Ketamine: yay or neigh? Implications for cardiovascular regulation and considerations for field use

Abstract. Caffeine placebo expectation seems to improve vigilance and cognitive performance. This study investigated the effect of caffeine and placebo expectation on vigilance and cognitive performance during 28 h sleep deprivation. Ten healthy males volunteered to take part in the double-blind, cross-over study, which required participants to complete five treatment periods of 28 h separated by 1-week wash-out intervals. The treatments were no substance (Control); caffeine 200 mg at 00:00 (C200); placebo 200 mg at 00:00 (P200); twice caffeine 200 mg at 00:00 and 04:00 (C200-C200); caffeine 200 mg at 00:00 and placebo 200 mg at 04:00 (C200-P200). Participants were told that all capsules were caffeine and given information about the effects of caffeine to increase expectation. Vigilance was assessed by a three-letter cancellation test, cognitive functions by the continuous addition test and Stroop test, and cardiovascular regulation by heart rate and blood pressure. Tests were performed bihourly from 00:00 to 10:00 of the second day. Results indicated that C200-P200 and C200-C200 were more alert (p < .05) than Control and P200. Their cognitive functions were higher (p < .05) than Control and P200. Also, C200-P200 scored higher than C200 in the letter cancellation task (p < .05). No test showed any significant differences between C200-P200 and C200-C200. The results demonstrated that the combination of caffeine 200 mg and placebo 200 mg expectation exerted prolonged positive effects on vigilance and cognitive performance.

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Interpreting Open- and Closed-Loop Transfer Relations Between Cardiorespiratory Parameters: Lessons Learned from a Computer Model of Beat-to-Beat Cardiovascular Regulation

Methods of Information in Medicine ◽

10.1055/s-0038-1636866 ◽

1997 ◽

Vol 36 (04/05) ◽

pp. 237-240

Author(s):

P. Hammer ◽

D. Litvack ◽

J. P. Saul

Keyword(s):

Computer Model ◽

Closed Loop ◽

Computer Models ◽

Cardiovascular Regulation ◽

Cardiovascular Control ◽

Lessons Learned ◽

Multiple Systems ◽

Response Characteristics ◽

Similarities And Differences

Abstract:A computer model of cardiovascular control has been developed based on the response characteristics of cardiovascular control components derived from experiments in animals and humans. Results from the model were compared to those obtained experimentally in humans, and the similarities and differences were used to identify both the strengths and inadequacies of the concepts used to form the model. Findings were confirmatory of some concepts but contrary to some which are firmly held in the literature, indicating that understanding the complexity of cardiovascular control probably requires a combination of experiments and computer models which integrate multiple systems and allow for determination of sufficiency and necessity.

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A Study on Evaluation of the Cardiovascular Regulation to Tilting by Noninvasive Method

Nippon Ronen Igakkai Zasshi Japanese Journal of Geriatrics ◽

10.3143/geriatrics.15.454 ◽

1978 ◽

Vol 15 (5) ◽

pp. 454-462

Author(s):

Kenji Teraoka

Keyword(s):

Cardiovascular Regulation ◽

Noninvasive Method

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Faculty Opinions recommendation of Effects of chronic baroreceptor stimulation on the autonomic cardiovascular regulation in patients with drug-resistant arterial hypertension.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1164467.626226 ◽

2009 ◽

Author(s):

Tom Lohmeier

Keyword(s):

Arterial Hypertension ◽

Cardiovascular Regulation ◽

Drug Resistant ◽

Baroreceptor Stimulation ◽

Resistant Arterial Hypertension

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Effects of Bromocriptine on Cardiovascular Regulation in Healthy Humans

Hypertension ◽

10.1161/01.hyp.25.5.1075 ◽

1995 ◽

Vol 25 (5) ◽

pp. 1075-1082 ◽

Cited By ~ 13

Author(s):

Hans P. Schobel ◽

Roland E. Schmieder ◽

Silke Hartmann ◽

Hartmut Schächinger ◽

Friedrich C. Luft

Keyword(s):

Cardiovascular Regulation ◽

Healthy Humans

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Variability of the haemodynamic responses to laboratory tests employed in assessment of neural cardiovascular regulation in man

Clinical Science ◽

10.1042/cs0690533 ◽

1985 ◽

Vol 69 (5) ◽

pp. 533-540 ◽

Cited By ~ 40

Author(s):

Gianfranco Parati ◽

Guido Pomidossi ◽

Agustin Ramirez ◽

Bruno Cesana ◽

Giuseppe Mancia

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Test Performance ◽

Blood Pressure Response ◽

Cold Pressor Test ◽

Cold Pressor ◽

Cardiovascular Regulation ◽

Pressor Test ◽

Carotid Baroreceptor ◽

Baroreceptor Stimulation

1. In man evaluation of neural cardiovascular regulation makes use of a variety of tests which address the excitatory and reflex inhibitory neural influences that control circulation. Because interpretation of these tests is largely based on the magnitude of the elicited haemodynamic responses, their reproducibility in any given subject is critical. 2. In 39 subjects with continuous blood pressure (intra-arterial catheter) and heart rate monitoring we measured (i) the blood pressure and heart rate rises during hand-grip and cold-pressor test, (ii) the heart rate changes occurring during baroreceptor stimulation and deactivation by injection of phenylephrine and trinitroglycerine, and (iii) the heart rate and blood pressure changes occurring with alteration in carotid baroreceptor activity by a neck chamber. Each test was carefully standardized and performed at 30 min intervals for a total of six times in each subject. 3. The results showed that the responses to any test were clearly different from one another and that this occurred in all subjects studied. For the group as a whole the average response variability (coefficient of variation) ranged from 10.2% for the blood pressure response to carotid baroreceptor stimulation to 44.2% for the heart rate response to cold-pressor test. The variability of the responses was not related to basal blood pressure or heart rate, nor to the temporal sequence of the test performance. 4. Thus tests employed for studying neural cardiovascular control in man produce responses whose reproducibility is limited. This phenomenon may make it more difficult to define the response magnitude typical of each subject, as well as its comparison in different conditions and diseases.

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