Critical care: Difference between revisions

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imported>Robert Badgett
imported>Robert Badgett
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===Respiration and oxygenation===
===Respiration and oxygenation===
;PaO<sub>2</sub>/FiO2 ratio (PF ratio)
;PaO<sub>2</sub>/FiO2 ratio (PF ratio)
:<math>{P/F\ ratio} = \left (\frac{PaO_2}{Fi0_2}\right) \times 100</math>
* Normal is 500
* ARDS is < 200
This measure is easier to calculate. Comparative studies suggest it correlates better with pulmonary shunts than does the A-a gradient.<ref name="pmid6409506">{{cite journal |author=Covelli HD, Nessan VJ, Tuttle WK |title=Oxygen derived variables in acute respiratory failure |journal=Crit. Care Med. |volume=11 |issue=8 |pages=646–9 |year=1983 |pmid=6409506 |doi=}}</ref><ref name="pmid14769743">{{cite journal |author=El-Khatib MF, Jamaleddine GW |title=A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery |journal=Chest |volume=125 |issue=2 |pages=592–6 |year=2004 |pmid=14769743 |doi=}}</ref><ref name="pmid3191742">{{cite journal |author=Cane RD, Shapiro BA, Templin R, Walther K |title=Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients |journal=Crit. Care Med. |volume=16 |issue=12 |pages=1243–5 |year=1988 |pmid=3191742 |doi=}}</ref>
This measure is easier to calculate. Comparative studies suggest it correlates better with pulmonary shunts than does the A-a gradient.<ref name="pmid6409506">{{cite journal |author=Covelli HD, Nessan VJ, Tuttle WK |title=Oxygen derived variables in acute respiratory failure |journal=Crit. Care Med. |volume=11 |issue=8 |pages=646–9 |year=1983 |pmid=6409506 |doi=}}</ref><ref name="pmid14769743">{{cite journal |author=El-Khatib MF, Jamaleddine GW |title=A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery |journal=Chest |volume=125 |issue=2 |pages=592–6 |year=2004 |pmid=14769743 |doi=}}</ref><ref name="pmid3191742">{{cite journal |author=Cane RD, Shapiro BA, Templin R, Walther K |title=Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients |journal=Crit. Care Med. |volume=16 |issue=12 |pages=1243–5 |year=1988 |pmid=3191742 |doi=}}</ref>


;Alveolar-arterial oxygen (A-a) gradient (alveolar-arterial oxygen difference - AVO<sub>2</sub>D)
;Alveolar-arterial oxygen (A-a) gradient (alveolar-arterial oxygen difference - AVO<sub>2</sub>D)
:<math>\mbox{A-a gradient} = {PAO_2}\  -\  {PaO_2}</math>
:<math>{PAO_2} = {Fi0_2} *\left ({760 - 47}\right) \  -\  \frac{PaCO_2}{0.8}</math>
* Normal is < 10 mm Hg
The A-a gradient is harder to calculate, but accounts for changes in respiration as measured by the [[partial pressure]] of carbon dioxide. However, this calculation relies on the respiratory quotient being constant in the prediction of alveolar CO<sub>2</sub> When compared to the PF ratio, the A-a gradient is found to correlate less well with pulmonary shunting.<ref name="pmid6409506">{{cite journal |author=Covelli HD, Nessan VJ, Tuttle WK |title=Oxygen derived variables in acute respiratory failure |journal=Crit. Care Med. |volume=11 |issue=8 |pages=646–9 |year=1983 |pmid=6409506 |doi=}}</ref><ref name="pmid14769743">{{cite journal |author=El-Khatib MF, Jamaleddine GW |title=A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery |journal=Chest |volume=125 |issue=2 |pages=592–6 |year=2004 |pmid=14769743 |doi=}}</ref><ref name="pmid3191742">{{cite journal |author=Cane RD, Shapiro BA, Templin R, Walther K |title=Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients |journal=Crit. Care Med. |volume=16 |issue=12 |pages=1243–5 |year=1988 |pmid=3191742 |doi=}}</ref>
The A-a gradient is harder to calculate, but accounts for changes in respiration as measured by the [[partial pressure]] of carbon dioxide. However, this calculation relies on the respiratory quotient being constant in the prediction of alveolar CO<sub>2</sub> When compared to the PF ratio, the A-a gradient is found to correlate less well with pulmonary shunting.<ref name="pmid6409506">{{cite journal |author=Covelli HD, Nessan VJ, Tuttle WK |title=Oxygen derived variables in acute respiratory failure |journal=Crit. Care Med. |volume=11 |issue=8 |pages=646–9 |year=1983 |pmid=6409506 |doi=}}</ref><ref name="pmid14769743">{{cite journal |author=El-Khatib MF, Jamaleddine GW |title=A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery |journal=Chest |volume=125 |issue=2 |pages=592–6 |year=2004 |pmid=14769743 |doi=}}</ref><ref name="pmid3191742">{{cite journal |author=Cane RD, Shapiro BA, Templin R, Walther K |title=Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients |journal=Crit. Care Med. |volume=16 |issue=12 |pages=1243–5 |year=1988 |pmid=3191742 |doi=}}</ref>


