icuroom.net August 2007 Archive

2007-08-31T17:52:00.000-07:00

Friday August 31, 2007
Cefepime in CVVHD

Q; Do you need to adjust Cefepime in CVVHD. Yes OR No ?

A: No

Cefepime is dialysable. In patients on CVVHD (Continuous venovenous haemodiafiltration), no dosage adjustment for cefepime is required and the dosage regime as with normal renal function should be administered.In patients on HD (hemodialysis), dose of 1 gram every 24 hours is recommended. A supplemental dose of cefepime is advisable at the end of a HD session due to the fact that cefepime is dialysable.

Related previous pearl: Vancomycin dosing in CRRT

2007-08-30T12:39:00.000-07:00

Thursday August 30, 2007
Calculating Base Excess

Q: Usually all new machines provide Base Excess/deficit automatically along with ABG. Supposedly you have a situation where ABG (arterial blood gas) is not available and due to some reason (like severe coagulopathy), you are not willing to do arterial punture, what is the formula to calculate Base Excess or Base Deficit?

A: Obtain HCO3 and PH from venous blood and apply following formula

B.E. = 0.9287 (HCO3 - 24.4 + 14.83 (pH - 7.4))

Or to roundup

B.E. = (HCO3 - 24 + 15 (PH - 7.4)

Base Excess is defined as the negative value of the concentration of titratable hydrogen ion in blood or plasma. The endpoint of titration is pH = 7.40. It also helps in determining the amount of bicarbonate immediately required for replacement with following formula

mEq of NaHCO3 needed = 0.1 or 0.2 × (BW in Kg) × (BE)

1 amp of bicarb. carries 50 mEq of NaHCO3

2007-08-29T09:30:00.000-07:00

Wednesday August 29, 2007
Are you pressing chest right? - bench to bedside

A very interesting article published recently in chest 1 evaluating the quality of chest compressions during CPR (Cardiopulmonary Resuscitation).

Methods: Ventricular fibrillation was induced (by occlusion of the left anterior descending coronary artery) in 24 pigs. Cardiac arrest was left untreated for 5 min. A total of four randomized groups of animals were investigated.

Animals who receive "conventional" chest compressions first than defibrillation.
Animals who receive "optimal" chest compressions first than defibrillation.
Animals who receive defibrillation first than "conventional" chest compressions.
Animals who receive defibrillation first than "optimal" chest compressions.

Postresuscitation myocardial function was echocardiographically assessed.

Results:

Coronary perfusion pressures and end-tidal PCO2 were significantly lower with conventional chest compressions.
With optimal chest compressions, either as an initial intervention or after defibrillation, each animal was successfully resuscitated.
Fewer shocks were required prior to the return of spontaneous circulation after initial optimal chest compressions.
No animals were resuscitated when conventional chest compressions preceded the defibrillation attempt.
When defibrillation was attempted as the initial intervention followed by conventional chest compressions, two of six animals were resuscitated.

Conclusions: In this animal model of cardiac arrest, it was the quality of the chest compressions, rather then the priority of either initial defibrillation or initial chest compressions, that was the predominant determinant of successful resuscitation.

Please refer to full article for Animal Preparation, Measurements, Statistical Analysis, Graphs, Tables and Discussion.

Reference: click to get abstract/article

The Quality of Chest Compressions During Cardiopulmonary Resuscitation Overrides Importance of Timing of Defibrillation - Chest. 2007; 132:70-75

2007-08-28T12:14:00.000-07:00

Tuesday August 28, 2007
Is fresh blood better ?

In a poster presentation (Dr. Hussam Jenad) at the International Conference of the American Thoracic Society, results have been presented of a study span over 10 years including 12,264 patients (total median transfusion of 4 pRBC units). Study was done at Mayo Clinic, Rochester, MN. It was found that

adjusted in-hospital mortality was 5% if pRBC was stored for less than 7 days
adjusted in-hospital mortality was 8% if pRBC was stored for 7-14 days
adjusted in-hospital mortality was 13% if pRBC was stored for more than 14 days

This corresponds to a reduction in the risk of in-hospital mortality of 62% for patients receiving pRBC stored for less than 7 days.

Reference:

ATS 2007 poster presentations: The 2007 International Conference Abstracts of the American Thoracic Society (ATS) are published in the American Journal of Respiratory and Critical Care Medicine, Volume 175, Abstracts Issue, April 2007.

2007-08-27T05:50:00.000-07:00

Monday August 27, 2007
Amiodarone induced optic neuritis !

