Category Archives: Critical Care

Critical Care

VBG versus ABG

Leave a comment

OVERVIEW

    Venous blood gases (VBG) are widely used in the emergency setting in preference to arterial blood gases (ABG) as a result of research published since 2001

    The weight of data suggests that venous pH has sufficient agreement with arterial pH for it to be an acceptable alternative in clinical practice for most patients

    Nevertheless acceptance of this strategy has been limited by some specialties and maybe inappropriate in some settings; for instance there is no data to confirm that this level of agreement is maintained in shock states or mixed acid-base disturbances
  
Clinically acceptable limits of agreement for blood gas parameters remains poorly defined

ARTERIAL BLOOD GAS PROS AND CONS

Advantages

    gold standard test for determining the arterial metabolic millieu (pH, PaCO2, HCO3)
    can determine PaO2

Disadvantages

    pH, PCO2 (if normocapnic), HCO3 and base excess from a VBG are usually adequate for clinical decision making
    SpO2 is usually sufficient for clinical decision making unless pulse oximetry is unreliable for other reasons (e.g. shock state, poor pick up)
    painful (should be performed with local anaesthetic in conscious patients)
    increased risk of bleeding and hematoma
    risk of pseudo aneurysm and AV fistula
    infection
    nerve injury
    digital ischemia
    injury to staff
    delays in care
    serial exams may be needed
    venous sampling may better represent the tissue milieu

CORRELATION BETWEEN VBG AND ABG

pH

    Good correlation
    pooled mean difference: +0.035 pH units

pCO2

    good correlation in normocapnia
    non-correlative in severe shock
    100% sensitive in detecting arterial hypercarbia in COPD exacerbations using cutoff of PaCO2 45 mmHg and laboratory based testing (McCanny et al, 2012), i.e. if VBG PCO2 is normal then hypercapnia ruled out (PaCO2 will be normal), though this conflicts with the meta-analysis by Byrne et al 2014 (see below)
    correlation dissociates in hypercapnia – values correlate poorly with PaCO2 >45mmHg
    Mean difference pCO2 +5.7 mmHg (wide range in 95%CIs among different studies, on the order of +/-20 mmHg)
    A more recent meta-analysis by Byrne et al, 2014 found that the 95% prediction interval of the bias for venous PCO2  was −10.7 mm Hg to +2.4 mm Hg. They note that in some cases the PvCO2 was lower than the PaCO2. The meta-analysis had considerable heterogeneity between studies which limits the reliability of its conclusions.

HCO3

    Good correlation
    Mean difference −1.41 mmol/L (−5.8 to +5.3 mmol/L 95%CI)

Lactate

    Dissociation above 2 mmol/L
    Mean difference 0.08 (-0.27 – 0.42 95%CI)

Base excess

    Good correlation
    Mean difference 0.089 mmol/L (–0.974 to +0.552 95%CI)

PO2

    PO2 values compare poorly
    arterial PO2 is typically 36.9 mm Hg greater than the venous with significant variability (95% confidence interval from 27.2 to 46.6 mm Hg) (Byrne et al, 2014)
   

DIABETIC KETOACIDOSIS

VBG can be used to guide management in preference to ABG (Ma et al, 2003)

    VBG correlated with ABG well
    Mean difference in pH -0.015 ± 0.006 units [95% CI]
    ABG pH changed treatment or disposition in 2.5% cases compared to VBG pH

WHEN IS ABG NECESSARY?

ABG may be necessary:

    to accurately determine PaCO2 in severe shock
    to accurately determine PaCO2 if hypercapnic (i.e. PaCO2 >45 mmHg)
    to accurately determine arterial lactate >2mM (rarely necessary)

In general, ABGs rarely need to be performed unless an arterial line is in place (for arterial blood pressure monitoring and ease of blood sampling)

References and Links

1. Byrne AL, Bennett M, Chatterji R, Symons R, Pace NL, Thomas PS. Peripheral venous and arterial blood gas analysis in adults: are they comparable? A systematic review and meta-analysis. Respirology. 2014 Jan 3. doi: 10.1111/resp.12225. [Epub ahead of print] PubMed PMID: 24383789. [Free Full Text]

2. Kelly AM. Review article: Can venous blood gas analysis replace arterial in emergency medical care? Emerg Med Australas. 2010 Dec;22(6):493-8. doi: 10.1111/j.1742-6723.2010.01344.x. Review. PubMed PMID: 21143397. [Free Full Text]

3. Kelly AM, McAlpine R, Kyle E. Venous pH can safely replace arterial pH in the initial evaluation of patients in the emergency department. Emerg Med J. 2001 Sep;18(5):340-2. PMID 11559602

