Increased intrathoracic pressure affects cerebral oxygenation following cardiac surgery.

BACKGROUND: Cerebral oximetry reflects circulatory stability during surgery. We evaluated whether frontal lobe oxygenation is influenced by a transient increase in intrathoracic pressure as induced by a lung recruitment manoeuvre. METHODS: Intrathoracic pressure was increased to 40 cm H(2)O for 20 s immediately after cardiac surgery in ten patients (age 64 ± 10 year, mean ± SD) with frontal lobe oxygenation assessed by near-infrared spectroscopy and cardiac output by thermodilution. RESULTS: The lung recruitment manoeuvre increased arterial O(2) pressure (from 29 ± 15 to 40 ± 12 kPa) with a decrease in mean arterial pressure (MAP) (from 69 ± 7 to 55 ± 11 mmHg), cardiac output (from 5·4 ± 0·6 to 5·0 ± 0·7 l min(-1)) and frontal lobe oxygenation (from 68 ± 9 to 60 ± 13%; all P<0·05). A reduction in MAP by more than 15 mmHg caused cerebral desaturation by 10%, the lowest cerebral oxygenation (44%) was with a reduction in MAP by 24 mmHg, and according to multiple linear regression, only MAP predicted cerebral deoxygenation (P = 0·03). Following the lung recruitment manoeuvre, hemodynamic variables and frontal lobe oxygenation were restored. CONCLUSIONS: A lung recruitment manoeuvre decreases frontal lobe oxygenation when MAP is low suggesting that with increased intrathoracic pressure, arterial pressure should be kept within the limits of cerebral autoregulation.

The effect of thoracic epidural analgesia on the occurrence of late postoperative hypoxemia in patients undergoing elective coronary bypass surgery: a randomized controlled trial.

STUDY OBJECTIVES: To evaluate the effect of perioperative thoracic epidural analgesia followed by postoperative epidural analgesia compared with conventional IV anesthesia on the occurrence of late postoperative hypoxemia in patients undergoing elective coronary bypass graft (CABG) surgery. DESIGN: Randomized controlled trial. SETTING: Cardiac surgery unit at a university hospital. PATIENTS: A total of 50 patients undergoing elective CABG surgery. INTERVENTION: Patients were randomly assigned to receive either conventional IV anesthesia (CON) or general anesthesia combined with thoracic epidural anesthesia followed by postoperative epidural analgesia (TEA) with bupivacaine. Postoperatively, the patients were monitored in the surgical ward with a pulse oximeter for a total of two postoperative nights (the second and third postoperative nights). MEASUREMENTS AND RESULTS: The overall incidence of episodic hypoxemia was 56% (28 of 50 patients) on the second postoperative night and 89% (41 of 46 patients) on the third postoperative night. More than 30 episodes of hypoxemia developed on the second night in 22% of patients (11 of 50 patients), and on the third night in 30% of patients (14 of 46 patients). Despite oxygen therapy, 7% of patients (3 of 46 patients) experienced constant hypoxemia on the third night. In general, hypoxemia seemed to be slightly worse on the third postoperative night compared with the second postoperative night. Significantly more patients in the TEA group (25 of 25 patients) experienced episodic hypoxemia on the third postoperative night compared with the CON group (16 of 21 patients; p < 0.05). Otherwise, there were no significant differences between the two regimens. CONCLUSIONS: Both episodic and constant hypoxemia were common in the late postoperative period in patients on the ward after CABG surgery with no clinically significant intergroup differences. Thus, perioperative epidural anesthesia/analgesia combined with postoperative epidural anesthesia/analgesia was not protective against hypoxemia, and therapy with opioids did not seem to be of importance for the occurrence of late postoperative hypoxemia on nights 2 and 3 after CABG surgery.

Lung recruitment maneuver depresses central hemodynamics in patients following cardiac surgery.

