Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0086543 (cataract)
 29,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Benzodiazepines for sedation may decrease the PaO2, the arterial O2 saturation (SaO2), and the CO2 response more in the elderly than in the young. The purpose of this study was to assess changes in blood gases due to i.v. midazolam or sublingual flunitrazepam given as premedication in elderly patients for unilateral cataract surgery. METHODS. Fifty patients over 65 years of age with treated arterial hypertension and other co-existing diseases (ASA III-IV) were randomly assigned to have: (1) i.v. midazolam titrated until they became drowsy (17 patients; 2.85 +/- 0.84 mg [mean +/- SD]); (2) sublingual flunitrazepam (16 patients; 0.005 mg/kg); or (3) no sedation (17 patients; controls). On entering the operating theatre, the radial artery was cannulated and the first blood gas analysis was obtained. The premedication was then given. At 5, 10, 20, and 30 min after premedication, before and 10 min after retrobulbar block, before operation, 5 and 15 min after the beginning of the operation, 10 and 20 min after administration of 500 mg acetazolamide i.v. during the operation, and 10 and 20 min after the operation additional arterial blood samples were analysed (a total of 15 measuring points). Pulse oximetry, invasive blood pressure, and ECG were continuously monitored. All patients received oxygen 3 l/min during the operation by nasal cannula. Differences between the three groups were analysed by Student's t-test or U-test and a P value < 0.05 was considered significant. RESULTS. The patient demography, including duration of anaesthesia and operation, was similar in the three groups (Table 1). No significant differences were seen in heart rate, mean arterial pressure, PaO2, pulse-oximetric oxygen saturation (SpO2), base excess, or serum bicarbonate levels. The PaCO2 increased in patients after midazolam (P < 0.01) and flunitrazepam (P < 0.05) until the beginning of the operation compared with the control group (Fig. 3); 20 min after the operation there was still a significant difference between the midazolam group and the controls. SaO2 was significantly (P < 0.05) lower in the midazolam group 10 and 20 min after administration of premedication compared with the control group, but was within physiological limits (Fig. 5). Despite titration, 2 patients had severe respiratory insufficiency 3 min after midazolam: the SpO2 decreased below 85% and the paO2 below 55 mmHg. The paCO2 was higher (P < 0.05) in the midazolam group 10 min after acetazolamide compared with the controls. CONCLUSIONS. The results of the study show the potential hazards of i.v. midazolam in the elderly. If sedation is required for cataract surgery under local anaesthesia, we recommend sublingual flunitrazepam or the use of benzodiazepines with lower hypnogenic effects in the elderly. A thorough preoperative discussion of anaesthesia and the operation might be an adequate substitute for any premedication in high-risk patients; the best blood gas analysis results were obtained in the control group.
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PMID:[Premedication in retrobulbar anesthesia. A blood gas analysis comparison of sublingual flunitrazepam and intravenous midazolam]. 146 54

