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January 11, 2011

Improving post-resuscitation care

So you got a pulse, now what? Return of spontaneous circulation (ROSC) after out-of-hospital cardiac arrest has improved over recent years, but is still lower than we would like. The same goes for long-term functional survival after ROSC.

Once you get a pulse, what you do next may determine your patient's ultimate survival. And it may be about doing less, not more. Hippocrates is considered the father of medicine and wrote long ago that we are "to do good or to do no harm." (Epidemics, Book 1).

Is more better?
You know the old saying, "If a little is good, more is better" — not so if we're talking about post-resuscitation oxygen therapy. With ROSC, oxygen is suddenly delivered to previously oxygen-starved cells and results in the production of toxic substances that can damage or destroy cells(1).

An overabundance of oxygen through our efforts in the field may increase that production. To minimize this process, we should titrate post-resuscitation oxygen therapy; get the oxygen level in the normal range without flooding the system with oxygen.

One recommendation is to keep the oxygen saturation from 94 percent to 96 percent(2); however getting it anywhere below 100 percent but above 93 percent would be preferable to oxygen flooding. And that can be accomplished by decreasing oxygen flow until your 'O2 sat' reaches target levels.

Growing role of prehospital oximetry
Prehospital oximetry is becoming as common as using a blood pressure cuff. And cost is not a major barrier. As with any medical monitoring device, it must be utilized and interpreted correctly and recognized as an adjunct to your direct observation of the patient.

Advanced airway devices
The same oxygen saturation rule applies if you utilize an advanced airway device, plus the patient should be connected to capnography to measure carbon dioxide and confirm adequate ventilation and prevent problems from over-ventilation or under-ventilation.

You must try to avoid high pressure ventilation which can damage the lungs, a problem your patient can live without. The objective is to provide the lowest ventilation pressure with the right rate of ventilation to maintain adequate but not excessive oxygenation and a normal carbon dioxide level.

Blood pressure and optimal perfusion pressure
Does our patient with ROSC require a normal blood pressure? Is there an optimal perfusion pressure that will maintain adequate blood flow to the brain and other organs without adding excessive strain on the potentially damaged heart? Unfortunately this has yet to be determined.

The best advice seems to be to treat obvious hypotension by raising the perfusion pressure to a systolic blood pressure in the 90-100mmHg range. Intravenous fluid bolus therapy with isotonic fluid should be accompanied by frequent monitoring for pulmonary edema. If the pump is damaged and cannot produce an adequate blood pressure, medication such as dopamine or dobutamine may be helpful.

You may also find your post-ROSC patient is hypertensive. An elevation in blood pressure may be a response to an increase in intracranial pressure due to prolonged hypoxia. And it may be a beneficial reflex that provides extra pressure to push the blood past the increased intracranial pressure and into the cerebral circulation(2). Remember, a resuscitated heart without a resuscitated brain equals lousy quality of life.

If you have a cardiac monitor, put it on and keep it on for early recognition and treatment of dysrhythmias. And if you are ECG capable, get a post-resuscitation 12 or 15 lead view of the heart's electrical system; if a ST Elevation Myocardial Infarct (STEMI) caused the arrest, it may still be evolving and that requires early recognition and treatment. Remember that most out-of-hospital sudden cardiac deaths are due to cardiac ischemia.

Maintaining optimal physiological boundaries
How about serum glucose levels? Abnormal blood sugar levels may produce problems for any patient, but for the resuscitated cardiac arrest patient it can adversely affect outcome if left untreated(2).

 Again (and again, and again) the goal is to maintain optimal physiological boundaries. If you have the ability to obtain a finger stick blood sugar in the field, at a minimum you can provide advanced notice to the receiving facility that the patient has an abnormal glucose.

If the blood sugar is low, you may administer oral glucose if the patient is conscious or if unconscious an intravenous glucose solution depending on your provider level. Whatever the chosen route, you should administer small doses and frequently check the blood sugar until you obtain an acceptable non-fasting serum glucose level (60 to 140mg/dl), and try not to overshoot. For hyperglycemia, intravenous fluid administration can decrease sugar levels but keep in mind the potential for fluid overload and check sugars frequently.

For every vital parameter discussed so far our goal is clear: stay within the normal physiological range…until this one. Therapeutic hypothermia has a proven track record in patients with ROSC who do not regain consciousness. Dropping the temperature a few degrees for a period of time improves outcome. What we don't know for sure is whether initiating the cooling process in the field or delaying until arrival at the receiving facility makes a difference in outcome(3). Further research will help define this question.

Out-of-hospital medical practitioners (you) now have another opportunity to improve outcomes by carefully monitoring the post-resuscitation patient and providing the optimum level of intervention. Your goal is an ancient one, strive to do good patient care and if you can't do good, then do no harm.

References
1. Kilgannon JH, Jones AE, Shapiro NI, et al. Association Between Arterial Hyperoxia Following Resuscitation From Cardiac Arrest and In-Hospital Mortality. JAMA. 2010;303(21):2165-2171.

2. Neumar RW, Nolan JP, Adrie C, Aibiki M, Berg RA, Böttiger BW, Callaway C, Clark RSB, Geocadin RG, Jauch EC, Kern KB, Laurent I, Longstreth WT Jr, Merchant RM, Morley P, Morrison LJ, Nadkarni V, Peberdy MA, Rivers EP, Rodriguez-Nunez A, Sellke FW, Spaulding C, Sunde K, Vanden Hoek T. Post–cardiac Arrest Syndrome: Epidemiology, Pathophysiology, Treatment, and Prognostication: A Consensus Statement From The International Liaison Committee on Resuscitation (American Heart Association, Australian and New Zealand Council on Resuscitation, European Resuscitation Council, Heart and Stroke Foundation of Canada, InterAmerican Heart Foundation, Resuscitation Council of Asia, and the Resuscitation Council of Southern Africa); the American Heart Association Emergency Cardiovascular Care Committee; the Council on Cardiovascular Surgery and Anesthesia; the Council on Cardiopulmonary, Perioperative, and Critical Care; the Council on Clinical Cardiology; and the Stroke Council. Circulation. 2008;118: 1–32.

3. Bernard SA, Smith K, Cameron P, Masci K, Taylor DM, Cooper J, Kelly AM, Silvester W. Induction of Therapeutic Hypothermia by Paramedics After Resuscitation From Out-of-Hospital Ventricular Fibrillation Cardiac Arrest A Randomized Controlled Trial. Circulation. 2010;122:737-742.

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