股静脉测压法和膀胱测压法在危重患者腹内压监测中的比较

目的：比较股静脉测压法和膀胱测压法在危重患者腹内压（IAP）监测中的应用价值.方法：对2013年1-6月住院治疗的20例ICU重症患者,分别使用两种测压方法进行IAP监测,均每8 h 1次,连续测定3 d,每次随机选择两种方法的测量顺序,共测量720次,比较两种测压法在读数精准性、测压数值、操作时间、并发症和医护人员满意度等方面的异同.结果：股静脉测压法所测压力数值与膀胱测压法相近[（14.14±4.33）mmHg比（12.91±4.75）mmHg,P〉0.05];但是股静脉测压法的操作时间[（57.94±19.00）s]较膀胱测压法更短[（112.49±27.07）s,P〈0.05];股静脉测压法读数精准率（84.44%）较膀胱测压法（49.44%）高（P〈0.01）,操作并发症低至1.1%（4例次）,远低于膀胱测压法的5.3%（19例次,P〈0.05）;医护人员满意度达（3.90±0.26）分,优于膀胱测压法[（2.48±0.19）分,P〈0.01].结论：相对于膀胱测压法而言,股静脉测压法具有测压值相似、操作时间短、读数精准度高、操作并发症少、接纳度高等优点,值得在危重患者IAP监测中推广.     

Arterial pulse pressure

A WELL IDENTIFIED RISK FACTOR: Other than systolic, diastolic and mean pressure, arterial pulse pressure (or differential pressure) is an independent factor of cardiovascular and notably coronary risk. The role of this factor is now clearly quantified in untreated hypertensive patients, but also in treated apparently controlled patients, and in patients with normal blood pressure. Demonstration of the deleterious role of an increase in pulse pressure was also made in populations at high risk of events such as heart failure, post-infarction or in hemodialyzed patients. FROM A THERAPEUTIC POINT OF VIEW: Antihypertensive treatments have inconstant efficacy on pulse pressure and new therapeutic routes appear promising. However, in the absence of available proof that a strategy axed on the decrease in pulse pressure improves cardiovascular prognosis, current recommendations do not yet include pulse pressure levels in therapeutic strategies. AN EFFICIENT MARKER: Whilst awaiting further data, the measurement of pulse pressure, because of its pertinence and simplicity, provides the practitioner with one of the most efficient markers for screening persons at high risk of cardiovascular and particularly coronary risk.     

Monitoring central venous pressure,arterial pressure and pulmonary wedge pressure

Direct measurement of vascular pressure requires the insertion of a cannula into a vessel. The cannula is connected to saline filled tubing attached to a transducer apparatus for measurement and display of the vascular pressure waveform. The transducer apparatus is essentially the same for all intravascular pressure measurement. Direct measurement of arterial pressure is indicated where rapid fluctuations in pressure are anticipated, where accurate control of pressure is required, and for repeated sampling of blood gases. Central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) measurement indicate the preload of the right and left side of the heart respectively; and when considered in conjunction with other physiological measures can give a guide to the volume status of a patient. Trends in response to therapeutic intervention should be used rather than any individual value being used in isolation. Direct measurement of vascular pressure involves invasive procedures which carry a risk of complications relating to insertion of the cannulae and duration of use.     

The role of the pulsatile pressure variations in intracranial pressure monitoring

