Impaired compensatory response to hypovolaemic circulatory stress in type 1 diabetes mellitus

Risk factors and a predictive nomogram for hemodynamic instability during adrenalectomy for large pheochromocytomas and paragangliomas: A retrospective cohort study

OBJECTIVE

This study aimed to investigate risk factors for intraoperative hemodynamic instability (HDI) and construct a clinical model for predicting intraoperative HDI for large pheochromocytomas and paragangliomas (PPGLs) patients.

METHODS

A single-center retrospective study of the clinicopathological data of patients undergoing surgery for PPGLs larger than 5 cm in diameter was conducted. A total of 215 eligible patients were enrolled in the study. Three advanced statistical methods were used to select independent risk factors in the training cohort for constructing a nomogram for predicting intraoperative HDI. The predictive performance of the model was assessed by area under the curve (AUC), positive predictive value (PPV), negative predictive value (NPV), and calibration. Decision curve analysis (DCA) and clinical impact curves (CIC) were used to assess predictive accuracy and clinical utility. The performance of the nomogram of was further internally validated.

RESULTS

Comorbid diabetes mellitus, anemia, hypoproteinemia, 24-h urine vanillylmandelic acid and intraoperative blood transfusion (P < 0.05) were identified as independent risk factors for constructing the nomogram. In the training cohort, the AUC, PPV and NPV of the nomogram were 0.846, 91.6% and 69.2%. In the validation cohort, the AUC, PPV and NPV were 0.842, 91.8% and 63.3%. These showed good predictive power of the model. The calibration curves demonstrated an optimal consistency between the nomogram-predicted and the actual observed survival probability. DCA and CIC examination showed superior clinical relevance.

CONCLUSIONS

The nomogram can objectively and accurately predict intraoperative HDI in patients with large PPGLs, which can help in individualized pre-treatment decision-making.

The role of blood volume in cardiac dysfunction and reduced exercise tolerance in patients with diabetes

Blood volume is an integral component of the cardiovascular system, and fundamental to discerning the pathophysiology of multiple cardiovascular conditions leading to exercise intolerance. Based on a systematic search of controlled studies assessing blood volume, in this Personal View we describe how hypovolaemia is a prevalent characteristic of patients with diabetes, irrespective of sex, age, and physical activity levels. Multiple endocrine and haematological mechanisms contribute to hypovolaemia in diabetes. The regulation of intravascular volumes is altered by sustained hyperglycaemia and hypertension. Chronic activation of endocrine systems controlling fluid homeostasis, such as the renin-angiotensin-aldosterone system and vasopressin axis, has a role in progressive kidney desensitisation and diabetic nephropathy. Furthermore, albumin loss from the intravascular compartment reduces the osmotic potential of plasma to retain water. Hypovolaemia also affects the loading conditions and filling of the heart in diabetes. The elucidation of modifiable volumetric traits will plausibly have major health benefits in the diabetes population.

Preoperative risk factors for haemodynamic instability during pheochromocytoma surgery in Chinese patients

OBJECTIVE

Pheochromocytoma surgery carries a high risk of haemodynamic instability (HI). However, there are few studies investigating the risk factors for HI for pheochromocytoma surgery in a Chinese population. Therefore, our objective was to identify preoperative risk factors for HI during surgery in a Chinese population with pheochromocytoma.

PATIENTS AND METHODS

In this retrospective study, 134 patients undergoing surgery for pheochromocytoma at a single university-affiliated hospital between November 2002 and July 2017 were enrolled. Demographics, comorbidities, preoperative medical preparation, operation details and perioperative haemodynamics of these patients were retrospectively collected and analysed. Multivariable logistic regression analysis was performed to identify the preoperative risk factors for intraoperative HI.

RESULTS

32.8% (44/134) patients suffered from intraoperative HI. According to the result of multivariate analysis, tumour diameter >50 mm (odds ratio [OR] 2.526; 95% confidence interval [CI] 1.163-5.485; P = .019), diabetes/prediabetes (OR 2.251; 95% CI 1.039-4.876; P = .040) and preoperative systolic blood pressure fluctuation >50 mm Hg (OR 3.163; 95% CI 1.051-9.522, P = .041) were independent predictors for intraoperative HI. The observed incidence of HI was 8.9%, 42.6%, 47.8% and 60% when zero, one, two or three risk factors were present, respectively.

