Head-down Position Research Articles

Anesthesia affects olfaction and chemosensory event-related potentials

Objective Olfactory and trigeminal systems interact and contribute to the perception of odorants. This study was aimed at investigating the effect of local anesthesia on olfaction. Methods One percent of tetracaine on a cotton swab was applied intranasally at three different locations in 20 volunteers and 4% of lidocaine was applied to the olfactory cleft in a head-down position. Before and after anesthesia, self-assessment, psychometric testing and olfactory event-related potentials [OERPs, using H 2S and phenyl ethyl alcohol (PEA)], and chemosomatosensory event-related potentials (CSSERPs, using CO 2) were examined. Results Anesthesia at all four locations significantly lowered the perceived self-assessment of olfaction, while using the cotton swab only anesthesia in the middle meatus elevated threshold ( P=0.020), lowered discrimination ( P=0.015) and prolonged OERP (PEA, P=0.008; H 2S, P=0.016), as well as CSSERPs latencies (CO 2, P=0.020). However, complete temporary anosmia was only achieved after applying 4% lidocaine into the olfactory cleft. Conclusions Intranasal anesthesia applied with a swab reduced self-assessment of olfaction but was unable to produce anosmia. Psychometric test results were concordant with changes in chemosensory event-related potentials. Significance Temporary anosmia is technically difficult to achieve but could be demonstrated for the first time using local anesthesia. Even though anesthesia influences self-assessment, measurable olfactory function can remain unchanged.

Human cerebrovascular and autonomic rhythms during vestibular activation.

Otolith activation increases muscle sympathetic nerve activity (MSNA), and MSNA activation may alter associations among autonomic oscillators, including those modulating cerebral hemodynamics. The purpose of this study was to determine the influence of vestibulosympathetic activation on cerebral and autonomic rhythms. We recorded the ECG, finger arterial pressure, end-tidal CO(2), respiration, cerebral blood flow velocity, and MSNA in eight subjects. Subjects breathed at 0.25 Hz for 5 min in the prone and head-down positions. We analyzed data in time and frequency domains and performed cross-spectral analyses to determine coherence and transfer function magnitude. Head-down rotation increased MSNA from 7 +/- 1.3 to 12 +/- 1.5 bursts/min (P = 0.001) but did not affect R-R intervals, arterial pressures, mean cerebral blood flow velocities (V(mean)), or their power spectra. Vestibular activation with head-down rotation had no effect on mean arterial pressure and V(mean) transfer function magnitude. The two new findings from this study are 1) head-down rotation independently activates the sympathetic nervous system with no effect on parasympathetic activity or V(mean); and 2) frequency-dependent associations between arterial pressures and V(mean) are independent of vestibular activation. These findings support the concept that vestibular-autonomic interactions independently and redundantly serve to maintain steady-state hemodynamics.

Head-down tilt and manual hyperinflation enhance sputum clearance in patients who are intubated and ventilated

The purpose of this prospective randomised cross-over study was to measure peak expiratory flow rates during manual hyperinflation and to determine if the addition of a head-down tilt to physiotherapy treatment increased sputum production in patients who are intubated and ventilated. Twenty patients who were intubated, ventilated and haemodynamically stable were randomised to a sequence of physiotherapy treatment in a flat side-lying or a head-down tilt position. Peak expiratory flow rates were measured for each breath during manual hyperinflation using a Vitalograph peak flow meter. Sputum wet weight was collected for each treatment position and static pulmonary compliance was measured before and immediately following physiotherapy treatment. There was a significant increase in peak expiratory flow (p < 0.001) and sputum production (p = 0.008) in the head-down tilt position. The mean difference and 95% confidence intervals for expiratory flow were 0.17 (0.15 to 0.19) l/sec and for the wet weight of sputum 1.97 (0.84 to 3.10) g. The peak expiratory flow rate was sufficient to produce annular flow in both flat side-lying (1.97 +/- 0.09) l/sec and in the head-down tilt position (2.14 +/- 0.08) l/sec. Static pulmonary compliance improved significantly following physiotherapy treatment (p = 0.003). The mean difference and 95% confidence intervals pre- and post-treatment for static pulmonary compliance were 5.18 (2.14 to 8.22) ml/cmH(2)O. The results suggest that addition of a head-down tilt to physiotherapy treatment, including manual hyperinflation, in patients who are intubated and ventilated, increases sputum production and improves peak expiratory flow.

