Influence of short-term venous stasis on clinical chemistry testing.

Control and standardization of preanalytical variability is a critical factor for achieving accuracy and precision in laboratory testing. Although venous stasis from tourniquet placement during venepuncture should be minimized, as it has been claimed to account for spurious and significant variations for several analytes in plasma, there is controversy surrounding its real impact on laboratory testing. The aim of the present study was the investigation of the influence of short-term venous stasis on routine biochemical testing, by measuring the plasma concentration of 12 common analytes, including proteins, protein-bound substances, enzymes and electrolytes, in plasma specimens collected either without venous stasis or following the application of standardized external pressure of 60 mm Hg using a sphygmomanometer for 1 and 3 min. Although the overall correlation between measures was acceptable, the pattern of change was mostly dependent on the length of stasis, size and protein-binding characteristics of the analytes, achieving clinical significance for albumin, calcium and potassium after 1-min stasis, and alanine aminotransferase, albumin, calcium, chloride, total cholesterol, glucose and potassium after 3-min stasis. Statistically significant differences could be observed in seven (alanine aminotransferase, albumin, calcium, total cholesterol, creatine kinase, iron and potassium) and ten (alanine aminotransferase, albumin, calcium, chloride, total cholesterol, creatine kinase, creatinine, glucose, iron and potassium) out of the 12 analytes tested, after 1- and 3-min venous stasis, respectively. The most clinically significant changes from standard venepuncture, when compared to the current analytical quality specifications for desirable bias, occurred for potassium (1-min stasis, -2.8%; 3-min stasis, -4.8%, both p<0.001), calcium (1-min stasis, +1.6%, p<0.05; 3-min stasis, +3.6%, p<0.001) and albumin (1-min stasis, +3.5%; 3-min stasis, +8.6%, both p<0.001). As most of these effects are dependent on the stasis time during venepuncture and biochemical or physiological characteristics of the analyte, these variations could likely be anticipated, allowing the most appropriate preventive measures to be adopted.     

Preanalytical variability in laboratory testing: influence of the blood drawing technique.

The predominant technique used to draw blood for laboratory testing is a conventional straight needle attached to an evacuated tube system. However, alternative tools might be advantageous in exceptional circumstances. The use of butterfly devices has been traditionally discouraged for reasons of costs and due to the high risk of obtaining unsuitable samples, but there is no convincing evidence to support the latter indication. The purpose of this study was to compare results of hematological and clinical chemistry testing, after drawing blood into evacuated tubes, employing either a traditional 21-gauge straight needle or a 21-gauge butterfly device with 300-mm-grade polyvinyl chloride tubing. Blood samples and complete sets of data were successfully obtained for 30 consecutive outpatients. Of the 43 hematological and clinical chemistry parameters measured, means for paired samples collected by the two alternative drawing techniques did not differ significantly, except for serum sodium, white blood cells and platelets counts. Bland-Altman plots and limits-of-agreement analysis showed mean bias of between -7.2% and 1.7% and relative coefficients of variation ranging from 0.2% to 21.2%. The 95% agreement interval in the set of differences was acceptable and was mostly within the current analytical quality specifications for desirable bias. The rate of hemolysis in plasma was not statistically different between the two collection techniques. Taken together, the results of the present investigation suggest that, when a proper technique is used and within certain limitations, the butterfly device may be a reliable alternative to the conventional straight needle to draw blood for laboratory testing.     

21G和23G细针对超声引导下甲状腺结节穿刺标本满意率的比较

目的比较21G和23G型号细针对甲状腺结节穿刺标本的满意率。 方法2015年1月至2015年2月到首都医科大学附属友谊医院超声医学科进行甲状腺穿刺的病例共123例,123个结节中每个结节分别用21G和23G针进行超声引导下细针穿刺抽吸活组织检查（US-FNAB）,所有标本进行液基细胞学制片,将标本分为满意和不满意2种,21G和23G针穿刺的先后顺序按照随机表进行,比较21G细针和23G细针在进行甲状腺结节穿刺时标本的满意率。 结果21G针穿刺甲状腺结节的标本满意率87.8%（108/123）,23G针穿刺甲状腺结节的标本满意率86.2%（106/123）。差异无统计学意义（χ²=0.045,P>0.05）。 结论23G细针和21G细针在甲状腺结节穿刺中取得标本的满意率相近,23G细针穿刺可以作为一种方法用于临床工作。     

