All posts by Timothy

The Myth of Cricoid Pressure – A Correspondence Worth Reading

trachea-intubation-technique-big

One of the most controversial manoeuvres in anaesthesia and critical care has got some new support since the Difficult Airway Society has published their new guidelines in which they basically continue to support the use of cricoid pressure (CP) for rapid sequence induction. The authors of the Obstetric Anaesthetists’ Association and Difficult Airway Society Guidelines for the Management of Difficult and Failed Tracheal Intubation also continue to recommend routine CP, which is considered level 3b evidence.

Surprised on how obstinately CP persists in current guidelines I think that following statement by Priebe HJ is an important reading. It summarises nicely why there is such a disagreement with these recommendations.

He states that

– not a single controlled clinical study provided convincing evidence that the use of cricoid pressure was associated with a reduced risk of pulmon ary aspiration. At the same time, there is good evidence that nearly all aspects of airway management are adversely affected by cricoid pressure

– if cricoid pressure were considered a new airway device, it would not be considered for further evaluation because Level 3B evidence for its efficacy does not exist

– when using cricoid pressure, we may well be endangering more lives by interfer ing with optimal
airway management than we are saving lives by preventing pulmonary aspiration

Priebe HJ, Anaesthesia 2016, 71, 343–351
Want to get more information on the controversy of cricoid pressure? Read here:

Cricoid Pressure for RSI in the ICU: Time to Let GO?

Time to let go? Remarkable article on RSI and Cricoid Pressure

Difficult Airway Society DAS: New Guidelines OUT! Cricoid Pressure still IN?

Lactate – From Bad to Good? An Explanation Trial

Give Him Lactate

The discussion on the so called lactic acidosis and its causes has become increasingly interesting over the last couple of years as several biochemical explanations have been challenged. A big confusion persists on the various relationships between lactate, lactic acid and metabolic acidosis.

Most clinicians continue to refer to the classical understanding of impaired tissue oxygenation causing increased lactate production, impaired lactate clearance and therefore resultant metabolic acidosis. Just recently we had a discussion on our ward round on this topic when I was presented the most recent article of UpToDate online on the causes of lactic acidosis. The authors state that ‘Lactic acidosis is the most common cause of metabolic acidosis in hospitalised patients’ and that ‘Lactic acidosis occurs when lactate production exceeds lactate clearance. The increase in lactate production is usually caused by impaired tissue oxygenation…’… finally suggesting that lactate is no good!

These statements support the classical understanding that:
– Hyperlactatemia is caused by tissue hypoxemia, and
– This in turn then leads to a metabolic acidosis called lactic acidosis

This biochemical understanding has persisted for decades but there are some good reasons to strongly challenge this classical aspect on the ‘bad’ lactate. Lactate turns out to be by far more complex in its characteristics and functions, so I decided to try and make a short but comprehensive overview on this molecule.

What is lactate?
Lactate is a small organic molecule with the chemical formula CH3CH(OH)CO2H and structurally looks like on the image to the left. It is produced in the cytoplasm of human cells largely by anaerobic glycolysis by the conversion of pyruvate to lactate by LDH. This chemical reaction normally results in a blood lactate to pyruvate ratio of about 10:1. And while lactate is produced, NAD+ also is incurred and this actually can accept protons itself, so does not result in acidosis itself.

Lactate arises from the production of energy by consuming glycogen and glucose.

Where does it come from?
Typically most people think of muscles first as an origin of lactate. As a matter of fact lactate originates from many other organs, including our red blood cells. Red blood cells always produce lactate as they lack the mitochondria required to regenerate NAD+ needed for glycolysis. In general you can say that tissues with lots of LDH are the main producers of lactate. Around 20mmol/kg/day of lactate are produced under normal circumstances.

Lactate is not only produced in skeletal muscle.

Muscle: 25%
Skin: 25%
Brain: 20%
RBC: 20%
Intestine: 10%
What happens with it?

Lactate is not just for nothing. After its production by anaerobic glycolysis lactate is reutilised, for instance in the liver and the cortex of the kidneys. As an example: under the influence of cortisol it is used for gluconeogenesis in hepatocytes and restores glucose and glycogen. Also it is a part of oxidative phosphorylation in the liver, kidney, muscles, the heart and the brain. Like this lactate helps conserve glucose levels in our blood.