Revision as of 10:56, 2 September 2009

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Critical care medicine is the "health care provided to a critically ill patient during a medical emergency or crisis".[1]

Monitoring the critically ill patient

Swan-Ganz catheterization

Respiration and oxygenation

PaO2/FiO2 ratio (PF ratio)
  • Normal is 500
  • ARDS is < 200

This measure is easier to calculate. Comparative studies suggest it correlates better with pulmonary shunts than does the A-a gradient.[2][3][4]

Alveolar-arterial oxygen (A-a) gradient (alveolar-arterial oxygen difference - AVO2D)
  • Normal is < 10 mm Hg

The A-a gradient is harder to calculate, but accounts for changes in respiration as measured by the partial pressure of carbon dioxide. However, this calculation relies on the respiratory quotient being constant in the prediction of alveolar CO2 When compared to the PF ratio, the A-a gradient is found to correlate less well with pulmonary shunting.[2][3][4]

Among outpatients with possible pulmonary embolism, the A-a gradient may be a better test.[5]

An online calculator for the A-a gradient is at http://www.mdcalc.com/aagrad.


Treatments provided in the intensive care unit

Circulatory support

Respiratory support

For more information, see: Artificial respiration.


Complications

Abdominal compartment syndrome

Abdominal compartment syndrome is associated with increased mortalty.[6]

Medical error

For more information, see: Medical error.

Examining errors in administration of parenteral medications, a study found:[7]

  • 74 errors per 100 patient-days
  • Independent risk factors were:
    • Patient complexity as measured by
      • number of organ failures
      • number of parenteral administrations
    • Work load as measured by
      • Larger intensive care unit
      • Increased ratio of patient turnover to the size of the unit
      • Number of patients per nurse
      • Occupancy rate of the unit

Preventing complications in the critically ill patient

Glucose control

Two clinical practice guidelines are available for patients with ; however, both of these guidelines were developed without broad representation of stakeholders.[8] This may lead to overly aggressive clinical recommendations. In addition, these guidelines were published before the two recent negative trials.

The American Association of Clinical Endocrinologists (AACE) recommends the following target blood glucose levels:[9]

  • "Critically ill patients, between 80 to 110 mg/dL (grade A recommendation)"

The American Diabetes Association (ADA) states[10]

  • "Critically ill patients: blood glucose levels should be kept as close to 110 mg/dl (6.1 mmol/l) as possible and generally <140 mg/dl (7.8 mmol/l). (A) These patients require an intravenous insulin protocol that has demonstrated efficacy and safety in achieving the desired glucose range without increasing risk for severe hypoglycemia. (E)"

Evidence

Randomized controlled trials of tight glucose control in the critical care and perioperative care settings have produced mixed results. See Table.

