Effect of Dexmedetomidine on the Corrected QT and Tp-e Intervals during Spinal Anesthesia

Purpose

The aim of this study is to evaluate the effect of dexmedetomidine on corrected QT (QTc) and Tp-e intervals in patients undergoing spinal anesthesia.

Materials and Methods

We studied 50 patients who were scheduled to undergo spinal anesthesia before orthopedic surgeries. Patients were allocated to receive either an infusion of dexmedetomidine or normal saline after spinal anesthesia.

Results

QTc intervals were significantly prolonged after spinal anesthesia, and the prolonged QTc interval returned to baseline values 10 minutes after either normal saline or dexmedetomidine administration in both groups. The QTc interval values after dexmedetomidine administration were significantly shorter compared to the QTc interval values just before dexmedetomidine administration.

Conclusion

Dexmedetomidine could promote the return of a prolonged QTc interval induced by spinal anesthesia and might be helpful in patients who have a prolonged QTc interval.     

Dexmedetomidine decreases hyperalgesia in neuropathic pain by increasing acetylcholine in the spinal cord

The activation of α2-adrenoceptors has attracted attention as a therapeutic target for neuropathic pain, which remains a clinical challenge. In the present study, we examined the interaction between α2-adrenergic and cholinergic signaling in a rat model of neuropathic pain induced by spinal nerve ligation (SNL). Intrathecal administration of dexmedetomidine, which is a selective α2-adrenoceptor agonist (0.1–1.0 μg), dose-dependently suppressed hyperalgesia in SNL rats but did not alter paw withdrawal thresholds in normal rats. The analgesic effect of dexmedetomidine was abolished by intrathecal pretreatment with idazoxan (30 μg) and atropine (30 μg), which antagonize the α2-adrenoreceptor and muscarinic receptor, respectively. In vivo microdialysis in the lumbar spinal dorsal horn revealed that acetylcholine concentrations increased after dexmedetomidine perfusion (1 μM), but only in SNL rats. The combination of an ineffective dose of intrathecal dexmedetomidine with intraperitoneal donepezil, which is a cholinesterase inhibitor, decreased neuropathic hypersensitivity. These results suggest that plasticity of the spinal noradrenergic–cholinergic axis only occurs in neuropathic pain states. Thus, drug combinations that strengthen the noradrenergic–cholinergic interaction may provide therapeutic benefit in neuropathic pain.     

The dose-dependent study of verapamil and diltiazem on spinal anesthesia in the rat

The aim of this study evaluated the spinal anesthetic effect of verapamil and diltiazem. After rats were injected intrathecally with verapamil and diltiazem, dose–response curves were constructed. We evaluated the potency and duration of verapamil or diltiazem which compared with mepivacaine, a commonly used local anesthetic, in rats. Verapamil, diltiazem and mepivacaine produced a dose-dependent local anesthetic effect as spinal anesthesia. On a 50% effective dose (ED₅₀) basis, the spinal anesthetic effect of verapamil was more potent than diltiazem or mepivacaine (P < 0.01 for each comparison). On an equipotent basis (ED₂₅, ED₅₀, and ED₇₅), the blockade duration of spinal anesthesia caused by diltiazem was longer than that caused by verapamil or mepivacaine (P < 0.01 for each comparison). In summary, verapamil produced more potent spinal blockades, when compared with diltiazem or mepivacaine. Diltiazem demonstrated longer spinal blockades than did verapamil or mepivacaine.     

