Changes in cerebral oxygenation based on intraoperative ventilation strategy.

INTRODUCTION: Cerebral oxygenation can be monitored clinically by cerebral oximetry (regional oxygen saturation, rSO2) using near-infrared spectroscopy (NIRS). Changes in rSO2 have been shown to precede changes in pulse oximetry, providing an early detection of clinical deterioration. Cerebral oximetry values may be affected by various factors, including changes in ventilation. The aim of this study was to evaluate the changes in rSO2 during intraoperative changes in mechanical ventilation. PATIENTS AND METHODS: Following the approval of the institutional review board (IRB), tissue and cerebral oxygenation were monitored intraoperatively using NIRS. Prior to anesthetic induction, the NIRS monitor was placed on the forehead and over the deltoid muscle to obtain baseline values. NIRS measurements were recorded each minute over a 5-min period during general anesthesia at four phases of ventilation: 1) normocarbia (35-40 mmHg) with a low fraction of inspired oxygen (FiO2) of 0.3; 2) hypocarbia (25-30 mmHg) and low FiO2 of 0.3; 3) hypocarbia and a high FiO2 of 0.6; and 4) normocarbia and a high FiO2. NIRS measurements during each phase were compared with sequential phases using paired t-tests. RESULTS: The study cohort included 30 adolescents. Baseline cerebral and tissue oxygenation were 81% ± 9% and 87% ± 5%, respectively. During phase 1, cerebral rSO2 was 83% ± 8%, which decreased to 79% ± 8% in phase 2 (hypocarbia and low FiO2). Cerebral oxygenation partially recovered during phase 3 (81% ± 9%) with the increase in FiO2 and then returned to baseline during phase 4 (83% ± 8%). Each sequential change (e.g., phase 1 to phase 2) in cerebral oxygenation was statistically significant (p < 0.01). Tissue oxygenation remained at 87%-88% throughout the study. CONCLUSION: Cerebral oxygenation declined slightly during general anesthesia with the transition from normocarbia to hypocarbic conditions. The rSO2 decrease related to hypocarbia was easily reversed with a return to baseline values by the administration of supplemental oxygen (60% vs. 30%).

Refractory Hypotension after Liver Allograft Reperfusion: A Case of Dynamic Left Ventricular Outflow Tract Obstruction.

Hypotension after reperfusion is a common occurrence during liver transplantation following the systemic release of cold, hyperkalemic, and acidic contents of the liver allograft. Moreover, the release of vasoactive metabolites such as inflammatory cytokines and free radicals from the liver and mesentery, compounded by the hepatic uptake of blood, may also cause a decrement in systemic perfusion pressures. Thus, the postreperfusion syndrome (PRS) can materialize if hypotension and fibrinolysis occur concomitantly within 5 min of reperfusion. Treatment of the PRS may require the administration of inotropes, vasopressors, and intravenous fluids to maintain hemodynamic stability. However, the occurrence of the PRS and its treatment with inotropes and calcium chloride may lead to dynamic left ventricular outflow tract obstruction (DLVOTO) precipitating refractory hypotension. Expedient diagnosis of DLVOTO with transesophageal echocardiography is extremely vital in order to avoid potential cardiovascular collapse during this critical period.

Pain management following myringotomy and tube placement: intranasal dexmedetomidine versus intranasal fentanyl.

