Hydroxyethyl Starch

Here Today, Gone Tomorrow

J. P. Nolan, M. G. Mythen

Disclosures

Br J Anaesth. 2013;111(3):321-324. 

After a review of the available evidence, on June 14, 2013, the Pharmacovigilance Risk Assessment Committee (PRAC) of the European Medicines Agency (EMA) concluded that the benefits of hydroxyethyl starch (HES) solutions no longer outweighed their risks and recommended that the marketing authorizations for these medicines be withdrawn.^[1] The United Kingdom (UK) Commission on Human Medicines (CHM) concurred and on June 27, 2013, the Medicines and Healthcare Products Regulatory Agency (MHRA) announced the withdrawal of HES products from the UK, giving just 48 h to return all unexpired stock.^[2] In contrast, on June 24, 2013, the United States (US) Food and Drug Administration (FDA) recommended that HES products not be used in critically ill patients or in those with pre-existing renal dysfunction but did not withdraw them completely.^[3]

read more here: http://www.medscape.com/viewarticle/810039

Reducing the risk of anaphylaxis during anesthesia: 2011 updated guidelines for clinical practice.

These guidelines represent the updated consensus of experts in the field of immediate hypersensitivity reactions occurring during anesthesia. They provide a series of valid, widely accepted, effective, and easily teachable guidelines that are the fruit of current knowledge, research, and experience. The guidelines are based on the findings of international scientific research and have been implemented in France under the auspices of the French Society for Anaesthesia and Intensive Care (Société Française d'Anesthésie et de Réanimation [SFAR]) and the French Society of Allergology (Société Française d'Allergologie [SFA]). The members of the European Network for Drug Allergy approved the guidelines. This paper presents the most relevant clinical implications of the guidelines.

Complete Guideline here.

My patient is allergic to eggs, can i use propofol? A case report and review

an interesting case report by Dr. Jamal Tashkandi

Rather than other drugs, propofol is more likely to be used for induction of anesthesia to cause an allergic reaction. Propofol is becoming the most common intravenous agent used for induction as well as maintenance of anaesthesia. Allergy to propofol is rarely reported. We present a case of 4–year-old boy presented for elective adenotonsillectomy with past medical history of eczema and multiple allergies to food. He developed what seems to be an allergic reaction to propofol. We concluded that anaesthetists should be alerted when using propofol in patients with history of atopy or several drug allergies. Current evidence suggests that egg allergic patients are not more likely to develop anaphylaxis when exposed to propofol. If reactions to drugs occurred, it is always advisable to ascertain the exact allergen in each individual case before deciding causality. Serum tryptase, skin prick, intradermal testing, or serologic testing should be done to confirm the diagnosis of an anaphylactic reaction.

source: Saudi Journal of Anesthesia

Heart rate variability: a diagnostic and prognostic tool in anesthesia and intensive care

The autonomic nervous system (ANS) plays an important role in the human response to various internal and external stimuli, which can modify homeostasis, and exerts a tight control on essential functions such as circulation, respiration, thermoregulation and hormonal secretion. ANS dysfunction may complicate the perioperative course in the surgical patient undergoing anesthesia, increasing morbidity and mortality, and, therefore, it should be considered as an additional risk factor during pre‐operative evaluation. Furthermore, ANS dysfunction may complicate the clinical course of critically ill patients admitted to intensive care units, in the case of trauma, sepsis, neurologic disorders and cardiovascular diseases, and its occurrence adversely affects the outcome. In the care of these patients, the assessment of autonomic function may provide useful information concerning pathophysiology, risk stratification, early prognosis prediction and treatment strategies. Given the role of ANS in the maintenance of systemic homeostasis, anesthesiologists and intensivists should recognize as critical the evaluation of ANS function. Measurement of heart rate variability (HRV) is an easily accessible window into autonomic activity. It is a low‐cost, non‐invasive and simple to perform method reflecting the balance of the ANS regulation of the heart rate and offers the opportunity to detect the presence of autonomic neuropathy complicating several illnesses. The present review provides anesthesiologists and intensivists with a comprehensive summary of the possible clinical implications of HRV measurements, suggesting that autonomic dysfunction testing could potentially represent a diagnostic and prognostic tool in the care of patients both in the perioperative setting as well as in the critical care arena.

see more: http://www.gnmhealthcare.com/cgi-bin/vw.pl?a=-12&sc=1053414&c=398&us=0

Effect of patient sex on general anaesthesia and recovery

from BJA:

Background  

Numerous studies have shown that women emerge faster from general anaesthesia than men, and differ in their postoperative recovery profile. The extent and underlying mechanisms for these sex-related differences in general anaesthesia are unclear.

