Tips for puppy resuscitation (Proceedings)

Neonatal survival

When puppies and kittens are born, they do not normally require assistance or resuscitation to survive. However, when neonates are stressed during parturition and the periparturient period, morbidity and mortality increase. Timely, effective intervention is required to successfully resuscitate a stressed neonate.

Puppy and kitten mortality rates vary from 9-26%. Neonates that fail to survive to weaning are most commonly stillborn or die within the first three days of life. Factors implicated in perinatal deaths include prematurity, in utero infection, anatomic birth defects, birth trauma/dystocia, low birth weight, inadequate nutrition, maternal neglect, and environmental stresses. Neonatal survival is optimized when breeders have good husbandry practices. Prospective planning includes genetic screening of the prospective dam and sire, ensuring that that dam is healthy at the time of breeding and throughout gestation, managing labor and delivery to reduce stillbirths, controlling parasitism and reducing infectious disease, preventing injury and environmental exposure, and optimizing nutrition of the dam and neonates.

The veterinarian should adopt a pro-active attitude and become involved long before presentation of a critical neonate. Client education in the prebreeding, breeding, prenatal, parturient and postpartum periods can increase neonatal survival, first by facilitating breeders to control or eliminate factors contributing to puppy and kitten morbidity and mortality and second empowering breeders with early warning signs so that veterinary intervention, should it become necessary, is timely.

Veterinarians often need to treat stressed and depressed neonates following dystocia and Caesarian section of the dam. In this situation, the primary causes of fetal depression are hypoxia and anesthesia.

Neonatal hypoxia

Neonates do not respond to hypoxia in the same manner as adults. In contrast to adults, hypoxic neonates respond with a decrease in heart and respiratory rates, presumably as a protective response to low pO2. This compensatory response allows the neonate to survive a longer exposure to hypoxia than would an adult.

Baroreceptor reflexes are not present, nor is sympathetic innervation of the heart complete during the first 4 days of life. So bradycardia in the neonatal period is not vagally mediated. Bradycardia IS indicative of myocardial hypoxia and/or hypothermia. The heart rate in a neonate with a body temperature of 96°F is 200-250 bpm (beats per minute). Be aware that severely hypoxic puppies may have heart rates in the expected range for adults of their breed. If the rectal temperature drops to 70°F, the heart rate decreases to 40-50 bpm. However, the hypothermia protects neonates from ischemic brain injury that accompanies cardiovascular failure.

Administration of chronotropic agents is, at best controversial. Parasympatholytic agents such as atropine will only exacerbate cardiac hypoxemia via increasing oxygen consumption and demand. The more appropriate treatment for neonatal bradycardia is to supplement oxygen and assist ventilation, if necessary. Remember that atropine crosses the placenta while glycopyrrolate does not. This is important when considering choice of medications to be administered pre-or intra-operatively to a dam undergoing a caesarian section delivery.

Hypoxemia in the neonate may result in life threatening sequelae such as septic shock due to bacterial translocation despite a lack of mucosal lesions. It is vital that the environment be kept free of airway irritants and oxygenation is adequate.

If you choose to provide services that require resuscitation of neonates, you will need an oxygen source. If you do not have a second anesthesia machine that can be used for oxygen administration, an oxygen concentrator is an inexpensive oxygen delivery system. An oxygen concentrator concentrates room air to >95% oxygen.

Neonatal hypothermia

Unlike their homeothermic adult counterparts, neonates are poikilothermic and are unable to regulate their own body temperature. They can lose heat through evaporation, conduction, radiation and convection and they cool quickly. Shivering and vasoconstrictive reflexes are not yet functional. However, they have well developed behavioral heat seeking responses which enable them to maintain a stable rectal temperature providing sources of heat are available.

Prevention of hypothermia in neonates is extremely important. Without a heat source, hypothermia ensues and resuscitative measures lose their effectiveness. Due to incomplete maturity of the autonomic nervous system, the neonate is less able to respond to physiological stress. Physiological responses noted during hypothermia include bradycardia, cardiovascular failure, neuronal injury, and ileus. Body temperature is known to have a dramatic effect on gastrointestinal movement in the neonate. At rectal temperatures below 94°F, ileus develops. As ileus progresses, the willingness to nurse decreases and the necessity for tube feeding puppies increases. Inherent to the tube feeding process is the risk for aspiration and subsequent development of pneumonia.

Normal rectal temperatures in the puppy are 95 - 99°F (week 1), 97 - 100°F (weeks 2 and 3) and by weaning rectal temperatures approach that of the adult. The challenge is to maintain the body temperature of the neonates without overheating the dam.

