The Pressor Response to the Drinking of Cold Water and Cold Carbonated Water in Healthy Younger and Older Adults

Purpose: Water drinking has been proposed for the treatment of orthostatic hypotension because it can increase blood pressure in patients. This study aimed to investigate whether drinking water with a cold or carbonation stimulus would cause a more effective pressor response, and whether it would be greater in older than in younger adults.Methods: We assessed blood pressure and heart rate from non-invasive arterial pressure (a volume-clamp method) and type II electrocardiography in 13 healthy young adults (6 females, 7 males; mean age, 19.9 ± 1.1 years) and nine healthy older adults (all females; mean age, 71.4 ± 4.2 years) who drank 200 mL of cold, cold carbonated, and room temperature water.Results: The pressor response to the drinking of cold and cold carbonated water was greater than that to room temperature water in both younger and older participants (p < 0.05; changes in systolic blood pressure of room temperature water, cold water and cold carbonated water in young: 15.31 ± 9.66, 22.56 ± 11.51 and 32.6 ± 17.98 mmHg, respectively; changes in systolic blood pressure of room temperature water, cold water and cold carbonated water in elderly: 21.84 ± 14.31, 41.53 ± 19.82 and 48.16 ± 16.77 mmHg, respectively). In addition, the pressor response to cold and cold carbonated water was persistent during the recovery period by about 5–10 mmHg (p < 0.05). Furthermore, the pressor response during the drinking and recovery periods was greater in the older than in the younger participants (p < 0.05).Conclusion: Our data suggest that even smaller amounts of water are able to elicit a sustained pressor response, in particular if the water is cold and carbonated. We speculate that the pressor effect may render cold and carbonated water an appropriate first aid method against certain forms of acute hypotension.

Altered Cardiovascular Defense to Hypotensive Stress in the Chronically Hypoxic Fetus

The hypoxic fetus is at greater risk of cardiovascular demise during a challenge, but the reasons behind this are unknown. Clinically, progress has been hampered by the inability to study the human fetus non-invasively for long period of gestation. Using experimental animals, there has also been an inability to induce gestational hypoxia while recording fetal cardiovascular function as the hypoxic pregnancy is occurring. We use novel technology in sheep pregnancy that combines induction of controlled chronic hypoxia with simultaneous, wireless recording of blood pressure and blood flow signals from the fetus. Here, we investigated the cardiovascular defense of the hypoxic fetus to superimposed acute hypotension. Pregnant ewes carrying singleton fetuses surgically prepared with catheters and flow probes were randomly exposed to normoxia or chronic hypoxia from 121±1 days of gestation (term ≈145 days). After 10 days of exposure, fetuses were subjected to acute hypotension via fetal nitroprusside intravenous infusion. Underlying in vivo mechanisms were explored by (1) analyzing fetal cardiac and peripheral vasomotor baroreflex function; (2) measuring the fetal plasma catecholamines; and (3) establishing fetal femoral vasoconstrictor responses to the α 1 -adrenergic agonist phenylephrine. Relative to controls, chronically hypoxic fetal sheep had reversed cardiac and impaired vasomotor baroreflex function, despite similar noradrenaline and greater adrenaline increments in plasma during hypotension. Chronic hypoxia markedly diminished the fetal vasopressor responses to phenylephrine. Therefore, we show that the chronically hypoxic fetus displays markedly different cardiovascular responses to acute hypotension, providing in vivo evidence of mechanisms linking its greater susceptibility to superimposed stress.

Afferent Baroreflex Dysfunction: Decreased or Excessive Signaling Results in Distinct Phenotypes

Head and neck tumors can affect afferent baroreceptor neurons and either interrupt or intermittently increase their signaling, causing blood pressure to become erratic. When the afferent fibers of the baroreflex are injured by surgery or radiotherapy or fail to develop as in familial dysautonomia, their sensory information is no longer present to regulate arterial blood pressure, resulting in afferent baroreflex failure. When the baroreflex afferents are abnormally activated, such as by paragangliomas in the neck, presumably by direct compression, they trigger acute hypotension and bradycardia and frequently syncope, by a mechanism similar to the carotid sinus syndrome. We describe our observations in a large series of 23 patients with afferent baroreflex dysfunction and the cardiovascular autonomic features that arise when the sensory baroreceptor neurons are injured or compressed. The management of afferent baroreceptor dysfunction is limited, but pharmacological strategies can mitigate blood pressure swings, improve symptoms, and may reduce hypertensive organ damage. Although rare, the prevalence of afferent baroreflex dysfunction appears to be increasing in middle-aged men due to human papillomavirus related oropharyngeal cancer.

Comparison of Haemodynamic Effects of Levobupivacaine and Bupivacaine in Sub-arachnoid Block for Total Abdominal Hysterectomy

Introduction: Altered haemodynamics and arterial hypotension are the most prevalent untoward effects of sub-arachnoid block with bupivacaine. Use of levobupivacaine as pure S (-) - enantiomer of bupivacaine has progressively increased due to its lower cardiotoxicity, neurotoxicity and shorter duration of motor block. This study aimed to compare the haemodynamic status of levobupivacaine and bupivacaine when used with fentanyl in Sub-arachnoid block (SAB) among patients undergone total abdominal hysterectomy. Materials and Methods: This randomized clinical trial enrolled 80 gynaecological patients scheduled for total abdominal hysterectomy under SAB. Forty patients were randomly assigned as trial group (levobupivacaine+fentanyl) and forty as control group (bupivacaine+fentanyl). Main outcome measures in both groups considered intraoperative haemodynamic stability (acute hypotension), cardiotoxicity (bradycardia or tachycardia) and time of administration of first dose of postoperative analgesics. Results: Bupivacaine caused comparatively more significant slowing of heart rate at 25 and 35 minutes of operation. Though no significant differences were found in systolic blood pressure between two groups, bupivacaine caused significant reduction of diastolic blood pressure in comparison to levobupivacaine at 6, 9, 45 minutes and at the end of surgery. Mean pressure found significantly lowered at 6 minutes and at the end of surgery following bupivacaine administration. The incidence of acute hypotension was significantly low in trial group and postoperative analgesia was maintained longer duration with levobupivacaine in control group. Conclusion: Levobupivacaine in comparison to bupivacaine showed more effective and satisfactory haemodynamic stability in sub-arachnoid block with less incidence of intraoperative acute hypotension and provides prolonged postoperative analgesic effect. Medicine Today 2020 Vol.32(1): 29-32