Pediatric equipment By Dr. Amr Maher Darwish Lecturer Of Anethesia In Ø this lecture we are going to discuss the kind of equipment we- anesthesiologists- need to safely anesthetize a pediatric patient. ØThese equipments are basically the same as the equipment required for the adults; but pediatric patient would require more attention for fine tuning and better outcome. Warming devices ØTemperature regulation is a greater problem in a child than an adult because of the higher ratio of body surface area to body mass. ØHypothermia may cause an infant to become acidotic and apneic, and may alter the kinetics of medications.(1) ØWrapping • It can reduce the radiant and convective heat losses.(1) • Wrapping can be done by simple materials as the plastic wrap used for food or by a sophisticated material as the space blankets with reflective aluminized layers. • Wrapping has the hazard of eliminating sweating as a regulatory thermal mechanism, so hyperthermia may develop. ØRadiant warmers • Overhead radiant heating units are useful; but it always carries the risk of skin burn. (1) ØWarming water blankets • Circulating water mattresses are useful in maintain normothrmia in patients with body surface of 0.5 m2 which means 10 kg of body weight or less, which makes it perfect for a pediatric patient. (1) • precautions to prevent possible surface burns: ü fluid temperature should never exceed 39⁰C. ü Avoid direct contact of the patient’s with the warming blanket. ØWarm air mattress • The most useful devices for keeping pediatric patient warm, because they can be wrapped around any part of the body. • They keep body temperature by a combination of convection with warm air and also the plastic wrapping which serves to reduce the evaporative heat losses. (1) ØHeat and moisture exchangers (HME) (1) • They preserve body heat, but they : ü Increase the resistance to breathing. So, there are small sized HME Fit for pediatric, and they are not suitable for spontaneously breathing patient. ü May clog with humidity over time. ØFluid warmers • As a rule, We have to give the patient his requirement of fluids warmed at least to body temperature. • The effectiveness of fluid warmers in warming intravenous fluids (or blood products) depends on the time that these fluids are in contact with the warmer. • limitations to use: ü It is not effective in reversing hypothermia in pediatric patient, as with slow intravenous fluid therapy-which is seen in the maintenance phase- the heat is lost along the length of the intravenous tubing between the warmer and the patient.(1) ü over heating the fluids, would lead to possibility of RBC’s hemolysis. Intravenous Therapy ØRules for intravenous therapy • An intravenous access should be established in all anesthetized patients.(1) • The infusion fluid container should not exceed the estimated fluid deficit for a certain patient; unless a volume limiting device is used.(2) • All the lines should be purged, and preferably intravenous air traps should be used, especially, in neonates and children with known intracardiac defects.(3) ØWhen precise amounts of fluids need to be transfused, electronic pumps and intravenous rate controllers are used. ØThese devices should have precise volume limits, air bubble alarm and pressure alarm. ØAnother cheaper method for metered transfusion is the use of a multiple stopcocks, with a syringe attached to one of the stopcocks for a precise volume calculation. ØIn emergencies, high flow rates through an intravenous line are needed. A rapid transfusion devices that have rapid warming and rapid administration features are the best solution. A Ø cheaper solution, but less effective, is the pressure infusion cuff that wraps around the solution. Airway devices ØMasks • A face mask that is suitable for pediatric use would be: üSmall dead space, like Rendell-Baker/Soucek masks. ü Transparent masks help in observing the patient’s color and shows condensation from exhaled water vapor. ØAirways • Oral airways üIt is a must in pediatrics as infants have large tongue. üInfants from 1-2 years would require 7 cm airway, 2-8 years an 8 cm airway, and over 8 years 9 cm. (1) üIf the airway is too large, it may result in uvular swelling or epiglottitis and postoperative airway obstruction. (2) • Nasopharyngeal airways ü These are not usually used in pediatrics as the internal diameter of such airways are usually small, increasing the work of breathing. Also, there is an increased risk of bleeding d.t. adenoid hypertrophy. ü It can be replaced by an endotracheal tube cut to appropriate length. • Laryngeal mask airway (LMA) ü As in adults, LMA is a valuable airway device, it is used to maintain airway in spontaneous breathing setting. (1) üIt becomes most valuable in the difficult to intubate, difficult to ventilate scenarios. Size 1 1 1/2 2 2 1/2 3 4 5 6 Adult Pt. Neonate Infant Child Child Child Adult Adult 70- selection <5kg 5-10kg 10-20kg 20-30kg 30-50kg 50-70kg >100kg 100kg Inflation 4ml 7ml 10ml 14ml 20ml 30ml 40ml 50ml Volume ØEndotracheal tubes (ETT) • In pediatric O.R.; ETT with sizes ranging from 2 to 6 mm internal diameter (ID) must be available, along with the appropriate size stylets. • The estimated size for a child older than 2 years is the patient’s age divided by 4 plus 4.5 mm ID. A full term neonate would accept a 3 mm ID, a normal 1 year old would accept 3.5-4 mm ID, and a 2 year old 4.5 to 5 mm ID. (1) • usually uncuffed tubes are used for elective surgeries, but when a patient has a full stomach, hiatus hernia or non compliant lungs a cuffed tube is used, and these are available as small as 3 mm ID. (1) • For head and neck surgeries, preformed tubes are