Treatment of shock with vasodilators measuring skin temperature on the big toe. Ten years' experience in 150 cases

Seasonal variation of temperature regulation: do thermoregulatory responses "spring" forward and "fall" back?

Seasonal variations in day length and light intensity can affect the circadian rhythm as well as some characteristics of temperature regulation. We investigated characteristics of autonomic (ATR), behavioural (BTR) and nocturnal (NTR) temperature regulation during spring and autumn. Eleven participants underwent experiments in both seasons. To assess ATR, participants performed a 30-min bout of submaximal upright exercise on a cycle ergometer, followed by 100 min of water immersion (28 °C). Thresholds for the onset of shivering and sweating and vasomotor response were measured. BTR was assessed using a water-perfused suit, with participants regulating the water-perfused suit temperature (Twps) within a range, considered as thermally comfortable. The Twps changed in a saw-tooth manner from 10 to 50 °C; by depressing a switch, the direction of the Twps changed, and this limit defined the thermal comfort zone (TCZ) for each participant. A 24-h proximal (calf)-distal (toe) skin temperature gradient (∆Tc-t) was measured to assess NTR. Initiation of vasomotor tone, shivering and sweating was similar between trials. Width of the TCZ was 8.1 °C in spring and 8.6 °C in autumn (p = 0.1), with similar upper and lower regulated temperatures. ∆Tc-t exhibited a typical circadian rhythm with no difference between seasons. Minor changes in skin temperature and oxygen consumption (p ˂ 0.05) between the seasons may indicate a degree of seasonal adaptation over the course of winter and summer, which persisted in spring and autumn. Other factors, such as country, race, sex and age could however modify the outcome of the study.

A gellan-based fluid gel carrier to enhance topical spray delivery

Autologous cell transplantation was introduced to clinical practice nearly four decades ago to enhance burn wound re-epithelialisation. Autologous cultured or uncultured cells are often delivered to the surface in saline-like suspensions. This delivery method is limited because droplets of the sprayed suspension form upon deposition and run across the wound bed, leading to uneven coverage and cell loss. One way to circumvent this problem would be to use a gel-based material to enhance surface retention. Fibrin systems have been explored as co-delivery system with keratinocytes or as adjunct to 'seal' the cells following spray delivery, but the high costs and need for autologous blood has impeded its widespread use. Aside from fibrin gel, which can exhibit variable properties, it has not been possible to develop a gel-based carrier that solidifies on the skin surface. This is because it is challenging to develop a material that is sprayable but gels on contact with the skin surface. The manuscript reports the use of an engineered carrier device to deliver cells via spraying, to enhance retention upon a wound. The device involves shear-structuring of a gelling biopolymer, gellan, during the gelation process; forming a yield-stress fluid with shear-sensitive behaviours, known as a fluid gel. In this study, a formulation of gellan gum fluid gels are reported, formed with from 0.75 or 0.9% (w/v) polymer and varying the salt concentrations. The rheological properties and the propensity of the material to wet a surface were determined for polymer modified and non-polymer modified cell suspensions. The gellan fluid gels had a significantly higher viscosity and contact angle when compared to the non-polymer carrier. Viability of cells was not impeded by encapsulation in the gellan fluid gel or spraying. The shear thinning property of the material enabled it to be applied using an airbrush and spray angle, distance and air pressure were optimised for coverage and viability. STATEMENT OF SIGNIFICANCE: Spray delivery of skin cells has successfully translated to clinical practice. However, it has not yet been widely accepted due to limited retention and disputable cell viability in the wound. Here, we report a method for delivering cells onto wound surfaces using a gellan-based shear-thinning gel system. The viscoelastic properties allow the material to liquefy upon spraying and restructure rapidly on the surface. Our results demonstrate reduced run-off from the surface compared to currently used low-viscosity cell carriers. Moreover, encapsulated cells remain viable throughout the process. Although this paper studies the encapsulation of one cell type, a similar approach could potentially be adopted for other cell types. Our data supports further studies to confirm these results in in vivo models.

