The haemodynamic response to submaximal exercise during isovolaemic haemodialysis.

INTRODUCTION: Exercise during haemodialysis has potential benefits but may compromise cardiovascular stability. We studied its acute effects on relative blood volume (RBV) and other haemodynamic parameters. METHODS: Two groups of 10 patients were exercised submaximally using a stationary cycle during isovolaemic dialysis whilst RBV was monitored continuously. In study 1, patients exercised for two 10 min periods separated by 10 min rest. Cardiac output (CO), peripheral vascular resistance (PVR), central blood volume (CBV) and stroke volume were measured using ultrasound dilution immediately before and after each exercise session. In study 2, haemoglobin, serum total protein and albumin levels were measured before and immediately after the exercise session and at the nadir of the RBV trace. RESULTS: RBV fell immediately on exercise initiation, the maximum reduction being 2.0+/-1.1% (after 5.9+/-1.4 min of exercise 1: P<0.001) and 2.0+/-1.2% (after 4.7+/-2.3 min of exercise 2: P<0.001). CO increased significantly after both periods of exercise (4.5+/-0.96 and 5.1+/-1.1 to 7.2+/-2.1 and 7.9+/-2.4 l/min, P<0.001 in both). Stroke volume increased significantly and PVR fell significantly during exercise. CBV increased in absolute terms but fell as a proportion of CO. Mean haemoglobin level at the RBV nadir was significantly higher than baseline (12.3+/-1.8 vs 11.8+/-1.7 g/dl: P<0.05: mean change 4.4+/-2.3%), as was mean total protein concentration (66.0+/-6.9 vs 62.0+/-8.1 g/l: P = 0.001: mean change 6.8+/-5.9%) and mean serum albumin concentration (36.0+/-3.9 vs 34.1+/-3.9 g/l: P<0.001: mean change 5.8+/-3.5%). CONCLUSION: The haemodynamic response to exercise during haemodialysis is comparable with that in normal individuals. The rapid reduction in RBV on exercise occurs in spite of a significant increase in CO, mainly as a consequence of fluid shifts from the microvasculature to the interstitium.     

Specific effect of the infusion of glucose on blood volume during haemodialysis.

BACKGROUND: Intradialytic morbid events such as hypotension and cramps during haemodialysis are generally treated by infusion of iso- or hypertonic solutions. However, differences may exist between solutions with respect to plasma refilling and vascular reactivity. METHODS: We compared the effect of no infusion (NI) with isovolumetric infusion of isotonic saline 0.9% (IS), saline 3% (HS), isotonic glucose 5% (IG), glucose 20% (HG) and mannitol 20% (HM), in six patients during the first hour of six standardized haemodialysis sessions with ultrafiltration. Relative blood volume was monitored continuously by measurement of the intravascular amount of protein. Blood pressure was measured by an oscillometric method, while cardiac output was measured by a thoracic impedance technique. RESULTS: At baseline, no differences in serum urea, sodium, potassium, glucose and osmolarity were found between the various infusion experiments. The maximum increase in relative blood volume directly after infusion was significantly greater with HG (5.1+/-0.7%) than with all other infusions (P<0.05). Stroke volume increased (21.0+/-19.2%, P<0.05) and total peripheral resistance decreased significantly (15.4+/-16.4%, P<0.05) after HG infusions. CONCLUSIONS: Infusion of hypertonic glucose during dialysis results in a greater increase in relative blood volume (RBV) than equal volumes of other solutions. As mannitol has the same osmolarity, molecule mass and charge, the greater increase in RBV following hypertonic glucose appears to be a specific effect, possibly related to a decline in vascular tone. It is therefore uncertain whether the observed increase in plasma volume during hypertonic glucose infusions will be of clinical benefit.     

Variability of relative blood volume during haemodialysis.

