Treatment of acute stroke with hyperbaric oxygen: time window for efficacy.

We conducted a retrospective statistical analysis of the Heyman, Saltzman, Whalen 1966 study of 22 stroke patients treated with hyperbaric oxygen (HBO2)--13 of them one to five hours post-stroke. We examined patients who received HBO2 treatment within seven hours post-stroke. An exploratory logistic regression analysis examining the influence of time post-stroke, time in chamber and dose of HBO2, range 2.02 atmospheres absolute (ATA) to 3.04 ATA, was conducted. Only time post-stroke was a significant influence for recovery, with each passing hour decreasing the chance of at least partial transient recovery by 62% - odds ratio: 0.38 (95% CI: 0.15 -0.95), p = 0.039. In the one- to five-hour group of 13 patients, nine (41% of 22) had recovery or recovery with relapse. This represented 69% (+/- 25% SE) of this time frame. Only two of the nine had permanent recovery. Past six hours poststroke, only one patient (11% +/- 21% SE) had partial recovery with relapse. The other eight past six hours had no recovery at all. The first three hours post-stroke HBO2 administration has the most promise for efficacy and improvement of rtPA therapy. HBO2 may also prove to be a useful challenge pre-rtPA administration to assess the risk-benefit ratio for giving rtPA.

Anesthetization of porpoises for major surgery.

Comparison of three porpoises (Tursiops truncatus and Lagenorhynchus obliquidens) given nitrous oxide with 18 given halothane, with complete documentation of reflexes and comprehensive physiological monitoring, showed halothane to be a suitable anesthetic for major surgery while nitrous oxide was found to be inadequate. In addition, sodium thiopental administered intravenously was successfully used to facilitate intubation procedures. This development eliminated the need to intubate awake porpoises.

Sudden hearing loss due to diving and its prevention with heparin.

Vascular embolic and thrombotic problems postulated to be the cause of inner ear sudden deafness have been reported with decompression sickness also. Decompression sickness has been found to lead to cochlear potential loss in the guinea pig, and these losses are minimized by the prophylactic administration of heparin. Preliminary results show that inner ear hemorrhage may be associated with diving deafness, but plasma protein leakage into the perilymph of the ear may precede the hemorrhage. Inner ear hemorrhage in diving deafness seems to be restricted to the microcirculation. Until we gain a better understanding of the pathophysiology of diving induced deafness, it would be premature to consider agents such as heparin for the treatment of the problem in man.

Relationship of sleep, respiration, and anesthesia in the porpoise: a preliminary report.

The porpoise, an air-breathing mammal whose habits are entirely aquatic, presents special problems of respiration, sleep, and anesthesia. These problems have been studied in three species, Tursiops truncatus, Lagenorhynchus obliquidens, and Phocoenoides dalli. The respiratory rhythm is unusual in that there is an extended pause-an apneustic plateau-between periods of expiration and inspiration. This rhythm has been observed under waking conditions, during sleep, and also when the animal is anesthetized. Two kinds of sleep behavior have been identified in Tursiops and Lagenorhynchus. In one of these, which is a light phase, the animal rests on the tank bottom for short periods, up to perhaps four minutes, and then comes to the surface to breathe. In a deeper phase the animal maintains itself at the surface for extended periods, breathing in an automatic fashion. In Phocoenoides no sleep behavior has been observed at any time.I have examined the special theory of Dr. John C. Lilly regarding respiration and sleep in the porpoise, which is based upon the assumption that respiration in this animal is altogether voluntary, and from my observations have concluded that respiration in the porpoise can be automatic or can be brought under voluntary control, just as in other mammals. Also the anesthetization of this animal can be carried out safely by methods that correspond closely to those employed in other animals.

Hearing in the giant sea turtle, Chelonia mydas.

Measurement were made of the cochlear potentials in three specimens of the giant sea turtle, Chelonia mydas, in response to both aerial and mechanical stimulation of the ear. The results show maximum sensitivity in the region of 300 to 400 Hz, with a rather rapid decline in sensitivity for lower and especially for higher tones. The upper limit for the observation of cochlear potentials without injury is 2000 Hz, and a practical limit of usefulness of this ear is probably about 1000 Hz.