Several studies comparing retrobulbar block (RB) and general anaesthesia (GA) for cataract surgery in the elderly have been published. Most of them were retrospective. Our prospective study was designed in order to determine the benefits or disadvantages using RB or GA. Arterial blood gases (ABG) and cardiovascular stability were explored in high-risk patients undergoing elective unilateral cataract extraction. METHODS. Forty patients over 65 years of age and with other co-existing diseases (ASA III-IV) were allocated randomly to receive either GA or RB. No premedication was given to either group of patients. On arrival in the anaesthetic room, a radial artery was cannulated for collection of blood samples and direct monitoring of the blood pressure. Pulse oximetry and ECG were continuously monitored in all patients, the end-expiratory CO2 (F(eexCO2)) only in the GA group. GA was induced with vecuronium 0.1 mg/kg and thiopentone 5 mg/kg; the lungs were ventilated with 100% oxygen. After intubation of the trachea controlled mechanical ventilation was continued with N2O/O2 (55:45) and enflurane 1%-2%. Only enflurane concentrations were varied to correct changes in mean arterial pressure (MAP) if these exceeded +/- 20%. Respiratory frequency and tidal volume were kept constant until completion of surgery. The patients were extubated when they were able to ventilate more than 5 1/min (pressure support 10 cmH2O; PEEP 5 cmH2O). After extubation no O2 was given. In the RB group neural block was undertaken with prilocaine 2% (3 ml) as a retrobulbar injection and prilocaine 1% (5 ml) to block the facial innervation of the orbicularis muscle (Van Lint, O'Brien). Oxygen 3 1/min was administered by nasal tube during the operation. Nine arterial samples for blood gas analysis were collected: (1) control; (2) before operation; (3) 5 min after beginning the operation; (4) 15 min after beginning the operation and before i.v. administration of 500 mg acetazolamide over 5 min; (5) after acetazolamide; (6 and 7) 10 and 20 min after acetazolamide; and (8 and 9) 15 and 30 min after operation (RB) or extubation (GA). RESULTS. The patient demography, including duration of anaesthesia and operation, was similar in both groups (Table 1). Four patients in the GA group (2 needed O2 after extubation because of hypoxaemia) and 2 in the RB group were excluded. No significant differences were seen in base excess (BE) and standard bicarbonate (SHCO3). Arterial O2 tension, arterial O2 saturation, and pulse-oximetric O2 saturation were higher in the RB group intra- and postoperatively (Figs. 1, 3, 4). Arterial CO2 tension (PaCO2) was significantly higher in the GA group during the pre- and postoperative period (Fig. 2), but not during the operation. The PaCO2- F(eexCO2) gradient ranged between 5 and 9 mmHg. Administration of acetazolamide did not influence this gradient by regressive analysis. The postoperative outcome of the patients was comparable in both groups. Nausea or vomiting did not occur. MAP was significantly higher in the RB group during the operation. No significant differences were seen in the pre- and postoperative period. Heart rate in the GA group was higher only after extubation, but was within physiological limits. DISCUSSION. Despite the differing results between the two groups, our study showed no important advantage related to either RB or GA. Changes in ABG, MAP, and heart rate during the investigation period were within physiological limits in elderly patients. Intravenous acetazolamide did not influence ABG in a significant manner. With regard to the preference of each patient, we recommend both RB and GA for cataract surgery in high-risk patients on the assumption of sufficient preoperative treatment of co-existing diseases. In conclusion, cardiovascular and ABG stability were maintained during both anaesthetic techniques.
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PMID:[General anesthesia vs. retrobulbar anesthesia in cataract surgery. A randomized comparison of patients at risk]. 152 60

The normal internal pH (pHi) of the amphibian lens, measured using ion-sensitive microelectrodes, is 7.1 (pHo = 7.4) and the membranes appear to be relatively impermeable to hydrogen ions. Perifusing the lens with 100% CO2 appeared to be the most efficient way of decreasing pHi, which fell to 6.3 after an exposure lasting 30 min. Accompanying this acidification, there was a rapid depolarization of membrane potential (Em), a decrease in membrane resistance (Rm) and increase in internal or bulk resistance (Ri). These changes did not occur if the external pH alone was decreased. All changes were reversible, although the time course of Ri recovery was faster than the others. The decrease in membrane resistance could be prevented if the chloride concentration in the external solution was reduced, suggesting that internal acidification opens chloride channels in the amphibian lens. Since chloride ions are normally close to equilibrium across amphibian lens membranes, it is suggested that the pH-induced depolarization is due to a decrease in potassium conductance. The increase in internal resistance on perifusing with CO2 is most likely due to a closing of gap junctions between the fibre cells. The relationship between internal conductance and pHi was very similar to that obtained in other tissues and could be fitted by the Hill equation with n = 6 and pK = 6.9. Fibre junctional conductance seems sensitive to small changes in hydrogen ion concentration around the resting pH. Two agents, aspirin and cyanate, that are believed to influence cataract development, slowed the recovery of Em, Rm and Ri during recovery from an acid load.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Internal acidification modulates membrane and junctional resistance in the isolated lens of the frog Rana pipiens. 154 38

