Intragastric pressure and its relevance to protective cricoid force.

Cricoid pressure is frequently used to protect the anaesthetised and paralysed patient from passive regurgitation. Although intragastric pressure (Pga) drives regurgitation, its relevance in the setting of protective cricoid force has been largely ignored. We sought to define the likely range of Pga encountered in the population at risk. We studied 100 consecutive patients presenting for surgery requiring mechanical ventilation. We measured respiratory swings in Pga during mechanical ventilation in the paralysed state following rapid sequence induction (n = 24) and routine induction of anaesthesia (n = 76). Pga (mmHg) in the whole group recorded at end-inspiration (Pga-In) and end-expiration (Pga-Ex) was [mean (SD)]: Pga-In 6.48 (2.60) mmHg and Pga-Ex 3.23 (2.24) mmHg. We found no correlation between Pga and body mass index (r2 = 0.018). These findings have implications for the level of cricoid force required to protect a patient during the induction of anaesthesia.

Percutaneous dilational tracheostomy. Malposition leading to delayed weaning.

We report a patient in whom delayed weaning from ventilatory support was caused by the malposition of a percutaneous dilational tracheostomy tube. A fold of mucosa, identified at tracheoscopy, was found to be the limiting factor, and the situation was resolved by removal of the tracheostomy and reintubation. We believe that the case supports the routine use of a bronchoscope to check the position of the tracheostomy tube.

Management of contact lens patients with pingueculae or pterygia.

Diplomates in the Contact Lens Section of the American Academy of Optometry were surveyed to determine how they managed contact lens patients with pingueculae or pterygia. Responses indicated that many patients with these conditions can be successful contact lens wearers. Specific management techniques used by these practitioners are reported.

A case of monocular triplopia of lenticular origin.

A 70-year-old male experienced unilateral monocular triplopia of lenticular origin. The images formed a nearly equilateral triangle and were equally clear. It was noted that the images were formed by sections of the crystalline lens whose borders were parallel to the orientation of the anterior Y-sutures.

Intra-ocular pressure changes during rapid sequence induction of anaesthesia. A comparison between thiopentone and suxamethonium and thiopentone and atracurium.

The changes in intra-ocular pressure associated with two different anaesthetic induction and tracheal intubation techniques were compared (n = 30). After pre-oxygenation, Group A received thiopentone (5 mg/kg) followed by suxamethonium (1.5 mg/kg), both within 25 seconds, and Group B atracurium (0.5 mg/kg) followed by thiopentone (5 mg/kg) again both within 25 seconds. Tracheal intubation occurred after one minute in Group A and 2 minutes in Group B to allow for full paralysis. In Group A intra-ocular pressure did not alter significantly from baseline and the maximum increase was only 0.93 mmHg. The statistical type II error risk was consistently below 55% and all 95% confidence limits included negative values. Intra-ocular pressure in Group B was consistently lower than baseline (p less than 0.05) but with a longer induction-intubation interval. These results therefore provide valuable information about the 'balance of risks' when choosing a muscle relaxant for an inadequately starved patient with a penetrating eye injury.

Penetrating tracheal injury in a child.

A case is reported of a 3.5-year-old child with a stab wound in the neck, that penetrated the trachea. A pneumomediastinum was present. The anaesthetic problems are discussed and the child's management outlined.

Preventing ambiguity in visual field descriptions.

Ambiguity in the description of visual fields arises when a field measurement is specified as a number of degrees, without any reference to the measurement as a radius or diameter. Examples of confusing field descriptions in current literature are cited, with a recommendation for improved visual field notation.

Feeding polyunsaturated vegetable oils to lactating cows.

Holstein cows fed concentrate:hay diets also were fed for 14 days supplements of soybean oil plus casein, soybean oil protected from ruminal hydrogenation by encapsulation in a casein-formaldehyde matrix, cottonseed oil plus casein, or cottonseed oil protected with casein formaldehyde. The supplements were fed at rates to give a linoleic acid (18:2) intake of 225 g/day. Yields of milk and milk protein were not affected by treatment. Milk 18:2 was not increased by the unprotected soybean oil or cottonseed oil but was increased by protected soybean and cottonseed oil from a control of 2.3 to 5.7% of total milk fat. Milk 18:0 and 18:1 also increased. Compensatory declines were observed in milk 16:0 and 14:0 acids. In fecal fatty acids during the treatment periods, percentage of 18:2 of the total fat decreased and 18:0 markedly increased. These results indicate hydrogenation of the dietary oils in the alimentary tract or a differential absorption. Fecal 16:0 and 14:0 decreased.

Milk and tissue lipid composition after feeding cows protected polyunsaturated fat for two years.

The long-term effects of feeding Holstein cows plant lipids protected from microbial hydrogenation in the rumen were studied. Of particular interest were cow health and changes in fatty acid and cholesterol concentrations of milk and meat. Safflower oil-casein or safflower oil-casein treated with formaldehyde to impede microbial attack were fed to two groups of three cows as 10% of the concentrate ration for two lactations. Production of milk fat of cows fed the protected concentrate increased significantly. Linoleic acid of milk fat was twice normal, providing a polyunsaturated milk. Cholesterol of milk or meat did not increase even though cholesterol of blood plasma was higher in both groups fed safflower oil than in control cows. Cardiovascular systems showed no marked abnormalities and no differences that could be due to treatment. All cows maintained normal health and milk production throughout the experiment.