Assessment of Regional Perfusion and Organ Function: Less and Non-invasive Techniques

Sufficient organ perfusion essentially depends on preserved macro- and micro-circulation. The last two decades brought substantial progress in the development of less and non-invasive monitoring of macro-hemodynamics. However, several recent studies suggest a frequent incoherence of macro- and micro-circulation. Therefore, this review reports on interactions of macro- and micro-circulation as well as on specific regional and micro-circulation. Regarding global micro-circulation the last two decades brought advances in a more systematic approach of clinical examination including capillary refill time, a graded assessment of mottling of the skin and accurate measurement of body surface temperatures. As a kind of link between macro- and microcirculation, a number of biochemical markers can easily be obtained. Among those are central-venous oxygen saturation (S_cvO₂), plasma lactate and the difference between central-venous and arterial CO₂ (cv-a-pCO₂-gap). These inexpensive markers have become part of clinical routine and guideline recommendations. While their potential to replace parameters of macro-circulation such as cardiac output (CO) is limited, they facilitate the interpretation of the adequacy of CO and other macro-circulatory markers. Furthermore, they give additional hints on micro-circulatory impairment. In addition, a number of more sophisticated technical approaches to quantify and visualize micro-circulation including video-microscopy, laser flowmetry, near-infrared spectroscopy (NIRS), and partial oxygen pressure measurement have been introduced within the last 20 years. These technologies have been extensively used for scientific purposes. Moreover, they have been successfully used for educational purposes and to visualize micro-circulatory disturbances during sepsis and other causes of shock. Despite several studies demonstrating the association of these techniques and parameters with outcome, their practical application still is limited. However, future improvements in automated and “online” diagnosis will help to make these technologies more applicable in clinical routine. This approach is promising with regard to several studies which demonstrated the potential to guide therapy in different types of shock. Finally several organs have specific patterns of circulation related to their special anatomy (liver) or their auto-regulatory capacities (brain, kidney). Therefore, this review also discusses specific issues of monitoring liver, brain, and kidney circulation and function.

Narrative review: clinical assessment of peripheral tissue perfusion in septic shock

Sepsis is one of the main reasons for intensive care unit admission and is responsible for high morbidity and mortality. The usual hemodynamic targets for resuscitation of patients with septic shock use macro-hemodynamic parameters (hearth rate, mean arterial pressure, central venous pressure). However, persistent alterations of microcirculatory blood flow despite restoration of macro-hemodynamic parameters can lead to organ failure. This dissociation between macro- and microcirculatory compartments brings a need to assess end organs tissue perfusion in patients with septic shock. Traditional markers of tissue perfusion may not be readily available (lactate) or may take time to assess (urine output). The skin, an easily accessible organ, allows clinicians to quickly evaluate the peripheral tissue perfusion with noninvasive bedside parameters such as the skin temperatures gradient, the capillary refill time, the extent of mottling and the peripheral perfusion index.

Exploration de la perfusion tissulaire microcirculatoire au cours du choc septique

Au cours des infections graves, les travaux chez l’animal et chez l’homme ont mis en évidence une altération de la perfusion microcirculatoire à l’origine des défaillances viscérales et potentiellement du décès. La sévérité des anomalies microcirculatoires ainsi que leur persistance sont des facteurs prédictifs de mortalité indépendamment du débit cardiaque ou de la pression artérielle. Il est donc indispensable de développer des outils permettant d’évaluer la perfusion microcirculatoire au lit du malade. De nombreux travaux au cours du sepsis suggèrent que l’analyse de la perfusion cutanée au travers de sa température (et/ou du gradient), du temps de recoloration cutané, de l’étendue des marbrures et de l’indice de perfusion périphérique constitue un outil simple qui permet au réanimateur une évaluation rapide des anomalies microcirculatoires.

Using skin for drug delivery and diagnosis in the critically ill

Skin offers easy access, convenience and non-invasiveness for drug delivery and diagnosis. In principle, these advantages of skin appear to be attractive for critically ill patients given potential difficulties that may be associated with oral and parenteral access in these patients. However, the profound changes in skin physiology that can be seen in these patients provide a challenge to reliably deliver drugs or provide diagnostic information. Drug delivery through skin may be used to manage burn injury, wounds, infection, trauma and the multisystem complications that rise from these conditions. Local anaesthetics and analgesics can be delivered through skin and may have wide application in critically ill patients. To ensure accurate information, diagnostic tools require validation in the critically ill patient population as information from other patient populations may not be applicable.

