GENERAL PRINCIPLES- Many of the patients are neonates, some pre-term and thus demand special consideration.
- In many cases the pathophysiology of the surgical disease dictates the optimal
anesthesia management. The anesthesiologist should understand the effects of the lesion on normal physiology.
- Surgery may be required immediately e.g. (congenital diaphragmatic hernia, tracheo-esophageal fistula) and there may not be time for optimal preparation of the patient. However, in most cases some time is available for preoperative resuscitation and the optimum
time for surgery must be decided by consultation between anesthesiologist, neonatologist and surgeon.
- For emergency abdominal surgery, the problem of full stomach must be considered (even if the patient has not eaten for some time, secretions accumulate in the stomach and emptying may be delayed by obstruction or ileus.
* Newborn and small infants aspirate stomach contents through a gastric tube, preoxygenate and perform awake intubation)
* Older children, aspirate stomach contents and perform a "crash" induction combined with cricoid pressure (Sellick's Maneuver).
* Remember: For crash induction in children (< 10yrs) succinylcholine does not increase intra-abdominal pressure at this age, and pretreatment with curare is not indicated.
- During thoracoabdominal surgery, blood loss may be considerable; be prepared to handle major blood transfusion.
- For major abdominal surgery, always place intravenous lines in the upper limbs. The I.V.C. may become occluded during the operation and thus transfusion via the lower limb veins would be useless.
- During limb surgery bronchial secretions (often serosanguinous) may accumulate and interfere with ventilation. Therefore all endotracheal intubation must have straight or plug and chain (Cobb) connectors to facilitate per operative tracheobronchial toilet; wherever this becomes necessary.
- During thoracotomy, V:Q ratios in the lungs are disturbed. Therefore increase the inspired oxygen concentration and check the arterial oxygen tension.
- In infants and small children, retraction of the lungs may obstruct major airways, impairing ventilation or it may compress the heart and great veins, leading to a precipitous fall in cardiac output and hence blood pressure. Constant breath- breath by monitoring via stethoscope is essential and a Doppler flow meter should be used to monitor pulse and blood pressure. In the event of bradycardia, hypotension or impaired ventilation:
* Ask the surgeons to remove all retractors immediately
* Venntilate the patient with 100% oxygen
- Patients requiring minor surgery ( e.g. herniotomy) may be preterm and/or have other condition that may complicate anesthesia and require special consideration.
Considerations for the newborn
Prophylaxis against hemorrhage: Ensure that Vitamin K is given, to prevent hemorrhage due to lack of Vit-K dependant factors.
Temperature: Avoid cold stress and decreases in body temperature.
- A heated transport incubator should be used to transfer the neonate to and from the operating room
- The operating room must be warmed to at least 24 degree C
- Leave the infant in the incubator till all the preparations are complete.
- Humidify anesthetic gases using the heated humidifier.
- Ensure that warm skin prep solutions (40 C) are used and that excess solutions are dried from the skin.
- Cover the head to prevent excessive heat loss from the scalp.
- It is preferable to intubate the neonate awake.
- Use a tube that passes the glottis easily and allows a slight leak during positive pressure ventilation.
- Use sterile ETT
- Position the tube carefully. Remember that in term newborn the trachea is only 4 cm long; therefore pass the tube 2cm below the vocal cords for optimal positioning.
- Check the air entry to all areas of the lung.
- The J.R. modification of the T- piece is mostly suitable for the newborn.
- Manual control of ventilation is preferable for thoraco-abdominal surgery, as subtle changes in compliance can be detected rapidly and adjustments can be made to maintain ventilation.
Preterm infantSize: Anesthetic management of the preterm infant is complicated by the very small size of the patient.
Apneic Spell: Common in the preterm infant. Post-operative apnea monitoring should be ordered for all infants less than 48 weeks PCA. The risk of apnea is increased during the first 24 hours.
Temperature control: The preterm infant is extremely vulnerable to heat loss. His surface area is even larger than the body mass and he has no insulating subcutaneous tissue.
Oxygenation: This must be very carefully controlled if hypoxia is to be avoided and risk of retrolental fibroplasia minimized. Inspired oxygen must be kept to the minimum that will allow safe conduct of anesthesia.
- Ascertain the FiO2 required preoperatively to-achieve satisfactory oxygenation. During non-thoracic surgery with controlled ventilation, continue with this FiO2 and check blood gas levels frequently.
- Whenever there is no contraindication use an air/ FiO2 mixture to achieve the desired FiO2.
- During intra-thoracic surgery it is essential to increase FiO2, check the blood gas levels frequently and limit the oxygen concentration as far as possible while avoiding the possibility of inducing hypoxia.