高龄膝关节置换过程中应用右美托咪啶硬膜外麻醉剂量的选择

背景：高龄膝关节置换过程中硬膜外麻醉是一种常用的麻醉方式。右美托咪啶因具有良好的镇痛效果,被广泛应用于高龄膝关节置换硬膜外麻醉中,但不同的右美托咪啶应用剂量可能会导致不同的效果。 目的：探讨高龄膝关节置换过程中不同剂量右美托咪啶的硬膜外麻醉效果。 方法：从膝关节置换的高龄患者中选择75例进行研究,随机分为右美托咪啶负荷加维持组、右美托咪啶维持组和生理盐水组,每组25例,分别给予小剂量右美托咪啶负荷加维持、右美托咪啶维持、静脉滴注等容量生理盐水。测定3组患者不同时间的血压、心率、镇静/警觉评分以及手术操作遗忘程度,并进行比较,观察时间点包括T0(硬膜外麻醉后),T1(用药后3 min),T2(用药后5 min),T3(用药后10 min),T4(用药后15 min),T5(用药后30 min)。 结果与结论：用药之后,右美托咪啶负荷加维持组和右美托咪啶维持组患者的血压和心率均出现下降,其中右美托咪啶负荷加维持组明显低于右美托咪啶维持组(P < 0.05),且在T3时相最慢,右美托咪啶维持组以T4时相最慢(P < 0.05);用药后5 min,右美托咪啶负荷加维持组、右美托咪啶维持组的镇静/警觉评分均出现下降现象;T3时右美托咪啶负荷加维持组患者出现深度镇静且心率明显下降,需给予阿托品方能改善,T4时右美托咪啶维持组评分最低(P < 0.05),但未出现深度镇静,血压、心率下降程度较右美托咪啶负荷加维持组轻。右美托咪啶负荷加维持组和右美托咪啶维持组、生理盐水组对手术相关操作的完全遗忘程度分别为72%,68%,0%,右美托咪啶负荷加维持组和右美托咪啶维持组均显著高于生理盐水组(P < 0.05),但两组间比较差异无显著性意义(P > 0.05)。表明在高龄患者膝关节置换过程中,予以小剂量右美托咪啶持续泵注硬膜外麻醉可以达到良好的镇痛、镇静效果,并消除患者对手术操作的不良记忆,是一种较为科学的麻醉方式。中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程      

Isobolographic analysis of caramiphen and lidocaine on spinal anesthesia in rats

The aims of the study were to evaluate the spinal anesthetic effect of caramiphen and also assess spinal anesthetic interactions of caramiphen with lidocaine. Lidocaine, a common local anesthetic, was used as control. Dose-dependent responses of intrathecal caramiphen on spinal anesthesia were compared with lidocaine in rats. The interactions of caramiphen with lidocaine were evaluated via an isobolographic analysis. Caramiphen and lidocaine produced a dose-dependent local anesthetic effect as spinal anesthesia. On a 50% effective dose (ED₅₀) basis, the spinal anesthetic effect of caramiphen was more potent than lidocaine (P < 0.01 for each comparison). Co-administration of caramiphen with lidocaine produced an additive effect. Caramiphen and lidocaine are known to have local anesthetic effects as spinal anesthesia in rats. The spinal anesthetic effects of adding caramiphen to lidocaine are similar to the combinations of other anesthetics with lidocaine.     

Intrathecal oxybuprocaine and proxymetacaine produced potent and long-lasting spinal anesthesia in rats

Proxymetacaine and oxybuprocaine were clinically used for topical ocular anesthesia but never for spinal anesthesia, and therefore spinal anesthetic effects of proxymetacaine and oxybuprocaine were performed and compared with bupivacaine and lidocaine. After rats were injected intrathecally with proxymetacaine, oxybuprocaine, bupivacaine, and lidocane, dose–response curves were constructed. We evaluated the potencies (ED₅₀) and durations (time to full recovery) of proxymetacaine and oxybuprocaine on spinal blockades of motor function, proprioception, and nociception and compared with bupivacaine and lidocaine in rats. We found that proxymetacaine and oxybuprocaine acted like bupivacaine or lidocaine and produced dose-related spinal blockades of motor function, proprioception and nociception. On the ED₅₀ basis, the ranks of potencies in motor, proprioception, and nociception were proxymetacaine > oxybuprocaine > bupivacaine > lidocaine (P < 0.01 for the differences). On an equipotent basis (ED₂₀, ED₅₀, ED₈₀), oxybuprocaine and bupivacaine produced similarly longer spinal blockades than did proxymetacaine or lidocaine (P < 0.05 for the differences). Intrathecal proxymetacaine, oxybuprocaine, and bupivacaine also produced longer sensory blockade than motor blockade. These data demonstrated that oxybuprocaine and proxymetacaine produced more potent spinal blockades, when compared with bupivacaine or lidocaine. Oxybuprocaine and bupivacaine with a more sensory-selective action over motor blockade produced longer spinal blockade than did proxymetacaine or lidocaine.     

