Clinicians are confronted every day with a growing number pacemakers (PMs), implantable cardioverter-defibrillators (ICDs) and implantable loop recorders (ILRs). Collectively these devices are sub summarised as cardiac rhythm management devices (CRMDs). Identification of these devices is simple as long a the patient can present an ID card or some other form of identification. This can become challenging especially in emergencies where such information might not be accessible, and interrogation of the pacemaker becomes a problem.
Using the wrong manufacturer-specific device programmer causes a delay in diagnostic and treatment and can be relevant in these situations.
Techniques to identify a CRMD are following:
- Patient's ID card
- Medical records
- Manufacturers' patient registries (All CRMD manufacturers keep their own in-house registry of patients implanted with their devices and provide 24-hour telephone technical support
- Device specific radiopaque alphanumeric codes (ANC)
All these identification techniques have their problems in clinical practice, and so far no other method or algorithm was available to help out in such a dilemma. Sony Jacob et al. have therefore developed and validated the so-called
Cardiac Rhythm Device Identification Algorithm using X-rays (CaRDIA-X, see below)
The study participants using this algorithm showed an overall accuracy of 96.9%. This study was published in 2011 but only now caught our attention.
We have tried this algorithm on a few X-rays ourselves and came to the conclusion:
Using the chart is a little challenge itself, but very helpful in most cases! Certainly worth keeping in mind!
Jacob S et al. Heart Rhythm. 2011 Jun;8(6):915-22.
We just had the discussion again and finally found a good and solid answer to it:
A 19 year old male was transferred to our unit from casualty with a GCS of 10 (E2, V3, M5) secondary to a little bit of... to many drinks. As he was found lying on the ground with no company an unwitnessed fall was considered and a rigid collar applied by paramedics. A c-spine CT-scan in the hospital showed no abnormalities and the patient was transferred to ICU for further treatment... with the rigid collar still in place!
The question soon arose whether it is safe to remove a rigid collar in the intoxicated and dazed patient after a normal c-spine scan or not. Some argued that the patient should also be examined clinically once sober in order to safely evaluate and clear the spine. As always by the way: The rigid collar was removed in ICU and no further problems evolved.
At that time we just knew it is safe to do so but now we seem to get some excellent evidence supporting this procedure.
Martin et al. have just published a
prospective multicenter study at 17 centers
in which they analyzed
10191 trauma patients that underwent CT of the c-spine during their primary evaluation (67% male, 83% car accidents or falls, mean ISS 11)
They found that
the intoxicated cohort had a lower incidence of c-spine injuries
c-spine CT had a sensitivity of 94%, a specifity of 99.5% and a negative predicitve value of 99.9%!
In words this means that a negative CT-result for a patient gives us a very high confidence that this negative result is true!
Clearing the c-spine by CT-scan in the intoxicated patient is definitely safe, especially when there are no other injuries or history of a high velocity trauma.
Martin MJ et al. J Trauma Acute Care Surg. 2017 Jul 19
Postoperative pain and delirium is a common concern and currently approached by different interventions. There is some evidence suggesting that ketamine given intra-operatively might have an influence on postoperative pain and delirium. Some anaesthetists commonly give a single dose of ketamine intra-operatively for exactly this reason.
Thumbs up for Ket
Ketamine has kept its fascination in various settings, from retrieval medicine onto the the care of critically ill patients in the ICU. Ketamine reduces postoperative markers of inflammation, is a rapid-acting antidepressant drug with an effect lasting for several days and might have neuroprotective properties.
Ketamine also has become increasingly popular as an adjunct to other sedatives in the ICU. There is evidence showing that ketamine used in the ICU has the potential to reduce cumulative opioid consumption after surgery (Asad E. et al. J Intensive Care Med December 8 2015 ).
Even better: It does not cause any kidney injuries, preserves laryngeal protective reflexes, lower airway resistance and much more...
And: Ketamine is cheap and has been used safely for over 50 years by anaesthetists!
The Dark Side of Ket
But there's the other side of ketamine making all of this a little more complicated. After all, Ketamine is a psychoactive drug and has well known hallucinogenic properties. Developed in the 1960s as a dissociative anaesthetic agent it started to appear on the street in the early 1970s and made its way to the 1980s as Special K, Acid and Super C (Dotson JW et al. J of Drug Abuse, Vol 25, Issue 4, 1995).