Amiodarone is one of the most commonly used medicine in ICU. In past, we have done many pearls related to IV amiodarone.

One of the other unusual and common presentation of Amiodarone toxicity is optic neuritis. Optic neuritis may occur at any time following initiation of therapy. If any symptoms of visual impairment appear, like change in visual acuity or decrease in peripheral vision, prompt ophthalmic consult is recommended.

Related previous pearls:

Why we call it Am-iod-arone

Amiodarone Neurotoxicity !

Amiodarone induced phlebitis

Etiology of Hypotension from intravenous Amiodarone

References: Click to get abstract/article

1. Cordarone from rxlist.com

2007-08-26T18:51:00.000-07:00

Sunday August 26, 2007
Hypercapnia - Bench to bedside !

In this month of 'Critical Care Medicine' (September 2007) 1, an interesting lab study published from Japan, evaluating the permissive range of Paco2. Study examined how Paco2 affects microvascular changes, hemodynamics, and cardiac output in rabbits.

Background: Permissive hypercapnia is a potent vasoactive stimulus, adequate tissue perfusion and oxygen delivery to dilated microvessels may be restored. Diffusion of CO2 to tissues may alter intracellular or extracellular hydrogen-ion concentrations, influencing calcium channels. An indirect action of CO2 is activation of the sympathetic nervous and adrenal systems.

Method: A total of 31 white rabbits were anesthetized with pentobarbital. An ear chamber was prepared to examine blood vessels by intravital microscopy. The rabbits were mechanically ventilated with air, oxygen, and CO2. The values of Paco2 were adjusted to about 20 (hypocapnia), 40, 60, 80, 100, 125, 150, and above 250 mm Hg. After stabilization at each Paco2 level, microvascular changes were recorded with a microscope-closed video camera to permit analysis of arteriolar diameter and blood flow.

Results:

The pH and heart rate decreased and mean blood pressure increased progressively as the Paco2 was increased.
When Paco2 was increased from 20 to 80 mm Hg, vessel diameter, blood-flow velocity, and blood-flow rate increased markedly. Cardiac output increased slightly.
When Paco2 exceeded 100 mm Hg, all of these variables decreased.
When Paco2 exceeded 150 mm Hg, all variables were significantly lower than the control values.

Reference: Click to get abstract/article

1. Permissive range of hypercapnia for improved peripheral microcirculation and cardiac output in rabbits - Critical Care Medicine. 35(9):2171-2175, September 2007.

2007-08-25T10:27:00.000-07:00

Saturday August 25, 2007
Hemodialysis in Salicylate overdose with normal level

Hemodialysis is recommended in salicylate overdose patients with a level at or above 100 mg/dL (cut it to half if history suggest chronic ingestion). But if there is any sign of neurological manifestation, dialysis is indicated despite normal level.

Salicylate cause "neuroglycopenia" (lower CNS glucose level) despite normal serum glucose. As patient gets more and more acidotic, salicylate enters CNS and by direct effect cause neuroglycopenia. 7 indications of Hemodialysis in Salicylate poisoning

Mental status change
Pulmonary edema
Cerebral edema
Associated or with renal failure
Level at or above 100 mg/dL(half if chronic ingestion)
If fluid overload prevents alkalinization
Patient continue to deteriorate clinically

References: Click to get abstract/article

1. Toxicity, Salicylate - emedicine.com

2.An evidence based flowchart to guide the management of acute salicylate (aspirin) overdose -Emerg Med J 2002; 19:206-209

3. Salicylic acid - intox.org

2007-08-24T00:27:00.000-07:00

Friday August 24, 2007

Q; Zofran (Ondansetron Hydrochloride) is relatively a safe medicine for symptomatic treatment for nausea but it may cause which electrolyte abnormality ?

A: Zofran may cause hypokalemia.

On side note, this may be of interest to know that data support the efficacy of this drug in the prevention of nausea and vomiting rather in the rescue of nausea and vomiting !!

2007-08-23T08:25:00.000-07:00

Thursday August 23, 2007
C-difficile and probiotic drink

Continuing our theme from yesterday on C.diff.,

The incidence and severity of the C-difficile infections has significantly increased and sometimes it becomes difficult to eradicate the infection by available therapies.

C-difficile diarrhea can be prevented by the consumption of a probiotic drink containing L casei, L bulgaricus, and S thermophilus can reduce the incidence of antibiotic associated diarrhoea and C difficile associated diarrhoea. This has the potential to decrease morbidity, healthcare costs, and mortality if used routinely in patients aged over 50.

