ANESTHESIA FOR PEDIATRIC LAPAROSCOPY
Dr Sunita Goel
Lecturer in Anaesthesiology BJ Wadia Childrens hospital
Introduction:

Laparoscopy permits inspection of the abdominal and pelvic organs and the intraperitoneal space with cameras without disturbing the anatomic relationships of these structures. The laparoscopic approach to pediatric surgery reduces hospital costs, allows earlier hospital discharge and a more rapid return to a normal diet and full activity.

The premature and term neonates present the greatest differences in anatomy and physiology from adults. Children also have different psychological needs. The following is a very brief account on the essential aspects of Pediatric anesthesia

Physiological Changes:

Although the peri-operative management of children undergoing laparoscopy is essentially identical to that that for other intra-abdominal procedures, two factors conspire to make anesthesia challenging namely
  1. The creation of pneumoperitoneum and

  2. Extremes of patient positioning


Creation Of Pneumoperitoneum: The creation of pneumoperitoneum with insufflated gas permits visualization and manipulation of the abdominal viscera. The volume of insufflating gas necessary for pneumoperitoneum is much lower in children than adults. Adults require 2.5L to 5L where as a 10 kg patient needs about 0.9L. Safety precautions must be taken if one is using the verres insufflator needle - namely aspiration, injection and the hanging drop technique so that the serious consequences of gas embolism can be avoided. The risk of injuries to vascular and visceral structures from the verres needle is higher in infants. The ideal gas for insufflation would have
  • Minimal peritoneal insufflation

  • Minimal physiologic effects

  • Rapid excretion of any absorbed gas

  • Inability to support combustiona

  • Minimal effects from intravascular combustion

  • High blood solubility

Carbon dioxide (CO2) approaches the ideal insufflating gas. As Laparoscopy frequently involves the use of bipolar diathermy or lasers, this insufflated gas must not support combustion.

Disadvantages of CO2 for insufflation:
  • The chief drawback of CO2 is its significant vascular absorption across the peritoneum.

  • In prolonged procedures, hypercapnia can develop. Hypercapnia can also provoke sympathetic nervous system activity, leading to an increase in blood pressure, heart rate, myocardial contractility and arrhythmias. Hypercapnia also sensitizes the myocardium to catecholamines particularly when volatile anesthetic agents are used.

  • Massive intravascular embolization of any gas results in cardiovascular collapse and CO2 is no exception. Detection of embolized gas is difficult unless a precordial Doppler probe or TEE is in use. Following a CO2 embolism, capnography might not reveal any change in ETCO2 until late in the course of the event.

Intra-Abdominal Pressure (IAP): The creation of pneumoperitoneum raises the IAP, which has significant cardiovascular, respiratory and neurologic effects.

Cardiovascular Effects: The critical determinants are IAP and patient positioning. If the IAP is kept below 15mmHg, venous return actually is augmented as blood is squeezed out of the splanchnic venous bed, producing an increase in cardiac output. At IAP, levels greater than 15mmHg venous return decreases as the IVC is compressed. This results in decrease in cardiac output and arterial blood pressure. These cardiovascular changes are complicated by the patient's position during surgery. The head-up position favored for upper abdominal procedures e.g. Nissen's fundoplication and cholecystectomy further reduces venous return and cardiac output. This effect is more marked during fundoplication in which a greater degree of head up tilt (250-300) is required than for laparoscopic cholecystectomy (15-30 degrees). Conversely when the patient is positioned head down, as for pelvic Laparoscopy examination, venous return is augmented and blood pressure returns to normal or supra normal values. Other cardiovascular phenomena can result from insufflating gas into the peritoneum. Children have a high level of vagal tone and occasionally peritoneal stimulation by a blast of insufflated gas or penetrated by trocars and laparoscopes can provoke bradycardia or asystole. Patients with normal cardiovascular function tolerate variations in preload and afterload well, but those with cardiovascular disorders, anemia or hypovolemia require meticulous attention to volume loading, positioning and insufflation pressures.

Causes of cardiovascular collapse:
  • Vasovagal reflex to peritoneal stimulation

  • Myocardial sensitization

  • Decreased venous return secondary to reverse Trendelenburg position, IVC compression or high insufflation pressures.

  • Hypovolemia

  • Hypercapnia

  • Venous gas embolism


Respiratory Effects:


Increase IAP
Increase IAP
Decreased diaphragmatic excursion
Decreased diaphragmatic excursion
Shifts the diaphragm cephalad
Shifts the diaphragm cephalad
Early closure of small airways
Early closure of small airways
Increased in the peak airway pressure
Increased in the peak airway pressure
Decrease in the thoracic compliance


Upward displacement of the diaphragm leads to preferential ventilation of non-dependant parts of the lungs. This results in ventilation perfusion mismatch. This is accentuated during positive pressure ventilation and by the trendelenburg position


Fall in FRC below closing capacity
Fall in FRC below closing capacity
Small airway collapse
Small airway collapse
Atelectasis
Atelectasis
Intrapulmonary shunting
Intrapulmonary shunting
Hypoxemia


High IAP permits insufflated gas to gain access to tissue spaces, which explains occasional reports of pneumothorax and pneumomediastinum. A postoperative chest X-ray should be obtained.

