Flow-related techniques for preoperative goal-directed fluid optimization

Background. Improved postoperative outcome has been demonstratedby perioperative maximization of cardiac stroke volume (SV)with fluid challenges, so-called goal-directed therapy. OesophagealDoppler (OD) has been the most common technique for goal-directedtherapy, but other flow-related techniques and parameters areavailable and they are potentially easier to apply in clinicalpractice. The objective of this investigation was thereforeto use OD for preoperative SV maximization and compare the findingswith a Modelflow determined SV, with an OD estimated correctedflow time (FTc), with central venous oxygenation () and with muscle and brain oxygenation assessedwith near infrared spectroscopy (NIRS). Methods. Twelve patients scheduled for radical prostatectomywere anaesthetized before optimization of SV estimated by OD.A fluid challenge of 200 ml colloid was provided and repeatedif at least a 10% increment in OD SV was obtained. Values werecompared with simultaneously measured values of Modelflow SV,FTc, and muscle and cerebral oxygenation estimated by NIRS. Results. Based upon OD assessment, optimization of SV was achievedafter the administration of 400–800 ml (mean 483 ml) ofcolloid. The hypothetical volumes administered for optimizationbased upon Modelflow and differed from OD in 10 and 11 patients, respectively. Changes in FTcand NIRS were inconsistent with OD guided optimization. Conclusion. Preoperative SV optimization guided by OD for goal-directedtherapy is preferable compared with Modelflow SV, FTc, NIRSand until outcome studies for the latter are available.     

Pathophysiology and clinical implications of perioperative fluid excess

Br J Anaesth 2002; 89: 622–32     

Intraoperative oesophageal Doppler guided fluid management shortens postoperative hospital stay after major bowel surgery

Background. Occult hypovolaemia is a key factor in the aetiologyof postoperative morbidity and may not be detected by routineheart rate and arterial pressure measurements. Intraoperativegut hypoperfusion during major surgery is associated with increasedmorbidity and postoperative hospital stay. We assessed whetherusing intraoperative oesophageal Doppler guided fluid managementto minimize hypovolaemia would reduce postoperative hospitalstay and the time before return of gut function after colorectalsurgery. Methods. This single centre, blinded, prospective controlledtrial randomized 128 consecutive consenting patients undergoingcolorectal resection to oesophageal Doppler guided or centralvenous pressure (CVP)-based (conventional) intraoperative fluidmanagement. The intervention group patients followed a dynamicoesophageal Doppler guided fluid protocol whereas control patientswere managed using routine cardiovascular monitoring aimingfor a CVP between 12 and 15 mm Hg. Results. The median postoperative stay in the Doppler guidedfluid group was 10 vs 11.5 days in the control group P<0.05.The median time to resuming full diet in the Doppler guidedfluid group was 6 vs 7 for controls P<0.001. Doppler patientsachieved significantly higher cardiac output, stroke volume,and oxygen delivery. Twenty-nine (45.3%) control patients sufferedgastrointestinal morbidity compared with nine (14.1%) in theDoppler guided fluid group P<0.001, overall morbidity wasalso significantly higher in the control group P=0.05. Conclusions. Intraoperative oesophageal Doppler guided fluidmanagement was associated with a 1.5-day median reduction inpostoperative hospital stay. Patients recovered gut functionsignificantly faster and suffered significantly less gastrointestinaland overall morbidity.     

Determination of fluid status in haemodialysis patients with whole body and calf bioimpedance techniques