Acoustic Radiation Force Impulse (ARFI) imaging-based needle visualization

Ultrasound-guided needle placement is widely used in the clinical setting, particularly for central venous catheter placement, tissue biopsy and regional anesthesia. Difficulties with ultrasound guidance in these areas often result from steep needle insertion angles and spatial offsets between the imaging plane and the needle. Acoustic Radiation Force Impulse (ARFI) imaging leads to improved needle visualization because it uses a standard diagnostic scanner to perform radiation force based elasticity imaging, creating a displacement map that displays tissue stiffness variations. The needle visualization in ARFI images is independent of needle-insertion angle and also extends needle visibility out of plane. Although ARFI images portray needles well, they often do not contain the usual B-mode landmarks. Therefore, a three-step segmentation algorithm has been developed to identify a needle in an ARFI image and overlay the needle prediction on a coregistered B-mode image. The steps are: (1) contrast enhancement by median filtration and Laplacian operator filtration, (2) noise suppression through displacement estimate correlation coefficient thresholding and (3) smoothing by removal of outliers and best-fit line prediction. The algorithm was applied to data sets from horizontal 18, 21 and 25 gauge needles between 0-4 mm offset in elevation from the transducer imaging plane and to 18G needles on the transducer axis (in plane) between 10 degrees and 35 degrees from the horizontal. Needle tips were visualized within 2 mm of their actual position for both horizontal needle orientations up to 1.5 mm offset in elevation from the transducer imaging plane and on-axis angled needles between 10 degrees-35 degrees above the horizontal orientation. We conclude that segmented ARFI images overlaid on matched B-mode images hold promise for improved needle visibility in many clinical applications.     

An Experimental Study on RBC Count and Serum Potassium Concentration Changes During Compression Transfusion of WBC-removal Whole Blood

Objective:To observe changes in RBC count,changes,RBC morphology,and serum potassium during compressed transfusion of WBC-removal whole blood.Methods:Prepared human WBC-removal whole blood and connected transfusion apparatus with different sizes of intravenous detaining needles(18G,20 G,22G and 24G).Observed RBC count and serum potassium concentration under different pressures(100 mmHg,200 mmHg,and 300 mmHg)as blood flowed out of the pinhead end of the intravenous detaining needle.Samples obtained with the 20 G needle were smeared on glass slides,and RBC morphologic changes were observed under an oil immersion lens.Results:RBC count and serum potassium changed slightly under different pressures with different sizes of intravenous detaining needles as blood flowed through the transfusion apparatus.In addition,the observation of blood samples under a common light microscope revealed that coarse-prick,oblong,and spindle cell counts in the visual fields increased gradually as the pressure increased.Additionally,aportion of cells had undergone splintering.Conclusions:While applying 18 G,20G,22 G and 24 G intravenous detaining needles for blood transfusion under less than 300 mmHg of pressure,no significant RBC count change was found in blood samples in the short term.However,there were significant RBC morphologic changes.The results could offer more basis to ensure the clinical safety of patients undergoing blood transfusion.     

Photoinstability of S-nitrosothiols during sampling of whole blood: a likely source of error and variability in S-nitrosothiol measurements

BACKGROUND: The determination of reference intervals for the concentration of total S-nitrosothiols (RSNOs) in blood is a highly controversial topic, likely because of the inherent instability of these species. Most currently available techniques to quantify RSNOs in blood require considerable sample handling and multiple pretreatment steps during which light exposure is difficult to completely eliminate. We investigated the effect of brief light exposure on the stability of RSNO species in blood during the initial sampling process. METHODS: A novel amperometric RSNO sensor, based on an immobilized organoselenium catalyst at the distal tip of an electrochemical nitric oxide detector, was used to determine RSNO species in diluted whole blood without centrifugation or pretreatment. Porcine blood was collected into aluminum foil-wrapped syringes via a 12-inch butterfly needle tube assembly. Two blood samples were collected from the same animal -- one with the butterfly needle tubing wrapped in aluminum foil and one with the tubing exposed to ambient room light. The RSNO concentrations in these sequential blood samples were determined by a standard addition procedure. RESULTS: Eight sets of measurements were made in 6 animals. Samples exposed to light yielded RSNO concentrations only 23.6% (7.2%) [mean (SD)] of the RSNO concentrations determined in samples that were shielded from light and obtained from the same animals. CONCLUSIONS: These results suggest significant photoinstablity of RSNOs in whole blood and indicate the critical importance of proper light protection during sampling and processing of blood samples for the accurate determinations of endogenous RSNO concentrations.     