BACKGROUND: A decrease in blood volume is thought to play a role in dialysis-related hypotension. Changes in relative blood volume (RBV) can be assessed by means of continuous haematocrit measurement. We studied the variability of RBV changes, and the relation between RBV and ultrafiltration volume (UV), blood pressure, heart rate, and inferior caval vein (ICV) diameter. METHODS: In 10 patients on chronic haemodialysis, RBV measurement was performed during a total of one hundred 4-h haemodialysis sessions. Blood pressure and heart rate were measured at 5-min intervals. ICV diameter was assessed at the start and at the end of dialysis using ultrasonography. RESULTS: The changes in RBV showed considerable inter-individual variability. The average change in RBV ranged from -0.5 to -8.2% at 60 min and from -3.7 to -14.5% at 240 min (coefficient of variation (CV) 0.66 and 0.35 respectively). Intra-individual variability was also high (CV at 60 min 0.93; CV at 240 min 0.33). Inter-individual as well as intra-individual variability showed only minor improvement when RBV was corrected for UV. We found a significant correlation between RBV and UV at 60 (r= -0.69; P<0.001) and at 240 min (r= -0.63; P<0.001). There was a significant correlation between RBV and heart rate (r= -0.39; P<0.001), but not between RBV or UV and blood pressure. The level of RBV reduction at which hypotension occurred was also highly variable. ICV diameter decreased from 10.3+/-1.7 mm/m(2) to 7.3+/-1. 5 mm/m(2). There was only a slight, although significant, correlation between ICV diameter and RBV (r= -0.23; P<0.05). The change in ICV-diameter showed a wide variation. CONCLUSIONS: RBV changes during haemodialysis showed a considerable intra- and inter-individual variability that could not be explained by differences in UV. No correlation was observed between UV or changes in RBV and either blood pressure or the incidence of hypotension. Heart rate, however, was significantly correlated with RBV. Moreover, IVC diameter was only poorly correlated with RBV, suggesting a redistribution of blood towards the central venous compartment. These data indicate that RBV monitoring is of limited use in the prevention of dialysis-related hypotension, and that the critical level of reduction in RBV at which hypotension occurs depends on cardiovascular defence mechanisms such as sympathetic drive.     

Haemodynamic effects of subarachnoid block in elderly patients

We have studied the haemodynamic effects of subarachnoid blockin elderly patients. Thirty patients were undergoing electivetransurethral surgery and 18 non-elective orthopaedic surgery,predominantly fractured neck of femur. Systolic arterial pressure(SAP) was measured by automated oscillotonometry, central venouspressure (CVP) by manometer and cardiac index (CI), stroke index(SI) and heart rate (HR) by transthoracic electrical bioimpedance.Systemic vascular resistance index (SVRI) was derived. SAP decreasedby more than 25% in 33 patients and SVRI showed similar decreases(P = 0.0001). CVP decreased (2.5 (SD 1.5) cm H₂O) in all patients.CI was unaffected because a decrease in SI in some patients(13 (19)%; P=0.01) was compensated for by an increase in HR(13 (13)%; P=0.01). Decreases in SAP of 25% were treated initiallywith colloid solution 8 ml kg^–1 which restored SAP in19 patients. CVP, SI and HR were all restored to baseline values,however, SVRI was decreased further (P<0.05). Fourteen patientsrequired additional treatment with metaraminol which restoredSVRI to baseline values. Patients with systolic hypertensionwere more likely to require treatment with metaraminol (P =0.04).     

The pressor response after laryngeal mask or cuffed oropharyngeal airway insertion

BACKGROUND: Since the cuffed oropharyngeal airway (COPA) has been suggested to cause less pharyngeal trauma than the laryngeal mask airway (LMA), we conducted a prospective, randomised study to compare haemodynamic changes after placing either the COPA or LMA in healthy anaesthetised adults. METHODS: After standard midazolam premedication (0.05 mg kg(-1) IV), general anaesthesia (IV propofol 2 mg kg(-1)) was induced in 60 ASA physical status I-II, 18-65-yr-old patients, who were randomly allocated to receive COPA (n=30) or LMA (n= 30) placement and then mechanically ventilated using a 60% nitrous oxide and 1% isoflurane in oxygen mixture (TV=8 ml kg(-1), RR=12 b.p.m., I/E=1/2). Haemodynamic variables were recorded 20 min after the midazolam premedication (baseline), and then every 1 min until 10 min after general anaesthesia induction. RESULTS: Nine patients of group COPA (30%) required chin lift, jaw thrust or head tilt to maintain adequate ventilation, while no problems were observed in the LMA group (P<0.0005); however, in no case did the designed extratracheal airway have to be removed due to unsuccessful mechanical ventilation, and no signs of gastric insufflation or regurgitation were reported. The maximum mean changes in haemodynamic variables were more marked after LMA placement (SAP: 12%+/-13%; DAP: 11%+/-18%; HR: 13%+/-16%) than COPA placement (SAP: -3%+/-18%; DAP: -5%+/-16%; HR: 4%+/-13%) (P<0.005, P<0.005, and P<0.01 for SAP, DAP and HR, respectively). Group LMA showed higher SAP and DAP values than group COPA only during the first 3 min after airway insertion. CONCLUSION: In healthy, anaesthetised patients, placing a cuffed oropharyngeal airway is associated with smaller cardiovascular changes after airway insertion compared with the laryngeal mask airway.     

