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Friday, November 06, 2015
  •  All anesthetic drugs except ketamine are given on a per body weight basis.
  •  It was consistently observed for more than 23 years in more than 6,000 patients that 100-pound women and 250-pound men alike remain motionless (dissociated) with the same 50 mg ketamine IV two minutes prior to skin injection of local anesthesia.
  •  The ketamine dissociative effect, primarily at midbrain NMDA receptors, requires 98-99% saturation prior to stimulation.
  •  Midbrain size is unrelated to body weight.
  •  N.B. Precede with IV glycopyrrolate (preferred over atropine) to prevent ketamine salivation. It has less tachycardia.
  •  Ketamine side effects (i.e., emergence hallucinations, dysphoria, and intra-op hypertension, tachycardia) are prevented with a stable cerebral cortical level of propofol.
  •  Create a stable level with incremental, not bolus, propofol induction. Watch a video of this at
  •  Prescribe 50 mcg  kg-1 propofol repeated to loss of lid reflex c 25 mcg kg-1 basal infusion, increase or decrease prn to 60 <BIS <75 c baseline EMG as clinical picture dictates.
  •  Titration typically requires about two minutes. This results in cardiovascular and respiratory stability with blood pressure and airway maintained.
  •  Masseter tone typically remains intact with patent airway. Intervene if needed.
  •  Immediately after induction, give 50 mg IV ketamine, and wait two minutes.
  •  Inject skin prior to incision with 0.5% lidocaine c epinephrine.
  •  If movement occurs, wait an additional minute, and try again. If movement continues, re-bolus an additional 50 mg ketamine.
  •  Define 98-99% NMDA saturation with non-response to skin incision injection.
  •  Instill, not inject, 10-20 cc 0.25% bupivacaine in wound prior to closure.
  •  In event of cough or sneeze, bolus IV lidocaine 1 mg/pound to prevent laryngospasm. No high-pitched crowing noise is generally heard.

Thursday, September 24, 2015
By Leon Gussow, MD

It’s not your father’s anion gap anymore.


Back when I was starting out in emergency medicine and toxicology, the differential diagnosis for an increased anion gap was fairly simple. The mnemonic was MUDPILES: Methanol, Uremia, Diabetic ketoacidosis (or alcoholic ketoacidosis,) Paraldehyde, Iron (or Isoniazid,) Lactic acidosis, Ethylene glycol, and Salicylates.


Recent evidence indicates that this mnemonic is no longer adequate because it misses a number of important toxicological causes. New laboratory technology and methods of measuring electrolytes also have resulted in a change of what’s considered a normal anion gap.


A normal value for the anion gap is now lower than in the past. The law of electroneutrality states that the positive charges (cations) in a system such as the serum must equal the negative charges (anions). Because the number of positive charges typically measured on routine lab testing is larger than the number of negative charges, the difference is called the anion gap. The formula for calculating this is anion gap = [Na+] - [Cl- + HCO3-].


Originally, a normal value was considered 12 + 4 mEq/L. Winter and Pearson et al. studied serum from healthy volunteers and blood donors, however, and determined a reference range between 3 and 11 mEq/L, with most subjects having an anion gap less than 6. (Arch Intern Med 1990;150[2]:311.) We routinely look at the anion gap to determine whether there is a clinically significant metabolic acidosis. I still use a gap of 15 mEq/L as my cutoff for that purpose while realizing that a lower number does not rule out mild metabolic acidosis.


APAP Overdose

Massive acetaminophen (APAP) overdose can cause a high-anion gap metabolic acidosis. This is an important point that some clinicians, still wedded to the old MUDPILES mnemonic, do not yet realize. The toxic acetaminophen metabolite NAPQI in massive APAP overdose impairs mitochondrial function, impairing oxidative phosphorylation in a manner similar to that of cyanide. This occurs early, within four to six hours after ingestion, long before hepatic failure sets in.


Recent recommendations from the Extracorporeal Treatment in Poisoning Workgroup ( suggest that an early metabolic acidosis with altered mental status and a level greater than 900 mcg/mL is an indication for hemodialysis in an acute acetaminophen overdose. (Clin Toxicol (Phila) 2014;52[8]:856.) A mnemonic for causes of high-anion gap metabolic acidosis that does not include acetaminophen is grossly inadequate.



Propylene glycol can also cause lactic acidosis. It is used as a diluent in a number of intravenous medications. Propylene glycol is metabolized in the liver to lactic acid, so a large-dose infusion of these medications can cause a high-anion gap lactic acidosis, especially in patients with renal dysfunction. Associated manifestations include neurotoxicity, ECG changes, and increased osmolarity. Common intravenous medications that contain propylene glycol include lorazepam, diazepam, digoxin, phenobarbital, and phenytoin.