4. Koul PA, Khan UH, Wani AA, Eachkoti R, Jan RA, Shah S, Masoodi Z, Qadri SM, Ahmad M, Ahmad A. Comparison and agreement between venous and arterial gas analysis in cardiopulmonary patients in Kashmir valley of the Indian subcontinent. Ann Thorac Med. 2011 Jan;6(1):33-7. PMID 21264169

5. Ma OJ, Rush MD, Godfrey MM, Gaddis G. Arterial blood gas results rarely influence emergency physician management of patients with suspected diabetic ketoacidosis. Acad Emerg Med. 2003 Aug;10(8):836-41. PMID 12896883

6. McCanny P, Bennett K, Staunton P, McMahon G. Venous vs arterial blood gases in the assessment of patients presenting with an exacerbation of chronic obstructive pulmonary disease. Am J Emerg Med. 2012 Jul;30(6):896-900. PMID 21908141

7. Middleton P, Kelly AM, Brown J, Robertson M. Agreement between arterial and central venous values for pH, bicarbonate, base excess, and lactate. Emerg Med J. 2006 Aug;23(8):622-4. PMID16858095

8. Tricia M McKeever et al : Using venous blood gas analysis in the assessment of COPD exacerbations: a prospective cohort study –

Thorax doi:10.1136 thoraxjnl-2015-207573

Web resources:

1. ALIEM — Paucis Verbis Card: VBG versus ABG (2012)

2. FET — Venous and Arterial Blood Gas Analysis in the ED by Anne-MArie Kelly (2012)

3. FET — Can a Venous Blood Gas Substitue for an Arterial Blood Gas by Jason Chu (2013)

4. LITFL – VBG versus ABG

Posted from WordPress for Android – Google Nexus 5
https://www​.facebook.com/MedicalGeek
https://in.groups.yahoo.com/neo/groups/only4medical/

Critical Care

NHLBI ARDS Network TRIALS

Leave a comment

The NHLBI ARDS Network enrolled 5,527 patients across ten randomized controlled trials and one observational study.

ARDS NET TRIAL

Ketoconazole for ALI/ARDS (KARMA)

Mar 1996 – Feb 1998

The first clinical trial completed by the Network was a randomized, controlled trial of Ketoconazole versus placebo in patients with acute lung injury and ARDS. It enrolled 234 participants.

Lower Tidal Volume Trial (ARMA)

Mar 1996 – Jul 1999

The ARMA study was a randomized, controlled multi-center 2×2 factorial study consisting of a drug treatment (Ketoconazole vs. placebo) and a ventilation strategy (6ml/kg tidal volume vs. 12ml/kg tidal volume). It enrolled 861 participants.

Lisofylline for ALI/ARDS (LARMA)

Feb 1998 – Jun 1999

The LARMA study was a randomized, double-blind, placebo-controlled multi-center study with where each patient was randomized between Lisofylline and Placebo. It was designed to test whether the administration of lisofylline early after the onset of ALI or ARDS would reduce mortality and morbidity. It was also conducted in a 2×2 factorial in the later stages of the ARMA trial. It enrolled 236 participants.

Late Steroid Rescue Study (LaSRS)

Aug 1997 – Nov 2003

The late phase of ARDS is often characterized by excessive fibroproliferation leading to gas exchange and compliance abnormalities. The objective of the LaSRS study was to determine if the administration of corticosteroids, in the form of methylprednisolone sodium succinate, in severe late-phase ARDS, would have a positive effect on this fibroproliferation, thereby reducing mortality and morbidity. It enrolled 180 particpants.

Higher vs Lower PEEP (ALVEOLI)

Nov 1999 – Mar 2002

The ALVEOLI study was a prospective, randomized, controlled multi-center trial. The objective was to compare clinical outcomes of patients with acute lung injury (ALI)and acute respiratory distress syndrome (ARDS) treated with a higher end-expiratory lung volume/lower FiO2 versus a lower end-expiratory lung volume/higher FiO2 ventilation strategy. It enrolled 549 participants.

Fluid and Catheter Treatment Trial (FACTT)

Jun 2000 – Oct 2005

The FACTT study was a prospective, randomized, multi-center trial evaluating the use of a pulmonary artery catheter versus a less invasive alternative, the central venous catheter, for the management of patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). It was combined in a 2×2 factorial design with a second study contrasting a conservative and a liberal fluid management strategy in patients with ALI or ARDS. It enrolled 1000 participants.

Albuterol for the Treatment of ALI (ALTA)

Aug 2007 – Sep 2008

A prospective, randomized trial of Aerosolized Albuterol vs. Placebo to test the safety and efficacy of aerosolized beta-2 adrenergic agonist therapy for improving clinical outcomes in patients with acute lung injury. It enrolled 282 participants.

Early vs. Delayed Enteral Nutrition (EDEN)

Nov 2006 – Mar 2011

Prospective, Randomized Trial of initial trophic enteral feeding followed by advancement to full-calorie enteral feeding vs. early advancement to full-calorie enteral feeding. It enrolled 1000 participants. This trial was originally run as a 2×2 factorial trial with the Omega trial. When the Omega arm was stopped for futility, the EDEN arm continued to completion.