​Lactate actually serves as a fuel for oxidation and glucose regeneration and therefore is a source for energy itself.


​How does hyperlactatemia develop?

In general you can assume that there is a balance between lactate production and its consumption or usage. The classical understanding that tissue hypoxia leeds to overproduction and underutilisation by impaired mitochondrial oxidation is basically correct.

The key point though is that lactate is also produced via aerobic glycolysis as a response to stress. This happens in septic patients, asthmatic exacerbations, trauma and other critical conditions. In these situations the trigger for lactate production is adrenergic stimulation and NOT tissue hypoxia. There are also several other reasons for hyperlactatemia other than tissue hypoxia:

Sepsis: Adrenergic drive
Asthma: Adrenergic drive
Trauma: Adrenergic drive
Cardiogenic and haemorrhagic shock: Adrenergic drive
Pheochromocytoma: Adrenergic drive
Inflammation: Cytokine drive
Alkalosis, antiretroviral medication and others

Also, there is good evidence showing that organs like the lungs are an important producer of lactate during stress. And of course in all these conditions hypoxic and non-hypoxic hyperlactatemia might also co-exist.

In critically ill patients often other reasons than tissue hypoxia are responsible for hyperlactatemia (e.g. adrenergic drive).

Is lactate harmful?

In contrast to the classical understanding of lactate and lactic acidosis more and more evidence comes up indicating that lactate during stress actually serves as a fuel for energy production. Various tissues, e.g. the myocardium increase their lactate uptake during stress significantly. Also our brain consumes more lactate during stress which is used for oxidation. Research has shown that lactate infusions improve cardiac output in pigs and even in patients with heart failure.

Experimental work on isolated muscles suggests that circulating catecholamines and development of acidic conditions during exhaustive exercise may improve muscles’ tolerance to elevated K+ levels. This implies that during high-intensity activity with high extracellular K+ and adrenaline, lactate actually serves as a performance-enhancing chemical, rather than being the cause of muscle fatigue.

Lactate is not harmful for our organism. On the contrary, recent compelling evidence actually suggests that lactate might actually be beneficial, rather than detrimental, during high-intensity activity and to force development in working heart and skeletal muscle.

Why do critically ill patients with hyperlactatemia die more often then?

In critical care hyperlactatemia indeed is a marker of illness severity and a strong indicator of mortality. This is especially true for patients with sepsis. However, as described above, hyperlactatemia often doesn’t indicate hypoperfusion or tissue hypoxia. Hyperlactatemia rather reflects the severity of illness by representing the degree of our body’s activation to stress. A fall in lactate concentration following treatment of critically ill patients is due to an attenuation of the stress response rather than to correction of oxygen debt.

​Hyperlactatemia reflects severe disease and the patients response to stress. Patients die due to their illness, not because of a high lactate.

What about Ringer’s lactate?

Ringer’s lactate (RL) is not harmful in patients with hyperlactatemia.

As a matter of fact RL turns out to be superior compared to normal saline in hyperlactatemia, acidotic patients and patients with hyperkalemia.

The bottom line

– Lactate is an indicator of stress, a marker of illness severity and a strong predictor of mortality, but not harmful as a molecule itself.

– Lactate is helpful as an important source of energy and an important fuel for oxidation and glucose generation.

– During conditions like septic shock there is no proof that lactate is produced only due to tissue hypoxia. In fact well ventilated lungs produce a large amount of lactate during sepsis. Lactate in sepsis and other critical conditions is mostly not due to hypoxemia or hypoperfusion.

– Ringer’s lactate contains sodium lactate, but not lactic acid. Lactate itself, as mentioned above, is actually beneficial in severe disease. Therefore RL remains the fluid of choice during severe disease like for instance septic shock.

– Ringer’s lactate is superior to normal saline in patients with metabolic acidosis, hyperlactatemia and also hyperkalemia.

Got interested in some better understanding? START READING HERE:

Emmettt et al. UpToDate online, August 2015, Causes of lactic acidosis

Garcia-Alvarez et al. Critical Care 2014, 18:503

Marik PE, Bellomo R. OA Critical Care 2013 Mar 01;1(1):3

Garcia-Alvarez et al. Lancet Diabetes Endocrinol. 2014 Apr;2(4):339-47.