used putting the anesthesia circuit away from the surgical field. Also, armored tubes are available whenever tube kink is a possibility, but, the wire reinforcement adds to the external diameter. ØIntubation equipment • For pediatric patient, laryngoscopes are available with small lightweight handle and a full range of blades. Generally, a straight blade design is often used in small children, infants and neonates in sizes 2, 1, and 0 respectively. (1) • Flexible and rigid fiberoptic laryngoscopes and bronchoscopes are available for pediatric and used for patients with difficult airway. Anesthesia machine and appendages ØAnesthesia machine • Most of the modern standard adult machines can be adjusted for pediatric setting, it is not economic or necessary to have anesthesia machine customized for pediatric use only. • The machine should have air flow meter for cases where nitrous oxide or high inspired oxygen is contraindicated for example in patients with intestinal obstruction and in premature infants. ØCircuits and ventilators • Infants and neonates less than 10 kg were anesthetized with non rebreathing systems as the Mapleson D systems; which have no valves or CO2 absorber which would greatly reduce the resistance to breathing. one famous modification to it the Jackson-Rees modification of Ayre’s T-piece. • The main disadvantage of such system is the need for relatively high fresh gas flow which leads to waste of anesthetic agents and excessive pollution to the O.R. • Nowadays, controlled ventilation is recommended, as it allows the use of circle system even in neonates with the advantage of lower fresh gas flow and therefore cost savings and less pollution. • Ventilators used in pediatric should be able to deliver small tidal volumes, rapid rates in high accuracy, and should have pressure limitation device. • In children less than 10 kg, pressure controlled ventilation may be preferred with peak inspiratory pressure of 15-18 cm H2O (1). In older children, volume controlled ventilation can be used, with tidal volume set at 8-10 ml/kg. in both conditions, the adequacy of ventilation should be monitored . • The tidal volume shouldn’t be only based on the weight, but also on: üchest wall expansion. übreath sound auscultation. üobserving the peak inflation pressure. Equipment cart and defibrillators • The usage of mobile multi-drawer carts is very valuable in the care of pediatric patients; especially that pediatric anesthesia is often administrated outside the O.R. • These carts are used to stock all the pediatric equipment and supplies necessary to make the anesthetic practice safe. • Defibrillators to be suitable for pediatric use should have energy range that can be adjusted to the appropriate levels (1-2 jouls/kg), and a pediatric sized paddles. Monitoring equipment ØAnesthesia record • The anesthesia record is important both in the medicolegal aspects and as a monitor tool; documenting the patient’s status on arrival, and evaluating every aspect of the patient. • Many changes that are too subtle to interpret on moment to moment basis, become obvious when plotted in the record over time. (1) ØPrecordial/esophageal stethoscope • it is a very valuable monitor. In infants, neonates and small children, an experienced ear can easily diagnose arrhythmias, assess cardiac output and adequacy of blood pressure. • The optimal site where both heart and breath sounds can be auscultated is the apex of the heart, sometimes the suprasternal notch is used. • After intubation, the precordial stethoscope can be changed with an esophageal stethoscope, which is usually not traumatic even in newborns. (1) ØBlood pressure measuring devices •Non invasive blood pressure measuring devices ü Blood pressure cuff should cover approximately two thirds of the length of the upper arm and its bladder should be placed on the artery. If the length and the size are wrong, fallacies would occur. ü Blood pressure measure from the cuff wrapped around the infant’s calf muscle poorly correlates with the arm blood pressure. ü We should avoid prolonged inflation time, as this may lead to venous stasis, petechiae, and possibly nerve compression damage. • Invasive blood pressure, central venous pressure, pulmonary Artery pressure monitoring ü In infants and neonates, percutaneous arterial cannulation is performed with a 22- to 24- gauge catheter-over-needle device, with a 20- gauge device in older patients. (1) For central venous and pulmonary artery cannulation, seldinger technique is used. ü The reference location for all pressures is the level of the patient’s right atrium. (2) ü values of central venous catheter and pulmonary artery catheter: helping in the management of air embolism in operations in the sitting position, mixed venous sampling from the pulmonary artery catheter to measure oxygen extraction, and calculation of COP. Balloon Inflation valve ØElectrocardiogram (ECG) • ECG is a mandatory monitor. The lead placement may differ in pediatric patient than in adult patient, as the primary need for ECG in pediatrics is the diagnosis of arrhythmias rather than the detection of ischemia. • The lead should not become wet with preparation solutions and should be isolated from the electrocautery dispersive electrode to avoid electrical burn. ØOxygen monitor • In neonates, especially premature, it is important to monitor inspired oxygen concentration, so as to be able to blend air with oxygen and prevent the possible ocular toxicity resulting from high inspired oxygen concentration. ØTemperature monitors • Temperature monitoring is important to detect temperature fluctuations, which is mostly hypothermia. (1) • Monitoring