Noninvasive monitoring of peripheral perfusion

BACKGROUND

Early hemodynamic assessment of global parameters in critically ill patients fails to provide adequate information on tissue perfusion. It requires invasive monitoring and may represent a late intervention initiated mainly in the intensive care unit. Noninvasive monitoring of peripheral perfusion can be a complementary approach that allows very early application throughout the hospital. In addition, as peripheral tissues are sensitive to alterations in perfusion, monitoring of the periphery could be an early marker of tissue hypoperfusion. This review discusses noninvasive methods for monitoring perfusion in peripheral tissues based on clinical signs, body temperature gradient, optical monitoring, transcutaneous oximetry, and sublingual capnometry.

DISCUSSION

Clinical signs of poor peripheral perfusion consist of a cold, pale, clammy, and mottled skin, associated with an increase in capillary refill time. The temperature gradients peripheral-to-ambient, central-to-peripheral and forearm-to-fingertip skin are validated methods to estimate dynamic variations in skin blood flow. Commonly used optical methods for peripheral monitoring are perfusion index, near-infrared spectroscopy, laser Doppler flowmetry and orthogonal polarization spectroscopy. Continuous noninvasive transcutaneous measurement of oxygen and carbon dioxide tensions can be used to estimate cutaneous blood flow. Sublingual capnometry is a noninvasive alternative for gastric tonometry.

Core-peripheral temperature gradient as a diagnostic test in dyspnoea

OBJECTIVES

To evaluate whether the core-peripheral temperature gradient could be used to distinguish between cardiac and respiratory causes of dyspnoea.

METHODS

In total, 50 patients were enrolled in the study, based on the following inclusion criteria: (a) a primary presenting complaint of dyspnoea; (b) age > 40 years; (c) respiratory rate > 20 breaths/min; (d) hypoxia. The tympanic temperature and the temperature of the nasal tip were recorded, and the patient's discharge data and chest x ray results checked. Where there was discordance, arbitration was carried out by another researcher.

RESULTS

Four patients were excluded, hence the final study sample was 46 patients. There was a statistically significant difference between the mean temperature gradients of the two study populations (p < 0.001). A gradient of > 8 degrees C was able to rule in a cardiovascular cause (92% specificity) whereas one of < 5 degrees C could rule it out (100% sensitivity).

CONCLUSION

The test is safe, non-invasive and inexpensive. Although there were some limitations to the study, the test can still be commended as a useful adjunct to the emergency assessment of the acutely breathless patient.

Core-peripheral temperature gradient in children: does it reflect clinically important changes in circulatory haemodynamics?

Following open heart surgery, changes in core and peripheral skin temperature and changes in the core-peripheral temperature gradient were measured in 10 children. These were correlated with changes in cardiac index, systemic vascular resistance index, mean arterial pressure and urinary output. During the study intervals, which lasted 1 h each, no changes in medical management were made. Using Spearman's rank correlation, only a change in central venous pressure was found to correlate with a change in the core-peripheral temperature gradient. We conclude that a change in the core-peripheral temperature will give valuable information about the patient's intravascular volume.

Core-peripheral temperature gradient does not predict cardiac output or systemic vascular resistance in children

We prospectively measured toe temperature, rectal temperature, systemic arterial pressure and cardiac output on two occasions one hour apart in 136 children who had had phenoxybenzamine after cardiac surgery while on cardiopulmonary bypass. Repeated measures analysis showed that there was no significant correlation between the change in temperature gradient over one hour in each patient and the change in cardiac index (r = 0.03, P greater than 0.1) or systemic vascular resistance (r = 0.007, P greater than 0.1). Although the peripheral temperature (toe temperature), and the core-peripheral temperature difference are simple, safe and inexpensive to measure in the population studied, they did not provide any guide to either cardiac output or systemic vascular resistance.

Toe temperature versus transcutaneous oxygen tension monitoring during acute circulatory failure

Measurements of toe temperature and transcutaneous PO2 (PtcO2) have been both suggested for non-invasive assessment of peripheral blood flow in acute circulatory failure. The underlying principle of the two methods is that cutaneous vasoconstriction occurs early when tissue perfusion is altered. In 15 patients, we compared the two measurements during cardiogenic shock (27 measurements) or septic shock (29 measurements). Toe-ambiant temperature gradient and PtcO2 correlated well together (r = 0.66, p less than 0.001) especially in hyperkinetic septic shock (r = 0.79, p less than 0.001). In cardiogenic shock, toe-ambiant temperature correlated well with cardiac index (r = 0.63), stroke index (r = 0.64) and oxygen transport (r = 0.65), and these correlations were stronger than for PtcO2. In septic shock, both techniques were poor indicators of blood flow indexes but PtcO2 rather correlated with arterial pressure (r = 0.66) and left ventricular work (r = 0.66). Trend evaluation of data revealed in cardiogenic shock that the increase in toe temperature usually preceded the increase in PtcO2. Since measurement of PtcO2 is technically more complicated, correlates less well with standard hemodynamic parameters and later reflects cardiovascular improvement, it has no advantage over measurement of toe temperature in circulatory shock. In cardiogenic shock, measurements of toe temperature can reliably track cardiac output changes. In septic states, however, non-invasive assessment of skin perfusion is of limited interest.