Aim: The aim of this study was to demonstrate the ability of widely used bioimpedance techniques to assess dry weight (DW) and to predict a state of normal hydration in haemodialysis patients whose post‐dialysis weight had been gradually reduced from baseline in successive treatments over time. Methods: Calf bioimpedance spectroscopy (cBIS) was employed to determine DW (DW_cBIS) as defined by flattening of an intradialytic continuously measured resistance curve and by normalized resistivity (nRho) being in the gender‐specific normal range. The wECV/TBW ratio was determined by ‘classical’ wrist‐to‐ankle whole body bioimpedance spectroscopy (wBIS); in addition, a novel whole body model (WBM) based on wBIS was used to predict normal hydration weight (NHW_WBM). Results: Twenty‐one haemodialysis patients were studied; 11 ± 6 measurements were performed per patient. Nine patients reached DW_cBIS (DW_cBIS group), while 12 patients remained fluid‐overloaded (non‐DW_cBIS group). Change in wECV as measured by wBIS accounted for 46 ± 23% in DW_cBIS group, which was higher than in non‐DW_cBIS group (33 ± 48%, P < 0.05) of actual weight loss at the end of study. In both groups the wECV/TBW ratio did not change significantly between baseline and study end. Mean predicted NHW_WBM at baseline was 3.55 ± 1.6 kg higher than DW_cBIS. The difference in DW_cBIS and NHW_WBM was 1.97 ± 1.0 kg at study end. Conclusion: WBM could be useful to predict a target range of normal hydration weight particularly for patients with substantial fluid overload. The cBIS provides an accurate reference for the estimation of DW so that combined use of cBIS and WBM is promising and warrants further studies.     

Thoracic electrical bioimpedance measurement of cardiac output and cardiovascular responses to the induction of anaesthesia and to laryngoscopy and intubation

Noninvasive methods of determining cardiac output (by thoracic electrical bioimpedance) and arterial pressure (by intermittent oscillometry) were used to record minute-by-minute changes in heart rate, mean arterial pressure, stroke volume, cardiac output and systemic vascular resistance following induction of general anaesthesia and laryngoscopy and intubation in 60 healthy female patients who were either unpremedicated, or premedicated with temazepam or papaveretum-hyoscine. Anaesthesia was induced with a sleep dose (3-5 mg.kg-1) of thiopentone and maintained with 70% nitrous oxide in oxygen with 0.5-1% enflurane. Tracheal intubation was facilitated by administration of vecuronium 0.1 mg.kg-1. Mean arterial pressure and cardiac output decreased maximally 5 min after induction in all premedication groups by mean estimates of 21-25% and 14-22% respectively. Heart rate increased initially one minute after induction, but decreased to less than the baseline value 5 min after induction. Systemic vascular resistance was unchanged. The stimulus of laryngoscopy and tracheal intubation was accompanied by a significant pressor response and tachycardia one minute after intubation (with mean increases in mean arterial pressure and heart rate of 29-34% and 22-33% respectively). The increase in mean arterial pressure was secondary to an increase in systemic vascular resistance (36-57%), and was accompanied by a decrease in stroke volume (-25 to -31%). These changes were significant in all three groups. Cardiac output decreased only in unpremedicated patients. There were wide variations in the different haemodynamic indices.(ABSTRACT TRUNCATED AT 250 WORDS)     

Body composition measurements using bioimpedance analysis in peritoneal dialysis patients are affected by the presence of dialysate

The presence of peritoneal dialysate when performing bioimpedance analysis may affect body composition measurements. The aim of this study was to evaluate the impact of dialysate on body composition measurements in Asians. Forty‐one patients undergoing maintenance peritoneal dialysis in our hospital peritoneal dialysis unit were included in this study. Dialysate was drained from the abdomen prior to measurement, and bioimpedance analysis was performed using multi‐frequency bioimpedance analysis, with each subject in a standing position (D‐). Dialysate was then administered and the measurement was repeated (D+). The presence of peritoneal dialysate led to an increase in intracellular water (ICW), extracellular water (ECW), and total body water (D‐: 20.33 ± 3.72 L for ICW and 13.53 ± 2.54 L for ECW; D+: 20.96 ± 3.78 L for ICW and 14.10 ± 2.59 L for ECW; P < 0.001 for both variables). Total and trunk oedema indices were higher in the presence of peritoneal dialysate. In addition, the presence of peritoneal dialysate led to an overestimation of mineral content and free fat mass (FFM) for the total body; but led to an underestimation of body fat (D‐: 45.80 ± 8.26 kg for FFM and 19.30 ± 6.27 kg for body fat; D+: 47.51 ± 8.38 kg for FFM and 17.59 ± 6.47 kg for body fat; P < 0.001 for both variables). Our results demonstrate that the presence of peritoneal dialysate leads to an overestimation of FFM and an underestimation of fat mass. An empty abdomen is recommended when evaluating body composition using bioimpedance analysis.     