Andersen JB et al. Journal of Experimental Biology 2007 210: vii doi: 10.1242/jeb.001107

Bakker J et al. Intensive Care Med (2016) 42:472–474

Analgosedation with Ketamine in the ICU: What is the Evidence?

Ketamine

Ketamine’s success seems unstoppable:
​+++ Anaesthesiologists are opening private clinics for off-label infusions of ketamine for depression http://bit.ly/1IGYTcI +++ Dr. Jim Roberts says #ketamine is an ideal treatment for excited #delirium: http://emn.online/Dec15InFocus +++ Major #ketamine treatment trial to start in 2016 http://m.huffpost.com/au/entry/8501942 +++ More impressed every day with low dose ketamine for pain management! https://www.youtube.com/watch?v=DgckjVVBb48

Intravenous ketamine is also used in critical care units and to my knowledge most clinicians use ketamine as an adjunct to other sedatives. This might be for patients on mechanical ventilation, intubation procedures or simply as an additive to a patient-controlled analgesia pump. I personally think ketamine is one of the essentials in ICU’s, but what does the evidence say.

Asad et al. have performed a systematic review on the usage of ketamine as a continuous infusion (>24h) in intensive care patients. The aim was to find evidence in favour for the utilisation of ketamine in the ICU.

As a result of this review – current evidence suggests that:

– In critically ill postoperative patients ketamine has the potential to reduce the cumulative morphine consumption at 48h compared to morphine only

– Several trials show the potential safety of ketamine in regards of cerebral haemodynamics in patients with traumatic brain injury, improved gastrointestinal motility and decreased vasopressor requirements

– One observational study and case reports suggest that ketamine is safe, effective and may have a role in patients who are refractory to other therapies
​Our conclusion: THUMBS UP for ketamine in the ICU

 

Asad E. et al. J Intensive Care Med December 8, 2015

What is Better in ARDS: Pressure Controlled or Volume Controlled Ventilation?

IMG_4590

A good question, but do you actually know. Most ICU’s have their standard modes of ventilation and we are busy enough concentrating on the wright PEEP, the perfect tidal volume or prone positioning the patient. But does the mode of ventilation actually have an impact on the outcome? Chacko et al. had a look at exactly this question and performed a systematic review on this topic:

– Early mortality: There is only some moderate-quality evidence suggesting that pressure controlled ventilation might be of benefit, although this was not observed in the long term follow-up!

– Duration of mechanical ventilation: no apparent difference between pressure- and volume-controlled ventilation

– ICU length of stay: no apparent difference between pressure- and volume-controlled ventilation

– incidence of barotrauma: no apparent difference between pressure- and volume-controlled ventilation

– Extrapulmonary organ failure: One underpowered study in favour of pressure controlled ventilation

– Infective complications, Quality of life: To this date no studies available

Conclusion: Current evidence shows no difference between pressure controlled and volume controlled ventilation in ARDS

 

Cochrane, Clinical Answers OPEN ACCESS

Chacko B, Peter JV, Tharyan P, John G, Jeyaseelan L. Cochrane Database of Systematic Reviews 2015, Issue 1. Art. No.: CD008807. OPEN ACCESS

OUT NOW: New and Updated ILCOR 2015 Treatment Recommendations on Cardiopulmonary Resuscitation

Screen Shot 2015-10-23 at 10.28.59

Since the year 2000 the International Liaison Committee on Resuscitation (ILCOR) continues to evaluate all evidence and updates their recommendations in 5-year cycles. The most recent ILCOR 2015 International Consensus Conference was held in Dallas last February and the new treatment recommendation are out now.

Resuscitation remains one of the most challenging situations in health care. Providing basic and advanced cardiac life support gives you the opportunity to virtually safe a patients life but in a very limited period of time. It is an enormous challenge to consider all emerging evidence and pack this into simple and useful guidelines.

It is imperative to for any health care provider to get familiar with the updated guidelines and major changes. Below you can find all relevant links to get the reading going.