From a medical point of view there are some worries that these psychotomimetic effects, which are of concern in the critically ill patient, might predispose to delirium (Erstad BL, J Crit Care, Oct 2016, Vol 35, p 145-149).
The PODCAST Trial
On the background of all this facts this trial revealed some interesting findings. Avidan et al. performed a
multicentre, international randomised trial
in which they randomly assigned
672 patients undergoing major cardiac and non-cardiac surgery under general anaethesia
into three groups to either receive a bolus of
placebo (normal saline), low-dose ketamine (0·5 mg/kg), or high dose ketamine (1·0 mg/kg) after induction of anaesthesia, before surgical incision.
Participants, clinicians, and investigators were blinded to group assignment. They found
NO difference in in the incidence of postoperative delirium among these groups
significantly more postoperative hallucinations and nightmares with increasing ketamine doses compared to placebo
This trial seems well performed with an acceptable sample size. The application of a single dose of ketamine before surgery neither prevented delirium nor induced it. With this sample size it seems safe to say that even if ketamine does prevent delirium, its effect would be rather small.
Furthermore, postoperative pain was not influenced by giving a single dose of ketamine and this is in contrast to previous findings and current guidelines. Importantly, most of the previous studies are smaller than this trial, making these findings remarkable.
But what really drew my attention was the fact that the appearance of hallucinations and night-mares was increased for at least 3 days after surgery.
So if ketamine has no influence on postoperative delirium or pain but does induce hallucinations and nightmares, even 3 days after surgery, current guidelines might have to be revised.
The Bottom Line
- The application of a subanaesthetic dose of ketamine during surgery to tackle postoperative pain and delirium does not seem to be as effective as previously assumed
- The usage of ketamine in this setting even seems to have undesirable side-effects like hallucinations and nightmare - and this effect might even last for up to 3 days!
- This trial provides good reasons to look for other options to prevent postoperative delirium!
(Like dexmedetomidine? The answer to this question has just been answered: READ HERE!)
Sometimes there's this moment you read about medical research in the news... sometimes you read lots of rubbish on medical issues in the news... but sometimes you stop and read, and you don't know what to think. This happened to quite some of us a couple of days ago when reading the headlines in the British Independent:
Well, it's not very often you read the term sepsis in the news but the word 'cure' causes estonishment or rather misbelief. Further reading certainly catches your attention: 'A doctor in the US state of Virginia claims to have found his own cure for sepsis' and 'Since then, he has used it to treat 150 sepsis patients. Just one has died of the condition, claims Dr Marik'. And it's not an article from some remote pseude magazine... no, it has been published in 'Chest'! And all this is not due to some novel molecule... it's all about Vitamin C!
Thanks to #FOAMed quite some smart brains have looked into this topic already...
So here's the most important facts you need to know - in short:
What's the Story?
Paul Marik et al. have published a
single-centre retrospective cohort study
in which they have treated
47 consecutive septic patients over a periode of 7 months with intravenous vitamin C (1.5g 6-hourly), hydrocortisone (50mg 6-hourly) and thiamine (200mg 12-hourly)
and then compared these patients to
47 septic patients treated in their unit during the preceding 7 months
Propensity score matching
An overall hospital mortality of 40.4% in the control group compared to 8.5% in the intervention group
An absolute risk reduction of 31.9% and also according to the authors none of the patients in the intervention arm died of sepsis!
What Does This Mean?
These results are quite amazing on the first look, but there's more behind these numbers. Paul Marik has first of all published an observational study: unblinded, uncontrolled, retrospective and low in patient numbers.
There are several limitations that go hand in hand with studies as such and unblinded before-and-after studies have a lot. A major challenge in conducting observational studies is to draw inferences that are acceptably free from influences by overt biases, as well as to assess the influence of potential hidden biases. One of the biggest drawbacks in this current study is the timely/ seasonal difference when patients have been selected.
If you are interested to have a closer look on this you should read Dan's blog entry on stemlynsblog.org HERE.
