Anesthesia and analgesia
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Anesthesia and analgesia · Feb 2002
Clinical Trial Controlled Clinical TrialEpidural infusion pressure in degenerative spinal disease before and after epidural steroid therapy.
The analgesic mechanism of epidural steroids in reducing pain associated with degenerative spinal disease (DSD) is poorly understood. We report increased inline epidural infusion pressure in patients with DSD and assess whether this phenomenon is affected by administration of an epidural steroid injection. We collected data during epidural placement for routine surgery or epidural steroid therapy. Using a 17-gauge Tuohy needle, with patients in the right lateral decubitus position, loss of resistance to 2 mL of saline identified the epidural space. Two minutes later the needle was attached to saline-filled tubing connected to a pressure transducer (Baxter PX 260 pressure monitoring kit with Truwave TM disposable pressure transducer). In the first part of the study, 4 successive boluses of 3 mL of local anesthetic were administered at a rate of 6 mL/min to 15 patients (age 47 +/- 6 yrs) with radicular back pain and magnetic resonance imaging (MRI) or computed tomography (CT) evidence of DSD, and to 8 control patients with no history of back pain (age 44 +/- 5 yr) while inline epidural infusion pressure was measured. In the second part of the study 44 patients with low back pain and MRI or CT evidence of DSD presenting to the pain clinic were infused with 8 mL of 0.125% bupivacaine and 40 mg of methylprednisolone (20 mg/mL) at a rate of 6 mL/min while inline epidural infusion pressure was measure and recorded. This was repeated 3 wk later. Initially, DSD patients had significantly increased infusion pressures over normals, which most likely reflects outflow resistance or obstruction. A significant decrease in inline epidural infusion pressure was observed after epidural steroid treatment. This change in pressure may indicate efficacy from epidural steroid injection. ⋯ During injection into the epidural space we observed increased resistance in patients with degenerative spinal disease. This resistance was significantly less when measured 3 wk after an epidural steroid injection. This change in pressure may indicate efficacy from epidural steroid injection.
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Anesthesia and analgesia · Feb 2002
Venous air emboli occur during release of positive end-expiratory pressure and repositioning after sitting position surgery.
We studied the effect of positive end-expiratory pressure (PEEP) release and positioning on the occurrence of venous air embolism (VAE). Eighteen consecutive patients (8 women, 10 men; ASA grade I-III) undergoing neurosurgery in the sitting position were studied. After induction of anesthesia ventilation was controlled with a PEEP of 5 cm H(2)O in an oxygen-air gas mixture. A transesophageal echocardiographic (TEE) probe was inserted. Preoperatively, a patent foramen ovale was excluded in all patients. TEE monitoring was performed during surgery, during PEEP release at the end of surgery with the patient still in the sitting position, and during change of the patient position into the supine position. The severity of VAE was differentiated as follows: grade 1 = only microbubbles; grade 2 = microbubbles and decrease of end-tidal carbon dioxide partial pressure (PETCO(2)) by more than 1.5 mm Hg; grade 3 = microbubbles combined with a decrease of PETCO(2) by more than 1.5 mm Hg, and a decrease of mean arterial blood pressure by at least 20 mm Hg. During surgery, VAE with a grade of 1, 2 or 3 occurred in 7, 4, and 2 patients, respectively. After PEEP release, VAE of grades 1, 2, and 3 were observed in 7, 2, and 1 patients, respectively. During repositioning from sitting to supine position, VAE of grades 1, 2, and 3 was observed in 6, 1, and 1 patients, respectively. The patient with VAE grade 3 needed inotropic support until 2 h after surgery to maintain sufficient blood pressure. No patient showed any sign of paradoxical arterial embolism or cardiac dysfunction. We conclude that VAE occurs not only during surgery in the sitting position, but also with release of PEEP and during repositioning to the supine position. ⋯ This study shows that venous air embolism (VAE) occurs not only during surgery in the sitting position but also during positive end-expiratory pressure release and repositioning of the patient into the supine position. Continuous monitoring for VAE should be performed until the patient is returned to the supine position.
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Anesthesia and analgesia · Feb 2002
Comparative StudyElectrocardiographic electrodes provide the same results as expensive special sensors in the routine monitoring of anesthetic depth.