References: click to get abstract

1. Use of probiotic Lactobacillus preparation to prevent diarrhoea associated with antibiotics: randomised double blind placebo controlled trial - BMJ. 2007 Jul 14;335(7610):80. Epub 2007 Jun 29

2. Effect of Lactobacillus rhamnosus GG in Persistent Diarrhea in Indian Children: A Randomized Controlled Trial - J Clin Gastroenterol.2007 Sep;41(8):756-60

2007-08-22T11:23:00.000-07:00

Wednesday August 22, 2007
Writing orders to check stool for C. diff.

Whenever Clostridium difficile is suspected in a patient, send 2 or 3 samples apart to check for toxins. There are different methods / kits to check for C. diff. toxins in stool and many test kits have lower sensitivity. Sending multiple samples enhance the sensitivity of results.OR request to run stool for both Toxin A and B of clostridium difficile.If stool test continue to remains negative despite high clinical suspicion, ask specifically for culture of Clostridium difficile. The organism does not grow on standard media and thus the laboratory must be informed that Clostridium difficile is suspected.

Remember ! Alcohol doen't kill C.diff. spores so washing with soap and water should be done after examining patient with C. Diff.

Related previous pearls:

Stool donation as C. Diff treatment

Fluoroquinolone induce strain of C. Diff.

2007-08-21T17:48:00.000-07:00

Tuesday August 21, 2007
How many attempts to intubate?

Its hard to give up procedure if you are failing it !!. For intubation, ASA (American Society of Anesthesiologists) recommends to limit laryngoscopic attempts to three. Dr. Thomas C. Mort from Hartford Hospital, CT entered 2833 Critically-ill patients, suffering from cardiovascular, pulmonary, metabolic, neurologic, or trauma-related deterioration into an emergency intubation quality improvement database. Data confirmed that the number of laryngoscopic attempts were directly proportional with the incidence of airway and hemodynamic adverse events (more than 2 attempts).

incidence of hypoxemia went from 11.8% to 70%,
incidence of regurgitation of gastric contents went from 1.9% to 22%,
incidence of aspiration of gastric contents went from 0.8% to 13%,
incidence of bradycardia went from 1.6% to 21%, and
incidence of cardiac arrest went from 0.7% to 11%

Call for help !! and remember, to limit intubation attempts to 3, unless untill you are trained to deal with 'difficult intubations'.

References: click to get abstract/article

1. Emergency tracheal intubation: complications associated with repeated laryngoscopic attempts - Anesth Analg 2004;99:607-613

2007-08-20T16:20:00.000-07:00

Monday August 20, 2007
CR-BSIs

One of the parameter or measurement of ICU is the decreasing rate of CR-BSIs. (Central line catheter-related bloodstream infections). CR-BSIs are calculated or presented usually per 1000 central line-days. The formula for the CR-BSI

Rate per 1000 catheter days is: Total no. of CR-BSI cases / No. of catheter days x 1000 = CR-BSI rate per 1000 catheter days

For example: In a given month, you had 100 central lines in your ICU and each stayed there for 4 days. Your total no. of catheter days are 100 X 4 = 400 days. Now you confirmed 15 cases of CR-BSIs. The CR-BSI Rate per 1000 catheter days in your ICU for that given month is 15 / 400 x 1000 = 37.5

On average per IHI report approximately 5.3 catheter-related bloodstream infections occur per 1,000 catheter days in ICUs. Goal should be to keep this number atleast below average for ICU.

Bonus Pearl: As against common belief, application of ointment at catheter insertion site does not decrease the infection rate. Actually application of antibiotic ointments (e.g., bacitracin) to catheter-insertion sites increases the rate of catheter colonization by fungi and promotes the emergence of antibiotic-resistant bacteria.

Recommended Reading:

Preventing Complications of Central Venous Catheterization, David C. McGee, M.D.,, NEJM, March 03, Volume 348:1123-1133.

2007-08-19T17:21:00.000-07:00

Sunday August 19, 2007
Indian Journal of Critical Care Medicine

Every Sunday, we go off-beat and try to introduce web related activities to Critical Care Medicine. One open access publication in this regard is

Indian Journal of Critical Care Medicine

Indian Journal of Critical Care Medicine is published under Indian Society of Critical Care Medicine. It contains very high quality research, education and clinical articles.