Neonatal resuscitation

1. Be prepared. Keep necessary equipment and supplies together and readily accessible. The most important "supply" is the resuscitator. Have an adequate number of adequately trained personnel available. With routine deliveries, one person per two puppies is recommended. For Caesarian section deliveries, especially when the neonates are known to be bradycardic and stressed, it is ideal to have one skilled person available to resuscitate each puppy. Perform a term gestation radiograph to determine the number of puppies to be delivered and to evaluate the potential for fetal-maternal size mismatch.

2. Effective neonatal resuscitation requires multi-tasking. Efforts to correct or maintain body temperature, clear the airway and stimulate breathing must all be performed simultaneously.

3. Prevent hypothermia. For Caesarian section deliveries, keep the dam warm during surgery and warm IV fluids as they are being administered. Prepare a warmed incubator or box to house puppies once they are breathing. Immediately upon delivery, the neonate should be dried off with a dry towel. Towels that have become moistened with amniotic fluid should be replaced with warm, dry towels. Vigorous rubbing aids in drying the puppy and stimulates breathing. Options for warming systems include infant incubators (set to 90°F/32°C and 50-60% humidity), circulating hot water or hot air heating pads, warm water bottles, or Snuggle Safes™. Contact surfaces are covered with towels. When neonates have become chilled and rapid warming is necessary, submersion of the puppy up to its neck in warm water has been reported.

4. Clear the airway. Remove any fetal membranes covering the nose and mouth. Suction the nose and mouth. A De-Lee mucous trap is useful for this purpose. Healthy neonates normally cry and spontaneously clear their own airways. Stronger suction methods are avoided due to the potential for injury to the airway, and for vagally-mediated bradycardia and laryngospasm. Vagal (parasympathetic) cholinergic innervation to the respiratory system is present at birth, in contrast to sympathetic innervation which is incomplete at birth. "Swinging" or "slinging" of puppies is no longer advocated due to the risk for injury: dropping of the puppy, cerebral hemorrhage from the centrifugal forces, aspiration of stomach contents.

5. Stimulate breathing. Rubbing of the genital or umbilical region of the neonate induces reflex respiration in the first 3 days after birth and may be clinically used to stimulate respiration. Normal respiratory rate in the neonate is low, ranging from 10 – 18 breaths per minute during the first week, despite a high metabolic oxygen demand. The mechanisms that control respiratory function (carotid body chemoreceptors) in the newborn develop well before birth but require maturation in the post natal period. The amount of work and pressure that is required by a neonate to maintain tidal breathing is increased as compared to that of the adult due to the high compliance of the chest wall. Therefore, neonates are highly susceptible to the development of hypoxemia and/or jeopardized ventilation and gas exchange due to the immaturity of chemoreceptor responses to hypoxia and chest wall construction.

If the neonate does not immediately start to breath within seconds of delivery, an attempt to expand the lungs should be made. This can be done by inserting the puppy's mouth and nose in a securely fitting face mask and applying 20-30 cm H2O pressure. Alternatively, the resuscitator can cover the mouth and nose of the neonate with his/her own mouth and administer positive pressure puffs of air in "mouth to snout" fashion. Care must be taken to avoid excessive pressure. Holding the neonate's head in extension minimizes the amount of air forced into the stomach. If the neonate is still not breathing spontaneously, then an attempt should be made to intubate the neonate and repeat lung expansion attempts incrementally up to 30-60 cm H2O. Insertion of a 25-gauge needle into the nasal philtrum (Renzhong acupressure point JenChung, GV26) can also be used to stimulate breathing.

6. Support ventilation with oxygen therapy. Oxygen can be supplied via face mask with an anesthesia machine. Be aware that plastics in the tubing of anesthetic machines can retain residual inhalant anesthetic if the machine has seen recent use. Oxygen concentrators can deliver 95% O2 from room air. If oxygen support is needed long-term, inspired oxygen should not exceed 40-60%, as acute respiratory distress syndrome or retrolental fibroplasias could occur.

7. Cardiovascular support. As discussed, bradycardia in neonates is almost always due to myocardial hypoxia. Therefore, treatment is directed at restoring normal oxygen saturation to the myocardium. If bradycardia persists following appropriate measures to clear the airway, provide ventilatory support and the warm the neonate, then cardiac massage is begun. In most breeds, lateral chest compressions are performed with the thumb and forefinger at a rate of 1-2 beats/sec with pauses for respiration. In barrel-chested breeds, such as the bulldog, sterna compressions may be more effective.

