Bispectral index monitoring during infant cardiac surgery: relationship of BIS to the stress response and plasma fentanyl levels.

BACKGROUND: We evaluated the relationship of the bispectral index (BIS) to commonly used indices of depth of anaesthesia in 19 infants enrolled in a prospective study of the stress response to hypothermic cardiopulmonary bypass. METHODS: Group 1 (n=8) received high-dose fentanyl by bolus technique; group 2 (n=6) received high-dose fentanyl by continuous infusion; and group 3 (n=5) received a fentanyl-midazolam infusion. Blood pressure (BP), heart rate (HR) and plasma epinephrine, norepinephrine, cortisol, ACTH, glucose, lactate and fentanyl were analysed 15 min postinduction, 15 min poststernotomy, 15 min on CPB during cooling and during skin closure. RESULTS: Mean BIS (SD) values for all 19 patients were 45.3 (12.3), 40.4 (14.5), 24.4 (12.4) and 47.9 (13.9), at the successive time points. No significant differences were observed in changes in BIS over time between the groups. A significant correlation was found 15 min postinduction between BIS and BP (systolic r=0.51, mean r=0.56) in all groups, but not between BIS and HR. BIS did not correlate with BP or HR at any other time point. There was no significant correlation between BIS and hormonal, biochemical or plasma fentanyl levels for any group at any time point. CONCLUSIONS: We were unable to demonstrate a relationship between the BIS and haemodynamic, metabolic or hormonal indices of anaesthetic depth. Further evaluation of the BIS algorithm is required in neonates and infants.

Stress response in infants undergoing cardiac surgery: a randomized study of fentanyl bolus, fentanyl infusion, and fentanyl-midazolam infusion.

UNLABELLED: There have been significant changes in the management of neonates and infants undergoing cardiac surgery in the past decade. We have evaluated in this prospective, randomized, double-blinded study the effect of large-dose fentanyl anesthesia, with or without midazolam, on stress responses and outcome. Forty-five patients < 6 mo of age received bolus fentanyl (Group 1), fentanyl by continuous infusion (Group 2), or fentanyl-midazolam infusion (Group 3). Epinephrine, norepinephrine, cortisol, adrenocortical hormone, glucose, and lactate were measured after the induction (T1), after sternotomy (T2), 15 min after initiating cardiopulmonary bypass (T3), at the end of surgery (T4), and after 24 h in the intensive care unit (T5). Plasma fentanyl concentrations were obtained at all time points except at T5. Within each group epinephrine, norepinephrine, cortisol, glucose and lactate levels were significantly larger at T4 (P values < 0.01), but there were no differences among groups. Within groups, fentanyl levels were significantly larger in Groups 2 and 3 (P < 0.001) at T4, and among groups, the fentanyl level was larger only at T2 in Group 1 compared with Groups 2 and 3 (P < 0.006). There were no deaths or postoperative complications, and no significant differences in duration of mechanical ventilation or intensive care unit or hospital stay. Fentanyl dosing strategies, with or without midazolam, do not prevent a hormonal or metabolic stress response in infants undergoing cardiac surgery. IMPLICATIONS: We demonstrated a significant endocrine stress response in infants with well compensated congenital cardiac disease undergoing cardiac surgery, but without adverse postoperative outcome. The use of large-dose fentanyl, with or without midazolam, with the intention of providing "stress free" anesthesia, does not appear to be an important determinant of early postoperative outcome.

The effects of thoracic epidural analgesia with bupivacaine 0.25% on ventilatory mechanics in patients with severe chronic obstructive pulmonary disease.