A randomized trial of winged Vialon cannulae and metal butterfly needles

The purpose of this parallel randomized study was to evaluate whether subcutaneous infusion sites initiated with winged vialon cannulae would have fewer skin reactions and longer site duration than metal butterfly needles and reduce needlestick injuries to staff. Data were collected on 42 hospice inpatients from the time of insertion of the first needle or cannula to the time of the first replacement of that device. A non-parametric survival plot for time (Kaplan-Meier method) was conducted and the survival time to replacement of the Vialon cannula was found to be longer than the metal butterfly needle. During the study period there were a total of four needlestick injuries to staff from metal butterfly needles. The authors conclude that Vialon cannulae reduce the frequency of site changes and are safer for staff to use because of the reduced risk of needlestick injuries.     

Evaluation of a simple method for minimizing iatrogenic blood loss from discard volumes in critically ill newborns and children

OBJECTIVE: To validate a simple method avoiding discard volumes in pediatric patients with indwelling arterial and venous lines. DESIGN: Zero-discarding was achieved by passive extracorporeal arteriovenous backflow via standard single pressure transducer equipment. We tested backflow distances (10, 20 and 30 cm beyond the sampling port), corresponding to withdrawal volumes of 0.6 ml, 0.8 ml and 1.0 ml, respectively, in comparison to conventional sampling with discard of 0.6 ml. With the backflow technique, the "withdrawal volume" was flushed back to the patient after sampling. We enrolled 120 patients who were allocated to either of the following paired sampling procedures: 10 cm versus conventional, 20 cm versus conventional, 30 cm versus conventional and two paired conventional samples. The order of the sampling was randomly allocated. Bias and precision were determined using Bland-Altman diagrams and algorithms. RESULTS: No appreciable difference was found for blood gases, hemoglobin, potassium and calcium between the backflow technique and conventional sampling. Sodium results and blood glucose showed a bias towards higher values with the backflow technique (mean difference, sodium, 0.9 mmol/l; glucose, mean difference 0.5 mmol/l, standard deviation 0.44 mmol/l). CONCLUSIONS: The backflow technique provides reliable results for blood gases and electrolytes. However, in patients at risk of hypoglycemia, the backflow method should not be used to monitor blood glucose levels.     

A multicenter, open-label, randomized, two-period crossover trial comparing glycemic control, satisfaction, and preference achieved with a 31 gauge x 6 mm needle versus a 29 gauge x 12.7 mm needle in obese patients with diabetes mellitus

BACKGROUND: Optimal needle length for subcutaneous insulin injection may differ for obese and nonobese patients, which could affect management of diabetes mellitus (DM). OBJECTIVE: The aim of this study was to determine whether 31 gauge (G) x 6 mm (shorter) needles are appropriate alternatives to 29 G x 12.7 mm (longer) needles in obese patients with DM. METHODS: A multicenter, open-label, randomized, 2-period crossover trial was conducted in insulin-treated patients with type 1 or 2 DM with body mass index >or=30 kg/m(2) and glycosylated hemoglobin A(1c) (HbA(1c)) concentration 相似文献   

婴幼儿静脉留置针留置方法研究

目的　探讨婴幼儿静脉留置针留置方法。方法　将 10 0例婴幼儿随机分成两组 ,采用改进法为观察组 ,75例 ,运用常规方法为对照组 ,2 5例。结果　两组婴幼儿静脉留置针成功率经 χ2检验 ,χ2 =15 .5 9,P<0 .0 1,留置时间经 t检验 ,t=36 .3,P<0 .0 1有显著性差异 ;塞管、局部发红情况经χ2 检验 ,P>0 .0 5 ,无显著性差异。结论　小于 10°角进入皮肤 ,浅而渐深进入血管 ,回血后送软管为可行的婴幼儿留置针穿刺方法 ;高浓度肝素一次性封管既可减少工作量 ,也能长时间地维持软管通畅。增加必要措施 ,做好陪护健康教育成为婴幼儿固定留置针重要的一关。     

The effect of sex, deviation from ideal weight and sampling time on blood constituents in presumably healthy subjects.