The effect on invasive and non-invasive oxygen, carbon dioxide and haemoglobin saturation measures of two repeated doses of alfentanil 0.5 microgram/kg were tested in 16 patients scheduled for elective cataract surgery under periocular anaesthesia. Alfentanil caused an acute respiratory depression, which was demonstrated as increased levels of arterial and end-tidal carbon dioxide and concomitant decrease in arterial and end-tidal oxygen levels as well as decreased arterial blood saturation and pulse oximeter readings. There was a good correlation between the non-invasive respiratory parameters and blood gas levels, as well as between pulse oximetry numbers and oxygen saturation of arterial blood. Therefore, hypoventilation and concurrent hypoxaemia can be predicted by monitoring end-tidal CO2.
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PMID:Comparison of non-invasive respiratory and arterial blood gas analysis. A recovery room study on acute respiratory depression. 212 59

During cataract surgery, both the surgeon and the anesthesiologist need access to the patient's face. At our institution we achieved a working compromise by using an oxygen insufflating hoop, which allowed the surgeon access to the eye and a sterile field. The patient's airway was kept free by the hoop, and the patient breathed a high inspired oxygen fraction. We measured the partial pressure of carbon dioxide (PCO2) of the gas mixture under the surgeon's drapes because they form a semiclosed breathing system for the patient. Accumulation of CO2 occurred in all patients (mean +/- SD, 6.1 +/- 3.1 mmHg), but an oxygen flow of 10 L/min through the hoop prevented an additional rise of CO2 levels during the operation. Reducing the oxygen flow below 10 L/min led to increased retention of CO2 under the drapes. Paper drapes are permeable to CO2, but plastic drapes are impermeable. We did not measure the arterial partial pressure of CO2, and so we do not know whether CO2 accumulation was accompanied by respiratory acidosis.
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PMID:Accumulation of carbon dioxide during eye surgery. 251 30

We investigated the effect of an antitransferrin receptor immunotoxin (454A12-rRA) on proliferating human and baboon lens epithelium in vitro. Human and baboon lens epithelial cells grown in modified TC-199 medium at 35 degrees Celsius in 7% CO2 were seeded in 24 well plates at a density of 17,500 cells/ml to 40,000 cells/ml. The cells were exposed to various concentrations of 454A12-rRA for seven days. The sensitivity of proliferating human lens epithelium to 454A12-rRA was dependent on the dose, with a 60% to 70% reduction in cell counts at immunotoxin concentrations of 100 ng/ml and above. The immunotoxin had no significant effect on baboon lens epithelium in vitro, which suggests that it is specific for human tissue. By preventing the proliferation of human lens epithelial cells, immunotoxin 454A12-rRA may be useful in the management of posterior capsule opacification after planned extracapsular cataract surgery.
J Cataract Refract Surg 1994 Sep
PMID:Inhibition of proliferating lens epithelium with antitransferrin receptor immunotoxin. 799 6

The authors present an account on the development of surgical techniques used in operations of cataract. Surgery of cataract was started on April 8, 1745 when the Frenchman Jaques Daviel made the first extraction of an opaque lens by limbal incision. This new method was enforced, however, very slowly and only after 100 years it finally celebrated victory over the hitherto widely used reclination. In the fifties of the present century a great advance in the surgery of cataract was the introduction of cryoextraction; at the First Ophthalmological Clinic a double-jacket instrument was designed which was filled with crushed CO2. The first cryoextraction was made at the authors' department on October 7, 1964, it was the very first operation of this type in Czechoslovakia.
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PMID:[From Beer's knife to the tunnel incision]. 819 15

An 8-year-old boy with galactose-1-phosphate uridyl transferase (GALT) deficiency presented with hypotonia, muscle hypotrophy, hepatomegaly, bilateral cataract and mild mental retardation. Two brothers showed a GALT activity consistent with a homozygotic condition and both parents were found to be heterozygotes for this defect. Histological and ultrastructural examination of muscle biopsy specimens showed several necrotic fibres. GALT activity was undetectable in skeletal muscle and muscle tissue cultures; myotubes converted galactose to CO2 at a lower rate than controls. Galactose-1-phosphate was increased in the patient's red cells and muscle tissue. GALT deficiency, not previously described in muscle, may be of pathogenic relevance in determining the myopathic features present in GALT deficiency syndrome.
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PMID:Clinical and biochemical evidence of skeletal muscle involvement in galactose-1-phosphate uridyl transferase deficiency. 832 30