Studies like this one are an important part of science, but observational studies are observational... not proof!
Why Vitamin C in Sepsis?
There is a scientific rationale behind all of this. As mentioned by Paul in his paper vitamin C levels do fall low in sepsis and the most efficient way to administer it is intravenously. The same is true for thiamin which also goes low in up to one third of all septic patients.
There are two rather small randomised control trials suggesting that vitamin C is safe in septic patients and might actually be of some degree of benefit for the patient.
- Neutralizes free radicals and has therefore antioxydative properties
- Is an important conenzyme for the procollagen-proline dioxygenase, which itself is necessary for the biosynthesis of stable collagen in our body. Vitamin C deficiency leeds to unstable collagen and therefore scurvy
- Is an important cofactor in the synthesis of steroids like cortisol and catecholamines like dopamine and noradrenalin as well
- and it has many more functions that go beyond the scope of this blog entry!
However, the importance of vitamin C in the treatment and prevention of diseases like e.g. the common cold or influenza remains highly contrversial. The observation of some moderate positive influence on the course of disease in some studies could not be reproduced in other trials.
Under normal circumstances vitamin C deficiency is practically non-existent in Europe, but becomes a fact during sepsis. If this is clinically relevant in septic patients seems plausible but remains to be elucidated.
Shailja Chambial, Shailendra Dwivedi, Kamla Kant Shukla, Placheril J. John, and Praveen Sharma. Vitamin C in Disease Prevention and Cure: An Overview. Indian Journal of Clinical Biochemistry. Oktober 2013; 28(4): S. 314–328
H. Hemilä, E. Chalker: Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. 2013
R. M. Douglas, E. B. Chalker, B. Treacy: Vitamin C for preventing and treating the common cold. In: Cochrane Database of Systematic Reviews. 2000; 2:CD000980.
Another great read into the details: Josh Farkas from pulmcrit
More Ifs and Buts
Sepsis is not a disease, its a clinical syndrome that has physiologic, biologic and biochemical abnormalities caused by a dysregulated inflammatory response to infection. The fact that different definitions have evolved since the early 1990s shows that we still struggle to definde sepsis as a single entity. This is one reason why a single therapy might not always be the best for each diesease causing sepsis.
Paul Marik’s publication is interesting and deserves respect. It’s an observational study but provides no evidence by far. Vitamin C might be an interesting novel approach to sepsis but the term ‘cure’ used in the media is inappropriate and misleading.
The term ‘cure for sepsis’ also implicates that vitamin C is a cure for all infections causing sepsis and is therefore problematic.
The Current Bottom Line
- The study published by Marik et al. is purely observational and provides no proof at all.
- Just because vitamine C might be safe in Sepsis does not mean this has to be given. At this stage no recommendation can be made for the use of vitamin C in sepsis.
- Studies like these are an part of research itself - However, the use of the term 'cure' seem problematic and inappropriate in this context.
Marik et. al, J Chest 2017
What's the Problem?
Most radiologic exams, especially computed tomography (CT) scans, use iodinated contrast media in order to improve image quality and therefore diagnostic accuracy. The decision on whether to use IV contrast media is also made on the background of pre-existing renal function as the use of these agents has been linked to increased risk of adverse events like: acute kidney injury, initiation of dialysis, renal failure, stroke, myocardial infarction, and death.
-> So called 'contrast-induced nephropathy' or short CIN!
The REAL PROBLEM is that randomising patients to receive or not receive a contrast-enhanced imaging study when indicated is simply not feasible.
- It has been presumed that these agents are a direct cause of acute kidney injury - and therefore dangerous ☠
But, Hold On: Is There Really a Problem?
The causal relationship between the application of IV contrast media and the development of acute kidney injury has recently been questioned - Seriously questioned!
- It is interesting to notice that most of our current understanding of contrast-induced nephropathy derives from arterial angiography studies.
- Also, many studies looking into this problem were performed without any control populations. These investigators obviously assumed that CIN undoubtably exists but did not compare their cohort to patients not receiving contrast media!
Mitchell AM et al. nn Emerg Med. 2015 Sep;66(3):267-274 or Mitchell AM et al. lin J Am Soc Nephrol. 2010 Jan;5(1):4-9. doi: 10 and more!