PURPOSE: Despite the brevity of the procedure, bilateral myringotomy and tympanostomy tube placement (BMT) can result in significant postoperative pain and discomfort. As the procedure is frequently performed without intravenous access, non-parenteral routes of administration are frequently used for analgesia. The current study prospectively compares the efficacy of intranasal (IN) dexmedetomidine with IN fentanyl for children undergoing BMT. METHODS: This prospective, double-blinded, randomized clinical trial included pediatric patients undergoing BMT. The patients were randomized to receive either IN dexmedetomidine (1 µg/kg) or fentanyl (2 µg/kg) after the induction of general anesthesia with sevoflurane. All patients received rectal acetaminophen (40 mg/kg) and the first 50 patients also received premedication with oral midazolam. Postoperative pain and recovery were assessed using pediatric pain and recovery scales, and any adverse effects were monitored for. RESULTS: The study cohort included 100 patients who ranged in age from 1 to 7.7 years and in weight from 8.6 to 37.4 kg. They were divided into 4 groups with 25 patients in each group: (1) midazolam premedication+IN dexmedetomidine; (2) midazolam premedication+IN fentanyl; (3) no premedication+IN dexmedetomidine; and (4) no premedication+IN fentanyl. Pain scores were comparable when comparing groups 2, 3 and 4, but were higher in group 1 (midazolam premedication with IN dexmedetomidine). There was no difference in total time in the post-anesthesia care unit (PACU) or time from arrival in the PACU until hospital discharge between the 4 groups. The heart rate (HR) was significantly lower in group 3 when compared to the other groups at several different times after arrival to the PACU. No clinically significant difference was noted in blood pressure. CONCLUSION: Following BMT, when no premedication is administered, there was no clinical advantage when comparing IN dexmedetomidine (1 µg/kg) to IN fentanyl (2 µg/kg). The addition of oral midazolam as a premedication worsened the outcome measures particularly for children receiving IN dexmedetomidine.

Accuracy of noninvasive and continuous hemoglobin measurement by pulse co-oximetry during preoperative phlebotomy.

BACKGROUND: In recent years, the continuous noninvasive hemoglobin measurement has been offered by devices using advanced pulse oximetry technology. Accuracy has been established in healthy adults as well as in surgical and intensive care unit patients but not in the setting of acute hemorrhage. In this study, we evaluated the accuracy of such a device in the clinical setting of preoperative phlebotomy thereby mimicking a scenario of acute blood loss. METHODS: This prospective study included patients undergoing surgical repair of congenital heart disease (CHD) for whom preoperative phlebotomy was planned. Blood was removed after the induction of anesthesia and prior to the start of the surgical procedure. Replacement with crystalloid was guided by hemodynamic variables and cerebral oxygenation measured by near-infrared spectroscopy. Hemoglobin was measured by bedside whole blood analysis (total hemoglobin [tHb]) before and after phlebotomy, and concurrent measurements from the pulse co-oximeter (noninvasive, continuous, or spot-check testing of total hemoglobin [SpHb]) were recorded. RESULTS: The study cohort included 45 patients ranging in age from 3 months to 50 years. Preoperative phlebotomy removed an average of 9.2 mL/kg of blood that was replaced with an average of 7.2 mL/kg of crystalloid. The pre- and postphlebotomy tHb values were 13.0 ± 1.9 and 12.4 ± 1.8 g/dL, respectively. The absolute difference between the tHb and SpHb (▵Hb) was 1.2 ± 0.1 g/dL. Bland-Altman analysis revealed a bias of 0.1 g/dL, a precision of 1.5 g/dL, and 95% limits of agreement of -2.8 to 3.1 g/dL. In 52.2% of the sample sets, the SpHb was within 1 g/dL of the actual hemoglobin value (tHb), and in 80% of the sample sets, the SpHb was within 2 g/dL. No variation in the accuracy of the deviation was noted based on the patient's age, weight, or type of CHD (cyanotic versus acyanotic). CONCLUSION: The current study demonstrates that the accuracy of continuous, noninvasive hemoglobin measurement was not affected by acute blood loss simulated by preoperative phlebotomy. Although the device provided a clinically acceptable correlation with the actual hemoglobin value and offers the value of a continuous trend monitor, given the precision of the device, it does not appear that actual transfusion decisions can be based on the device alone.

Propofol and remifentanil for rapid sequence intubation in a pediatric patient at risk for aspiration with elevated intracranial pressure.

