Saturday October 13, 2007
Dopamine dosing on pump !


Beauty of Critical Care Medicine is in details


In contrast to dosing of other vasopressors, it is important to dose Dopamine on "ideal" body weight instead of actual body weight.

Unexpected tachycardia or hypertension may occur due to overdosing, if actual body weight instead of "ideal" body weight punched on pump. This is important to understand as in ICU it is very frequent to have high actual body weight due to fluid resuscitation. The right way to write dopamine dosing is like,

Start Dopamine drip with 2 mcg/kg/min of "Ideal" body weight and titrate as needed upto 20 mcg/kg/min. Call physician if heart rate more than 120 or Mean Blood Pressure more than 100.



Further recommended reading

1. Dopamine administration - Intensive Care Medicine , Volume 10, Number 5 / September, 1984
2. The ICU Book - 3rd edition, Paul L. Marino, Page 301

Friday October 12, 2007

Scenario: Nurse call you as patient 's SVRI (Systemic Vascular Resistance Index) is only 372. As you asked further hemodynamics data, you were given following info:

MAP (Mean Arterial Pressure) = 80 ,
CI (Cardiac Index) = 4.0,
CVP = 10

What what be your response?

1. Do Nothing - you are happy with this number
2. Recalibrate and recheck the SVRI again as it appears to be an error.
3. Titrate the vasopressor up.
4. Give fluid.
5. Give Lasix.

Answer: B

This is probably an error as formula for SVRI is

SVRI = (MAP - CVP) / CI x 80

so SVRI in above case should be:

(80 - 10)/4 x 80 = 1400

Objective of above question is to emphasize the point that, with high dependence on technology and computer chips, errors are common and its very important to obtain full picture when things appear out of normal for no reason and does not fit with full picture. It is more important to know "What not to do" than to know "what to do" !

It is very frequent in board exams to have questions with objective to identify erroneous data !

Thursday October 11, 2007
Carbon Dioxide Angiography

Carbon dioxide (CO2) gas is used as an alternative contrast to iodinated contrast material. When injected into a blood vessel, carbon dioxide bubbles displace blood, allowing vascular imaging. Because of the lack of nephrotoxicity and allergic reactions, CO2 is increasingly used as a contrast agent for diagnostic angiography and vascular interventions.

CO2 is particularly useful in patients with renal insufficiency or a history of hypersensitivity to iodinated contrast medium. Also, it is safe as CO2 is effectively eliminated by means of respiration.

Disadvantage: CO2 is less dense than iodinated contrast medium, and the overall quality of the CO2 vascular image is less than the contrast medium.


Cautions:

• CO2 should not be used as a contrast agent in the coronary and cerebral circulations because of the possibility of adverse effects secondary to a gas embolism. Safely, CO2 should be avoided in vessels above the diaphragm.
• In patients with pulmonary insufficiency or pulmonary hypertension because of amount diagnostic doses of CO2 pulmonary arterial pressure may increase.
• In right-to-left shunts Co2 may cause paradoxical gas embolism.
  
  

See slide presentation CARBON DIOXIDE ANGIOGRAPHY AND INTERVENTION CARBON DIOXIDE (Jim Caridi MD. University of Florida. Gainesville, FL)



Reference: click to get article

Carbon Dioxide Angiography - emedicine.com

Wednesday October 10, 2007
Significance of venous blood gas

Venous blood gasses are easy to obtained but very under-utilized in ICUs.

In ICU setting where hypotension and hypoperfusion are very common, it is very important to know that although information about arterial blood gases is needed to assess pulmonary gas exchange, in the presence of severe hypoperfusion, the hypercapnia and acidemia at the level of the tissues are detected better and correlate more in central venous blood.