It provides a very good peek into practice of Critical Care Medicine in developing countries. The most rewarding part of this journal from this perspective is section of case reports, like

Brachial plexus palsy due to subclavian artery pseudo aneurysm from internal jugular cannulation

or review article on subjects seldom seen and described in western countries:

Acute ingestion of copper sulphate: A review on its clinical manifestations and management

2007-08-18T08:11:00.000-07:00

Saturday August 18, 2007

Case: You have been called to 'code blue' with patient in PEA (pulseless electrical activity). You tried rounds of epinephrine and atropine beside IVF wide open, without any success. While in that chaos you heard 2 suggestions - one for 'soda-bicarb' and other for 'calcium chloride'. You decide to try both !. What would be other advise you will give with order ?

Answer: First of all calcium is not recommended in PEA unless there is a specific indication like evidence or suspicion of hyperkalemia (as in renal failure patients) or hypocalcemia or calcium channel-blocker overdose. It may have potential serious complications 1.

Also, routine administration of sodium bicarbonate is discouraged because it worsens intracellular and intracerebral acidosis and failed to show any improvement in mortality rate. It should be reseved for patients with severe systemic acidosis, hyperkalemia, or a tricyclic antidepressant overdose.

In case, for above reasons, if you decide to use both sodium bicarbonate and calcium - Give order with advise - "Use different lines for both". It's a simple chemistry. NaHCO3 and CaCl in the same line will form together CaCO3. Also, it is advisable to give soda-bicarb before calcium to avoid above reaction and to avail the benefit of soda-bicarb and once utilized, give calcium.

Related previous pearls: Calcium in Dig toxicity and In Hyperkalemia !!

Reference:

1. Critical Care Medicine: The Essentials - Marini and Wheeler, Page 335

2007-08-17T00:49:00.000-07:00

Friday August 17, 2007
Viagra in acute pulmonary hypertension

The treatment of pulmonary hypertension remains very challenging due to multifactorial and multidimensional nature of disease as well as the side effects of therapeutic agents.

Understanding the mechanism of action: The vascular endothelium produces nitric oxide that diffuses into the vascular smooth muscle cells, where it binds to and activates guanylate cyclase, causing smooth muscle relaxation. The action of cGMP is terminated by phosphodiesterase (PDE), which converts cGMP to the inactive 5-GMP. It is postulated that PDE inhibitors such as milrinone should be capable of affecting vasodilatation by prolonging the action of cGMP.

Why Sildenafil (Viagra): At least 11 isoenzymes of PDE have been identified. The specificity of sildenafil for PDE type 5 is known to produce vasodilatation in the penile corpus cavernosum (for which it is well known). Because PDE type 5 is also found in high concentrations in the lung, sildenafil is also postulated as a treatment for pulmonary hypertension by causing pulmonary vasodilatation. Sildenafil is also said to ameliorates effects of inhaled nitric oxide withdrawal.

Note: Viagra is marketed with name "Revatio" to avoid possible embarrassment for patients with pulmnary hypertension at pharmacy counter.

references: click to get abstract/article

1. Sildenafil for Pulmonary Hypertension - The Annals of Pharmacotherapy: Vol. 39, No. 5, pp. 869-884

2. Sildenafil—a possible treatment for acute pulmonary hypertension during cardiac surgery - Proc (Bayl Univ Med Cent). 2002 January; 15(1): 13–15

3. Sildenafil in primary pulmonary hypertension. N Engl J Med. 2000;343:1342

4. Therapy of pulmonary hypertension: targeting pathogenic mechanisms with selective treatment delivery -Crit Care Med. 2001;29:1086–1087

2007-08-16T09:55:00.000-07:00

Thursday August 16, 2007
Keppra (Levetiracetam) and renal failure

Keppra (Levetiracetam), an anti-epileptic drug is now available in IV form and is frequently used in ICU. Its important to remember that Keppra metabolized through kidney and dose needs to be reduced in renal insufficiency by 50%. Also keppra is dialyzable and ideally should be given after dialysis on dialysis day.

Unfortunately, there is no test available to measure therapeutic blood levels.

2007-08-15T10:45:00.000-07:00

Wednesday August 15, 2007
myasthenia gravis - Bedside tip !

Patients with myasthenia gravis (MG) crisis are frequently admitted under ICU care. One important bedside tip to remember is: Iodinated IV contrast is associated with further exacerbation of MG, and should be avoided if possible.

