Wednesday, September 22, 2010

ICU Rounds Report - Sept 22nd 2010

From Cara
Contraction Alkalosis.  Contraction alkalosis is a form of metabolic alkalosis – an increase in pH due to an increase in HCO3.  What differentiates contraction alkalosis from other types of metabolic alkalosis is that the extracellular amount of bicarbonate remains the same whereas the bicarbonate concentration artificially increases due to loss of extracellular fluid that is relatively bicarbonate free.

This was first described by Cannon et al.'s 1965 study of contraction alkalosis in patients with congestive heart failure following diuresis with ethacrynic acid (a seldom used ototoxic non-sulfonamide loop diuretic).  They found that diuresis was accompanied by increase in bicarbonate, rise in pH, and increase in arterial carbon dioxide pressure.  Further, the fluid lost in the process of diuresis had virtually no bicarbonate, demonstrating that the extracellular fluid "contracted" around a stable amount of bicarbonate.

Administration of intravenous loop diuretics in an edematous patient is the most common cause of contraction alkalosis.  Other causes include states wherein a high chloride, low-bicarbonate solution is lost, such as sweat losses in cystic fibrosis, gastric secretion losses in patients with achlorhydria, and congenital chloride diarrhea.  

Timing of ICU admission. With increasing talk of 24 hour ICU staffing around the county (and here!) comes an interesting meta-analysis published by a group at Jefferson Medical College that complies the results of 10 studies evaluating the link between admission time and mortality. The good news: being admitted at night didn't seem to affect mortality overall (odds ratio [OR], 1.0 [95% CI, 0.87-1.17]; P = .956). Bad news? Coming in over the weekend increased your risk of dying by almost 10% (OR, 1.08 [95% CI, 1.04-1.13]; P < .001). No one knows why this is, but the researchers posit that decreased staff-to-patient ratios, unavailability of board-certified intensivists, physician fatigue, lack of ancillary staff, and difficulty in obtaining complex diagnostic tests or therapies may be the cause.

This follows previous studies that found patients with acute, severe medical illness (aortic aneurysm, ICH, etc) are more likely to die when admitted through the ED on a weekend. Finally, remember that trauma patients presenting between midnight and 6 am are more likely to be sick and much more likely to die.  Overall, more evidence suggesting that more intensive staffing (including 24 hour in-house intensivists) may be coming...
Cavallazzi R, Marik PE, Hirani A, Pachinburavan M, Vasu TS, Leiby BE. Association between time of admission to the intensive care unit and mortality: A systematic review and meta-analysis. Chest 2010;138:68–75
Bell CM. Mortality among patients admitted to hospitals on weekends as compared with weekdays. N Engl J Med 2001 345(9):663–668
Vaziri K.  Optimizing physician staffing and resource allocation: sine-wave variation in hourly trauma admission volume. J Trauma 2007 62(3):610–614.

Does Quetiapine Work? Seems to calm patients down a bit, but what are the data? Sarah Gruber (thanks Sarah!) points to a well-done, multicenter, placebo controlled RTC published this year in CCM that randomized 36 mixed ICU patients to either placebo or 50 mg every 12 hrs of quetiapine. The results were positive.

Quetiapine was associated with a shorter time to first resolution of delirium (1.0  vs. 4.5 days, p =.001) and a reduced duration of delirium (36  vs. 120 hrs; p =.006). There was a trend towards reduced mortality and decreased hospital LOS, but they were not significant in this small trial. Side effects, including rates of QTc prolongation and extrapyramidal symptons were similar in both groups.

Among the atypical antipyschotics, the authors point out that quetiapine has several favorable characteristics that make it a good choice in the ICU:  a short half-life that facilitates dose titration, lower propensity to alter the QTc interval, and very rare reports of extrapyramidal symptom effects.
Devlin JW. Efficacy and safety of quetiapine in critically ill patients with delirium: a prospective, multicenter, randomized, double-blind, placebo-controlled pilot study. Crit Care Med. 2010 Feb;38(2):419-27.

Jordan Hackworth, M.D.
Fellow, Critical Care Medicine
Department of Anesthesiology
University of Virginia

No comments:

Post a Comment