Summary The magnitude of the pulsatile intracranial pressure variations (CSF pulse pressure) is determined by the elastance of the craniospinal system and by the magnitude of the pulsatile variations in cerebral blood volume (CBV). The pulsatile change in CBV is, among other factors, determined by the compliance of the cerebral vascular bed which, in its turn, is dependent on the cerebral vasomotor tone. This concept has led the authors to devise a method for the assessment of both the elastance and the state of the cerebral vasomotor tone based on the relationship between CSF pulse pressure and intracranial pressure. This relationship was found to be of a linear nature both in clinical patients and in experimental animals. A significant, positive correlation was found between the slope of this relationship and the value of the craniospinal volume-pressure relationship: the elastance coefficient. During elevation of the intracranial pressure a breakpoint was observed in the relationship between CSF pulse pressure and the intracranial pressure above which the pulse pressure increased more rapidly. The elastance remained constant above this breakpoint. The same phenomenon was observed during plateau waves in clinical patients. Induced changes in systemic arterial pressure produced opposite effects on CSF pulse pressure and elastance coefficient. In these cases the discrepancy between pulse pressure and elastance was attributed to the pulsatile changes in CBV and this could be verified by means of electromagnetic flowmetry. The advantage of this method is that all the information is contained within the intracranial pressure signal itself, from which it can be extracted by simple means without the use of invasive tests.     

Estimation of critical closing pressure and cerebral perfusion pressure using transcranial Doppler

Editor—We read with interest the article by Sherman andcolleagues.¹ We would like to comment on the methods used toestimate critical closing pressure and cerebral perfusion pressure. The formula used to calculate critical closing pressure in thisarticle omits the influence of cerebrovascular wall tension.It actually equates critical closing pressure with intracranialpressure. As shown earlier, critical closing pressure consistsnot only of intracranial pressure but also of a factor representingarterial vascular wall tension.² Moreover, the method used tocalculate critical closing pressure can     

Measurement of the footsole pressure distribution of normal subjects by pressure sensitive films

A simple method measuring the pressure on the footsole was described using "Prescale", pressure sensitive films. Prescale consists of two films, one coated with microcapsules which contain a color-producing agent and rupture when a pressure is applied, and the other coated with a color-developing agent. Then, when a pressure is applied on the former film, the latter one display a color of various density corresponding to the pressure applied. Distribution of the pressure on the footsole was studied in normal subjects by this method. Pressure distribution in each subject was compared with his foot structure examined radiologically. And the clinical implications and indication of this method were discussed.     

Central venous pressure and pulmonary artery pressure monitoring

Central venous pressure and pulmonary artery pressure are used as measures of cardiovascular filling. While pressure–volume relationships are not constant, trends in central venous pressure give an indication of increasing or decreasing right ventricular filling, while pulmonary artery pressure gives an indirect indication of left ventricular filling pressure. Cardiac output can be estimated by use of thermodilution.     

Selectivity of oxymetazoline for urethral pressure vs blood pressure in the anaesthetized female rabbit

OBJECTIVE: The aim of this study was to test alpha-adrenergic reference agonists for tissue selectivity in the urethra and to pharmacologically characterize the functional alpha-adrenoceptor type of the female rabbit urethra in vivo. MATERIAL AND METHODS: The effect of alpha-adrenergic agonists and antagonists on the urethral pressure was compared with that on blood pressure and heart rate measured simultaneously in the anaesthetized female rabbit. RESULTS: Oxymetazoline, NS-49, phenylephrine and phenylpropanolamine enhanced the urethral pressure in a dose-dependent manner. Phenylephrine and phenylpropanolamine also enhanced the blood pressure with significantly lower ED50 (dose that gives half of the maximal enhancing effect) values than for the urethral pressure. This was in contrast to oxymetazoline and NS-49. The ED50 values for oxymetazoline on urethral pressure, and systolic and diastolic blood pressure were 0.00067, 0.0030 and 0.0020 mg/kg, respectively. The ED50 values for NS-49 on urethral pressure, and systolic and diastolic blood pressure were 0.019, 0.21 and 0.18 mg/kg, respectively. Clonidine and UK 14,304 had no effect on urethral or blood pressure. The oxymetazoline-evoked increase in urethral pressure was inhibited by WB-4101 with an ID50 (dose that gives half of the inhibitory effect) significantly lower than that for rauwolscine. CONCLUSIONS: The results suggest that in the female rabbit in vivo activation of alpha1-adrenoceptors increased the urethral pressure. Phenylephrine and phenylpropanolamine, in contrast to oxymetazoline and NS-49, selectively enhanced blood pressure as compared with urethral pressure. Provided that the present results also have validity in humans, it would seem possible to develop urethra-selective drugs for treatment of stress incontinence with few or no cardiovascular side-effects.     