Immediate extubation and epidural analgesia allow safe management in a high-dependency unit after two-stage oesophagectomy. Results of eight years of experience in a specialized upper gastrointestinal unit in a district general hospital

Background. The perioperative management of two-stage oesophagectomyhas not been standardized and the prevailing practice regardingthe timing of extubation after the procedure varies. This audithas evaluated the outcome, in particular the respiratory morbidityand mortality, after immediate extubation in patients who havehad thoracic epidural analgesia. Methods. All the patients who underwent two-stage oesophagectomyby a single specialist upper gastrointestinal surgeon were recordedboth retrospectively (1993–1999) and prospectively (1999–2001).Physical characteristics, comorbid factors, anaesthetic managementand postoperative events were recorded on a computer database.Analysis was undertaken to evaluate the morbidity and mortality,in particular the need for reventilation and transfer to theITU. Results. Seventy-six patients underwent two-stage oesophagectomybetween 1993 and 2001. Seventy-three (96%) patients were extubatedin theatre and transferred to a high-dependency bed. Three wereventilated electively and extubated within 36 h and madean uncomplicated recovery. Seven (10%) of the immediately extubatedpatients subsequently needed admission to the ICU and reventilation.Sixty-seven patients had effective epidural analgesia and nineneeded i.v. morphine by patient-controlled analgesia. The 30-dayor in-hospital mortality was 2.6% (2 of 76). A further two patientsdied within 90 days, but after discharge. Respiratory complicationswere responsible for half of the overall morbidity (44.7%).Respiratory failure occurred in 6.5% (5 of 76) and acute respiratorydistress syndrome in 2.6% (2 of 76). Both the in-hospital deathsoccurred in patients requiring reventilation and resulted fromrespiratory complications. The following factors were foundto be significant in the reventilated patients: duration ofone-lung ventilation; forced expiratory volume in the firstsecond; and ratio of forced expiratory volume in the first second/forcedvital capacity. Conclusions. Immediate extubation after two-stage oesophagectomyin patients with thoracic epidural analgesia is safe and associatedwith low morbidity and mortality. Patients can be managed ina high-dependency unit, thus avoiding the need for intensivecare. This has cost-saving and logistical implications. Br J Anaesth 2003; 90: 474–9     

围手术期目标导向容量治疗用于预防腹部手术后胃肠道并发症的Meta分析

目的 评价围术期目标导向容量治疗对预防腹部手术后胃肠道并发症的有效性,为制定临床合理的个体化容量治疗方案提供理论依据.方法 计算机检索Cochrane图书馆(2010年第3期)、PubMed、EMbase、Highwire、CBM、CNKI等中外生物医学数据库.收集关于围手术期目标导向容量治疗对预防腹部手术后胃肠道并发症方面的临床随机对照试验,检索日期由2000年1月至2010年12月.按Cochrane系统评价方法,评价所纳入研究的文献质量,并提取有效数据后采用RevMan5.0软件进行Meta分析.结果 纳入10项研究,共计775例患者.Meta结果 显示:目标导向容量治疗可显著提高机体氧供(WMD=82.95,95%CI:17.43～148.46),降低胃肠道术后并发症的发生率(RR=0.39,95%CI:0.29～0.52),并缩短住院天数(WMD=-2.06,95%CI:-2.95～-1.17).结论 围手术期目标导向容量治疗可以有效预防术后胃肠道并发症的发生.

