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Biomedical subjects

V Hessemer

Publications and source records attributed to V Hessemer.

53 records · Page 3Linked to original sources
PubMed1990

[Modification of hemodynamic retrobulbar anesthesia effects by different oculopression procedures (with and without orbital compression)].

For studying the influence of orbital compression--an essential component of the clinically used methods of oculopression--on the hemodynamic effects of retrobulbar anesthesia, two series of investigations were performed preoperatively in 40 patients. In series 1, we initially performed retrobulbar anesthesia (RBA) with 5 ml of a bupivacaine/lidocaine mixture with adrenaline. RBA was followed by a 15-min period of suction-cup oculopression (SCO; negative pressure -100 and -150 mmHg in 10 patients each), which represents an experimental "pure" oculopression without compression of orbital tissue. In series 2, RBA was followed by a 15-min period of Vörösmarthy oculopression (VMO; pressure 30 and 40 mmHg in 10 patients each) which produces both ocular and orbital compression. Before and again after both RBA and oculopression, we determined the intraocular pressure (pio), the systolic retinal and ciliary perfusion pressures or blood pressures, respectively, and the ocular pulsation volume (PVoc) using oculo-oscillo-dynamography. After injection, pio was increased by an average of 4.5 mmHg, the ocular perfusion and blood pressures were lowered by 8.5 and 4.2 mmHg, respectively, and PVoc was reduced by an average of 0.47 microliters (51%) in both series 1 and 2. These effects of RBA may be interpreted as a depressing influence on ocular circulation. After SCO, pio was lowered by an average of 8.5 mmHg, and the ocular blood pressures remained unchanged at the post-injection levels. The perfusion pressures, however, were increased to their initial values, and even beyond in some cases. Thus, the inhibitory effects of RBA on ocular circulation are partially set off by the effects of SCO.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Bilateral dacryocystography using digital subtraction technic for kinetic evaluation of the lacrimal passage].

For dacryocystography we used the following procedure: after bilateral intubation of either the inferior or superior canaliculi with two galactography tubes connected with an Y-adapter, aqueous contrast medium (Ultravist 370) was injected. The lacrimal pathways were then imaged with the digital subtraction technique (Siemens Polytron), as well as with conventional film. In cases of postsaccal stenosis, the relative delay of contrast medium passage--compared with the normal side--could be specified. A diverticulum of the canaliculus and a transitional cell carcinoma of the lacrimal sac could be demonstrated with both techniques. For the purpose of the post-operative follow-up after dacryocystorhinostomy, bilateral digital dacryocystography is particularly helpful because of the good documentation provided on pathway kinetics. However, digital subtraction dacryocystography cannot fully replace conventional dacryocystography.

Adult↗
PubMed1989

Tono-Pen, a new tonometer.

UNLABELLED: The Tono-Pen is a miniaturized Mackay-Marg tonometer with electronic signal analysis and digital pressure display. In study 1, we compared the Tono-Pen with Goldmann tonometry in 108 healthy human subjects (216 eyes). In 33 of these subjects, the IOP was changed in a range between 0 and 50 mmHg by a scleral suction-cup system. In study 2, the Tono-Pen was compared with a Statham membrane manometer in 6 humans (12 eyes), 3-6h after death. The IOP was changed in a range between 0 and 60 mmHg by an infusion system. - RESULTS: Related to the Goldmann tonometer, the Tono-Pen gave a small overestimation of IOP below 16 mmHg (maximum deviation 1.5 mmHg at 0 mmHg Goldmann reading). Above 16 mmHg, however, the Tono-Pen increasingly underestimated the IOP determined by Goldmann tonometry (maximum deviation 8 mmHg at 50 mmHg Goldmann reading). Related to the manometer, the Tono-Pen gave a small overestimation of IOP below 17 mmHg and small underestimation above 17 mmHg (maximum deviation 2.5 mmHg at manometer readings of 0 and 60 mmHg, respectively). - CONCLUSIONS: Throughout the entire clinically relevant IOP range, an acceptable relationship between Tono-Pen and manometer readings was found in human cadaver eyes, whereas the relationship between Tono-Pen and Goldmann tonometric readings in the clinical study was found to be acceptable only in the low and physiological IOP range. The considerable deviation from the Goldmann readings in the high IOP range requires further modifications of the Tono-Pen.