References: click to get abstracts

Assessing acid-base status in circulatory failure. Differences between arterial and central venous blood - Volume 320:1312-1316, , May 18. 1989

Comparison of Blood Gas and Acid-Base Measurements in Arterial and Venous Blood Samples in Patients with Uremic Acidosis and Diabetic Ketoacidosis in the Emergency Room - American Journal of Nephrology 2000;20:319-323

Agreement between arterial and central venous values for pH, bicarbonate, base excess, and lactate.. Emerg. Med. J. 23: 622-624

Tuesday October 9, 2007
"Locked-in" Syndrome (coma vigilante)

Patient is a silent and unresponsive witness to everything that is happening" - from story of Nick Chisholm 1


Patient with Locked-in syndrome is a fully conscious person, but all the voluntary muscles of the body are completely paralyzed, other than those that control eye movement. Term was first introduced about 25 years ago by Plum and Posner with complete occlusion of the basilar artery. 3

Locked-In syndrome can be caused by stroke at the level of the basilar artery denying blood to the ventral part of the pons, among other causes. Any catastrophy involving ventral pons can cause this syndrome like massive stroke, traumatic head injury, ruptured aneurysm, pontine infarction after prolonged vertebrobasilar ischaemia, haemorrhage, tumor, central pontine myelinolysis, pontine abscess or postinfective polyneuropathy. As all of the nerve tracts responsible for voluntary movement pass through the ventral pons but fortunately or unfortunately, consciousness are above the level of the ventral pons. 2

Only supportive rehabilitation is the answer.

Being an intensivist, it is extremely important to educate staff and to protect patient from any physical or psychological harm (like procedure without adequate analgesia), with an upmost understanding that it is an "imprisoned mind buried alive in a dead body’’ (as said for character with paralysis like locked-in syndrome in Thérèse Raquin by Emile Zola - 1868).


References: Click to get articles/abstract

1. The patient's journey: Living with locked-in syndrome - BMJ 2005;331:94-97 (9 July)
2. Locked-in Syndrome - enotes.com
3. Plum F, Posner JB. The diagnosis of stupor and coma. Philadelphia: FA Davis, 1982; 377
4. Locked-in syndrome: a catastrophic complication after surgery - British Journal of Anaesthesia, 2004, Vol. 92, No. 2 286-288

Monday October 8, 2007
Comparison of two dose regimens of arginine vasopressin in advanced vasodilatory shock.


Even though not an establish part of guidelines and literature is not plenty either, vasopressin has fastly become an integral pressor in most ICUs across USA. Usual acceptable dose is 0.04 units/min.

Very recently, a retrospective controlled study of 78 patients published, to evaluate the effects of two vasopressin dose regimens (0.033 vs. 0.067 IU/min) on treatment efficacy, hemodynamic response, prevalence of adverse events, and changes in laboratory variables.

78 patients with vasodilatory shock (mean norepinephrine dosage, 1.07 mcg//min were given supplementary infusion of vasopressin. 2 groups were

• 0.033 (n = 39) and
• 0.067 IU/min (n = 39)

Cardiocirculatory, laboratory, and clinical variables were evaluated and compared between groups before and at 0.5, 1, 4, 12, 24, 48, and 72 hrs after initiation of Vasopressin (AVP).

Treatment efficacy was assessed by the increase in mean arterial blood pressure and the extent of norepinephrine reduction during the first 24 hrs of vasopressin therapy.


Results:

• Although the relative increase in mean arterial pressure was comparable between groups (16.8 +/- 18.4 vs. 21.4 +/- 14.9 mm Hg), norepinephrine could be reduced significantly more often in patients receiving 0.067 IU/min.
• AVP at 0.067 IU/min resulted in a higher mean arterial pressure (p < .001), lower central venous pressure (p = .001), lower mean pulmonary arterial pressure (p = .04), and lower norepinephrine requirements (p < .001) during the 72-hr observation period.
• Increases in liver enzymes occurred more often in patients treated with 0.033 IU/min (71.8% vs. 28.2% - p < .001) !
• The prevalence of a decrease in cardiac index, decrease in platelet count, and increase in total bilirubin was not significantly different between groups.
• Base deficit were lower and arterial lactate concentrations higher in patients receiving 0.033 IU/min.

