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Biomedical subjects

H Ahn

Publications and source records attributed to H Ahn.

At least 73 records · Page 4Linked to original sources
PubMed1988

Effect of epidural anaesthesia on intestinal blood flow.

The effect of epidural bupivacaine (5 mg/ml) on intestinal blood flow was studied with laser Doppler flowmetry in 15 patients during operations including various types of large bowel resection. In the colon, blood flow increased in 13 out of 15 patients, which was significant at the 1 per cent level. The average increase was 41 per cent. In the ileum an increase was found in eight out of eleven patients who could be studied, which was significant at the 5 per cent level. Bowel function was restored satisfactorily in all patients. It is concluded that epidural bupivacaine has a favourable effect on intestinal blood flow during colorectal surgery.

Adult↗
PubMed1988

Effect of continuous postoperative epidural analgesia on intestinal motility.

The effect of postoperative epidural bupivacaine on intestinal motility was studied by measuring the transit time of barium contrast through the intestines in 16 patients after resection of the left colon and/or rectum. Fourteen patients served as controls and received postoperative injections of pentazocine. Mean transit time through the intestinal tract was 35 h in the epidural group and 150 h in the control group, a difference that is significant at the 0.1 per cent level. The average time before passage of flatus and faeces was different between the two groups at the 0.1 per cent level. We conclude that postoperative epidural bupivacaine constitutes an effective means of analgesia after colorectal surgery and is associated with a short duration of intestinal paralysis.

Aged↗
PubMed1988

Assessment of gastric blood flow with laser Doppler flowmetry.

The use of laser Doppler flowmetry (LDF) to measure gastric blood flow was evaluated in the cat and man. The reproducibility of laser Doppler flowmetry recordings was studied in the feline stomach. In five cats flowmeter signals and venous outflow of the stomach were simultaneously recorded. The flowmeter recordings were made during operation and gastroscopy in 140 patients by means of two different (PF1-4-kHz and PF2-12-kHz) laser Doppler systems. The flowmeter recordings were highly reproducible during the cat experiments, with a coefficient of variation varying between 4% and 13%. Angulation of the probe within 60-120 degrees against the tissue under study did not affect the flowmeter signal. Pressure of the probe against the studied tissue attenuated the flowmeter signal 42 +/- 13% (n = 10). A significant correlation coefficient (r = 0.76; p = 0.01; n = 30) was obtained between flowmeter signal and venous outflow of the stomach. In man the PF2-12-kHz system yielded a higher flowmeter signal (14.5 +/- 6.9 V; 32 patients) than the PF1-4-kHz system (7.9 +/- 2.5 V; 108 patients). Flow dimensions were calculated by using results previously obtained in the intestines. The estimated blood flow values amounted to 31 +/- 10 and 57 +/- 27 ml min-1 100 g-1 for the PF1-4-kHz and PF2-12-kHz systems, respectively. In conclusion, laser Doppler flowmeter is a promising technique for studying gastric perfusion during operation and endoscopy. Motion artifacts are the major drawback of the present laser Doppler systems.

Adult↗
PubMed1988

Complications of intra-aortic balloon counterpulsation, with special reference to limb ischemia.

During a 5-year period, intra-aortic balloon pumping (IABP) was performed on 90 patients (3.1% of those undergoing open-heart surgery), using a Percor catheter inserted with Seldinger technique. Overall prognosis was poor; only 46 of the 90 patients were alive at postoperative follow-up averaging 23 months. Limb ischemia arose in 20%, with incidence uninfluenced by catheter insertion technique (percutaneous v. 'open'). Surgical treatment was required for half of the ischemic limbs. Groin hematoma commonly followed percutaneous extraction of IABP catheter, whereas 'open' removal was always hemostatic, with potential for embolectomy. Percutaneous insertion of IABP catheter via the femoral artery is the method of choice in an emergency situation. 'Open' Seldinger technique is preferable in the operating room. For elective IABP catheter removal, the 'open', hemostatic technique is recommended. If limb-threatening ischemia develops, the catheter must be removed. If the patient is IABP-dependent, the contralateral femoral artery or the ascending aorta should be considered as an alternative catheter route.

