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Fat Emulsion to the Rescue
Lipid emulsion therapy can resuscitate patients who've suffered cardiac collapse after local anesthetic administration.
Linda Chitwood
Publish Date: December 1, 2008   |  Tags:   Anesthesia

After injecting the local anesthetic bupivacaine 0.25% for post-op pain relief, the surgeon reached for a suture to close the wound. But 60 seconds after the injection, the anesthesia provider alerted the team to an ominous development: profound and deadly changes evolving in the patient's cardiac rhythm. With a potentially fatal myocardial event unfolding in front of their eyes, the surgeon flung aside the suture and ripped off the drapes while others called for help. As the code cart crashed through the OR door, monitors began alarming: BP 63/30, ECG V-Tach, then a full cardiac arrest. Advanced cardiac life support (ACLS) was started, and the patient left the ASC for a nearby hospital with chest compressions in progress.

A subsequent case review fingered cardiotoxicity related to bupivacaine as the likely trigger of the arrest. That surgeon never used bupivacaine again. Why? Despite years of safe use, bupivacaine has been associated with a rare but often lethal cardiotoxicity.

The testimony to toxicity
When first introduced decades ago, manufacturers trumpeted this long-acting local anesthetic — at its 0.75% strength — as the premier local anesthetic agent for labor epidurals. Until women started dying, that is. Anesthesia providers and obstetricians discovered that in cases where 0.75% bupivacaine was inadvertently injected intravenously or found its way into the bloodstream, patients who developed bupivacaine cardiotoxicity simply couldn't be resuscitated, despite optimal ACLS protocol efforts.

The industry withdrew that 0.75% strength from the market — leaving the 0.5% and 0.25% concentrations we're familiar with today. (The 0.75% strength is available for ocular blocks only.) Yet it remains true that in cases of severe local anesthetic cardiotoxicity from which a patient can't be resuscitated, bupivacaine is typically the offending agent. Even now we're learning more about bupivacaine's link to cardiac arrests.

In a 2005 presentation to the Anesthesia Patient Safety Foundation, an anesthesiologist described how he performed a popliteal block with bupivacaine on a patient who then went into cardiac arrest. All attempts to resuscitate this patient, who was to have a routine ankle procedure, had failed. Finally he rushed her to the OR across the hall where a cardiopulmonary bypass machine was awaiting a heart patient. After an emergency sternotomy, an hour on bypass and 10 days in the hospital, she survived.

In 2006, Meg Rosenblatt, MD, and others reported on a case of a 58-year-old man undergoing a regional block for shoulder surgery. A cardiac arrest followed the bupivacaine injection, but standard ACLS efforts again proved futile. While a cardiac bypass machine was being readied, the code team injected a fat emulsion, also known as lipid. Within seconds, cardiac rhythm and pulses were restored.

Most facilities don't have a cardiopulmonary bypass machine and team standing by in case a patient experiences local anesthetic cardiotoxicity. And most aren't willing to toss bupivacaine out of their ORs since it works well and is less expensive than alternatives. That means you must be prepared for a potentially fatal event following the use of bupivacaine, or even other local anesthetics.

Your Lipid Resuscitation Kit

Here's what you'll need to easily and inexpensively assemble a fat emulsion kit:

  • a plastic box, labeled, in which to store the supplies
  • fat emulsion 20%, 500ml bag
  • IV tubing
  • two 60ml syringes and needles

In the event of local anesthetic-induced cardiac arrest that is unresponsive to standard therapy, in addition to standard cardio-pulmonary resuscitation, give fat emulsion 20% IV in the following dose regime:

  • fat emulsion 20%, 1.5mL/kg over 1 minute
  • follow immediately with an infusion at a rate of 0.25mL/kg/min
  • continue chest compressions (lipid must circulate)
  • repeat bolus every 3 to 5 minutes up to 3mL/kg total dose until circulation is restored
  • continue infusion until hemodynamic stability is restored; increase the rate to 0.5mL/kg/min if BP declines
  • a maximum total dose of 8mL/kg is recommended

In practice, in resuscitating an adult weighing 70kg:

  • take a 500ml bag of fat emulsion 20% and a 50ml syringe
  • draw up 50ml and give stat IV, x2
  • then attach the fat emulsion bag to an IV administration set (macrodrip) and run it IV over the next 15 minutes
  • repeat the initial bolus up to twice more if spontaneous circulation has not returned
  • store your kit where you perform regional blocks and remember to restock the lipid

— Reprinted with permission from Guy Weinberg, MD (www.lipidrescue.org)

Fend off a fatality with fat
Fat emulsion — you're familiar with it as a mainstay of parenteral nutrition — has proven incredibly efficient at clearing local anesthetics like bupivacaine from the bloodstream, thereby negating its cardiotoxic effects. Recently, fat emulsion (lipid) solutions have also been used to resuscitate patients from accidental and intentional overdoses of other drugs. This is an off-label use of fat emulsion, which is neither marketed nor manufactured for cardiac resuscitation. No controlled human studies have been conducted; clearly researchers can't induce bupivacaine toxicity in humans just to see if a fat emulsion will resuscitate them and prevent fatalities. Conclusive research documenting the optimum or maximum dose in lipid resuscitation isn't available yet, and we don't have final research determining which fat emulsion formulation is the best. That scientific laboratory research is underway by specialists around the world.

Nevertheless, the case reports are impressive. The evidence in human resuscitation is anecdotal at this point, but major scientific journals are documenting this as a breakthrough in resuscitating patients who've suffered cardiac collapse after local anesthetic administration. In fact, the case reports of lives saved are so good that your facility's care might be considered less than optimal if you don't have a fat emulsion kit.

"Fat emulsion should be immediately available in the event of cardiac arrest. There is a substantial amount of robust literature supporting this," says Guy Weinberg, MD, anesthesiologist and professor at the College of Medicine at the University of Illinois in Chicago. "It has proven successful after standard resuscitation efforts have failed."

An IV injection of fat emulsion will likely do no harm to a patient, appears to be incredibly effective, has a long shelf life and is not expensive. Still, fat emulsion therapy doesn't replace accepted ACLS protocols. Dr. Weinberg notes that the first key to successful resuscitation remains aggressive and immediate airway management with oxygenation, but administering the fat emulsion ASAP is critical.

Many providers reduce the possibility of a bupivacaine-induced cardiac arrest by using another agent such as ropivacaine, especially in patients with a significant cardiac history. However, due to its higher cost, ropivacaine isn't likely to replace bupivacaine in your clinical area soon.

Construct a kit
See "Your Lipid Resuscitation Kit" on page 53 to easily and inexpensively assemble an emergency fat emulsion kit. You need this antidote if your facility administers regional anesthesia or uses bupivacaine. Many facilities keep a kit in each OR or a location where local anesthetics are injected and regional blocks are performed. Although any standard fat emulsion reportedly will do, most case reports mention Intralipid 20%. A 500ml bag costs about $54. A hospital pharmacist can provide you with the fat emulsion, and you've already got the other supplies (IV tubing, syringes). Read more about the kit, case reports and Dr. Weinberg's resuscitation protocols at lipidrescue.org.

The steps that you can take to orchestrate good outcomes and reduce fatalities when a cardiotoxic event develops in your outpatient facility are simple. Remember to store your kit where regional blocks are performed, and rest easy tonight knowing you're better prepared to prevent a fatality tomorrow.