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Biomedical subjects

R C Hamilton

Publications and source records attributed to R C Hamilton.

At least 19 recordsLinked to original sources
PubMed1992

Comparison of plain with pH-adjusted bupivacaine with hyaluronidase for peribulbar block.

Fifty patients scheduled for cataract surgery under peribulbar block were randomised to receive either plain (pH 5.4) or pH-adjusted (pH 6.8 range 6.7-6.9) 0.75% bupivacaine. Hyaluronidase was added to both solutions prior to peribulbar block. The time of onset of akinesia of the globe and the need for supplementary injections were recorded by an independent observer. Patients who returned for surgery to the second eye received the alternative local anaesthetic solution for the second peribulbar block. The relative efficacy of the different anaesthetic solutions was compared in patients who underwent unilateral surgery (Group A, n = 50). In 12 patients (Group B) who underwent bilateral surgery, direct comparisons between eyes in the same patient were possible. In both groups of patients, eyes receiving peribulbar block with the pH-adjusted solution showed a shorter time to partial akinesia of the globe (P less than 0.05). However, there was no difference between the solutions in the time to complete akinesia of the globe, but the number of supplementary injections required for an effective block with the pH-adjusted solution was increased. Onset time to akinesia of the lateral and superior rectus muscles was shortened in patients receiving the pH-adjusted solution but there were minimal effects on the medial and inferior recti.

Anesthesia, Local↗
PubMed1992

Effect of combined peribulbar and retrobulbar injection of large volumes of anesthetic agents on the intraocular pressure.

A prospective randomized study was done in 79 patients undergoing elective routine cataract surgery in which the Kelman phacoemulsification technique was used with placement of an intraocular lens. In all the patients anesthesia was induced with both a peribulbar and a retrobulbar injection of a large volume (total 10.5 mL) of local anesthetic. The patients were randomly assigned to receive either the peribulbar (39 patients) (group 1) or the retrobulbar (40 patients) (group 2) injection first. The intraocular pressure (IOP) was measured five times during anesthesia. The mean elevation in IOP immediately after the first injection was 0.4 mm Hg in group 1, compared with 2.0 mm Hg in group 2. Twenty minutes after both injections had been given and a Super Pinky pressure device had been placed on the eye, the mean decrease in IOP from the preoperative value was 3.1 mm Hg in group 1 and 4.8 mm Hg in group 2. We conclude that a combined peribulbar and retrobulbar approach is a safe and effective alternative method of regional anesthesia for cataract surgery.

Aged↗
PubMed1992

Myasthenia gravis-like syndrome induced by topical ophthalmic preparations. A case report.

This case study reports on a 64-year-old female who presented for cataract surgery. She relayed a history of allergic responses to local anesthetics such as xylocaine, but was otherwise in good health. Upon instilling ophthalmic preparations into her eyes during routine ocular examination, she developed general muscular weakness but not other allergic-like symptoms. Further investigation established her myasthenic-like syndrome to be precipitated by an ophthalmic mydriatic preparation. She was able to undergo uneventful cataract surgery and enjoy 20/20 vision postoperatively, with proper management.

Cataract Extraction↗
PubMed1992

Technique of ocular regional anesthesia.

Regional anaesthesia by retrobulbar injection by the anaesthetist is recommended for day care ophthalmic surgery. Patient management and anaesthetic technique are detailed. The preferred anaesthetic is 2% lidocaine with hyaluronidase and adrenaline added. Fine, sharp pointed needles are recommended.

Ambulatory Surgical Procedures↗
PubMed1992

Brain-stem anesthesia as a complication of regional anesthesia for ophthalmic surgery.

Brain-stem anesthesia is a serious complication of orbital regional anesthesia that may occur when the injected local anesthetic agent gains access to the central nervous system by direct spread from the apex of the orbit via submeningeal pathways. In most studies the reported incidence rate during retrobulbar block is one case per 350 to 500 patients. Failure to recognize the condition or to treat it adequately may be life threatening. Treatment includes reassurance, intravenous administration of fluids, pharmacologic circulatory support or suppression of convulsions, and cardiopulmonary resuscitation. With proper treatment complete recovery is the rule. In all situations in which orbital block is to be done, basic cardiopulmonary resuscitation equipment and personnel familiar with its use are essential. Monitoring of the blood pressure, electrocardiography and pulse oximetry should be routine. Having the globe in primary gaze renders the optic nerve less vulnerable, and avoidance of deep penetration of the orbit is of great importance.

Anesthesia↗
PubMed1988

The effect of prophylactic acetaminophen administration on reactions to DTP vaccination.