Abstract：

Objective To assess whether goal-directed fluid management can prevent gastrointestinal complications in major surgery. Methods Electronic databases including Cochrane library (Issue 3,2010), Pubmed, EMbase, Highwire, CBM, and CNKI were searched. The date of search was between January 2000 and December 2010. Randomized controlled trials (RCTs) were indentified studying association of goal-directed therapy (GDT) with gastrointestinal complications. Study selection and meta-analysis were conducted according to the Cochrane Handbook for systematic reviews. Data were extracted from these trials by 3 reviewers independently and analyzed by RevMan5.0 software. Results Ten trials involving 775 patients were included. GDT significantly improved oxygen supply (WMD=82.95, 95% CI: 17.43-148.46). GDT reduced postoperative hospital stay (WMD=-2.06, 95% CI:-2.95——1.17) and decreased postoperative complication rate after major surgery(RR=0.39, 95% CI: 0.29-0.52). Conclusion Goal-directed fluid management can stabilize cardiac output, augment oxygen supply, and therefore reduce postoperative complications.     

Nitrous oxide for monitoring fluid absorption in volunteers

Background. We studied whether nitrous oxide (N₂O) added toa fluid allows the infused volume to be quantified by measuringN₂O in the expired air during normal breathing. If so, N₂O mightserve as a tracer of fluid absorption during endoscopic surgery. Methods. Twelve male volunteers received continuous and intermittenti.v. infusions (5–45 min) of fluid containing 40 ml litre^–1of N₂O. Breath N₂O and CO₂ concentrations were measured everysecond via a flared nasal cannula, a standard nasal cannula,or a Hudson mask. Results. An expression for the amount of infused fluid was obtainedby calculating the area under the N₂O concentration–timecurve for samples representative for exhalation (CO₂>median)and then dividing this area by the median CO₂ for the remainingsamples. The N₂O method then estimated fluid volumes of between50 and 1400 ml within a 95% prediction interval of ±200ml. There were differences of up to 14% in results between theairway devices tested, but the volunteers preferred the flarednasal cannula. N₂O showed a distinctly higher 3 min variabilityduring intermittent infusion, which could indicate whether fluidabsorption is directly intravascular or extravascular. No adverseeffects were seen. Conclusions. N₂O method does not require forced end-expiratorybreath sampling but still predicts an administered fluid volumewith high precision. N₂O variability can probably be used todistinguish immediately between intravascular and perivesicalfluid absorption during surgery. Declaration of interest. Following completion of the study,the sponsors (AGA-AB) gave the patent of the N₂O method to thecorresponding author.     

Outcome of ASA III patients undergoing day case surgery

Background. Day case surgery is becoming more acceptable, evenfor patients with complex medical conditions. Current recommendationssuggest that patients who are graded as American Society ofAnaesthesiologists physical status (ASA) III may be suitablefor this approach. There is only a small amount of publisheddata available to support this. We present a retrospective reviewof ASA III patients who had undergone day surgical proceduresin our unit. Methods. We carried out a retrospective case controlled reviewof 896 ASA III patients who had undergone day case proceduresbetween January 1998 and June 2002 using the existing computerizedpatient information system. The system records admission rates,unplanned contact with healthcare services and post-operativecomplications in the first 24 h after discharge. Results. We demonstrated no significant differences in unplannedadmission rates, unplanned contact with health care services,or post-operative complications in the first 24 h after dischargebetween ASA III and ASA I or II patients. Conclusion. With good pre-assessment and adequate preparationASA III patients can be treated safely in the day surgery setting. Br J Anaesth 2004; 92: 71–4     