Adolescent↗
PubMed1989

[Preoperative use of suction cup oculopression in comparison with Vörösmarthy oculopression].

In contrast to Vörösmarthy oculopression (VOP), suction-cup oculopression (SOP) is "pure" oculopression without compression of orbital tissue. Prior to 44 cataract operations with posterior chamber lens implantation, the authors performed SOP (negative pressure - 110 mm Hg) or VOP (level of oculopression 30 mm Hg) of the same duration (average 26 min). Before oculopression, a retrobulbar injection (RBI) was performed for local anesthesia. The intraocular pressure (IOP) was decreased by 14 mm Hg to 3.9 and 4.9 mm Hg after SOP and VOP, respectively. After VOP, the iris-vitreous diaphragm was more frequently judged to be concave, i.e., vaulted against the retina, than after SOP (standardized questionnaire). After RBI + SOP, a post-injection of anesthetic was necessary in three cases; no additional injection was required after RBI + VOP. In conclusion, identical preoperative reductions in IOP can be achieved with SOP and VOP. Regarding the form of the iris-vitreous diaphragm and the frequency of post-injection, the differences between the two methods may be related to the lack of orbital compression during SOP.

Aged↗
PubMed1989

[Tono-pen versus manometer. Comparative measurements of intraocular pressure in human cadaver eyes].

A new hand-held tonometer, the Tono-Pen (TP), was compared with a Statham membrane manometer (MAN). The TP is a pen-sized Mackay-Marg tonometer with electronic signal analysis and digital pressure display. Comparative measurements of intra-ocular pressure (IOP) were performed on six cadavers (12 eyes in situ), 3-6 hours after death. The IOP was changed in 5 to 10 mm Hg steps in a range between 0 and 60 mm Hg by an infusion system. As compared to the manometrically determined IOP, the TP gave small overestimation of IOP below 17 mm Hg and a small underestimation above 17 mm Hg (maximum deviation 2.5 mm Hg). The mean values of 29.9 (TP) and 30.4 mm Hg (MAN) were not significantly different (p greater than 0.05, analysis of variance). The correlation coefficient was 0.99. The relationship between TP (y axis) and MAN (x axis) pressure readings is characterized exactly by a slightly curvilinear graph (y = 0.82x + 0.0002x2 + 2.52; mm Hg). This may be approximated by a regression line with a slope of 0.94, a y intercept of 1.46 mm Hg and a standard deviation of the TP readings in relation to the regression line of 2.36 mm Hg. In conclusion, the good agreement between TP and MAN pressure readings is superior to the recently described agreement between TP and Goldmann tonometer readings.

Electronics↗
PubMed1989

[Detection of cystoid macular edema with orally administered fluorescein].

To detect cystoid macular edema after extracapsular cataract extraction, the authors used indirect ophthalmoscopy after oral application of fluorescein, rather than intravenous fluorescein angiography. The patients drank 10-20 ml 10% fluorescein sodium in 250 ml orange juice. Ophthalmoscopy was performed 30-45 minutes later using an exciter filter. Twenty-five patients with a tentative clinical diagnosis of cystoid macular edema were examined in this way. In six of them a manifest edema was detected. The results were confirmed by intravenous fluorescein angiography.

Administration, Oral↗
PubMed1989

[Changes in uveal and retinal hemodynamics caused by retrobulbar anesthesia using various injection volumes].

In 20 patients, retrobulbar injections of 2 or 5 ml local anesthetic (bupivacaine-lidocaine mixture with hyaluronidase) were given preoperatively. Directly after the 5-ml injection, the systolic retinal and ciliary perfusion pressures (measured by means of oculo-oscillo-dynamography according to Ulrich) were reduced by an average of 5.6 mmHg (p less than 0.001) in comparison with the untreated fellow eyes. The ocular pulsation volume (PVoc) was reduced by 39%. Fifteen minutes after the 5-ml injection, the perfusion pressures and PVoc were reduced even slightly more. The intraocular pressure (Pio) was increased by an average of 3.2 mmHg directly after the 5-ml injection, whereas after 15 min the Pio had reassumed its preinjection level. After the 2-ml injection, the PVoc was reduced by the same amount as found after the 5-ml injection. However, there was no significant change in perfusion pressures or Pio after the 2-ml injection. The findings observed during retrobulbar anesthesia may be interpreted as an inhibitory effect on ocular hemodynamics, which increases at higher injection volumes. This effect cannot be accounted for by adrenaline--which was not employed--and can at best only partially be accounted for by the changes in Pio.