Effects of intra-abdominal CO2-insufflation on normal and impaired myocardial function: an experimental study.

Intra-abdominal pressure (IAP) elevation during CO2-pneumoperitoneum increases cardiac afterload and may enhance dysfunction of the already compromised heart. This study focused on the effects of acute IAP increases on left and right ventricular loadings and contractility in the heart with impaired global function. Impairment of myocardial function (IMF) was pharmacologically induced in 16 pigs by administration of halothane and propranolol, while baseline arterial pressure was maintained by intravenous phenylephrine. Intra-abdominal pressure was gradually increased by 10 mmHg up to 30 mmHg in the supine position (IMF group 1, n = 8) or in a head-down tilted position (IMF group 2, n = 8). In two control groups with normal myocardial function, IAP was also increased in the supine position or the head-down tilted position. Cardiac function in all groups was assessed by epicardial echocardiography, intraventricular pressure measurements and pulmonary artery catheterization. The increase in IAP was accompanied by a transient rise in LV end-systolic wall stress and reduced cardiac output significantly by 16-24% in all groups. In the IMF groups, LV end-diastolic transmural pressure increased by 34-60% to peak values of 24 mmHg, while cross-sectional LV end-diastolic areas remained unchanged. Increases in right ventricular end-diastolic volume and decreases in right ventricular ejection fraction as well as in cardiac output were most pronounced at IAP 20 mmHg and significantly stronger in both IMF groups than in the control groups (P < 0.001). Following the acute elevation of IAP, the right ventricular volume load shifted more extensively in the IMF groups than in the animals with normal myocardial function. Myocardial function in the impaired heart may worsen during IAP elevation due to right ventricular load alterations rather than a LV afterload increase.

Episcleral venous pressure of mouse eye and effect of body position

Purpose. To measure the episcleral venous pressure (EVP) of the mouse eye and to investigate the effect of body position on EVP and intraocular pressure (IOP). Methods. A microneedle connected to a pressure transducer was used to measure IOP in NIH Swiss white mice. To measure EVP, a reservoir connected to this transducer allowed modulation of the intracameral pressure by changing its height. As intracameral pressure was gradually lowered, there was an observable reflux of erythrocytes from an episcleral vein into Schlemm’s canal. The IOP at which this occurred was the endpoint of the EVP measurement. EVP and IOP were measured in a horizontal body position (0°) analogous to an awake mouse and at 30° and 60° head-down body position from the horizontal position. EVP was measured twice in each eye of 6 mice. Results. Mean IOP at 0°, 30° and 60° of head-down position was 16.5 ± 0.6, 18.2 ± 0.6, and 19.5 ± 1.8 mmHg, respectively. EVP (horizontal) was 9.6 ± 1.3mmHg (N = 6 eyes). EVP significantly increased with increasing degree of head-down position (SNK test, p < 0.05). EVP at 30° and 60° of head-down position was 11.2 ± 1.3 and 13.3 ± 1.5mmHg, respectively. Conclusions. Mouse EVP was successfully measured based on the detection of erythrocyte reflux from an episcleral vein into Schlemm’s canal. Both EVP and IOP increased with the degree of the head-down body position.

