Disease relevance of Head-Down Tilt

• Hypoxia increased cGMP, cAMP, ALD, and PRA throughout the protocol and significantly potentiated the increase in cGMP during head-down tilt [1].
• Impaired suppression of plasma norepinephrine during head-down tilt in patients with congestive heart failure [2].
• This study demonstrates that the combination of CO2 pneumoperitoneum and the reverse Trendelenburg position does adversely effect cardiac output [3].
• Three of the five untreated hypertensive patients demonstrated unacceptable decreases of arterial pressure, associated with abrupt and severe bradycardia, and required immediate treatment (head-down tilt, atropine and methoxamine) [4].
• Circulating ANP levels rose with head-down tilt and exercise, and were raised in patients with chronic renal failure in proportion to volume status [5].

High impact information on Head-Down Tilt

• In most patients, the fall in blood pressure was transient (9 +/- 6 min, range = 2 to 30) and easily managed by slowing or stopping the infusion, placing the patient in the Trendelenburg position, or by administering an infusion of low-dose norepinephrine or dopamine [6].
• Heart rate, mean arterial pressure, plasma NE, NE clearance, and NE spillover were assessed before and after 30-minute infusions of AII, vehicle, or phenylephrine in the supine position and then after 15 minutes of head-up and 15 minutes of head-down tilt [7].
• MATERIALS AND METHODS: Twenty-five male white volunteers, 26-45 years of age, were randomly assigned to the control (n = 9), exercise (n = 9), and pamidronate (n = 7) groups and underwent 90-day 6 degrees head-down tilt bed rest [8].
• Further, deslanoside did not normalize the sympathetic response to mild baroreceptor loading produced by head-down tilt [9].
• No significant suppression of arginine vasopressin was seen during head-down tilt after mannitol infusion compared with values in a time control period [10].

Chemical compound and disease context of Head-Down Tilt

• Plasma atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP), cyclic adenosine monophosphate (cAMP), plasma aldosterone (ALD), and plasma renin activity (PRA) were measured in six healthy male volunteers who were exposed to a head-down tilt protocol during normoxia and hypoxia [1].
• The separate and combined acute effects of hypoxia (HY-11% O2), head-down tilt (HD-30 degrees) and fluid loading (FL-1.0 L saline) on hemodynamics and pulmonary gas exchange were determined in 17 anesthetized, mechanically ventilated dogs [11].
• These results indicate that: (1) if the proper technique is used, CPB in rabbits with direct cannulation of the ascending aorta is a reliable procedure, and (2) the effect of steroid on the prevention of brain edema related to the Trendelenburg position during CA is not established within the scope of this study [12].

Biological context of Head-Down Tilt

• 1. Procedures that increase atrial pressure, such as head-down tilt, result in an increase in plasma atrial natriuretic peptide (ANP) and a natriuresis, but a direct cause-and-effect relationship between these two responses has not been established [13].
• Heart rate, and the dose of sevoflurane, decreased significantly in the head-down tilt position [14].
• We used venous congestion strain gauge plethysmography (VCP) to measure the changes in fluid filtration capacity (K(f)), isovolumetric venous pressure (Pv(i)), and blood flow in six volunteers before, on the 118th day (D118) of head-down tilt (HDT), and 2 days after remobilization (Post) [15].
• Plasma AVP, serum osmolality, heart rate, central venous pressure, mean arterial pressure, and pulse pressure were assessed before and after a 0.06 ml.kg-1.min-1-infusion of 5% saline give over 90 min and then after 10 min of 30 degrees head-down tilt and 10 min of head-down tilt plus lower-body positive pressure [16].
• Basal values were compared with those obtained during inspiration, expiration, Valsalva maneuver, negative tilt (head down), and positive tilt (head up) with 0.8-1.6 mg p.o. nitroglycerin [17].

Anatomical context of Head-Down Tilt

• Common carotid artery blood flow changes were similar during nitroglycerin provocations in the two groups, but greater (P<0.05) during head down tilt in patients than in controls [18].
• Fractal analysis of cytoskeleton rearrangement in cardiac muscle during head-down tilt [19].
• CONCLUSION: After rotation in the plane of the affected semicircular canal, BPPV can interfere with the cardiac response to head-down tilt of the whole body [20].
• Both lower body positive pressure (LBPP) and head-down tilt (HDT) can induce fluid shifts from the lower body to the thorax and result in a loading of cardiopulmonary baroreceptors [21].
• CONCLUSION: Severe cerebrospinal fluid hypovolemia after craniotomy may produce a dramatic herniation syndrome that is completely reversed by the Trendelenburg position [22].

Associations of Head-Down Tilt with chemical compounds

• With the needle left in place and the patient in the Trendelenburg position, the contrast agent is sequentially displaced above any encountered extradural blocks by further injection of diluent or sterile saline into the caudal thecal sac [23].
• Materials and Methods: Plasma epinephrine and norepinephrine were evaluated in 29 patients who underwent laparoscopic retroperitoneal surgery in a half lateral decubitus position (group 1) or laparoscopic varicocelectomy in a Trendelenburg position (group 2) [24].
• We studied healthy humans under three separate conditions: control, acute 10 degrees head-down tilt (HDT), and saline infusion (SAL) [25].
• After 1 and 2 weeks of suspension in an antiorthostatic (head-down tilt) position, the mice were challenged with polyriboinosinic-polyribocytidylic acid to induce interferon-alpha/beta [26].
• We measured renal functions and hormones associated with fluid regulation after a bolus injection of aldosterone (Ald) during head-down tilt (HDT) bed rest to test the hypothesis that exposure to simulated microgravity altered renal responsiveness to Ald [27].

Gene context of Head-Down Tilt

• Effects of head-down tilt on atrial natriuretic peptide and the renin system in pregnancy [28].
• Modifications of plasma levels of tissue factor pathway inhibitor and endothelin-1 induced by a reverse Trendelenburg position: influence of elastic compression--preliminary results [29].
• Twenty-four men (31 +/- 3 yr) underwent 5 d of 6 degree head-down tilt: eight performed no exercise (CON), eight performed upright treadmill exercise (UPex), and eight performed supine treadmill exercise against LBNP at -51.3 +/- 0.4 mm Hg (LBNPex) [30].
• A head-down tilt on the other side induces central engorgement leading to a decrease of EPO concentrations [31].
• Alternative experimental models conducted to simulate the effects of weightlessness in humans such as head-down tilt (HDT) and lower body positive pressure (LBPP) have yielded less consistent results than those of water immersion (WI) with respect to renal function [32].

Analytical, diagnostic and therapeutic context of Head-Down Tilt

• After head-down tilt, subcutaneous injections of either placebo or 6 mg of sumatriptan were administered [33].
• A technique involving the use of reduced doses of hyperbaric bupivacaine (0.5%) in conjunction with head-down tilt appears to be useful for spinal anesthesia for cesarean section [34].
• INTRODUCTION: The purpose of this study was to identify the combinations of head down tilt (HDT) and lower body negative pressure (LBNP) that would counterbalance each other's effects on cardiovascular and endocrine variables to produce a "neutral point" (NP) [35].
• The effects of 10 degrees reverse trendelenburg position on ICP and CPP in prone positioned patients subjected to craniotomy for occipital or cerebellar tumours [36].
• Therefore, changes in PV were determined with an EB dilution technique in 10 males before, during, and after an acute posture change from seated to 6 degrees head-down tilt (HDT) [37].

References