8. Drugs. There are multiple routes for drug administration when performing neonatal resuscitation. Intravenous (IV) is good choice if there is ready venous access. In neonates, IV injection presents a challenge and can best be achieved via the jugular or umbilical veins. If there is not venous access, drugs can be given topically or by IM injection sublingually. Absorption sublingually is rapid due to the preferential circulation to the brain and head. Consideration must be given to the potential for tissue irritation and injury when injecting at this site. If the neonate is intubated, intra- or endotracheal administration (IT, ET) may be used with lipid-soluble drugs (naloxone, lidocaine and epinephrine). Using the IT route, drug dosages often need to be doubled and then diluted to have adequate contact area and absortion. This method may be inappropriate in some neonates due to small tube diameter, delayed onset of action, poor absorption or potential for tissue irritation. Intraosseous (IO) administration of drugs is easy and results in similar blood concentrations as with IV administration. A spinal needle is placed through the trochanteric fossa into the medullary cavity at the proximal end of the femur. Intracardiac (IC) injections are not recommended because of the hazards involved: lung laceration, vessels laceration and refractory ventricular fibrillation. Subcutaneous (SQ) injections are not recommended due to poor absorption and circulation in compromised neonates.

8.1 Antibiotics. When antimicrobials are needed for the dam or for sick neonates, antibiotic choice requires consideration of its effect on colonization resistance. Antibiotic choice must often be made without benefit of culture and sensitivity results. Cephalosprins and clavamox are generally safe, while ampicillin, tetracyclines and sulfonamides should be avoided.

8.2 Atropine. Atropine crosses the placenta, but until puppies are 14 days old (11 days old in kittens), atropine has little effect on heart rate. Any effect it might have would only serve to increase oxygen demand on the myocardium, especially if the neonate is not well ventilated. Therefore, atropine is neither effective nor recommended in neonates.

8.3 Dextrose and Crystalloid Fluids. Care must be taken when giving neonates fluids. Neonates can neither concentrate nor dilute their urine, so fluid volume overloading can occur. Maintenance fluids rates for puppies range from 60-180 ml/kg/day. If needed, 10% dextrose can be given IV or IO (intraosseous) at a dosage of 2-4 ml/kg slowly.

8.4 Doxapram. The use of doxapram in neonatal resuscitation is controversial. Doxpram acts to selectively stimulate respiration and tidal volume by activating carotid receptors. The dogma is to administer 1-2 drops of doxapram, a respiratory stimulant, sublingually if the neonates are depressed. Current thinking is that if neonates are depressed and hypoxic, sublingual doxapram will not reach effective circulating blood levels. In fact, doxapram is not mentioned in most current guidelines for human infant resuscitation. If used, an IV route of administration is recommended.

8.5 Epinephrine. An endogenous catecholamine, epinephrine is an α and α adrenergic agonist used for cardiac resuscitation. Epinephrine administration should be considered only in cases where respiratory support and chest compression fail to elicit a heartbeat. The dose is 0.1-0.3 mg/kg IV or IO. Do not confuse the 1:1000 (1mg/ml) with the 1:10,000 (0.1mg/ml) formulations.

8.6 Naloxone. With Caesarian section delivery when the dam was medicated with opiods (eg. hydromorphone) , naloxone can be given, if needed, to the neonates after birth to reverse the opioid effects. The dose is 0.1 mg/kg IV or IO. Naloxone's duration of action is 45-90 minutes.

9. Don't give up too soon. Resuscitative efforts should be continued for at least 30 minutes.

References

Center SA, Randolph JF, ManWarren T, et al. Effect of colostrum ingestion of gamma-glutamylaminotransferase and alkaline phosphatase activity in neonatal pups. Am J Vet Res 1991; 52: 499 – 500.

Davidson AP. Neonatology. Clin Theriogen 1(1):127-141 2009.

Davidson AP. Topics in pediatrics. In: Proceedings Swedish Society for Small Animal Reproduction Annual Meeting. April 2005

Davidson AP. Nursing care of neonatal puppies and kittens. In: P Pratt (ed) Principles and Practice of Veterinary Technology. Mosby-Year Book, Inc., Santa Barbara, 1997.

Grundy SA. Clinically Relevant Physiology of the Neonate. VCNA 36(2): 443-460, Philadelphia: Elsevier Saunders, May 2006.

Johnston SD, Root Kustritz MV, Olson PNS. The neonate – from birth to weaning. In: Johnston SD, Root Kustritz MV, Olson PNS, eds. Canine and feline theriogenology, 1st edition. Philadelphia: WB Saunders; p.146 – 167, 2001.

Kelley RL. Canine reproduction: factors influencing litter size. Proc of the 2002 SFT Annual Conference, Colorado Springs, CO, Aug 2002.

Lavely JA. Pediatric Neurology of the Dog and Cat. VCNA 36(2); 475-503, Philadelphia: Elsevier Saunders, May 2006.

Lawler DF. Neonatal and pediatric care of the puppy and neonate. Theriogen 70;384-392, 2008.

Moon PF, Erb HN, Ludders JW, et al. Perioperative risk factors for puppies delivered by cesarean section in the United States and Canada. J Amer An Hosp Assoc 36:359-368, July 2000.

Traas AM. Resuscitation of canine and feline neonates. Theriogen 70;343-348, 2008.