Duration of apnoea in anaesthetized children required for desaturation of haemoglobin to 95%: comparison of three different breathing gases

In this study, we compared three gas compositions to determine if the duration of apnoea for Spo₂ to decrease is proportionate to the oxygen fraction of the gas prior to apnoea. Twenty-five patients ASA physical status 1–2 aged two months to 12 years were included in the study. Anaesthesia was induced via a mask with 5% sevoflurane and 66% N₂O in oxygen. After paralysis with vecuronium (0.12 mg·kg^?1, i.v.) the trachea was intubated and anaesthesia was maintained with sevoflurane and N₂O in oxygen. When cardiovascular stability was obtained, the patient was randomly set to breathe one of three gas compositions: 1. oxygen (Fio₂ 1.0), 2. N₂O/O₂ (Fio₂ 0.4), and 3. air/O₂ (Fio₂ 0.4). All three gas compositions included 2–4% of sevoflurane to maintain anaesthesia. After more than eight min of each gas breathing, apnoea was begun by disconnecting the breathing circuit from the tracheal tube. The time from the start of apnoea (Spo₂ 100%) to Spo₂ of 95% (T₉₅) was measured. T₉₅ measured after breathing N₂O/O₂ and air/O₂ were 34.6 ± 5.7 and 28.8 ± 4.7% of that measured after oxygen breathing (P < 0.001 vs oxygen breathing, P < 0.001 vs oxygen and N₂O/O₂ breathing), respectively. Preoxygenation before intubation was validated to delay the haemoglobin desaturation brought about by apnoea. An induction technique using a low Fio₂ will allow rapid haemoglobin desaturation.     

Relationship between glycosylated haemoglobin and mean plasma glucose concentration in cystic fibrosis.

BACKGROUND: HbA(1c) is recommended for monitoring glycaemic control in people with cystic fibrosis-related diabetes (CFRD). However the relationship between HbA(1c) and mean plasma glucose concentration (MPG) has not been established in CFRD, as in other forms of diabetes mellitus. METHODS: 20 people (13 male, 29.7+/-8.8 years, 10 CFRD) with cystic fibrosis (CF) underwent HbA(1c) measurement and 48 h continuous glucose monitoring for estimation of MPG. The relationship between HbA(1c) and MPG was established and compared to the reported relationship for type 1 diabetes. RESULTS: HbA(1c) was strongly correlated with MPG (R(2)=0.888, p<0.0001) in CF. The relationship of MPG to HbA(1c) was described by the equation MPG=(1.47xHbA(1c))-1.15, giving a 1.47 mmol L(-1) change in MPG per 1% change in HbA(1c). This equation predicts that MPG in people with CF and HbA(1c) <7.0% will be similar to MPG in people with type 1 diabetes who achieve the same HbA(1c) target. CONCLUSIONS: These results imply that HbA(1c)<7.0% will predict good blood glucose control in CF as in type 1 diabetes. However, although HbA(1c) predicts complications in type 1 diabetes, further studies are required to establish the relationship between HbA(1c) and diabetic complications in people with CFRD.     

Circulatory effects of somatostatin in anaesthetized dogs.

Five anaesthetized dogs were given 20 infusions of 1--9 min duration of somatostatin in a dosage of 0.2--15 micrograms.kg-1.min-1. Cardiac output was measured by thermodilution. Electromagnetic blood flow measurements were simultaneously performed in the hepatic artery proper, the left gastric artery, the superior pancreatico-duodenal artery, the superior mesenteric artery and in the portal vein. Mean arterial blood pressure was recorded continuously. Somatostatin reduced all splanchnic blood flows measured by 15--35%, except for the hepatic artery flow, which was increased by 5% or unaffected. Cardiac output and mean arterial pressure were unchanged. Somatostatin was thus demonstrated to exert a specific vasoactivity in the splanchnic area without influencing central circulation. It is suggested that somatostatin acts directly on the vascular smooth muscle.     

