Gastrointestinal/hepatic problems
Potential anesthetic implications
Vomiting, diarrhea
Electrolyte imbalance, dehydration, full stomach
Gastroesophageal reflux
Treat like a full stomach
Increased abdominal volume
Diaphragmatic cephalic displacement
Decreased lung compliance
Decreased systemic oxygenation
Ab ingestis inhalation
Aspiration pneumonia
Pulmonary infiltrates
Decreased lung compliance
Increased V/Q mismatch
Increased pulmonary shunt effect
Decreased systemic oxygenation
Prolonged fasting
Dehydration, hypovolemia
Malabsorption
Anemia, malnutrition
Black stools
Anemia, hypovolemia
Jaundice
Drug metabolism/hypoglycemia
Liver dysfunction
Drug metabolism/toxicity
Echocardiography is performed to check for cardiovascular anomalies, right and left ventricle performances, and pulmonary pressure.
Lung function testings have been widely used in children 6–8 years of age or greater. Simple spirometry is easiest to obtain. The results of such tests are generally used as indicators of the complexity of perioperative management.
In patients about to be submitted to digestive surgery, the following procedures are indicated:
An effective optimization of preoperative therapy
An appropriate assessment of the need for blood products
An assessment of the presence and ultimate need for intravenous access with consideration of temporary or long-term central venous catheter
A rating for antibiotic needs
An analgesic perioperative plan
Risk evaluation and informed consent are essential elements in preoperative assessment. The American Society of Anesthesiologists developed and modified later the classification of physical status (ASA) to define a correlation of clinical condition and tolerance to surgery. The correct information about all possible anesthetic techniques (a pamphlet should be given before the anesthesiological visit) and in particular of the benefit/risk of the purpose tailored procedures must be provided before acquiring written consent for anesthesia. A specific risk such as difficult airway management, or cardiac, respiratory, neurological, and metabolic conditions, should be annotated on the anesthesiological chart and on the operatory list.
4.4 Premedication and Preoperative Fasting
At the end of the global evaluation (clinical history, physical examination, laboratory tests, imaging, cardiorespiratory tests), a pharmacological medication is considered. Sedative premedication is not always necessary, but when useful, midazolam 500 mcg/kg, orally, is currently the most frequently used drug. Midazolam can also be administered by nasal route (200 mcg/kg). Atropine in clinical practice is administered after vein placement only in the presence of clinical need. A local anesthetic emulsion (lidocaine 25 mg + prilocaine 25 mg) or medicated plaster (lidocaine 70 mg + tetracaine 70 mg, for children over 3 years) is applied on a detectable peripheral vein. Preoperative fasting is indicated for elective surgery and healthy patients, to avoid inhalation syndrome at anesthesia induction. Recent guidelines also consider the correct preoperative administration of drugs to decrease the risk for pulmonary aspiration in selected patients [6]. Parents are allowed to be present in the operating room at induction of anesthesia.
4.5 Anesthesiological Approach
Studies in the literature consider it very important in these patients to achieve a level of anesthesia which allows a safe execution of the surgical procedure. The entire staff, involving different professional figures, should be trained and educated in order to improve safety, ensure treatment of possible side effects, and guarantee the management of emergencies [7].
4.5.1 Monitoring
Standard intraoperative monitoring is both invasive and noninvasive and is well described in the guidelines for safety in the operating room.
Cardiovascular function is monitored by ECG (heart rate and rhythm), noninvasive systolic blood pressure (SBP), and diastolic blood pressure (DBP); if necessary, a radial arterial catheter is cannulated not only for invasive monitoring but also for intraoperative and postoperative blood gas analysis and laboratory tests. When clinical conditions and the fluid requirements are difficult to evaluate, a central venous catheter (CVC) is placed by a superior cava approach for invasive monitoring of central venous pressure (CVP).
The respiratory function is monitored by peripheral arterial oxygen saturation (SpO2) and end-tidal CO2 (ETCO2). The mechanical ventilator permits the variation of all respiratory items including frequency, tidal volume (inspiratory and expiratory), minute volume, peak pressure, and mean airway pressure.
Monitoring also includes body temperature, urine output, and inspiratory and expiratory concentration of volatile anesthetics. In many patients, the neuromuscular blockade is monitored by stimulating the ulnar nerve using the train-of-four pattern of stimulation.
Temperature measurement is a must in pediatric abdominal surgery and in particular in neonates. The temperature is tested with the esophageal probe during major surgery. The use of pre-warmed fluids and active warming systems (mattress, convective warm air blanket, radiant heater) is necessary. Anesthesia interferes with the thermoregulatory response in all ages.
A new approach is oriented to measure cerebral oxygenation (using near-infrared spectroscopy technology) to reduce potential risks of neurolesive events caused by conventional intraoperative ventilation that influence intracranial pressure, cerebral blood flow, and cerebral perfusion pressure [8, 9].