腹膜透析患者的总外周阻力对血压与容量关系的影响

目的 研究腹膜透析（PD）患者中高血压与正常血压患者容量状态发生重叠的血流动力学机制。 方法 选取51例PD患者，采用生物电阻抗方法评估患者的细胞外液（ECW）、细胞内液(ICW)、总体水(TBW)水平，并通过身高标化后得出NECW。根据不同性别组NECW的平均水平定义为正常容量状态组（NV组，NECW≤平均水平）及高容量状态组（HV组，NECW＞平均水平）。再根据容量和血压将患者分成4组：正常血压合并正常容量组 （NT-NV)、正常血压合并高容量组(NT-HV)、高血压合并正常容量组(HT-NV)和高血压合并高容量组(HT-HV)。超声心动图观测患者的每博输出量(SV)、心输出量(CO)及总外周阻力(TPR)，并以体表面积校正，计算出相对应的指数SI、CI和TPRI。 结果 高容量状态组的ECW、ICW、TBW均明显高于正常容量组。HT-NV 组TPR、TPRI 水平明显高于NT-HV组[分别为(219.4±47.4) 比(168.8±54.6) Pa&#8226;s&#8226;cm-3；(148.8±29.5)比(99.1±36.2) Pa&#8226;s&#8226;cm-1，均P < 0.01]，同时也显著高于其他2组（P < 0.05）。而NT-HV组SV、SI、CO及CI与NT-NV组、HT-NV组差异无统计学意义。但HT-NV组SV及CO明显低于HT-HV组[SV：(58.3±8.4) ml比(75.6±21.9) ml；CO：(4.03±0.70) ml/m2比(5.18±1.46) ml/m2；均P < 0.05]。 结论 PD患者中高血压与正常血压患者容量状况的重叠与TPR 及 TPRI的差异有关。正常血压合并高容量状态的患者存在低TPR和TPRI，而高血压合并正常容量状态的患者则存在高TPR和TPRI。     

Effects of haemoglobin normalization on quality of life and cardiovascular parameters in end-stage renal failure.

BACKGROUND: The optimal haemoglobin concentration ([Hb]) for patients with end-stage renal failure is uncertain. In particular, it is unclear whether Hb normalization may be an advantage to such patients who are otherwise well. METHODS: A prospective, randomized, double-blind cross-over study was completed in 14 haemodialysis patients (12 male) aged between 23 and 65 years over a period of 18 months, using a variety of measures to examine the effect of epoetin at target [Hb] of 10 g/dl ([Hb](10)) and 14 g/dl ([Hb](14)). Patients were randomized to maintain one or other of the target levels for 6 weeks before being crossed over to the alternative [Hb]. Baseline data (mean [Hb]: 8.5+/-0.2 g/dl) were also included selectively. Six patients were known to be hypertensive. Comparisons were made between 24-h ambulatory blood pressure levels (ABP), echocardiographic findings and estimates of blood volume (BV), plasma volume (PV) and Hb mass. Quality of life estimates were obtained using the Sickness Impact Profile (SIP), and epoetin dosage requirements at target [Hb] were assessed. RESULTS: Daytime and nocturnal ABP (systolic and diastolic) were not different at the respective target [Hb], although nocturnal diastolic levels were higher compared with baseline (73+/-4 mmHg) at both [Hb](10) (83+/-3, P:<0.01) and [Hb](14) (81+/-6, P:<0.05). Significant reductions in cardiac output (5.2+/-0.3 vs 6.6+/-0.5 l/min, P:<0.01) and left ventricular end-diastolic diameter (4.8+/-0.2 vs 5.2+/-0.2 cm, P:<0. 001) were found at [Hb](14) compared with [Hb](10). Left ventricular mass index was correlated with both PV (P:<0.001) and BV (P:<0.01), but not with Hb mass. The PV decreased as the [Hb] rose (P:<0.001) but BV remained unchanged. Quality of life was significantly improved at [Hb](14) compared with [Hb](10) for both total score (6. 5+/-1.7 vs 13.4+/-3.0, P:=0.01) and psychosocial dimension score (5. 4+/-1.9 vs 15.4+/-4.0, P:<0.01). The maintenance weekly dose of epoetin required was 80% higher at [Hb](14) compared with [Hb](10) (P:<0.001). CONCLUSION: These data suggest there may be a significant haemodynamic and symptomatic advantage in maintaining a physiological [Hb] in haemodialysis patients. Although untoward effects were not identified in this study at [Hb](14), a substantially higher dose of epoetin is required to maintain this level.     

Hypotension during hemodialysis results from an impairment of arteriolar tone and left ventricular function

