Transcranial Doppler ultrasonography in anaesthesia and intensive care.
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Anesthetics↗
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Results for “Monitoring, Intraoperative”
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Performing perioperative optimization of the high-risk surgical patient.
Perioperative risk of death after general surgery is quoted as overall less than 1%. However, each individual's risk varies widely according to many identified factors with some having a significantly increased risk of a worse outcome. The observation that manipulating and targeting certain physiological parameters in selected patients can influence this risk has been reported in numerous studies. Yet it is still not widely practised to assist the process, despite the availability of various invasive and non-invasive monitors. This may be in part because of a lack of experience with the practicalities of perioperative optimization, and lack of knowledge in applying currently available tools. This article aims to try and address this deficit and increase awareness of how and when to utilize monitoring equipment to achieve optimal results for the patients we treat.
Algorithms↗
Clinical trials of monitoring in anaesthesia, critical care and acute ward care: a review.
During anaesthesia monitoring is used as part of a complex feedback-control system to keep the patient in a safe physiological 'envelope' and so is central to the conduct of a modern anaesthetic. The utility of basic monitoring is universally acknowledged and will never be assessed using randomized controlled trials. However, each time a new monitoring device is introduced, it can be assessed to see if it adds to the safety and effectiveness of anaesthetics. This review highlights some of the studies that have assessed new monitors in anaesthesia, critical care, and other areas of acute care.
Anesthesia↗
Alarms and human behaviour: implications for medical alarms.
Alarms are used in many clinical applications, but they are often less than optimal because the design and implementation of alarms has not always taken the cognitive capacity and processing mechanisms of the user into account. As a result alarms are frequently too loud, irritating, confusing, badly designed, and too numerous, resulting in them often being turned off and hindering, rather than enhancing, task performance. This paper reviews some of the main areas where it is essential to take account of the cognitive system of the user and behavioural processes more generally. Five central areas of concern are discussed: the number of alarms and ways that this might be reduced; false alarm rates and their impact on human responses; the design of alarms and the application of research into auditory cognition on design; intelligent alarm systems; and the proposals for alarm design set out in a recent worldwide medical alarms standard. In each area some background is given and the implications for alarm design and implementation outlined. The conclusion is that there are some indications that alarm design and implementation takes account of relevant research data, but that there is still some way to go before these findings are fully integrated and the situation is improved upon further.
Anesthesiology↗
Continuous cardiac output monitoring by pulse contour during cardiac surgery.
Most pulse contour methods are unreliable under changing haemodynamic conditions, because no corrections are made for pressure-dependent compliance and reflections of pressure waves. The pulse contour method of Wesseling includes such corrections. Four thermodilution measurements equally spread over the ventilatory cycle were used to calibrate and evaluate this pulse contour method. We designed a prototype incorporating a combination of the thermodilution method and pulse contour method and evaluated its potential for monitoring patients undergoing coronary bypass graft operation. Eight to 12 times during the operation, cardiac output was estimated by pulse contour and by thermodilution. The results were compared: the linear regression between the methods was COpc = 0.3 + 0.94. COth, (r = 0.94). The standard deviation for the difference between the methods against the mean of the methods was 10.6%. We concluded that the corrected pulse contour method estimates cardiac output accurately, even when heart rate, blood pressure, and total peripheral resistance change substantially.
Blood Pressure↗
Caudal clonidine prolongs analgesia from caudal S(+)-ketamine in children.