Associations between intracranial pressure, intraocular pressure and mean arterial pressure in patients with traumatic and non-traumatic brain injuries

Introduction

Anatomical proximity of the eye and the intracranial space is a fact but the existence of physiological and pathophysiological relationships between them is elusive. The objective of this study was to explore anatomical and pathophysiological interactions between the eye and the intracranial space and to assess clinical utility of intraocular pressure measurement in estimation of intracranial pressure in patients with brain injuries and to discover how haemodynamic instability could influence these interactions. Controversy surrounds the recent literature concerning this problem and the consensus has not been achieved.

Materials and methods

We evaluated the correlation between intracranial pressure and intraocular pressure, intracranial pressure and mean arterial pressure, intraocular pressure and mean arterial pressure in 40 patients with brain injuries initially comatose, admitted to our hospital. All patients required the intracranial pressure monitoring on clinical grounds. Simultaneous recordings of intracranial pressure, intraocular pressure and mean arterial pressure were performed.

Results

We calculated both the linear correlation coefficient and the Spearman rank-order correlation coefficient for all three relations. We found significant correlation between intraocular pressure and mean arterial pressure in 63% of the tested population. When the power of the test was increased, by considering only patients with 11 or more observations, this ratio increased to 76%. However, the correlation between intraocular pressure and intracranial pressure, as well as, between intracranial pressure and mean arterial pressure was not significant.

Conclusions

There is no anatomical and pathophysiological basis for the statement that intraocular pressure can be used as an indirect estimator of intracranial pressure.     

腹内高压对门静脉压、中心静脉压影响的实验研究

目的研究腹内压升高对大鼠中心静脉压和门静脉压的影响。方法将20只成年雄性SD大鼠分别通过颈静脉插管、穿刺门静脉主干法来测定中心静脉压和门静脉压,运用氮气气腹法制作大鼠腹内高压动物模型。建立气腹后分别在0、5、10、15、20、25、30、35、40、45mmHg压力值下测得中心静脉压和门静脉压。结果中心静脉压和腹内压之间的直线回归方程为Y=2.824+0.045X,相关系数r=0.984(P<0.01);门静脉压和腹内压之间的直线回归方程为Y=8.887+0.939X,相关系数r=0.998(P<0.01)。结论腹内压与中心静脉压和门静脉压有很好的相关性,可以根据腹内压监测中心静脉压和门静脉压的变化。     

联合应用压力手套及压力垫治疗手背烧伤后瘢痕的疗效观察

目的：观察联合应用压力手套和压力垫对手背侧烧伤后瘢痕增生的预防和治疗作用。方法：对58只烧伤后愈合患手分别采用单纯压力手套和联合应用定制压力手套及压力垫进行干预,用Sawada评分方法对两组治疗前、治疗3个月及治疗6个月手背瘢痕色泽、厚度、硬度及敏感度进行定量评分,比较其治疗差异。结果：联合治疗组在治疗6个月后效果优于单纯治疗组,具有统计学差异（P〈0．05）。结论：联合治疗组较单纯治疗组更有效控制瘢痕增生及因瘢痕增生引起的继发畸形,外观改善明显。     

Intracranial pressure

Background: The effects of pneumoperitoneum on intracranial pressure (ICP) have received relatively little attention. This study was undertaken to investigate the changes in ICP occurring as a result of increased intraabdominal pressure (IAP) and positioning in animals with normal and elevated ICP. Method: Five pigs (average weight 60 lb) were studied. A subarachnoid screw was placed for ICP monitoring. End tidal CO₂ was monitored. Ventilation was performed to keep PCO₂ between 30 and 50 mmHg. Measurements of arterial blood gases, mean arterial blood pressure, and ICP were recorded at four different levels of intraabdominal pressure (IAP 0, 8, 16, and 24 mmHg), both in the supine and Trendelenburg positions. A Foley catheter was introduced into the subarachnoid space to elevate the intracranial pressure, and the same measurements were performed. Results: There was a significant and linear increase in ICP with increased IAP and Trendelenburg position. The combination of increased IAP of 16 mmHg and Trendelenburg position increased ICP 150% over control levels. Conclusions: Patient positioning and level of IAP should be taken into consideration when performing laparoscopy on patients with head trauma, cerebral aneurysms, and other conditions associated with increased ICP. Received: 19 March 1996/Accepted: 24 May 1996     