CONCLUSIONS

HI is common among Chinese patients undergoing surgery for pheochromocytoma. Our study identified three predictive factors for intraoperative HI: a large tumour diameter, diabetes/prediabetes and a great preoperative systolic blood pressure fluctuation. Furthermore, patients are more likely to suffer from HI when they have more predictive risk factors. Identification of these risk factors can help to improve perioperative management.

Body temperature regulation in diabetes

The effects of type 1 and type 2 diabetes on the body's physiological response to thermal stress is a relatively new topic in research. Diabetes tends to place individuals at greater risk for heat-related illness during heat waves and physical activity due to an impaired capacity to dissipate heat. Specifically, individuals with diabetes have been reported to have lower skin blood flow and sweating responses during heat exposure and this can have important consequences on cardiovascular regulation and glycemic control. Those who are particularly vulnerable include individuals with poor glycemic control and who are affected by diabetes-related complications. On the other hand, good glycemic control and maintenance of aerobic fitness can often delay the diabetes-related complications and possibly the impairments in heat loss. Despite this, it is alarming to note the lack of information regarding diabetes and heat stress given the vulnerability of this population. In contrast, few studies have examined the effects of cold exposure on individuals with diabetes with the exception of its therapeutic potential, particularly for type 2 diabetes. This review summarizes the current state of knowledge regarding the impact of diabetes on heat and cold exposure with respect to the core temperature regulation, cardiovascular adjustments and glycemic control while also considering the beneficial effects of maintaining aerobic fitness.

Reduced Venous Compliance in Young Women with Type 1 Diabetes - Further Aggravated by Prolonged Elevated Levels of HbA1c

BACKGROUND

Young patients with diabetes present with reduced compensatory responses to hypovolemic stress. Less compliant veins could be a contributing factor, since roughly two-thirds of the blood volume resides in the venous system as a blood reservoir, adjusting proper venous inflow to the heart. The aim of this study was to measure venous compliance and lower limb blood pooling during hypovolemic stress, and to correlate them to indices of diabetes severity and glucose control.

METHODS

Fifteen young women with type 1 diabetes (DW) and 18 healthy age-matched women (C) were subjected to lower body negative pressure (LBNP) (11-44 mmHg), creating hypovolemic stress. Lower limb blood pooling was measured with strain gage technique and venous compliance calculated as the relationship between ∆V/∆P.

RESULTS

DW presented with reduced blood pooling (e.g., blood pooling during LBNP of 44 mmHg, DW, 1.69 ± 0.10; C, 2.10 ± 0.08 (ml/100 ml), and P = 0.003). Calculated venous compliance was also reduced in DW (e.g., compliance at 20 mmHg, DW, 0.046 ± 0.003; C, 0.059 ± 0.002 (ml/100 ml/mmHg), and P = 0.002). A progressive reduction in both venous compliance (P < 0.007) and blood pooling (P < 0.005) was seen with increasing level of HbA_1c, and furthermore, less strongly associated with presence of microvascular disease (signs of retinopathy).

CONCLUSION

Women with type 1 diabetes present with both reduced venous compliance and blood pooling. The reductions were particularly present in patients with long-standing poor glycemic control.

Reduced venous compliance: an important determinant for orthostatic intolerance in women with vasovagal syncope