Hypoglycemia and Hyperglycemia: Preterm infants are prone to hypoglycemia. Blood glucose levels of <40 mg/dl should be corrected by infusions of glucose. Preterm infants are also prone to hyperglycemia, which leads to glycosuria, osmotic diuresis and dehydration and should be avoided by frequent blood sugar measurements.
Fluid administration: Avoid overload by careful control of I.V. Use tuberculin syringes to accurately measure small volumes of drugs. Syringe pumps and controlled lines are essential.
Coagulation: The preterm infant is subject to coagulopathy associated with shock and sepsis. Thrombocytopenia is common. Platelet concentrates, FFP or exchange transfusions may be required.
Down's syndrome (Trisomy 21) is common in 1.5/1000 births. Mental retardation is invariably present but varies in severity from patient to patient.
- Congenital heart disease (60%) with AV canal, VSD, PDA, TOF
- Respiratory infections are common, may be related to genetic anomaly, an immune deficiency and /or social and institutional implications.
- Atlanto-axial joint instability (12%) leads to cervical spinal cord injury.
- Duodenal atresia of the newborn is common
- Congenital subglottic stenosis is common
- Polycythemia is a frequent finding in the neonate and may require phlebotomy to relieve circulatory failure.
- Thyroid hypofunction is common as the child grows older
- Sleep apnea is common
- Airway: The large tongue and small nasopharynx predispose to respiratory obstruction, particularly during mask anesthesia and recovery stages. Congenital subglottic stenosis predisposes to post-operative stridor.
- Lungs: Is there any acute infection present, which requires therapy prior to surgery?
- Problem of associated cardiac disease
- Atlanto-axial joint instability may predispose to injury during intubation
- Retarded children are more difficult to manage during induction of anesthesia
Note: Children with Down's Syndrome are particularly sensitive to the effects of atropine.
Cystic fibrosisCystic fibrosis is an autosomal disorder. It affects many body systems including the lungs; respiratory failure develops by the 2nd /3rd decade of life.
Special anesthetic problems:
- Copious, extremely viscous secretions in the respiratory tract
- Because of the V/Q disturbances: Hypoxia may develop rapidly during anesthesia. Induction of anesthesia with inhalational agents is prolonged.
- Increased lung compliance. In the severe late cases, very high airway pressure may be required to provide adequate ventilation and prevent hypoxemia. Therefore use a cuffed ETT or bronchoscope, whenever possible.
- Many children having advanced cystic fibrosis become severely emotionally upset. All of them require especially careful and considerate handling and much reassurance.
Plastic SurgeryMany of these children have psychological upsets stemming from both the deformity and multiple surgical procedures. Thus a very careful considerate approach by the anesthesiologist is essential.
Smooth general anesthesia with quiet emergence lessens the risk of damage to the grafted areas and delicately sutured repairs.
Many patients requiring plastic surgery have potentially serious airway problems that require careful assessment and special management.
Congenital structural anomalies commonly affect more than one body system. If congenital heart disease is present, ensure that the child is given prophylactic antibiotic therapy pre-operatively.
Cleft lip and Palate Cleft lip and palate are present in various combinations in as many as 1/1000 live born infants. Infants with these lesions may be both anemic and malnourished because of feeding difficulties and may have had repeated respiratory infections.
- Congenital Heart Disease
- Pierre Robin Syndrome
- Treacher Collins syndrome
- Subglottic stenosis
- Cleft lip repair: performed at 10-12 weeks of age
- Cleft palate repair: Nowadays from 9 months onwards
- Palatoplasty and pharyngoplasty: Palatoplasty performed from 9 months onwards Pharyngoplasty is performed from 5 to 6 year onwards.
Special anesthetic problems:
- Airway problems, including difficulty in intubation
- Blood loss
- Problems related with associated conditions
- Pharyngoplasty is performed to decrease the velopharyngeal incompetence and improve speech. This procedure increases resistance to ventilation.
- Post-operative airway obstruction may occur in the PICU.
- Chronic airway obstruction may persist after the operation and lead to pulmonary hypertension and/ or obstructive sleep apnea.
Cystic HygromaCystic hygroma is in fact a cystic lymphangioma which usually occurs in the neck and less commonly in the axilla. Intraoral extension of this benign tumor may cause airway obstruction. 3% of cervical tumors extend in to the mediastinum.
Special anesthetic problems:
- Existing airway obstruction
- Difficulty with intubation due to distortion of the airway
- Complete removal of the tumor may involve extensive dissection and be accompanied by major blood loss.
BurnsAfter the acute phase of their injury, children who have extensive burns require repeated anesthesia for plastic and reconstructive surgery.
- Contractures resulting from burns of the face and neck may make intubation and maintenance of the airway during anesthesia very difficult.
- Succinylcholine is contraindicated for 2-3 months after severe burns (It may cause cardiac arrest secondary to hyperkalemia.