Omega Nutrition Supplement Trial (Omega)

Nov 2006 – Apr 2009

@TODO A trial of omega-3 fatty acid, gamma-linolenic acid, and anti-oxidant supplementation vs. a comparator. It enrolled 272 participants. It was run as a part of a 2×2 factorial trial with the EDEN study. The Omega arm was stopped for futility.

H1N1 Registry

Nov 2009 – Jun 2010

A registry created in collaboration with the CDC to track severe cases of H1N1. It enrolled 683 participants.

Rosuvastatin vs. Placebo (SAILS)

Mar 2010 – Sep 2013

Statins for Acutely Injured Lungs from Sepsis is a trial of rosuvastatin versus placebo comparator for the treatment of patients with ALI or ARDS. It enrolled 745 participants.

Critical Care

Antibiotic lock therapy : Summary

Leave a comment

Antibiotic lock therapy (ALT) involves instillation of a concentrated antibiotic solution into the catheter lumen with the intention of achieving a drug level high enough to kill sessile bacteria within the biofilm of the catheter. Anticoagulants are often included in the solution and are thought to facilitate antibiotic penetration into microbial biofilm.

For clinically stable children and adults with infections of long-term tunneled central venous catheters and ports due to coagulase-negative staphylococci, gram-negative rods, and vancomycin -sensitive enterococci in whom a decision is made to salvage the catheter, we suggest ALT in conjunction with systemic antibiotics rather than systemic antibiotics alone ( Grade 2B ).

Catheter management options for catheter-related bloodstream infections (CRBSI) include removal, salvage, and exchange over a guidewire. Catheter salvage should not be attempted in the following circuminfections

-Complicated CRBSI
-Severe sepsis or hemodynamic instability
-Persistent bacteremia despite 72 hours of appropriate antibiotic therapy
-Infections caused by S. aureus, P. aeruginosa, fungi, mycobacteria, Bacillus species, Micrococcus species, or Propionibacteria
-Tunnel infections, port abscesses, or exit site infections

Cefazolin , vancomycin , ceftazidime , and gentamicin are commonly used in ALT and are stable in solution with heparin over a prolonged period of time ( see table ). Specific antibiotic selection for ALT should be guided by culture and susceptibility results when available. We favor a dose in which the final antibiotic concentration exceeds the minimum inhibitory concentration (MIC) of the organism by at least 10administered

image

For patients receiving ALT, we typically include heparin in the antibiotic lock solution unless there is a contraindication to heparin (eg, heparin-induced thrombocytopenia). For patients with contraindications to heparin, only antibiotics that have been shown be stable and effective when used alone should be administered

Fungal superinfection, systemic toxicities of antibiotics or anticoagulants included in lock solutions, and emergence of antibiotic resistance with failure are potential but not frequently reported adverse effects.

Antibiotic lock solutions should be administered in an amount sufficient to fill and dwell in the catheter lumen when the catheter is not in use. Depending on the need for access, dwell times can range from four to six hours to three days, after which the solution should be withdrawn and discarded.

Infected catheters should be removed in patients who remain febrile 48 to 72 hours after initiating ALT, who have persistently positive blood cultures 72 hours after initiating ALT, or who have signs of sepsis, hemodynamic instability, or metastatic infection.

Posted from WordPress for Android – Google Nexus 5
https://www​.facebook.com/MedicalGeek
https://in.groups.yahoo.com/neo/groups/only4medical/

Critical Care, Guidelines

CPR Guidelines – Adults

Leave a comment

AHA CPR Guidelines 2010

NOTE: Sequence has changed from airway, breathing, chest compressions (ABC) to chest compressions, airway, breathing (CAB) per the 2010 AHA Guidelines

Untrained lay rescuers should do compression-only CPR; whereas, trained lay rescuers and healthcare providers (HCP) should include compressions and breathing

Compressions

check pulse at carotid
compression landmarks: lower half of sternum, between nipples
compression method: heel of one hand, other hand on top
compression depth: at least 2 inches (5 cm)allow complete chest recoil after each compression
compression rate: at least 100/min compression-ventilation ratio: 30:2 (1 or 2 rescuers)
minimize interruptions in compressions; limit interruptions to <10 seconds avoid excessive ventilation

Airway

head tilt-chin (HCP suspected trauma: use jaw thrust)

Breathing

ventilation with advanced airway: 1 breath every 6-8 seconds (8-10 breaths/min)
asynchronous with chest compressions
about 1 second per breath
visible chest rise

Defibrillation

attach and use AED as soon as available
minimize interruptions in chest compressions before and after shock
resume CPR beginning with compressions immediately after each shock