Pediatric Anatomical and Physiological Differences 2024-2025 PDF

Pediatric anatomical and physiological differences Dr.Ghassan AL-jumaily 2024-2025 Several anatomical and physiological differences impact the effects and techniques of anesthesia administration. Pediatric patients can be divided into four groups based on age....

Pediatric anatomical and physiological differences Dr.Ghassan AL-jumaily 2024-2025 Several anatomical and physiological differences impact the effects and techniques of anesthesia administration. Pediatric patients can be divided into four groups based on age. I. Newborn: from birth to the first 24 hours. =°=⑦> > > II. Neonate: from 1 to 30 days of life. -> > III. Infant: from 1 month to 12 months of age. - - IV. Child: from 1 year to the onset of puberty. -> - >  Cardiovascular Physiology Cardiac output for a * neonate is 30-60% greater than an adult. This helps meet the increased oxygen consumption requirements. > Cardiac output in the- pediatric patient is dependent on heart rate. - Monitoring of the pediatric patient’s heart rate can be accomplished with a precordial stethoscope, ECG, and pulse oximetry. - - -- - Prompt recognition and treatment of bradycardia are critical. Bradycardia is : 1. less than 80 in children 1-8 years. - - - 2. less than 100 beats per minute in infants aged 1-12 months. - => -- ⑳ 3. less than 120 beats per minute in neonates. ❑ It is the most common rhythm before cardiac arrest in the pediatric patient. 1. Hypoxia. And then: & The most common cause of bradycardia in pediatrics is: > -> 2. Vagal stimulation (suctioning, surgical traction, etc.). 3. An overdose of anesthetic medications. - 4. Hypothermia. - 5. Increased intracranial pressure. - The blood volume of the pediatric patient is highest as a neonate - - - >>>> > and declines with age. Knowledge of the approximate blood volume is important when calculating total blood volume and estimated blood loss. e.g., a 4 kg neonate’s total blood volume would be calculated as follows: ❖ 4(kg) X 85 (ml/kg) = 340 ml total blood volume. S  Pulmonary Physiology and Airway Anatomy The functional reserve capacity(FRC) is=> &during anesthesia, airway much smaller in infants and neonates obstruction can result in hypoxia very quickly. => For this reason, pulse oximetry is essential. - Induction and emergence are especially critical periods to monitor for these complications. Oxygen consumption for a neonate is two times greater than that of an adult. The anatomy of the pediatric airway is different compared to an adult: The pediatric patient is prone to -> --- airway obstruction related to a proportionally larger head, short neck, and large tongue. => > - -> Positioning of the patient's airway is an important consideration. Overextension can result in airway obstruction in the neonate. Infants and neonates exchange air primarily through their nasal airways. The larynx is higher in the infant and child (cervical vertebrae 3-4) than in the adult (cervical vertebrae 5- = 6). -> - - The epiglottis is large, stiff, and U-shaped. The trachea is short, and the right main bronchus is less angled, this increases the risk of a right mainstem intubation.  Choosing the correct-size endotracheal tube and approximate length of insertion is important. This can also be accomplished by a simple calculation. The equation that can be used (age/4+ 4) will approximate the correct size of the endotracheal tube. Regardless of the calculations, an endotracheal tube should slide easily into the trachea, and never be pushed or forced. The calculation for the correct endotracheal tube depth insertion is to multiply the diameter of the endotracheal tube by 3. For example, an endotracheal tube that is a size of 3.0 would be multiplied by 3 to equal a depth insertion of 9 cm. Auscultation of equal, bilateral lung sounds (including the axilla) after endotracheal tube placement should always be performed.  Renal System and Extracellular Fluid Volume At birth, the kidneys have a decreased glomerular filtration rate, decreased sodium excretion, and decreased concentrating ability. # The glomerular filtration rate will increase and reach adult levels by 12-24 months of age. Neonates and infants up to ⑧ 24 months are not able to compensate for alterations in fluid balance as well as adults. This makes fluid replacement very important. # The extracellular fluid volume in an infant is twice that of an adult. Approximately 40% of the body weight in -& -> infants is extracellular fluid compared to 20% of adults’ body weight. - - Neonates, infants, and children fasting for anesthesia can become dehydrated more quickly than an adult. Careful fluid calculation includes NPO deficit, maintenance fluids, 3rd space fluid loss, and estimated blood loss replacement. For a pediatric patient that is dehydrated, it is important to correct pre-existing deficits before anesthesia - to avoid hypotension. -  Temperature Regulation Neonates and infants can rapidly lose heat, even in warm environments. > => They are at greater risk for hypothermia than adults due to: - - A. Relatively high surface-to-volume ratio. B. High metabolic rate. C. Insufficient body fat for insulation. - Infants less than 3 months do not shiver to generate heat. - & ② It is important to take steps to minimize heat loss including a warm operating room, warm blankets, or a heating blanket. ⑤ Monitoring the patients’ temperature before, during, and after the anesthesia is important to detect abnormal drops or increases in temperature. - - -  Pharmacology in Pediatrics Pediatric patients respond differently to anesthetic medications when compared to adults. This is due to physiological differences that include: a. Increase extracellular fluid. b. Decrease skeletal mass. c. Increase metabolic rate. d. Decrease renal function. e. Receptor maturity. ❖ Inhaled Anesthetics Uptake, distribution, and potency of volatile anesthetics are different in neonates and infants than in adults. - - Induction of general anesthesia occurs faster in neonates and infants. Emergence also occurs faster. The differences between adult and pediatric patients during induction and emergence are: 1. Smaller functional residual capacity (smaller lung volume). && & 2. Greater blood flow to the vessel-rich tissues such as the brain, heart, liver, and kidneys. - - In infants and neonates, the vessel-rich tissues comprise about 22% of total body weight. - > => In adults, the vessel-rich tissues compose about 10% of the total body weight. - MAC varies according to the age of the patient. In general, MAC is lower in neonates than in infants. MAC increases until about 2-3 months of age, peaks during infancy, and then steadily declines. During puberty, there is a brief increase in MAC. After puberty, MAC will continue to decline. Lower MAC requirements for volatile anesthetics in neonates are due to an immature central nervous system. ❖ Intravenous Anesthetic Agents - Neonates are sensitive to intravenous anesthetic agents. 1. They have an immature blood-brain barrier. 2. decreased ability to metabolize medications such as opioids and barbiturates. - - - 3. lower doses of intravenous anesthetic medications are required to produce the desired effects. 4. There are some generalized exceptions. For example, to induce general anesthesia higher doses of Propofol (on an mg/kg basis) are required when compared to an adult. ⑭ Pediatric patients less than 6 months old may be& administration. > - ⑧ more sensitive to respiratory depression resulting from opioid Caution should be used when administering opioids to this age group. The pediatric patient should be carefully monitored during the postoperative period. ❖ Non-depolarizing Muscle Relaxants & Neonates and infants may be more sensitive to the effects of non-depolarizing muscle relaxants. The neuromuscular junction of the infant is- - immature. hepatic systems. - & The duration of action of non-depolarizing muscle relaxants may be prolonged due to immature renal and  Depolarizing Muscle Relaxants - Neonates and infants require higher doses, on an mg/kg basis, of succinylcholine than the adult patient. #This is due to an increased extracellular volume and volume of distribution. - The dose of succinylcholine in pediatrics is 1.5-2 mg/kg IV compared to 1 mg/kg IV in adults. Routine use of succinylcholine in pediatric anesthesia is not recommended. = AThe use of succinylcholine in pediatrics should be reserved for emergency intubation, rapid sequence - induction, and laryngospasm. - - Thank you for listening Your questions are welcomed