Prediction of fluid responsiveness in patients during cardiac surgery

Background. Left ventricular stroke volume variation (SVV) hasbeen shown to be a predictor of fluid responsiveness in varioussubsets of patients. However, the accuracy and reliability ofSVV are unproven in patients ventilated with low tidal volumes. Methods. Fourteen patients were studied immediately after coronaryartery bypass grafting (CABG). All patients were mechanicallyventilated in pressure-controlled mode [tidal volume 7.5 (1.2)ml kg^–1]. In addition to standard haemodynamic monitoring,SVV was assessed by arterial pulse contour analysis. Left ventricularend-diastolic area index (LVEDAI) was determined by transoesophagealechocardiography. A transpulmonary thermodilution techniquewas used for measurement of cardiac index (CI), stroke volumeindex (SVI) and intrathoracic blood volume index (ITBI). Allvariables were assessed before and after a volume shift inducedby tilting the patients from the anti-Trendelenburg (30°head up) to the Trendelenburg position (30° head down). Results. After the change in the Trendelenburg position, SVVdecreased significantly, while CI, SVI, ITBI, LVEDAI, centralvenous pressure (CVP) and pulmonary artery occlusion pressure(PAOP) increased significantly. Changes in SVI were significantlycorrelated to changes in SVV (r=0.70; P<0.0001) and to changesin LVEDAI, ITBI, CVP and PAOP. Only prechallenge values of SVVwere predictive of changes in SVI after change from the anti-Trendelenburgto the Trendelenburg position. Conclusions. In patients after CABG surgery who were ventilatedwith low tidal volumes, SVV enabled prediction of fluid responsivenessand assessment of the haemodynamic effects of volume loading.     

Quantifying acute changes in volume and nutritional status during haemodialysis using bioimpedance analysis

Aim: To determine the precision of multi‐frequency bioimpedance analysis (MFBIA) in quantifying acute changes in volume and nutritional status during haemodialysis, in patients with end‐stage renal disease (ESRD). Methods: Using whole‐body MFBIA, we prospectively studied changes in total body water (TBW), extracellular volume (ECV), intracellular volume (ICV), lean body mass (LBM), body cell mass (BCM) and fat mass (FM), pre‐ and post‐haemodialysis and tested the agreement of volume changes with corresponding acute weight change and ultrafiltration volume (UF) using Bland‐Altman analysis. Results: Forty‐four prevalent and 17 incident haemodialysis patients were studied (median age 55 years, 56% males). MFBIA‐derived TBW, ECV, ICV, LBM and BCM were significantly reduced after haemodialysis (P < 0.001), but FM remained constant. TBW change estimated weight change with mean bias of ?0.52 L, with 56/61 (91.8%) data points within limits of agreement (?2.74 L, 1.69 L). TBW change estimated UF with mean bias of ?0.62 L, with 55/61 (90.2%) data points within limits of agreement (?2.68 L, 1.43 L). ECV change underestimated weight change and UF with mean bias of ?1.17 L and ?1.27 L respectively. Similarly, ICV change underestimated both clinical measures with corresponding mean bias of ?1.34 L and ?1.44 L. Comparing incidents versus prevalent haemodialysis patients, TBW change estimated weight change with smaller mean bias (?0.10 L vs?0.69 L, respectively) and narrower limits of agreement. Conclusion: Multi‐frequency bioimpedance analysis‐derived TBW change has the best agreement with acute clinical volume change during haemodialysis compared to ECV or ICV change alone, but overall degree of precision remains poor. Nutritional assessment using LBM and BCM measurements is significantly confounded by hydration status.     

Liberal or restrictive fluid administration in fast-track colonic surgery: a randomized, double-blind study

Background: Evidence-based guidelines on optimal perioperative fluid managementhave not been established, and recent randomized trials in majorabdominal surgery suggest that large amounts of fluid may increasemorbidity and hospital stay. However, no information is availableon detailed functional outcomes or with fast-track surgery.Therefore, we investigated the effects of two regimens of intraoperativefluids with physiological recovery as the primary outcome measureafter fast-track colonic surgery. Methods: In a double-blind study, 32 ASA I–III patients undergoingelective colonic surgery were randomized to ‘restrictive’(Group 1) or ‘liberal’ (Group 2) perioperative fluidadministration. Fluid algorithms were based on fixed rates ofcrystalloid infusions and a standardized volume of colloid.Pulmonary function (spirometry) was the primary outcome measure,with secondary outcomes of exercise capacity (submaximal exercisetest), orthostatic tolerance, cardiovascular hormonal responses,postoperative ileus (transit of radio-opaque markers), postoperativenocturnal hypoxaemia, and overall recovery within a well-definedmultimodal, fast-track recovery programme. Hospital stay andcomplications were also noted. Results: ‘Restrictive’ (median 1640 ml, range 935–2250ml) compared with ‘liberal’ fluid administration(median 5050 ml, range 3563–8050 ml) led to significantimprovement in pulmonary function and postoperative hypoxaemia.In contrast, we found significantly reduced concentrations ofcardiovascularly active hormones (renin, aldosterone, and angiotensinII) in Group 2. The number of patients with complications wasnot significantly different between the groups (1 vs 6 patients,P = 0.08). Conclusions: A ‘liberal’ fluid regimen led to a transient improvementin pulmonary function and postoperative hypoxaemia but no otherdifferences in all-over physiological recovery compared witha ‘restrictive’ fluid regimen after fast-track colonicsurgery. Since morbidity tended to be increased with the ‘restrictive’fluid regimen, future studies should focus on the effect ofindividualized ‘goal-directed’ fluid administrationstrategies rather than fixed fluid amounts on postoperativeoutcome.     