OBJECTIVE: To assess the impact of the lung recruitment maneuver on circulation following cardiac surgery. DESIGN AND SETTING: Prospective randomized cross-over study at the Departments of Anesthesia and Thoracic Surgery, Copenhagen University Hospital. PATIENTS: Ten adult undergoing coronary artery bypass surgery. INTERVENTIONS: Patients were randomized to two durations of lung recruitment maneuvers (40 cmH2O airway pressure for 10 s and 20 s or vice versa after 5 min) administered immediately after surgery. MEASUREMENTS AND RESULTS: Transesophageal echocardiography (left ventricular short axis view), pulse contour cardiac output, and arterial blood pressure were monitored continuously. Systemic and pulmonary arterial blood gases were sampled before and after each lung recruitment maneuver to calculate the intrapulmonary shunt. Left ventricular end-diastolic areas decreased significantly during both the 10-s and the 20-s lung recruitment maneuvers. Cardiac output was 5.6+/-0.8 l/min at baseline, decreasing by 3.0+/-1.1 l/min and 3.6+/-1.2 l/min during lung recruitment maneuvers of 10 and 20 s, respectively. Shunt decreased from 20+/-5% to 15+/-6% after the first lung recruitment maneuver and from 15+/-6% to 12+/-5% after the second. CONCLUSIONS: Lung recruitment maneuvers markedly reduced cardiac output and left ventricular end-diastolic areas in hemodynamically stable patients following cardiac surgery.

Effects of high thoracic epidural analgesia on myocardial blood flow in patients with ischemic heart disease.

BACKGROUND: In patients with ischemic heart disease, high thoracic epidural analgesia (TEA) has been proposed to improve abnormalities of coronary function by inhibiting cardiac sympathetic tone. We evaluated the effect of TEA on myocardial blood flow in patients with ischemic heart disease. METHODS AND RESULTS: Twenty male patients with multivessel ischemic heart disease were studied. An epidural catheter was inserted between the second and third thoracic vertebral interspace (Th2 to Th3). Analgesia was induced by epidural injection of bupivacaine 0.5%, and a sensory block from the sixth cervical (C6 to C7) to Th10 (Th8 to Th11) vertebral interspace was achieved. Myocardial blood flow was measured with dynamic 13N-ammonia PET with and without TEA at rest, during pharmacological vasodilation with dipyridamole, and during sympathetic stimulation with the cold pressor test. Myocardial blood flow during dipyridamole increased similarly, regardless of TEA, in all regions except in myocardium subtended by collateral arteries in which blood flow increased more with than without TEA (P<0.05). Without TEA, myocardial blood flow during the cold pressor test remained unchanged compared with myocardial blood flow at rest. In contrast, with TEA, myocardial blood flow increased in all vascular territories. Coronary vascular resistance increased during the cold pressor test without TEA, whereas with TEA, coronary resistance decreased in myocardium subtended by nonstenotic and stenotic coronary vessels and remained unchanged in myocardium subtended by occluded vessels. CONCLUSIONS: In patients with multivessel ischemic heart disease, TEA partly normalizes the myocardial blood flow response to sympathetic stimulation.

Effects of amiodarone and thoracic epidural analgesia on atrial fibrillation after coronary artery bypass grafting.

OBJECTIVE: This study was designed to assess the effects of a perioperative dosing regimen of amiodarone administration, high thoracic epidural anesthesia (TEA), or a combination of the 2 regimens on atrial fibrillation (AF) after coronary artery bypass grafting (CABG). DESIGN AND SETTING: The study was prospective, controlled, and randomized and was performed in a tertiary health care center associated with a university. PARTICIPANTS: One hundred sixty-three patients scheduled for coronary artery bypass graft surgery. INTERVENTIONS: In this 2 x 2 factorial-designed study the patients were randomized to 1 of 4 regimens in which group E had perioperative TEA, group E+A had TEA and amiodarone, group A had amiodarone, and group C served as control. The epidural catheter was inserted at T1-3 the day before surgery. TEA groups received TEA for 96 hours. The amiodarone regimen consisted of a single loading dose of 1,800 mg of amiodarone orally. Intravenous infusion of amiodarone was started after induction of anesthesia and was administered at 900 mg over 24 hours for the subsequent 3 days. MEASUREMENTS AND MAIN RESULTS: AF was documented using Holter monitoring. In group E 22 of 44 (50%), in group E+A 10 of 35 (28.6%), in group A 10 of 36 (27.8%), and in the control group 20 of 48 (41.7%) patients developed AF (odds ratio amiodarone/nonamiodarone 0.47 [0.24-0.90]; P = 0.02). CONCLUSIONS: The perioperative amiodarone regimen used in this study was effective in reducing the incidence of AF after CABG while TEA was not.