- As a matter of fact, serum creatinine level fluctuations (meeting the criteria for contrast induced nephropathy) occur in patients in patients undergoing unenhanced CT at similar rates to those published after contrast-enhanced CT. Newhouse JH et al. (see reference below) for instance looked at a total of over 32'000 patients and noticed that creatinine level increases in patients who are not receiving contrast material as often as it does in published series of patients who are receiving contrast material.
AJR Am J Roentgenol. 2008 Aug;191(2):376-82
Newhouse already suspected that CIN may have been overestimated so far! Also other studies found no increased of acute kidney injury after after contrast media administration in any patient group, regardless of baseline renal function.
Crit Cloud review from March 2014
Crit Cloud review from January 2015
Maybe There is No Major Problem
Two recently published paper further challenge the paradigm of contrast-induced nephropathy.
Hinson J et al. published a single-center retrospective cohort study in 2016 in which a total of 17'934 patient visits to their emergency department over a period of 5 years were included. They analysed three patient groups that where demographically similar: contrast-enhanced CT, unenhanced CT and no CT scan performed. In this largest controlled study of it's kind no difference was found in the incidence of acute kidney injury.
Hinson J et al. Annals of Emergency Medicine, 2017; DOI: 10.1016/j.annemergmed.2016.11.021
And just now Wilhelm-Leen et al. have published their analysis of almost 6'000'000 hospitalised patients in the united states and their risk of radio-contrast associated nephropathy. Their results strongly suggest, that the incremental risk of AKI that can be attributed to contrast-media is modest at worst, and almost certainly overestimated!
Wilhelm-Leen Emilee, J Am Soc Nephrol 28: 653-659,2017
A most recent editorial by Lopez-Ruiz at al. puts this new knowledge into a new perspective.
J Am Soc Nephrol. 2017 Feb;28(2):397-399
- If contrast induced nephropathy does exist, it's relevance in clinical practice seems to have been overestimated so far!
Is There a Way to Prevents Contrast-Induced Nephropathy?
The application of sodium bicarbonate, N-acetylcysteine, statins, ascorbic acid and pre-hydration with IV fluids have been recommended for the prevention of CIN in patients with compromised renal function. Among all of these measures hydration with intravenous saline is considered the cornerstone in the prevention of CIN.
And luckily enough just now The Lancet provides us with a first answer to this specific question. The AMAZING trial published in February 2017 provides fairly good evidence that prophylactic hydration with normal saline does not lower the incidence of CIN.
EC Nijssen et al. The Lancet, Feb. 2017
The Bottom Line:
- Until proven otherwise IV contrast media should be considered potentially nephrotoxic. This is supported by preclinical and cardiac studies. If this is relevant in clinical practice (escpecially for CT scans) is not proven so far... but also difficult to disapprove!
- The risk of contrast-induced nephropathy certainly has been oversetimated so far!
- While prophylactic hydration of the patient has no benefit in regards of CIN, keeping patients well hydrated in general is certainly strongly recommended.
- Quick and proper treatment of the patients underlying condition is most probably more important than worrying about CIN and therefore withholding an indicated enhanced CT-scan!
When filling out the form for a CT scan in you hospital you will not only have to provide clinical information about the patient but almost certainly also the latest creatinine levels. This information is required as many clinicians are worried that IV contrast media might cause iatrogenic acute kidney injury and therefore increased rates of dialysis, renal failure, and death. Despite several reports of contrast-induced nephropathies in the past, the causal relationship between IV contrast media and the development of acute kidney injury has been challenged recently (Read our previous summary HERE).
The major problem is that performing a randomized controlled trial to elucidate the true incidence of contrast-induced nephropathy is considered unethical because of the presumption that contrast media administration is a direct cause of acute kidney injury.
While the discussion goes on Hinson et al. have come up with another nice piece of evidence that in emergency situations there is no reason to withhold the application of IV contrast for CT scans when required.