The influence of lower limb venous compliance on orthostatic vasovagal syncope (VVS) is uncertain. The most widespread technique to calculate venous compliance uses a nonphysiological quadratic regression equation. Our aim was therefore to construct a physiologically derived venous wall model (VWM) for calculation of calf venous compliance and to determine the effect of venous compliance on tolerance to maximal lower body negative pressure (LBNP). Venous occlusion plethysmography was used to study calf volume changes in 15 women with VVS (25.5 ± 1.3 yr of age) and 15 controls (22.8 ± 0.8 yr of age). The fit of the VWM and the regression equation to the experimentally induced pressure-volume curve was examined. Venous compliance was calculated as the derivative of the modeled pressure-volume relationship. Graded LBNP to presyncope was used to determine the LBNP tolerance index (LTI). The VWM displayed a better fit to the experimentally induced pressure-volume curve (P < 0.0001). Calf blood pooling was similar in the groups and was not correlated to the LTI (r = 0.204, P = 0.30). Venous compliance was significantly reduced at low venous pressures in women with VVS (P = 0.042) and correlated to the LTI (r = 0.459, P = 0.014) in the low pressure range. No correlation was found between venous compliance at high venous pressures and the LTI. In conclusion, the new VWM accurately adopted the curvilinear pressure-volume curve, providing a valid characterization of venous compliance. Reduced venous compliance at low venous pressures may adversely affect mobilization of peripheral venous blood to the central circulation during hypovolemic circulatory stress in women with VVS.

Calf venous compliance measured by venous occlusion plethysmography: methodological aspects

PURPOSE

Calf venous compliance (C calf) is commonly evaluated with venous occlusion plethysmography (VOP) during a standard cuff deflation protocol. However, the technique relies on two not previously validated assumptions concerning thigh cuff pressure (P cuff) transmission and the impact of net fluid filtration (F filt) on C calf. The aim was to validate VOP in the lower limb and to develop a model to correct for F filt during VOP.

METHODS

Strain-gauge technique was used to study calf volume changes in 15 women and 10 age-matched men. A thigh cuff was inflated to 60 mmHg for 4 and 8 min with a subsequent decrease of 1 mmHg s(-1). Intravenous pressure (P iv) was measured simultaneously. C calf was determined with the commonly used equation [Compliance = β 1 + 2β 2 × P cuff] describing the pressure-compliance relationship. A model was developed to identify and correct for F filt.

RESULTS

Transmission of P cuff to P iv was 100 %. The decrease in P cuff correlated well with P iv reduction (r = 0.99, P < 0.001). Overall, our model showed that C calf was underestimated when F filt was not accounted for (all P < 0.01). F filt was higher in women (P < 0.01) and showed a more pronounced effect on C calf compared to men (P < 0.05). The impact of F filt was similar during 4- and 8-min VOP.

CONCLUSIONS

P cuff is an adequate substitute for P iv in the lower limb. F filt is associated with an underestimation of C calf and differences in the effect of F filt during VOP can be accounted for with the correction model. Thus, our model seems to be a valuable tool in future studies of venous wall function.

Decreased circulatory response to hypovolemic stress in young women with type 1 diabetes

OBJECTIVE

Diabetes is associated with hemodynamic instability during different situations involving acute circulatory stress in daily life. Young men with type 1 diabetes have been shown to have impaired circulatory response to hypovolemic stress. The effect of type 1 diabetes on cardiovascular response to hypovolemia in young women is unknown, however.

RESEARCH DESIGN AND METHODS

Lower body negative pressure of 30 cm H2O was used to create rapid hypovolemic stress in 15 young women with type 1 diabetes (DW) and 16 healthy women (control subjects [C]). Compensatory mobilization of venous capacitance blood (capacitance response) and net fluid absorption from tissue to blood were measured with a volumetric technique. Overall cardiovascular responses and plasma norepinephrine levels were measured.

RESULTS

Capacitance response was reduced (DW, 0.67 ± 0.05; C, 0.92 ± 0.06) and developed slower in DW (P < 0.01). Capacitance response was further reduced with increasing levels of HbA1c. Fluid absorption was almost halved in DW (P < 0.01). The initial vasoconstrictor response was reduced and developed slower in DW (P < 0.05). Arterial vasoconstriction was further reduced in the presence of microvascular complications (P < 0.05).

CONCLUSIONS

DW present with decreased and slower mobilization of venous capacitance blood and decreased net fluid absorption from tissue to blood during hypovolemic circulatory stress. Collectively, this indicates that DW are prone to hemodynamic instability, especially in the presence of microvascular complications and poor glycemic control.