In order to verify the influence of sampling time on blood constituents, populations of supposedly healthy subjects were grouped according to age, sex, deviation from their ideal weight, state of fasting or nonfasting, and time of sampling. Each fasting subject in one group underwent two samplings during the course of a morning: the first at 08.00 and the second between 09.00 and 12.00. In the second group, the first was taken at 13.00, and the second between 14.00 and 16.00. Subjects in the second group had eaten a standard meal of 700 calories at 12.00. Differences between the paired samples from a given individual are discussed with respect to the time of sampling for plasma urea, creatinine, proteins, albumin, calcium, sodium, potassium, cholesterol, uric acid, chloride ions, phosphate, bilirubin, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine phosphokinase, alkaline phosphatase, hemoglobin and erythrocyte and leukocyte counts. Variations due to the time of sampling were large for phosphorus, bilirubin, and leukocyte count.     

Effects of bicarbonate therapy on hemodynamics and tissue oxygenation in patients with lactic acidosis: a prospective, controlled clinical study

OBJECTIVE: To determine whether correction of acidemia using bicarbonate improves hemodynamic variables and tissue oxygenation in patients with lactic acidosis. DESIGN: Prospective, randomized, blinded, cross over study. Each patient sequentially received sodium bicarbonate and sodium chloride. The order of the infusions was randomized. PATIENTS: Ten patients with metabolic acidosis, increased arterial plasma lactate concentrations (greater than 2.45 mmol/L), and no severe renal failure (creatinine less than 250 mumol/L [less than 2.3 mg/dL]). METHOD: Sodium bicarbonate (1 mmol/kg body weight) or equal volume of sodium chloride was injected iv at the beginning of two successive 1-hr study periods. Period order was randomized. Arterial and venous blood gas measurements, plasma electrolytes (sodium, potassium, chloride), osmolality and lactate, 2,3-diphosphoglycerate (DPG), and oxygen hemoglobin affinity, hemodynamic variables, oxygen delivery, and oxygen consumption measurements were obtained before and repeatedly during the 1-hr period after the injection of bicarbonate or sodium chloride. MEASUREMENTS AND MAIN RESULTS: Sodium bicarbonate administration increased arterial and venous pH, serum bicarbonate, and the partial pressure of CO2 in arterial and venous blood. Hemodynamic responses to sodium bicarbonate and sodium chloride were similar. Tissue oxygenation (as estimated by oxygen delivery, oxygen consumption, oxygen extraction ratio, and transcutaneous oxygen pressure) was not modified. No changes in serum sodium concentration, osmolality, arterial and venous lactate, red cell 2,3-DPG levels, or hemoglobin affinity for oxygen were observed. CONCLUSION: Administration of sodium bicarbonate did not improve hemodynamic variables in patients with lactic acidosis, but did not worsen tissue oxygenation.     

两种外周留置针临床应用效果的比较

目的比较密闭式外周留置针和开放式外周留置针在临床上的应用效果。方法 2011年1-3月,便利抽样法选择上海市第六人民医院心胸外科收治的需静脉输液患者200例为研究对象,按随机数字表法将其分为观察组和对照组,每组100例。观察组患者采用密闭式Y型留置针,对照组患者采用开放式留置针,两组患者均采用24G、0.7mm×19mm规格的留置针、6mm×7mm透明敷贴固定、连接输液器均为精密输液器。比较两组患者的一次性穿刺成功率、血液回流污染率、留置针留置时间、静脉炎的发生情况。结果密闭式Y型留置针在穿刺成功率、血液回流污染率上明显优于开放式留置针(P<0.05,P<0.01),在留置时间上也长于开放式留置针(P<0.01),在感染静脉炎方面两者差异无统计学意义(P>0.05)。结论患者外周静脉置管输液时,使用密闭式留置针比开放式留置针穿刺成功率高、脱针/渗漏少、不误伤操作者,更适合临床尤其是住院患者的使用。     

Influence of hemolysis on routine clinical chemistry testing.