In this single-center retrospective cohort study researchers have included a total of 17'934 patient visits to their emergency department over a period of 5 years. They analysed three patient groups that where demographically similar: contrast-enhanced CT, unenhanced CT and no CT scan performed. Patients were included when their initial serum creatinine level was between 35 umol/L and 352 umol/L. Of all CT scans, 57.2 percent were contrast-enhanced. The probability of developing acute kidney injury was 6.8 percent for patients undergoing contrast-enhanced CT, 8.9 percent for patients receiving unenhanced CT and 8.1 percent for patients not receiving CT at all. This proofs to be the largest controlled study of its kind in the emergency department and shows that:
In current clinical context, contrast media administration for CT scans is NOT associated with an increased incidence of acute kidney injury. And even though a large randomised controlled trial is still missing it seems safe...
There is no reason to withhold the use of IV contrast media in cases where contrast-enhanced CT is indicated to avoid delayed or missed diagnosis of critical disease.
Hinson J et al. Annals of Emergency Medicine, 2017; DOI: 10.1016/j.annemergmed.2016.11.021 OPEN ACCESS
Crit Cloud Review from 18/01/2015
Oxygen is life! There is no doubt, a lack of oxygen is no good and can have lethal consequences in humans. The mitochondrial reduction of oxygen sustains life in aerobic organisms and therefore makes oxygen to one of our most used medications in critical care.
The Free Radical Theory
But as important oxygen is to help sustain life, it's excess (hyperoxia) has proven to be actually harmful itself. This post provides a brief insight into this topic including some of the important references.
Oxygen toxicity is attributed to the free radical theory in which the partial reduction of oxygen forms the superoxide anion radical. Superoxide is a toxic free radical with an unpaired valence shell electron in the outer orbital and is one of several free radicals known.
These reactive oxygen species are formed primarily in the mitochondria, but also by neutrophils and endothelial cells and by the conversion of xanthines. The anti-oxidant defence mechanisms on the other hand consist of several enzymes and small molecules (Vit. A, C and E, Coenzyme Q etc.). An imbalance of these reactions leads to oxidative stress resulting in tissue damage.
Already back in 1899 J. Lorrain Smith et al. noticed the toxic effect of high oxygen concentrations. It had been observed that "oxygen at a tension of over 100% of an atmosphere produced pneumonia in the normal animal". In their conclusion (at that time called 'General Résumé') they state: "Oxygen which at the tension of the atmosphere stimulates the lung cells to active absorption, at a higher tension acts as an irritant, or pathological stimulant, and produces inflammation". The pulmonary toxicity of oxygen is therefore sometimes still called the 'Lorrain Smith Effect'.
Over the years several investigations have shown the toxic properties of oxygen in mice, primates and also humans.
Gerald Nash et al. finally brought this topic to the level of critical care with an article in the NEJM in 1967. He performed autopsies in 70 patients that had been on mechanical ventilation with high inspired fractions of oxygen. He was able to show that lung damage correlated with the level of FiO2 applied. He also noticed that early changes were mainly oedematous and exudative while the late phase was characterised by fibro-proliferative changes.
Other Implications of Hyperoxia
Haque W et al. J Am Coll Cardiol. 1996 Feb;27(2):353-7.
Another interesting input on this topic comes from Girardi and his team who have published an interesting randomised clinical trial comparing the treatment of ICU patients with either oxygen in a conventional manner or according to a restrictive protocol. In this single-centre study his team have recruited 480 patients with an expected intensive care unit length of stay of 72 hours or longer.
In this interdisciplinary ICU the patients were then randomly assigned to receive oxygen therapy to maintain a Pao2 between 70 and 100 mm Hg (or Spo2 between 94% and 98%, 'conservative group') or, according to standard ICU practice, to allow Pao2 values up to 150 mm Hg (or Spo2 between 97% and 100%, 'conventional control group').
Interestingly, the conservative protocol was associated with an absolute risk reduction for intensive care unit mortality of 8.6% compared with that for patients treated with conventional therapy.
The patient populations were comparable, but still there are some limitations to this study. One of them is that the trial was terminated early due to an earthquake in the region of the hospital. Nevertheless, these findings earn respect.
Take Home Messages
- Oxygen is definitely toxic at high concentrations!
- Oxygen toxicity does not only depend on the concentration of oxygen applied it also depends on the duration of exposure!