Effects of spinal anesthesia on resting metabolic rate and quadriceps mechanomyography

Previous work by our group has shown by mechanomyography (MMG) that resting muscle is mechanically active. Ten patients having spinal anesthesia for surgery, which paralyses muscle below the waist, were studied to help determine whether resting-muscle mechanical activity plays a significant role in resting metabolism, and to further determine if the phenomenon is neurally mediated. Resting metabolic rate (RMR) by indirect calorimetry, and mid-anterior thigh MMG by accelerometer, were recorded before and during spinal anesthesia. Spinal anesthesia produced a 25% decrease in oxygen uptake (mean ± standard deviation: pre-spinal 228 ± 76; during spinal 171 ± 67 ml min⁻¹; P < 0.001) and 37% decrease in mean absolute MMG signal amplitude (pre-spinal-anesthetic 10.6 ± 3.9; during spinal: 6.7 ± 3.5 mm s⁻²; P < 0.001). Decreased oxygen uptake in individuals correlated with decreased resting-muscle mechanical activity (R = 0.624; P = 0.05). Paralysis of muscle below the waist reduced RMR and resting-muscle mechanical activity.     

EMG activity in pectoral and femoral muscles during spinal cord cooling in exercising pigeons

Adult domestic pigeons, with thermodes chronically implanted in the vertebral canal, were trained to walk on a treadmill. In the first series of experiments, EMG activity in a pectoral (M. pectoralis) and a femoral muscle (M. biceps femoris) was measured to determine if shivering could occur during exercise. When the spinal cord was cooled (36.2±0.5°C) during exercise (0.6 km/h), pectoral muscle EMG activity increased by 80%, while femoral muscle EMG activity did not change significantly. EMG activity remained unchanged during exercise in control experiments where the spinal cord was not cooled.In the second series of experiments, the spinal cord was first cooled (36.1±0.5°C) for 5 min in resting pigeons and then the treadmill was started. Spinal cord cooling during rest significantly increased pectoral muscle EMG activity but not that of the femoral muscle. Within 1 s after the onset of exercise, EMG activity in the pectoral muscle decreased by 74%.In both series of experiments, shivering was not induced in the femoral muscle. The level of pectoral muscle EMG activity stimulated by spinal cord cooling during exercise in the first series of experiments corresponded to the level to which EMG activity was reduced by exercise during spinal cord cooling in the second series of experiments (192% and 186% in relation to the post-cooling level, respectively).It is concluded that shivering can be induced in the pectoral muscle by spinal cord cooling during exercise in the pigeon. The level of shivering induced in the pectoral muscle is well balanced according to the degree of spinal cord cooling (thermal information) and the running speed of exercise (non-thermal information possibly from active muscles and joints).     

Increase in oxygen consumption induced by selective spinal cord cooling in the exercising pigeon

Six domestic pigeons with chronically implanted spinal thermodes were exercised on a treadmill at neutral ambient temperature. During the exercise the spinal cord was cooled to 34.7±0.4°C (mean±S.E.M.). Oxygen consumption of the pigeons increased from 28.3 ±2.1 to 61.2±3.7 ml·min^–1·kg^–1 due to exercise per se, and superimposed cooling of the spinal cord during exercise induced an additional increase in oxygen consumption to 84.9±4.5 ml·min^–1·kg^–1. The result demonstrates that cooling of the spinal cord elicits shivering in exercising pigeons at thermoneutral conditions.     

Patient education and anesthesia choice for total knee arthroplasty

ObjectivesSpinal anesthesia (SA) for Total Knee Arthroplasty (TKA) may be associated with better patients’ outcomes. This study aims to assess the association between preoperative education about the advantage of SA over general anesthesia (GA) for TKA and the likelihood of patient choice of NA.MethodsPatients undergoing unilateral primary TKA were identified. Type of anesthesia (GA or SA), attendance of the (joints class), patient demographics, ASA status, anticoagulation status, and diagnosis of back problems were recoded. Regression analysis was used to assess the association between the type of anesthesia and attendance of the joints class.Results1010 patients were identified to have unilateral primary TKA. 31% of patients attended the joint class. Patients who attended the joints class were more likely to receive SA when compared to those who did not attend (OR = 1.7, CI: 1.2–2.5, P = 0.004) after adjusting for other variables.ConclusionPreoperative education about advantages of SA may be associated with an increase in patients receiving SA for TKA.Practice implicationsIncrease in patients receiving SA for TKA may improve outcomes.     