AIMS: Hypotensive episodes are a major complication of hemodialysis. Hypotension during dialysis could be directly related to a reduction in blood volume or to a decrease in cardiovascular activation as a response to decreased cardiac filling. A decreased cardiovascular activation could be due to patient-related or to dialysis-related factors. In order to study the isolated effect of a reduction in filling pressure, lower body negative pressure (LBNP) causes activation of the cardiovascular reactivity with a decrease in cardiac filling, but without the influence of the dialysis procedure that could affect cardiovascular reactivity. METHODS: We studied the relationship between relative blood volume (RBV), central venous pressure (CVP), systolic arterial pressure, heart rate, stroke volume index (SI), and total peripheral resistance index (TPRI) during a combined dialysis/ultrafiltration and during LBNP to -40 mmHg in 21 hemodialysis patients with a high incidence of hypotension. Systolic arterial pressure, heart rate, SI and TPRI were measured by Finapres. CVP was measured after cannulation of the jugular vein. During dialysis RBV was measured by a blood volume monitor (BVM). In order to study the conditions in which hypotension occurred after dialysis, we divided the patients into 2 groups: hypotensive (H) and non-hypotensive (NH) during dialysis. RESULTS: Baseline levels did not show any significant differences. During dialysis systolic arterial pressure declined gradually in the H group from 30 minutes before the onset of hypotension. There was a similar decrease of RBV and increase of heart rate in both groups with a large interindividual variation. At hypotension, H patients showed a significantly smaller increase in TPRI as compared to NH patients. The reduction in SI tended to be greater at hypotension, while CVP decreased to a similar extent in both groups. Moreover, during LBNP, a similar reduction in CVP resulted in a much smaller decrease in SI. Systolic arterial pressure was only slightly lowered due to a much greater increase in TPRI. CONCLUSION: We conclude that dialysis-related hypotension in our patient group did not result from an inability to maintain blood volume or from decreased cardiac filling. Hypotension appeared to result from the inability to adequately increase arteriolar tone and a reduction in left ventricular function. Both vascular tone and left ventricular function appeared to be impaired by the dialysis procedure.     

Haemodynamics and electrolyte balance: a comparison between on-line pre-dilution haemofiltration and haemodialysis.

BACKGROUND: An important advantage of convective therapies is improved vascular reactivity. However, it is not well known whether the vascular response during convective therapies remains superior when compared to haemodialysis (HD) with an adjusted temperature of the dialysate. It has also been suggested that convective therapies may impair small electrolyte removal through an effect on the Donnan equilibrium. In the present study, we compared the haemodynamic response and small electrolyte removal between pre-dilution on-line haemofiltration (HF) and HD procedures. METHODS: Cardiac output (CO), central blood volume (CBV) and peripheral vascular resistance (PVR) were assessed, using the saline dilution technique, in 12 stable patients during HF and HD with two different temperatures of the dialysate [36.5 and 35.5 degrees C (HD(36.5) and HD(35.5))]. Balances for sodium, potassium, calcium and conductivity were assessed using total dialysate/filtrate collections. Target filtration volume for HF was 1.2 times body weight. The temperature of the infusate was 36.5 degrees C. RESULTS: The change (Delta) in CBV was less during HD with a dialysate temperature of 35.5 degrees C (-0.03+/-0.14 l; P<0.05) compared to HF (-0.16+/-0.05 l) and HD(36.5) (-0.11+/-0.14 l), but the other haemodynamic parameters did not differ between the studied techniques. DeltaPVR was significantly related to DeltaCBV (r = -0.46; P<0.01), whereas DeltaCBV was related to ultrafiltration rate (r = -0.34; P = 0.05). DeltaCO was related to DeltaCBV (r = 0.62; P<0.001). Solute balances did not differ between HF and HD. CONCLUSION: Using the saline dilution method, no difference in the change in CO and PVR was observed between on-line HF vs HD(36.5) and HD(35.5). Only CBV declined to a significantly lesser degree during HD(35.5), although absolute differences were small. Changes in the other haemodynamic variables appeared more dependent upon the degree and rapidity of fluid removal than upon the treatment modality. No difference in small electrolyte balance was observed between HF and HD, suggesting that ionic removal is not impaired during on-line HF.     

Characteristics of hypotension-prone haemodialysis patients: is there a critical relative blood volume?

BACKGROUND: Intradialytic morbid events (IME, mostly hypotension) mainly due to ultrafiltration-induced hypovolaemia still are the most frequent complication during haemodialysis (HD). This study was performed to test the hypothesis that there is an individual critical relative blood volume (RBV(crit)) in IME-prone HD patients. METHODS: In this prospective international multicentre study, 60 IME-prone patients from nine dialysis centres were observed during up to 21 standard HD sessions without trial-specific intervention. The RBV was monitored continuously by an ultrasonic method (BVM; blood volume monitor). Also, the ultrafiltration rate was registered continuously. Blood pressure was measured at regular intervals, and more frequently during IME. All IME and specific therapeutic interventions were noted. RESULTS: In total, 537 IME, some with more than one symptom, were documented during 585 HD sessions. The occurrence of IME increased up to 10-fold from the start to the end of the HD session. RBV(crit) showed a wide inter-individual range, varying from 71 to 98%. However, the intra-individual RBV limit was relatively stable, with an SD of <5% in three-quarters of the patients. In patients with congestive heart failure, cardiac arrhythmia, advanced age, low ultrafiltration volume and low diastolic blood pressure, higher values of RBV(crit) were observed. While all correlations between RBV(crit) and patient characteristics alone were found to be of weak or medium strength, the combination of diastolic blood pressure, ultrafiltration volume and age resulted in a strong correlation with RBV(crit): the linear equation with these parameters allows an estimation of RBV(crit) in patients not yet monitored with a BVM. CONCLUSIONS: An individual RBV limit exists for nearly all patients. In most IME-prone patients, these RBV values were stable with only narrow variability, thus making it a useful indicator to mark the individual window of haemodynamic instabilities.     