Methods 

In a multicentre, prospective, matched cohort study, 500 ASA physical status I or II patients of either sex undergoing general anaesthesia for elective surgery were recruited. All subjects received a general anaesthetic through inhalation. Anaesthetic drugs and doses used, bispectral index (BIS) scores, recovery times, pain scores, and 40-item quality of recovery (QoR-40) scores for 3 days after general anaesthesia were recorded.

Results 

Women had higher BIS scores at similar concentrations of anaesthesia (P<0.05). Time to eye-opening (P<0.01) and time to obeying commands (P<0.01) were shorter in women. Duration of recovery room stay was longer in women, who also had higher pain scores and need for treatment of nausea and vomiting (all P<0.001). QoR-40 scores for the first 3 days after general anaesthesia were lower in women (P<0.001). Plasma progesterone concentrations in women negatively correlated with the time to eye-opening (ρ=−0.53, P=0.01).

Conclusions 

Patient sex is an independent factor influencing the response to anaesthesia and recovery after surgery. Women emerged faster from general anaesthesia but their overall quality of recovery was poorer. Female sex hormones, particularly progesterone, might be involved, with premenopausal women having faster recovery time but poor overall recovery.

Effect of patient sex on general anaesthesia and recovery

ACE Inhibitors Before Surgery May Do No Harm

Patients on blood pressure drugs experienced lower 30-day mortality

by Alison McCook

Researchers at Toronto General Hospital used data from more than 61,000 patients to compare people who took ACE inhibitors with those who did not, and found that being on the blood pressure medication long-term leading up to noncardiac surgery was associated with lower 30-day mortality.

When they looked more closely at the ACE inhibitor group, they found that those who chose to stop taking the drugs a few days prior to surgery, and delayed restarting it, fared no better than those who took the drug up to the morning of the procedure, and resumed once they were stable.

“Maintaining ACE inhibitors prior to surgery might be of some benefit,” said study author Jason Toppin, MD. “And they definitely do not cause any problem.”

Dr. Toppin’s group presented its findings at the 2011 annual meeting of the Society of Cardiovascular Anesthesiologists (abstract 64).

Decisions Based On Unsatisfying Data

Previous small, retrospective studies had suggested that patients who take ACE inhibitors in the perioperative period are at higher risk for renal failure, hypotension, cardiac events such as myocardial infarction and even death. The reasoning, Dr. Toppin explained, was that any drug that lowers blood pressure might cause problems when combined with either anesthesia or other issues that exacerbate hypotension.

But when he and his colleagues took a closer look at the studies, they felt the researchers did not adequately control for differences between those on and off the drugs. People taking ACE inhibitors are generally sicker, he explained, so comparison studies have to be careful to match them with people who have the same levels of underlying disease.

So Dr. Toppin and his team scanned the hospital’s surgical booking center for all patients undergoing noncardiac surgery between 2003 and 2008. They identified 61,420 patients, 7,339 (12%) of whom were taking ACE inhibitors—or, less commonly, angiotensin receptor blockers (ARBs)—at the time of surgery. They then isolated about 7,200 patients on the drugs and compared them with the same number not taking the medications, taking care to match patients on more variables than had prior studies, such as cardiac failure, renal function and other risk factors, Dr. Toppin said.

They found that those taking ACE inhibitors or ARBs experienced a statistically significant reduction in mortality (odds ratio, 0.54) within the 30 days after surgery. Specifically, 1.4% of those not taking the medications died, compared with about 0.5% of those on ACE inhibitors (P<0.0001).

When they looked within the group taking ACE inhibitors, stopping the drug prior to surgery and for a few weeks afterward was not associated with any better outcomes.

These findings mirror what Arthur Wallace, MD, PhD, of the University of California, San Francisco and his colleagues have seen: Taking ACE inhibitors before surgery poses no added risk.

“When we have looked, it’s hard to show that people with ACE inhibitors have more hypotension during surgery when you give them the drug,” Dr. Wallace told Anesthesiology News.

The finding makes sense, Dr. Wallace added, because if people need the drug to go about their daily lives, they should need it during a time of added stress, such as surgery. “It is hard to show that taking away a good drug is good for you,” he said.

“It just goes back to why people are on them,” agreed Dr. Toppin. “It’s a drug that is associated with beneficial effects in these high-risk patients.”

In 2008, the American College of Physicians issued recommendations on the perioperative management of patients with congestive heart failure, which stated that clinicians should “consider holding or reducing” the usual dose of ACE inhibitors the day of, and for up to 24 hours prior to, elective surgery (http://pier.acponline.org/mcpp/pdf/periopr867.pdf).

Still, the decision to stop or continue ACE inhibitors prior to surgery depends on the individual and institution, Dr. Toppin said. However, some patients do halt their medication over fears of ill effects, based on the results from prior studies. He said he typically asks patients to continue their ACE inhibitors until the morning of surgery, then restart once they are stable.