Selected randomized controlled trials of glucose control in critical care[11][12][13] [14][15]
Trial Patients Intervention Comparison Outcomes Results Authors' conclusions
Intensive control Control group
NICE-SUGAR[11]
2009		 6104 patients in medical and surgical ICU Insulin drip targeting serum glucose of 81 to 108 mg/dl Insulin drip targeting serum glucose of 144 - 180 mg/dl Mortality at 90 days 27.5% * 24.9% "intensive glucose control increased mortality among adults in the ICU"
Arabi et al[12]
2008		 523 patients in medical and surgical ICU Insulin drip targeting serum glucose of 80 to 110 mg/dl Insulin drip targeting serum glucose of 180 to 200 mg/dl Mortality in the intensive care unit 13.5% 17.1 "Intensive insulin therapy was not associated with improved survival...and was associated with increased occurrence of hypoglycemia"
SepNet[13]
2008		 537 patients with severe sepsis Insulin drip if needed to target serum glucose of 80 to 110 mg/dl Insulin drip if needed to target serum glucose of < 200 mg/dl Mortality in the intensive care unit 24.7% 26% "intensive insulin therapy placed critically ill patients with sepsis at increased risk for serious adverse events"
Van den Berghe[14]
2006		 1200 patients in medical ICU Insulin drip targeting serum glucose of 80 to 110 mg/dl Insulin drip targeting serum glucose of 180 to 200 mg/dl Hospital mortality 37.3% 40% "Intensive insulin therapy significantly reduced morbidity but not mortality"
Van den Berghe[15]
2001		 1548 patients in surgical ICU Insulin drip targeting serum glucose of 80 to 110 mg/dl Insulin drip targeting serum glucose of 180 to 200 mg/dl Mortality in the intensive care unit 4.6% * 8% "Intensive insulin therapy...reduces morbidity and mortality"
Notes:
* Significantly different from the control group.

Two of the trials in the Table suggested benefit (see green cells):

  • Van den Berghe 2006[14]. Although this trial concluded "intensive insulin therapy significantly reduced morbidity but not mortality among all patients in the medical ICU. Although the risk of subsequent death and disease was reduced in patients treated for three or more days" the trial stated "these patients could not be identified before therapy."[14]
  • Van den Berghe 2002[15]. This trial has been criticized for the following reasons:[16]
  1. "The trial was stopped early for an unexpectedly large treatment effect, which can overestimate the efficacy of treatment or result in a false-positive finding;"
  2. "The relative reduction in mortality for a decrease of 50 mg/dL in morning glucose levels seems biologically implausible and exceeds that for any other intervention in critically ill patients;"
  3. "The mortality rate in the control group was much higher than that noted in tertiary care medical centers in the United States. On admission to the ICU, all patients received 200 to 300 g/d of intravenous dextrose followed by enteral or parenteral nutrition, an unusual practice considering the deleterious effects of parenteral nutrition; at least in part, the difference in outcomes between the 2 arms in this study might have reflected the harm of maintaining the control group as hyperglycemic rather than the benefit of strict glucose control in the intervention group."

Tight control may protect renal function.[17]

Regarding intraoperative control of glucose, a randomized controlled trial concluded "the increased incidence of death and stroke in the intensive treatment group raises concern about routine implementation of this intervention."[18]

Preventing anemia

Blood transfusion

There may not be a meaningful difference in outcomes between transfusing blood to maintain a hemoglobin > 7.0 g/dl versus a hemoglobin > 10.0 g/dl.[19]

Erythropoietin

A randomized controlled trial reported "epoetin alfa does not reduce the incidence of red-cell transfusion among critically ill patients, but it may reduce mortality in patients with trauma. Treatment with epoetin alfa is associated with an increase in the incidence of thrombotic events."[20]

Selective gastrointestinal decontamination

Systematic reviews conclude that selective decontamination of the digestive tract may reduce morbidity in critically ill patients[21][22][23] although some randomized controlled trials have[24][25][26] and others have not found benefit[27].

Preventing gastrointestinal tract ulceration

Preventing deep venous thrombosis

For more information, see: Deep venous thrombosis.


Preventing healthcare-associated pneumonia

Medical error in the intensive care

For more information, see: medical error.

Regarding overlooked diagnosis among patients receiving artificial respiration in the intensive care, an autopsy study concluded "abdominal pathologic conditions--abscesses, bowel perforations, or infarction--were as frequent as pulmonary emboli as a cause of class I errors. While patients with abdominal pathologic conditions generally complained of abdominal pain, results of examination of the abdomen were considered unremarkable in most patients, and the symptom was not pursued." [28]

Predicting outcomes of adult patients

Although there is much research into prognosing patients in intensive care, patients are not very confident in thei accuracy of prognoses.[29]

Apache II score

For more information, see: APACHE II.