Aspiration is a significant cause of anesthetic morbidity, occurring most commonly during the induction of anesthesia. For patients with a high likelihood of aspiration, rapid sequence intubation (RSI) techniques may minimize this risk by reducing the time between the loss of protective airway reflexes and the placement of a cuffed endotracheal tube. Although RSI frequently involves the administration of a neuromuscular-blocking agent (NMBA) such as succinylcholine or rocuronium, there are times when the administration of an NMBA is contraindicated or undesirable. We present an 11-year-old boy who presented with vomiting, papilledema, and a history concerning for an undiagnosed neuromuscular disorder. Deep sedation or anesthesia was required during an emergent lumbar puncture to evaluate his symptoms. Rapid sequence intubation was successfully performed with propofol and remifentanil without the use of an NMBA. We highlight the anesthetic considerations in such a clinical scenario and review the literature regarding the combination of remifentanil and propofol for RSI.

Accuracy of the CNAP monitor, a noninvasive continuous blood pressure device, in providing beat-to-beat blood pressure readings in the prone position.

STUDY OBJECTIVE: To assess the accuracy of a noninvasive continuous arterial pressure (CNAP) monitor in patients who are positioned prone in the operating room. DESIGN: Prospective study. SETTING: Operating room at a children's hospital. PATIENTS: 20 pediatric patients, aged 13.8 ± 2 years, and weight 63.7 ± 18.8 kg, scheduled for surgery in the prone position, and for which arterial catheter placement was planned. INTERVENTIONS: Measurements were recorded with an arterial line (AL) and a new noninvasive continuous blood pressure (BP) monitor. MEASUREMENTS: Systolic (SBP), diastolic (DBP), and mean arterial (MAP) pressure readings were captured from an arterial cannula and the CNAP device every minute during anesthesia. MAIN RESULTS: The study cohort consisted of analysis of 4104 pairs of SBP, DBP, and MAP values, which showed an absolute difference between the AL and CNAP device readings of 7.9 ± 6.3 mmHg for SBP, 5.3 ± 4.3 mmHg for DBP, and 4.6 ± 3.9 mmHg for MAP. Bland-Altman analysis of MAP values showed a bias of 0.26 mmHg, with upper and lower limits of agreement of 12.18 mmHg and -11.67 mmHg, respectively. CNAP readings deviated from arterial values by ≤ 5 mmHg in 67% of MAP values, 59% of DBP values, and 43% of SBP readings. The difference was ≤ 10 mmHg for 94% of MAP readings, 90% of DBP values, and 73% of SBP readings. CONCLUSIONS: During prone positioning, the CNAP monitor provided clinically acceptable accuracy for MAP values, similar to those reported in adults in the supine position.

Ultrasound-guided trunk and core blocks in infants and children.

Regional anesthetic techniques for perioperative analgesia in children are being increasingly utilized with the reported advantages of providing superior analgesia, decreasing opioid consumption, and reducing opioid-related adverse effects. The following article reviews the available literature regarding core and trunk blocks in infants and children; specifically, transversus abdominis plane, ilioinguinal/iliohypogastric nerve, rectus sheath, lumbar plexus, and paravertebral and intercostal nerve blockade. The common indications and potential complications and adverse effects for each block are presented. Additionally, the anatomy and techniques needed for their performance are reviewed. Finally, a summary of the relevant literature in relation to each peripheral nerve block technique is included.

Cardiac arrest following ketamine administration for rapid sequence intubation.

Given their relative hemodynamic stability, ketamine and etomidate are commonly chosen anesthetic agents for sedation during the endotracheal intubation of critically ill patients. As the use of etomidate has come into question particularly in patients with sepsis, due to its effect of adrenal suppression, there has been a shift in practice with more reliance on ketamine. However, as ketamine relies on a secondary sympathomimetic effect for its cardiovascular stability, cardiovascular and hemodynamic compromise may occur in patients who are catecholamine depleted. We present 2 critically ill patients who experienced cardiac arrest following the administration of ketamine for rapid sequence intubation (RSI). The literature regarding the use of etomidate and ketamine for RSI in critically ill patients is reviewed and options for sedation during endotracheal intubation in this population are discussed.