UNLABELLED: Optimal analgesia is important after thoracotomy in pulmonary-limited patients to avoid pain-related pulmonary complications. Thoracic epidural anesthesia (TEA) can provide excellent pain relief. However, potential paralysis of respiratory muscles and changes in bronchial tone might be unfavorable in patients with end-stage chronic obstructive pulmonary disease (COPD). Therefore, we evaluated the effect of TEA on maximal inspiratory pressure, pattern of breathing, ventilatory mechanics, and gas exchange in 12 end-stage COPD patients. Pulmonary resistance, work of breathing, dynamic intrinsic positive end-expiratory pressure, and peak inspiratory and expiratory flow rates were evaluated by assessing esophageal pressure and airflow. An increase in minute ventilation (7.50 +/- 2.60 vs 8.70 +/- 2.10 L/min; P = 0.04) by means of increased tidal volume (0.46 +/- 0.16 vs 0.53 +/- 0.14 L/breath; P = 0.003) was detected after TEA. These changes were accompanied by an increase in peak inspiratory flow rate (0.48 +/- 0.17 vs 0.55 +/- 0.14 L/s; P = 0.02) and a decrease in pulmonary resistance (20.7 +/- 9.9 vs 16.6 +/- 8.1 cm H(2)O. L(-1). s(-1); P = 0.02). Peak expiratory flow rate, dynamic intrinsic positive end-expiratory pressure, work of breathing, PaO(2), and maximal inspiratory pressure were unchanged (all P > 0.50). We conclude that TEA with bupivacaine 0.25% can be used safely in end-stage COPD patients. IMPLICATIONS: Thoracic epidural anesthesia with bupivacaine 0.25% does not impair ventilatory mechanics and inspiratory respiratory muscle strength in severely limited chronic obstructive pulmonary disease patients. Thus, thoracic epidural anesthesia can be used safely in patients with end-stage chronic obstructive pulmonary disease.

Parameters associated with perioperative baffle fenestration closure in the Fontan operation.

OBJECTIVE: To identify clinical parameters indicating perioperative fenestration closure in children who underwent the fenestrated Fontan operation. DESIGN: Retrospective. SETTING: Single children's hospital. PARTICIPANTS: Patients who underwent a fenestrated Fontan operation in 1996 through 1997 (n = 101). INTERVENTION: A fenestrated Fontan operation was performed in children with single-ventricle physiology. MEASUREMENTS AND MAIN RESULTS: Early perioperative closure of the fenestration occurred in 14 patients (group 1), whereas the fenestration remained patent in 87 patients (group 2). The groups were compared by the following parameters: demographics, cardiac catheterization and ultrasound data, and use of aspirin or warfarin preoperatively and intraoperatively by assessing the composition of the cardiopulmonary bypass solution, use of ultrafiltration and antifibrinolytics, protamine dose, last hematocrit on cardiopulmonary bypass, and requirement of blood products. Immediately postoperatively in the intensive care unit (ICU), cardiac filling pressures (central venous and left atrial pressure), coagulation profile, cardiac rhythm, chest tube drainage, length of stay in the ICU, and use of atrial pacing were reviewed. Significant indicators of early fenestration closure in this study as determined by multivariate stepwise logistic regression were a high transpulmonary pressure gradient (p = 0.015) and a higher oxygen saturation (p = 0.001) 1 hour after arrival in the ICU, a low fibrinogen level (p < 0.0001), and the need for temporary atrial pacing (p = 0.029). The fenestration was reopened in 13 patients in group 1. In 101 patients, there was no early mortality, and all patients survived to discharge. CONCLUSION: Factors that correlated with postoperative fenestration closure in the fenestrated Fontan operation in this study were a high transpulmonary pressure gradient and a high oxygen saturation 1 hour after arrival in the ICU, a low fibrinogen level, and the need for temporary atrial pacing.

Synthetic antifibrinolytics are not associated with an increased incidence of baffle fenestration closure after the modified Fontan procedure.

OBJECTIVE: To determine if the lysine analog antifibrinolytic agents, epsilon-aminocaproic acid and tranexamic acid, are associated with early closure of the baffle fenestration after the modified Fontan procedure. DESIGN: Retrospective chart review. SETTING: University hospital. PARTICIPANTS: Seventy-four successive patients underwent the modified Fontan procedure. Three patients received aprotinin and were excluded. A total of 71 patients were analyzed. INTERVENTIONS: Charts were examined for variables known to be associated with baffle fenestration closure in the modified Fontan procedure. MEASUREMENTS AND MAIN RESULTS: Occurrence of baffle fenestration closure, oxygen saturation, central venous pressure, left atrial pressure, transpulmonary gradient, chest tube drainage volume, chest tube drainage duration, intensive care unit (ICU) duration, and total inpatient duration were compared between the 33 patients who received antifibrinolytics and the 38 patients who did not. One patient of 71 had baffle fenestration closure in the first 48 hours after surgery. Oxygen saturation, central venous pressure, left atrial pressure, transpulmonary gradient, chest tube drainage volume, chest tube drainage duration, days in ICU, and total inpatient duration were not significantly different between the two groups. CONCLUSIONS: Use of epsilon-aminocaproic acid and tranexamic acid is not associated with early baffle fenestration closure after the modified Fontan procedure. It is concluded that these agents can be used without increasing the risk of spontaneous baffle fenestration closure.

Reactive hyperemia in skin after cardiopulmonary bypass.

