THE PERIPHERAL BLOOD FLOW IN SURGICAL SHOCK: The Reduction in Circulation through the Hand Resulting from Pain, Fear, Cold, and Asphyxia, with Quantitative Measurements of the Volume Flow of Blood in Clinical Cases of Surgical Shock

Brachial artery reactivity and vascular reactive hyperemia for preoperative anaesthesia risk assessment - an observational study

Background

Non-invasive measures of vascular reactivity have emerged to refine cardiovascular risk. However, limited data exists investigating vascular reactivity as a preoperative diagnostic tool for anesthesiologists. In this study, we compare the utility of two non-invasive techniques, Brachial Artery Reactivity Testing (BART) and Digital Thermal Monitoring (DTM), as surrogates for measuring vascular reactivity.

Methods

Following IRB approval, 26 patients scheduled for major thoracic surgery (e.g. esophagectomy and pneumonectomy) were studied prospectively. BART [Flow mediated dilation (FMD) and Peak flow velocity (PFV)] and DTM [Temperature rebound (TR%)] were performed preoperatively at baseline using 5 minute blood pressure cuff occlusion of the upper arm. Statistical summaries were provided for the comparison of BART and DTM with select patient characteristics, and correlations were used to investigate the strength of the relationship between BART and DTM measurements.

Results

Patients preoperatively diagnosed with hyperlipidemia were associated with lower FMD% values {Median (Range): 14.8 (2.3, 38.1) vs. 6.2 (0.0, 14.3); p = 0.006}. There were no significant associations between BART and DTM techniques in relation to cardiovascular risk factors or postoperative complications.

Conclusion

Our study suggests that impaired vascular reactivity as measured by BART is associated with the incidence of hyperlipidemia. Also, using a novel technique such as DTM may provide a simpler and more accessible point of care testing for vascular reactivity in a perioperative setting. Both non-invasive techniques assessing vascular function warrant further refinement to better assist preoperative optimization strategies aimed at improving perioperative vascular function.

Responses of peripheral blood flow to acute hypoxia and hyperoxia as measured by optical microangiography

Oxygen availability is regarded as a critical factor to metabolically regulate systemic blood flow. There is a debate as to how peripheral blood flow (PBF) is affected and modulated during hypoxia and hyperoxia; however in vivo evaluating of functional PBF under oxygen-related physiological perturbation remains challenging. Microscopic observation, the current frequently used imaging modality for PBF characterization often involves the use of exogenous contrast agents, which would inevitably perturb the intrinsic physiologic responses of microcirculation being investigated. In this paper, optical micro-angiography (OMAG) was employed that uses intrinsic optical scattering signals backscattered from blood flows for imaging PBF in skeletal muscle challenged by the alteration of oxygen concentration. By utilizing optical reflectance signals, we demonstrated that OMAG is able to show the response of hemodynamic activities upon acute hypoxia and hyperoxia, including the modulation of macrovascular caliber, microvascular density, and flux regulation within different sized vessels within skeletal muscle in mice in vivo. Our results suggest that OMAG is a promising tool for in vivo monitoring of functional macro- or micro-vascular responses within peripheral vascular beds.

THE STATE OF THE VESSELS OF THE MESENTERY IN SHOCK PRODUCED BY CONSTRICTING THE LIMBS AND THE BEHAVIOR OF THE VESSELS FOLLOWING HEMORRHAGE

1. Direct observations of the arteries, arterioles, capillaries, veins, and lymphatics in the mesentery of anesthetized cats put into shock by incomplete occlusion of the circulation of the limbs showed that: (a) Marked constriction of the arteries and arterioles, produced by muscular contraction, occurred usually within an hour after incomplete occlusion of the limbs, lasted several hours, and finally gave way in most instances to relaxation an hour or more before death. The constriction reduced the blood supply to the mesentery and intestine and the venous return from them. It did not, however, interrupt the blood flow. No pooling or stagnation of blood was seen even as a terminal phenomenon. (b) The veins of the mesentery also became constricted but showed less tendency to dilate as death approached. The lymphatics likewise became somewhat narrowed. Even during the terminal stage the leukocytes moved along without change in shape or sticking to the walls of the capillaries or venules. (c) Hematocrit determinations showed progressive hemoconcentration of moderate degree. (d) Autopsy usually showed the presence of small hemorrhages in many parts of the body, especially the heart, liver, spleen, and lungs. (e) Bilateral nephrectomy, suprarenalectomy, and pancreatectomy did not significantly alter the morphological picture elicited by shock induced by restriction of the circulation to the limbs. 2. Removal of large amounts of blood was always followed within a short time by constriction of arteries, arterioles, veins, and lymphatics of the mesentery. 3. Fall in arterial pressure produced by pithing was not accompanied by change in diameter of the arteries, arterioles, veins, or lymphatics, or by blanching of the mesentery or gut.

Effects of arterial hypoxia on the cutaneous circulation of the rabbit

1. Changes in blood flow of the skin of the rabbit's ear and hind limb have been studied during arterial hypoxia by a calibrated heat conductivity method, together with changes in arterial pressure and aortic blood temperature.2. There is little change in the blood flow of the hind-limb skin during the early phase of arterial hypoxia, reflecting a balance between the local dilator effects of hypoxia and the increased constrictor activity mediated through the sympathetic nerves as a result of arterial chemoreceptor excitation. During more prolonged arterial hypoxia there is a small gradual dilatation of the vessels of the hind-limb skin as a result of some diminution in the initial intensity of vasoconstrictor activity.3. There is much more extensive vasodilatation in the ear than in the hind-limb skin during arterial hypoxia. Vasoconstrictor activity is slight in this region. Comparison of the ear responses to arterial and to primary tissue hypoxia suggests that in the former type of hypoxia stimulation of the arterial chemoreceptors inhibits thermoregulatory vasoconstriction to the ear, whilst in the latter type of hypoxia baroreceptor reflexes maintain or intensify it.

Effect of Hemorrhage on the Cardiac Output and Distribution in the Rat

The effects of moderate and severe hemorrhage on the cardiac output and its distribution have been studied in the rat. In moderate hemorrhage, cerebral and adrenal blood flow are well maintained through localized vasodilatation while most other organs show increased vascular resistance and diminished blood flow. After severe hemorrhage, despite further changes in territorial resistances, the blood flow is not maintained in any area of the body.

The Distribution of Body Fluids In Congestive Heart Failure

The pathogenesis of congestive heart failure is discussed. Experimental evidence is cited to support the thesis that abnormalities in the distribution of body fluids may affect circulatory and renal function, and hence may be a cause as well as an effect in the complex sequence of events leading to the congestive state. Emphasis is placed upon alterations in cellular metabolism which may lead to such disturbances in body fluids and so through various mechanisms, cellular, humoral, and circulatory, may modify the volume regulation of the body.

Impending Hemorrhagic Shock and the Course of Events following Administration of Dibenamine

By blocking sympathogenic vasoconstrictor mechanisms with dibenamine, a dog's tolerance to severe hemorrhagic hypotension states is definitely improved. New evidence is presented that partial release from vasoconstriction achieved by, giving small doses of dibenamine during the impending shock state seems to provide animals with even greater tolerance to this standardized form of stress. Although the use of dibenamine clinically for this purpose seems contraindicated, the dangers of at administering vasoconstrictor drugs to patients in impending shock are emphasized.