UNLABELLED: We performed a prospective randomized double-blinded study to test preservative-free S(+)-ketamine alone or in combination with clonidine for intra- and postoperative caudal blockade in pediatric surgery over a 24-h period. Fifty-three children (1-72 mo) scheduled for inguinal hernia repair were caudally injected with either S(+)-ketamine 1 mg/kg alone (Group K) or with additional clonidine (Group C1 = 1 microg/kg; Group C2 = 2 microg/kg) during sevoflurane anesthesia via a laryngeal mask. Intraoperative monitoring included heart rate, blood pressure, and pulse oximetry; postoperative monitoring included a pain discomfort scale and a sedation score. No additional analgesic drugs were required during surgery. The mean duration of postoperative analgesia was 13.3 +/- 9.2 h in Group K, 22.7 +/- 3.5 h in Group C1, and 21.8 +/- 5.2 h in Group C2 (P < 0.0001, Group K versus other groups). Groups C1 and C2 received significantly fewer analgesics in the postoperative period than Group K (15% and 18% vs 63%; P < 0.01). The three groups had similar postoperative sedation scores. We conclude that the combination of S(+)-ketamine 1 mg/kg with clonidine 1 or 2 microg/kg for caudal blockade in children provides excellent analgesia without side effects over a 24-h period. IMPLICATIONS: Caudally administered preservative-free S(+)-ketamine combined with 1 or 2 microg/kg clonidine provides excellent perioperative analgesia in children and has minimal side effects.
Analgesia↗
Relationship of regional wall motion abnormalities to hemodynamic indices of myocardial oxygen supply and demand in patients undergoing CABG surgery.
To investigate the hemodynamic correlates of perioperative regional wall motion abnormalities (RWMA), we measured wall motion continuously via transesophageal echocardiography (TEE), and related RWMA to continuously measured hemodynamic indices of myocardial oxygen supply and demand (heart rate [HR] and systemic and pulmonary arterial blood pressures). Fifty patients undergoing coronary artery bypass graft (CABG) surgery were studied throughout the prebypass postbypass, and intensive care unit (ICU) periods. Only 28% of TEE episodes (RWMA suggestive of ischemia) were preceded by acute changes in any hemodynamic parameter. Specifically, 7% of TEE episodes were preceded by increases in HR (20% deviation from control), 14% by increases in systolic blood pressure (SBP), 13% by decreases in diastolic blood pressure (DBP), and 9% by increases in pulmonary artery diastolic pressure (PAD). Twelve per cent of TEE episodes were associated with increases in rate-pressure product (RPP) to greater than 12,000, and 27% were associated with decreases in mean arterial pressure (MAP)/HR to less than 1 at the onset of TEE episodes. Comparison among periods revealed that postbypass TEE episodes were more frequently associated with either increases in demand or decreases in supply than were prebypass episodes (53% vs. 25%, P less than 0.05). ECG ischemic episodes also were infrequently (30%) associated with acute changes in HR, SBP, DBP, or PAD. We conclude that perioperative TEE episodes are infrequently triggered by changes in hemodynamics, suggesting that a primary decrease in myocardial oxygen supply may be an important mechanism for most perioperative RWMA. In addition, neither pulmonary artery catheter pressure measurements nor specialized indices (RPP and MAP/HR) appear to be useful in predicting TEE episodes.
Adult↗
Acute isovolemic anemia does not impair peripheral or central nerve conduction.
BACKGROUND: Previous studies have found subtle slowing of responses in tests of addition and digit-symbol substitution during acute severe isovolemic anemia to a hemoglobin concentration of 5 g/dl in healthy unmedicated humans. In this study, the authors tested the hypothesis that such changes relate to the slowing of afferent neural traffic. METHODS: The median nerve was stimulated at the wrist in seven healthy unmedicated volunteers before and after induction of acute isovolemic anemia to a nadir hemoglobin concentration of 5.1 +/- 0.3 g/dl (mean +/- SD). Times for neural impulses to travel from the stimulus site to the brachial plexus, cervical spinal cord, and cerebral cortex were measured using somatosensory evoked potentials. Tests were repeated during acute anemia with the subject breathing oxygen. As a control for time and intrasubject variation, the testing was repeated on a separate day when anemia was not produced at times equivalent to those on the experimental day. RESULTS: Induced acute severe isovolemic anemia decreased nerve conduction latencies from the wrist to the contralateral cerebral cortex (i.e., to the N20 peak) by 2.3 +/- 1.6% compared with values at a mean hemoglobin concentration of 12.7 g/dl (P < 0.01). These decreased latencies were due solely to an increased peripheral conduction velocity, from the wrist to the brachial plexus (P < 0.05), and were not altered when subjects breathed oxygen (P > 0.05). Conduction velocity from the brachial plexus or cervical spinal cord to the cerebral cortex did not change with acute anemia (P > 0.05). Latencies did not differ on the control day among the times of testing (all P > 0.05), nor did they differ at baseline between the control and experimental days (all P > 0.05). CONCLUSION: Somatosensory evoked potential latencies were not increased by acute severe isovolemic anemia, making it unlikely that the afferent portion of the neural system is responsible for slowing of cognitive responses previously observed during acute anemia. Because severe isovolemic anemia did not increase somatosensory evoked potential latencies, etiologies other than anemia should be sought if latencies are increased during intraoperative monitoring.