Reduction of hypotensive side effects during online-haemodiafiltration and low temperature haemodialysis.

BACKGROUND: This study compares the effect of online-haemodiafiltration (o-HDF, post-dilution mode) with conventional haemodialysis (HD) and 'temperature-controlled' HD (Temp-HD) on the haemodynamic stability of hypotension-prone patients. METHODS: Seventeen patients with a history of frequent hypotensive episodes during dialysis sessions were studied, each patient serving as his or her own control. The first 25 HD treatments in comparison with 25 o-HDF sessions were evaluated using identical dialysate temperature. In the second part of the study, o-HDF (n = 25) was compared with Temp-HD (n = 25). In the latter method, the temperature of the dialysate was adjusted to result in identical energy transfer rates to those in the corresponding o-HDF. The number of hypotensive episodes, blood temperature and blood volume regulation were assessed. RESULTS: Symptomatic hypotension was much more frequent during HD (40%) than during o-HDF (4%) (P < 0.001). During o-HDF, an enhanced energy loss within the extracorporeal system occurred (o-HDF, 16.6 +/- 4.0 W; HD, 5.4 +/- 5.1 W; P < 0.0001), despite identical temperature settings for dialysate and substitution fluid. As a result, the blood returning to the patient was cooler during o-HDF than during HD (o-HDF 35 +/- 0.2 degrees C vs HD 36.5 +/- 0.3 degrees C; P < 0.0001). In o-HDF, even in the patients' circulation, the mean blood temperature was lower (o-HDF 36.7 +/- 0.2 degrees C vs HD 36.9 +/- 0.3 degrees C; P < 0.0001) and blood volume was significantly more reduced (o-HDF, 91.8 +/- 3.1%; HD, 94.0 +/- 3.2%; P < 0.05). Energy transfer rates and blood temperature did not differ significantly between o-HDF and Temp-HD. The rate of hypotensive episodes was low and not different between o-HDF (4%) and Temp-HD (4%). Neither was there any significant difference in blood volume reduction. CONCLUSIONS: O-HDF showed a significant reduction of hypotensive episodes compared with HD. Surprisingly, o-HDF resulted in cooling of the blood via enhanced thermal energy losses within the extracorporeal system, despite use of replacement fluid prepared from pre-warmed dialysate. The incidence of symptomatic hypotension was reduced to that of o-HDF by using cooler Temp-HD. Thus, unexpected blood cooling appears to be the main blood pressure-stabilizing factor in o-HDF.     

Improvement in ejection fraction by nocturnal haemodialysis in end-stage renal failure patients with coexisting heart failure.

BACKGROUND: Congestive heart failure (CHF) is an independent risk factor for mortality in the end-stage renal disease (ESRD) population. Nocturnal haemodialysis (NHD), a novel mode of renal replacement therapy, may be more effective than conventional haemodialysis in reducing intravascular volume or in removing uraemic toxins with vasoconstrictor or myocardial depressant actions, and may, therefore, improve the left ventricular (LV) systolic function of patients with coexisting cardiac and renal failure. METHODS: To test this hypothesis, we determined, in six patients (mean age+/-SD: 49.5+/-9 years), blood pressure (BP), ejection fraction (EF: radionucleotide angiography), left ventricular mass index (LVMI: echocardiography), LV fractional shortening (FS), and extracellular fluid volume (ECFV: bioelectrical impedance): before and after a mean of 3.2+/-2.1 years following conversion from conventional dialysis (3 days/week x 4 h) to NHD (6 nights/week x 8-10 h). RESULTS: There were significant reductions in systolic and mean arterial BP (138+/-10 to 120+/-9 mmHg, P=0.04; 99+/-6 to 86+/-7 mmHg, P=0.01). There was a significant increase in EF (28+/-12 to 41+/-18%, P=0.01) and a trend to greater LV FS (20+/-10 to 38+/-17%, P=0.06). Post-dialysis ECFV was not affected by dialysis mode (18.5+/-5.1 vs 18.2+/-3.5 l, P=0.76). The number of prescribed cardiovascular medications was reduced (2.2-0.7, P=0.02). CONCLUSIONS: In ESRD patients with systolic dysfunction, NHD leads to a sustained increase of EF and a reduction in the requirement for vasoactive medications in the absence of any reduction in post-dialysis ECFV.     