Related previous pearl: "Ice test" - Poor man's test for Myasthenia Gravis

Reference: click to get abstract/article

1. Iodinated contrast agents in myasthenia gravis, Neurology.1987; 37: 1400

2007-08-14T09:04:00.000-07:00

Today's ICU Pearl
Tuesday August 14, 2007

CPR on patient with IABP If patient requires CPR who is on Intra-Aortic Baloon Pump (IABP) - do not switch off IABP. Switch from "ECG trigger" to "Pressure trigger". IABP during CPR improves cerebral and cardiac blood flow. With CPR, on "pressure trigger", an arterial pressure tracing should be generated on console/screen and if the console is not recognising the arterial pressure tracing, chest compressions may not be adequate. (If feels uncomfortable regarding IABP during code - just put IABP to 'standby' mode during code).

Related: IABP care protocol - (source: London Health Sciences Centre, Canada)

Further Reading:

P. J Overwalder: Intra Aortic Balloon Pump (IABP) Counterpulsation . The Internet Journal of Thoracic and Cardiovascular Surgery. 1999. Volume 2 Number

2007-08-13T15:59:00.000-07:00

Monday August 13, 2007
Ischemia Modified Albumin (IMA)

When we look at the standard coronary disease predictors (Troponin-I & CK-MB) we are looking at values that reflect necrosis. In one small study the use of IMA along with Myoglobin, CK-MB, & Troponin-I increased the sensativity of detecting an ischemic event to 97% with a negative predictive value of 92%. Similar other reports in literature are also posing for this test to be an integral part of cardiac events in future (see references).

Above pearl contributed from:

Ken Davis at Eastern New Mexico University - Roswell (DAVISKE@roswell.enmu.edu)

References: click to get abstract/article

1. Role of "Ischemia Modified Albumin", a new biochemical marker of myocardial ischaemia, in the early diagnosis of acute coronary syndromes - Emerg Med J 2004; 21:29-34
2. Ischemia-Modified Albumin and Myocardial Ischemia - Kalay et al. J Am Coll Cardiol.2007; 49: 2375
3. Utility of admission cardiac troponin and "Ischemia Modified Albumin" measurements for rapid evaluation and rule out of suspected acute myocardial infarction in the emergency department - Emergency Medicine Journal 2006;23:256-261
4. "Ischemia modified albumin": a new biochemical marker of myocardial ischaemia Emerg Med J.2004; 21: 3-4
5. "Ischemia modified albumin" from thedoctorsdoctor.com

2007-08-12T13:38:00.000-07:00

Sunday August 12, 2007
icumedicus

This website should be a bookmark for all intensivists.

www.icumedicus.com

Interesting features of site include

2007-08-10T21:05:00.000-07:00

Saturday August 11, 2007
Blue dye in tube feedings

Although initially thought to be without risk and a reasonable indicator of aspiration, the nutritional support community advises AGAINST putting blue dye into tube feeds. Blue dye was thought to be non-absorbable, non-toxic, and sensitive for aspiration. However, now it is hypothesized that blue dye can be absorbed systemically due to increased intestinal permeability and that it can cause decreased mitochondrial oxygen consumption and mitochondrial toxicity.

ASPEN (American Society of Parenteral and Enteral Nutrition) recommends against the use of blue dye in tube feeds. The reasons include:

● The reliability and validity have not been adequately tested.
● There have been reports of skin and body organ staining.
● No safe amount of dye has been established.

Since blue dye is NOT recommended to routinely detect aspiration, prevention is the best treatment. Prevention may include:

● Adjusting rate of administration based on tolerance, bowel sounds, and residuals.
● Elevating the head of bed 45 degrees or more.
● Pro-motility agents.

References: click to get abstract/article

1. Use of Colored Dyes in Enteral Formulas. REVIEW ARTICLE - Topics in Clinical Nutrition. 21(3):226-233, July/September 2006
2. Systemic absorption of food dye in patients with sepsis. N Engl J Med 2000;343(14):1046-7.
3. Skin discoloration with blue food coloring. Ann Pharmacother 2000;34:868-70.
4. Evidence-based practice for enteral feedins:aspiration prevention strategies, bedside detection, and practice changes. Medsurg Nurs 2000;9(1):27-31.

2007-08-10T06:01:00.001-07:00

Friday August 10, 2007
Insulin in TPN

Adding insulin to the TPN bag itself - this is chemically compatible and has been done for years. The debate comes in when we start to discuss how much actually makes it to the patient. Study results have been variable. The amount of insulin adsorbed (i.e. stuck to) the glass bottle, plastic bag, or plastic IV tubing can be as high as 80%. Some factors affecting this adsorption include type of container, solution, administration set, previous exposure of tubing to insulin, etc. The binding appears to happen within the first 30-60 minutes. Some in vitro studies have been conducted to assess the effect of "priming" the line with a dilute insulin solution. Priming the tubing with a dilute solution or running through and wasting the first aliquot of the insulin-containing solution increases delivery of insulin from 38% to 85% at 2 hours. Once the priming is done, the amount of insulin delivered remains pretty constant.

