Anestesia Pediatrica e Neonatale

Introduction:

Laproscopy permits inspection of the abdominal and pelvic organs and the intraperitoneal space with cameras without disturbing the anatomic relationships of these structures. The laproscopic 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 presents 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 laproscopy is essentially identical to that that for other intra-abdominal procedures, two factors conspire to make anesthesia challenging namely

The creation of pneumoperitoneum and
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 combustion.
Minimal effects from intravascular combustion.
High blood solubility.
Carbon dioxide (CO2) approaches the ideal insufflating gas. As Laproscopy 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 (25º-30º) is required than for laproscopic cholecystectomy (15-30 degrees). Conversely when the patient is positioned head down, as for pelvic Laproscopy 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

↓

Decreased diaphragmatic excursion

↓

Shifts the diaphragm cephalad

↓

Early closure of small airways

↓

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

↓

Small airway collapse

↓

Atelectasis

↓

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 laproscopic surgery should be managed in exactly the same way as any child presenting for surgery.

Premedication:

Oral midazolam 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

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.

Perioperative 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 Laproscopy 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 Laproscopy 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.

Postoperative Nausea And Vomiting (PONV):

PONV is a common complication following Laproscopy, 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 Laproscopy. Although aspiration with LMA is low there has been no report with Laproscopy 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.
Preoperative atropine prevents bradycardia especially with noncompliant 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 Laproscopy safe in pediatrics.

Acknowledgements

We thank Dr. Sunita Goel, Pediatric Oncall and Dr. Ira Shah for professional collaboration with our Journal.

Dario Galante, MD
Scientific Manager of "Anestesia Pediatrica e Neonatale"

Anesthesia for Pediatric Laparoscopy

Sunita Goel, MD,
Consultant Pediatric Anesthetist,
Bai Jerbai Wadia Children's Hospital, Mumbai, India


		Anesthesia for Pediatric Laparoscopy
		Sunita Goel, MD, Consultant Pediatric Anesthetist, Bai Jerbai Wadia Children's Hospital, Mumbai, India Vol. 4, N. 1, Gennaio 2006
	Introduction: Laproscopy permits inspection of the abdominal and pelvic organs and the intraperitoneal space with cameras without disturbing the anatomic relationships of these structures. The laproscopic 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 presents 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 laproscopy is essentially identical to that that for other intra-abdominal procedures, two factors conspire to make anesthesia challenging namely The creation of pneumoperitoneum and 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 combustion. Minimal effects from intravascular combustion. High blood solubility. Carbon dioxide (CO2) approaches the ideal insufflating gas. As Laproscopy 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 (25º-30º) is required than for laproscopic cholecystectomy (15-30 degrees). Conversely when the patient is positioned head down, as for pelvic Laproscopy 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 ↓ Decreased diaphragmatic excursion ↓ Shifts the diaphragm cephalad ↓ Early closure of small airways ↓ 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 ↓ Small airway collapse ↓ Atelectasis ↓ 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 laproscopic surgery should be managed in exactly the same way as any child presenting for surgery. Premedication: Oral midazolam 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 a. Intravenous (Preferred if venous access has been secured à can be performed with minimal discomfort using EMLA, prilocaine gel) b. 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. Perioperative 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 Laproscopy 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 Laproscopy 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. Postoperative Nausea And Vomiting (PONV): PONV is a common complication following Laproscopy, 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 Laproscopy. Although aspiration with LMA is low there has been no report with Laproscopy 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. Preoperative atropine prevents bradycardia especially with noncompliant 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 Laproscopy safe in pediatrics. Acknowledgements We thank Dr. Sunita Goel, Pediatric Oncall and Dr. Ira Shah for professional collaboration with our Journal. Dario Galante, MD Scientific Manager of "Anestesia Pediatrica e Neonatale"

Anesthesia for Pediatric Laparoscopy

Sunita Goel, MD, Consultant Pediatric Anesthetist, Bai Jerbai Wadia Children's Hospital, Mumbai, India

Sunita Goel, MD,
Consultant Pediatric Anesthetist,
Bai Jerbai Wadia Children's Hospital, Mumbai, India