BACKGROUND: Preanalytical factors are the main source of variation in clinical chemistry testing and among the major determinants of preanalytical variability, sample hemolysis can exert a strong influence on result reliability. Hemolytic samples are a rather common and unfavorable occurrence in laboratory practice, as they are often considered unsuitable for routine testing due to biological and analytical interference. However, definitive indications on the analytical and clinical management of hemolyzed specimens are currently lacking. Therefore, the present investigation evaluated the influence of in vitro blood cell lysis on routine clinical chemistry testing. METHODS: Nine aliquots, prepared by serial dilutions of homologous hemolyzed samples collected from 12 different subjects and containing a final concentration of serum hemoglobin ranging from 0 to 20.6 g/L, were tested for the most common clinical chemistry analytes. Lysis was achieved by subjecting whole blood to an overnight freeze-thaw cycle. RESULTS: Hemolysis interference appeared to be approximately linearly dependent on the final concentration of blood-cell lysate in the specimen. This generated a consistent trend towards overestimation of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine, creatine kinase (CK), iron, lactate dehydrogenase (LDH), lipase, magnesium, phosphorus, potassium and urea, whereas mean values of albumin, alkaline phosphatase (ALP), chloride, gamma-glutamyltransferase (GGT), glucose and sodium were substantially decreased. Clinically meaningful variations of AST, chloride, LDH, potassium and sodium were observed in specimens displaying mild or almost undetectable hemolysis by visual inspection (serum hemoglobin < 0.6 g/L). The rather heterogeneous and unpredictable response to hemolysis observed for several parameters prevented the adoption of reliable statistic corrective measures for results on the basis of the degree of hemolysis. CONCLUSION: If hemolysis and blood cell lysis result from an in vitro cause, we suggest that the most convenient corrective solution might be quantification of free hemoglobin, alerting the clinicians and sample recollection.     

Influence of needle gauge on in vivo ultrasound and microbubble-mediated gene transfection

Ultrasound and microbubble-mediated gene transfection are potential tools for safe, site-selective gene therapy. However, preclinical trials have demonstrated a low transfection efficiency that has hindered the progression of the technique to clinical application. In this paper it is shown that simple changes to the method of intravenous injection can lead to an increase in transfection efficiency when using 6-MHz diagnostic ultrasound and the ultrasound contrast agent, SonoVue. By using needles of progressively smaller gauge, i.e., larger internal diameter (ID), from 29 G (ID 0.184 mm) to 25 G (ID 0.31 mm), the transfection of a luciferase plasmid (pGL4.13) was significantly increased threefold in heart-targeted female CD1 mice. In vitro work indicated that the concentration and size distribution of SonoVue were affected by increasing needle gauge. These results suggest that the process of systemic delivery alters the bubble population and adversely affects transfection. This is exacerbated by using high-gauge needles. These findings demonstrate that the needle with the largest possible ID should be used for systemic delivery of microbubbles and genetic material.     

比较超声引导下粗针与细针在经皮脾穿刺活检中的应用价值

目的比较超声引导下18G粗针与21G细针脾穿刺活检的安全性和有效性。方法53例行超声引导下脾穿刺活检的患者,局灶性病变35例,弥漫性病变18例。18G粗针组35例应用组织切割针配以自动活检枪;21G细针组18例应用手动活检针。结果46例明确了诊断,7例假阴性,准确率86.8%,2组比较进针次数和诊断准确率均有显著差异（P=0.017,P=0.037）;1例并发出血,2组比较并发症的发生率没有统计学差异。结论18G针和21G针行超声引导下经皮脾穿刺活检均安全。18G粗针活检能够获得较多而完整的组织条,诊断的准确率较高,是获得病理诊断的有效方法。     

Comparison of two blood sampling methods in anticoagulation therapy: venipuncture and peripheral venous catheter

Aim. To compare prothrombin time and activated partial thromboplastin time values in concurrent blood samples obtained by direct venipuncture and from a peripheral venous catheter. Method. Concurrent blood samples obtained from catheters and by direct venipuncture were studied. Venipuncture samples were labelled as the reference (control) group and the peripheral venous catheter samples as the experimental group. A 21‐gauge needle was used in the venipuncture method and 18G, 20G, 22G catheters were used in the peripheral venous catheters method. In each case, after the blood samples were drawn by venipuncture and peripheral venous catheter the needles were drawn out, 1·8 ml of blood was added to 0·2 ml of citrate to give a 2 ml sample. The tube was shaken gently to mix the blood and citrate well. Results. No clinically significant difference between prothrombin time and activated partial thromboplastin time values were seen in the blood samples drawn by venipuncture and peripheral venous catheter methods. Discussion. It is recommended that peripheral venous catheter can be used for patients with high bleeding risk if they have a long hospital stay and frequent blood samples are needed. Relevance to clinical practice. In clinical applications, nurses may prefer the use of peripheral venous catheter to venipuncture both for the comfort of the patients who get anticoagulation therapy and for the prevention of the risks as a result of venipuncture. Application of peripheral venous catheter eliminates the risks of superficial bleeding, irritation, pain and anxiety caused by venipuncture.     