To determine the effect of prophylactic acetaminophen on reactions after diphtheria and tetanus toxoids and pertussis vaccination, 282 children received either acetaminophen or placebo in a double-blind, randomized fashion before and 3, 7, 12, and 18 hours after vaccination. Fever and local and systemic reactions were monitored. Switching to known acetaminophen was permitted if the patient's temperature was 38.9 degrees C or higher or for moderate pain. Overall, the reaction score of acetaminophen recipients was significantly less than that of placebo recipients. The rates of occurrence of fever and fussiness and the degree of pain at the injection site were significantly reduced by acetaminophen administration. Children who received acetaminophen were less likely to be switched to "open" acetaminophen than placebo recipients. It is concluded that prophylactic acetaminophen as given in this study had a moderating effect on fever, pain, and fussiness after diphtheria and tetanus toxoids and pertussis immunization.

Acetaminophen↗
PubMed1988

Regional anaesthesia for 12,000 cataract extraction and intraocular lens implantation procedures.

Twelve thousand regional anaesthetics for cataract extraction and intraocular lens implantation surgery were administered by one anaesthetist over a period of 52 months in a free-standing outpatient surgical facility. The ophthalmologist, who did all the operations, assessed the quality of the blocks using an objective scoring system which is described. The first 3,595 patients had retrobulbar and seventh nerve blocks. The following 1,640 patients had higher volume retrobulbar blocking alone. The next 3,478 had peribulbar blocks, followed by 2,226 who had a modified form of peribulbar blocking. A final group of 1,061 had a combination of peribulbar and periorbital blocks with added retrobulbar injection if indicated. As the method of blocking evolved, the more closely was the goal of safe, painless and effective regional anaesthesia approached. The requirements for effective anaesthesia of this type are presented, the complications described and the importance of familiarity with the anatomy of the orbit and its contents stressed.

Aged↗
PubMed1987

The effect of corneal contact lenses on the oxygen tension in the anterior chamber of the rabbit eye.

The oxygen tension in the aqueous humor in the anterior chamber of rabbit eyes was measured continuously with a polarographic electrode. The normal oxygen tension in the anterior chamber was 23 +/- 2 mm Hg (mean +/- SD, n = 4). A contact lens was then placed on the cornea for at least 10 min and the drop in oxygen tension recorded. A hard polymethylmethacrylate lens reduced the oxygen tension by 16 +/- 4 mm Hg, and a larger hydroxyethylmethacrylate soft lens (Soflens) decreased oxygen tension by 17 +/- 4 mm Hg (mean +/- SD, n = 4). Comparable statistically significant decreases were seen with the Permalens, Polycon II, and Silcon lenses. Only the elastofilcon A lens (Silsoft) did not decrease the oxygen tension in the anterior chamber significantly.

Animals↗
PubMed1986

The infectivity of Encephalitozoon cuniculi in vivo and in vitro.

The infectivity of Encephalitozoon cuniculi grown in cell cultures was determined in cultured cells and in wild and domestic rabbits. The ratio of the total to tissue culture viable count was 1,300 (median of seven determinations). The mean ratio of intact spore count to total count, as determined by electron microscopy was 0.12. Although variation between infectivity experiments was large, the median animal infective dose contained 51 FFU (cell culture focus-forming units) for wild rabbits (Oryctolagus cuniculus) and 40 FFU for domestic rabbits. These two infectivities were not statistically different.

Animals↗
PubMed1985

Restoring balance.

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Defensive Medicine↗
PubMed1979

A marsupial oncovirus?

A virus-like particle was observed in two continuous cell lines derived from the marsupial Sminthopsis crassicaudata (Fat-tailed Dunnart). The development of the particle was similar to the development of D-type oncoviruses. Initially, a crescentof nucleoid material was observed near the nucleus in the region of the Golgi apparatus. This crescent developed into a doughnut-shaped-A-type particle which migrated through the cytoplasm towards the cell membrane where it budded either into a smooth membrane cytoplasmic vacuole or from the cell membrane. Only enveloped A-type particles were observed; no mature B-type, C-type or D-type particles were detected.

Animals↗
PubMed1979

An investigation of the route and progression of Encephalitozoon cuniculi infection in adult rabbits.

Rabbits infected either orally or intratracheally with cell culture-grown Encephalitozoon cuniculi were monitored regularly for serum antibody levels and E. cuniculi in the urine. Their responses were compared with intravenously inoculated and uninoculated control rabbits. All rabbits receiving E. cuniculi developed serum antibodies, generally within 3 weeks, and excreted E. cuniculi by 6 weeks. In the acute stage of infection, the organs most affected were lung, kidney and liver; the brain and gut were unaffected. However, during chronic infection, the brain, kidney, and heart were the only organs found to be involved. Antibody levels were very high at this stage. Thus both the oral and tracheal routes may be normal routes of infection with E. cuniculi in adult rabbits.

Animals↗