Female↗
PubMed1988

Assessment of gastrointestinal blood flow with laser Doppler flowmetry in patients with chronic radiation injury.

Laser Doppler flowmetry was used for pre- and intraoperative assessment of gastrointestinal blood flow and vascular damage in eight patients with late radiation injury of the gastrointestinal tract. The flowmeter recordings were compared with reference values previously obtained in unaffected tissue from corresponding gastrointestinal sites. Marked reduction of blood flow was demonstrated in macroscopic areas of radiation injury in all eight patients. Five also showed varying degrees of disturbed blood flow in adjacent macroscopically normal bowel segments with histologically varying severity of radiation injury. In a ninth patient radiation injury was clinically suspected but could not be demonstrated with laser Doppler flowmetry or histologically. The extent of radiation injury often is underestimated from clinical signs, and laser Doppler flowmetry during surgical treatment of late radiation injury to the gastrointestinal tract provides substantial information concerning the extent of vascular damage.

Adult↗
PubMed1987

Tissue penetration and measuring depth of laser Doppler flowmetry in the gastrointestinal application.

Tissue penetration of laser light and measuring depth (depth sensitivity) for laser Doppler flowmetry in the gastrointestinal application were studied in the feline and human bowel and stomach with a wall thickness of from 2.1 to 7.0 mm. Mucosal and serosal recordings from corresponding sites in the gastrointestinal tract were comparable and in the intestine correlated to total blood flow. Laser light was reflected by a mirror placed on the opposite side of the bowel wall, and hyperemic reactions were similarly recorded from both sides of the bowel with wall thickness up to 6 mm. Placing layers of unperfused feline small intestine (average thickness, 2.1 mm) between the probe and the perfused feline gastric wall attenuated the laser Doppler signal in an exponential manner. We conclude that with this instrument, the tissue penetration and measuring depth of laser Doppler flowmetry are at least 6 mm in the gastrointestinal application.

Animals↗
PubMed1986

Local blood flow changes in association with proximal gastric vagotomy.

Local blood flow changes in association with proximal gastric vagotomy were studied with laser Doppler flowmetry in 10 patients. After the vagotomy a significant decrease in blood flow amounting to 57 +/- 21% (range, 18-87%; p less than 0.001) was observed within the dissected area along the lesser curvature. In three patients, the flowmeter recordings suggested localized areas with very poor perfusion. The blood flow was restored to preoperative control values within 3-4 weeks after the operation. It is suggested that the temporary poor blood perfusion along the lesser curvature may be an important factor in the genesis of postoperative ulcerations in the dissected area. We conclude that laser Doppler flowmetry seems to have great potential as a method to study localized blood flow changes in the stomach. Flowmeter recordings can be made both during operation and endoscopy.

Humans↗
PubMed1986

Assessment of small-bowel ischemia by laser Doppler flowmetry. Some case reports.

Laser Doppler flowmetry was used for intraoperative assessment of intestinal blood flow in five patients with small-bowel ischemia. In two patients with mechanically caused ischemia, bowel resection could be limited or avoided after flowmeter recordings. In two patients with mesenteric vascular occlusion, the flowmeter recording confirmed the macroscopic impression of irreversible gangrene. In a third subject with mesenteric vascular occlusion the extent of severe ischemia was clinically underestimated compared with the results obtained with the laser Doppler flowmeter. We conclude that, with further experience and development, laser Doppler flowmetry has great potential as a useful method for objective intraoperative assessment of blood flow in patients with small-bowel ischemia of various origins.

Aged↗
PubMed1986

Assessment of blood flow in the small intestine with laser Doppler flowmetry.