The APACHE II is available at http://www.sfar.org/scores2/apache22.html.

SAPS II

References

  1. ↑ Anonymous. Critical care. National Library of Medicine. Retrieved on 2008-01-07.
  2. ↑ 2.0 2.1 Covelli HD, Nessan VJ, Tuttle WK (1983). "Oxygen derived variables in acute respiratory failure". Crit. Care Med. 11 (8): 646–9. PMID 6409506. [e]
  3. ↑ 3.0 3.1 El-Khatib MF, Jamaleddine GW (2004). "A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery". Chest 125 (2): 592–6. PMID 14769743. [e]
  4. ↑ 4.0 4.1 Cane RD, Shapiro BA, Templin R, Walther K (1988). "Unreliability of oxygen tension-based indices in reflecting intrapulmonary shunting in critically ill patients". Crit. Care Med. 16 (12): 1243–5. PMID 3191742. [e]
  5. ↑ McFarlane MJ, Imperiale TF (1994). "Use of the alveolar-arterial oxygen gradient in the diagnosis of pulmonary embolism". Am. J. Med. 96 (1): 57–62. PMID 8304364. [e]
  6. ↑ Malbrain ML, Chiumello D, Pelosi P, et al (February 2005). "Incidence and prognosis of intraabdominal hypertension in a mixed population of critically ill patients: a multiple-center epidemiological study". Crit. Care Med. 33 (2): 315–22. PMID 15699833. [e]
  7. ↑ Valentin A, Capuzzo M, Guidet B, et al (2009). "Errors in administration of parenteral drugs in intensive care units: multinational prospective study". BMJ 338: b814. PMID 19282436. [e]
  8. ↑ Mulrow CD, Lohr KN (April 2001). "Proof and policy from medical research evidence". J Health Polit Policy Law 26 (2): 249–66. PMID 11330080. [e]
  9. ↑ AACE Diabetes Mellitus Clinical Practice Guidelines Task Force (2007). "American Association of Clinical Endocrinologists medical guidelines for clinical practice for the management of diabetes mellitus". Endocr Pract 13 Suppl 1: 1–68. PMID 17613449. [e] Complete summary from National Guidelines Clearinghouse
  10. ↑ American Diabetes Association (January 2008). "Standards of medical care in diabetes--2008". Diabetes Care 31 Suppl 1: S12–54. DOI:10.2337/dc08-S012. PMID 18165335. Research Blogging. Complete summary from National Guidelines Clearinghouse
  11. ↑ 11.0 11.1 The NICE-SUGAR Study Investigators (March 2009). "Intensive versus conventional glucose control in critically ill patients". N. Engl. J. Med. 360 (13): 1283–97. DOI:10.1056/NEJMoa0810625. PMID 19318384. Research Blogging.
  12. ↑ 12.0 12.1 Arabi YM, Dabbagh OC, Tamim HM, et al (December 2008). "Intensive versus conventional insulin therapy: a randomized controlled trial in medical and surgical critically ill patients". Crit. Care Med. 36 (12): 3190–7. DOI:10.1097/CCM.0b013e31818f21aa. PMID 18936702. Research Blogging.
  13. ↑ 13.0 13.1 Brunkhorst FM, Engel C, Bloos F, et al (2008). "Intensive insulin therapy and pentastarch resuscitation in severe sepsis". N. Engl. J. Med. 358 (2): 125–39. DOI:10.1056/NEJMoa070716. PMID 18184958. Research Blogging.
  14. ↑ 14.0 14.1 14.2 14.3 Van den Berghe G, Wilmer A, Hermans G, et al (2006). "Intensive insulin therapy in the medical ICU". N. Engl. J. Med. 354 (5): 449–61. DOI:10.1056/NEJMoa052521. PMID 16452557. Research Blogging.
  15. ↑ 15.0 15.1 15.2 van den Berghe G, Wouters P, Weekers F, et al (2001). "Intensive insulin therapy in the critically ill patients". N. Engl. J. Med. 345 (19): 1359–67. PMID 11794168. [e]
  16. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named pmid18380987
  17. ↑ Schetz M, Vanhorebeek I, Wouters PJ, Wilmer A, Van den Berghe G (2008). "Tight blood glucose control is renoprotective in critically ill patients". J. Am. Soc. Nephrol. 19 (3): 571-8. DOI:10.1681/ASN.2006101091. PMID 18235100. Research Blogging.
