The oxygen delivery response to acute hypoxia during incremental knee extension exercise differs in active and trained males

Background

It is well known that hypoxic exercise in healthy individuals increases limb blood flow, leg oxygen extraction and limb vascular conductance during knee extension exercise. However, the effect of hypoxia on cardiac output, and total vascular conductance is less clear. Furthermore, the oxygen delivery response to hypoxic exercise in well trained individuals is not well known. Therefore our aim was to determine the cardiac output (Doppler echocardiography), vascular conductance, limb blood flow (Doppler echocardiography) and muscle oxygenation response during hypoxic knee extension in normally active and endurance-trained males.

Methods

Ten normally active and nine endurance-trained males (VO_2max = 46.1 and 65.5 mL/kg/min, respectively) performed 2 leg knee extension at 25, 50, 75 and 100% of their maximum intensity in both normoxic and hypoxic conditions (FIO₂ = 15%; randomized order). Results were analyzed with a 2-way mixed model ANOVA (group × intensity).

Results

The main finding was that in normally active individuals hypoxic sub-maximal exercise (25 – 75% of maximum intensity) brought about a 3 fold increase in limb blood flow but decreased stroke volume compared to normoxia. In the trained group there were no significant changes in stroke volume, cardiac output and limb blood flow at sub-maximal intensities (compared to normoxia). During maximal intensity hypoxic exercise limb blood flow increased approximately 300 mL/min compared to maximal intensity normoxic exercise.

Conclusion

Cardiorespiratory fitness likely influences the oxygen delivery response to hypoxic exercise both at a systemic and limb level. The increase in limb blood flow during maximal exercise in hypoxia (both active and trained individuals) suggests a hypoxic stimulus that is not present in normoxic conditions.

     

Why change a good thing? Revisiting the fleur-de-lis reconstruction of the breast

Although the latissimus flap is known for its simplicity and reliability, use of the fleur-de-lis pattern was plagued by undesirable T-shaped donor sites and small breast volumes in thin patients. We report a modified technique for optimal shaping of the standard latissimus with the successful application of a modified fleur-de-lis pattern. Because a "wet" tumescent infiltration was utilized and large amounts of subcutaneous fat were harvested, these changes permitted application to a wide variety of patients, with generous breast volumes reducing the size of the implant placed and resulting in excellent donor-site scars.This is a retrospective cohort study of 53 delayed or immediate reconstructions performed consecutively by the principal author (M.E.A.) on 48 patients at a university-based, urban hospital. Each case was analyzed between April of 1995 and February of 1999, with a follow-up from 2.5 to 44 months. All patients underwent injection of tumescent solution into the subcutaneous plane and harvest of large amounts of subcutaneous fat with the neurologically intact latissimus muscle. The last 25 reconstructions utilized the modified fleur-de-lis skin pattern, an inferiorly based vertical limb and replacement of skin deficiency in both axes.Of 11 perioperatively irradiated patients, none required skin grafting, whereas 6 percent of all native mastectomy flaps were grafted. There was one instance of minor distal tip flap necrosis in a nonirradiated patient. No implants became infected or were extruded. Donor sites were without wound complications and unveiled a 16 percent overall seroma rate.Through selective addition of harvested tissue, this modified technique, particularly the fleur-de-lis pattern, permits improved volume and projection in the inferior pole. The T-shaped donor-site closure is not only acceptable, but is also desirable, with reduced wound tension and minimization of dog-ear formation. With a relative paucity of complications, this conceptually ideal modification is technically simple and aesthetically comparable to our transverse rectus abdominis muscle flap results.     