Neurologic Effects Hypercapnia leads to increase in the systemic venous return, which combined with head down positioning lead to elevation in the ICP.

Endocrinologic Effects: Increase in the blood levels of 'stress hormones' i.e. insulin, cortisol, prolactin, epinephrine, blood levels of lactate, glucose and interleukin-6.

Perioperative Management: The child presenting for laparoscopic surgery should be managed in exactly the same way as any child presenting for surgery.

Premedication: Oralmidazolam 0.5- 0.75mg/kg 15-30mins preoperatively. The use of atropine is associated with lower incidence of cardiovascular and airway complications. One advantage of anticholinergic premedication is to prevent vasovagal reflexes that are occasionally seen when the peritoneum is penetrated.

Anesthesia Techniques:

  • Local

  • Regional

  • General

  • Intravenous (Preferred if venous access has been secured a can be performed with minimal discomfort using EMLA, prilocaine gel)

  • Inhalational - using sevoflurane or halothane in nitrous oxide and oxygen.

Emergency exploration: Rapid sequence intubation with cricoid pressure until a tracheal tube is securely in place to reduce the risk of pulmonary aspiration of gastric contents. Peripheral intravenous access should be obtained in all patients to allow continued hydration and drug administration.

Monitoring:
Continuous E.C.G

Automated N.I.B.P

Pulse Oximetry

Temperature

Capnography

Peripheral Nerve Stimulator

Spirometry, if available

Small children have a high body surface area to mass ratio and little subcutaneous fat or body hair to retain heat. Continuous insufflation of large volumes of cold, non-humidified CO2 directly in to the abdominal cavity also contributes to a major risk of hypothermia. A warming mattress, heated humidifier or a convective forced air warmer might be used, if available. An oro-nasogastric tube should be inserted after induction to permit deflation of the stomach, thus minimizing the chances of Verres needle accidentally perforating the inflated viscus.

Peri-operative Care: A balanced technique with controlled ventilation using inhalational agents, intravenous opioids, non-depolarizing neuromuscular blocking agents is preferred. The chief difference in anesthetic management between Laparoscopy and other abdominal procedures in children relates to the cardiorespiratory resulting from pneumoperitoneum and positioning. Ventilation should be controlled because this facilitates removal of exogenous CO2 and minimizes the reduction in FRC caused by a combination of increased IAP, Trendelenburg position and the use of volatile anesthetic agents. Minute ventilation needs to be increased by 20% or more to maintain normocapnia.

Pain Management: Pain following Laparoscopy results from a variety of maneuvers
  • Rapid distension of the peritoneum

  • Excitation of phrenic nerve with CO2

  • Unusual positions can stretch nerves


Pain is best controlled by multimodal approach of local anesthetics, NSAIDs and opioids. Local anesthetics can be injected intraperitoneally as well as infiltrated on the puncture sites. NSAID can be given oral, rectal, intramuscular and intravenous routes.

Post-operative Nausea And Vomiting (PONV): PONV is a common complication following Laparoscopy, delaying discharge from the hospital. A combination of drugs including 5-HT3 antagonist - ondansetron, dexamethasone and droperidol can be used.

Use Of LMA: The use of LMA is a remarkably useful adjunct to anesthesia for patients undergoing Laparoscopy. Although aspiration with LMA is low there has been no report with Laparoscopy and positive pressure ventilation.

High Risk Patients With Severe Myocardial Disease:
  • Avoid anesthetics, which directly depress the myocardium, or release histamine. Sevoflurane may be the agent of choice.

  • Pre-operative atropine prevents bradycardia especially with non-compliant ventricles having a fixed stroke volume to maintain cardiac output.

  • Avoid caudal/epidural as reduction in preload can lead to decrease in cardiac output.

  • TEE is preferred over CVP due to its accuracy in preload and myocardial contractility.

  • Pulmonary artery catheters for children weighing more than 15 kgs.

  • Arterial catheter for blood gas monitoring may be considered.

Summary: Knowledge of pathophysiological changes, adequate monitoring and good planning makes anesthesia for Laparoscopy safe in pediatrics.
How to Cite URL :
Goel S D. ANESTHESIA FOR PEDIATRIC LAPAROSCOPY. Pediatric Oncall [serial online] 2005[cited 2005 January 1];2. Art #16. Available From : http://www.pediatriconcall.com/Journal/Article/FullText.aspx?artid=748&type=J&tid=&imgid=&reportid=392&tbltype=
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