Hemodynamic changes following the administration of propofol to facilitate endotracheal intubation during sevoflurane anesthesia.

BACKGROUND: The common intravenous anesthetic agent, propofol, is frequently reported to have negative inotropic and chronotropic effects. In the pediatric population, propofol is commonly used after inhalation induction to facilitate endotracheal intubation without the need for a neuromuscular blocking drug agent. In this setting, we have noted that propofol administration is commonly followed by tachycardia. The current study prospective evaluates heart rate and blood pressure changes following the administration of propofol to pediatric patients anesthetized with nitrous oxide (N2O) and sevoflurane. METHODS: ASA class 1 and 2 pediatric surgical patients were enrolled in the study. After premedication with midazolam and inhalation induction with N2O in oxygen and sevoflurane, a bolus dose of propofol was administered to facilitate endotracheal intubation. Heart rate (HR) was measured at baseline and at 30 second intervals following propofol administration. Blood pressure (MAP) was measured at baseline and 120 seconds post-administration. RESULTS: The study cohort consisted of 40 patients who ranged in age from 1 to 15 years. After inhalation induction, propofol (average dose of 2.6 mg/kg) was administered. The end-tidal N2O and sevoflurane concentrations were 62.2 ± 10.3% and 5.7 ± 1.1% respectively. Nineteen of 40 patients had a HR increase >10 bpm. When comparing these patients to those who did not experience a HR increase >10 bpm, there were no differences in the demographic data. Those with a HR increase received a greater dose of propofol when compared to patients whose HR change was <10 bpm (3.0 ± 0.8 versus 2.2 ± 0.5 mg/kg; p=0.0007). There was a significantly greater decreased in the MAP at 120 seconds following propofol administration in the group that did not sustain a >10 bpm HR increase. CONCLUSION: Tachycardia following propofol administration occurs in approximately 50% of pediatric patients despite preceding inhalation induction and concurrent administration of N2O and sevoflurane. Future studies are needed to define the mechanism for this effect.

Pain management after comprehensive stage 2 repair for hypoplastic left heart syndrome.

Achieving optimal pain control for children after complex cardiac surgery can be challenging. Recently, the hybrid approach to palliation of hypoplastic left heart syndrome (HLHS) was introduced as an alternative to the classic Norwood procedure. The second stage of the hybrid approach is a complex procedure known as comprehensive stage 2 (CS2). The authors have noted that pain control after the CS2 procedure is particularly difficult to manage. This report presents a review of the authors' pain management strategy in this clinical scenario and evaluates its efficacy. The medical records of patients who underwent CS2 repair of the hybrid procedure for HLHS between June 2008 and August 2011 were retrospectively reviewed. As a comparative group with a similar physiology, patients undergoing an isolated Glenn procedure also were reviewed. In addition to demographic data, the intraoperative use of narcotics and other adjunct medications for analgesia and sedation was recorded. Postoperatively, the mode of analgesia, the total opioid administered during the first 48 h postoperatively, and the nursing-assessed patient pain scores were recorded. Any adverse drug effect or need to adjust the analgesic regimen was recorded, as well as the timing of tracheal extubation. During the study period, 36 patients ranging in age from 4 to 14 months underwent the CS2 procedure, and 21 patients underwent a Glenn procedure. After CS2 repair, fentanyl was the opioid initially prescribed for all but 2 of the 21 patients managed with the nurse-controlled analgesia (NCA) delivery method and 15 patients managed with continuous infusion. After the Glenn shunt, all patients were prescribed NCA, with 20 patients receiving fentanyl and 1 patient receiving hydromorphone. The use of intraoperative dexmedetomidine caused a decrease in the total narcotic requirements, although this did not reach a statistical significance for either the extubated or intubated patients after CS2. The extubated patients who underwent the Glenn procedure received a smaller total equivalent dose of fentanyl during the first 24 h (29.02 ± 10.6 µg/kg) than did the extubated patients after the CS2 procedure, who received an average of 37.92 ± 8.5 µg/kg (P = 0.02). During the second 24 h, the extubated Glenn patients continued to receive less fentanyl, at an average dose of 7.02 ± 11.5 µg/kg compared with 27.7 ± 23.1 µg/kg for the CS2 patients (P = 0.02). The extubated patients who underwent the Glenn procedure required less NCA time (33.68 ± 17.7) than the CS2 patients (57.9 ± 31.8 h) (P = 0.04). Dexmedetomidine use with the CS2 patients resulted in a trend toward lowering of the total fentanyl dose, but this did not reach statistical significance. The intubated patients who received dexmedetomidine after the CS2 procedure had less NCA time (61.7 ± 39.2 vs. 128.1 ± 100 h; P = 0.02). After the CS2 procedure for palliation of HLHS, patients experience a complex pain profile that differs from the pain associated with the traditional Glenn procedure. This group of patients generally can be managed with fentanyl NCA. Achieving a balance between a proper level of analgesia and sedation in the setting of early tracheal extubation to optimize postoperative physiology can be challenging. The preliminary data suggest that improvements in pain management should be investigated given that more than 30 % of the pain scores in the CS2 group were in the moderate to severe range compared with 18 % after the Glenn procedure.