Acute Disease↗
Tumescent local anesthesia for the surgical treatment of burns and postburn sequelae in pediatric patients.
BACKGROUND: Tumescent local anesthesia is a technique for regional anesthesia of the skin and the subcutaneous tissue, using infiltration of large volumes of local anesthetic. The advantages of this technique are (1) simplicity, (2) prolonged postoperative analgesia, (3) low incidence of bleeding, and (4) anesthetization of a large area of the body. There are no reports on the use of tumescent local anesthesia in pediatric patients. METHODS: In 30 consecutive pediatric burn patients with American Society of Anesthesiologists physical status class I or II who were 1-120 months old (34 +/- 31.6 months), after induction of anesthesia with nitrous oxide-oxygen-sevoflurane, infiltration with 0.05% (14 ml/kg) or 0.1% (7 ml/kg) lidocaine solution was performed. Anesthesia was maintained with patients spontaneously breathing with 1.5% sevoflurane in nitrous oxide-oxygen (50%). The maximum dose of lidocaine used was 7 mg/kg. Postoperative pain was assessed by using the Children's Hospital of Eastern Ontario Pain Scale (for patients aged up to 5 yr) and by using a visual analog scale (for patients older than 5 yr). A comparison with a historic control group not treated with the tumescent local anesthesia technique was performed. RESULTS: No patients were excluded from the study, and no significant variations in the monitored intraoperative parameters were observed. Five patients had an increase in heart rate and respiratory rate at the beginning of surgery, and of these, two needed a temporary increase in sevoflurane concentration. After the initial incision, no response to painful stimulus was observed. No complications occurred. Six patients required postoperative acetaminophen administration, and 24 patients did not require analgesic treatment. CONCLUSIONS: Tumescent local anesthesia with maximum dose of 7 mg/kg lidocaine seems to be safe and the sole possible effective locoregional anesthesia technique for the surgical treatment of noncontiguous pediatric burns.
Anesthesia, Local↗
Blood flow of the areola and breast skin flaps during reduction mammaplasty as measured by laser Doppler flowmetry.
Blood flow changes during reduction mammaplasty were studied using laser Doppler flowmetry. Twenty-one patients (39 breasts) were entered into the study. Eight patients underwent a modified Skoog mammaplasty, 6 a central glandular pedicle mammaplasty, 2 an inferior pyramidal dermal flap mammaplasty, and 5 a glandular resection with free nipple grafts. Laser Doppler flowmetry was performed preoperatively, immediately postoperatively, 24 hours postoperatively, 48 hours postoperatively, and 2 weeks postoperatively. Laser Doppler flowmetry values (in milliliters per minute per 100 grams) measured at the areola declined by 23% (Skoog), 18% (central pedicle), and 21% (inferior pyramidal), in the immediate postoperative period. Values at 48 hours were 31% below baseline (Skoog), 14% below baseline (central pedicle), and 60% below baseline (inferior pyramidal). Values at 2 weeks postoperatively were 12% below baseline (Skoog), 2% above baseline (central pedicle), and 44% below baseline (inferior pyramidal). The free nipple grafts showed an 89% rise above baseline at 2 weeks. One patient's procedure was changed to a free nipple graft after a 92% Doppler flow reduction during a Skoog mammaplasty. The free nipple graft had the greatest blood flow. The central pedicle mammaplasty showed the least decline in areolar flow. The inferior pyramidal mammaplasty showed the greatest decline. Laser Doppler flowmetry is a clinically useful tool for monitoring intraoperative and postoperative nipple/areolar blood flow.