不同血浆代用品术前急性超容血液稀释可行性的比较

目的比较不同血浆代用品术前急性超容血液稀释(AHHD)的可行性.方法70例ASAⅠ～Ⅱ的病人随机分成四组,羟乙基淀粉组(H组,n=20)、琥珀酰明胶组(G组,n=20)、聚明胶肽组(P组,n=20)和平衡液组(R组,n=10).全麻诱导和气管插管后分别在20～30 min内输入6%羟乙基淀粉液(200/0.5)、4%琥珀酰明胶、5%聚明胶肽和乳酸林格氏液20 ml/kg,于AHHD前、AHHD完成即刻和AHHD后30 min采桡动脉血3ml立即测定激活全血凝固时间(ACT)、血栓弹力图(TEG)各参数[最大振辐(MA)、反应时间(R)、血凝块形成时间(K)]、血气和电解质.每10min记录心率(HR)、平均动脉压(MAP)和中心静脉压(CVP).结果R组扩容率低于其它三组(P＜0.01),而其它三组间差异无显著性(P＞0.05).H、G、P组AHHD完成即刻CVP较AHHD前均升高(P＜0.01).P组AHHD后30 min血浆K+浓度较AHHD前升高(P＜0.01),AHHD完成即刻及AHHD后30 min H组和G组血浆Ca2+浓度较AHHD前下降(P＜0.05或0.01),但均在正常范围内.AHHD完成即刻和AHHD后30min H组MA较AHHD前及R组均降低(P＜0.05或0.01).AHHD前后各组间pH、HCO3、R、K和ACT差异均无显著性(P＞0.05).结论羟乙基淀粉、琥珀酰明胶和聚明胶肽均较平衡液更适宜用于术前AHHD;6%羟乙基淀粉20 ml/kg快速输入可抑制血小板功能,不宜用于有凝血功能障碍者;聚明胶肽在扩容的同时可使血钾增高,但在正常范围内.     

Effect of indomethacin on renal function in anaesthetized dogs

The inhibitory action of indomethacin administered as a single-dose injection (4 mg/kg) was examined under general anaesthesia in dogs, moderate volume expansion having been induced with physiological saline infusion. At 20 to 30 min after the administration of indomethacin, excretion of Na and water showed a fall of the same extent, GFR remaining stable and the effective plasma flow (C_PAH) declining. RBF estimated by the⁸⁶Rb method decreased from 411±96 ml/min/100 g to 292±±53 ml/min/100 g (p<0.01). This fall was coupled with an intrarenal redistribution of blood flow. While the cortical fraction of renal blood flow increased from 79% to 83.9% (p<0.001), its outer medullary fraction decreased from 17% to 13.2% (p<0.001) and its inner medullary fraction from 4.0% to 2.8% (p<0.05). The renal, primarily the medullary, vasculature is assumed on these grounds to be under the influence of a continuous secretion of prostaglandins which thus seem to be involved in the physiological control of intrarenal distribution of blood flow and of sodium and water excretion.     

Effect of althesin on renal perfusion in anaesthetized dogs

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - Since Althesin affects not only the systemic circulation but also certain regional blood flows autoregulated by intrinsic...     

Online measurement of haemoglobin concentration.

BACKGROUND: Regular monitoring of haemoglobin in chronic haemodialysis patients is essential to ensure that targets for anaemia management are consistently achieved. Repeated blood sampling can be time consuming, invasive and, for pragmatic reasons, only infrequently performed, often delaying therapeutic change. On-line optical continuous monitoring of the haemoglobin concentration would allow non-invasive assessment of haemoglobin, and immediate therapeutic changes could be implemented, thereby improving the efficiency of anaemia management. This study aimed to evaluate the use of on-line haemoglobin concentration measurement. METHODS: Eleven dialysis monitors (Integra Hospal) were calibrated using at least five haemoglobin samples spread over at least 4 g/dl. Optical measurement of haemoglobin concentration is already incorporated into the dialysis monitor to allow the study of relative blood volume. Fifteen patients were studied with paired haemoglobin measurements (i.e. dialysis monitor value and conventional laboratory assessment) taken at intervals over 7 months (mean 11.0+/-0.28 g/dl, range 7.5-14.8). RESULTS: Haemoglobin measured by Hemoscan correlated well with the laboratory measurements (r2 = 0.83, P<0.0001), indicating that the machine values are broadly comparable with laboratory figures. There was a mean underestimate of haemoglobin by Hemoscan of 0.34%. There was no significant deterioration in the quality of this correlation over the study period (r2>0.8). CONCLUSION: The ability of the dialysis monitor to measure the optical concentration of haemoglobin compared with conventional laboratory assessment is both precise and accurate. Regular on-line assessment of haemoglobin may allow more proactive micromanagement of renal anaemia, with a reduction in the time taken to achieve clinically important targets and give early warning of suboptimal response to treatment.     