The Endotracheal Tube Moves More Often in Obese Patients Undergoing Laparoscopy Compared with Open Abdominal Surgery

We compared the incidence of movements of the endotracheal tube (ETT) within the trachea in morbidly obese patients undergoing either laparoscopic or open gastroplasty. In a double-blinded, prospective, controlled study, 60 patients (body mass index, 35–60 kg/m2) were equally allocated to either laparoscopic LapBand gastroplasty (study group; Group 1) or open laparotomy gastroplasty (control; Group 2), both under standardized general anesthesia. Movements of the ETT were assessed with chest auscultation, peak inspiratory pressure, ETco2, Spo2, and the Rapiscope™ at predetermined time points: after intubation (baseline values), 5 min before peritoneal inflation in Group 1 and 10 min postintubation in Group 2, at maximal abdominal inflation in Group 1 and 20 min into the procedure in Group 2, 5 min before and 5 min after changing the patient’s position from neutral to 10° head up and 10° head down in Group 1 and 30 and 40 min into the procedure in Group 2, 2 min after abdominal deflation and table repositioning in Group 1 and at 50 min in Group 2, and just before extubation in both groups. Twenty-one events of ETT tip movement occurred in both groups. The tube moved in 15 (50%) study (laparoscopy) group patients compared with 6 (20%) controls (laparotomy;P < 0.05), 12 of the former having moved downward either after maximal abdominal insufflation or in association with head-down positioning. The tubes of five study group patients (17%) advanced into the right bronchus, compared with none in the controls (P < 0.05). All changes in position were rectified only by the Rapiscope™.

ヘッドダウンによるベッドレスト試験が青年男子の腸内環境および菌叢に及ぼす影響

To clarify the change in intestinal microflora under a microgravity environment, we chose 12 health young men (22.2±3.2 years old) for a 20-day bed-rest experiment. After a 4-day adjustment period, the subjects were put to bed in a head-down position at an angle of 6°. The basic food intake was provided by a menu cycle of 4 days to maintain the body weight which contained 1, 931kcal of energy, 67g of protein (14% PE), 53g of fat (24% FE) and 291g of carbohydrate (62% CE).A comparison between the data for the experimental period of two weeks and the adjustment period shows that the number of Lactobacilli decreased by a significant level (p<0.05) and the number of Clostridium perfringens increased by a significant level (p<0.05) in the feces, while no change was apparent for the other bacteria.The results also demonstrate that, among the putrefactive substances (phenol, p-cresol, ethyl-phenol, indole and skatole) in the feces, p-cresol increased by a significant level (p<0.05) and phenol tended to decrease. A evaluation of the mental status by the Zung self-rating depression scale (SDS) indicated the onset of depression during the test period due to the lack of activity.These results suggest that the deterioration of the intestinal environment from the change in intestinal bacteria and the increase in putrefactive substances was caused by long-term stress induced by 20 days of bed rest under the microgravity environment.

Comparison of Changes in Arterial Blood Gases during Endoscopic Thyroidectomy, Laparoscopic Cholecystectomy and Gynecologic Laparoscopic Surgery

Background: Because laparoscopic surgery has many advantages compared with conventional methods, it has recently been applied to not only intraabdominal or intrathoracic surgery but also thyroidectomy. It is possible that arterial blood gases and hemodynamic variables can be changed by patient position and insufflation of pressurized CO2 into extraperitoneal or intraperitoneal space, so we examined the changes in arterial blood gases, end tidal CO2 (PETCO2) and hemodynamic variables during an endoscopic thyroidectomy with extraperitoneal CO2 insufflation, laparoscopic cholecystectomy and gynecologic laparoscopic surgery with intraperitoneal CO2 insufflation under N2O, enflurane inhalational general anesthesia. Methods: Forty ASA class I or II patients were included in this study, endoscopic thyroidectomy group (n = 10), laparoscopic cholecystectomy group (n = 18), gynecologic laparoscopic surgery group (n = 12). All patients were underwent controlled mechanical ventilation (tidal volume: 10 ml/kg, respiratory rate: 12/min) and the ventilator mode was fixed in this volume and rate until the end of the operation. The position of patients during the endoscopic thyroidectomy and laparoscopic cholecystectomy were under 5 degree reverse Trendelenburg position, whereas the gynecologic laparoscopic surgery was under a 10 degree head-down lithotomy position. Variables were measured before CO2 insufflation (10 minute after induction), 10, 20 and 30 minutes after CO2 insufflation and 40 minutes after CO2 deflation. Results: PaCO2 and PETCO2 were significantly increased during CO2 insufflation compared with preinsufflation values in all groups, but the magnitude of increases of PaCO2 and PETCO2 was not significantly different among the three groups. The mean magnitude of increases of PaCO2 at 10 minutes after CO2 insufflation were as follows: gynecologic laparoscopic surgery (6.21 2.0 mmHg), endoscopic thyroidectomy (5.07 2.3 mmHg), and laparoscopic cholecystectomy (5.01 G 2.2 mmHg).