Assessment of refill and hypovolaemia by continuous surveillance of blood volume and extracellular fluid volume

During renal replacement therapy hypovolaemia due to ultrafiltration(UF) may, when not sufficiently counteracted by refill fromthe interstitium, result in hypotension. Combining two recentlydeveloped methods the haemodynamic process of refill was studiedin order to find characteristics featuring hypotension. Relativeblood volume (BV) and extracellular fluid volume (EFV) weremeasured continuously in 40 stable haemodialysis patients bymeans of an optical and a conductivity technique respectively.Regarding their postdialytic (PD) EFV the patients were dividedinto three groups: normohydrated (N, n=20), dehydrated (D, n=11) and overhydrated (O, n=9). Significant differences betweenthe groups were assessed in BV decrease (after 2 h until theend of treatment P<0.05 and after 3 h P<0.01), EFV decrease(after 3 h P<0.05) and occurrence of hypotensive episodes(N,5; D,7; O,none; P<0.01). During the entire session thespeed of BV decrease was significantly higher in hypotensivepatients (H) than in non-hypotensive patients (non-H). At themoment of hypotension (after 141±49 min) residual BVwas less (P<0.0005) in H (87.7±5.2%) than at the correspondingmoment in non-H patients (96.5±4.0%). PD BV and PD EFV,both expressed as a percentage of the starting value, correlatedsignificantly (r=0.63, p<0.005) and UF-volume (differencesbetween the groups were not significant) correlated to EFV decrease(r=0.45, P<0.005). In conclusion, the combination of bothnon-invasive methods elucidates the pathophysiology of UF-inducedhypotension and provides a means of reducing dialysis morbidity.The influence of tissue hydration state on these variables hasbeen shown.     

Etomidate modifies hemodynamic response to fentanyl in patients with impaired left ventricular function]

The haemodynamic effects and the side-effects of anaesthesia using high doses of fentanyl were compared in two groups of 12 patients each. All the patients had poor left ventricular function and were scheduled for elective coronary artery bypass graft surgery or valvular replacement. Patients were randomly assigned to either group. In group EF, patients were given 5 micrograms.kg-1 of fentanyl, followed by 0.3 mg.kg-1 of etomidate. Once they had lost consciousness, they were given 15 mg of pancuronium and 25 micrograms.kg-1 of fentanyl over a 5 min period. Patients in group F received the full 30 micrograms.kg-1 dose of fentanyl over a 5 min period, followed by 15 mg of pancuronium. The patients were intubated 2 min after the end of the fentanyl infusion. They were mechanically ventilated with 100% oxygen. Anaesthesia was maintained with a continuous infusion of fentanyl (total dose 100 micrograms.kg-1). The usual haemodynamic parameters were monitored and calculated, as well as pain during injection of the drugs, myoclonia, chest wall rigidity and the time to loss of consciousness. The two groups were comparable with respect to age, weight, height and surgery. One third of the patients in group EF complained of pain during etomidate injection. The time required to loose consciousness was shorter in group EF (55 +/- 16 sec) than in group F (177 +/- 56 sec) (p < 0.001). The cardiac index decrease in group EF (2.0 +/- 0.4 l.min-1.m-2 vs. 1.9 +/- 0.4 l.min-1.m-2) (p < 0.05), respectively between the time just before tracheal intubation (T1), and 10 min after tracheal intubation (T3).(ABSTRACT TRUNCATED AT 250 WORDS)     

Unexpected haemodynamic instability associated with standard bicarbonate haemodialysis.

BACKGROUND: The bicarbonate concentration in dialysis fluids for intermittent haemodialysis usually is between 32 and 35 mmol/l. The severity of chronic metabolic acidosis secondary to end-stage renal failure is very variable, however, so that in some patients pre-dialysis acidosis is overcorrected. This study aimed to analyse haemodynamic tolerances to metabolic alkalosis during intermittent haemodialysis. METHODS: In this randomized controlled trial with a single blind, cross-over design, we used dialysis liquids with two different bicarbonate concentrations, 32 (modality A) and 26 (modality B) mmol/l, and in 26 patients, 468 dialysis sessions, compared blood pressure, heart rate, incidence of hypotension and the frequency of corrections required with saline or hypertonic glucose infusions. RESULTS: The results of intradialytic haemodynamic monitoring for modalities A and B, respectively, were: lowest systolic blood pressure 120.8+/-20.8 vs 124.3+/-20.6 mmHg (P < 0.01); mean systolic blood pressure 138.5+/-23.8 vs 144.6+/-24.8 mmHg (P < 0.001); and highest heart rate 73.5+/-12.0 vs 75.8 +/- 12.9 (NS); with modality A, patients had more dialysis sessions with hypotensive episodes (5.55 vs 1.7%, P < 0.05) and required more saline or hypertonic glucose infusions (20.9 vs 13.7% of the dialysis sessions, P < 0.05). CONCLUSIONS: Mild metabolic alkalosis resulting from standard bicarbonate haemodialysis (32 mmol/l) may induce symptomatic hypotension. While normalizing chronic metabolic acidosis is desirable, reducing bicarbonate concentrations should be considered in cases of significant alkalaemia or otherwise untreatable haemodynamic instability.     