  18. ↑ Gandhi GY, Nuttall GA, Abel MD, et al (2007). "Intensive intraoperative insulin therapy versus conventional glucose management during cardiac surgery: a randomized trial". Ann. Intern. Med. 146 (4): 233–43. PMID 17310047. [e]
  19. ↑ Hébert PC, Wells G, Blajchman MA, et al (1999). "A multicenter, randomized, controlled clinical trial of transfusion requirements in critical care. Transfusion Requirements in Critical Care Investigators, Canadian Critical Care Trials Group". N. Engl. J. Med. 340 (6): 409–17. PMID 9971864. [e]
  20. ↑ Corwin HL, Gettinger A, Fabian TC, et al (2007). "Efficacy and safety of epoetin alfa in critically ill patients". N. Engl. J. Med. 357 (10): 965–76. DOI:10.1056/NEJMoa071533. PMID 17804841. Research Blogging.
  21. ↑ Chan EY, Ruest A, Meade MO, Cook DJ (2007). "Oral decontamination for prevention of pneumonia in mechanically ventilated adults: systematic review and meta-analysis". BMJ 334 (7599): 889. DOI:10.1136/bmj.39136.528160.BE. PMID 17387118. Research Blogging.
  22. ↑ Silvestri L, van Saene HK, Milanese M, Gregori D, Gullo A (2007). "Selective decontamination of the digestive tract reduces bacterial bloodstream infection and mortality in critically ill patients. Systematic review of randomized, controlled trials". J. Hosp. Infect. 65 (3): 187–203. DOI:10.1016/j.jhin.2006.10.014. PMID 17244516. Research Blogging.
  23. ↑ Silvestri L, van Saene HK, Milanese M, Gregori D (2005). "Impact of selective decontamination of the digestive tract on fungal carriage and infection: systematic review of randomized controlled trials". Intensive Care Med 31 (7): 898–910. DOI:10.1007/s00134-005-2654-9. PMID 15895205. Research Blogging.
  24. ↑ de Jonge E, Schultz MJ, Spanjaard L, et al (2003). "Effects of selective decontamination of digestive tract on mortality and acquisition of resistant bacteria in intensive care: a randomised controlled trial". Lancet 362 (9389): 1011–6. PMID 14522530. [e]
  25. ↑ Cockerill FR, Muller SR, Anhalt JP, et al (1992). "Prevention of infection in critically ill patients by selective decontamination of the digestive tract". Ann. Intern. Med. 117 (7): 545–53. PMID 1524328. [e]
  26. ↑ Stoutenbeek CP, van Saene HK, Little RA, Whitehead A (2007). "The effect of selective decontamination of the digestive tract on mortality in multiple trauma patients: a multicenter randomized controlled trial". Intensive Care Med 33 (2): 261–70. DOI:10.1007/s00134-006-0455-4. PMID 17146635. Research Blogging.
  27. ↑ Gastinne H, Wolff M, Delatour F, Faurisson F, Chevret S (1992). "A controlled trial in intensive care units of selective decontamination of the digestive tract with nonabsorbable antibiotics. The French Study Group on Selective Decontamination of the Digestive Tract". N. Engl. J. Med. 326 (9): 594–9. PMID 1734249. [e]
  28. ↑ Papadakis MA, Mangione CM, Lee KK, Kristof M (1991). "Treatable abdominal pathologic conditions and unsuspected malignant neoplasms at autopsy in veterans who received mechanical ventilation". JAMA 265 (7): 885–7. PMID 1992186. [e]
  29. ↑ Zier LS, Burack JH, Micco G, et al (August 2008). "Doubt and belief in physicians' ability to prognosticate during critical illness: the perspective of surrogate decision makers". Crit. Care Med. 36 (8): 2341–7. DOI:10.1097/CCM.0b013e318180ddf9. PMID 18596630. Research Blogging.
  30. ↑ Le Gall JR, Lemeshow S, Saulnier F (1993). "A new Simplified Acute Physiology Score (SAPS II) based on a European/North American multicenter study". JAMA 270 (24): 2957–63. PMID 8254858. [e]
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