Thermoregulatory Response to Intraoperative Head-Down Tilt

Thermoregulation interacts with cardiovascular regulation within the central nervous system. We therefore evaluated the effects of head-down tilt on intraoperative thermal and cardiovascular regulation. Thirty-two patients undergoing lower-abdominal surgery were randomly assigned to the 1) supine, 2) 15°–20° head-down tilt, 3) leg-up, or 4) combination of leg-up and head-down tilt position. Core temperature and forearm minus fingertip skin-temperature gradients (an index of peripheral vasoconstriction) were monitored for 3 h after the induction of combined general and lumbar epidural anesthesia. We also determined cardiac output and central-venous and esophageal pressures. Neither right atrial transmural pressure nor cardiac index was altered in the Head-Down Tilt group, but both increased significantly in the Leg-Up groups. The vasoconstriction threshold was reduced in both leg-up positions but was not significantly decreased by head-down tilt. Final core temperatures were 35.2°C ± 0.2°C (mean ± sem) in the Supine group, 35.0°C ± 0.2°C in the Head-Down Tilt group, 34.2°C ± 0.2°C in the Leg-Up group (P < 0.05 compared with supine), and 34.3°C ± 0.2°C when leg-up and head-down tilt were combined (P < 0.05 compared with supine). These results confirm that elevating the legs increases right atrial transmural pressure, reduces the vasoconstriction threshold, and aggravates intraoperative hypothermia. Surprisingly, maintaining a head-down tilt did not increase right atrial pressure.

A model for time-dependent flow in (giraffe jugular) veins: uniform tube properties

Computations are reported for a one-dimensional model of time-dependent flow in collapsible tubes representing long mammalian veins. The tubes are taken to have uniform intrinsic properties and we concentrate on the effect of longitudinal gravity. The main application is to the jugular vein of the upright giraffe, with given inflow rate from the head, a given pressure, slightly above the external, atmospheric pressure, at the downstream (vena caval) end, and a variety of initial conditions. We show that: (i) previously calculated steady flows are the long time limits of unsteady computations, although only after a considerable time in which slowly-decaying waves and elastic jumps propagate up and down, (ii) steady flows are indeed not found when the steady-flow analysis shown them not to exist, although the consequent unsteadiness is of such small amplitude as to be practically unimportant, (iii) the time taken for the flow to become steady when the neck is raised from the horizontal or the head-down position can be several seconds longer than the neck-raising time itself (3– 7 s ). We also find that roll-waves do not develop despite having been previously predicted for long collapsible tubes. Further application is made to the effect of postural changes on human neck and leg veins.

The effect of posture on cerebral oxygenation during abdominal surgery.

Performing surgery with a patient in the head-down position for several hours may cause marked facial and conjunctival oedema. It is not known whether oedema might also be occurring within the cranial cavity. This study, using near-infrared regional cerebral oximetry, was performed to see if there was any evidence of cerebral anoxia during operations performed with patients in the head-down position compared with those performed on patients who were flat. Patients managed in the head-down position did not demonstrate any reduction in regional cerebral oxygenation, but those who were managed flat did. An explanation of these paradoxical findings is elusive.