Yet, the real understanding of the benefits or risks associated with ACE inhibitors will only come after prospective studies, Dr. Toppin cautioned. “We still think the definitive answer still lies in doing a prospective study.”

Researchers should not stop with ACE inhibitors, added Dr. Wallace, who is chief of anesthesia at the San Francisco VA Medical Center. Some regular aspirin-takers stop the drug before surgery, out of fear of excess bleeding, he said, and some hospitals even halt b-blockers for patients during the perioperative period, despite research showing this practice may be harmful. “We need to identify which medicines you need to keep going, and which medicines need to be stopped before surgery. It’s incredibly important.”

Anesthesiology News - ACE Inhibitors Before Surgery May Do No Harm

Anesthesiology News - More Evidence One Size of Anesthesia Doesn’t Fit All

Study also suggests acetaminophen in recovery reduces postpartum depression

by Alison McCook

For women at risk for pain and depression in the months following a cesarean delivery, adding more pain medicine during the operation may help, according to a small study presented at the annual meeting of the Society for Obstetric Anesthesia and Perinatology (SOAP).

All of the 50 women included in the study were considered to be at risk for experiencing relatively high levels of pain immediately after the procedure, as well as pain and depression two months later.

But when half of the women received twice the dose of intrathecal morphine (300 mcg) during the operation, as well as 1 g of acetaminophen (equivalent to two extra-strength Tylenol) every six hours for 24 hours in the recovery room, they experienced significantly less pain on movement and at rest, and had lower pain scores overall, 24 hours after the operation (abstract 87).

“There does seem to be value in identifying patients who are likely to have increased pain requirements, and not treat all comers the same way,” said study author Robert Fish, MD, obstetric anesthesia fellow at Wake Forest University in Winston-Salem, N.C.

Dr. Fish and his team selected their subjects based on their responses to three questions: How much do you expect to hurt after this surgery? How anxious are you about this surgery? How much pain medicine will it take to treat your pain after surgery?

Anesthesiology News - More Evidence One Size of Anesthesia Doesn’t Fit All

In-vitro contracture testing for susceptibility to malignant hyperthermia: can Halothane be raplced?

Malignant hyperthermia is a potentially lethal inherited hypermetabolic syndrome that develops in susceptible individuals following administration of depolarising neuromuscular relaxants or volatile anaesthetics. Genetic analysis can only confirm a diagnosis of malignant hyperthermia in about 70%, and in the remainder an in-vitro contracture test, with halothane and caffeine, on muscle obtained from open muscle biopsy is required to establish the diagnosis. As the licence for clinical use of halothane expired in 2005, its continuing availability is in doubt. More modern volatile anaesthetics such as enflurane, isoflurane, desflurane and sevoflurane are less potent triggers of malignant hyperthermia in humans and pigs. The aim of this study was to investigate whether these agents can be considered possible substitutes for halothane in a modified in-vitro contracture test.

In-vitro contracture testing for susceptibility to malignant... : European Journal of Anaesthesiology

Are Opioids Safe?

Charles E. Argoff, MD

Hi. I am Dr. Charles Argoff, Professor of Neurology and Director of the Comprehensive Pain Center at Albany Medical College and Albany Medical Center in Albany, New York. I would like to talk briefly about, although it is a huge topic, the near crisis (if not actual crisis) we face right now in grappling with the issue of opioid prescribing.

The Opioid Prescribing Crisis

Currently, and over many years, we have learned and appreciated that opioid analgesics (sometimes referred to, unfortunately, as "narcotics," but still opioid analgesics) can be a very effective component in treatment for individuals with moderate to severe pain. We often see the benefits in individuals who have acute pain and pain of a shorter duration that benefits from a short-term treatment with opioids. Where the crisis has emerged is: can we manage individuals safely on long-term opioids? And if so, how can we do so?

Unintentional Deaths From Using "As Prescribed"

Over the last few decades, the cancer pain community has showed us that there is a role for using opioids in pain management. We have been trying to learn the most effective way of using this class of medication in the treatment of chronic pain. Several issues have emerged: first, unfortunately, we have learned that as more opioids have been prescribed, we have seen almost a proportional increase in the number of unintentional deaths associated with use of those agents. There has been much clamor in terms of safety about the number of individuals who, even when they were supposedly taking their medication as prescribed, succumbed to the effects of the medications.

So we are not talking about people who are misusing, diverting, or obtaining multiple prescriptions. We are talking about patients who have been using their medications (to the best of anyone's ability to determine this) "as prescribed," but this medication use resulted in unintentional death.

Right now, it is one of the leading causes of death in certain age groups, and it is a huge problem. Why is it a huge problem? Obviously, it is a huge problem because death from the inappropriate use of medication is never acceptable and can be prevented. But even more so, it presents tremendous challenges not only to the pain specialists, the neurologists, and the anesthesiologists doing pain management, but also to every single prescriber in this country.