Ibuprofen overdose also can cause high-anion gap metabolic acidosis. The number of reported overdose cases has increased dramatically since over-the-counter ibuprofen became available in 1984. Fortunately, most of these cases involve only mild toxicity and resolve with supportive care. Massive ibuprofen overdose can cause severe toxicity, however, with manifestations that include coma, hypothermia, hypotension, seizures, acute renal failure, and, rarely, death despite aggressive supportive care.


Metabolic Acidosis

High-anion gap metabolic acidosis can also occur. This results from a combination of lactic acidosis and accumulation of exogenous acids consisting of ibuprofen and its metabolites. Treatment is generally supportive. Ibuprofen is highly protein-bound, so hemodialysis would not be expected to increase elimination significantly, but may be indicated to help correct severe acidosis.


Following changes in the anion gap can replace arterial blood gas tests for monitoring progression of metabolic acidosis. Many clinicians will perform an arterial puncture to determine whether acidosis from a known cause such as ethylene glycol poisoning is getting worse or resolving. This is completely unnecessary and unwise, given the discomfort and risk of arterial injury, though admittedly slight. A simple venipuncture for basic electrolytes will allow calculation of the anion gap, which will indicate trends and reflect whether metabolic acidosis is worsening or resolving.


Clearly, MUDPILES is no longer adequate as a memory aid for recalling the complete differential diagnosis for a high-anion-gap metabolic acidosis. We need an expanded version. The best one I’ve seen is A CAT MUDPILE. (See table.)


Speaking of mnemonics, I thought I’d pass along my favorite of them all. See if you can determine what it represents: Frank Sinatra Takes Four Fifths Seagram’s Seven Each Night To Ease Tension. The answer is at the bottom of the table.


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Wednesday, September 23, 2015

The predicted heart age among U.S. adults is significantly higher than their chronological age, said researchers who linked that figure to race and geography. (MMWR 2015;64[34]:950.)


Researchers used weighted 2011 and 2013 Behavioral Risk Factor Surveillance System data and applied it to the sex-specific, non-laboratory-based Framingham risk score models. They layered results by age and race/ethnic group, educational and income levels, and state of residence, and then translated the results into age-standardized heart age values. Once they calculated the mean excess heart age, they compared the findings across groups.


The average predicted heart age for men and women was 7.8 and 5.4 years older than their chronological age, respectively. The heart age among non-Hispanic black men (58.7 years) and women (58.9 years) was greater than other racial/ethnic groups, including non-Hispanic white men (55.3 years) and women (52.5 years).


Excess heart age was lowest for men and women in Utah (5.8 and 2.8 years, respectively) and highest in Mississippi (10.1 and 9.1 years, respectively). It also increased with age and decreased as education and household income increased. The prevalence of excess heart age less than five years was 48.8 percent among men and 38.5 percent among women. Among both sexes, prevalence was higher among blacks compared with whites, increased with age, and decreased with greater education and household income.


The authors of the study suggest that use of heart age might simplify risk communication and motivate more individuals, especially the younger crowd, to adopt healthier lifestyles and better comply with recommended therapeutic interventions to prevent heart disease and stroke.


Read more results:


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Tuesday, September 22, 2015

The association between ED crowding and ED length of stay (LOS) for trauma patients was not statistically significant, and ED LOS was associated with hospital capacity, according to a study published in the Journal of Hospital Administration. (


Researchers conducted a retrospective database review of 1,207 Level 1 and 2 patients at a Midwest Level I trauma center over a year. Approximately two-thirds of patients (807 of 1,207) had a short ED LOS, and there was no difference in the mortality rates between short (4.8%) and long (4.0%) ED LOS groups.


Length of stay has become an important quality indicator for emergency departments because it measures patient flow from arrival to disposition. Increased LOS, according to the study, has been linked to poor patient satisfaction and crowding, and may be associated with adverse outcomes. The Centers for Medicare and Medicaid Services (CMS) began collecting data on crowding and patient flow in 2012, generating much interest in finding associations among ED throughput measures and clinical outcomes.


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Monday, September 21, 2015

Pulmonary embolisms (PE) identified by pulmonary CT angiography (CTA) are often overdiagnosed when compared with the overall opinion of chest radiologist experts, according to a study published in American Journal of Roentgenology. (


The study was a retrospective review of 937 pulmonary CTA exams performed in a tertiary care university hospital over one year, and studies originally reported as positive for PE were reinterpreted by three chest radiologists with more than a decade of experience.


Pulmonary CTA was considered negative for PE when all three chest radiologists were in agreement that the pulmonary CTA study was negative for PE. PE was diagnosed in the initial report in 174 of these cases (18.6%). There were disagreements among the chest radiologists and the original radiologist in 45 (25.9%) cases. Discordance occurred more often where the original reported PE was solitary (46.2% of reported solitary PEs were considered negative on retrospective review) and located in a segmental or subsegmental pulmonary artery (26.8% of segmental and 59.4% of subsegmental PE diagnoses were considered negative on retrospective review).


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About the Author

Alissa Katz
Assistant Editor