The vaginal pressure profile

AIMS: To describe the vaginal pressure profile in asymptomatic nulliparous women. METHODS: Fourteen nulliparous women without symptoms of anal or urinary incontinence were studied with vaginal manometry. A rapid pull-through technique utilized a four-channel water-perfused catheter on a motor-driven puller to create a pressure profile for each subject. The profiles were measured with the subject at rest and during a sustained contraction of the levator ani muscle. The individual subject's pressure profiles were averaged to create a composite profile at rest and during squeeze. RESULTS: The vaginal pressure profile at rest and during squeeze contains three pressure zones: proximal, mid, and distal. The pressure is highest in the mid pressure zone and was labeled as the vaginal high-pressure zone. In the vaginal high-pressure zone, the maximum pressure during squeeze is significantly higher than the maximum pressure at rest (P < 0.05). The length of the high-pressure zone is longer during squeeze as compared to rest (P < 0.05). The maximum pressures exhibit circumferential asymmetry with the pressures in anterior and posterior directions being significantly higher than those in the lateral directions (P < 0.05). CONCLUSIONS: The vaginal pressure profile is more complex than previously described. Understanding of the vaginal pressure profile is crucial when employing vaginal manometry to assess pelvic floor muscle strength or as a surrogate for intra-abdominal pressure.     

Lumbar cerebrospinal fluid pressure waves versus intracranial pressure waves in idiopathic normal pressure hydrocephalus

The aim of this study was to explore how the lumbar cerebrospinal fluid pressure (CSFP) waves recorded during lumbar infusion compared with the intracranial pressure (ICP) waves recorded, either during lumbar infusion or during long-term, overnight monitoring. For this purpose, we assessed 27 simultaneous lumbar CSFP/ICP recordings made during lumbar infusion and 27 long-term, overnight ICP recordings in 27 consecutive idiopathic normal pressure hydrocephalus (iNPH) patients. Pressure waves during lumbar infusion were explored by computing pulse pressure amplitude and mean single wave pressure of every corresponding CSFP/ICP wave pair; among our 27 lumbar CSFP/ICP recordings a total of 35,532 CSFP/ICP wave pairs were available for analysis. We as well computed mean values of pulse pressure amplitude (i.e. mean CSFP wave amplitude or mean ICP wave amplitude) and mean values of mean single wave pressure (i.e. mean CSFP or mean ICP) during consecutive 6-s time windows, as well as average values for the individual recordings. During lumbar infusion, the cerebrospinal fluid pulse pressure amplitudes were about 2 mmHg smaller than the corresponding intracranial pulse pressure amplitudes. The mean CSFP wave amplitudes recorded during lumbar infusion correlated significantly with the mean ICP wave amplitudes recorded either during lumbar infusion or during long-term, overnight ICP monitoring. In 21 of 27 lumbar infusion tests (78%), the presence of elevated lumbar mean CSFP waves was related to presence of elevated mean ICP wave amplitudes during long-term, overnight ICP monitoring. Hence, the lumbar cerebrospinal fluid pulse pressure amplitudes recorded during lumbar infusion could be used to predict the intracranial pulse pressure amplitudes recorded during long-term, overnight ICP monitoring.     