Aged↗
PubMed1989

[Intraocular pressure and ocular hemodynamics following oculopression with and without added retrobulbar anesthesia].

Two series of experiments were performed prior to cataract surgery. In series 1, in 30 patients oculopression was performed for 15 min (30, 40 or 50 mmHg). Directly after oculopression the intraocular pressure (Pio) was found to be reduced by an average of 10.7 mmHg. Systolic retinal and ciliary perfusion pressures (measured by means of oculo-oscillodynamography according to Ulrich) were found to be increased by an average of 5.4 mmHg, and the ocular pulsation volume (PVoc) was unchanged. In series 2, we injected 5 ml of anesthetic plus adrenaline behind the eye in 20 patients, followed by 15 min of oculopression (30 or 40 mmHg). Directly after the injection, Pio was found to have increased by 3.7 mmHg, and the perfusion pressures and PVoc were reduced by an average of 8 mmHg and 51%, respectively. Directly after oculopression (15 min after injection), Pio was lower by 10.1 mmHg, but the perfusion pressures and PVoc also remained lower. The changes observed in series 1 and 2 did not depend on the amount of oculopression. We conclude that a reduction in Pio after oculopression has a beneficial effect on the ocular circulation (increased perfusion pressures), whereas retrobulbar anesthesia has an inhibitory effect (reduction of perfusion pressures and PVoc). The hemodynamic effects of oculopression are largely suppressed by additional retrobulbar anesthesia.

Aged↗
PubMed1989

[Postoperative cataract following intraocular lenses with and without laser ridge].

In this randomized, prospective clinical study, a convex plane intraocular lens (IOL) with a laser ridge was compared with a convex plane IOL without a laser ridge. No difference was found in the reduction of capsular opacification 1 year after surgery. The 100 patients (40 males/60 females) with senescent cataracts were treated with ECCE by a single surgeon from November 1986 to March 1987. The operative technique consisted of capsulorhexis, irrigation-aspiration and in-the-bag-implantation. The first group of 50 patients (50 eyes) had an IOL without a laser ridge and the second group an IOL with a laser ridge. When considering after-cataracts in combination with minor visual deterioration we had secondary cataract rate of 15% in the IOL group with a laser ridge and of 16% in the IOL group without a laser ridge. When we considered only the cases in which visual acuity worsened and YAG laser capsulotomy was required, the secondary cataract rate was 1.5%.

Aged↗
PubMed1988

Comparison of intraocular pressure measurements with the Oculab Tono-Pen vs manometry in humans shortly after death.

We compared the Oculab Tono-Pen, a miniaturized Mackay-Marg tonometer, with a Statham membrane manometer in six humans (12 eyes), three to six hours after death. The intraocular pressure was changed in 5- to 10-mm Hg steps in a range between 0 and 60 mm Hg by an infusion system. The correlation coefficient of the relation of Tono-Pen readings vs manometrically determined intraocular pressures was .99. Compared to the manometer, the Tono-Pen gave a small underestimation of intraocular pressure above 17 mm Hg or overestimation below 17 mm Hg. The maximal deviation of the Tono-Pen readings from the manometer readings was 2.5 mm Hg. In our experience the correspondence between Tono-Pen and manometer readings was superior to the correspondence between the readings obtained with the original Mackay-Marg tonometer and manometry.

Aged↗
PubMed1988

[Tono-pen, a new position-independent tonometer. Comparison with the Goldmann tonometer by applanation measurement].