4.5.2 Vascular Access
Vascular access is necessary in all types of surgery.
Adequate peripheral access is essential intraoperatively and also for fluid replacement in the postoperative period. One or two peripheral veins may be necessary.
Clinical conditions and the type of surgery indicate the placement of a single- or double-lumen central venous catheter, appropriate for the size of the patient. This vascular access is required both for monitoring and for rapid and safe infusions of fluid, plasma expanders, and blood derivatives. The upper cava vein approach is mandatory for the liver and oncologic abdominal surgery, particularly when it has been extended to or into the inferior cava vein (rarely until the right atrium), and surgery may foresee vein clamping. The use of ultrasonographic guidance during CVC placement has been demonstrated the better percutaneous procedure for decreasing the complications rate [10].
4.5.3 Intraoperative Fluids
Intra-surgical crystalloid infusion was 20 ml/kg during the first hour in patients under 3 years and 15 ml/kg for older patients; in the hours that followed, the infusion dosage was 8–10 ml/kg/h for all patients.
Extravascular or interstitial sequestration of fluid (the so-called “third-space” fluid loss) can occur during digestive surgery. Estimated third-space fluid deficits are replaced with isoosmotic fluids, at rates according to the type of surgery (approximately 4 ml/kg). The infusion used was 0.8–1 % dextrose in polyelectrolyte solution or in quarter-strength normal saline solution (0.2 % NaCl) and lactated Ringer’s solution [11–13].
4.5.4 Anesthetic Techniques
General anesthesia is increasingly associated with regional anesthetic techniques, to optimize anesthesia and analgesia results throughout the perioperative period.
4.5.4.1 General Anesthesia (GA)
Anesthetic management can be performed by inhalation or intravenous hypnotics, associated with neuromuscular blocking agents, opioids, and adjuvant drugs, if necessary. Anesthesiological management, today, foresees combined general-regional anesthesia.
Balanced anesthesia is the most common GA applied, in which a mixture of small amounts of several drugs, administered by different routes (inhalation + intravenous), permits a correct anesthetic plan for the surgery. Recently, total intravenous anesthesia (TIVA) is chosen for pediatric patients. In all pediatric ages and in particular in neonates, many drugs cannot be legally used. The bispectral index is designed to observe the anesthetic plan and drug consumption although results do not differ from those of conventional clinical practice (Table 4.2) [14].
Table 4.2
Drugs used during digestive general anesthesia in pediatric age
Drug | Induction doses | Maintaining doses |
|---|---|---|
Anesthetic agents | ||
Sevoflurane* | 1–8 % | 2–3.5 % |
Thiopental | 3–6 mg/kg | |
Propofol | 2.5–3 mg/kg | 9–12 mg/kg/h |
Opioids | ||
Fentanyl | 1–2 mcg/kg | 1–3 mcg/kg/h |
Alfentanil | 7–15 mcg/kg | 0.5–1.5 mcg/kg/min |
Remifentanil | 0.5–1 mcg/kg | 0.3–1 mcg/kg/min |
Neuromuscular blocking agents | ||
Atracurium besylate | 0.3–0.5 mg/kg | 0.2–0.4 mg/kg/h |
Cisatracurium besylate | 0.15–0.25 mg/kg | 0.1–0.3 mg/kg/h |
Vecuronium | 0.08–0.1 mg/kg | 0.06–0.08 mg/kg/h |
Rocuronium | 0.6 mg/kg | 0.3–0.6 mg/kg/h |
Inhalation Agents
Sevoflurane is a halogenated general inhalation anesthetic drug and to date the most frequently drug employed in pediatric anesthesia. It is administered by vaporization vehicled by O2/medical air at different FiO2. The minimum alveolar concentration (MAC) in neonates (3.3 %) and children until 3 months (3.2 %) is similar, but older infants and children have a lower MAC of approximately 2.5 %. During mask induction, the incidence of agitation is near 14 %, but laryngospasm and bronchospasm are present in around 1 or 2 %. It is quite clear that the concomitant use of opioids requires a lower halogenated concentration. Inhalation anesthesia consents a rapid recovery, but agitation is frequently present and is considered an adverse effect [15–17].
Intravenous Agents
Although in the past years sodium thiopentone, belonging to the pharmacological class of barbiturates, was considered the most commonly used intravenous agent for anesthesia induction, propofol is now the most frequently employed induction agent (1.5–3 mg/kg) in pediatric age. The current and recent literature contains many reports of good results in particular for anesthesia induction in procedural deep sedation [18–20]. In preterm neonates and in the first 10 days of life, there is a risk of propofol accumulation if given both for an intermittent bolus and infusion. It would seem sensible at present to limit its use to single-bolus administration [21–24].