Intraocular pressure of juvenile loggerhead sea turtles (Caretta caretta) held in different positions

The intraocular pressure of 12 apparently healthy juvenile loggerhead sea turtles (Caretta caretta) was determined by applanation tonometry while the turtles were held in dorsoventral, ventrodorsal, and head-down suspended positions....

Influence of pneumoperitoneum and patient positioning on respiratory system compliance

Study Objective: To investigate the influence of pneumoperitoneum (PP) and posture on respiratory compliance and ventilation pressures. Design: Prospective, single blind trial. Patients: 10 female ASA physical status I and II patients scheduled for elective gynecologic laparoscopy. Setting: University medical center. Interventions: Anesthesia was performed as total IV anesthesia (TIVA) with propofol, alfentanil, and atracurium. After induction of anesthesia and orotracheal intubation, the lungs were ventilated to maintain partial pressure of CO 2 (P ETCO 2) of 30 ± 3 mmHg. Ventilation was kept constant. As gas mixture oxygen and air 1:1 was used without positive end-expiratory pressure (PEEP). Measurements: Measurements were taken before and after creation of pneumoperitoneum with an intraabdominal pressure (IAP) of 10 mmHg, of 15 mmHg in 20° head-down tilt, then in 20° head-up tilt, and after deflation of PP. We determined peak inspiratory pressure (PIP), mean airway pressure (mPaw), P ETCO 2 , expiratory minute volume (V̇ E), heart rate (HR), and systolic (SBP), diastolic (DBP), and mean arterial pressure (MAP). Respiratory system compliance (C eff rs) was calculated as quotient of tidal volume (V T) and PIP. Main Results: After creation of PP (IAP 10 mmHg), there was a significant increase of median PIP (3 cmH 2 O), mPaw (1 cm H 2 O) and arterial pressure (BP), (MAP by 7 mmHg), C eff rs decreased by 6 mL · cm H 2 O -1 . Increase of IAP to 15 mmHg led to a further increase of PIP (2 cm H 2 O) and mPaw (1 cm H 2 O), and a further decrease of C eff rs by 5 mL cm H 2 O -1 ; BP decreased (MAP by 5.5 mmHg). Head-up or head down positions showed no significant hemodynamic or pulmonary changes. P ETCO 2increased from 29.5 to 36 mmHg at an IAP of 15 mmHg, but then no further changes were noticed. Five minutes after deflation of pneumoperitoneum all values returned to baseline levels. Conclusions: Creation of PP at an IAP of 15 mmHg reduced respiratory system compliance, and increased peak inspiratory and mean airway pressures, which quickly returned to normal values after deflation. Head-down or head-up position did not further alter those parameters.

Influence of body water distribution on skin thickness: measurements using high-frequency ultrasound.

Although it is known that the skin acts as a water reservoir and participates in the fluid content of the whole body, no method has been established to quantify the fluid shifts in superficial tissue. The aim of this study was to investigate changes in dermal and subcutis thickness and echodensity at the forehead and lower leg by high-frequency (20 MHz) ultrasound under various physiological conditions influencing water balance. These parameters were measured in the skin of 20 healthy male volunteers at baseline and successively at 30 min after lying down, in a head-down position, after physical activity and after infusion of 10 mL kg-1 body weight of Ringer's solution. Dermal thickness at the forehead showed a significant increase from baseline to a horizontal position and a further increase in the head-down position. Physical activity did not lead to further changes, whereas after fluid infusion the dermal thickness also increased markedly. The echodensity showed inverse changes, with decreasing values. The thickness of the subcutis increased slightly from baseline to a lying position and decreased in the head-down position and after fluid infusion. At the lower leg, skin thickness decreased slightly in the head-down position with elevated legs, and increased after fluid infusion. Our results show that slight changes in the water distribution of the body influence the thickness and the echodensity of the dermis. Changes are more pronounced at the forehead than on the lower legs. Further, the fluid storage takes place mainly in the dermis and not in the subcutis. High-frequency ultrasound is able to quantify these effects and is a sensitive method for measuring fluid intake and balance during anaesthesia and therapy.