A new hand-held tonometer, Tono-Pen (TP), was compared with the Goldmann tonometer (GM). The TP utilizes the operating principle of the Mackay-Marg tonometer. However, the TP is battery-operated, only 18 cm long, weighs only 60 g, and features electronic signal analysis (single-chip microprocessor) and a digital pressure display (mm Hg). In 108 subjects (216 eyes) presenting no ocular abnormalities, comparative tonometric measurements were performed in randomized order by two investigators (A: TP; B: GM). In 33 of these subjects (66 eyes), the intraocular pressure (IOP) was changed by means of a scleral suction-cup system. A total of 457 pairs of values was obtained in an IOP range extending continuously from 0 to 50 mm Hg. The relationship between TP (y axis) and GM (x axis) pressure readings is described exactly by a slightly curvilinear graph (y = 0.96x - 0.003x2 + 1.48; mm Hg). This may be approximated by a regression line with a slope of 0.8, a y intercept of 2.76 mm Hg and a standard deviation of 2.5 mm Hg (y values) in relation to the regression line. The mean values were 17.6 (TP) and 18.6 mm Hg (GM), which were not significantly different (P less than 0.05). The correlation coefficient amounted to 0.97. Below an IOP (GM) of 16 mm Hg, the TP slightly overestimated the IOP by a maximum of 1.48 mm Hg at GM = 0). Above 16 mm Hg, the TP increasingly underestimated, the IOP by a maximum of 8 mm Hg at GM = 50). Summing up, the TP is unique among hand-held tonometers in its miniaturization. In the low and physiological pressure range, there is an acceptable relationship between TP and GM readings. In the high pressure range, however, its readings deviate considerably from those of the tonometer.

Adult↗
PubMed1986

Effects of passive heat adaptation and moderate sweatless conditioning on responses to cold and heat.

Two series of experiments were performed in physically untrained subjects. In series A (heat adaptation, HA), seven male subjects were adapted to dry heat (five consecutive days at 55 degrees C ambient air temperature (Ta) for 1 h X day-1) under resting conditions. Before and after HA, the subjects' shivering responses were determined in a cold test (Ta + 10 to 0 degrees C). In series B, eight male subjects underwent mild exercise training (five consecutive days at a heart rate, HR, of 120 b X min-1) under Ta conditions individually adjusted (Ta + 15 to +5 degrees C) to prevent both sweating and cold sensations. Before and after "sweatless training", the subjects were subjected to a combined cold and heat test. During HA the thresholds for shivering, cutaneous vasodilatation (thumb and forearm) and sweating were shifted significantly (p less than 0.05) towards lower mean body temperatures (Tb). The mean decrease in threshold Tb was 0.36 degrees C. "Sweatless training" resulted in a mean increase in work rate (at HR 120 b X min-1) and oxygen pulse of 13 and 8%, respectively. However, "sweatless training" did not change the threshold Tb for shivering or sweating. Neither HA nor "sweatless training" changed the slopes of the relationships of shivering and sweating to Tb. It is concluded that the previously reported lowering of shivering and sweating threshold Tb in long-distance runners is not due to an increased fitness level, but is essentially identical with HA. The decreased shivering threshold following HA is interpreted as "cross adaptation" produced by the stressors cold and heat.

Adaptation, Physiological↗
PubMed1985

Influence of menstrual cycle on shivering, skin blood flow, and sweating responses measured at night.

In 10 women, external cold and heat exposures were performed both in the middle of luteal phase (L) and in the early follicular phase (F) of the menstrual cycle. Serum progesterone concentrations in L and F averaged 46.0 and 0.9 nmol X l-1, respectively. The experiments took place between 3:00 and 4:30 A.M., when the L-F core temperature difference is maximal. At neutral ambient temperature, esophageal (Tes), tympanic (Tty), rectal (Tre), and mean skin (Tsk) temperatures averaged 0.59 degrees C higher in L than in F. The thresholds for shivering, chest sweating, and cutaneous vasodilation (heat clearance technique) at the thumb and forearm were increased in L by an average of 0.47 degrees C, related to mean body temperature [Tb(es) = 0.87Tes + 0.13 Tsk] and to Tes, Tty, Tre, or Tsk. The above-threshold chest sweat rate and cutaneous heat clearances at the thumb and forearm were also enhanced in L, when related to Tb(es) or time. The metabolic rate, arm blood flow, and heart rate at thermoneutral conditions were increased in L by 5.0%, 1.1 ml X 100 ml-1 X min-1, and 4.6 beats X min-1, respectively. The concomitant increase in threshold temperatures for all autonomic thermoregulatory responses in L supports the concept of a resetting of the set point underlying the basal body temperature elevation in L. The effects of the increased threshold temperatures are counteracted by enhanced heat loss responses.