Other options - although costly and controversial, adding albumin in small concentrations may help deliver higher amount of insulin by decreasing the amount of insulin available to bind to the container and/or tubing. Adding 0.3 gram/100ml seems to decrease adsorption. Flushing the tubing with the insulin-containing solution two hours before administration seems to saturate the binding sites and minimizes further adsorption. Giving the insulin as a separate IV infusion is another delivery option but adsorption should be considered in this setup as well.

2007-08-08T21:10:00.000-07:00

Thursday August 9, 2007
Choice of IVF in Thyroid storm

In Thyroid storm, solutions that contain dextrose (some experts recommend even 10% dextrose solution) should be given as IVF. The hepatic glycogen reserve is usually depleted in thyroid storm and dextrose will help replenishing it and to cope with continuously high metabolic demand. Naturally, electrolyte monitoring is recommended with dextrose solution infusion.

Bonus Pearl: Aspirin is contraindicated for control of pyrexia in thyroid storm and tylenol is the prefered agent.

Related pearl: Iodide in Thyroid Storm

Reference:

1. Thyroid Storm: Recognizing the signs and symptoms of this life-threatening complication. AJN, American Journal of Nursing. 102(5):33-35, May 2002.

2007-08-08T14:45:00.000-07:00

Wednesday August 8, 2007
Vasoconstrictor extravasation

Antidote for vasoconstrictor extravasation in skin and tissues (dopamine, epinephrine, or norepinephrine) is PHENTOLAMINE.

Infiltrate 5-15 mg of PHENTOLAMINE in 10 ml of normal saline into the area of extravasation as soon as possible. Treatment may be applied and effective up to 12 hours post extravasation of vasoconstrictor. Keep yourself ready for fluid bolus post treatment.

Mechanism of action: Phentolamine is a nonspecific alpha-adrenergic blocking agent which inhibits vasoconstriction and allow improved blood circulation through the affected area.

References: Click to get abstract or article

1. Drug Monographs - Phentolamine - lhsc.on.ca
2. Treating Extravasation Injuries - extravasation.org
3. The use of phentolamine in the prevention of dopamine-induced tissue extravasation - J Crit Care 1998 Mar;13(1):13-20

2007-08-07T10:48:00.000-07:00

Tuesday August 7, 2007
Fentanyl induced chest wall (thoracic) rigidity - FITR

Fentanyl is one of the most commonly used analgesic in ICUs. One of the relatively unknow but common side effect of Fentanyl is chest wall rigidity which was first reported about 25 years ago and may happen with low dose. Chest wall rigidity itself can lead to respiratory distress causing hypercapnia, and hypoxemia leading to bradycardia. Moreover, it may also make intubation difficult as often chest wall rigidity is associated with laryngospasm. Treatment is reversal with Naloxone. If respiratory failure does not resolve, airway should be secured followed with sedation and neuromuscular blockade till fentanyl wears off. The mechanism of action is not known but suspected to be neuraxis dopamine antagonism.

Fentanyl induced thoracic rigidity is relatively more common in neonates.

References: click to get abstract/article

1. Rigidity and hypercarbia associated with high dose fentanyl induction of anesthesia (Letter). Anesth Analg 1981; 60: 362–3

2. Opioid-induced rigidity after intravenous fentanyl - Obstetrics & Gynecology 1997;89:822-824

2007-08-06T11:16:00.001-07:00

Monday August 6, 2007
Regarding false positive Digoxin level

Many common clinical conditions may lead to false positive elevations of plasma digoxin and erroneous medical management. Actually, many experts don't believe in checking digoxin level unless there is any clinical manifestation due to many artifactual factors such as poor assay quality, incorrect timing or technique of drawing blood samples. Atleast, in following 3 conditions, there is an increase of endogenous digoxin-like substances in plasma which may lead to false positive result with total error upto 0.6 - 1.8 ng/mL.
chronic renal failure
hepatobiliary disease
in the third trimester of pregnancy

Also atleast 3 commonly used drugs (like steroid derivative drugs) may cross react with the digoxin radioimmunoassay and give false postive values.

spironolactone
methylprednisolone
Tobramycin

Note: New born neonates can have very high false postive digoxin level upto 4 ng/mL due to increased levels of endogenous digoxin-like substances.