OBJECTIVE: To study reactive hyperemia (RH) using a transcutaneous PO2/PCO2 combination electrode heated to 37 degrees C and tissue reflectance spectrophotometry in patients before and after cardiopulmonary bypass (CPB) to determine whether microcirculatory function of skin is altered. DESIGN: Prospective study. SETTING: Anesthesiology and critical care unit of a university hospital. PARTICIPANTS: Eight patients undergoing elective CPB under mild hypothermia. INTERVENTIONS: To produce RH, blood flow to the forearm was prevented by inflation of a cuff to 300 mmHg for an interval of 5 minutes. MEASUREMENTS AND MAIN RESULTS: Measurements were obtained on the day prior to surgery (DPS), on the day of surgery (DOS) rewarmed to 37 degrees C in the intensive care unit (ICU), and on the first (POD 1) and the third postoperative days (POD 3). The following parameters were recorded: preocclusive baseline cutaneous PO2, and PCO2 (B-PtcO2, B-PtcCO2), and microvascular hemoglobin saturation (B-HbO2); postischemic peak of PtcO2, PtcCO2, and HbO2; and 10 minutes after release of the cuff occlusion posthyperemic PtcO2, PtcCO2, and HbO2. B-PtcO2 was 3.5 +/- 1.2 mmHg on DPS, 2.6 +/- 0.7 mmHg on DOS, 1.5 +/- 0.3 mmHg on POD 1, and 3.5 +/- 3.5 mmHg on POD 3. B-PtcCO2 increased significantly from 40.1 +/- 2.5 mmHg to 52.2 +/- 2.0 mmHg on DOS (p = 0.01) and to 48.9 +/- 3.6 mmHg on POD 1 (p = 0.02). On POD 3, B-PtcCO2 was 40.6 +/- 2.6 mmHg. B-HbO2 declined from a preoperative value of 42.4% +/- 8.6% to 37.1% +/- 14.7% on DOS and further to 21.7% +/- 4.8% on POD 1, which was significantly different (p = 0.03). On POD 3, B-HbO2 still remained lower (30.7% +/- 6.2%) compared with the preoperative value. RH (deltaPtcO2, deltaHBO2) was quantified as the differences between peak PtcO2, HBO2 and B-PtcO2, B-HBO2. DeltaPtcO2 was 13.0 +/- 2.3 on DPS, 11.3 +/- 2.9 on DOS, 12.6 +/- 2.6 on POD 1, and 11.5 +/- 3.5 on POD 3. DeltaHBO2 was 42.0 +/- 5.6 on DPS, 40.0 +/- 7.1 on DOS, 49.9 +/- 2.5 on POD 1, and 52.9 +/- 6.4 on POD 3. The elimination rate of carbon dioxide from skin (ECO2) was calculated as difference between peak PtcCO2 and PtcCO2 after 3 minutes of reperfusion divided by the difference between peak PtcCO2 and B-PtcCO2. ECO2 was 1.0 +/- 0.2 kPa/min on DPS, 0.7 +/- 0.1 kPa/min on DOS, and 0.8 +/- 0.1 kPa/min on POD 1 and POD 3. CONCLUSION: Cutaneous microcirculation assessed by RH is well preserved during the immediate postoperative period in patients undergoing uncomplicated coronary artery surgery with CPB.

The effect of hematocrit on cerebral blood flow velocity in neonates and infants undergoing deep hypothermic cardiopulmonary bypass.

UNLABELLED: Varying degrees of hemodilution are used during deep hypothermic cardiopulmonary bypass. However, the optimal hematocrit (Hct) level to ensure adequate oxygen delivery without impairing microcirculatory flow is not known. In this prospective, randomized study, cerebral blood flow velocity in the middle cerebral artery was measured using transcranial Doppler sonography in 35 neonates and infants undergoing surgery with deep hypothermic cardiopulmonary bypass. Patients were randomized to low Hct (aiming for 20%) or high Hct (aiming for 30%) during cooling on cardiopulmonary bypass (CPB). Systolic (V(s)), mean (Vm), and diastolic (Vd) cerebral blood flow velocity, as well as pulsatility index (PI = [V(s) - Vd]/Vm) and resistance index (RI = [V(s) - Vd]/V(s)) were recorded at six time points: postinduction, at cannulation, after 10 min cooling on CPB, rewarmed to 35 degrees C on CPB, immediately off CPB, and at skin closure. Vm was significantly lower in the high Hct group compared with that in the low Hct group during cooling (P < 0.01). Postinduction, the high Hct group demonstrated significantly lower Vd immediately off CPB (P < 0.01) and significantly lower Vm and V(s) at skin closure (P < 0.001). We conclude that there is an inverse relation between hematocrit and cerebral blood flow velocity during deep hypothermic cardiopulmonary bypass in neonates and infants. IMPLICATIONS: There is an inverse relation between hematocrit and cerebral blood flow velocity during deep hypothermic cardiopulmonary bypass in neonates and infants. Further studies correlating Hct and cerebral blood flow velocity with cerebral metabolic rate and neurologic outcome are necessary to determine the optimal Hct during deep hypothermic cardiopulmonary bypass.