Comparative study of haemodynamic responses to active and passive posture inducing head-ward pooling of blood in man

To study the relative effects of passive head-down tilt and squatting on the cardiovascular dynamics in man. A pre-test/post-test study. Physiology Research Laboratories in the Schools of Medicine at Addis Ababa University and the University of Dundee, UK. Ten normal healthy subjects aged nineteen to twenty two years. Cardiovascular variables measured in Passive body tilt and squatting. Similar responses in forearm blood flow, arterial blood pressure, peripheral vascular resistance, and pulse rate observed in both active and passive postural changes. A change from the sitting to the squatting position resulted in marked changes of forearm blood flow (FBF=1.63ml/100 ml/min, p<0.05), mean arterial blood pressure (BP=9mmHg, p<0.05), mean forearm vascular resistance (PVR=-10 PRU, p<0.05) and mean pulse rate (PR =-5 beats/min, p>0.05). The corresponding changes in the head-down position were: FBF=2.37ml/100 ml/min, p<0.05; BP=11.0 mmHg, p<0.05; VR=-12.85 PRU, p<0.05; PR=-10 beats/min, p>0.05). These results suggest that the movement of blood towards the head is only slightly more marked in the head-down tilt than in the squatting position. The changes in flow and arterial blood pressure are similarly correlated (r=0.6291 in squatting and r=0.553 in 30 degrees head-down tilt). In both positions, blood moves to the thorax, neck and the head thus traversing the same baroreflex regions. This means that changes in cardiovascular variables in the two positions are detected by the same receptors signalling information to integrating centres via the same afferent pathways. Squatting and head-down tilt can, therefore, be used alternately to counteract orthostatic dizziness and to assess the significance of cardiovascular autonomic neuropathy in patients with disease conditions like diabetes mellitus.

Does patient position during liver surgery influence the risk of venous air embolism?

Background: It is generally believed that positioning of the patient in a head-down tilt (Trendelenberg position) decreases the likelihood of a venous air embolism during liver resection. Methods: The physiological effect of variation in horizontal attitude on central and hepatic venous pressure was measured in 10 patients during liver surgery. Hemodynamic indices were recorded with the operating table in the horizontal, 20 degrees head-up and 20 degrees head-down positions. Results: There was no demonstrable pressure gradient between the hepatic and central venous levels in any of the positions. The absolute pressures did, however, vary in a predictable way, being highest in the head-down and lowest during head-up tilt. However, on no occasion was a negative intraluminal pressure recorded. Conclusion: The effect on venous pressures caused by the change in patient positioning alone during liver surgery does not affect the risk of venous air embolism.

Der Einfluss von Operationslagerungen und Spinalanästhesie auf die Lungenfunktion

Various surgical positions, e.g., lithotomy, prone, or head-down positions influence respiratory mechanics. The aim of the present paper was to investigate whether particular surgical positions (lithotomy, lithotomy with head-down tilt, prone, prone with a roller placed under the abdomen) as well as spinal anaesthesia in lithotomy position impair the pulmonary function to a greater extent than supine position and whether they have to be considered as increasing the perioperative risk in elderly patients and patients with ventilatory disorders. In two separate experimental series, we examined a) the influence of the surgical positions on the pulmonary function in 45 subjects (25 without and 20 with ventilatory disorders) and b) the effects of spinal anaesthesia in 25 urologic patients (9 without and 16 with ventilatory disorders). Static and dynamic lung function parameters were determined. Under spinal anaesthesia, the arterial O2 saturation and the end-expiratory partial pressure of CO2 were measured additionally. The most pronounced lung function decrease occurred with the transition from seated to supine position. Lithotomy and prone positions impaired the respiratory function only slightly. In elderly persons and in patients with ventilatory disorders, the spirometric changes tended to be stronger than in young persons, but were not considered to increase the perioperative pulmonary risk. A combination of lithotomy position and spinal anaesthesia did likewise not remarkably impair the respiratory function. Lithotomy and prone positions as well as spinal anaesthesia are not considered to be an additional risk factor for pulmonary function.