Effect of ultrafiltration on peripheral urea sequestration in haemodialysis patients.

BACKGROUND: Ultrafiltration (UF) is assumed to enhance urea removal during haemodialysis (HD) because of convective transport and because of contraction of urea distribution volume. However, UF-induced blood volume reduction has been hypothesized to enhance peripheral urea sequestration and post-dialysis urea rebound (PDUR), possibly reducing HD effectiveness. The effect of UF on PDUR was investigated in this study. METHODS: Nine HD patients were studied on two subsequent treatment days. The first HD was performed with UF (UF-rate=0.78+/-0.27 l/h), and the second treatment without UF. Serial measurements of serum water urea nitrogen concentration, arterial blood pressures (BP), and relative blood volume changes (BV%) were obtained over the duration of HD. RESULTS: BP and BV% decreased with UF (BP(sys)= -9%, BP(dia)=-8%, BP(mean)=-9%, BV%=-15%) but increased or remained unchanged without UF (BP(sys)= 9%, BP(dia)=12%, BP(mean)=11%, BV%=1%). PDUR was 28.6+/-9.6% without UF, and increased in every single patient with UF (40.7+/-13.2%, P<0.01). Modelled perfusion of the peripheral low-flow compartment decreased from 1.45+/-0.54 l/min without UF to 0.91+/-42 l/min with UF (P<0.05), thereby explaining an enhanced two-compartment effect and increasing PDUR. CONCLUSION: The significant increase in the two-compartment effect of urea kinetics observed in current HD accompanied by UF can be explained by compensatory, intradialytic blood flow redistribution induced by blood volume reduction. Because of the link between UF and blood flow, limited solute clearance treatment modes that optimize fluid removal such as variable UF will also have favourable effects on delivered dose of dialysis.     

Esmolol for control of increases in heart rate and blood pressure during tracheal intubation after thiopentone and succinylcholine

Esmolol, an ultra-short-acting cardioselective beta-adrenergic blocker, was investigated in a double-blind prospective protocol for its ability to control haemodynamic responses associated with tracheal intubation after thiopentone and succinylcholine. Thirty ASA physical status I patients received a 12-minute infusion of esmolol (500 micrograms X kg-1 X min-1 for four minutes, then 300 micrograms X kg-1 X min-1 for 8 minutes) or saline. Five minutes after the start of the drug/placebo infusion, anaesthesia was induced with 4 mg X kg-1 thiopentone followed by succinylcholine for tracheal intubation. Prior to induction esmolol produced significant decreases in heart rate (HR) (9.3 +/- 1.8 per cent) and rate-pressure product (RPP) (13.1 +/- 1.8 per cent), systolic blood pressure (SAP) (4.3 +/- 1.5 per cent) and mean arterial blood pressure (MAP) (1.7 +/- 2.0 per cent). Increases in HR, SAP and RPP after intubation were approximately 50 per cent less in patients given esmolol compared to patients given placebo. There were highly significant differences in HR (p less than 0.0001), and RPP (p less than 0.0005) and significant differences in SAP (p less than 0.05) when the maximal esmolol post-intubation response was compared to the maximal placebo response. Infusion of esmolol in the dose utilized in this study significantly attenuated but did not completely eliminate cardiovascular responses to intubation.     

Review of clinical outcomes in nocturnal haemodialysis patients after renal transplantation.

BACKGROUND: Nocturnal haemodialysis (NHD) is a novel form of haemodialysis therapy that is associated with improved blood pressure control when compared to conventional haemodialysis (CHD). Current studies suggest that NHD lowers blood pressure through a decrease in peripheral resistance. The graft and blood pressure outcomes of NHD patients who undergo renal transplantation are unknown. METHODS: We reviewed the renal allograft and blood pressure outcomes of 15 NHD patients who underwent renal transplantation. An age and vintage matched cohort of 29 CHD patients was used as controls. RESULTS: The rate of delayed graft function (DGF) tended to be higher in the NHD group compared to the CHD group (64 vs 41%, P = 0.15), however the 1-year graft function (53+/-6 vs 59+/-5 ml/min, P = 0.426) and graft survival (92 vs 95%, P = 0.751) were similar. Intra-operatively, NHD patients had lower minimum systolic (92+/-5 vs 109+/-4, P = 0.03) and diastolic (48+/-3 vs 64+/-2, P = 0.02) blood pressures in comparison to the CHD cohort. Pathologically, acute tubular necrosis accounted for 100% of DGF in the NHD group in contrast to 75% in the CHD population (P = 0.01). Pre-transplant mean systolic BP (sBP) was significantly lower in the NHD group compared to the CHD group (113+/-6 vs 145+/-10 mmHg, P<0.001). At 12 months post-transplant, mean sBP increased from baseline in the NHD group ( triangle up sBP 22+/-7 mmHg, P = 0.009) while in the CHD group mean sBP fell (Delta sBP -14+/-5 mmHg, P = 0.014). Mean arterial and diastolic BP exhibited similar changes. These trends persisted after 24 months of post-transplant follow-up. CONCLUSIONS: One-year graft outcomes and blood pressures are similar for NHD and CHD patients who undergo renal transplantation. Unlike CHD patients, NHD patients experienced a significant fall in their intra-operative blood pressures, which likely contributed towards the delayed graft function in this cohort of patients. Further prospective studies are needed to examine the underlying differences in haemodynamics and long-term graft survival between the two renal replacement modalities.     