What should you do?
- Oxygen is a drug, you need to dose accordingly!
- Keep the FiO2 <0.6 whenever possible... and always at the lowest acceptable
- Current recommendation is to achieve paO2 values of 60-80mmHg (ARDSnet.org)
Never withhold oxygen in an emergency setting, especially when the patient needs it!
For the resuscitation out-of-hospital one of the mainstays besides compression and defibrillation ist the application of adrenalin and amiodarone. According to the new ACLS guidelines 2015 these are the only drugs remaining in the treatment for shockable rhythms.
While adrenaline is given for maximum vasoconstriction in order to promote coronary perfusion pressure CPP, amiodarone and sometimes lidocaine are used to promote successful defibrillation of shock-refractory ventricular fibrillation VF or pulseless ventricular tachycardia VT. While the usage of these drugs is undoubtedly very effective in patients with existing circulation the effectiveness during resuscitation remains a matter of debate.
The Effect of Adrenaline
As a matter of fact it has never been proven that adrenalin actually improves long-term outcome. In 2014 Steve Lin and colleagues published a systemativ review on the efficacy of adrenaline in adult out-of-hospital cardiac arrest (OHCA). They were able to show that according to current evidence standard dose adrenaline (1mg) improved rates of survival to hospital admission and return of spontaneous circulation (ROSC) but had no benefit in means of survival to discharge or neurologic outcomes.
What about Amiodarone and Lidocaine?
Kudenchuck et al. now made the effort to look into the efficacy of amiodarone and lidocaine in the setting of OHCA. Used according to the ACLS guidelines 2016 amidarone is given after the third shock applied when treating a shockable rhythm. Two rather small controlled trials have shown so far that using amidarone actually does increase the likelihood of ROSC and the chance to arrive at a hospital alive. It's impact on survival to hospital discharge and neurologic outcome though remains uncertain.
In this randomized, double-blind trial, the investigators compared parenteral amiodarone, lidocaine and saline placebo in adult, non-traumatic, OHCA. They ended up with 3026 patients meeting inclusion criteria and which were randomly assigned to receive amiodarone, lidocaine or saline placebo for treatment. They finally found that neither amiodarone nor lidocaine improved rate of survival to discharge or neurologic outcome significantly. There were also no differences in these outcomes between amiodarone and lidocaine. Across these trial groups also in-hospital care like frequency of coronary catheterisation, therapeutic hypothermia and withdrawal of life-sustaining treatments did not really differ, making a bias due to treatments after admission unlikely.
- This study was not able to show any benefit of amiodarone or lidocaine in the the setting of OHCA in terms of survival to hospital discharge and neurologic outcome
- Amiodarone seems to improve the likelihood of ROSC and survival to hospital admission (similar to adrenaline)
- As there are no other options, I believe amiodarone should remain part of the standard treatment for shockable rhythms in OHCA
- Lidocaine can be safely removed from CPR sets as there is no benefit of over amiodarone
N Engl J Med 2016;374:1711-22
Resuscitation, June 2014, Vol 85, Issue 6, p 732-740
New ACLS Guidelines 2015, The Changes
As posted on BIJC before, Asad et al. had performed a systematic review on the usage of ketamine as a continuous infusion (>24h) in intensive care patients. The same authors have now published a narrative review providing a more depth discussion about the pharmacological and pharmacokinetic properties of ketamine. Also they present recommendations for dosing and monitoring in an ICU setting.
The Goodies of Ket
Current evidence shows that Ketamine...