- Blood loss may be large during grafting of extensive burns.
- Temperature homeostasis is impaired and special measures must be taken to avoid excessive heat loss.
- Infection of burns is a serious hazard at this stage. Observe great care in handling the patient in order to prevent cross infections; use reverse isolation techniques in the operating room and post-operatively.
- Hepatic dysfunction may follow burns recovery and takes several weeks.
- Emergence from anesthesia should be quiet in order to avoid damage to recently grafted areas.
- Peri-operative management must be planned to minimize the possibility of increasing the intra-cranial pressure.
- Light GA is adequate for neurosurgery procedure. All anesthetic drugs used should be short acting, capable of being rapidly eliminated, or completely reversible. This ensures that the patient speedily emerges from anesthesia and that accurate continuous neuro-surgical assessment is possible.
- Post-operative pain is not severe following intracranial surgery. Potent analgesics are unnecessary and may cause ventilatory depression, they therefore should not be used.
Hydrocephalus: Hydrocephalus may be due to a congenital defect ( e.g. Arnold Chiari malformation, aqueduct stenosis) or acquired disease ( e.g. tumor). In the newborn, hydrocephalus is most commonly secondary to Arnold Chiari malformations.
- Exercise special care if the ICP is increased. The patient should be watched carefully until surgery can be arranged as his condition may deteriorate suddenly, necessitating immediate ventricular tap or lumbar puncture.
- If the patient becomes apneic; intubate, ventilate and arrange for an immediate ventricular tap.
- Pre-medication: only atropine; preferably intravenous at induction.
- Do not give opioid analgesics.
Myelomeningocele and Encephalocele: It may result from failure of the neural tube to fuse in the fetus. The incidence of myelomeningocele is approximately 1- 4/1000 live births; with a large geographic locations. Encephalocele is much less common.
Associated conditions: Hydrocephalus, in many cases with aqueductal stenosis occurs in 80% of infants with myelomeningocele or encephalocele.
- Potential difficulty in positioning the patient for intubation.
- Blood losses are difficult to measure and may be considerable.
- Difficulty in controlling heat loss during surgery
- Children cannot usually be expected to co-operate during eye surgery. Therefore, general anesthesia is required.
- Intraocular surgery and surgery of nasolacrimal duct and eyelids require a bloodless field. Smooth general anesthesia with optimal airway, good positioning of the patient and quiet emergence with out coughing or straining is important
- The oculocardiac reflex is powerful in children but can be readily blocked I children by giving atropine intravenous in usual dosage (0.02mg/kg) at the time of induction. Monitor the heart rate.
- Some children may be under treatment with long acting plasma cholinesterases inhibitors (e.g. phospholine iodide). Significant systemic absorption occurs and may result in toxic symptoms (nausea, vomiting and abdominal pain) and prolonged apnea following succinylcholine. Timolol maleate topical (a ß blocking agent) is used as an anti glaucoma agent in children. It is absorbed from the conjunctiva and may cause bradycardia refractory to atropine and bronchospasm.
- Drugs applied to the conjunctivae during surgery may cause systemic effects. Epinephrine and phenylephrine may cause hypertension and arrhythmias, effects which are potentially dangerous especially during halothane anesthesia. Monitor the heart rate and blood pressure carefully with drug instillation and be prepared to discontinue the halothane.
- Anesthesia for ophthalmology must be deep enough to ensure that eyes are immobile and fixed centrally. Smooth extubation with out coughing can be affected by administration of lidocaine 1-2mg intravenously immediately before removing the tube.
- Post-operative pain may be troublesome after eye operations requiring full doses of analgesics.
Strabismus: Commonest eye operation in children
- Oculocardiac reflex: Severe bradycardia and even cardiac arrest can occur as a result of traction on the extraocular muscle.
- Oculo-gastric reflex: Vomiting after eye muscle surgery is very common.
- Post-operative pain may be considerable.
Dental surgery General Principles:
- Children may require GA more frequently than adults for dental procedures.
- Many children who present for GA have previous failed attempts at surgery under LA and are very apprehensive.
- Some children have behavioral disorders or retardation syndrome and require special consideration.
- Some children have other medical conditions which require special considerations.
- Endotracheal intubations should be performed for all children. Nasal intubation per se causes bacteremia and is an indication for prophylactic antibiotics, if heart disease is present.
- Special care must be taken to ensure that no foreign body should remain in the airway at the end of the procedure.
ENT casesGeneral principles:
As many of these operations involve the airway, the anesthesiologist must be prepared to provide good surgical access to that area while maintaining a safe ventilatory pathway for the patient. The use of laser to treat lesions of the larynx, has added some additional potential problems of anesthesia management.
