THE INFLUENCE OF CAPTOPRIL AND NALOXONE ON THE VALSALVA MANOEUVRE AND SYSTOLIC TIME INTERVALS IN HEALTHY VOLUNTEERS

1. The aim of the study was to ascertain whether the inhibition of the sympathetic nervous system by angiotensin-converting enzyme (ACE) inhibitors is mediated by endogenous opioids. Naloxone was used to evaluate the effects of the latter on systolic time intervals (STI) and Valsalva manoeuvre-induced blood pressure and heart rate changes. 2. Baseline recordings were done in 12 healthy male volunteers and repeated 2h after oral administration of 75 mg of captopril and again after naloxone 0.4 mg/kg was administered intravenously over 10 min. 3. After captopril there was a significant reduction in systolic (P<0.02) and mean blood pressure (P<0.04) without any changes in heart rate. Furthermore, captopril increased the Valsalva ratio (P<0.06) but did not influence inotropism as indicated by STI. Naloxone did not influence any of these findings. 4. The changes in the Valsalva ratio after captopril were mediated by an increase in the maximum bradycardia in nine of the 12 subjects. 5. The results indicate that endogenous opioids do not play a role in the putative sympatholytic effect of ACE inhibition.     

To clamp or not to clamp: Inflow occlusion during liver resection

Aim: To review the evidence in using inflow occlusion during liver resection. Other strategies to minimize the untoward effects of inflow occlusion will also be discussed. Methods: Randomized trials evaluating the use of inflow occlusion in hepatectomy and strategies to minimize its associated adverse effects were reviewed in this article. Recent experience showing comparable operative outcomes without the use of portal clamping was also described. Results: Results from randomized trials and meta‐analyses were not conclusive on the benefits of routine inflow occlusion during liver resection. Intermittent inflow occlusion and ischaemic preconditioning had been found to be effective in reducing ischaemic–reperfusion injury to remnant liver. With refined operative techniques and better instruments, routine inflow occlusion in liver resection can now be safely avoided. Conclusion: Vascular inflow occlusion is an important armamentarium during liver resection, but it should not be used indiscriminately. With refined techniques and better instruments, hepatectomy can be performed safely without the need for routine inflow occlusion.     

Autonomic cardiovascular responses in antecedent poliomyelitis

Autonomically mediated cardiovascular responses were evaluated in 20 subjects with antecedent poliomyelitis and compared to data from an age- and sex-matched control group. The polio subjects had a lower heart rate response to the Valsalva manoeuvre but the same respiratory sinus arrhythmia as the controls. From this it is concluded that the polio subjects had a normal vagal function. The polio subjects had a greater initial heart rate increase but the same blood pressure response to the orthostatic position as the controls. This indicates a normal function of the sympathetic nerves. The greater heart rate increase is most likely caused by a displacement of blood to the legs because of muscle atrophy. The polio subjects had a smaller blood flow increase as an initial response to an isometric handgrip than the controls. This might be attributed to a reduced beta-adrenergic vasodilation, possibly due to a reduced central vasomotor drive. It is concluded that subjects with antecedent poliomyelitis have no significant dysfunction of the peripheral autonomic nerves. Thus, there is no deterioration of the peripheral autonomic nerve function in parallel with the progressive muscle atrophy and paralysis earlier described in post-polio subjects.     

The Valsalva manoeuvre--cardiovascular effects and performance technique: a critical review

Variations in the technique of the Valsalva manoeuvre (VM) have been shown to greatly influence the pattern of cardiovascular response (CVR) to the test. Intra-strain tachycardia, post-strain bradycardia, Valsalva ratio, and baroreflex sensitivity decrease in proportion to an increase in lung volume and a decrease in strain pressure at VM. In conditions of completely expanded lungs and low strain pressure many subjects reveal an intra-strain bradycardic response to VM instead of the usual tachycardic one. Intra-strain arterial hypotension and post-strain hypertension decrease with decrease in strain pressure. The changes in heart rate and blood pressure during an expiratory VM are greater than the responses observed during completition of an inspiratory VM. The rate of the deep inspiration prior to strain has an impact particularly on phase I of the VM. The magnitude of the CVR correlates with the strain duration, particularly at high levels of strain pressure, and depends on the baseline level of the cardiovascular parameters and their variations. The paper discusses the possible mechanisms of different CVRs to variations in the technique of the VM. Some practical recommendations are suggested.     

Peripheral pulse pressure responses to postural stress do not reflect those at the carotid artery

Objective: Interpretation of baroreflex cardiovascular control requires accurate assessment of pulse pressure (PP) in central arteries under conditions of varying systemic or hydrostatic pressure. The objective of this study was to examine whether changes in PP during postural stress were similar in the peripheral versus carotid arteries. Design: Protocol A: Pulse pressure was measured in both the left (Millar tonometer) and right (Colin Pilot) radial arteries, and in the finger (Finapres) in seated subjects (n = 7) who performed Valsalva's manoeuvre. Protocol B: PP was measured from the carotid (Millar tonometer), and from the finger and wrist kept at the level of the carotid artery, during supine and 60° head‐up postures. Results: Protocol A: Pulse pressures during Valsalva's manoeuvre were highly correlated between all devices (r = 0·6–0·8). Protocol B: compared with supine, PP was reduced in both the finger and wrist during head‐up‐tilt (HUT) (P<0·05), but not in the carotid artery. Conclusions: During Valsalva manoeuvers the Millar and Colin tonometers similarly tracked PP over a wide range of rapidly changing pressures. This observation provided confidence for the further use of the hand‐held device for central measurements during changes in posture. The results from Protocol B indicate that peripheral PP measurements are not suitable surrogates for carotid pulse pressures during HUT.     

