations like coagulopathy and encephalopathy, and explore various causes, including toxins and viral infections. The conversation also navigates through complications, such as intracranial hypertension, and highlights cutting-edge treatments like high-dose CRRT and urgent transplant referrals. It's a whirlwind through life-saving critical care insights!

Dive into the fascinating world of diabetes insipidus, where tasteless urine takes center stage. Learn about its two types: cranial DI, marked by a deficiency of antidiuretic hormone, and nephrogenic DI, involving resistance to this important hormone. Discover the critical role of ADH in regulating urine output and the challenges it presents in ICU settings. This discussion clarifies complexities within endocrinology, making the topic accessible for anyone navigating critical care.

Dive into the complexities of Heparin-Induced Thrombocytopenia (HIT), where two forms pose different risks. Type 1 is benign, but Type 2 involves serious immune responses that lead to clotting despite low platelets. Learn how exposure to heparin triggers this condition and the role of platelet factor 4 in generating an immune reaction. The discussion also highlights the importance of proper assessment techniques and alternative anticoagulation strategies for effective management.

Dive into the complexities of empyema, a condition often linked to pneumonia. Discover the key bacterial culprits and the significance of clinical assessments and imaging techniques. Learn about innovative drainage methods and injectable lysis therapies, bolstered by insightful trials like MIST-2. The podcast highlights the importance of combinatorial antibiotic treatments while critiquing research gaps, particularly in ICU representation. Prepare to rethink your understanding of chest drains and pleural therapies!