The use of lasers in medicine and especially surgery is rapidly expanding in many disciplines from clinical laboratory to the office practice and operating room. It is essential that users of this powerful tool have knowledge of their potential hazards and the measures to protect patients and personnel against injuries or undesired effects. Below, we have included information about the way lasers are classified; the development of protective standards; the current status of protection standards that apply to lasers, especially those used in medicine/surgery; the specific kinds of hazards associated with medical/surgical applications; and the measures by which hazards have been controlled. Since laser technology is still a young field, it is likely that problems unknown at present will occur and methodologies for controlling hazards will evolve. The American National Standards Committee produced the first consensus standard Z136.1 in 1973. The Standard was revised in 1976 to accommodate differences in biological effects for different wavelengths in the visible spectrum. The ANSI Standard has been revised again in 1980, and currently (1984) there are two additional standards in preparation, Z136.2 and 136.3, which treat the safe use of light-emitting diodes and the safe use of lasers in the health care environment, respectively. Most surgical and medical lasers are Class III or IV. Some lasers have a Class IV therapy level beam plus a Class I or II alignment beam. When using lasers, it is possible to generate incandescence or fluorescence in an irradiated object. This can occur even with protective eyewear, because the correlated radiations are usually of a different wavelength. Generally, this should not be a problem when beams are directed at biological material. However, hazard could be caused by lasers designed to produce fluorescence. Control of correlative radiation in a laser system is required in the federal regulations. Hazards of lasers may be grouped as those to the eye, skin and associated hazards, fire, x-rays, electrical, fumes, toxic materials, etc. Effects on tissue are governed by the following factors:--the energy or power density of the beam;--the absorption in tissue at the laser wavelength;--the time the beam is held at a given area.;--the protective effects of heat removal by thermal conduction and by circulation. Eye hazards include thermal burns or acoustical disruption (shock waves) from high-powered or high-energy beams in the visible and near infrared wavelengths. Direct beam exposure or specular or diffuse reflaction from these very high-power lasers can also cause injuries to other parts of the retina. For example, beams can directly penetrate through the sclera and cause retinal injury. Near ultraviolet (less than 400 hm) and far infrared (.3000 hm including CO2 lasers) can cause moderate to severe corneal burns. Far ultraviolet (200-315 nm), mid infrared (1400-3000 nanometers) can cause welders' flash or snow blindness and chronic exposure could cause cataract, and exposure to ultraviolet rays may be carcinogenic. For CO2 lasers, the far infrared radiation is attenuated by plastic goggles, or by glasses, or quartz. Other eyewear with special filters is used for different lasers. The whole personnel who may be exposed to direct beams, specular reflections, and many times diffuse reflections must wear protective eyewear. In all cases the surgeon and others viewing the procedure through the endoscope need glasses or suitable protective lenses installed in the endoscope. Persons who are not viewing the beam may not need to wear protective glasses with the same level of optical density. Glasses may be selected to provide protection for lasers operating in the visible wavelength to the point where the normal aversion response could protect the individual.
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PMID:[Classification of laser irradiation and safety measures]. 986 31

We investigated transcutaneous partial CO2 and O2 pressures and respiratory rate in unpremedicated elderly patients of ASA physical status 1 to 3 who underwent cataract surgery under retrobulbar anaesthesia. In group A no air suction was used. In group B suction was applied under the sterile drapes to avoid rebreathing of CO2. In group A transcutaneous partial CO2 pressure and respiratory rate significantly increased compared with baseline, whereas in group B they remained constant. In both groups transcutaneous partial O2 pressure and oxygen saturation as measured by pulse oximetry significantly rose after insufflating oxygen 31.min-1. Heart rate and mean arterial blood pressure remained constant. Our results demonstrate that the application of suction near the patient's head prevents CO2 rebreathing and subsequent hypercapnia associated with an elevated respiratory rate. The use of suction makes it unnecessary to raise oxygen administration. Suction combined with monitoring of partial CO2 pressure using transcutaneous sensors should be used in all ophthalmological operations under retrobulbar anaesthesia.
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PMID:Transcutaneous CO2/O2 and CO2/air suction in patients undergoing cataract surgery with retrobulbar anaesthesia. 1019 29


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