What is the possible significance of a heart murmur? How should it be evaluated?

Are any lab tests helpful? Which ones? Should this patient have a preoperative echocardiogram? Why? Should a cardiology consult be obtained? Why? A small atrial septal defect is diagnosed. Is this of any significance?

What are the perioperative implications of this tumor? What is diabetes insipidus?

How can diabetes insipidus be diagnosed preoperatively? If diabetes insipidus is present preoperatively, will this affect your preoperative fluid management? How do you assess the need for perioperative steroids? What are the possible implications of inadequate steroid replacement? What other hormones can be affected? What lab work would you require preoperatively? Explain.

During routine random examinations, up to 30 % of children will demonstrate an innocent murmur. There are several innocent murmurs of childhood, not associated with any cardiac pathology, with which a pediatric anesthesiologist should be familiar. The innocent murmur (Still’s murmur) is characterized by a high pitched, vibratory, short systolic murmur heard along the left midsternal border without radiation in children 2–7 years of age. An innocent venous hum resulting from turbulent flow in the jugular system may also be detected in the neck or upper chest. The hum can be changed or eliminated by position changes or light compression of the jugular veins in the neck. In some cases of increased cardiac output such as during febrile illnesses, murmurs of flow across normal semilunar valves are heard. The murmur of an ASD is similar to that appreciated in pulmonic stenosis. There is no murmur caused by the low velocity left to right flow across the ASD itself. Because of the increased flow across the pulmonic valve in children with right to left flow through an ASD, a murmur can be heard. The murmur is characterized as a soft ejection-type (crescendo-decrescendo) murmur of relative pulmonic stenosis which is heard at the upper left sternal border. This murmur results from the excessive flow across a normal pulmonary valve. The second heart sound is louder and also widely and persistently split as a result of this excessive flow. The most common type of ASD is the secundum type with the abnormal connection between the atria, a result of incomplete formation of the second atrial septum. PVR remains normal throughout childhood and CHF is quite infrequent. Adults with uncorrected ASDs do develop CHF and/or atrial flutter or pulmonary hypertension, so correction of the ASD is generally undertaken in early childhood. The significance of an ASD is that of the possibility of a paradoxical embolus in which air or clots in the venous system cross the ASD and lead to complications in the systemic arterial circulation.

Craniopharyngioma, a tumor of Rathke’s pouch, may descend into the sella turcica and destroy part or all of hypothalamic and pituitary tissues as it enlarges, leading to hypopituitarism [1]. Preoperatively, the child should be evaluated for adrenal or thyroid dysfunction [2]. If ACTH secretion is impaired by the tumor, the production of glucocorticoids and androgens by the adrenal cortex will be below normal. If not evaluated preoperatively, adrenal insufficiency should be assumed and the patient treated accordingly. Diabetes insipidus is unlikely to be seen preoperatively but certainly may occur during or after the procedure. It is diagnosed by the presence of a large volume of dilute urine (Osm <300 mOsm/mL) in the face of increasing serum osmolarity and increasing serum sodium. If replacement of urinary losses with dilute IV fluid such as D2.5W or D5 0.2NS is insufficient, an infusion of aqueous vasopressin should be started. The preoperative lab tests ordered depend upon the clinical presentation but may include electrolytes, fasting glucose, thyroid function tests, and a CBC. Of course, imaging studies ordered by the neurosurgeon should be reviewed as well.

Would you administer a premedication on this child? Why? Would you require an intravenous catheter before starting the induction? Why? If not, or if the initial attempts are unsuccessful, what’s next? A colleague suggests intramuscular ketamine. Agree? Why? Is an inhalation induction appropriate? Explain.

Would you insert an arterial catheter? Why? Is a central venous catheter needed? Why? If yes, where? Potential problems? Where do you want the tip to be? How do you confirm its position? What if multiple attempts are unsuccessful? Is a urinary catheter necessary? Why? Is a precordial Doppler necessary? Explain.

What agent would you use for induction? Why? Explain your choice of muscle relaxant, if you are using one. Explain your choice of agents for maintenance. Suppose the surgeon asked you to give mannitol. How much is appropriate? Would hypertonic NS be a better option? Why/Why not? What is the expected effect of administering either of these agents? What are the potential problems with the administration of either of these agents?

During the craniotomy, the blood pressure decreases to 60/40 mmHg. What are the possible causes? The end-tidal CO₂ decreases as well. Cause? How can hypovolemia be differentiated from venous air embolism? Are there different treatments for each of these? PEEP? Does the presence of the atrial septal defect influence your management? After your first intervention, the hypotension persists. What is your next move? When are vasopressors indicated? Which would you choose? Why? Would you continue/restart the nitrous oxide? Explain.

The urine output is 4 mL/kg/h. What is your differential diagnosis? Which lab tests might be helpful? The serum sodium is 155 mEq/L. Diagnosis? Treatment? Which intravenous fluids would you use? Why? Should they contain glucose? Why? How do you determine the rate of administration?

How much blood loss is acceptable prior to transfusion? Why? Are there alternatives? What are the risks?

The operation takes 10 h. Is the child a candidate for extubation in the OR? Pros/cons? How would you minimize straining at extubation? Do you anticipate hypertension at the end of the case? Is this a problem? Why? Prevention/Treatment?

The possibility of raised ICP should be considered when planning whether or not to administer a premedication. In a child such as the one presented who does not have intracranial hypertension, an inhalation induction is appropriate, with or without a premedication, depending upon the patient’s (and the family’s) level of anxiety. Placement of an IV for induction is also appropriate and would allow a more rapid induction without the possibility of airway compromise that sometimes occurs during an inhalation induction and that would likely upset both the child and family. Ketamine is a potent cerebral vasodilator and also can cause sudden increases in ICP. Use of ketamine for this child is appropriate but may not be so as an induction agent in children with raised ICP. Intramuscular midazolam is another possibility for a particularly anxious, uncooperative child who refuses oral premedication. Barbiturates have some advantages in neurosurgical patients, since this class of drugs does lower both cerebral blood flow (CBF) and the cerebral metabolic rate for oxygen (CMRO2).

An arterial catheter is appropriate for cases such as this in which large fluid shifts or blood losses are possible and/or frequent monitoring of serum ABGs or electrolytes is planned. The radial artery is the most convenient and commonly used site, although the posterior tibial and dorsalis pedis arteries in the foot are also acceptable sites. Complications of arterial cannulation include arterial occlusion, flushing of emboli through indwelling catheters, ischemia distal to a catheter, and rarely, infection. A central venous catheter may be useful in this case as a measure of preload. For neurosurgical procedures, cannulation of the femoral vein is an attractive option. Not only is the insertion site accessible to the anesthesiologist who is at the patients side but also venous drainage from the head is not impaired. A CVP catheter is not useful in treating venous air embolism (VAE) except as a route for administration of resuscitation medications, should that become necessary. Given the possibility of DI, a urinary catheter is an important monitor. VAE is a possible complication of pediatric neurosurgical procedures. A precordial Doppler is the most sensitive monitor of VAE, detecting even minute, clinically insignificant amounts of air. The precordial Doppler is of limited use during electrocautery. Supplementing the Doppler with another monitor of VAE such as the capnograph or end-tidal nitrogen monitoring is helpful since these monitors are not affected by electrocautery [3].