4.5.4.2 Regional Anesthesia (RA)
It is generally accepted that RA provides safe and effective pain relief, as it provides the block of sensory transmissions [25, 26]. Regional anesthetic techniques also in pediatric patients provide safe and effective pain relief during and after surgery with different techniques [27].
A recent study of the ADARPEF revealed a low incidence of complications related to regional anesthetic techniques and concludes that RA has a good efficacy and safety [28]. The application of pediatric regional anesthesia blocks has increased in recent years; neuraxial blocks are applied in all ages and peripheral blocks are rapidly expanding especially in children aged 5 years or older. In pediatrics RA is performed under GA or deep sedation to reduce potential damages from a loss of behavioral control during the procedure and to keep hypnosis during surgery. However, RA reduces intraoperative anesthetic requirements, supporting recovery and early ambulation and shortening the time to rehabilitation [29, 30]. A necessary condition to obtain the most benefits from RA is the knowledge and expertise of the specialist who chooses and applies the techniques and appropriate and adequate equipment and devices. Ultrasound guidance is the best clinical practice both for neuraxial and peripheral blocks. Ultrasonography could augment the success rate, since it allows anatomical structures and nerves to be visualized, permits the needle location to be identified, and reduces the amount of local anesthetic administered [31].
The drugs used are local anesthetics and opioids for both top-up boluses and continuous infusion. It should be noted that the binding of local anesthetics with plasmatic protein (albumin and α-glycoprotein) is reduced in both newborn and infants and can result in an accumulation of the drugs themselves, especially if a continuous infusion is planned, with potential toxic risks.
Currently, selected local anesthetics for pediatric techniques are left-handed enantiomers (levobupivacaine and ropivacaine), and this makes the technique safer. The association of local anesthetics with opioids allows the use of low doses of both. Morphine, which was once the most widely used opioid, owing to the increased incidence of respiratory depression, vomiting, and itching, is now often replaced by fentanyl.
Neuraxial Blocks
Central neuraxial bock is suggested for patients undergoing major abdominal surgery. In the spinal approach, drugs are administered intrathecally into the cerebrospinal fluid, in epidural approach into the fatty tissues surrounding the dura [32]. Absolute contraindications are local infection at injection site, hypovolemia, shock, coagulopathy, high intracranial pressure, allergy to local anesthetics, and parent refusal. Relative contraindications include sepsis, neurological dysfunction, and anatomic abnormalities. Neurological injury, infection, ischemia, seizures, hypotension, and cardiac arrest are the risks of neuraxial anesthesia. It should be remembered that there are some anatomical differences between adults and children in the lumbosacral region [33].
Caudal Epidural Block
Epidural block by caudal route, the most popular technique in pediatrics, is suggested in herniorrhaphy and other pathologies with surgical under umbilical approach. The caudal space is easy to find in patients less than 7 years of age, when block is commonly performed. The sacral hiatus is found by searching for a triangle with the base formed by a line joining the right and left sacral cornea and the apex at the lower IV sacral vertebrae. The sacral hiatus is situated higher in children than in adults. The dedicated needle passes, at a nearly 45° angle, through the sacrococcygeal ligament, and after loss of resistance, the local anesthetic is injected. This block is more frequently used as a “single shot.” Adjuvants may be added to prolong the duration of analgesia. Over the past several years, caudal catheters were introduced upward even to thoracic level especially in neonates and infants, but this technique is no longer recommended, because of the risk of fecal soiling [34, 35].
Lumbar Epidural Block
In contrast to the caudal block, lumbar epidural block is rarely used as a single injection, and usually a catheter is inserted. Catheter placement is based on surgical incision location corresponding to segmental levels to target analgesia. This technique should be performed by experienced anesthesiologists. In very small infants, epidural needles are inserted below L4 so, to achieve the desired segmental level, the catheters should be threaded for a long segment, monitoring the efficacy of the pain relief. Currently, the indication is to decrease the distance of insertion to as short as 3–4 cm inside the epidural space. Central blocks have a history of more than 100 years in adults, but in pediatrics RA was rarely applied/described [36, 37] and became an essential integrated, safe, and effective analgesic system producing excellent intraoperative analgesia, less than 20 years ago, when Anand published his work [38].
Peripheral Nerve Blocks
Peripheral nerve blocks are a valid alternative to the neuraxial technique, with good sensory block and without the major complications of central block. Sympathetic block and hemodynamic changes are minimal as well as motor block and urinary retention. The use of neurostimulation and ultrasonography is recommended although, in the latter case, evidence is not strong. The length of block depends on the pharmacokinetics of the local anesthetic, long-acting anesthetics such as levobupivacaine or ropivacaine are preferred, while adjuvants such as clonidine may extend the duration.