Safe Prescribing Tips

Opioids are an important class of medication used in the treatment of acute and chronic pain. We need to learn how to use these drugs as safely as possible. I'd like to highlight a couple of issues because opioids are effective for some but not all people, and they need to be used as safely as possible.

Individualize treatment. First, when you treat somebody with an opioid (and when you treat someone with any class of medication), keep in mind that it is a class of medication; it's not the be all and end all. There are people in whom opioids will either not be well tolerated or will not be effective alone. The expectation is not that you will say, "here's a prescription and that's all we're going to do for you." You need to individualize the treatment plan for each patient using opioids as a component.

If it's an expected duration of pain that is only going to be a few weeks, such as after a severe back sprain or other injury, then that patient should only be given enough medication to last that 2-week period. A return for follow-up should be arranged either in person or by phone so that you, as the prescriber, know what has happened to that person and whether that person needs additional treatment or additional evaluation.

Rational prescribing. All too often, children (adolescents) are getting prescriptions for hydrocodone/acetaminophen combinations after having their wisdom teeth extracted for 60 or 120 pills. Who would imagine that you would need a month's supply of this kind of medication for a simple tooth extraction? Yet this is happening. It happened in 2 circumstances that I am close to, including my own daughter when she had her wisdom teeth extracted. This is crazy; that's not exactly the best way to use an opioid. You should prescribe the smallest amount that the patient might need.

Get a diagnosis. If you are treating someone with acute or chronic pain, you need to have a diagnosis. What am I treating? As you are developing a treatment plan, which may or may not include opioids, you need to do the appropriate testing to evaluate that person. You also need to know if the person in front of you has a history of problems using opioids. That's not to say that you would never use opioids in a patient who may be problematic, but you certainly would use them with much greater monitoring. Keep in mind that unintentional deaths have occurred in people who have never been shown to have any issues.

Consider long-acting preparations. It's very important to consider: what type of opioid am I giving to this patient who is using it long-term? It cannot be said that longer duration of action or longer-acting opioids are superior with respect to pain relief, compared with shorter-acting opioids, but we can say that longer-acting opioids have fewer pills, a potential benefit of not having highs and lows in terms of blood levels, so they are not reinforcing potential addictive behaviors towards the medication and may be less problematic in trying to control someone's pain in a more stable manner.

Currently, many long-acting opioids have doses that are small enough that you can start the patient with a long-acting agent, as opposed to what has been taught in the past, which was that you should start patients on a short-acting regimen and switch them. It's much easier to get them on the right preparation as early as possible.

Multimodal therapy. Opioids are a class of medications that may be helpful for many, but not for all, patients with moderate to severe pain. When they are used, they should almost always be considered a part of a multidisciplinary or multimodal treatment for that person, especially in the treatment of chronic pain. Opioids are time-limited -- you need to monitor the patient's clinical response by seeing that patient, by following that patient, by finding out -- is the patient still using the medication? Should other treatments be considered? Is this person using the medication properly?

Opioid monitoring. This brings us to a point that I have not emphasized enough yet, which is monitoring the patient. Random urine drug screening may be important, even before you ever prescribe. If this patient tells you, "no, I don't use this, no, I've never used that," but you do a random drug screen before you prescribe and find that there happens to be opioid or cocaine metabolites or some other substance in the urine that the patient never told you about, obviously that's an important piece of history that you want to know before you prescribe to that person. Very often, people who are recreational drug users will not think that what they do is inappropriate, or they may just do it and not tell you what they do, and it's important to know to whom you're prescribing to maximize benefit and maximize safety.

Longer-acting opioids for chronic pain are preferred over shorter-acting opioids because of their ability to provide smoother, more stable blood levels of the medication. That may not necessarily improve pain relief, but it will be better for that person overall and is likely to be safer for that person.

Tamper-proof products. There are many new products, 2 of which are already available and others that are in development, that have significant enhancements in their ability to prevent crushing or changing the manner in which the drug can be used. Although that won't help everyone -- there are those who will just take a handful of pills at a time; it won't deter that kind of behavior -- it will help the person who has been crushing the medication for a use other than the medical purpose of an opioid. It will help that person not succumb to that behavior -- the less crushable the pill is, the harder it is for the drug to be misused in that form.

We really want to be able to have access to this class of medications. At the same time, an enormously important feature of prescribing opioids is prescribing them as safely and as rationally as possible.

Thank you very much.

From Medscape.com: Are Opioids Safe?