Effect of preoperative amino acid infusion on thermoregulatory response during spinal anaesthesia

Background. Intravenous amino acid infusion during general anaesthesiaprevents decreases in core temperature resulting from increasedenergy expenditure and heat accumulation. Methods. We investigated whether such stimulation also occursduring spinal anaesthesia, which blocks sympathetic nervousactivity. We examined the effect of i.v. amino acid infusionon changes in core temperature during spinal anaesthesia. Thirty-fivepatients were divided into two groups: an i.v. amino acid infusiongroup (4 kJ kg^–1 h^–1 starting 2 hbefore surgery); and a saline infusion group. Tympanic membranecore temperature, forearm–fingertip temperature gradient(an index of peripheral vasoconstriction) and mean skin temperaturewere measured for 90 min after the onset of spinal anaesthesia. Results. Changes in mean arterial pressure and heart rate didnot differ significantly between the groups during the studyperiod. Mean final core temperature 90 min after inductionof spinal anaesthesia was 35.8 (SEM 0.1)°C in the salinegroup and 36.6 (0.1)°C in the amino acid group (P<0.05).The increased level of oxygen consumption in the amino acidgroup compared with the saline group was preserved even afterthe onset of spinal anaesthesia. The thermal vasoconstrictionthreshold, defined as the tympanic membrane temperature thattriggered a rapid increase in forearm–fingertip temperaturegradient, was increased in the amino acid group [36.8 (0.1)°C]compared with the saline group [36.5 (0.1)°C] (P<0.05). Conclusions. Preoperative infusion of amino acids effectivelyprevents spinal anaesthesia-induced hypothermia by maintaininga higher metabolic rate and increasing the threshold core temperaturefor thermal vasoconstriction. Br J Anaesth 2003; 90: 58–61     

Near-patient testing for coagulopathy after cardiac surgery

Background. We assessed the accuracy and precision of a newnear-patient testing system (Hemochron^® Response) by measuringprothrombin time and activated partial thromboplastin time (PTand APTT) in 50 patients undergoing cardiac surgery using cardiopulmonarybypass and comparing the results with laboratory assays. Methods. Blood samples were taken at the beginning of surgeryand the PT and APTT was measured both in the laboratory andby the Hemochron^® Response. The tests were repeated 30 minafter reversal of heparin with protamine. Results. Before bypass, the bias for PT was only +0.34, withsmall 95% limits of agreement. Making the same measurementsafter bypass, the Hemochron^® Response under-read and thebias was –3.27, with an increase of the 95% limits ofagreement. With the APTT, the bias and the 95% limits of agreementwere greater before bypass, and became even wider after bypass. Conclusions. We found good agreement in the PT and clinicallyacceptable levels of agreement in the APTT during the pre-bypassperiod. After bypass, bias became greater for both PT and APTTand the limits of agreement could be clinically unacceptable. Br J Anaesth 2003; 90: 499–501     

腰椎术后脑脊液漏的处理

1993年7月～2007年5月,我科共行腰椎手术429例,其中18例术后发生脑脊液漏,发生率4．2％,经积极处理后均治愈。