Incorrect instruction in the use of the Valsalva manoeuvre for paroxysmal supra-ventricular tachycardia is common

Objective: Success rates for the Valsalva manoeuvre (VM) in treatment of paroxysmal supraventricular tachycardia (SVT) vary with performance technique. This study aimed to assess whether ED doctors instruct their patients to perform the recommended VM technique (supine position for 15 s). Methods: A multicentre, observational study of 35 ED registrars and 17 emergency physicians. Each doctor was asked to describe how he/she would instruct a patient in SVT to perform the VM. Results: Only five (9.6%) doctors would position their patient correctly and 31 (59.6%) would incorrectly instruct their patient to assume a sitting or semirecumbent position. Only five (9.6%) doctors would give specific instructions to blow for at least 15 s and 34 (65.4%) would instruct their patient to blow ‘as long as you can’. Only four (7.4%) doctors would use a sphygmomanometer to measure intrathoracic pressure during the VM. There were no significant differences (P > 0.05) between the registrar and physician group responses for any study endpoint. Conclusion: Few ED doctors correctly instruct their patients in the VM technique recommended for management of SVT. Hence, maximal vagal tone and SVT conversion rates may not be achieved in many cases. The use of the recommended VM technique is encouraged.     

The effect of pain on changes in heart rate during the Valsalva manoeuvre

Abstract. The presence of pain may influence autonomic function in patients with painful neurological or cardiovascular disorders. The aim of the present study was to determine whether pain influences cardiac baroreflexes during the Valsalva manoeuvre. Eighteen healthy subjects immersed their hand twice at each temperature in 30 °C water and painfully hot (47 °C) and cold water (12 °C and 7 °C) for 2.5 minutes, followed by 5 minute rest periods. During 50% of the immersions, subjects performed the Valsalva manoeuvre (40 mmHg for 30 seconds) starting one minute after their hand entered the water. Pain ratings and heart rate were greater during the 7 °C and 47 °C immersions than during the 12 °C and 30 °C immersions. Pain-induced increases in heart rate did not influence peak tachycardia during phase II or III of the Valsalva manoeuvre or peak bradycardia during phase IV, but opposed bradycardia during the post-strain recovery period. Further studies are needed to establish whether pain influences indices of autonomic function during clinical assessment.     

Intraocular pressure responses to systemic autonomic stimulation in diabetes mellitus

Summary The acute changes in intraocular pressure during sustained handgrip contraction (2.5 minutes duration) and the Valsalva manoeuvre (15 seconds duration), both standard tests of autonomic nerve function were studied in 14 diabetic patients and 14 similar aged control subjects.During sustained handgrip contraction, diastolic blood pressure increased by 16.35 ± 1.87 mmHg in the diabetic patients and 21.36 ± 0.66 mmHg for the control group. Mean intraocular pressure decreased by 0.71 ± 0.43 mmHg in the diabetics, p < 0.05 and 0.64 ± 0.27 mmHg, p < 0.01) in the control group.There was no correlation between the blood pressure and the intraocular pressure responses in either group.On release of handgrip contraction, mean recovery intraocular pressure over 5 minutes was significantly lower than mean baseline values for the two groups; control: baseline 14.78 ± 0.49 to 14.14 ± 0.67, p < 0.001 and diabetic: 14.57 ± 0.65 to 13.86 ± 0.72, p < 0.001.During the Valsalva manoeuvre, there was a significant rise in intraocular pressure in the control (+7.85 ± 0.75mmHg, p < 0.001) and the diabetic group (+7.93 ± 1.18mmHg, p < 0.001). 5 minutes after release of intrathoracic pressure, mean recovery intraocular pressure remained significantly below baseline values for the two groups. The Valsalva ratios were in the normal range for the control group (1.21 to 2.2) while 2 diabetics had abnormal ratios.     

冠心病患者等长收缩运动时肺毛细血管嵌顿压升高的机理

用左右心导管观察10例典型劳力性心绞痛患者在极量等长收缩运动(IE)和IE加乏氏动作时的血液动力学反应及临床表现,并以冠状动脉气囊扩张成形术建立急、慢性冠状动脉供血不足以及正常冠状动脉的模型。结果表明进行极量前臂等长收缩运动和乏氏动作时肺毛细血管嵌顿压升高,其机理可能与胸腔内压的增高和主动脉压的增高有关而与心肌缺血无关。这解释了为何等长收缩运动试验的敏感性不高,也说明对心脏患者禁止IE和乏氏动作的概念应该加以修正。