Anesthesia Awareness: Consciousness During Surgery

Dr. Orin Guidry, MUSC anesthesiologist, discusses intraoperative awareness -- the medical phenomenon commonly known as awareness under anesthesia. Dr. Guidry discusses the frequency of occurrences, gives an overview of what happens under intraoperative awareness and explains the various measures taken to decrease instances. This video is brought to you by the Medical University of South Carolina in Charleston, South Carolina.

from NEJM

Anesthesia Awareness and the Bispectral Index

Michael S. Avidan, M.B., B.Ch., Lini Zhang, M.D., Beth A. Burnside, B.A., Kevin J. Finkel, M.D., Adam C. Searleman, B.S., Jacqueline A. Selvidge, B.S., Leif Saager, M.D., Michelle S. Turner, B.S., Srikar Rao, B.A., Michael Bottros, M.D., Charles Hantler, M.D., Eric Jacobsohn, M.B., Ch.B., and Alex S. Evers, M.D.

BACKGROUND

Awareness during anesthesia is a serious complication with potential long-term psychological consequences. Use of the bispectral index (BIS), developed from a processed electroencephalogram, has been reported to decrease the incidence of anesthesia awareness when the BIS value is maintained below 60. In this trial, we sought to determine whether a BIS-based protocol is better than a protocol based on a measurement of end-tidal anesthetic gas (ETAG) for decreasing anesthesia awareness in patients at high risk for this complication.

METHODS

We randomly assigned 2000 patients to BIS-guided anesthesia (target BIS range, 40 to 60) or ETAG-guided anesthesia (target ETAG range, 0.7 to 1.3 minimum alveolar concentration [MAC]). Postoperatively, patients were assessed for anesthesia awareness at three intervals (0 to 24 hours, 24 to 72 hours, and 30 days after extubation).

RESULTS

We assessed 967 and 974 patients from the BIS and ETAG groups, respectively. Two cases of definite anesthesia awareness occurred in each group (absolute difference, 0%; 95% confidence interval [CI], −0.56 to 0.57%). The BIS value was greater than 60 in one case of definite anesthesia awareness, and the ETAG concentrations were less than 0.7 MAC in three cases. For all patients, the mean (±SD) time-averaged ETAG concentration was 0.81±0.25 MAC in the BIS group and 0.82±0.23 MAC in the ETAG group (P=0.10; 95% CI for the difference between the BIS and ETAG groups, −0.04 to 0.01 MAC).

CONCLUSIONS

We did not reproduce the results of previous studies that reported a lower incidence of anesthesia awareness with BIS monitoring, and the use of the BIS protocol was not associated with reduced administration of volatile anesthetic gases. Anesthesia awareness occurred even when BIS values and ETAG concentrations were within the target ranges. Our findings do not support routine BIS monitoring as part of standard practice. (ClinicalTrials.gov number, NCT00281489.)

N Engl J Med 2008; 358:1097-1108March 13, 2008

Preoperative Statin Therapy on Adverse Postoperative Outcomes

from Anesthesiology.org

Background: Chronic statin therapy is associated with reduced postoperative mortality. Renal and cardiovascular benefits have been described, but the effect of chronic statin therapy on postoperative adverse events has not yet been explored.

Methods: In this observational study involving 1,674 patients undergoing aortic reconstruction, we prospectively assessed chronic statin therapy compared with no statin therapy, with regard to serious outcomes, by propensity score and multivariable methods.

Results: In propensity-adjusted multivariable logistic regression (c-index: 0.83), statins were associated with an almost threefold reduction in the risk of death in patients undergoing major vascular surgery (odds ratio: 0.40; 95% CI: 0.28–0.59) and an almost twofold reduction in the risk of postoperative myocardial infarction (odds ratio: 0.52; 95% CI: 0.38–0.71). Likewise, the use of chronic statin therapy was associated with a reduced risk of postoperative stroke and renal failure. Statins did not significantly reduce the risk of pneumonia, multiple organ dysfunction syndrome, and surgical complications; however, in the case of postoperative multiple organ dysfunction syndrome (odds ratio: 0.34; 95% CI: 0.12–0.94) and surgical complications (odds ratio: 0.39; 95% CI: 0.17–0.86), reduced mortality was observed.

Conclusions: Chronic statin therapy was associated with a reduction in all cardiac and vascular outcomes after major vascular surgery. Furthermore, in major adverse events, such as multiple organ dysfunction syndrome and surgical complications, statins were also associated with decreased mortality.

"In conclusion, the observed association between chronic statin therapy and postoperative complications suggests that statins have to be considered as global perioperative protection for patients undergoing major vascular surgery and not only as cardioprotective treatment. This important observation suggests that perioperative use of statins should be guided not only by cardiac risk."

Impact of Preoperative Statin Therapy on Adverse Postoperati... : Anesthesiology

General Anesthesia: A Reversible Coma, Not Sleep

December 29, 2010 — Despite what anesthesiologists may tell surgery patients, the brain under general anesthesia is not "asleep," it is placed in a reversible drug-induced coma, according to 3 neuroscientists who reviewed and synthesized the latest research in general anesthesia, sleep, and coma.