Ventricular thrombus and subarachnoid bleeding during support with ventricular assist devices.

We report the case of a 23-year-old man with acute aortic valve insufficiency caused by endocarditis, who after emergency aortic valve replacement developed biventricular heart failure. The heart failure was treated with temporary assist devices. Subarachnoid bleeding and thrombus obstruction of the left ventricular outflow tract was detected. The postoperative course is presented with special emphasis on management of subarachnoid bleeding and the simultaneous use of anticoagulation necessary for ventricular assist devices.

Lung volume reduction surgery: preoperative functional predictors for postoperative outcome.

UNLABELLED: Approximately 20% of patients undergoing lung volume reduction surgery (LVRS) exhibit no functional improvement postoperatively. Therefore, we examined whether variables characterizing ventilatory mechanics before LVRS could serve as predictors for outcome. In 32 patients undergoing LVRS, lung function, dyspnea score, and ventilatory mechanics were assessed preoperatively and 3 mo after LVRS. Ventilatory mechanics were characterized by total resistive work of breathing (WOB), mean airway resistance (Rawm), and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn). Calculations of WOB, Rawm, and PEEPi,dyn were made from measurements of airflow, volume, and esophageal pressure. Preoperative PEEPi,dyn correlated well with the increase in forced expiratory volume percent predicted (r = 0.75; P < 0.0001) and the decrease in dyspnea score (r = -0.74; P < 0.0001) after LVRS. Rawm and WOB showed inferior correlation compared with PEEPi,dyn. The examination of distinct threshold values for WOB, Rawm, and PEEPi,dyn with respect to predicting improvement resulted in a sensitivity of 93% and specificity of 88% for a cutoff point of preoperative PEEPi,dyn > or =5 cm H2O. Preoperative PEEPi,dyn correlated well with improvement in forced expiratory volume and dyspnea score after LVRS. Thus, preoperative assessment of PEEPi,dyn could improve risk to benefit stratification before LVRS. IMPLICATIONS: We examined the preoperative ventilatory mechanics of patients with emphysema undergoing lung volume reduction surgery with respect to their value in predicting outcome. Preoperative intrinsic positive end-expiratory pressure correlated well with the increase in forced expiratory volume in 1 s after surgery. Thus, this variable seems promising for improved patient selection.

Ventilatory mechanics and gas exchange during exercise before and after lung volume reduction surgery.

Many patients with emphysema are able to meet ventilatory demands during resting conditions, but they show severe limitations during exercise. To examine the effect of lung volume reduction (LVR) surgery on exercise performance and the mechanism of possible improvement, we measured ventilatory mechanics (pulmonary resistance [RL], work of breathing [WOB], dynamic intrinsic positive end-expiratory pressure [PEEPi,dyn], peak expiratory flow rate [PEFR]), breathing pattern, oxygen uptake (V O2), and carbon dioxide removal (V CO2) at rest and during cycle ergometry in eight patients before and 3 mo after LVR surgery. Ventilatory mechanics were evaluated assessing esophageal pressure and air flow. Three months after LVR surgery, the tolerated workload was doubled when compared with the preoperative value (p < 0.0005), associated with a reduction of RL (p < 0.05), PEEPi,dyn (p < 0.005), and WOB (p < 0. 005) at comparable workloads. Maximal ventilatory capacity and maximal tidal volume (VT) increased significantly (p < 0.01). Maximal V O2 increased from 474 +/- 23 to 601 +/- 16 ml/min (p < 0. 005) and maximal V CO2 from 401 +/- 13 to 558 +/- 21 ml/min (p < 0. 005), though no significant difference at comparable workloads could be observed. In conclusion, emphysema surgery leads to an improvement of ventilatory mechanics at rest and during exercise. Higher maximal VT and minute ventilation were observed, resulting in improvement of maximal V O2 and V CO2 and exercise capacity.