Signs and symptoms of a diabetic coma are [7]:

•  Flushed face, rapid pulse and respirations
•  Dry skin and acetone breath
•  Nausea, vomiting
•  Headache and abdominal pain
•  Thirst
•  Shortness of breath
•  Coma

Other symptoms may include:

•  Increased thirst
•  Fever
•  Weakness
•  Increased micturition

• Anuria

  Main dangers during recompensation of diabetic coma are: hypovolaemia with oliguria -- anuria, dysequilibrium syndrome with cerebral edema and hypokalaemia. [ncbi.nlm.nih.gov]

  Joslin 2 states that in diabetic coma oliguria and moderate nitrogen retention are common but that anuria occurs only occasionally. [annals.org]

Work up consists of a detailed history (from the family/attendants if the patient is unconscious), physical examination and laboratory tests.

Laboratory Tests

•  Random blood sugar
•  Fasting blood sugar
•  Arterial blood gases
•  Complete blood count
•  Urea, creatinine and BUN
•  Serum electrolytes
•  Kidney function tests
•  Liver function tests
•  Ketone test 
•  Urinalysis

Imaging Studies

•  ECG
•  EEG
•  Chest X-ray

Test Results

On the basis of test results, a diagnosis can be made and treatment is immediately begun.

• Phenylalanine Increased

  The level of phenylalanine increased both at the concentration and the molar ratio, and tyrosine did only at the molar ratio. The significance of such changes in the plasma is discussed in relation to diabetic ketoacidosis or lactic acidosis. [ncbi.nlm.nih.gov]

Treatment depends upon the underlying cause. Symptomatic treatment, however, is immediately begun. Dehydration should be treated with normal saline and/or dextrose. Serum electrolytes should be corrected by intravenous infusions.

In case of hyperglycemia, insulin should be given. In case of hypoglycemic diabetic coma, intravenous dextrose should be administered.

Once the patient has sufficiently recovered, his diabetes medication should be optimised to prevent any recurrence of the coma.

Mortality attributed to HNC is variable, with rates from 10-50%, most likely depending upon the underlying illness or comorbidity [5].

The prognosis of advanced DKA leading to diabetic coma depends upon the treatment of the cause, i.e of the DKA itself. So if DKA is treated, the blood sugar level will go down and prognosis will be excellent.

Severe hypoglycemic diabetic coma also has a good prognosis, providing the patient is immediately brought to the ICU and his glucose levels along with serum electrolytes are corrected.

Complications

A serious post-treatment complication is cerebral edema, which may be related to therapy [6]. Other complications include hyperglycemia or hypoglycemic shock, lactic acidosis, speech or motor impairment, etc.

Diabetic coma develops when blood sugar levels exceed or not satisfy the tolerance capacity of the body. An exact cut off value is not decided upon, however, it is safe to say that a diabetic coma may arise if blood sugar levels become more than 5 times the normal random blood sugar limit (200 mg/dl).

There are three main causes of diabetic coma including severe diabetic hypoglycemia, diabetic ketoacidosis and hyperosmolar nonketotic coma.

Incidence

The incidence of diabetic ketoacidosis in developing countries is not known, but it may be higher than in industrialised nations [1].
The exact incidence of other types of diabetic coma is also not known.

Race

It should be noted that it has no known correlation or predilection to any particular race, ethnicity or region.

Age

Age is not a factor in disease manifestation, unless it is coupled with pre-existing illness. It may occur in young children suffering from type 1 diabetes mellitus or it may occur in old age patients in their 6th or 7th decade of life suffering from type 2 diabetes mellitus.

Diabetic coma may develop due to one of the following conditions:

Hyperosmolar nonketotic coma (HNC)

Typically, in clinical practise, HNC is seen in patients with type 2 diabetes mellitus and residual insulin secretion [2]. This type develops much more insidiously than other types because it usually does not present with vomiting or other clear signs. Upon blood sugar level evaluation, severe hyperglycemia is revealed, often with glucose as high as 1800mg/dL.