右美托咪定在儿童扁桃体手术围拔管期的应用

目的观察右美托咪定在小儿扁桃体、腺样体切除手术术后围拔管期的镇静作用。方法选择择期进行扁桃体、腺样体切除手术的患儿60例,随机分为常规组（A组）和右美托咪定组（B组）各30例;两组均以丙泊酚和瑞芬太尼靶控输注诱导及维持,手术结束时停药,并静注曲马多2mg／kg。B组手术结束前10min静脉注射右美托咪定0．5μg／kg,输注时间10min。两组均等待患儿自然清醒拔管,观察两组生命体征变化、术后睁眼时间、拔管时间以及苏醒期躁动、上呼吸道梗阻、术后恶心呕吐等情况。结果B组拔管时和术后清醒时平均动脉压（MAP）和心率（HR）较A组低,差异有统计学意义（P〈0．05）;B组睁眼时间和拔管时间长于A组,差异有统计学意义（P〈0．05）;A、B组术后上呼吸道梗阻率分别为6．7％和10．O％,术后恶心呕吐发生率为16．7％和13．3％,差异均无统计学意义：B组苏醒期躁动发生率为10．0％,较A组的30．0％低．差异有统计学意义（P〈0．05）。结论右美托咪定在手术围拔管期的应用能较好地用于儿童扁桃体手术术后拔管期的镇静,稳定患儿循环情况,减少苏醒期躁动的发生。     

瑞芬太尼与右美托咪定用于预防全麻苏醒期呛咳反射及血流动力学波动的比较

目的 对比瑞芬太尼靶控输注和单次给予右美托咪定预防全麻苏醒期呛咳反射和稳定血流动力学的效果.方法 选择甲状腺切除手术患者90例,随机分为对照组(C组,n =30)、瑞芬太尼组(R组,n=30)和右美托咪定组(D组,n=30).术中以七氟烷和靶控输注瑞芬太尼维持麻醉.D组于手术结束前10 min经静脉缓慢滴注0.5 μg/kg右美托咪定.手术结束即刻,C组和D组同时停止输注瑞芬太尼;R组维持瑞芬太尼2 ng/mL靶控输注直至拔管结束.记录拔管期间患者呛咳评分、BP、HR、拔管后呼吸频率、镇静评分和咽痛评分.结果 拔管期间呛咳评分为0分(无呛咳)或1分(1次呛咳)的患者的比例在R组(73.3％)显著高于C组(40％)和D组(40％)(P＜0.05);R组MBP显著低于C组和D组(P＜0.05);R组和D组HR均低于C组(P＜0.05).结论 全麻醉苏醒期间,瑞芬太尼靶控输注在预防呛咳反射及血压升高方面效果优于单次给予右美托咪定;两者在稳定心率方面效果相当;拔管后两者均无明显呼吸抑制作用.     

Studies on the ascending pathways from the thermosensitive region of the spinal cord

Summary In young guinea pigs the ascending pathways from the spinal thermosensitive region were studied by means of 1. microelectrode recording and 2. micro-electrocoagulation. In the first series of studies, impulse frequency was recorded from single units of the spinothalamic tract which responded to a temperature rise in the spinal segments C₅-T₂ with an increase of discharge frequency. At a spinal cord temperature of 38–39° C these units showed a firing rate of 1–5 imp./sec; local heating of the spinal cord (dT/dt=0.1° C/sec) to 40–41° C caused an increase in discharge frequency to 20–25 imp./sec. The mean static impulse frequency was 3 imp./sec at a spinal cord temperature of 39° C, and 10 imp./sec at a spinal cord temperature of 42.5° C.In the second series of studies bilateral RF-coagulations were carried out in different sites of the diencephalon. These experiments showed that the ascending fibres from the spinal thermosensitive region connect the thermosensitive spinal region with a hypothalamic temperature control centre.Supported by the Deutsche Forschungsgemeinschaft (Br. 184/10).     