Their review, 3 years in the making, appears in the December 30 issue of The New England Journal of Medicine.

"Anesthesiologists use the term 'sleep' so as not to scare patients with the word 'coma,' " Emery N. Brown, MD, PhD, from the Department of Anesthesia, Critical Care, and Pain Medicine at Massachusetts General Hospital and Harvard Medical School, Boston, pointed out in correspondence with Medscape Medical News. In reality, however, general anesthesia is a type of coma.

Dr. Brown's coauthors on the review are Ralph Lydic, PhD, from the University of Michigan, Ann Arbor, whose expertise is sleep medicine, and Nicholas D. Schiff, MD, from Weill Cornell Medical College in New York City, who specializes in recovery from coma.

"This review was prompted by a recognition that common brain circuit mechanisms may underlie aspects of general anesthesia and recovery from coma and that thinking through the links across these phenomena and their distinction from the natural processes of sleep would reveal important insights," Dr. Schiff told Medscape Medical News.

The realization that general anesthesia and coma have more in common with each other than differences "is very exciting," Dr. Schiff said, "because it gives us new ways to understand each of these states.

"Measuring brain circuit mechanisms may lead to greater diagnostic accuracy and targeted therapeutic strategies for predicting and supporting the recovery process from coma after severe brain injuries," he added. Monitoring brain function under general anesthesia may also help in developing new sleep aids.

Nothing Mysterious About the Anesthetized Brain

The scientists note in their article that there is substantial overlap between the electroencephalograms of patients in coma and of patients during general anesthesia. "The [electroencephalogram] of the states of coma recovery can resemble those of the awake, general anesthesia, or sleep state, depending on how extensive the brain injury is and where the patient is in terms of recovery," Dr. Brown noted.

The team also notes that anesthetic drugs induce unconsciousness or alter arousal through actions at multiple sites in the cerebral cortex, brainstem, and thalamus.

Contrary to what is commonly stated, how these drugs create the state of general anesthesia "is not mysterious," Dr. Brown explained, and "there are multiple mechanisms even for a single drug."

General anesthesia, the scientists say, is functionally equivalent to brainstem death, and perhaps explains why some patients do not fully recover consciousness for several hours after general anesthesia, as well as why postoperative cognitive dysfunction could persist in elderly patients for several months afterward.

"One thing which is evident regarding recovery from general anesthesia is that it tracks the return of function in the brainstem from bottom (respiration) to top (eye-movements and arousal centers)," Dr. Brown noted.

Dr. Brown, Dr. Lydic, and Dr. Schiff hope their article will facilitate more informed discussions among anesthesiology, sleep, and coma researchers and lead to new approaches to creating the state of general anesthesia, sedation, and sleep, as well as new approaches to facilitating coma recovery.

They hope it will also lead to better education of the public about general anesthesia.

This research was supported by the National Institutes of Health, the James S. McDonnell Foundation, Massachusetts General Hospital Department of Anesthesia, Critical Care and Pain Medicine, and University of Michigan Department of Anesthesiology.

N Engl J Med. 2010;363:2638-2650.

General Anesthesia: A Reversible Coma, Not Sleep

Codeine Linked to Increased CVD Events, Mortality

Codeine Linked to Increased CVD Events, Mortality

The researchers found that the risk for cardiovascular events was similar across opioid groups 30 days after initiation, but after 180 days of exposure it was elevated for codeine (rate ratio [RR], 1.62; 95% confidence interval [CI], 1.27 – 2.06), compared with the reference hydrocodone.

Similarly, propoxyphene showed a nonsignificant increase in cardiovascular toxicity at 30 days (RR, 1.17; 95% CI, 0.85 – 1.62), which persisted at 180 days (RR, 1.25; 95% CI, 1.00 – 1.57).

Femoral Nerve Block: Indications and Technique

A femoral nerve block is a basic nerve block technique that is easy to master, carries a low risk of complications, and has a significant clinical applicability for surgical anesthesia and post-operative pain management.

• Indications: Anterior thigh and knee surgery
• Landmarks: Femoral (inguinal) crease, femoral artery pulse
• Nerve Stimulation: Twitch of the patella (quadriceps) at 0.2-0.5 mA current
• Local anesthetic: 20 mL
• Complexity level: Basic

This block is well suited for surgery such on the anterior thigh, knee, quadriceps tendon repair, and postoperative pain management after femur and knee surgery. When combined with a block of the sciatic nerve, anesthesia of almost the entire lower extremity from the mid-thigh level can be achieved. The success rate of this block for surgery is very high, nearing 95%.