Cerebral oximetry monitoring during preoperative phlebotomy to limit allogeneic blood use in patients undergoing cardiac surgery.

Preoperative phlebotomy can minimize the need for allogenic blood products. Frequently, removed blood is replaced with intravenous fluids to maintain euvolemia (acute normovolemic hemodilution [ANH]). During cardiopulmonary bypass (CPB), ANH may present problems when the circuit prime causes further hemodilution and unacceptably low hemoglobin. This investigation aimed to demonstrate that minimum volume replacement after preoperative phlebotomy can be used safely when guided by cerebral oxygenation (rSO(2)) measured by near-infrared spectroscopy (NIRS). This prospective study included patients undergoing surgery for congenital heart disease. After preoperative phlebotomy, fluid replacement was guided by mean arterial pressure (MAP), heart rate, and rSO(2), which were measured at baseline, immediately after phlebotomy, and 15 and 30 min after phlebotomy. This study enrolled 38 patients ages 3 months to 50 years. Preoperative phlebotomy removed 9.3 ± 2.9 mL/kg of blood, and 5.6 ± 5.1 mL/kg of crystalloid was administered intraoperatively. Within 30 min after phlebotomy, 23 patients had a MAP decrease of 20 % or more from baseline. This fall in MAP coincided with a decrease in rSO(2) of 20 or more at 2 of 114 measured points. Initially, rSO(2) decreased from 74 ± 9 to 68 ± 10 but thereafter remained constant. On five occasions, rSO(2) decreased 20 or more from baseline, but no patient's NIRS value was less than 45. A decrease in rSO(2) occurred more commonly in younger patients and those who had a larger volume of blood removed. Preoperative phlebotomy without significant volume replacement can be performed safely before CPB. Volume replacement may be more appropriately guided by rSO(2) than by hemodynamic variables.

Chest wall rigidity in two infants after low-dose fentanyl administration.

Since its introduction into clinical practice, it has been known that fentanyl and other synthetic opioids may cause skeletal muscle rigidity. Involvement of the respiratory musculature, laryngeal structures, or the chest wall may impair ventilation, resulting in hypercarbia and hypoxemia. Although most common with the rapid administration of large doses, this rare adverse effect may occur with small doses especially in neonates and infants. We present 2 infants who developed chest wall rigidity, requiring the administration of neuromuscular blocking agents and controlled ventilation after analgesic doses of fentanyl. Previous reports regarding chest wall rigidity after the administration of low-dose fentanyl in infants and children are reviewed, the pathogenesis of the disorder is discussed, and treatment options offered.

Perioperative management of the pediatric patient with traumatic brain injury.