Adolescent↗
Abdominoplasty with procedural sedation and analgesia.
The ability to perform abdominal cosmetic surgery in the ambulatory setting provides a more comfortable environment for the patient, ease of scheduling for the physician, and decreased costs. Avoiding the use of general anesthesia allows for quicker recovery, shorter length of hospital stay, and decreased rate of postoperative complications. The authors report 106 consecutive abdominoplasties, including fascial plication when indicated, using local anesthesia, with procedural sedation and analgesia. All procedures were performed with an anesthesiologist providing intraoperative monitoring of the patients. Their protocol uses procedural sedation and analgesia, which results in a depressed level of consciousness, but allows the patient to maintain airway control independently and continuously. The results of this approach were measured in terms of procedure time, length of hospital stay, rate of complications, total recovery time, and the level of patient satisfaction. Between January 1996 and January 1999, 106 patients underwent abdominoplasty (performed by one of the authors) under local anesthesia with procedural sedation and analgesia. All patients had an American Society of Anesthesiologists status of 1 to 3, and underwent a full abdominoplasty, including fascial plication. In 26% of the patients, allied procedures were also performed, most commonly liposuction or augmentation mammaplasty. The mean age in this series was 45 years, and all patients were available for follow-up at least 1 year after surgery. The mean operative time was 135 minutes, recovery room time was 68 minutes, and all patients were ambulatory. There were no surgical complications, including flap loss or wound dehiscence, and no complications related to anesthesia (cardiac, deep vein thrombosis, fat emboli, pulmonary embolism, etc.). Because paralytic agents were not used, none of the patients required catheterization postoperatively. Patients were generally pleased with the results of surgery. Although the extent of the surgery remains the same, this approach provided patients with an easier postoperative experience. In summary, abdominoplasty, including full fascial plication of the rectus and external oblique aponeurosis, can be performed safely and comfortably under local anesthesia with procedural sedation and analgesia. Patients are comfortable, recover quickly, and are very satisfied with their surgical result and overall experience.
Abdominal Muscles↗
Anesthetic considerations for thoracic neurosurgical procedures.
Anesthetic considerations for thoracic and thoracoscopic neurosurgical procedures are considered, emphasizing the need to provide anesthetic stability during prolonged periods of one-lung ventilation, while optimizing conditions for intraoperative monitoring of spinal cord integrity.
Journal Article↗
Endoscopic and stereotactic neurosurgery.
PURPOSE OF REVIEW: Review of the anesthetic considerations for neuroendoscopy and stereotactic procedures. RECENT FINDINGS: Minimally invasive procedures are increasingly applied in novel ways in the diagnosis and treatment of neurological pathologies. Endoscopic third ventriculostomy, endoscopic shunt revisions and drainage of intraventricular hematoma using a neuroendoscope have become routine neurosurgical procedures. Stereotaxis has expanded its scope from simple brain biopsy to functional neurosurgery and psychiatry. While these procedures are 'minimally invasive', perioperative critical events may still occur. SUMMARY: Vigilance in preoperative assessment and intraoperative monitoring is essential in minimizing perioperative morbidity and mortality in patients undergoing neuroendoscopic and stereotactic procedures.
Journal Article↗
Prevention of positional brachial plexopathy during surgical correction of scoliosis.