Conclusions: Vasopressin dosages of 0.067 IU/min seem to be more effective to reverse cardiovascular failure in vasodilatory shock requiring high norepinephrine dosages than 0.033 IU/min.



Reference: click to get abstract/article

Comparison of two dose regimens of arginine vasopressin in advanced vasodilatory shock. - Critical Care Medicine. 35(10):2280-2285, October 2007.

Sunday October 7, 2007
Carvedilol (Coreg)



Q: How Carvedilol (Coreg) is different from other B-blockers?

A; Coreg is a triple blocker. It blocks beta-1, beta-2 and alpha-1 receptors. Alpha-1 blockade provides vasodilation and so protection in congestive heart failure (CHF). U.S. Carvedilol Heart Failure Study with 1094 patients showed 65% lower risk of death than placebo patients 1. Dose should be started at 3.125 mg BID and titrated (as tolerated) upto 25 mg BID. Obese patients may require higher dose.Extended release Metoprolol (Toprol XL) is another B-blocker approved from FDA for use in CHF. MERIT-HF study showed 34% reduction in mortality than placebo in patients taking Toprol XL 2.

FDA approves only Toprol-XL and Coreg for CHF.


References: Click to get article/abstract

1. The Effect of Carvedilol on Morbidity and Mortality in Patients with Chronic Heart Failure - N Engl J Med. 1996;334:1349-1355.

2. MERIT-HF Study Group. Effect of metoprolol CR/XL in chronic heart failure: metoprolol CR/XL randomised intervention trial in congestive heart failure. Lancet. 1999;353:2001-2007

Saturday October 6, 2007
On reintubation rate

Here is a little twist if you are proud of your too low reintubation rate !!

"A reintubation rate of 5% to 15% is acceptable; lower rates indicate the patients are being kept on the ventilator too long, while higher rates suggest that they are being taken off too soon". - Dr. Neil R. Macintyre - at ACCP annual meeting, october 23, 2006


Related links:

HOW TO ESTABLISH A VENTILATOR WEANING PROTOCOL , Gregory P. Marelich, MD - thoracic.org

When to wean from a ventilator: An evidence-based strategy, Ref: CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 70, NUMBER 5 MAY 2003 page 389


Related previous pearls:

Spontaneous Breathing Trial (SBT) - how long - 30 or 120 minutes?,

IV steroid to reduces postextubation stridor

Friday October 5, 2007
Our progress card on Venous Thromboembolism Prophylaxis in Acutely Ill Hospitalized Medical Patients


"Chest" recently reported physicians' progress card on Venous Thromboembolism Prophylaxis in 15,156 Acutely Ill Hospitalized Medical Patients from 52 hospitals in 12 countries via program called IMPROVE (international Medical Prevention Registry on Venous Thromboembolism).


Results:

• Only approximately 60% of patients who either met the ACCP criteria for requiring prophylaxis or were eligible for enrollment in randomized clinical trials that have shown the benefits of pharmacologic prophylaxis actually received prophylaxis.


• Intermittent pneumatic compression was the most common form of medical prophylaxis utilized in the United States, although it was used very rarely in other countries (22% vs 0.2%, respectively).


• Unfractionated heparin was the most frequent pharmacologic approach used in the United States (21% of patients), with low-molecular-weight heparin used most frequently in other participating countries (40%).


• There was also variable use of elastic stockings in the United States and other participating countries (3% vs 7%, respectively.

Conclusions; Data suggest that physicians’ practices for providing VTE prophylaxis to acutely ill hospitalized medical patients are suboptimal.




Reference: click to get article

1. Venous Thromboembolism Prophylaxis in Acutely Ill Hospitalized Medical Patients - Chest. 2007; 132:936-945

Thursday October 4, 2007
Hypothermia and hypocapnia !

Editors' note: Many time objective of our pearls is to introduce concepts which may be only of academic interest but intensivist need to be atleast aware of it.


Q: What's the relationship of CO2 production with level of hypothermia?