TBI and its sequelae remain a major healthcare issue throughout the world. With an improved understanding of the pathophysiology of TBI, refinements of monitoring technology, and ongoing research to determine optimal care, the prognosis of TBI continues to improve. In 2003, the Society of Critical Care Medicine published guidelines for the acute management of severe TBI in infants, children, and adolescents. As pediatric anesthesiologists are frequently involved in the perioperative management of such patients including their stabilization in the emergency department, familiarity with these guidelines is necessary to limit preventable secondary damage related to physiologic disturbances. This manuscript reviews the current evidence-based medicine regarding the care of pediatric patients with TBI as it relates to the perioperative care of such patients. The issues reviewed include those related to initial stabilization, airway management, intra-operative mechanical ventilation, hemodynamic support, administration of blood and blood products, positioning, and choice of anesthetic technique. The literature is reviewed regarding fluid management, glucose control, hyperosmolar therapy, therapeutic hypothermia, and corticosteroids. Whenever possible, management recommendations are provided.

Pain management after surgery for single-ventricle palliation using the hybrid approach.

The hybrid pathway for the management of patients with hypoplastic left heart syndrome was pioneered at our institution and is the preferred approach compared with the traditional Norwood pathway. Patients undergoing this surgery are generally <6 months of age, and pain management in this age group after surgery for complex congenital heart disease (CHD) may be particularly challenging. We retrospectively reviewed our pain-management strategy after stage 1 hybrid procedure (HS1) and evaluated its efficacy, especially in the setting of early tracheal extubation. We retrospectively reviewed the records of patients receiving fentanyl analgesia after HS1 palliation for single-ventricle anatomy between June 2008 and August 2011. In addition to demographic data, we also recorded the mode of analgesia, total fentanyl administered during the first 48 postoperative hours, and total hours of fentanyl use. Other data collected included pain scores, adverse effects, time of tracheal extubation, and use of adjunctive medications, such as dexmedetomidine. Nurse-controlled analgesia (NCA) with fentanyl was used in 21 of the 33 patients in the study cohort, with the remainder receiving a continuous fentanyl infusion. NCA-fentanyl was the method of choice in 12 of the 13 patients whose tracheas were extubated in the operating room versus 9 of 20 patients who received postoperative mechanical ventilation and tracheal intubation (p = 0.0093). During the first and second 24 h after surgery, fentanyl requirements were lower in patients whose tracheas were extubated (11.8 ± 7.6 vs. 20.6 ± 18.1 and 6.6 ± 10.3 vs. 24.3 ± 20.4 µg/kg, respectively). Adverse effects were noted in 3 of the 33 patients (9%) and included one episode each of respiratory depression requiring reintubation of the trachea, pruritus, and excessive sedation. Dexmedetomidine was used as an adjunct medication in 5 patients and resulted in decreased fentanyl use (6.3 ± 1.3 vs. 19 ± 15.9 µg/kg in the first 24 postoperative hours and 7.9 ± 3.5 vs. 19 ± 20.3 µg/kg in the second 24 postoperative hours). Fentanyl administered by way of continuous infusion or NCA provided effective postoperative analgesia with a limited adverse effect profile after HS1 surgery in neonates with complex CHD. Fentanyl requirements were lower in patients who achieved early tracheal extubation as well as those who received dexmedetomidine.

Dexmedetomidine as part of balanced anesthesia care in children with malignant hyperthermia risk and egg allergy.

Malignant hyperthermia is an acute hypermetabolic crisis triggered in susceptible patients by the administration of succinylcholine or a volatile anesthetic agent. When anesthesia care is provided to malignant hyperthermia-susceptible patients, a total intravenous anesthesia technique with propofol is frequently chosen. However, coexisting allergies to egg and soybeans may contraindicate the use of propofol. We present our experience with the use of dexmedetomidine as part of the anesthesia regimen in 3 patients with family histories of malignant hyperthermia and personal histories of egg or soybean allergies. In 2 patients, dexmedetomidine was used as part of a general anesthesia regimen and for sedation during spinal anesthesia in the third patient. Previous reports of the use of dexmedetomidine in patients susceptible to malignant hyperthermia are reviewed, and its benefits in such patients are discussed.