Patient monitoring during and after open heart surgery by an improved deep body thermometer

The deep body thermometer developed by Fox was improved by Togawa by thermal insulation of the probe. The present status of medical progress in clinical thermometry through the improved deep body thermometer was reviewed from the view point of cardiac surgery. The forehead and sole temperatures obtained by this improved thermometer were monitored and recorded by a multipotentiometric recorder continuously up to 12 days in the patients admitted to the ICU who underwent open heart surgery. The forehead tissue temperature measured by this thermometer is slightly lower than and parallel to the rectal temperature, being close to the pulmonary arterial blood temperature. On the other hand, the sole tissue temperature fluctuates from room temperature to the forehead tissue temperature, sometimes showing rhythmic changes. The former seems to be the core temperature and the latter, the shell temperature. The dissociation when the two temperatures are more than 7 degrees C apart from each other suggests that the hemodynamical condition is worse than in the convergence when they remain within 2 degrees C. A state of shock can be diagnosed when the arterial systolic pressure is less than 90 mmHg and the urine output less than 1 ml/min/mg in addition to the dissociation. The effect of treatment and the prognosis for the patient are predictable according to the trends of the two temperatures as divergent or convergent. The dynamic thermometry by this thermometer is very informative and the procedure is noninvasive without discomfort to the patient.

Continuous tissue pH and transcutaneous PO2 measurement as an index of tissue perfusion in critically ill patients

Measurements of transcutaneous PO2 (tcPO2) and tissue pH (pHt) were compared with arterial values in 28 critically ill patients. Eleven of the patients were undergoing continuous flow cardiopulmonary bypass and the other 17 were admitted to the Intensive Therapy Unit (ITU) suffering from a variety of medical and surgical disorders. A total of 135 observations were made on the 28 patients. The overall correlation between the two sets of measurements was poor. The correlation coefficient (r) between arterial PO2 (Pa,O2) and tcPO2 was 0.41 (P less than 0.01) and between arterial pH (pHa) and pHt 0.67 (P less than 0.01). However, the value varied greatly in different groups of patients. In those patients with cardiopulmonary failure, the tcPO2 and pHt measurements rapidly and accurately reflected changes in peripheral tissue perfusion, by contrast the core-peripheral temperature deficit did not change significantly. It is concluded that the technique can be used as a sensitive index of peripheral blood flow and may have prognostic significance

Central peripheral temperature gradient. Its value and limitations in the management of critically iii surgical patients

Monitoring the central peripheral temperature gradient in critically ill surgical patients is a simple, sensitive, noninvasive and inexpensive method that can accurately reflect the state of peripheral circulation. It serves as an early warning sign, and its return to normal is a good measure of the efficacy o f therapy. Recognition of the cause of an abnormal gradient is essential to successful management since it can result from pain as well as hypovolemia. Warm-up patterns vary, and every patient should be treated individually. Forcing vasodilatation is usually unnecessary and amy be dangerous in hypothermic patients and in patients with hypovolemia if blood volume is not corrected simultaneously. Peripheral vascular disease, central hypothermia and the use of vasoactive drugs limit the usefulness of this method.