The Bispectral Index (BIS) is a mathematically derived electroencephalographic (EEG) derivative that has been introduced to monitor depth of anesthesia (1,2). The A-2000 BIS monitoring system (Aspect Medical Systems, Inc., Newton, MA) is currently the only commercially available system to monitor depth of anesthesia. In several studies, its propensity to optimize the use of hypnotics to maintain and achieve a certain depth of anesthesia has been described (3,4). Some studies have even proposed that the routine use of the monitoring system can decrease awareness (1,5), an increasing factor in malpractice claims. The cost-benefit calculations for BIS monitoring suffer from the fact that like its predecessor, the 1000-A BIS monitor, the A-2000 BIS monitoring system demands the use of expensive, special electrodes (6). Although the application of the single-use BIS sensor is very comfortable and easy to use, its high price of approximately $10-20 US prevents many anesthesiologists from using it. Furthermore, whereas the former model of the monitor (1000-A BIS monitor; Aspect Medical Systems, Inc.) used standardized connectors, which allowed the use of other electrodes such as electrocardiogram (ECG), the new monitoring system makes this very difficult because of special connectors that match the equivalent connector at the proximal BIS sensor site. The purpose of this prospective study was to compare BIS values derived from the original BIS sensor with BIS values derived from commercially available ECG electrodes. This comparison was made possible by designing and manufacturing a connector allowing the use of ECG electrodes. ⋯ The Bispectral Index (BIS) monitor adequately monitors depth of anesthesia. The routine use of this monitor has been hampered by the benefit-cost equation because only special expensive electrodes can be used. We examined the agreement of BIS values obtained by original sensor electrodes and commercial electrocardiogram (ECG) electrodes. These ECG electrodes can replace more expensive BIS sensors.
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Anesthesia and analgesia · Feb 2002
Comparative StudyTransesophageal echocardiography interpretation: a comparative analysis between cardiac anesthesiologists and primary echocardiographers.
Diagnostic interpretation of intraoperative transesophageal echocardiography (TEE) examinations may vary, particularly when the echocardiographer is also the anesthesiologist. We therefore evaluated the concordance of TEE interpretation as part of a process of continuous quality improvement (CQI). Ten cardiac anesthesiologists participating in a CQI program conducted 154 comprehensive TEE examinations, each consisting of 16 major fields describing cardiac anatomy and function. These examinations were subsequently interpreted off-line by two primary echocardiographers (a radiologist and a cardiologist). Agreement was assessed using the kappa coefficient and percent agreement. Overall kappa and percent agreement were 0.58 and 83% for anesthesiologists versus radiologist, 0.57 and 80% for anesthesiologists versus cardiologist, and 0.60 and 82% for radiologist versus cardiologist. Anesthesiologists with longer than 5 yr of TEE experience had higher levels of agreement with the radiologist when assessing the aorta, right atrium, pulmonary vein flow, transmitral flow, and fractional area change. Cardiac anesthesiologists supported by a CQI program interpret TEE examinations at a level comparable with physicians whose primary practice is echocardiography. Thus, the anesthesiologist and the intraoperative echocardiographer need not be mutually exclusive. ⋯ Interpretation of intraoperative transesophageal echocardiograms can be reliably performed by cardiac anesthesiologists.
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Anesthesia and analgesia · Feb 2002
Preserved CO(2) reactivity and increase in middle cerebral arterial blood flow velocity during laparoscopic surgery in children.
In adult patients, the creation of pneumoperitoneum (PP) by means of carbon dioxide (CO(2)) insufflation leads to an increase in cerebral blood flow velocity (CBFV), which is thought to be caused by hypercapnia. We evaluated whether PP leads to an increase of CBFV in children, and whether this increase is directly related to PP. The effects of PP on middle cerebral artery blood flow velocity were investigated in 12 children (mean age 3 yr, range 15-63 mo) undergoing laparoscopic herniorrhaphy under general anesthesia with sevoflurane and nitrous oxide/oxygen. CBFV was measured by using transcranial Doppler ultrasonography. During CO(2) insufflation, the end-tidal CO(2) concentration was kept constant by adjustment of ventilation by increasing minute volume. The CBFV increased significantly at an intraabdominal pressure of 12 mm Hg compared with baseline from 68 +/- 11 cm/s to 81 +/- 12 cm/s (P < 0.05). CO(2) reactivity remained in the normal range (4.0% +/- 1.9%/mm Hg) during PP. We conclude that the induction of PP leads to an increase in middle cerebral artery blood flow velocity in young children independent from hypercapnia, whereas CO(2) reactivity remains normal. ⋯ Laparoscopic surgery is performed frequently in pediatric patients. Cerebral blood flow velocities increase during insufflation of the intraperitoneal cavity for minimally invasive surgery in children. The vasoreactivity as part of the cerebral autoregulation remains unaffected.