Analysis of Variance↗
PubMed1985

Influence of menstrual cycle on thermoregulatory, metabolic, and heart rate responses to exercise at night.

Ten women [mean maximal O2 uptake (VO2max), 2.81 l X min-1] exercised for 15 min on a cycle ergometer in the middle of the luteal phase (L) and in the early follicular phase (F) of the menstrual cycle at the same constant work rates (mean 122 W) and an ambient temperature of 18 degrees C. Serum progesterone averaged 44.7 nmol X l-1 in L and 0.7 nmol X l-1 in F. After a 4-h resting period, exercise was performed between 3 and 4 A.M., when the L-F core temperature difference is maximal. Preexercise esophageal (Tes), tympanic (Tty), and rectal (Tre) temperatures averaged 0.6 degrees C higher in L. During exercise Tes, Tty, and Tre averaged 0.5 degrees C higher. The thresholds for chest sweating and cutaneous vasodilation (heat clearance technique) at the thumb and forearm were elevated in L by an average of 0.47 degrees C, related to mean body temperature (Tb(es) = 0.87Tes + 0.13Tskin), Tes, Tty, or Tre. The above-threshold chest sweat rate and cutaneous heat clearances were also increased in L. The mean exercise heart rate was 170.0 beats X min-1 in L and 163.8 beats X min-1 in F. The mean exercise VO2 in L (2.21 l X min-1) was 5.2% higher than in F (2.10 l X min-1), the metabolic rate was increased in L by 5.6%, but the net efficiency was 5.3% lower. No significant L-F differences in the respiratory exchange ratio and postexercise plasma lactate were demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Basal Metabolism↗
PubMed1984

Effect of slightly lowered body temperatures on endurance performance in humans.

Eight well-trained male rowers exercised as hard as possible on a bicycle ergometer for 60 min at an ambient temperature of 18 degrees C. On 1 day (precooling test, PRET) exercise was preceded by a double cold exposure that caused starting body temperatures to be approximately 4.5, 1.0, 0.8, and 0.4 degrees C (mean skin, mean body, tympanic, and esophageal temperatures, respectively) lower than in the control test (CONT). In PRET the mean 1-h work rate (172 W) was 6.8% larger than in CONT (161 W), O2 uptake (Vo2) was 9.6% higher (2.86 vs. 2.61 1 X min-1), and O2 pulse was increased by 5.6% (18.8 vs. 17.8 ml), whereas the sweat rate was 20.3% lower in PRET (1.06 vs. 1.33 mg X cm-2.min-1). No differences in heart rate, efficiency, postexercise blood values of lactate, or acid-base status were demonstrated. It appears that the improved performance in PRET was related to an increased O2 supply to the working muscles. Although plasma levels of total beta H-endorphin immunoreactivity were in the same range under both test conditions, different components of beta H-endorphin immunoreactivity were indicated to exist in PRET and CONT.

Adolescent↗
PubMedDate not supplied

[Viscoelastic substances in cataract surgery. Principles and current overview].

The major aim for the application of viscoelastic substances in cataract surgery is prevention of corneal endothelial cell loss. This aim is fulfilled by deepening of the anterior chamber, mechanical endothelium protection against surgical trauma, absorption of ultrasound energy, and coating of intraocular lens. The first and mostly used viscoelastic in ophthalmic surgery is a 1% solution of sodium hyaluronate (NaHA) with a molecular weight of 4 million daltons, and a viscosity of 229,000 cP (Healon). For this substance, a good endothelium-protecting function in cataract surgery, especially phacoemulsification, is documented in the literature. In the meantime, further NaHA solutions of different concentrations and viscosities, and a mixture of chondroitin sulfate and NaHA are being offered, as well as low-viscosity solutions of hydroxypropylmethylcellulose (HPMC). The different rheological properties (viscoelasticity, viscosity, and pseudoplasticity) of the substances, the pertinent differences in surgical behavior (injectability, ease of aspiration and manipulation), and the viscoelastic side-effects (mainly IOP increase) are described.

Cataract Extraction↗