Intraosseous Access is associated with lower survival in out of hospital cardiac arrest

Takahisa Kawano,  Brian Grunau,  Frank X. Scheuermeyer  et el published a study comparing  intraosseous versus intravenous vascular access on survival as well as neurological outcome in out of hospital cardiac arrest in Annals of emergency medicine.

BACKGROUND

Intraosseous access (IO) was first pioneered by Drinkler and colleagues in 1922 but it became popular as a substitute to peripheral IV in 1980s.  Pediatricians started using this route in frequent emergency situations like hypovolemic shock in dehydrated infants.  In adults, IO access is less frequently used. However, it has been recommended for about 15 years in the case of failure of peripheral IV line placement during resuscitation.  IO access could technically allow for fluid resuscitation as well as high-volume drugs with efficacy similar to an IV access. It is also recommended in combat situations. 

It has been hypothesized that  compared with intravenous access, the intraosseous route may minimize interruptions in cardiopulmonary resuscitation (CPR), decrease time to vascular access, and potentially improve outcomes.

Earlier, a trial by Reades, Studnek et el showed that IO access had highest first-attempt success for vascular access
and the most rapid time to vascular access during out-of-hospital cardiac arrest.

STUDY

The aim of this study was to assess the association between the vascular access route (intraosseous and intravenous) and outcomes after out-of-hospital cardiac arrest.

METHODS

This was a secondary analysis of the Resuscitation Outcomes Consortium Prehospital Resuscitation Using an
Impedance Valve and Early Versus Delayed (PRIMED) study.  The primary outcome was favorable neurologic outcome on hospital discharge (modified Rankin Scale score 3).   Secondary outcomes included return of spontaneous circulation and survival to hospital discharge.

WHERE

PRIMED study was conducted in 7 sites in the United States (Pittsburgh, PA; Dallas, TX; Portland, OR [2 sites];
Birmingham, AL; Seattle/King County, WA; and San Diego, CA) and 3 sites in Canada (Toronto Rescu sites, Ontario;
Vancouver, British Columbia, and Ottawa/OPALS sites, Ontario).

PATIENTS

Of 13,155 included out-of-hospital cardiac arrests, 660 (5.0%) received intraosseous vascular access.  These were compared with patients who received intravenous access using  multivariable logistic regression, adjusting for
age, sex, initial emergency medical services
recorded rhythm (shockable or nonshockable), witness status, bystander cardiopulmonary resuscitation, use of public automated external defibrillator, episode location (public or not), and time from call to paramedic scene arrival.
Study included total of 17445 patients but 4290 patients were excluded based on age <17, no vascular access, patients with both IV and IO, EMS only tried IV or IO, patients with either IV or IO in which EMS failed to obtain alternative.

RESULTS

Intraosseous access was negatively associated with the probability of return of spontaneous circulation, survival,
and favorable neurologic outcome at hospital discharge. This relationship was consistent after adjustment for baseline characteristics and for selection bias and unmeasured confounders by propensity score-matching techniques.
In the intraosseous group,10 of 660 patients (1.5%) had favorable neurologic outcome compared with 945 of 12,495 (7.6%) in the intravenous group.

POSSIBLE EXPLANATIONS

  1.  Actual effectiveness of several cardiac resuscitation medication by this route is unclear; drugs may remain stagnant in bone marrow, especially without a fluid bolus of 20 mL or pressure bags.
  2. During hemorrhagic shock, bone marrow blood flow decreases by 70% to 80% and  bone blood flow during CPR might be equally or more reduced. 
  3. Epinephrine is known to both reduce bone marrow flow rate and increase bone vascular resistance.
  4. In this study,  flow rate through intraosseous access (11.1 mL/min) was significantly slower than through intravenous access (18.4 mL/min).
  5. It is possible that resuscitative drugs are distributed slower through the intraosseous route than the intravenous route, and some may be trapped in bone marrow.
  6. Animal study has shown that  the mean atrial concentration of drugs through the tibial intraosseous route
    was 53% of the drug concentration as delivered though the central venous route.
      It is also slower to reach(60 vs 43 seconds).

BOTTOMLINE

Intraosseous access has been advocated as an alternative to intravenous approach in setting of cardiac arrest, however, this study shows that intraosseous access was associated with lower survival and poor neurologic recovery. Further research is required to determine the effectiveness of interosseous vascular access and cardiac arrest situations.

IO insertion technique can be seen here.

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