The effect of dopamine or dobutamine on plasma concentration of magnesium in dogs

Plasma magnesium (Mg) concentration of dogs was determined with atomic absorption spectrophotometry during the infusion of dopamine (DOA) or dobutamine (DOB). Other electrolytes were also measured with same samples. Normoventilation was maintained during this experiment in order to avoid the respiratory interference. DOA 15-20 micrograms.kg-1.min-1 decreased Mg concentration significantly. DOB 5-20 micrograms.kg-1.min-1 did not change Mg concentration. Potassium (K) values were almost constant during infusion of both drugs, but DOB reduced K concentration at the dose of 20 micrograms.kg-1.min-1. Ionized calcium ion tended to decrease in DOA and to increase in DOB while the dose of the catecholamines was increased. These were not significant changes. These changes of concentration returned to control values 1 hour after stopping drug administrations. We speculate that beta-receptor, especially beta 2-receptor stimulation by DOA is responsible for the decrease of Mg in the mechanism of Mg uptake into cells of such tissues as liver or muscle.     

Effects of plasma substitutes on hemostasis

OBJECTIVE: Data synthesis on haemostasis effects of cristalloids and colloids and clinical implications for their use for plasma volume replacement. DATA SOURCES: Data were searched in the Medline database from 1954 to 2000 using the following key-words: cristalloids, colloids, albumin, gelatin, dextran, hydroxyethyl starch, haemostasis, von Willebrand disease, haemodilution. DATA EXTRACTION: Publications from 1954 to 1990 were selected depending on the quality of their methodology. Most of articles published after 1990 and all types including case report were accepted. DATA SYNTHESIS: Cristalloids induces a moderate hypercoagulable state with 10 to 30% haemodilution. Hypocoagulation is observed above 50% haemodilution. Albumin does not impair hemostasis except with a 50% or more haemodilution where hypocoagulation is observed. Dextran dramatically impairs haemostasis and fibrinolysis. With increasing dose, a progressive decrease of all von Willebrand multimers, mostly the largest, is observed. Till 50% haemodilution, gelatin has a moderate impact on hemostasis, but platelet aggregation is moderately modified. However this moderate impairment of haemostasis may potentiate the haemostatic effect of other colloids when used in association with gelatin. More than 30% haemodilution with hydroxyethyl starch (HES) has a serious effect in vitro on platelet function and fibrinoformation. In most studies in human, less than 20 ml.kg-1 plasma volume replacement has no clinical impact, but in some evaluations postoperative bleeding is more important with HES, particularly HES 450, in comparison to other colloids. With HES 450 and HES 200 highly substituted (0.6 of degree of substitution) intravascular cumulation of large molecules leads to type I von Willebrand syndrome when doses overtake 80 ml.kg-1. Dextran and HES are prohibited in patients with impaired haemostasis due to congenital disease (haemophilia and von Willebrand disease) or acquired defect (thrombocytopenia). Caution is required in patients with renal failure or receiving antithrombotic or non-steroidal anti-inflammatory agents. Patients without a haemorrhagic diathesis must not received more than 1.5 g.kg-1.j-1 of dextran and restrictive conditions of use must be respected with HES. CONCLUSION: Except isotonic cristalloids, all colloids induce haemostastic changes particularly for haemodilution over 30%. Effects are more pronounced with HES and dextran.     

Atrioventricular conduction during adenosine-induced hypotension in dogs anaesthetized with sevoflurane

We have studied the effects of adenosine-induced hypotension on A-H interval (atrioventricular (AV) nodal conduction time during sinus rhythm), St-H interval (intra-atrial plus AV nodal conduction time during atrial pacing), H-V interval (His-Purkinje conduction time) and H-S interval (total ventricular conduction time) by His-bundle electrocardiography in addition to surface electrocardiogram during both sinus rhythm and atrial pacing in nine dogs anaesthetized with 1 MAC of sevoflurane. Stepwise increases in infusion rates of adenosine to 0.1, 0.3, 0.5 and 1.0 mg kg-1 min-1 produced a dose-related decrease in mean arterial pressure from 91 (6) to 38 (2) mm Hg. Adenosine significantly increased the A-H interval at infusion rates of 0.5 mg kg- 1 min-1 and above, and the St-H interval at 1.0 mg kg-1 min-1. The H-V and H-S intervals remained unchanged. Heart rate decreased significantly only at 1.0 mg kg-1 min-1 with a significant increase in the PR interval. Adenosine-induced hypotension did not have deleterious effects on AV conduction times and the surface electrocardiogram in dogs anaesthetized with 1 MAC of sevoflurane. This may indicate that the effects of adenosine on AV conduction were small and therefore are unlikely to be a contraindication to the use of adenosine for inducing hypotension in patients with initially normal conduction during sevoflurane anaesthesia.      