Characterisation of gravity-induced facial skin oedema using biophysical measurement techniques.

In humans, the microgravity environment can be expected to induce swelling of facial tissues and shrinking of the tissues in the lower limbs, together with a loss in body weight. To evaluate fluid shifts in skin, the head-down bed-rest model was used. The aim of the present study was to evaluate the appearance of facial oedema in subjects undergoing anti-orthostatic bed-rest at an angle of -10 degrees. The forehead of each of four subjects was measured before and after 1, 10 and 24 h in this head-down tilt position. At these time points, interstitial fluid migration and facial oedema were assessed using a high resolution B-scan ultrasound and a device for measuring the skin's mechanical properties. The results obtained showed a progressive increase in dermal thickness and initial stress, and a reduction in stiffness and elasticity of the skin during the study period. This preliminary study has demonstrated the feasibility of the method in measuring fluid displacement and retention in the skin. Furthermore, it highlights the influence of fluids on the mechanical behaviour of the skin. These techniques could be used for studying the redistribution of liquid masses during periods spent in space.

Heart displacement during off-pump CABG: how well is it tolerated?

Background. Heart displacement during off-pump coronary artery bypass grafting (CABG) is necessary to expose the anastomosic sites. We analyzed the hemodynamic changes in relation to the grafted arteries. Methods. The relationship between surgical exposure and hemodynamic management was assessed in 150 consecutive patients undergoing off-pump CABG utilizing the Octopus Tissue Stabilization System (Medtronic, Minneapolis, MN). Results. Surgical exposure by anterolateral thoracotomy showed no significant hemodynamic changes. Through sternotomy, stroke volume was significantly reduced by dislocation at all target sites: by 6% at the left anterior descending artery (LAD), 25% at the diagonal branch artery (D), 14% at the right coronary artery (RCA), and 21% at the obtuse marginal artery (OM). The application of head-down positioning (LAD, 56%; D, 74%; RCA, 90%; OM, 96%) increased not only surgical exposure but also preload, producing correction of ventricular filling pressures and output. In a minority of cases, dopamine (3 to 5 μg · kg −1 · min −1) was added to maintain baseline hemodynamic values (LAD, 5%; D, 15%; RCA, 7%; OM, 28%). Conclusions. Revascularization during anterolateral thoracotomy was uneventful. The sternotomy approach with heart displacement induced right heart compression. Mainly fluid redistribution was sufficient to correct cardiac output. Once stabilized, systemic circulation remained unchanged during revascularization.

A new approach to stage 3 macular holes

Purpose The purpose of this article is to demonstrate the feasibility of a surgical approach that might be possible in an office setting for idiopathic stage 3 macular holes. The posterior hyaloid of the vitreous and perihole tissue is enzymatically manipulated to create an atraumatic posterior vitreous separation and may stimulate cell proliferation to close macular holes. Design Prospective noncomparative interventional case series. Participants Nine eyes of eight patients with idiopathic stage 3 macular holes were treated. Methods The patients were treated with an injection of 0.4 IU of autologous plasmin enzyme into the midvitreous cavity and lavage of the vitreous cavity with an infusion light pipe and vitreous cutter followed by filling 70% to 80% of the vitreous cavity with 14% C3F8 and head-down positioning. Main outcome measures Posterior vitreous detachment, macular hole closure, and vision improvement. Results Eight of nine eyes showed a spontaneous posterior vitreous detachment. One eye required minimal suction of less than 50 mmHg to elevate the posterior hyaloid off the retinal surface. Eyes were followed for a minimum of 6 months. All holes closed, and there was an average visual acuity improvement of four lines. The average surgical time for this procedure was 20 minutes. Conclusions Autologous plasmin enzyme–assisted vitreous surgery techniques can reduce operative time, expense, and patient inconvenience while maintaining excellent surgical results, which may allow office-based vitreous surgery for idiopathic stage 3 macular holes.