不同型号静脉留置针滴注20％甘露醇的效果比较

目的比较采用不同型号静脉留置针输入20％甘露醇的临床效果。方法采用随机对照研究的方法,将82例需输注20％甘露醇的脑部疾病患者按照静脉留置针的不同型号随机分为观察组（24G,43例）和对照组（22G,39例）,两组均按q．8h～q．12h滴人20％甘露醇125—250ml,每位患者输入4d,采用统一制定的观察记录表记录输注过程中的各项指标,并统计穿刺成功率、静脉炎发生率、针头堵塞率、重新置管率及留置时间。结果不同型号静脉留置针穿刺成功率、重新置管率及针头堵塞率比较,两组差异无统计学意义（x。值分别为2．9823,0．0123,0．0154;P〉0．05）;观察组在留置时间上长于对照组[（89．9902±20．3606）h比（80．2800±23．2790）h],在静脉炎发生率方面低于对照组（20．9％比41．0％）,两组比较,差异有统计学意义（t=2．0147,χ2=3．8970;P〈0．05）。结论临床护理人员对输入20％甘露醇的患者应尽可能选择24G留置针,以减少静脉炎的发生并延长留置时间。     

Effects of syringe material and needle size on the minimum plunger-displacement pressure of arterial blood gas syringes.

We determined the minimum systolic pressures required for blood to enter and begin to displace the plungers of four brands of 3-ml and 5-ml plastic and glass arterial blood gas syringes by combining samples of each syringe size with three sizes of short-beveled needles--25 gauge, 5/8"; 22-gauge, 1"; and 20-gauge, 1 1/2". We measured pressures by use of an arterial-vessel model that incorporated whole human blood and simulated the conditions of a percutaneous arterial puncture. We concluded that all the arterial blood gas syringes that we studied would self-fill in most clinical situations when they were combined with 20- or 22-gauge needles, but that 22-gauge needles with glass syringes were preferable for persons whose systolic pressures were less than 70 mm Hg, for persons in shock, and for persons undergoing CPR. Only glass 3-ml syringes should be used with 25-gauge needles, as two brands of plastic 3-ml syringes with 25-gauge needles required systolic pressures greater than 158 mm Hg and all brands of plastic and glass 5-ml syringes with 25-gauge needles required systolic pressures greater than 247 mm Hg. Because we found no clinical or statistical differences between 20- and 22-gauge needles, we do not recommend use of the larger 20-gauge needle. The syringe-needle combinations that we do recommend should negate the need for, and the potential trauma of, manual aspiration of the syringe plunger.     

Validation of oxygen saturation monitoring in neonates.

BACKGROUND: Pulse oximetry is commonly used to monitor oxygenation in neonates, but cannot detect variations in hemoglobin. Venous and arterial oxygen saturations are rarely monitored. Few data are available to validate measurements of oxygen saturation in neonates (venous, arterial, or pulse oximetric). Purpose To validate oxygen saturation displayed on clinical monitors against analyses (with correction for fetal hemoglobin) of blood samples from neonates and to present the oxyhemoglobin dissociation curve for neonates. METHOD: Seventy-eight neonates, 25 to 38 weeks' gestational age, had 660 arterial and 111 venous blood samples collected for analysis. RESULTS: The mean difference between oxygen saturation and oxyhemoglobin level was 3% (SD 1.0) in arterial blood and 3% (SD 1.1) in venous blood. The mean difference between arterial oxygen saturation displayed on the monitor and oxyhemoglobin in arterial blood samples was 2% (SD 2.0); between venous oxygen saturation displayed on the monitor and oxyhemoglobin in venous blood samples it was 3% (SD 2.1) and between oxygen saturation as determined by pulse oximetry and oxyhemoglobin in arterial blood samples it was 2.5% (SD 3.1). At a Pao(2) of 50 to 75 mm Hg on the oxyhemoglobin dissociation curve, oxyhemoglobin in arterial blood samples was from 92% to 95%; oxygen saturation was from 95% to 98% in arterial blood samples, from 94% to 97% on the monitor, and from 95% to 97% according to pulse oximetry. CONCLUSIONS: The safety limits for pulse oximeters are higher and narrower in neonates (95%-97%) than in adults, and clinical guidelines for neonates may require modification.