Influence of semi-recumbent position on intra-abdominal pressure as measured by bladder pressure

BACKGROUND: Intra-abdominal pressure (IAP) obtained by bladder pressure measurement is used to detect impending abdominal compartment syndrome (ACS), but, while it is recommended to use a supine position, the literature describes IAP measurement in varying positions. This study evaluated the impact of body position at differing head-of-bed (HOB) elevations on bladder pressure when planned to be used as a surrogate IAP measurement. MATERIALS AND METHODS: Forty-five trauma patients admitted to a surgical intensive care unit underwent bladder pressure measurements at 0, 15, 30, 45 degrees HOB position and 30 degrees HOB position plus 15 degrees of reverse Trendelenburg tilt; these measurements were performed in counterbalanced fashion and assessed by built-in angle indicators on the bed rails of each bed. Study participants were connected to an IAP monitoring kit via their indwelling Foley catheter. RESULTS: A total of 675 bladder pressure measurements were obtained with 135 measurements at each of five HOB elevations (0 degrees , 15 degrees , 30 degrees , 45 degrees , 30 degrees +15 degrees tilt). Statistically significant differences occurred between all HOB elevations. Statistically significance differences also occurred at different BMI statuses. CONCLUSIONS: Elevating HOB significantly increases bladder pressure measurement. Bladder pressure measurements in nonsupine positions may not provide valid interpretation for IAP, and more so in cases of increased body mass index.     

Measuring tissue perfusion during pressure relief maneuvers: insights into preventing pressure ulcers

BACKGROUND/OBJECTIVE: To study the effect on tissue perfusion of relieving interface pressure using standard wheelchair pushups compared with a mechanical automated dynamic pressure relief system. DESIGN: Repeated measures in 2 protocols on 3 groups of subjects. PARTICIPANTS: Twenty individuals with motor-complete paraplegia below T4, 20 with motor-complete tetraplegia, and 20 able-bodied subjects. METHODS: Two 1-hour sitting protocols: dynamic protocol, sitting configuration alternated every 10 minutes between a normal sitting configuration and an off-loading configuration; wheelchair pushup protocol, normal sitting configuration with standard wheelchair pushup once every 20 minutes. MAIN OUTCOME MEASURES: Transcutaneous partial pressures of oxygen and carbon dioxide measured from buttock overlying the ischial tuberosity and interface pressure measured at the seat back and buttocks. Perfusion deterioration and recovery times were calculated during changes in interface pressures. RESULTS: In the off-loading configuration, concentrated interface pressure during the normal sitting configuration was significantly diminished, and tissue perfusion was significantly improved. Wheelchair pushups showed complete relief of interface pressure but incomplete recovery of tissue perfusion. CONCLUSIONS: Interface pressure analysis does not provide complete information about the effectiveness of pressure relief maneuvers. Measures of tissue perfusion may help establish more effective strategies. Relief achieved by standard wheelchair pushups may not be sufficient to recover tissue perfusion compromised during sitting; alternate maneuvers may be necessary. The dynamic seating system provided effective pressure relief with sustained reduction in interface pressure adequate for complete recovery of tissue perfusion. Differences in perfusion recovery times between subjects with spinal cord injury (SCI) and controls raise questions about the importance of changes in vascular responses to pressure after SCI.     

Determinants of regional intramyocardial pressure

Regional myocardial flow becomes dependent on intramyocardial pressure after maximal coronary vasodilatation occurs. Thus, knowledge of the determinants of intramyocardial pressure magnitude and distribution across the ventricular wall is important. If the ventricle is represented by concentric thin-wall spheres, the magnitude and distribution of intramyocardial pressure is dependent upon (a) the spherical geometry of the ventricle and (b) the distribution of circumferential wall stress. Theoretical solutions obtained on a computer for various geometries and wall stress distributions predict intramyocardial pressure to be less than intraventricular cavitary pressure and decrease from endocardium to epicardium unless subendocardial compressive stress is present. When there is subendocardial compression intramyocardial pressure exceeds intracavitary pressure over most of the ventricular wall, and smaller ventricular cavity volumes and hypertrophy increase the intramyocardial pressure further. Hypertrophied, contracted, or near-empty ventricles such as occur during hypovolemic shock and cardiopulmonary bypass are, therefore, more subject to myocardial ischemic injury—particularly in the subendocardial and middle myocardial layers—than are normal beating ventricles, because of higher intramyocardial pressures which may impede coronary flow.     