A: For every degree below 37 c, CO2 production decrease approximately by 10%, due to decrease metabolic demand. During post-operative warming, it should be kept in mind, anticipating rise in CO2 while weaning ventilator.

Wednesday October 3, 2007
Rocephin and calcium !


The safety labeling for IV ceftriaxone (Rocephin) has been updated by FDA to describe the potential risks associated with concomitant use of calcium or calcium-containing solutions in patients of any age (despite most reports are from neonates).

Per Roche, the maker of Rocephin, "the theoretical possibility exists for an interaction between ceftriaxone and IV calcium-containing solutions in patients other than neonates." Therefore, the use of ceftriaxone with calcium products is now contraindicated in all age groups.

Cases of fatal reactions with calcium-ceftriaxone precipitates in the lungs and kidneys have been reported in both term and premature neonates. Some of these cases occurred even when ceftriaxone and the calcium-containing products were administered by different routes at different times.

Because of the risk for particulate precipitation, ceftriaxone should not be mixed with calcium-containing solutions/products or reconstituted with calcium-containing diluents such as Ringer's or Hartmann's solution. Concomitant administration of ceftriaxone with calcium-containing solutions or products is likewise contraindicated, even via different infusion lines; 48 hours should elapse between the last dose of ceftriaxone and their use.


Reference: click to get article/abstract

1. IMPORTANT CLARIFICATION OF PRESCRIBING INFORMATION, fda - medwatch - Ceftriazone - August 2007

Tuesday October 2, 2007
Ethanol drip in Ethylene Glycol


Q; How you write Ethanol drip in Ethylene Glycol poisoning assuming you don't have Fomepizole or Dialysis available ?


A: Ethylene Glycol poisoning is common and can have bleak outcomes. Intensivists should be aware of all the possible interventions available. Antidotal therapy is based on preventing the alcohol dehydrogenase enzyme from metabolizing ethylene glycol into toxic byproducts. In case Fomepizole or Dialysis is not available, Ethanol will competitively inhibit alcohol dehydrogenase. But the serum ethanol level must be monitored frequently.Therapeutic ethanol is administered in a bolus followed by a continuous infusion. Initially, 7.5 to 10 mL/Kg of 10% ethanol, in D5W, is administered over 30 minutes. Then, a continuous infusion of 1 to 2 mL/Kg/hr of 10% ethanol is infused until the patient has eliminated all of the EG from his serum. It is important to keep the serum ethanol level at 100 to 150 mg/dL so as to completely inhibit the alcohol dehydrogenase enzyme.

Actual antidote or first line therapy is Fomepizole (Antizol) with fewer side effects. Fomepizole blocks alcohol dehydrogenase. Fomepizole is administered as 15 mg/Kg (up to 1 Gm) initially, then 10 mg/Kg q12h times four doses, and then 15 mg/Kg q12 hours until ethylene glycol level <10>


Bonus Pearl: Fomepizole can also be use as an antidote in Methanol overdose.

Monday October 1, 2007

Scenario: A patient was transferred to Critical Care Unit in septic shock. 4 out of 4 blood cultures were positive for Staphylococcus epidermidis and E. coli. Patient moved from Mexico to United States approximately six months ago for the treatment of HTLV-1 associated Lymphoma and has been on chemotherapy. What is the most likely cause of sepsis?

Diagnosis: Strongyloidiasis.

Strongyloides stercoralis is endemic in many areas of the world and is associated with HTLV-1. There is increased risk of disseminated strongyloides in immunocompromised individuals, and can result in pllymicrobial bacteremia.


Read very precise review article at emedicine.com: Strongyloides Stercoralis

click to get larger image

Reference: click to get abstract/article

1. A Canadian immigrant with coinfection of Strongyloides stercoralis and human T-lymphotropic virus 1 - CMAJ • August 28, 2007; 177 (5).

2. Complicated and fatal Strongyloides infection in Canadians: risk factors, diagnosis and management - CMAJ • August 31, 2004; 171 (5).