Efficacy of the valsalva maneuver on needle projection pain and hemodynamic responses during spinal puncture

This study evaluated the efficacy of the valsalva maneuver that can induce baroreceptor activation and nociception, on needle projection pain and hemodynamic responses associated with spinal puncture. Ninety adults, ASA physical status I and II undergoing elective surgeries were included. Patients were randomized into three equal groups. Group I (C): control; Group II (B): ball; pressed a rubber ball (attention-diverting method); Group III (V): valsalva; blew into sphygmomanometer tubing and hold the mercury column up to 30 mm Hg for a period of at least 20s. Spinal needle projection pain was graded using numeric rating scale (NRS): 1-10, where scales of 1-3 were rated as mild, 4-6 as moderate, and >6 as severe. Blood pressure and heart rate, five minutes before the procedure, during the spinal puncture and first and third minutes after that, were also recorded. Significant reduction in NRS was observed in the valsalva group compared with the control and the ball groups (p=0.001). There were statistical but no significant clinical differences in mean arterial blood pressure and heart rates between the study groups (P=0.008 and P=0.016 respectively). In conclusion valsalva maneuver can decrease the skin puncture pain associated with spinal needle projection while observing hemodynamic changes.     

右美托咪定改善全麻苏醒期患者血液动力学及 医院感染的疗效观察

目的 分析右美托咪定对全麻苏醒期血液动力学及医院感染的改善效果。方法 选取2016年9月~2017年9月我院收治的86例接受腹腔手术的胆结石患者为研究对象,依据随机数字表法分为观察组和对照组,各43例。对照组患者均接受本院传统的全麻诱导及腹腔手术治疗,观察组在对照组的基础上实施全麻诱导+右美托咪定诱导镇静。比较两组患者术后苏醒时间、躁动率、脉搏指标水平、呼吸道及伤口感染率情况。结果 两组患者手术时间及术后苏醒时间比较,差异无统计学意义（P＞0.05）,观察组患者苏醒期躁动发生率低于对照组,差异有统计学意义（P＜0.05）;观察组患者苏醒期心率、平均动脉压和脉搏血氧饱和度均优于对照组,差异有统计学意义（P＜0.05）;观察组患者苏醒期的医院感染率低于对照组,差异有统计学意义（P＜0.05）。结论 全麻诱导前静脉注射右美托咪定可以有效改善患者的血液动力水平,稳定患者情绪降低躁动比例以及减少术后感染率,值得推广应用。     

右美托咪定通过抑制脊髓星形胶质细胞活化改善甲醛诱导的急性炎性痛

目的探讨右美托咪定(DEX)在0.1%甲醛诱导的急性炎性痛中的作用。方法将30只ICR雌性小鼠随机分成生理盐水对照(NS)组、甲醛(F)组、右美托咪定+甲醛(DEX+F)组。向右后爪足底注射25μl 0.4%甲醛建立小鼠急性炎性痛模型,在甲醛注射前1 h,DEX+F组小鼠腹腔注射DEX,NS组和F组小鼠腹腔注射等体积生理盐水。以小鼠舔咬足累计时间评价自发痛行为。采用免疫组织化学法和Western blotting检测脊髓星形胶质细胞标记物胶质纤维酸性蛋白(GFAP)的表达。结果自发痛评分结果显示,与NS组相比,F组小鼠出现典型的双相痛反应;与F组相比,DEX+F组小鼠的第Ⅰ时相痛(P<0.001)和第Ⅱ时相痛(P<0.001)累计时间明显减少。免疫组织化学结果显示,与NS组相比,F组小鼠脊髓后角GFAP阳性细胞数目明显增多(P<0.001);与F组相比,DEX+F组小鼠脊髓后角GFAP阳性细胞数目明显减少(P<0.001)。Western blotting结果显示,与NS组相比,F组小鼠脊髓GFAP表达明显增加(P<0.05);与F组相比,DEX+F组小鼠...     

Comparison of shivering in man exposed to cold in water and in air

Summary Metabolic rate (M), mean skin temperature ( ) and rectal temperature (Tre) were studied during 2 h exposure to cold in the air (Ta=15–25°C) and in water . From the results, it was possible to draw tentative equations of the metabolic response in transient and steady state as functions of body temperatures: M_air=41,3–57.77 dTsk/dt-5.01 and M_water=M_air+984.15–23.79 Tre. These equations show an important difference between the two groups of experiments: in water, both and Tre are required, whereas suffices in air. This leads to discuss the usage of mean weighted skin temperature and rectal temperature to describe peripheral and central input respectively, specially on man in cold air, in the range of these experiments.     