Surface Landmarks The following surface anatomy landmarks are used to determine the insertion point for the needle: Femoral crease Femoral artery
Anatomic Landmarks Landmarks for the femoral nerve block are easily recognizable in all patients and include: Femoral crease Femoral artery pulse
Needle insertion site is labeled immediately lateral to the pulse of the femoral artery. All landmarks should be outlined with a marking pen. TIPS: Note that this technique differs from common descriptions of the femoral nerve block, where the needle is inserted at the level of the inguinal ligament. Instead, in this technique the needle is inserted at the level of the femoral crease, a naturally occurring, oblique skin fold positioned a few centimeters below the inguinal ligament. The femoral crease can be accentuated in obese patients by asking an assistant to retract the lower abdomen laterally. The retraction of the abdomen should be maintained throughout the procedure to facilitate palpation of the femoral artery and block performance.

After a thorough cleaning with an antiseptic solution, local anesthetic is infiltrated subcutaneously at the estimated site of needle insertion. The injection for the skin anesthesia should be shallow and in a line extending laterally to allow for more lateral needle reinsertion when necessary.

The anesthesiologist is standing on the side of the patient with the pal-pating hand on the femoral artery. The needle is introduced immediately at the lateral border of the artery and advanced in the saggital and slightly cephalad plane.

TIP: The nerve stimulator is initially set to deliver 1.0 mA (2 Hz, 100 µsec). With proper needle position, advancement of the needle should not result in any local twitches; the first response is usually that of the femoral nerve.

from NYSORA.com

Malignant Hyperthermia: Are we becoming less suspicious?

Guidelines from the European Malignant Hyperthermia Group
K. P. E. Glahn; F. R. Ellis; P. J. Halsall; C. R. Müller; M. M. J. Snoeck; A. Urwyler; F. Wappler

Key points

• MH is rare, but its incidence may be increasing.
• Prompt recognition is the key to a safe outcome.
• These guidelines provide a template for diagnosis and treatment.
• Suspected cases and their relatives should be followed up and investigated for MH.

The first known case of malignant hyperthermia (MH) survived because the anaesthetist quickly stopped anaesthesia and surgery when he observed a set of strange clinical signs. However, he was already alerted to a potential problem because of a preoperative history of several anaesthesia-related deaths in the patient's family. The key lesson learnt from this event is as relevant today as it was back in 1960: survival from an MH crisis is highly dependent on early recognition and prompt action.

MH crises are very rare and an increasing use of total i.v. anaesthesia (TIVA) using non-triggering agents in many Western European countries is likely to make it even rarer, leading to the potential risk of reduced awareness of MH among anaesthetists and theatre staff. However, recent reports showed that the frequency of MH episodes has increased, and due to the autosomal-dominant inheritance in humans, prevalence of MH can be estimated up to 1:3000. In addition, dantrolene, the cornerstone of successful MH treatment, is unavailable in many institutions in Eastern European countries and in large areas around the world due to its cost, thereby increasing the risk of MH fatalities in these areas.

The European Malignant Hyperthermia Group (EMHG), a leading international society working on MH, has therefore decided to publish guidelines for the detection and handling of an MH crisis. Many institutions have drawn up local guidelines and most countries with an MH Investigation Unit have developed national guidelines. The EMHG Executive committee collected and reviewed all guidelines available from the various MH centres in order to provide a consensus document. It is hoped that this will be helpful, especially for countries having no MH centre and therefore no national guidelines.

While recognizing that it is impossible to stipulate the exact set-up for dealing with MH for each institution worldwide, we are, nevertheless, convinced that the EMHG guidelines will provide a sound basis to help anaesthetists and theatre staff in Europe and around the world ensure that best practice is followed and enable them to plan ahead.

The guidelines consist of two textboxes: Box 1 on recognizing MH and Box 2 on the treatment of an MH crisis.

Box 1 EMHG Guidelines: Recognizing an MH crisis

Early recognition of an impending MH crisis and its immediate treatment is essential for the patient's survival. As the clinical signs associated with MH are not unique, anaesthetists must be able to recognize a pattern of signs in order to make a rapid diagnosis.

Any patient may develop MH during or shortly after an anaesthetic where trigger agents are used—this can occur even in patients who have had uneventful general anaesthesia previously.

Trigger agents are

• all volatile (inhalation) anaesthetic agents;
• succinylcholine.

Clinical signs

Early signs

• Metabolic
  
  • Inappropriately elevated CO₂ production (raised end-tidal CO₂ on capnography, tachypnoea if breathing spontaneously).
  • Increased O₂ consumption.
  • Mixed metabolic and respiratory acidosis.
  • Profuse sweating.
  • Mottling of skin.
• Cardiovascular
  
  • Inappropriate tachycardia.
  • Cardiac arrhythmias (especially ectopic ventricular beats and ventricular bigemini).
  • Unstable arterial pressure.
• Muscle
  
  • Masseter spasm if succinylcholine has been used.
  • Generalized muscle rigidity.