- Has no adverse effects on the gastrointestinal tract (bleeding) and does not cause acute kidney injury (compared to nonsteroidal anti-inflammatory drungs, NSAID's)
- Does not negatively influence bowel motility (in contrast to opioids)
- Preserves laryngeal protective reflexes
- Lowers airway resistance
- Increases lung compliance
- Is less likely to cause respiratory depression
- Is sympathomimetic, facilitates adrenergic transmission and inhibits synaptic catecholamine reuptake, therefore increasing heart rate and blood pressure
The Concerns of Ket
- Might increase pulmonary airway pressure and therefore aggravate pulmonary hypertension
- Might cause well known psychotomimetic effects which are of concern in the critically ill patient as this might predispose to delirium
- Interacts with benzodiazepines via the P450 pathway which could result in drug accumulation and prolonged recovery
Concerns Proven Wrong
- Ketamine need not to be avoided in patients at risk for seizures, particularly when used for analgosedation for short periods in the ICU setting
- Current evidence shows no increased intracranial pressure or associated adverse neurologic outcomes associated with ketamine administration in critically ill patients
The use of ketamine for analgosedation in the ICU continues to lack high-level evidence.However, it is effectively used around the globe and remains an attractive alternative agent for appropriately selected patients. Taking current knowledge and evidence into account this is especially true for patients with severe pain unresponsive to conventional therapies.
Taking precautions and contraindications into account ketamine is considerably safe and even avoids potentially adverse side effects of other agents used.
Erstad BL, J Crit Care, Oct 2016, Vol 35, p 145-149
Continuous Etomidate Suppresses the Adrenal Gland in a Dose-Dependent Manner - A Potentially Life-Saving Intervention
An endogenous Cushing's syndrome, mostly caused by an adenoma of the pituitary gland, is associated with significant morbidity and mortality when left untreated. The condition is closely associated to life-threatening infections, diabetes mellitus, hypertension and increased risk associated with surgery.
For Cushing's disease the first line therapy is surgical removal of the pituitary tumor. Sometimes though urgent medical therapy is needed first. It has been shown, that surgical risk may be significantly reduced if cortisol concentrations are normalised preoperatively. Conditions requiring urgent cortisol-lowering measures are severe biochemical disturbances (e.g. hypokalaemia), immunosuppression or mental instability.
Medical Treatment Options
Ketokonazole (yes, the antifungal agent) and metyrapone are used to suppress adrenal steroidogenesis at enzymatic sites. Both agents carry the risk of postential side effects. Mifepristone, a glucocorticoid receptor antagonist, and pasireotide, a new targeted pituitary therapy, are alternative agents. However, they also have their limits and side effects.
Now that's where etomidate joins the game. Interestingly, etomidate and ketokonazole are chemically closely related... they are both members of the imidazole family. Etomidate is used as an anaesthetic agent since 1972 and became popular for hemodynamic stability and the lack if histamine release. In 1983 a Lancet article noted an increased mortality when etomidate was used in critically unwell patients. In 1984 an article in Anaesthesia first showed a link to low serum cortisol levels caused by etomidate. Until now the discussion continues, whether a single induction dose actually negatively influences patient outcome. A meta-analysis in 2010 was unable confirm this apprehension and the debate continues.
Etomidate suppresses the production of cortisol by inhibiting the mitochondrial cytochrome p450-dependent adrenal enzyme 11-beta-hydroxylase and therefore lower serum cortisol levels within 12 hours. In higher doses it also blocks side chain cleavage enzymes and also aldosterone synthase. It might even have anti-proliferative effects on adrenal cortical cells.
On this basis the idea arose, that etomidate might be a useful therapy for severe hypercortisolaemia.
Continuous Etomidate - What's the Evidence
A review article by Preda et al. in 2012 identified 18 publications about the primary therapeutic usage of etomidate in Cushing's syndrome, most of which were case reports. Review of current literature reveals that etomidate indeed suppresses hypercortisolaemia safely and efficiently in patients requiring parenteral therapy. Moreover, etomidate shows a dose-dependent suppression and allows adjustment of the medication to target cortisol levels. At recommended dosages etomidate is considered safe with almost no serious side effects.
The authors conclude, that etomidate is a useful therapeutic option in a hospital setting when oral therapy is not tolerated or inappropriate.
- Continuous etomidate (in non-hypnotic doses) reduces cortisol concentrations in a dose-dependent manner in both hyper- and eucortisolaemic subjects
- The application of continuous etomidate in Cushing's disease is safe and efficient
- After termination of infusion adrenocortical suppression persists for about 3 hours
- The suspicion, that a single dose of etomidate for rapid sequence inductions might negatively influence patient outcome in the critically ill remains a matter of debate
J Clin Endocrinol Metab. 1990 May;70(5):1426-30.