Myocardial performance early after aorto-coronary bypass surgery and the influence of nitroprusside infusion

The central and peripheral circulation were studied in 12 patients after aortocoronary bypass surgery. During the initial 5 h after termination of cardiopulmonary bypass, the oesophageal temperature rose from 36.5 degrees C to 39.4 degrees C, concomitant with cutaneous vasoconstriction and an increase in systemic vascular resistance (SVR) and mean arterial blood pressure (MABP). The oxygen uptake index (Vo2I) increased by 57% during the rewarming period. The cardiac index (CI), which was constant at 2.8 l.min-1.m-2, was too low to satisfy this oxygen demand and the arterio-venous oxygen content difference (AVDo2) increased to 3.0 mmol . l-1 by the 3rd hour. After 5 h, SVR had decreased and cutaneous vasodilation began. Vo2I and AVDo2 decreased. The postoperative myocardial function was moderately impaired and deteriorated after the cutaneous vasodilation. Twelve patients were given an infusion of sodium nitroprusside during the postoperative period (0.25--2.5 micrograms . kg-1 . min-1). The rewarming pattern was not influenced by this infusion, but the initial increases in MABP and SVR were eliminated. The myocardial performance was better in the nitroprusside group. CI was significantly higher than in the control group (3.5 l.min-1.m-2) and AVDo2 remained normal.

The importance of environmental conditions, especially temperature, in the operating room and intensive care ward

Although most patients are essentially well enough to be able to resist or to adapt to unfavourable ambient conditions, this may not be so with an ill patient or one who is having or has had a serious operation. The climatic conditions necessary in the operating room to give an optimal environment are discussed. These are second in importance only to control of infectivity. Air-conditioning in operating suites should be obligatory; there is even official acceptance of this. Earlier recommendations that the operating room should be heated to up to 80 degree F (27-9 degree C) are obsolete. The temperature most favoured by surgeons is 18-5-21 degree C; some prefer a range of 21-22 degre C. The critical ambient temperature desirable is 21 degree C. For infants and children this may be increased up to 24 degree C. It is difficult or impossible to achieve climatic conditions in the operating room that are acceptable to all. The needs of the patient are of special importance and are largely neglected; he alone is unable to speak for himself. The disposition of air inlets in the operating room is fully discussed. Climatic conditions in the intensive care unit are of great importance and are discussed. The need for full air-conditioning is absolute although this is often ignored. The delivery of conditioned air within the intensive care unit is also fully presented, especially the need to avoid direct chilling of the patient. The advantages of horizontal laminar air flow are presented.

Use of central and peripheral temperature measurements in care of the critically ill child

In the presence of constant ambient conditions, a fall in effective circulating blood volume causes peripheral vasoconstriction which is reflected in a fall in peripheral (great toe) temperature and thus in an increase in the central (rectal)/peripheral temperature gradient. We report 5 illustrative clinical situations showing the value of this technique in the medical care of critically ill children. We suggest that such measurements are useful, first in the recognition of dehydration and in assessing the response to treatment, secondly in managing shock, and finally, in differentiating dehydration fever from other causes of fever.

Peripheral vasoconstriction after open-heart surgery

Matthews, H. R., Meade, J. B. and Evans, C. C. (1974).Thorax, 29, 338-342. Peripheral vasoconstriction after open-heart surgery. Great toe temperatures have been recorded serially after open-heart surgery on 148 patients in order to study the change from a peripherally vasoconstricted to a peripherally vasodilated state. The results in 81 `normals' show a remarkably consistent warm-up pattern which is independent of the duration or nature of operation and of many other potential variables. The reproducibility of this event has enabled us to construct a nomogram which predicts the limits of time within which a patient should warm up if he is recovering normally from operation. In our unit patients should reach a toe temperature of 34°C within 6·5 hours of return to the intensive care unit if they are breathing spontaneously and within 8 hours if they are on intermittent positive-pressure ventilation, time limits at lower temperatures also being defined by the nomogram. It is anticipated that the recognition of the normal postoperative warm-up pattern will facilitate the early detection and effective treatment of circulatory insufficiency after open-heart surgery.

Temperature of the great toe as an indication of the severity of shock

To establish whether changes in skin temperature would provide objective indication of the presence and severity of shock, hemodynamic and temperature measurements were obtained with the aid of a digital computer. Values obtained 3 hours after admission and 3 hours prior to discharge or death in 100 patients who presented with clinical signs of circulatory shock were analyzed. Temperature was measured with standard thermistor probes at five sites: the digital pad of the third finger, the large toe, the deltoid region of the arm, the lateral portion of the thigh, and the rectum.

A significant correlation was demonstrated between the cardiac output and temperature of the toe (r = 0.71). Correlations were increased to 0.73 when corrections were made for changes in ambient temperature. A stepwise regression analysis provided no significant improvement in the predictability of cardiac index when the values for temperatures of other skin sites were included. Discriminant function analysis showed that an early measurement of toe temperature correctly predicts patient outcome 67% of the time.