Nicardipine HCL: clinical experience in patients undergoing anaesthesia for intracranial aneurysm clipping

Previous studies have reported haemodynamic interactions between dihydropyridine calcium antagonists and general anaesthesia. During anaesthesia for intracranial aneurysm surgery, we prospectively compared haemodynamic values obtained from 13 patients being treated with nicardipine HCl (0.15 mg.kg-1.hr-1 IV) for cerebral vasospasm against values obtained from 11 untreated controls. Prior to induction of anaesthesia, nicardipine-treated patients had significantly elevated mean +/- SD cardiac index (5.67 +/- 1.30 vs 3.99 +/- 0.73 L.min-1.m-2) while MAP (86 +/- 10 vs 99 +/- 14 mmHg) and systemic vascular resistance (647 +/- 227 vs 1141 +/- 404 dynes.sec-1.cm-5) were reduced. Heart rate, CVP, and PACWP were similar between groups. Anaesthesia induction and tracheal intubation resulted in similar haemodynamic values between groups with the exception of CVP (10 +/- 5 vs 5 +/- 2 mmHg) and PACWP (15 +/- 5 vs 8 +/- 3 mmHg) which were elevated in the nicardipine group (P less than 0.01). Mannitol infusion and deliberate hypotension resulted in nearly identical haemodynamic responses in both groups. Nicardipine-treated patients required more intravenous fluids during the operative procedure (2.4 +/- 0.3 L vs 1.5 +/- 0.4 L, P less than 0.05) and were less likely to require isoflurane supplementation to morphine sulphate/nitrous oxide anaesthesia (P less than 0.01). In summary, our experience with nicardipine HCl revealed no major untoward effects with respect to maintenance of intraoperative haemodynamic stability despite continuous antivasospasm therapy with this vasodilator.     

Haemodynamic and catecholamine responses to calcitonin gene-related peptide during volatile anaesthesia

PURPOSE: Calcitonin gene-related peptide (CGRP) produces vasodilatation, hypotension, and tachycardia. Tachycardia induced by CGRP may be due to sympathetic activation. Volatile anaesthetics attenuate activation of arterial baroreflexes. We examined the haemodynamic and endocrine effects of CGRP infusion (4 micrograms.kg-1) during anaesthesia with either enflurane or isoflurane in dogs. METHODS: Measurements of haemodynamic variables and hormone assays for plasma catecholamines were made before, during, and after CGRP infusion. Anaesthesia consisted of induction with 25 mg.kg-1 pentobarbital, followed by either enflurane (n = 7) or isoflurane (n = 7) to achieve a 1.0 end-tidal minimum alveolar concentration in oxygen 100%. RESULTS: Mean arterial pressure and systemic vascular resistance decreased (P < 0.01) and the reductions in both variables were similar during CGRP infusion in both groups. Cardiac index (CI) was increased (P < 0.01) in the enflurane group throughout the study while CI increased (P < 0.01) only during infusion in the isoflurane group. Heart rate (HR) remained unchanged (from 135 +/- 6 bpm to 134 +/- 7 bpm) in the enflurane group but tended to increase (from 162 +/- 9 bpm to 171 +/- 9 bpm) in the isoflurane group during infusion. Intergroup differences in HR were found (P < 0.05). Plasma epinephrine concentrations increased (from 42.4 +/- 12.7 pg.ml-1 to 115.3 +/- 41.8 pg.ml-1, P < 0.01) during infusion in the isoflurane group. However, these increases were suppressed (from 46.6 +/- 23.2 pg.ml-1 to 64.7 +/- 32.4 pg.ml-1) to a greater extent in the enflurane group. CONCLUSION: The haemodynamic responses, except for HR, of CGRP infusion are similar during enflurane and isoflurane anaesthesia. Suppression of tachycardia induced by CGRP is greater with enflurane than with isoflurane. The differences in HR may be due to the roles of catecholamine responses resulting from the anaesthetic-induced sympathetic suppression.