Diabetic ketoacidosis (DKA)

Causes of DKA in type I diabetes mellitus include the following [3]:

• Insulin deficiency, occurs in 25% of patients. 
• Bacterial infection
• Poor compliance with insulin 
• Medical, surgical or emotional stress
• Idiopathic

Causes of DKA in type II diabetes mellitus include the following [4]:

• Intercurrent illness 
• Medications 

So, if DKA is present and advances to a worse state characterised by increasing lethargy, dehydration and accompanied with vomiting and severe hyperglycemia, it may lead to shock and ultimately a diabetic coma.

Severe hypoglycemic coma

This type is much more common in patients suffering from type 1 diabetes mellitus. Although, it can be easily reversed by eating carbohydrate rich food, often the drop in blood sugar level is sudden and sharp, leading to unconsciousness. If left untreated, the patient may rapidly progress to a diabetic coma.

Frequent self-monitoring of blood glucose should reduce the frequency of hypoglycemic reactions, but not necessarily, as noted by the DCCT study [8].

Diabetic coma is a complication of long standing diabetes. By keeping the primary disease in check, many complication can be easily prevented.

Diabetic coma is a severe complication of long standing diabetes mellitus. It occurs when blood sugar levels go very high or low and the patient loses consciousness. This may occur in diabetics who do not keep their blood glucose levels in control, regardless of which type of diabetes they have.

It should be noted, however, that this is a reversible coma. With appropriate treatment and management, the patient may fully recover.

Definition

Diabetic coma is a reversible type of coma [9] that occurs in diabetics when their sugar level goes extremely high or low.

Cause

Diabetic coma occurs as a result of too little insulin, too much food, infectious causes, GI upset, etc [7].

Symptoms

It may present with the following symptoms [10]:

• Coma
• Convulsions
• Confusion
• Lethargy
• Thirst

Diagnosis

Diagnosis is clinical. It is made by a careful appraisal of the patient's health and by the evaluation of laboratory test results.

Treatment

Treatment of the disease depends upon the underlying cause. Once the cause is identified and appropriately treated, the complication should abate. 

1. Zargar AH, Wani AL, Masoodi SR, et al. Causes of mortality in diabetes mellitus:data from a tertiary teaching hospital in India. Postgrad Med J. May 2009;85(1003);227-32 [Medline]
2. Siperstein, MD. Diabetic Ketoacidosis and Hyperosmolar Coma. Endocrinol Metab Clin North Am. 21:415-32, 1992 
3. Bowden SA, Duck MM, Hoffman RP. Young children (<5 year) and adolescents (>12 year) with type I diabetes mellitus have low rate of partial remission: diabetic ketoacidosis is an important risk factor. Pediatr diabetes. June 2008 9:(3 Pt 1);197-201 [Medline]
4. Potenza M, Via MA, Yanagisawa RT. Excess thyroid hormone and carbohydrate metabolism. Endocr Pract. May-June 2009;15(3):254-72 [Medline]
5. Arieff Al, Carroll HJ: Non Ketotic Hyperosmolar Coma with Hyperglycemia. Clinical Features, Pathophysiology, renal functions, acid base balance, plasma cerebrospinal fluid equilibria, and the effects of therapy in 37 cases. Medicine 51:73-94, 1972
6. Durr JA, Hoffman WH, Sklar AH, El-Gammal T, Steinhart CM. Correlates of brain edema in uncontrolled IDDM. Diabetes 41:627-32,1992
7. George H, LCSW. Insulin Shock Diabetic Coma: To intervene and recognise diabetic emergencies. A review by Central Care Policy, Aug 2010.
8. The Diabetes Control and Complications Trial Research Group: The effect of intensive treatment of diabetes on the development and progression of long term complications in insulin-dependent diabetes mellitus. N Eng J Med 329:977-86,1993
9. Richard S. Irwin; James M. Rippe (2008). Irwin and Rippe's Intensive Care Medicine. Lippincott, Williams and Wilkins. pp 1256. ISBN 9780781791533. Retrieved 16th September, 2014
10. Buse JB, Polonsky KS, Burant CF. Type 2 diabetes mellitus. In: Melmed S, Polonsky KS, Larsen PR, Kronemberg HM, LarsenPR, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia. Pa: Saunders Elsevier;2011:chap 31