High pressure and anesthesia: pressure stimulates or inhibits bacterial bioluminescence depending upon temperature

Although high pressure is often viewed as a nonspecific stimulus counteracting anesthesia, pressure can either excite or inhibit biological activity depending on the temperature at application. Temperature and pressure are two independent variables that determine equilibrium quantity, e.g., the state of organisms in terms of activity and anesthesia depth. We used the light intensity of luminous bacteria (Vibrio fischeri) as an activity parameter, and studied the effects of pressure and anesthetics on the bacteria's light intensity at various temperatures. The light intensity was greatest at about 30 degrees C at ambient pressure. When the system was pressurized up to 204 atm, the temperature for maximum light intensity was shifted to higher temperatures. Above the optimal temperature for the maximal light intensity, high pressure increased the light intensity. Below the optimal temperature, pressure decreased light intensity. Pressure only shifts the reaction equilibrium to the lower volume state (Le Chatelier's principle). When the volume of the excited state is larger than the resting state, high pressure inhibits excitation, and vice versa. Halothane 0.008 atm and isoflurane 0.021 atm inhibited the light intensity both above and below the optimal temperature. When pressurized, the light intensity increased in the high temperature range but decreased in the low temperature range, as in the control. Thus, high pressure seemingly potentiated the anesthetic action at low temperatures. When the ratio of the light intensity in bacteria exposed to anesthesia and those not exposed to anesthesia was plotted against the pressure, however, the value approached unity in proportion to the pressure increase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Treatment of normal pressure hydrocephalus with low versus medium pressure cerebrospinal fluid shunts

In a retrospective study, 39 patients received a low pressure (20 to 50 mm H2O) shunt and 33 received a medium pressure (55 to 85 mm H2O) shunt for the treatment of normal pressure hydrocephalus (NPH). Pre- and postoperative computed tomographic scans were obtained in 32 patients, permitting us to determine the influence of shunt pressure on ventricular size. A reduction in 3rd ventricle width was found to correlate with clinical improvement and was observed more frequently after the placement of a low pressure shunt than after the placement of a medium pressure shunt. When results were evaluated in patients who did not have advanced NPH or develop postoperative complications, gait was markedly improved in 60% of those receiving a low pressure shunt as opposed to 23% of those receiving a medium pressure shunt (P less than 0.05).     

Relationship between intracranial pressure and critical closing pressure in patients with neurotrauma

BACKGROUND: The driving pressure gradient for cerebral perfusion is the difference between mean arterial pressure (MAP) and critical closing pressure (CCP = zero flow pressure). Therefore, determination of the difference between MAP and CCP should provide an appropriate monitoring of the effective cerebral perfusion pressure (CPP(eff)). Based on this concept, the authors compared conventional measurements of cerebral perfusion pressure by MAP and intracranial pressure (CPP(ICP)) with CPP(eff). METHODS: Simultaneous synchronized recordings of pressure waveforms of the radial artery and blood flow velocities of the middle cerebral artery were performed in 70 head trauma patients. CCP was calculated from pressure-flow velocity plots by linear extrapolation to zero flow. RESULTS: Intracranial pressure measured by intraventricular probes and CCP ranged from 3 to 71 and 4 to 70 mmHg, respectively. Linear correlation between ICP and CCP was r = 0.91. CPP(ICP) was 77 +/- 20 mmHg and did not differ from CPP(eff); linear correlation was r = 0.92. However, limits of agreement were only +/- 16.2 mmHg. Therefore, in 51.4% of the patients, CPP(ICP) overestimated CPP(eff) by 19.8 mmHg at most. CONCLUSION: Assuming that CPP(eff) (MAP - CCP) takes into account more determinants of cerebral downstream pressure, in individual cases, the actual gold standard of CPP determination (MAP - ICP) might overestimate the CPP(eff) of therapeutic significance.