site could be : üEsophageal & nasopharyngeal probes: but when the patient is intubated the esophageal probe may show lower value (2). ü Rectal probe: but it is subject to cooling during major abdominal procedures. ü Axillary probe: placed high in the axilla and no IV fluids should be given in that arm. (1) üTympanic membrane probe: but improperly placed probe may injure the tympanic membrane. ØPulse oximetry • Pulse oximetry is by far the most important monitor in anesthetic practice, its value:- ü Measuring oxygen saturation value. ü Provides an early warning of developing desaturation well before a clinician is able to detect it clinically. (1) ü Detecting arrhythmias and peripheral perfusion inadequacy caused either by hypovolemia or hypothermia by the waveform. • Its accuracy is affected by: ü Intravenous dyes and nail polish. ü Dyshemoglobinopathies. ü When O2 saturation becomes less than 70%. ü Electrocautery, flickering or bright O.R. lights. ü Movement of the patient. ØCarbon dioxide analyzers • Monitors that measure the end tidal CO2 work by 2 methods; either suctioning the expired gas from the anesthesia circuit (side-stream sampler), or acting as a main stream optical sensor. • The side stream samplers may become obstructed with water or secretions; while the main stream is heavy and bulky leading to the possibility of endotracheal tube kinking especially in smaller pediatric sized tubes. • Values of measurement of end tidal CO2 : üConfirm endotracheal intubation. üAdjust ventilatory setting, and confirm its adequacy. üDetect complications like disconnections, ETT kinking, accidental extubation, air embolism and malignant hyperthermia. ØNeuromuscular monitoring • Whenever a muscle relaxant is used, neuromuscular transmission should be monitored; best by assessing the train of four. • The infant sized ECG electrodes are the best electrodes used to deliver the impulses, and the best location for these electrodes is over the ulnar nerve with observation of the thumb. (1) ØDisconnection/apnea alarms • Whenever a ventilator is used, a disconnection alarm should be used especially in the absence of capnography. These alarms sense time cycling of pressure events • They may not be sensitive enough to detect extubations with small endotracheal tubes or partial circuit disconnections because of the continued presence of flow resistance ØApnea monitors • These are very helpful in the perioperative, and recovery room period; especially in premature infants with less than 60 weeks postconceptual age, infants with history of apnea spells • These monitors depend on transthoracic impedance or respiratory motion. ØInspiratory pressure gauge • In patients requiring mechanical ventilation, especially the pediatric age group, a pressure gauge applied at the airway allows delivery of precise pressures and help to prevent barotrauma. (1) • The closer the measurement site to the airway, the more accurate the pressure measured ØBlood loss monitoring • Blood loss estimation is best done by: üClose observation of the surgical field and the patient’s physiologic status. üThe use of a small volume tarp on the suction line before the main evacuation trap is arranged. (1) üWeighing surgical sponges making the approximation of 1 gm of weight equivalent to 1 ml of blood. Urine volume monitoring • U.O.P. is valuable for: ü Indicator of volume and perfusion status. ü If hematuria develops, it would indicate surgical trauma to the urinary system, or transfusion reaction. • The indications for urinary catheter insertion: ü Procedures with massive fluid shifts. ü Prolonged radiologic procedures with large doses of contrast material. üDiuretic therapy, and urinary reconstructive procedures. Purchasing Anesthesia Equipment ØUseful principals for any equipment purchase:- ü New equipment should be compatible and interface with the equipment that is already present. ü The new equipment should be usable in different locations (e.g. O.R. and ICU). üSales persons are biased, the reviews and info about a certain device or brand name should be obtained from unbiased sources, as research institute and boards. ü The proposed equipment should be tested in the same working environment and by the same personnel who will be using it. ü The hospital safety office should check for all the safety issues regarding the use of this equipment. ü Spend as much on the maintenance as on the product. Consider a maintenance contract. ü If two products are comparable, choose the one with local service facilities. ü Consider the specific needs, for example if the monitor is to be used for transport or outside the O.R. it must have internal battery backup. ü Though economically difficult, additional spare units of the same equipment should be available, as any given piece of equipment will occasionally be out of service. Questions Ø To warm a 12 years old hypothermic child the best would be: A) Water mattress. B) Warm fluids. C) Warm air blanket. D) Over head warmer. ØConcerning pediatric airway, the following is true: A) Nasal airway is better than oral airway. B) Laryngeal airway has no role. C) Curved and straight laryngoscope blades can be used. D) Reinforced endotracheal tubes is a must. ØConcerning mechanical ventilation in pediatrics, the following is true: A) It is contraindicated in pediatrics. B) The tubing has to be wide to decrease resistance. C) It is more economic. D) No role for volume controlled mechanical ventilation Ø the value obtained from a pulse oximeter is not affected by: A) Desaturation, less than 70% B) Nail polish. C) anemia. D) Bright O.R. light and patient movement.
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