The synthesis of short- and medium-chain-length poly(hydroxyalkanoate) mixtures from glucose- or alkanoic acid-grown <Emphasis Type="Italic">Pseudomonas oleovorans</Emphasis>

Pseudomonas oleovorans NRRL B-778 accumulated mixtures of poly-3-hydroxybutyrate (PHB) and medium-chain-length poly(hydroxyalkanoates) (mcl-PHAs) when grown on glucose, octanoic acid or oleic acid, whereas growth on nonanoic acid or undecanoic acid resulted in copolymers of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-co-HV). Acetone fractionation verified the presence of PHB/mcl-PHA mixtures. The acetone-insoluble (AIS) fractions of the polymers derived from glucose (PHA-glucose), octanoic acid (PHA-octanoic) and oleic acid (PHA-oleic) were exclusively PHB while the acetone-soluble (AS) fractions contained mcl-PHA composed of differing ratios of 3-hydroxy-acid monomer units, which ranged in chain length from 6 to 14 carbon atoms. In contrast, both the AIS and AS fractions from the polymers derived from nonanoic acid (PHA-nonanoic) and undecanoic acid (PHA-undecanoic) were composed of comparable ratios of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). The unfractionated PHA-glucose, PHA-octanoic and PHA-oleic polymers had melting temperatures (T _m) between 177 and 179°C, enthalpies of fusion (ΔH _f) of 20 cal/g and glass transition temperatures (T _g) of 3–4°C. This was due to the large PHB content in the polymer mixtures. On the other hand, the PHA-nonanoic and PHA-undecanoic polymers had thermal properties that supported their copolymer nature. In both cases, the T _m values were 161°C, ΔH _f values were 7cal/g and T _g values were −3°C. Journal of Industrial Microbiology & Biotechnology (2002) 28, 147–153 DOI: 10.1038/sj/jim/7000231 Received 30 July 2001/ Accepted in revised form 04 November 2001     

The clinical outcome of abdominoplasty performed under conscious sedation: increased use of fentanyl correlated with longer stay in outpatient unit

The objective of this study was to present data supporting the effectiveness of performing mini and full abdominoplasties under conscious sedation with local anesthesia. The authors performed 20 such operations between 1994 and 1996, using a combination of midazolam (Versed) and fentanyl instead of general anesthesia (without an anesthesiologist or nurse anesthetist present). At 5- to 10-minute intervals, the surgeon would order the injection of 1 cc (1 mg/ml) of midazolam and 1 cc (50 microg/ml) of fentanyl. The amount and the interval varied based on the patient's level of sedation. Blood pressure, oxygen saturation, and the patient's response to verbal and physical stimuli were used to assess the sedation level. Average operating time was 147.5 minutes, and mean length of stay in the outpatient recovery room was 235.5 minutes. The average amounts of midazolam and fentanyl used were 9.4 mg (6 to 12.5 mg) and 532 microg (300 to 800 microg), respectively. The average age of patients in this group was 41.7 years (28 to 63 years). Nineteen patients were discharged the same day. There were no surgical complications and no complication related to the sedation (such as respiratory or cardiac compromise). The average follow-up of these patients was 1.2 years (range, 3 to 21 months). Correlation coefficient rates and regression rates were calculated. The longer the procedure, the more midazolam was used intraoperatively (r = 0.5, p = 0.03). However, there was no correlation between the length of the procedure and the amount of fentanyl used. Rather, there was a positive correlation demonstrating that patients who received more fentanyl stayed longer in the outpatient recovery area after surgery (r = 0.6, p < 0.01). The age of the patients and the amount of midazolam did not correlate with how fast they went home from the outpatient area. In conclusion, full and mini abdominoplasties can be performed safely using conscious sedation without compromising patient care or surgical outcome. Second, the survey revealed that patient satisfaction with these procedures performed under conscious sedation was very high. Third, the increased use of fentanyl, not midazolam, resulted in a longer stay in the outpatient unit after surgery. Nausea is a known side effect of narcotic analgesics, and it correlated with a higher dose of fentanyl administration in the patients. The authors are now routinely administering a dose of either droperidol or odansetron (Zofran) preoperatively (both are antiemetics). Previously, the ratio of midazolam and fentanyl injection was 1:1 every 5 to 10 minutes, but now it is 2: 1 to 4: 1 every 5 to 10 minutes (a smaller dose of fentanyl is administered). The conscious sedation technique should be an option for patients and plastic surgeons in academic and community hospital settings if they desire.     

Optimization of conscious sedation in plastic surgery.

