Field Techniques for Resuscitation of Foals

I. Introduction

Cardiopulmonary cerebral resuscitation (CPCR, previously called CPR) is the restoration of spontaneous circulation (a heartbeat) with the preservation of neurologic (brain) function. The most common and immediate case requiring CPCR is an asphyxiated foal. Clinical signs that resuscitation is needed for a newborn foal include the absence of breathing; irregular gasping; respiratory rate less than 10 breaths/minute; irregular or absent heart rate, or one less than 40 beats/minute; muscle flaccidity; and the lack of a response to tactile stimulation. Foals delivered by cesarean section often need CPCR. It is important to always assess the glucose levels on a foal that may have arrested because hypoglycemia is one of the most common causes requiring resuscitation.

II. Materials and methods

Preparation 

There will be few moments in your veterinary career when preparation is more vital than when dealing with a compromised neonate. The 5 P’s of Prior Planning Prevents Poor Performance rings true in this medical situation. The goal of CPCR is the restoration of spontaneous circulation with preservation of neurological function. Successful treatment is defined as the return or establishment of normal function, not just the restoration of spontaneous circulation and survival to discharge. Many veterinarians feel inadequate because of their low success rates for CPCR. We must, however, realize the odds for survival after CPCR in humans are also low, with 6% survival from out of hospital arrests to 15% success during in hospital arrests.^1-4

It is of the utmost importance to also educate clients about providing basic CPCR because the veterinarian may not be present at foaling.

All emergency supplies should be organized into a dedicated, easily accessible and portable “resuscitation kit”.

The “resuscitation kits” must be organized and stocked with all the medications and supplies needed to provide emergency resuscitation (Fig. 1). The resuscitation kit should include the following items:

• Full Oxygen tank (OPTIONAL)
• Ambu resuscitator with 3 ft corrugated tubing tail piece
• Endotracheal tubes (7,8 and 9 mm for foals)
  • 10 ml syringe to inflate the cuff
• Fluids
  • Hydroxyethyl starch volume expander
  • Hypertonic Saline
  • Isotonic polyionic fluids (Lactated Ringer’s Solution, etc.)
• Fluid Administration sets
  • Include a pressure bag for administration of fluids
• Fluid Additives
  • 50% Dextrose
  • 50% Magnesium Sulfate
• Oxygen Supplies
  • Tubing
  • Nasal cannula
  • Humidifier and connectors Intravenous Catheters
• Feeding Tubes
  • 24 Fr , 60 inches long (Harris Flush Tube or Stallion Urinary Catheter)
• Sedatives for the mare
  • Xylazine
  • Detomidine
  • Romifidine
• Tackle box with emergency medications already drawn up and labeled
  • Epinephrine 1 mg/ml
    • Dose: .01 to .02 mg/kg IV (50 kg
      Foal: 0.5 to 1 ml IV at 3 minute increments if until return of circulation)
    • Have three 1 cc syringes drawn up
  • Doxapram 20 mg/ml (Respiratory stimulant)
    • Dose: 0.5 mg/kg IV
    • Have two 1 cc syringes drawn up
• Glycopyrrolate 0.2 mg/ml (Anticholinergic agent used to treat bradyarrhythmias)
  • Dose: .0022 mg/kg IV (50 kg foal: 0.5 cc IV)
  • Have two 1cc syringes drawn up
• Yohimbine (Alpha 2 adrenergic antagonist- Used for dystocias or C-sections in which the mare is heavily sedated with an alpha₂adrenergic agonist)
  • Dose 0.75 mg/kg IV
  • Have bottle available
    • Give 0.5 to 1.5 cc IV per 100 pounds
• Naloxone (Narcotic antagonist- Used in C-Section foals to help reduce the endogenous opioids that cause mental depression)
  • Dose 5 mg IV
  • Have two 4mg bottle available
• Prednisolone sodium succinate
  • Dose 2 mg/kg IV
  • Have three 100 mg bottles available
• Lidocaine 2% (For ventricular tachycardia)
  • Dose 1 mg/kg IV
• Furosemide (Diuretic- Use for pulmonary edema) 
  • Dose 1 mg/kg IV
  • Have bottle available
• Umbilical Clamp
  • Nolvasan umbilical dip
• Gloves (sterile and non-sterile)
• Eye lubricant
• Suture Kit
  • Scalpel blades
• Tracheostomy tubes
  • 5 mm I.D and 7.3 MM O.D. 
  • 7 mm I.D and 10 MM O.D.

The concept of the ABCs is important: A—assessment/airway; B--breathing; C--circulation.
 

Assessment/Airway

The first step is to clear the airway and remove membranes and mucus from the nose. If this does not work, the airway can be suctioned with a bulb syringe (like a turkey baster) or a 60-mL syringe and rubber tubing. Suctioning should only be performed if meconium is present and then only for less than 10 seconds as it may cause bradycardia and cardiac arrest via vagal reflexes.

Don't worry about suctioning the mouth because horses are obligate nasal breathers. Vigorous rubbing with dry towels can provide tactile stimulation and initiate breathing. Slapping, shaking, spanking, and holding the foal upside down are strongly advised against in horses (and humans). The foal should start to have a regular breathing pattern within 30 seconds of birth. It is not unusual for foals to have arrhythmias for the first 10-15 minutes of life. In one study, 50 newborn foals were evaluated electrocardiographically during their adaptive period, immediately after birth. In 48 foals there were paroxysmal arrhythmias or mixed arrhythmias. The most common arrhythmias were sinus arrhythmia including wandering pacemaker (32/50) and atrial premature contractions (30/50). The others observed were atrial fibrillation (15/50), ventricular premature contractions (10/50), partial atrioventricular block (7/50), ventricular tachycardia (4/50), atrial tachycardia (3/50) and idioventricular rhythm (1/50). The duration of the arrhythmias was approximately 5 min, and in all cases the arrhythmia disappeared within 15 min of birth. With the exception of 2 cases, all foals have continued to grow and develop normally. These arrhythmias are considered normal physiological processes in newborn Thoroughbred foals during the adaptive period to extra-uterine life. High vagal tone and hypoxemia at birth are probably the main contributing factors.5 Foal that continue gasping for > 30 seconds or are not breathing, have a heart rate of < 50 BPM or do not have a heart beat require immediate resuscitation.

To achieve a patent airway, intubation would be required. Endotracheal tube size range from 7 mm to 12 mm (internal diameter). The largest possible endotracheal tube should be used without damaging the nasal passages and pharynx. For the average 50 kg Thoroughbred foal an 8 mm to 9 mm diameter tube with a length of 55 cm would be ideal. For smaller breeds tubes with a 7 mm diameter would be required. The foal’s head should then be placed in lateral or sternal recumbency. The head should be maximally extended and the endotracheal tube passed ventral and centrally into the ventral meatus and then rotated and advanced slowly into the trachea. If the tube is placed correctly, minimal resistance should be noted when passing the tube into the trachea and expired air can be felt as the thorax is compressed. To minimize the amount of dead space, the tube should be advanced as far as possible with only the end adapter remaining exteriorized from the nostril. If nasotracheal intubation is unsuccessful after 10-15 seconds then orotracheal intubation should be attempted. Orotracheal intubation can, however, result in injury to the oral cavity when the patient starts to awaken and chews on the tube.⁶  [...]