- Sharing the airway with the surgeon.
- When acute infection or extreme lymphoid hypertrophy is present, intubation may be difficult.
- Danger of bleeding post-operatively.
- History of bleeding or recent salicylate therapy.
- History suggestive of sleep apnea or OSA.
- Difficulty maintaining adequate ventilation during the procedure, when the airway must be shared with the endoscopist.
- Existing impairment of ventilation in some cases.
- The child may have undergone esophagoscopy repeatedly and thus be very apprehensive.
- In small infants, passage of an esophagoscope may compress the trachea and obstruct ventilation, even when ETT is in place.
- Coughing or other movements can result in esophageal perforations during the procedure. Patients must be anaesthetized adequately to maintain complete immobility.
- Lower esophageal stricture or achalasia may have resulted in esophageal dilatation higher up. Food and secretions accumulated in the dilated segment may be aspirated during anesthesia.
Hematological disordersAnemia: Children requiring surgery may be anemic. Remember that Hb level, normally 18-20g/dl at birth falls to 10-11g/dl by 3 months and thereafter climbs gradually to 14-16g/dl at 6 years of age.In patients with anemia:
- O2 transport to the issues can be maintained by increased cardiac output or increased O2 extraction from blood.
- Coronary sinus blood is normally desaturated, therefore O2 transport to the heart muscle can be maintained only by increased coronary blood flow.
- Increased risk of cardiac arrest during anesthesia.
- Patients with cardiac or serious respiratory disease require a higher Hb level than normal children.
If surgery cannot be delayed: Transfuse the patient. If blood transfusion cannot be done, avoid excessive sedation. Oxygenate well. High O2 concentration. Use ETT. Use controlled ventilation. Do not give CVS depressant drugs. Extubate awake, Give O2 during transport
Sickle cell disease: Presence of abnormal HbS. HbS forms a gel when deoxygenated, distorting the erythrocytes; these then occlude vessels, causing infarction. The disease is almost entirely confined to the black races and may become evident during infancy when HbS replaces fetal Hb.
- Sickle cell trait (Mild): when HbS < 50%
- Sickle cell disease (Severe form): When HbS > 75%
- A sickling crises may be precipitated by general or local hypoxemia.
- Sickling is more likely if patient is anemic, acidotic, hypotensive, dehydrated, or hypothermic.
- If patient has sickle cell disease, previous vascular occlusive crises may have permanently impaired cardiac, hepatic or renal function.
- Serum cholinesterase activity may be low.
Thalassemia: It occurs in two forms. The primary defect is a slow rate of Hb synthesis.
- Thalassemia minor: Hb level is usually 9-12 g/dl. No special treatment required and no anesthesia problems.
- Thalassemia Major: Also called Cooley's anemia: Low Hb levels may necessitate repeated transfusions, which may result in hemosiderosis.
Special anesthesia problems:
- Anemia may be severe (5-7g /dl).
- Hemosiderosis may have developed and may impair myocardial and hepatic function.
- Facial deformity (overgrowth of the maxillary region) may make intubation difficult.
Idiopathic Thrombocytopenic Purpura:
In ITP, an antiplatelet factor is present which results in the excessive destruction of platelets by the spleen, with consequent thrombocytopenia and bleeding. The disease may be acute or chronic; the highest incidence is 7 years of age. The acute form, lasts for 1 month before spontaneous remission, may be complicated by severe intracranial bleeding or exsanguinating GI hemorrhage, but the overall death rate is less than 2%.
Surgical therapy: Splenectomy results in improvement in almost all the patients with acute ITP and many of those with the chronic condition.
- Platelet counts may be very low and cannot be improved by infusions until the spleen is removed. Therefore infusing platelets pre-operatively is useless.
- Many patients will have been treated with steroid hormones.
Factor VIII Deficiency (Classic Hemophilia Type A): Classic hemophilia is characterized by episodes of bleeding, either spontaneously or after minimal injury. Hemophilic children require special care during surgery.
Pre-operative measures: One hour before surgery, an infusion of cryoprecipitate (3mg/kg) should be given followed by an assay for plasma factor VIII activity. Surgery can proceed if factor VIII activity is over 30%.
- Depending on the nature of surgery, the factor VIII levels in the blood should be maintained at 30-50% for several days. This is achieved by giving infusions of cryoprecipitate, as dictated by repeated assays for factor VIII.
- After dental extraction, epsilon-aminocaproic acid (Amicar) may help to inhibit fibrinolysis of formed blood clot.
- When factor VIII inhibitors are present, cryoprecipitate cannot be used and treatment presents a grave problem. At present, factor IX infusions are given.
Factor IX Deficiency (Christmas Disease, Hemophilia Type B):
- Factor IX levels are assayed and factor IX infusions are given.