Diabetic retinopathy at high altitude

Branch retinal artery occlusion secondary to high-altitude exposure and diabetic retinopathy: a case report

Background

To report a case of branch retinal artery occlusion (BRAO) secondary to high-altitude exposure and diabetic retinopathy (DR), and to characterize the retinal changes before and after hyperbaric oxygen (HBO) treatment.

Case presentation

We present a case of a 42-year-old man with DR who travelled to Tibet (in China, 3800 m/12467 ft. above mean sea level). The day after the end of his journey, the patient presented with acute, painless visual loss and visual field loss in his left eye. He was then diagnosed with BRAO, which is an acute blockage of blood flow. After HBO treatment, visual acuity and visual field were improved.

Conclusions

High-altitude exposure and DR may be considered as relevant risk factors for BRAO. The ophthalmologist should be aware that the BRAO might be a rare presenting sign of high-altitude retinopathy (HAR), particularly in patients with DR. HBO treatment can be considered as a choice for ophthalmologists on treatment against BRAO.

Wilderness Medical Society Clinical Practice Guidelines for Diabetes Management

The Wilderness Medical Society convened an expert panel in 2018 to develop a set of evidence-based guidelines for the treatment of type 1 and 2 diabetes, as well as the recognition, prevention, and treatment of complications of diabetes in wilderness athletes. We present a review of the classifications, pathophysiology, and evidence-based guidelines for planning and preventive measures, as well as best practice recommendations for both routine and urgent therapeutic management of diabetes and glycemic complications. These recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks or burdens for each recommendation.

High hemoglobin levels are associated with decreased risk of diabetic retinopathy in Korean type 2 diabetes

Anemia is an independent risk factor for the development of diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (DM). Hemoglobin levels may also be associated with DR. We investigated the association between hemoglobin levels and DR risk. This cross-sectional, population-based study utilized data from 2,123 type 2 DM patients aged ≥30 years who participated in the Korea National Health and Nutrition Examination Survey from 2008 to 2012. Participants underwent an ophthalmic examination, including fundus photographs. A multiple logistic regression analysis was performed to evaluate the relationship between hemoglobin levels and DR risk. The mean hemoglobin levels in patients with and without DR were 13.76 ± 0.12 and 14.33 ± 0.05 g/dL, respectively, with anemia observed in 16.2 (2.4)% and 7.8 (0.8)%, respectively. A 19% decrease in DR risk was found with a 1.0-g/dL increase in hemoglobin level. DR risk exhibited a decreasing trend with increasing hemoglobin levels (P for trend <0.0001). The adjusted odds ratio of DR was significantly lower in the highest hemoglobin quartile. Our findings indicate that high hemoglobin levels are significantly related to a decreased DR risk in Korean type 2 diabetes.

Diabetes, trekking and high altitude: recognizing and preparing for the risks

Although regular physical activity is encouraged for individuals with diabetes, exercise at high altitude increases risk for a number of potential complications. This review highlights our current understanding of the key physiological and clinical issues that accompany high-altitude travel and proposes basic clinical strategies to help overcome obstacles faced by trekkers with Type 1 or Type 2 diabetes. Although individuals with diabetes have adaptations to the hypoxia of high altitude (increased ventilation, heart rate, blood pressure and hormonal responses), elevated counter-regulatory hormones can impair glycaemic control, particularly if mountain sickness occurs. Moreover, high-altitude-induced anorexia and increased energy expenditure can predispose individuals to dysglycaemia unless careful adjustments in medication are performed. Frequent blood glucose monitoring is imperative, and results must be interpreted with caution because capillary blood glucose meter results may be less accurate at high elevations and low temperatures. It is also important to undergo pre-travel screening to rule out possible contraindications owing to chronic diabetes complications and make well-informed decisions about risks. Despite the risks, healthy, physically fit and well-prepared individuals with Type 1 or Type 2 diabetes who are capable of advanced self-management can be encouraged to participate in these activities and attain their summit goals. Moreover, trekking at high altitude can serve as an effective means to engage in physical activity and to increase confidence with fundamental diabetes self-management skills.

Physical activity at altitude: challenges for people with diabetes: a review

BACKGROUND

A growing number of subjects with diabetes take part in physical activities at altitude such as skiing, climbing, and trekking. Exercise under conditions of hypobaric hypoxia poses some unique challenges on subjects with diabetes, and the presence of diabetes can complicate safe and successful participation in mountain activities. Among others, altitude can alter glucoregulation. Furthermore, cold temperatures and altitude can complicate accurate reading of glucose monitoring equipment and storage of insulin. These factors potentially lead to dangerous hyperglycemia or hypoglycemia. Over the last years, more information has become available on this subject.

PURPOSE

To provide an up-to-date overview of the pathophysiological changes during physical activity at altitude and the potential problems related to diabetes, including the use of (continuous) blood glucose monitors and insulin pumps. To propose practical recommendations for preparations and travel to altitude for subjects with diabetes.

DATA SOURCES AND SYNTHESIS

We researched PubMed, medical textbooks, and related Internet sites, and extracted human studies and data based on relevance for diabetes, exercise, and altitude.

LIMITATIONS

Given the paucity of controlled trials regarding diabetes and altitude, we composed a narrative review and filled in areas lacking diabetes-specific studies with data obtained from nondiabetic subjects.

CONCLUSIONS

Subjects with diabetes can take part in activities at high, and even extreme, altitude. However, careful assessment of diabetes-related complications, optimal preparation, and adequate knowledge of glycemic regulation at altitude and altitude-related complications is needed.

Improved glycemic control in moderate altitude type II diabetic residents

Exposure to altitude hypoxia may elicit changes in glucose homeostasis. This work is designated to investigate the glycemic control in type II diabetic patients (DMII) permanently resident at moderately high altitude (2400 m), and to investigate whether the arterial oxygen-related parameters are different in DMII patients living at altitude compared to those living at low altitude. Blood glucose, HbA1c, hemoglobin concentration, and hematocrit (HCT) were measured in moderate altitude type II diabetics and compared with both altitude nondiabetics and diabetic patients living at normoxic and normobaric conditions. The data revealed that fasting blood glucose was lower in altitude diabetic patients compared to diabetics living at low altitude (157±33 mg/dL and 176.81±15.98 mg/dL, respectively, p<0.01). Also, glycemic control was improved in altitude diabetic patients, where their HbA1c was lower than the corresponding low altitude diabetic patients (8.68±0.79% and 9.30±1.02% respectively, p<0.01). Low oxygen tension at altitude was compensated in both diabetics and nondiabetics by a significant increase in both hemoglobin and HCT (17.33±0.72 mg/dL and 50.7±2.20%, respectively) compared to the corresponding groups living at low levels (15.53±0.55 mg/dL and 45.8±1.64%, respectively). The underlying disease neither affected the arterial oxygen tension (PaO2) nor oxygen saturation (SaO2), where insignificant correlations were observed between glucose, PaO2 (r=-0.06) and SaO2 (r=-0.2). These results suggest that moderate altitude may improve the glycemic control in type II diabetic patients compared to diabetics living at sea level.