Preda et al. European Journal of Endocrinology (2012) 167 137-143 OPEN ACCESS
Soh et al. Letter to the Editor, European Journal of Endocrinology (2012) 167 727–728
Ge et al. Critical Care201317:R20 OPEN ACCESS
Fluids are one of the cornerstones in the treatment of patients with shock. But with any drug applied, also fluids can harm if given inappropriately! While inadequate fluid resuscitation might result in tissue hypoperfusion and worsening of end-organ function, to much fluid might lead to problems like pulmonary oedema and finally increased mortality. Many measures are used in clinical practice, but most of them lack specificity and are not very representative as a sole marker. One of the better methods to evaluate fluid requirements is the use of dynamic measures that estimate the change in cardiac output (CO) in response to a fluid bolus.
In this regard the use of point-of-care ultrasound (POCUS) has become increasingly attractive in order to use basic critical care ultrasound to asses the need of fluids in a specific clinical setting. Lee at al. have now looked at the sonographic assessment of the inferior vena cava and lung ultrasound in order to quite fluid therapy in intensive care. By taking into account current evidence they have produced an algorithm using these measures to help guiding fluid therapy.
As with any measurement in critically ill patients the pathophysiologic cause of shock must be taken into account. The algorithm presented here seems to work best in patients in hypovolemic shock. To fully understand the following algorithm and its limitations we recommend to read the open access article (see link below).
The algorithm provided is a helpful tool to help assess the need of fluids in a simple and quick manner.
Lee C et al. J of Crit Care 31 (2016) 96-100 OPEN ACCESS
Sepsis certainly keeps us going... either when treating patients on ICU or when it comes to the discussion on what actually sepsis is and how to define it. So far the SIRS (Systemic Inflammatory Response Syndrome) criteria have provided some degree of handle to cope with this syndrome but of course we weren't all quite happy with this. In fact every person with any sort of infectious disease will respond with 2 or more SIRS criteria... but doesn't necessarily have to be septic. As a matter of fact a SIRS is nothing else but a physiologic response to any sort of inflammation.
The New Approach to Sepsis - The SOFA
The new international consensus definitions for sepsis and septic shock try to focus on the fact that sepsis itself defines a life-threatening organ dysfunction caused by a dysregulated host response to infection. By saying this the aim is to provide a definition that allows early detection of septic patients and allow prompt and appropriate response. As even a modest degree of organ dysfunction is associated with an increased in-hospital mortality the SOFA score (Sequential or 'Sepsis-related' Organ Failure Assessment) was found to be the best scoring system for this purpose. It's well known, simple to use and has a well-validated relationship to mortality risk.
Sepsis (related organ dysfunction) is now defined by a SOFA score increase of 2 points or more
The Quick Approach to Sepsis - The BAT
In the out-of-hospital setting, on the general wards or in the emergency department the task force recommends an altered bed side clinical score called the quickSOFA - or alternatively 'the BAT' score:
The New Approach to Septic Shock -Vasopressors and Lactate
Septic shock is now defined as a subset of sepsis in which underlying circulatory, cellular, and metabolic abnormalities are associated with a greater risk of death than sepsis alone. Keeping a long story short:
Septic Shock is now:
- The need for vasopressors to maintain a mean arterial pressure of at least 65mmHg
- a serum lactate level of more than 2mmol/L... after adequate fluid resuscitation
The Bottom Line:
The way it looks like we are left with Sepsis and Septic Shock
Severe Sepsis has vanished and the question remains, whether these new definitions will actually benefit the ones that need it most... our septic patients!
Singer M et al. JAMA. 2016;315(8):801-810.
Seymour CW et al. JAMA. 2016;315(8):762-774.
Shankar-Hari M et al. JAMA. 2016;315(8):775-787.
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?
The discussion on the so-called lactic acidosis and its causes have become increasingly attractive over the last couple of years as several biochemical explanations are challenged. A significant confusion persists on the various relationships between lactate, lactic acid and metabolic acidosis.
Most clinicians continue to refer to the traditional 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 a team member 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 vigorously challenge this traditional 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 of 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 mainly by anaerobic glycolysis by the conversion of pyruvate to lactate by LDH. This chemical reaction results typically 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.