Later signs

• Hyperkalaemia.
• Rapid increase in core body temperature.
• Grossly elevated blood creatine phosphokinase levels.
• Grossly elevated blood myoglobin levels.
• Dark-coloured urine due to myoglobinuria.
• Severe cardiac arrhythmias and cardiac arrest.
• Disseminated intravascular coagulation.

Differential diagnosis

• Insufficient anaesthesia, analgesia, or both.
• Infection or septicaemia.
• Insufficient ventilation or fresh gas flow.
• Anaesthetic machine malfunction.
• Anaphylactic reaction.
• Phaeochromocytoma.
• Thyroid crisis.
• Cerebral ischaemia.
• Neuromuscular disorders.
• Elevated end-tidal CO₂ due to laparoscopic surgery.
• Ecstasy or other dangerous recreational drugs.
• Malignant neuroleptic syndrome.

Box 2 EMHG Guidelines: Managing an MH Crisis

Start treatment as soon as an MH crisis is suspected.

The clinical presentation of MH varies and treatment should be modified accordingly.

Treatment

• Immediately
  
  • Stop all trigger agents.
  • Hyperventilate (use a minute volume 2–3 times normal) with 100% O₂ at high flow.
  • Declare an emergency and call for help.
  • Change to non-trigger anaesthesia (TIVA).
  • Inform the surgeon and ask for termination/postponement of surgery.
  • Disconnect the vaporizer—do not waste time changing the circuit/anaesthetic machine.
• Dantrolene
  
  • Give dantrolene 2 mg kg⁻¹ i.v. (ampoules of 20 mg are mixed with 60 ml sterile water).
  • Obtain dantrolene from other sources, for example, pharmacy/nearby hospitals—at least 36–50 ampoules may be needed for an adult patient.
  • Dantrolene infusions should be repeated until the cardiac and respiratory systems stabilize.
  • The maximum dose (10 mg kg⁻¹) may need to be exceeded.
• Monitoring
  
  • Continue routine anaesthetic monitoring (Sa_o2, ECG, NIAP, e′_co2).
  • Measure core temperature.
  • Establish good i.v. lines with wide-bore cannulas.
  • Consider inserting an arterial and central venous line, and a urinary catheter.
  • Obtain samples for measurement of K⁺, CK, arterial blood gases, myoglobin, and glucose.
  • Check renal and hepatic function and coagulation.
  • Check for signs of compartment syndrome.
  • Monitor the patient for a minimum of 24 h (ICU, HDU, or in a recovery unit).

Symptomatic treatment

• Treat hyperthermia
  
  • 2000–3000 ml of chilled (4°C) 0.9% saline at i.v.
  • Surface cooling: wet, cold sheets, fans, and ice packs placed in the axillae and groin.
  • Other cooling devices if available.
  • Stop cooling once temperature <38.5°C
• Treat hyperkalaemia
  
  • Dextrose: 50%, 50 ml with 50 IU insulin (adult dose).
  • CaCl₂: 0.1 mmol kg⁻¹ i.v. (e.g. 7 mmol=10 ml for a 70 kg adult).
  • Dialysis may be required.
• Treat acidosis
  
  • Hyperventilate to normocapnoea.
  • Give sodium bicarbonate i.v. if pH < 7.2.
• Treat arrhythmias
  
  • Amiodarone: 300 mg for an adult (3 mg kg⁻¹ i.v.).
  • β-blockers (e.g. propranolol/metoprolol/esmolol)—if tachycardia persists.
• Maintain urinary output >2 ml kg⁻¹ h⁻¹
  
  • Furosemide 0.5–1 mg kg⁻¹.
  • Mannitol 1 g kg⁻¹.
  • Fluids: crystalloids (e.g. lactated Ringer's solution or 0.9% saline) i.v.

Consult your local Malignant Hyperthermia Investigation Unit about the case

Patients suspected of being MH-susceptible should undergo diagnostic testing using in vitro contracture testing (IVCT) at a designated MH-laboratory (www.emhg.org).

Action cards adapted for local conditions and resources can be extremely helpful in dealing with an MH crisis. Such a system, designed by the Australian and New Zealand MH group (MHANZ), has proved to be a success in full-scale simulation and can save valuable time.

It is important that once a case of MH is suspected, either because of a full-blown MH crisis or a set of symptoms suggestive of MH which resolved on stopping any trigger agents, the patient and their relatives should always be referred to a regional or national MH centre for further investigation wherever possible. The EMHG has previously published guidelines for diagnosing MH susceptibility using the IVCT test and genetic testing when indicated.

source: Br J Anaesth. 2010;105(4):417-420.