SICU Rounds Report - Sept 7th, 2010

Tobramycin Dosing and Levels. As an aminoglycoside, levels should be followed at peaks and troughs. In morbid obesity, dosage requirement may best be estimated using a dosing weight of IBW + 0.4 (TBW - IBW). Main concerns: causes nephrotoxicity (usually reversible), causes neuromuscular blockade, neurotoxicity (not reversible and related to total dose and duration), Cdiff. Draw peak 30 minutes after 30-minute infusion has been completed or 1 hour following I.M. injection or beginning of infusion; draw trough immediately before next dose

Therapeutic levels:

Peak:

Serious infections: 6-8 mcg/mL (SI: 12-17 μmol/L)

Life-threatening infections: 8-10 mcg/mL (SI: 17-21 μmol/L)

Urinary tract infections: 4-6 mcg/mL (SI: 7-12 μmol/L)

Synergy against gram-positive organisms: 3-5 mcg/mL

Trough:

Serious infections: 0.5-1 mcg/mL

Life-threatening infections: 1-2 mcg/mL

The American Thoracic Society (ATS) recommends trough levels of <1 style="font-size:78%;">American Thoracic Society and Infectious Diseases Society of America, “Guidelines for the Management of Adults With Hospital-Acquired, Ventilator-Associated, and Healthcare-Associated Pneumonia,” Am J Respir Crit Care Med, 2005, 171(4):388-416.

Reglan and Gastric Residuals. Both reglan (up to 10 mg q 6 hours) and eythromycin (up to 250 mg q 6 hours) improve gastric empyting, which is usually measured by given oral tylenol and following serum levels. There is no evidence of any clinical benefit, however. Use as an adjunct to help get your dobhoff post-pyloric (which probably doesn’t matter anyway) works for erythomycin but not metoclopramide. Nevertheless, routine use of erythromycin is not recommended because of concerns for macrolide abx resistance. Reglan of course is the subject of recent headlines because of growing class-action lawsuits over extrapyramidal effects. Rates are thought to be less than 1%, but keep an eye on your patients for any sign of movement disorder because tardive dyskinesia sucks and is not reversible.

Booth CM Gastrointestinal promotility drugs in the critical care setting: a systematic review of the evidence. Crit Care Med. 2002 Jul;30(7):1429-35.
Hawkyard CV, The use of erythromycin as a gastrointestinal prokinetic agent in adult critical care: benefits versus risks. J Antimicrob Chemother. 2007 Mar;59(3):347-58. Epub 2007 Feb 8.
Rao, AS, Camilleri, M. Review article: metoclopramide and tardive dyskinesia. Aliment Pharmacol Ther 2010; 31:11.

Normal WBC count in asplenic patients. After splenectomy, <15 style="font-size:78%;">McBride, JA, Dacie, JV, Shapley, R. The effect of splenectomy on the leucocyte count. Br J Haematol 1968; 14:225

Toutouzas KG. Leukocytosis After Posttraumatic Splenectomy Arch Surg. 2002;137:924-929.

Rapid Shallow Breathing Index. Very commonly used and validated index to predict whether a patient can be extubated. Simply divide the minute ventilation by the rate. The test is seriously confounded by the use of pressure support and even small (5 cm H2O) amounts of PEEP. Less than 105 is the traditional cutoff for success. Patients less than 120 usually fly, but may need some non-invasive positive pressure after extubation.

El Kahtib MG. Effect of pressure support ventilation and positive end expiratory pressure on the rapid shallow breathing index in intensive care unit patients Int Care Medicine Volume 34, Number 3, 505-510

IVC Filters Long Term. I have many questions about IVC filters. Do they work? Do they have thrombogenic potential? How long should they stay in? What is the difference between “permanent” and “temporary” filters? At what point have so many large venous collaterals formed that no additional benefit is given? Should they be placed in someone with a known PE but no proximal DVTs? Urgh. Apparently, only the radiologist know these secrets and they missed rounds again this morning.

Here is what I learned. There is no evidence that these filters affect mortality, though PE after placement is a rare event. In the biggest trial to date, filters reduced that amount of PEs in patients with DVTs acutely, but no difference in any outcome (including symptomatic PE and death) was seen at 2 years. Down the road, patients with filters tend to have more symptomatic DVTs. There is no prospective clinical data to recommend for routine use in high risk patient populations (bariatrics, major trauma, big spine surgery).

They appear to be very safe, with little acute or chronic complications. Mortality is less than 0.3% and has been due to IVC erosion or migration. Chronic lower extremity is reported to vary from 2 - 28%. No study goes out past 8 years. Because retrieving them can be challenging, all should be considered potentially permanent. There is no good data comparing different types.

Decousus, H, Leizorovicz, A, Parent, F, et al. A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein thrombosis. N Engl J Med 1998; 338:409.
Joels, CS, Sing, RF, Heniford, BT. Complications of inferior vena cava filters. Am Surg 2003; 69:654.