Blood flow in the small intestine was assessed in 48 patients by laser Doppler flowmetry. Mucosal and serosal flowmeter signals were compared during 'resting' conditions, vascular occlusion, and reactive hyperemia. Serosal flowmeter recordings were compared with the total blood flow of a bowel segment as measured by venous collection. The magnitudes of the mucosal (n = 49) and serosal (n = 49) flowmeter signals were comparable throughout the whole range of flowmeter signals (r = 0.97; p less than 0.001). A correlation coefficient of 0.95 (n = 51; p less than 0.001) was obtained between serosal flowmeter signals and total blood flow during 'resting' and reduced blood flows. During vasodilatation after a vascular occlusion, blood flow was underestimated by the flowmeter. A calibration curve could be constructed for approximate interpretation of the flowmeter signals in absolute flow units. The present study underlines the potential of laser Doppler flowmetry in the assessment of blood flow in the human small intestine.

Adolescent↗
PubMed1986

Measurement of colonic blood flow with laser Doppler flowmetry.

Colonic blood flow was measured with laser Doppler flowmetry during operation in 62 patients and during coloscopy in 15 patients. In 18 subjects mucosal and serosal laser Doppler signals were compared during 'resting' conditions, vascular occlusion, and reactive hyperemia. The mucosal (n = 36) and serosal (n = 36) flowmeter signals were of the same order of magnitude throughout the whole range of flowmeter signals (r = 0.96; p less than 0.001). In eight subjects total venous outflow from a colonic segment was measured simultaneously with flowmeter recordings from the serosal side. A correlation coefficient of 0.95 (n = 46; p less than 0.001) was obtained between total intestinal blood flow and serosal flowmeter signal during 'resting' and reduced blood flows. In this flow range a calibration curve was constructed for interpretation of the flowmeter signals in absolute flow units. The wall thickness of the bowel determined the quantitative relationship between flowmeter signal and total intestinal blood flow. It is concluded that laser Doppler flowmetry represents a potentially very interesting non-invasive, continuous method for the quantitative study of human intestinal blood flow.

Adolescent↗
PubMed1986

Pneumocephalus: effects of patient position on the incidence and location of aerocele after posterior fossa and upper cervical cord surgery.

The incidence of pneumocephalus and factors contributing to its occurrence were studied retrospectively in 100 consecutive patients who underwent posterior fossa or cervical cord surgery in the sitting, park-bench, and prone positions. Supine skull x-ray films taken immediately postoperatively were used to determine the presence of intracranial air. Surgery in the sitting position uniformly resulted in pneumocephalus (32/32 patients). Pneumocephalus also occurred frequently among patients in the park-bench (29/40) and prone positions (16/28). Intraventricular air occurred more frequently when patients were in the sitting position (25/32) than in the two other surgical positions (3/29 and 4/16, respectively, P less than 0.001). The high incidence of pneumocephalus and of intraventricular air that occurred when patients were in the sitting position is attributed to the large amount of cerebrospinal fluid drained due to gravitational effect. When surgical position is considered one of the contributing factors, only positions significantly affected the frequencies of pneumocephalus and intraventricular air accumulation. None of the 77 patients with pneumocephalus suffered neurologic change related to the presence of intracranial air. We conclude the following: pneumocephalus commonly occurs after posterior fossa or cervical cord surgeries, particularly when the surgery is performed in the sitting position; neurologic change caused by pneumocephalus is a rare complication after posterior fossa craniotomy; when a patient with coexisting hydrocephalus undergoes surgery, if the patient is in the sitting position, there is an increased risk of trapping a large amount of intracranial air.

Adolescent↗
PubMed1985

Evaluation of laser Doppler flowmetry in the assessment of intestinal blood flow in cat.