Importance of the preoperative haemoglobin concentration in arterial surgery

A study of reconstructive operations for ischaemia of the legs showed a correlation between a high preoperative haemoglobin level and early postoperative reocclusion. The mean preoperative haemoglobin level of patients with early reocclusion (165 +/- 3 g/l, SEM) was significantly higher (p less than 0.001) than that of patients who did not reocclude (153 +/- 3 g/l). There was no significant difference in the total serum protein concentrations, suggesting that dehydration was not the cause of the difference observed in haemoglobin concentration. The mechanism may be the lower flow rate associated with the higher haemoglobin content and increased blood viscosity.     

急性代谢性酸中毒和肾上腺素对血浆钾离子浓度的影响

报告两种实验性代谢性酸中毒以及外源性肾上腺素对血浆钾离子浓度的影响。静脉输入２Ｍ乳酸溶液造成酸中毒（ｐＨ７．００）时对血钾水平的影响不明显（从３．３４±０. ２７升至３．７１±０．４０ｍｍｏｌ／Ｌ，Ｐ＞０．０５），而输入 ２Ｍ盐酸造成同样程度的酸中毒则引起血钾水平明显升高（从 ３． ７８± ０．４９升至 ４． ５８±０．５８ｍｉｎｏｌ／Ｌ，Ｐ＜０．０５）。外源性肾上腺素在酸中毒环境下对血钾浓度影响不明显，而在对照组可引起血钾浓度的降低。     

Myocardial damage in coronary artery bypass surgical patients anaesthetized with two anaesthetic techniques: a random comparison of halothane and enflurane

Fifty patients with ischaemic heart disease scheduled for coronary artery bypass surgery received either an enflurane or a halothane anaesthetic. The anaesthetic techniques were randomly assigned to the patients and consisted of induction with diazepam 0.5 mg·kg^-1 and pancuronium 0.1 mg·kg^-1 supplemented by nitrous oxide and oxygen (50:50). Enflurane in dosages of 0.5–1.5 volumes per cent and halothane 0.3–0.7 volumes per cent were administered to Group E (25 patients) and Group H (25 patients), respectively. The inhalation drug dosage was varied to maintain heart rate and systemic blood pressure within predetermined limits. The two patient groups (E and H) were compared with regard to myocardial damage (determined electrocardiographically and enzymatically) as well as by haemodynamic changes and adjuvant cardiovascular drug therapy. One patient in group H sustained a postoperative infarction detected by electrocardiogram and sustained CK MB release. There was no other unequivocal electrocardiographic evidence of myocardial infarction in either group and the myocardial damage estimated from CK MB curves was remarkably low and similar in both anaesthetic groups. Myocardial damage was estimated by CK MB maximum release (CK MB MAX) of 8.1 ± 1.00IU/1 (Group E), 7.8 ± 1.32IU/I (Group H), by area under the CK MB disappearance curve (CK MB AREA) of 144 ± 21.9 IU/1 x hr (Group E), 173 ± 32.9 IU/1 x hr (Group H), and by the accumulated CK MB or CK MB damage size (CK MB DS) of 10.S±1.79IU/1 (Group E), 10.3 ± 2.26 IU/1 (Group H). There was no release of CK MB before cardiopulmonary bypass in either group. There was no statistically significant difference between the two groups for myocardial damage, haemodynamics or adjuvant drug interventions. There was a trend toward greater use of vasodilators in Group H than in Group E. It is concluded that enflurane and halothane are associated with equally low levels of myocardial damage when used for anaesthesia in patients with ischaemic heart disease. The release of CK MB occurred following cardiopulmonary bypass and probably represents imperfect myocardial preservation. Patients with severely impaired ventricular function were not studied, and in these patients enflurane and halothane must be used judiciously.     

Copper in seminal plasma: comparison of two processing methods for atomic absorption spectrophotometry

Fifty-three randomly selected seminal plasma samples were assayed for copper by atomic absorption spectrophotometry. All the samples had undergone two accepted processing methods--wet oxidation and dilution. The results were compared, and a highly significant difference was seen (p less than 0.001). The dilution method gave the better reading and was simpler in processing. The author recommends the dilution method for elemental study in seminal plasma by using atomic absorption spectrophotometry.