The administration of conscious sedation by the plastic surgeon must be safe, efficient, and consistent. In the proper setting, with trained staff and appropriate backup, conscious sedation can allow optimal patient satisfaction with expedient recovery in addition to cost containment. The highly effective local anesthesia afforded by dilute, high-volume ("tumescent") infiltration extends the use of conscious sedation to cases previously performed under general anesthesia or deep sedation. The purpose of this analysis was to identify variables in conscious sedation that affect traditional outcome parameters in ambulatory surgery, particularly the duration of recovery and adverse events such as nausea and emesis. All perioperative and operative records of 300 consecutive patients having plastic surgical procedures under conscious sedation were carefully reviewed. Patients were ASA class I or II by requisite. Conscious sedation followed a standardized administration protocol, using incremental doses of two agents: midazolam (0.25 to 1 mg) and fentanyl (12.5 to 50 mcg). A subset of patients received preoperative oral sedation. Multivariate statistical analysis was conducted using SPSS 8.0 for Windows (SPSS Inc., Chicago, Ill.). Of the 300 patients, same-day discharge was intended for 281. Eight procedure categories were defined. No anesthetic complications occurred. As expected, recovery time was significantly correlated with the duration and type of procedure (p < 0.001) and the total dosage of both intraoperative sedative agents (p < 0.001). Interestingly, a negative correlation with advancing age existed (p < 0.001), likely reflecting the significantly higher intraoperative sedative dosing in younger patients (p < 0.001). When controlled for the effects of procedure duration and intraoperative sedative dosing, two other variables-use of preoperative oral sedation and postoperative nausea/emesis-significantly lengthened recovery time (p = 0.0001 for each). Fifteen unintended admissions occurred secondary to nausea, prolonged drowsiness, or pain control needs. Conscious sedation is an effective anesthetic choice for routine plastic surgical procedures, many of which would commonly be performed under general anesthesia. In our experience with a carefully structured and controlled conscious sedation protocol, the technique has proven to be safe and effective. This analysis of outcome parameters identified two important and potentially avoidable causes of recovery delay following conscious sedation-oral premedication and nausea/emesis. Nausea and emesis were particularly problematic in that they were responsible for 11 of 15 (73 percent) unintended admissions. Preoperative sedation is valuable in certain circumstances, and its use is not discouraged; however, its benefits must be weighed against its unwanted effects, which can include a prolongation of recovery.     

Evolution of anaerobic ciliates from the gastrointestinal tract: phylogenetic analysis of the ribosomal repeat from Nyctotherus ovalis and its relatives

The 18S and 5.8S rDNA genes and the internal transcribed spacers ITS-1 and ITS-2 of ciliates living in the hindgut of frogs, millipedes, and cockroaches were analyzed in order to study the evolution of intestinal protists. All ciliates studied here belong to the genus Nycrotherus. Phylogenetic analysis revealed that these ciliates from a monophyletic group that includes the distantly related anaerobic free-living heterotrichous ciliates Metopus palaeformis and Metopus contortus. The intestinal ciliates from the different vertebrate and invertebrate hosts are clearly divergent at the level of their rDNA repeats. This argues for the antiquity of the associations and a predominantly vertical transmission. This mode of transmission seems to be controlled primarily by the behavior of the host. The different degrees of divergence between ciliates living in different strains of one and the same cockroach species most likely reflect the different geographical origins of the hosts. In addition, host switches must have occurred during the evolution of cockroaches, since identical ciliates were found only in distantly related hosts. These phenomena prevent the reconstruction of potential cospeciation events.      

我国巴拉巴按蚊形态描述

白踝按蚊种团是由很多形态近似的蚊种组成,其中巴拉巴按蚊和白踝按蚊均为东南亚一带的重要传疟媒介。我国过去资料均记载为白踝按蚊,但未从形态上详细鉴定。为了确定该种的分类地位,1963年作者等在海南岛万宁县兴隆附近山林区采集“白踝按蚊”全套标本10批共150多套,1971年后从云南省采集少数标本进行形态鉴定,发现其与Colless(1956,1957)所描述的白踝按蚊Anopheles leucosphyrus leucosphyrus Donitz(1901)有很明显的差别,而与巴拉巴按蚊A.balabacensis balabacensis Balsas(1936)除某些特征略有差异外,余均完全一致。按Colless的分类法,过去我国记载的“白踝按蚊”,应鉴定为巴拉巴按蚊A.balabacensis balabacensis Baisas。