Heart Rate Response to Atropine Doses Less Than 0.1mg IV to Anesthetized Infants
Condition: Bradycardia; Arrhythmias
MeSH terms: Bradycardia
Study type: Interventional
Phase: Phase 4

Summary: 
      An infants heart rate is very important because it ensures that blood is pumped to all organs
      in the body. Heart rate may decrease during anesthesia and surgery, and this is why the
      anesthesiologist will often give a medication to prevent this from happening. The most common
      drug for this purpose is called atropine. The dose of most drugs given to babies is based
      upon the baby's weight, but some believe that the dose of atropine should not be less than
      0.1mg. However there is no evidence to support this minimum dose. A larger dose of atropine
      may cause a very fast heart rate instead. Anesthesiologists routinely dose the atropine based
      upon the baby's weight without regard for a minimum dose.

      The purpose of the present study is to measure the heart rate after doses of atropine in
      neonates and infants who receive less than 0.1 mg.
    

Detailed description: 
      60 infants, ASA physical status I and II, undergoing elective surgical procedures will be
      enrolled after signed informed parental consent.

      All children will be fasted according to institutional guidelines and unpremedicated. After
      arriving in the operating room, EKG, pulse oximeter and blood pressure monitors will be
      applied (Datex-Ohmeda Aisys).

      Anesthesia will be induced with 66% N2O in O2 and 8% sevoflurane. Respiration will be
      supported by a properly sized face mask through which he/she is allowed to breath
      spontaneously. Respiration will continue spontaneously through a facemask at 2 MAC
      sevoflurane in 66% N2O.

      All children will be positioned supine, warmed with a forced air warmer and given 20 ml/kg IV
      balanced salt solution over 30 minutes after the IV has been established. The end-tidal pCO2
      will maintained 35-45 mmHg and oxygen saturation >96%.

      After a 22 or 24G IV cannula is inserted, 0.005 mg/kg atropine will be administered
      intravenously over 5 seconds through a fast-flowing IV and followed by 5 ml of normal saline
      to flush it in through the IV deadspace. The study (ECG recording) period will extend from 30
      seconds before atropine administration to 5 minutes after injection. During this time the
      heart rate and rhythm (through lead II) will be monitored and recorded continuously using an
      analogue interface system. EKG will be recorded on paper continuously for the 330 seconds of
      the study.

      The recording will be analyzed for the heart rate (based on the R-R interval) and arrhythmias
      by a physician blinded to the study. Blinding means that the individual is unaware of the
      hypothesis of the study and what medication was administered to account for any changes in
      heart rate. Bradycardia is defined as a 20% reduction from baseline heart rate while
      tachycardia is a heart rate > 160 beats/minute(6). Any heart rate < 100/minute will be
      considered a bradycardia in this age group. Arrhythmia is any disorder of rhythm or rate
      observed. These will be summarized for each child.

      All heart rate responses will be recorded and reviewed. The time to record the heart rate
      after atropine, which will occur before surgery, will add less than 5 additional minutes to
      the anesthetic since it will overlap the time taken for other surgical preparatory events.

      The blood pressure will be monitored non-invasively immediately before receiving atropine and
      at one and five minutes after it is given.

      The primary outcome is the incidence of bradycardia during the first 5 minutes after atropine
      will be determined by reviewing the electrocardiogram. All continuous data will be reported
      as means +/- standard deviation.
    

Intervention name(s): Atropine
Intervention type(s): Drug
Intervention description(s): intravenous atropine affect on heart rate
Other intervention name(s): atropine sulfate; atropine injection
Intervention MeSH terms: Atropine
Intervention model: Single Group Assignment
Intervention model description: This is a single arm study where a dose of atropine was administered and the ECG recorded.
Masking: None (Open Label)
Primary purpose: Other
Keywords: Atropine; bradycardia; tachycardia