Continuous intraoperative monitoring of spinal cord function using somatosensory evoked potentials (SSEP) has gained nearly universal acceptance as a reliable and sensitive method for detecting and possibly preventing neurologic injury during surgical correction of spinal deformities. In several reports, spinal cord injury was identified successfully based on changes in SSEP response characteristics, specifically amplitude and latency. Less well documented and used, however, is monitoring of peripheral nerve function with SSEPs to identify and prevent the neurologic sequelae of prolonged prone positioning on a spinal frame. The authors describe a patient who underwent surgical removal of spinal instrumentation but was not monitored. A brachial plexopathy developed in this patient from pressure on the axilla exerted by a Relton-Hall positioning frame during spinal surgery. In addition, data are presented from 15 of 500 consecutive pediatric patients who underwent surgical correction of scoliosis between 1993 and 1997 with whom intermittent monitoring of ulnar nerve SSEPs was used successfully to identify impending brachial plexopathy, a complication of prone positioning. A statistically significant reduction in ulnar nerve SSEP amplitude was observed in 18 limbs of the 500 patients (3.6%) reviewed. Repositioning the arm(s) or shoulders resulted in nearly immediate improvement of SSEP amplitude, and all awoke without signs of brachial plexopathy. This complication can be avoided by monitoring SSEPs to ulnar nerve stimulation for patients placed in the prone position during spinal surgery.
Adult↗
A neurovascular complication after scapulothoracic arthrodesis.
Facioscapulohumeral muscular dystrophy is a progressive disorder characterized by weakness in the muscles of the face, shoulder girdle and upper limbs, and variable lower extremity weakness. The muscles that stabilize the scapula are significantly weak, although the deltoid usually is preserved. With attempted shoulder abduction, the unstable scapula protrudes, elevates, and internally rotates. Scapulothoracic arthrodesis stabilizes the scapula and improves active range of motion and function of the shoulder. Appropriate scapular positioning on the chest wall has been described previously. The current authors review a neurovascular complication after scapulothoracic arthrodesis in which the scapula was positioned as described in the literature. Immediate repositioning resulted in an excellent long-term outcome. Previous recommendations as to scapular position must be taken simply as guidelines. Intraoperative monitoring of neurovascular function in the upper extremity should prevent this complication.
Adolescent↗
Fluorescence mapping of mitochondrial redox changes in heart and brain.
Fluorescence techniques may be utilized to map changes in the distribution of mitochondrial redox states in heart and brain during ischemic or hypoxic stress. The basis of these techniques is the intrinsic fluorescence of reduced NADH and oxidized flavoprotein in mitochondria which respond to changes in critical oxygen supply. Ischemic areas in rabbit hearts induced by coronary ligation were detected and mapped based on the increase in NADH fluorescence in the ischemic zone. The width of the jeopardized normoxic tissue surrounding the ischemic area (less than 50--350 mu) was measured by combination of fluorescein angiography and NADH fluorescence. Areas of increased NADH fluorescence in gerbil brains after carotid artery ligation or induction of spreading depression were mapped in a similar manner. Intraoperative monitoring of flavoprotein fluorescence from human cerebral cortex after superficial temporal artery middle cerebral artery (STA-MCA) anastomoses demonstrated increased rates of cortical oxidative metabolism after the surgical procedures.
Animals↗
The saphenous system for long-term parenteral nutrition.
Three case reports describing the use of inferior vena caval catheterizations for total parenteral nutrition (TPN) are presented. Five anterior femoral vein cutdowns were advanced through the saphenous bulb, femoral, and iliac veins into the inferior vena cava. Four catheters were used for the purpose of TPN administration, the 5th for blood product administration and intraoperative monitoring. Five catheters were left in place without thrombotic or septic complications for a total of 10 months. The technique of elastomer catheter insertion in the tributary of the greater saphenous vein under local anesthesia is described.
Adult↗
Concurrent right and left ear auditory brain stem response recording.
In auditory brain stem response testing, it is often advantageous to record the responses to right and left ear stimulation quickly. A method is described in which both ears are tested concurrently, each ear at a slightly different stimulus rate. With appropriate temporal parameters, the response of each ear can be recorded without contamination by the contralateral ear's response. When both ears were tested at the same intensity, either 40 or 70 dB nHL, there was little attenuation of wave V. When one ear was stimulated at 80 dB nHL, the response of the other ear at intensities down to 40 dB was not seriously affected; the response at 20 dB nHL was, however, so diminished by contralateral stimulation at 80 dB that binaural testing would save no time. This method has promise for intraoperative monitoring and infant screening, and could be used in threshold determination if the stimulus intensities for the two ears are not too dissimilar.
Acoustic Stimulation↗