References: click to get abstract/article

1. Digoxin-like substance in the serum of uremic patients before and after hemodialysis - Cardiovascular Drugs and Therapy, Volume 2, Number 6 / January, 1989
2. Cross-Reactivity of TDX and OPUS Immunoassay Systems for Serum Digoxin Determination. Therapeutic Drug Monitoring. 19(6):657-662, December 1997.
3. Falsely elevated digoxin levels: another look - Ther Drug Monit. 1989 Sep;11(5):572-3

2007-08-05T18:32:00.000-07:00

Sunday August 5, 2007
Sedatives and sexual dreams - a legal liability?

In 1847, after a year of ether anesthesia introduction, a dentist was convicted to 6 years of jail for sexually assaulting two girls under the influence of anaesthesia. There are well documented cases where physicians and dentists have lost their licenses for similar allegation. Anaesthetics particularly propofol (widely use in ICU) has been reported to be associated with vivid dreams and sexual fantasies though a fairly good study failed to show any association. Recently, Dr. Robert Strickland's report in this regard at the American Society of Anesthesiologists meeting has been widely reported in media and is worth reading. Click on reference # 2.

References: Click to get abstract or article

1. Dreams, images and emotions associated with propofol anaesthesia -Anaesthesia, Volume 52, Number 8, July 1997, pp. 750-755(6)
2. Anesthesia can give rise to sex illusion - ARIZONA DAILY STAR - 06.21.2005

2007-08-04T05:11:00.000-07:00

Saturday August 4, 2007
Hypomagnesemia and IV Magnesium (Mg) infusion

Hypomagnesemia has been reported in upto 60% of ICU patients and sometimes can be clinically very significant like in recovery phase of DKA (diabetic ketoacidosis). Symptoms of severe hypomagnesemia (less than 1 mEq/L) include respiratory failure, hyperactive deep-tendon reflexes, muscular fibrillations, mental status changes, tetany, seizures, positive Chvostek and Trousseau signs. EKG manifestations are prolong PR interval, widened QRS complex, ST depression, altered T waves and last but not the least is loss of voltage. About 33% of serum magnesium is protein-bound but unfortunately wide-spread test for free or active (ionized) magnesium is not available. It is a common practice to write IV Mg orders in grams or mls.

1 gram of IV Mg contains 8.12 meq of Mg and
1 meq of Mg provides 12 mg of elemental Mg.

One ml MgSO4 50% Solution = 4 meq Magnesium
One ml MgSO4 10% Solution = 8 meq Magnesium

Rapid IV administration can induce life threatening cardiac dysrhythmias, hypotension, flushing, sweating, sensation of warmth and hypocalcemia. In non-emergent cases, general rule of thumb is to infuse 1 gram per 1 hour. In risky situations, like impending arrhythmia, 2 grams of IV Magnesium sulfate may be given over 20 minutes. In extremely emergent cases 2 grams (16 mEq) of IV MgSO4 may be administered over 5 minutes and actually may be given as IV push if there is no permission of time.

In Preeclampsia, load IV 4-6 grams of MgSO4 in 100 ml of D5W over 20-30 minutes and maintenance is 2-3 grams/hour with close monitoring of target level (goal of 4-7 mEq/L) and clinical manifestations like decrease deep tendon reflexes. It is not a bad idea to keep IV calcium at bedside during massive IV magnesium infusion as in preeclampsia.

IV calcium is an antidote for magnesium overdose.

In kidney dysfunction, IV magnesium dose should be reduced by about 50%.

2007-08-03T19:10:00.000-07:00

Friday August 3, 2007
step-up oxygen saturation and VSD

Case: 61 year old male admitted with Angina. Cardiac cath. showed 3 vessel disease. Cardiac Bypass surgery planned for next morning. Patient admitted back to CCU with protocolized post cardiac cath orders. Around 12 midnight, patient suddenly became hypotensive. Arriving at bedside you noticed tall v waves on pulmonary artery catheter tracings. You suspect flail Mitral valve (Mitral regurgitation - MR) with possible ruptured Chordae tendinae. Cardiologist is also concerned about ventricular septal defect (VSD). Unfortunately, STAT Echo is not available at 12 MN. What would be the best way to differentiate between MR and VSD ?

VSD is very difficult to diagnose from MR on clinical grounds. VSD can be differentiated from MR by demonstrating a step-up in oxygen saturation in the right ventricle. (By collecting blood from CVP, RV and PA/distal ports of PA catheter).