Laser Doppler flowmetry with a differential detector system has been used in the assessment of blood flow in the feline small intestine. Simultaneous mucosal and serosal laser Doppler flowmeter recordings were compared with total blood flow of a bowel segment measured by an optical drop-recorder unit in 6 cats. Blood flow through the muscularis layer was estimated using the 85Kr washout technique. A correlation coefficient of r = 0.96 (mucosal recordings = 90, serosal recordings = 80, p less than 0.001) was obtained between laser Doppler flowmeter output signals and total blood flow at different levels of vascular tone, regardless of whether the flowmeter recordings were made from the mucosal or the serosal side of the bowel wall. At intense vasodilation, the flowmeters showed a tendency to underestimate blood flow. The flowmeter signals were at variance with the muscularis blood flow but were clearly correlated to the calculated mucosal-submucosal blood flow. The uneven blood flow distribution in the intestinal wall did not affect the ability of the flowmeters to reflect total blood flow from either side of the bowel wall. A calibration curve could be constructed for approximate interpretation of the laser Doppler signals in absolute flow units. However, further experiments in humans and further development of the technique must be performed to elucidate clinical applications of the method.

Animals↗
PubMed1981

Neurometric evaluation of learning disabled children.

A quantified electrophysiological system called Neurometrics is described in terms of procedures, reliability and validity. The role of the computer in both acquisition and analysis is noted. In terms of the application of Neurometrics to issues of diagnostic validity five studies are discussed. The first describes a study showing that normal functioning and at risk children differ markedly in terms of the percentage showing EEG abnormalities; the second reports the difference between children who are poor achievers in verbal, arithmetic or both skills; the third shows that Neurometric indices differentiate between epileptic children who are achieving or not achieving at grade appropriate levels; the fourth describes Neurometric EEG differences between learning disabled children who do or do not have reading reversal problems; and the fifth describes the behavioral differences constructed on the basis of their Neurometric profiles.

Brain↗
PubMed1980

Developmental equations for the electroencephalogram.

Thirty-two linear regression equations predict the frequency composition of the electroencephalogram within four frequency bands, for four bilateral regions of the brain, as a function of age. Equations based on such data from large groups of healthy children in the United States and Sweden are closely similar. These equations describe the development of the electrical activity of the normal human brain, independent of cultural, ethnic, socioeconomic, or sex factors.

Adolescent↗
PubMed1980

Developmental equations reflect brain dysfunctions.

Developmental equations, which predict 32 parameters of the electroencephalogram recorded from the healthy human as a function of age, were tested in diverse groups of children. Few significant deviations were found in normal children, even in a culture different from the one on which the equations were based. A high incidence of significant deviations was found in children with learning disabilities and those at risk for various neurological disorders.

Adolescent↗
PubMed1980

Neurometric evaluation of epileptic children who do well and poorly in school.

The neurometric examination is a way of obtaining quantitative electrophysiological data which can be analyzed statistically and compared with similar information from control groups. Statistically significant differences were found among 4 groups of children: group I -- 'epileptic achievers', children with a history of seizures who are functioning at grade level, group II -- 'epileptic under-achievers', children with a history of seizures who are not functioning up to grade level, group III -- 'healthy achievers', children without a history of seizures who are functioning at grade level, and group IV --'healthy underachievers', children who do not have a history of seizures and who are not functioning at grade level. 'Epileptic achievers' and 'epileptic underachievers' both showed sharp waves, severe and widespread. However, 'epileptic underachievers' displayed more 'beta bursts', excessive theta and beta activity in the resting EEG, and greater hyper-reactivity of evoked responses to visual and auditory stimuli in the frontal and frontopolar regions. 'Epileptic achievers' and 'healthy achievers' both had little abnormality in the frequency spectrum. However, the 'epileptic achievers' showed more theta activity, more asymmetry and lower coherence. 'Epileptic underachievers' showed a lower incidence of EEG asymmetries than 'healthy underachievers' but more theta and beta activity. 'Healthy underachievers' showed more abnormal spectral bands, more areas with abnormal spectral bands, greater asymmetry, lower coherence, and a higher incidence of sharp waves than 'healthy achievers'. When the 'epileptic achievers' and 'underachievers' were combined, they were found to have a significantly higher incidence of sharp waves, theta and beta excess, EEG asymmetry, low coherence, and hyper-reactive evoked responses than the 'healthy achievers'.

Achievement↗