Cochlear Structure in the Dolphin, Lagenorhynchus obliquidens.

The cochleas of five specimens of the Pacific white-sided dolphin, Lagenorhynchus obliquidens, that had been fixed by intravital perfusion, embedded in celloidin, and sectioned in a continuous series, were studied with particular attention to the numbers and distribution of hair cells and ganglion cells. The number of inner hair cells is estimated as 3272 and the number of outer hair cells is estimated as 12,899, for a total of 16,171 cells. The ganglion-cell population is estimated as 50,412 after correction for cell splitting in the sectioning process.

Spontaneous genetic hypertension in the rat and its relationship to reduced ac cochlear potentials: implications for preservation of human hearing.

We present controlled laboratory studies of the spontaneously hypertensive rat which indicate that hypertension is an important pathophysiological risk factor in age-related hearing loss. Our results are in concert with previous retrospective clinical studies that pointed to this possibility in man. Hypertension as a risk factor for hearing loss is within the bounds of known measures of diagnosis, treatment, and even prevention, with monitoring early in life. Because hypertension is such a major public health problem in the United States, in view of our results it is possible that its treatment and early diagnosis will benefit a significant number of people who would otherwise lose their hearing with advancing age. We compared the round window ac cochlear potential-sensitivity and -intensity functions in 10 female spontaneously hypertensive rats and 10 female normotensive Wistar-Kyoto control rats. The animals were all 12 months old and weighed between 170 and 250 g. The normotensives had higher maximum cochlear potential-intensity values compared with the hypertensives: 1,000 Hz (P less than 0.005), 5,000 Hz (P less than 0.005), and 10,000 Hz (P less than 0.01). One-microvolt isopotential cochlear potentials for the low frequencies of the normotensives showed greater sensitivity than those of the hypertensives: 100 Hz (P less than 0.05), 200 Hz (P less than 0.10), 290 Hz (P less than 0.05), and 2,000 Hz (P less than 0.10). Blood pressure of the hypertensive group was significantly greater than that of the normotensive rats (P less than 0.001). The hearts and aortas of the hypertensive group were hypertrophied. Autonomic imbalance, platelet aggregation, decreased arterioles, and natriuretic hormone were discussed as possible etiologies for the measured sensory hearing loss.

The Cochlea of the Dolphin, Tursiops truncatus: General Morphology.

The anatomy of the cochlea of the dolphin Tursiops truncatus was studied in a number of specimens after fixation by vital perfusion, cellodin embedding, and serial sectioning. The results reveal the general structural relations and cellular detail up to the limits of light microscopy. A description is given of the variations of structure along the course of the cochlea, in which there are many departures from the typical mammalian form, especially in the compact quality of the tissues and the sturdiness of its elements. Apparently these features represent an adaptation of the cetacean ear to the reception of high-frequency sounds.

Cochlea of the dolphin, Tursiops truncatus: the basilar membrane.

In the dolphin Tursiops truncatus, the basilar membrane over its course its course from basal to apical ends shows a systematic variation in width and in the manner and rigidity of its suspension. The suspension is by bony laminae on both the outer and inner edges in the basal region, and by progressively less rigid attachments in the more apical regions, until near the apex the membrane is held only by connective tissue. The basilar membrane shows an unusual variation in width of 14 times, ranging from an astonishingly small value of 25 mum at the basal end to a value toward the apex of about 350 mum. This structural variation is in harmony with the extension of sensitivity of the dolphin ear into the very high frequencies, and suggests unusual capabilities of pitch discrimination in this high range.

The cochlea of the dolphin, Tursiops truncatus: hair cells and ganglion cells.

A study of the cochlear hair cells in Tursiops truncatus showed 3451 inner and 13,933 outer hair cells, for a total of 17,384. This total is of the same order of magnitude as the value of 14,975 for the human ear. Determination of the ganglion cell population for the dolphin gave a total of 95,004 cells, which is about three times as many as in man. The large number of hair cells in the dolphin ear suggests a high order of auditory proficiency in general, and especially a marked ability of tonal differentiation. The large ratio of ganglion cells to hair cells suggests unusual capabilities in the utilization of auditory information.