Long-term continuous spinal Anesthesia in severe tetanus with autonomic disturbance

Summary The mortality rate from tetanus is still high if the disease is accompanied by signs of autonomic nervous system dysfunction. We treated a 75-year-old woman with tetanus and autonomic dysfunction with continuous high spinal anesthesia for 23 days. She recovered. Spinal anesthesia may be a useful adjunct for the treatment of severe tetanus.     

Dexmedetomidine decreases the inflammatory response to myocardial surgery under mini-cardiopulmonary bypass

Cardiopulmonary bypass (CPB) with extracorporeal circulation produces changes in the immune system accompanied by an increase in proinflammatory cytokines and a decrease in anti-inflammatory cytokines. We hypothesize that dexmedetomidine (DEX) as an anesthetic adjuvant modulates the inflammatory response after coronary artery bypass graft surgery with mini-CPB. In a prospective, randomized, blind study, 12 patients (4 females and 8 males, age range 42-72) were assigned to DEX group and compared with a conventional total intravenous anesthesia (TIVA) group of 11 patients (4 females and 7 males). The endpoints used to assess inflammatory and biochemical responses to mini-CPB were plasma interleukin (IL)-1, IL-6, IL-10, interferon (INF)-γ, tumor necrosis factor (TNF)-α, C-reactive protein, creatine phosphokinase, creatine phosphokinase-MB, cardiac troponin I, cortisol, and glucose levels. These variables were determined before anesthesia, 90 min after beginning CPB, 5 h after beginning CPB, and 24 h after the end of surgery. Endpoints of oxidative stress, including thiobarbituric acid reactive species and delta-aminolevulinate dehydratase activity in erythrocytes were also determined. DEX+TIVA use was associated with a significant reduction in IL-1, IL-6, TNF-α, and INF-γ (P<0.0001) levels compared with TIVA (two-way ANOVA). In contrast, the surgery-induced increase in thiobarbituric acid reactive species was higher in the DEX+TIVA group than in the TIVA group (P<0.01; two-way ANOVA). Delta-aminolevulinate dehydratase activity was decreased after CPB (P<0.001), but there was no difference between the two groups. DEX as an adjuvant in anesthesia reduced circulating IL-1, IL-6, TNF-α, and INF-γ levels after mini-CPB. These findings indicate an interesting anti-inflammatory effect of DEX, which should be studied in different types of surgical interventions.     

Measurement and prediction of peak shivering intensity in humans

Prediction equations of shivering metabolism are critical to the development of models of thermoregulation during cold exposure. Although the intensity of maximal shivering has not yet been predicted, a peak shivering metabolic rate (Shiv_peak) of five times the resting metabolic rate has been reported. A group of 15 subjects (including 4 women) [mean age 24.7 (SD 6) years, mean body mass 72.1 (SD 12) kg, mean height 1.76 (SD 0.1) m, mean body fat 22.3 (SD 7)% and mean maximal oxygen uptake (V˙O_2max) 53.2 (SD 9) ml O₂ · kg⁻¹ · min⁻¹] participated in the present study to measure and predict Shiv_peak. The subjects were initially immersed in water at 8°C for up to 70 min. Water temperature was then gradually increased at 0.8 °C · min⁻¹ to a value of 20 °C, which it was expected would increase shivering heat production based on the knowledge that peripheral cold receptors fire maximally at approximately this temperature. This, in combination with the relatively low core temperature at the time this water temperature was reached, was hypothesized would stimulate Shiv_peak. Prior to warming the water from 8 to 20 °C, the oxygen consumption was 15.1 (SD 5.5) ml · kg⁻¹ · min⁻¹ at core temperatures of approximately 35 °C. After the water temperature had risen to 20 °C, the observed Shiv_peak was 22.1 (SD 4.2) ml O₂ · kg⁻¹ · min⁻¹ at core and mean skin temperatures of 35.2 (SD 0.9) and 22.1 (SD 2.2) °C, respectively. The Shiv_peak corresponded to 4.9 (SD 0.8) times the resting metabolism and 41.7 (SD 5.1)% of V˙O_2max. The best fit equation predicting Shiv_peak was Shiv_peak (ml O₂ · kg⁻¹ · min⁻¹)=30.5 + 0.348 ×V˙O_2max (ml O₂ · kg⁻¹ · min⁻¹) − 0.909 × body mass index (kg · m⁻²) − 0.233 × age (years); (P=0.0001; r ²=0.872). Accepted: 7 September 2000