If oxygen saturation level in right ventricle is more than 5% from right atrium or 8% from pulmonary artery (due left-to-right shunt across the ventricular septum), it is diagnostic of VSD. In this era of technology, echocardiography is preferable, if available, due to its non-invasive and good diagnostic value.

Reference: click to get abstract/article

Hemodynamic complications of ventricular septal rupture after acute myocardial infarction - Catheterization and Cardiovascular Interventions, Volume 60, Issue 4 , Pages 509 - 514, 2003

2007-08-02T12:55:00.000-07:00

Thursday August 2, 2007

Case: 24 year old male admitted with left thigh cellulitis and abcess. I and D was performed and cefazolin (ancef) was initiated. Patient did not respond to cefazolin and antibiotic was changed to vancomycin after availability of sensitivity from micro lab. Patient showed marked improvement over next 3 days except patient complaint of new rash on his body which you attributed to "Red man syndrome" and wrote an order to infuse vancomycin slowly and with increase dilution. Next day, as you reached hospital, you were informed by outgoing intensivist that patient deteriorated overnight and required intubation. You were baffled and as you examine the patient, you find extensive dermal exfoliation along with axillary and inguinal lymphadenopathy. On lab, LDH and liver enzymes were markedly elevated and kidney funtion deteriorated from normal to anuria. CBC showed eosinophilia.

Vancomycin-induced Stevens-Johnson syndrome

Stevens-Johnson syndrome is an acute mucocutaneous process characterized by severe exfoliative dermatitis and mucosal involvement of the gastrointestinal tract and conjunctiva. Pathogenesis is unclear, but an immunological mechanism, probably cell-mediated, has been suggested. Clinical diagnosis of Stevens-Johnson syndrome is based on the presence of "target" or "iris" lesions involving the skin and erosive lesions of two or more mucosal surfaces. Associated findings include extensive dermal exfoliation, nephritis, lymphadenopathy, hepatitis, and multiple serologic abnormalities. Vancomycin, a glycopeptide antibiotic, has case reports in literature produceing immunologically mediated adverse reactions such as interstitial nephritis, linear IgA bullous dermatosis, exfoliative erythroderma, necrotizing cutaneous vasculitis and toxic epidermal necrolysis. The treatment consists of cessation of vancomycin and administration of antihistamine and/or steroid.

References: click to get abstract/article

1.Vancomycin-induced Stevens-Johnson syndrome Allergy Asthma Proc. 1996 Mar-Apr;17(2):75-8.

2.Stevens-Johnson-type reaction with vancomycin treatment. - Ann Pharmacother. 1992 Dec;26(12):1520-1

3 Uncommon Vancomycin-Induced Side Effects - Brazilian Journal of Infectious Diseases - 2002;6(4):196-200

2007-08-01T15:44:00.000-07:00

Wednesday August 1, 2007

Q; 72 year old female with no significant past medical history has been admitted from ER to ICU with progressive mental status change over last 3 days. Only significant finding in workup is Na+ of 123 mEq/liter. The only pertinent history is start of a new anti-depressant medication about 2 weeks ago. Per son, there is no sign of drug over-dose ?

A; Anti-depressants' associated hyponatremia.One of the significant but less know side effect of anti-depressants, mostly SSRIs is hyponatremia. Exact mechansism is unknown but it causes SIADH (Syndrome of Inappropriate Antidiuretic Hormone). It has also been reported with 'atypical' anti-depressents' (venlafaxine, trazodone, maprotiline, nefazodone, bupropion) as well as with tricyclic antidepressants (TCAs) and monamine oxidase inhibitors (MAOIs).When prescribing antidepressants particularly to elderly patients, consideration of hyponatremia should be kept in mind. Patients who develop mental status change need prompt assessment of electrolytes' status. Patients already at risk of the SIADH (such as cancer) should be prescribed anti-depressent with caution and close followup.

Related previous pearl: ANTIDEPRESSANTS' AND SEROTONIN SYNDROME

References: click to get abstract/artice

1. Hyponatremia in the psychiatric population: a review of diagnostic and management strategies. Psychiatr Ann 2003; 33:318–325

2. Hyponatremia secondary to antidepressants. Psychiatr Ann 2003; 33:333–339

3. Hyponatremia in elderly psychiatric patients treated with selective serotonin reuptake inhibitors and venlafaxine: a retrospective controlled study in an inpatient unit. Int J Geriatr Psychiatry 2002; 17:231–237

4. Hyponatremia with venlafaxine. Ann Pharmacother 1998; 32:49–50

5. Severe symptomatic hyponatremia during citalopram therapy - a case report - BMC Nephrology 2004, 5:2