Ilioinguinal-Iliohypogastric Nerve Block
This block may be used for surgical procedures in the inguinal region such as herniorrhaphy. Using a landmark technique, the puncture site is about 1 cm medial to the anterior superior iliac spine, but this traditional technique is burdened with high failure rates. The point of injection by ultrasound is more lateral, and the transversus abdominis/internal oblique fascial plane needs to be identified, where the nerves could be found [39].
Rectus Sheath Block
A rectus sheath block provides effective pain relief and muscle relaxation for laparoscopic surgery and other small midline incisions. It is performed bilaterally, between the rectus abdominis muscle and the posterior rectus sheath. The unpredictable depth of the posterior rectus sheath in children is a good argument for the use of ultrasound together with the advantage of allowing visualization of the bowel, which may decrease accidental puncture [40].
Transversus Abdominis Plane (TAP) Block
TAP block is effective in laparoscopic procedures and open surgery. Its use is limited by the need for bilateral blocks when the incision crosses the midline. This, like the other abdominal wall blocks described above, is effective for somatic pain but not for visceral pain. TAP block may be useful when epidural analgesia is contraindicated. Local anesthetic should be placed between the internal oblique and transversus abdominis muscles; the triangle of Petit is used as landmark for injection; a relatively large volume of anesthetic is required [41].
Local Wound Infiltration
Local wound infiltration is a component of multimodal postoperative analgesia. The single-shot infiltration of local anesthetics in laparoscopic working ports is more commonly performed than continuous wound infiltration for fear of complications. Also intraperitoneal instillation was rarely performed, although a systematic review and meta-analysis of its effectiveness in adults have given promising results [42].
4.5.5 Intraoperative Ventilation
The aim of intraoperative ventilation techniques is to maintain normal levels of oxygenation and normocapnia. The aim to facilitate the digestive intervention and the advice to avoid high pressure in the airway should be remembered.
Pulmonary mechanical ventilation for these patients reflects the traditional intraoperative ventilation techniques. Patients were mechanically ventilated using an oxygen/air mixture with oxygen inspired fraction (FiO2) between 0.35 and 0.50; tidal volume was adjusted between 9 and 10 ml/kg, and respiratory rate (RR) was regulated on the basis of the patient’s age. The ratio of inspiratory time to expiratory time was usually 1:2. Positive end-expiratory pressure (PEEP) was set at 3–4 cm H2O.
4.6 Laparoscopy in Digestive Surgery
Laparoscopic videosurgery is becoming increasingly more important in pediatric abdominal surgery for both the diagnosis and surgical treatment. Several authors who have compared this technique to traditional surgery for the treatment of some pathologies have reported reduced surgical trauma, less postoperative pain, reduced perioperative morbidity, shorter period of postoperative ileus, earlier postoperative mobilization, shorter periods of disability, shorter hospital stays, and better cosmetic results in favor of laparoscopic videosurgery [43–45]. Other benefits, compared to traditional “open” operative techniques, include the avoidance of large incisions, less fluid loss, heat, and forced retraction of tissues.
An optimal approach to the planning of anesthesia for laparoscopy depends on a knowledge of the technical requirements and an understanding of the physiological alterations associated with the procedure.
Physiological changes during laparoscopic surgery are related to the changes associated with the increased abdominal pressure associated with insufflation of the abdomen, the patient’s postural modifications (head-up or head-down), and the CO2 absorption and its general effects [46].
The magnitude of the physiological perturbations associated with laparoscopy is influenced by the patient’s age, the patient’s underlying myocardial and respiratory function, and the administered anesthetic agents.
Tension pneumoperitoneum causes an elevation in intra-abdominal pressure (IAP) which produces important effects on cardiovascular, pulmonary, renal, and metabolic function.
4.6.1 Effects on Respiratory System
Pneumoperitoneum and increase in IAP cause cephalic displacement of the diaphragm, resulting in the reduction in lung volumes including vital capacity, total lung volume, and functional residual capacity (FRC). This phenomenon is exacerbated by cephalic shift of the abdominal contents in the head-down position. Pulmonary compliance is reduced and airway resistance is increased, producing a higher airway pressure for any given tidal volume with an increased risk of hemodynamic changes and barotrauma during intermittent positive pressure ventilation (IPPV). Restriction in diaphragmatic mobility promotes uneven distribution of ventilation to the nondependent part of the lung, resulting in ventilation-perfusion mismatch with hypercarbia and hypoxemia. This preferential ventilation is increased further by supine position, inhalational anesthetic agents, and neuromuscular blockade [47, 48].
Another important respiratory implication is represented by CO2 insufflation. Insufflated CO2 is rapidly absorbed across the peritoneum and can lead to an increase in the total body CO2 content. If ventilation is controlled and not changed in response to this increase, then the arterial pCO2 will rise.
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