The team of BoringEM.org in Canada have provided some excellent infographics to visualise all important changes in the new treatment guidelines since 2010. You should also note that the Canadian Heart & Stroke Association and the American Heart Association have just published the ‘HIGHLIGHTS of the 2015 American Heart Association Guidelines Update for CPR and ECC’, an excellent summary of the new recommendations and changes. So if you can’t find the time to read all of the publication in ‘Circulation’, this will certainly provide all information you need to know.

The links to all infographics can be found on our website HERE
Summary of the Canadian Heart & Stroke Association and the American Heart Association: HIGHLIGHTS of the 2015 American Heart Association Guidelines Update for CPR and ECC


​The original publication in Circulation, October 20, 2015, Volume 132, Issue 16 suppl 1
OPEN ACCESS

​ERC and ESICM 2015 Guidelines for Post-Resuscitation Care

​Based on the the 2015 ILCOR treatment recommendations the European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) have produced these post-resuscitation care guidelines on October the 13th. Recent changes here are the greater emphasis for urgent PCI when indicated, target temperature management at 36°C, prognostic evaluation using a multimodal strategy and an increased emphasis on rehabilitation after survival.


Nolan JP, Resuscitation, October 2015, Pages 202 – 222

Spreading the Word: In Hyperkalemia Ringer’s Lacate is Superior to Normal Saline

Screen Shot 2015-10-17 at 23.50.41

Just recently the discussion came up once again on what sort of infusion should be used in patients with hyperkalemia. To my surprise the idea seems to persist that normal saline (NS) should be used, as this solute does not contain any further potassium. This is a thought in the wrong direction and Pulmcrit made a great statement in 2014 to clarify this myth. The key points are as follows:

Infusing Ringer’s lactate (RL) in a patient with hyperkalemia will actually lower his serum potassium level
Even a solute with twice the potassium concentration of RL (this would be 8mmol/L) would require a vast amount of fluid to create any effect in serum potassium levels
NS has been shown to produce non-anion gap metabolic acidosis, which causes potassium to shift out of cells, thereby increasing potassium levels
RL does not cause any acidosis

Here’s all the background reading including references:

Pulmcrit Myth-busting: RL is safe in hyperkalemia, and is superior to NS


This might also be of interest. Have a very close look on normal saline infusions:

Normal Saline and Acidosis: Is it Really the Salt that Matters?

Antiemetics in the Emergency Department: Sure Look it!

Screen Shot 2015-09-16 at 01.50.18

Many patients admitted to the emergency department (ED) suffer of nausea and vomiting – and many doctors treat this with antiemetics like metoclopramide or ondansetron. Treating nausea is tricky and of course we all try to do our best to comfort patients as good as possible. But are you really sure giving an antiemetic in the ED actually improves symptoms?

Unfortunately results coming in on this topic do not look very promising. 3 publications looked at exactly this setting and although their number of patients isn’t overwhelming the results are rather discouraging.

Egerton-Warburton and colleagues performed a RCDT and looked a total 258 patients who got either metoclopramide, ondansetron or normal saline as a treatment for nausea in the ED. They basically found no differences in reduction of nausea severity.

Back in 2006 Braude et al. already stated in a RCDT including 97 patients that metoclopramide and prochlorperazine were not more effective than saline placebo as an antiemetics in the ED. Only droperidol was found to be more effective than metoclopramide or prochlorperazine but caused more extrapyramidal symptoms.

And in 2011 Barrett and colleagues published a study with 163 patients where they compared metoclopramide, ondansetron, promethazine and saline placebo in the ED. Same again: no evidence was found that ondansetron is superior to metoclopramide and promethazine in reducing nausea in ED adults.
Even if the number of patients is not that big… it’s three trials so far and they all don’t really support the use of antiemetics in the emergency department.
It is interesting to note that these drugs have been proven to be effective in the setting of chemotherapy and in anaesthetics, but the setting in the ED seems to differ. At least most patients experienced some relief over time… most probably to treatment of the cause itself!

Egerton-Warburton et al. Ann Emerg Med. 2014;64:526-532 OPEN ACCESS

Braude, D et al. Am J Emerg Med. 2006; 24: 177–182

Barrett et al. Am J Emerg Med. 2011; 29: 247–255