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)

Vitreous replacement with air, pure octafluorocyclobutane (C4F8), and mixtures of 40% C4F8 and 60% air was done in owl monkeys to determine ocular toxicity and duration of gas within the vitreous compartment. Large volumes of gas mixture and pure C4F8 caused posterior subcapsular cataract formation. Pure C4F8 expands in the vitreous within 24 to 48 hours. A 1.0-ml mixture of 40% C4F8 and 60% air lasted 12.7 days and did not cause ocular changes. However, anterior chamber aqueous replacement with pure C4F8 or gas mixture resulted in cataract production. Twenty-four and fourty-eight hours after injection of 0.1-ml pure C4F8 in the vitreous of experimental rabbits, presence of oxygen, nitrogen, and carbon dioxide was shown by gas chromatographic analysis. This finding supports the hypothesis of volume expansion secondary to diffusion of above-mentioned gases inside the C4F8 gas bubble.
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PMID:Octafluorocyclobutane in vitreous and aqueous humor replacement. 80 78

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

We measured certain respiratory conditions (respiratory rate [RR], oxygen saturation [SO2], and end-expiratory carbon dioxide partial pressure [pCO2]) of 31 patients undergoing planned cataract surgery using local anesthesia in order to determine the effects of administering pure oxygen (3 L/min) by a nasal probe in 10 of them. In the patients who did not receive pure oxygen, at the end of surgery the mean RR was 15.8 +/- 4.4/min (maximum, 21; minimum, 6.4/min); the mean SO2 was 86.9% +/- 6.6% (maximum, 98%; minimum, 74%; in 11/25 patients, the SO2 was lower than 90%); and the mean pCO2 was 34.9 +/- 7.7 mm Hg (maximum, 46.5; minimum, 12.15; in 4/25 patients, the pCO2 was greater than 45 mm Hg). In the patients who received pure oxygen by a nasal probe, the mean SO2 increased intraoperatively from 80.6% +/- 5.8% to 96.9 +/- 2.9% (in no patients was SO2 lower than 90%). Therefore we recommend an intraoperative administration of pure oxygen by a nasal probe.
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PMID:O2 administration by a nasal probe improves respiration in cataract surgery after retrobulbar anesthesia. 196 23

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

Eye injuries sustained by 4 patients who took part in 'war games' (in which young men shoot at each other with pistols powered by compressed carbon dioxide and firing latex rubber bullets filled with non-toxic paint) are described. In 3 cases the injuries were severe, including traumatic cataract, and 1 of these patients has a permanent macula scar with vision reduced to 6/36. Although eye protection is recommended, it was found that in the 'battle situation' combatants did not always follow regulations. Attention is drawn to the seriousness of disregarding the need for correct protective glasses.
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PMID:Eye injuries associated with 'war games'. 278 25

This paper presents current clinical and experimental uses of the carbon dioxide laser and the results of our human and animal tissue fusion investigations. Trials were conducted with human scleral and corneal eye bank tissue and in albino rabbits. With power settings of 100 to 200 mW, optimal laser effect consisting of slight whitening and minimal edge shrinkage occurred between 10 and 70 mJ of total energy. No tissue adherence could be demonstrated with the parameters tested. A final study was made on the feasibility of sealing an epikeratophakia lenticle to its recipient bed using the carbon dioxide laser. The average force required to remove the button in the control experiments was 6.45 g and this increased to 6.99 g after laser treatment although no fusion was apparent. This was statistically significant (P less than .05).
J Cataract Refract Surg 1987 May
PMID:Carbon dioxide laser use in wound sealing and epikeratophakia. 310 90

Ten patients undergoing elective cataract surgery with local anesthesia were evaluated for rebreathing using mass spectrometry and arterial blood gas analysis. Results showed a 10 or 51 oxygen-air mixture with an inspired oxygen concentration of 50% (FIO2) administered via a face tent maintained normal blood gases and a satisfactorily low inspired carbon dioxide (FICO2) in conscious patients who were free of lung disease.
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PMID:Evaluation of rebreathing in patients undergoing cataract surgery. 312 84


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