UBP 6.8 (Short Form): Renal – Arterial Venous Fistula

Question 1

Pre-operative Management:

How would you assess this patient’s volume status?

(A 72-year-old, 78 kg, male presents for AV fistula revision. He has a 6-year history of renal failure, has been on hemodialysis for the last 4 years, and was dialyzed yesterday through a subclavian line. His past medical history includes HTN, peripheral vascular disease, GERD, and type II diabetes mellitus. His medications include lisinopril, ASA, metformin, nexium, gentamicin, and a multivitamin. Vital Signs: HR = 94, BP = 162/89 mmHg, RR = 20, Temp = 37.6 C, Hgb = 10.2 gm/dL.)

Answer 1

Assessing the volume status of a patient with chronic hypertension and renal failure may prove challenging, since chronically hypertensive patients are more often predisposed toward intravascular volume depletion and patients with renal failure may be hypervolemic or hypovolemic depending on the time of last hemodialysis.

Keeping this in mind, I would begin my evaluation by reviewing the patient’s dialysis records to determine the frequency of dialysis, the amount of fluid removed during his last session, and his weight fluctuation over the last week.

I would review any available hemodynamic data, obtain a chest x-ray, and perform a clinical exam to identify signs of hypovolemia, such as mucous membranes, hypotension, and orthostasis; and signs of hypervolemia, such as pulmonary edema, hypertension, peripheral edema, and jugular venous distension.

Question 2

Pre-operative Management:

What are the systemic effects of chronic renal failure?

(A 72-year-old, 78 kg, male presents for AV fistula revision. He has a 6-year history of renal failure, has been on hemodialysis for the last 4 years, and was dialyzed yesterday through a subclavian line. His past medical history includes HTN, peripheral vascular disease, GERD, and type II diabetes mellitus. His medications include lisinopril, ASA, metformin, nexium, gentamicin, and a multivitamin. Vital Signs: HR = 94, BP = 162/89 mmHg, RR = 20, Temp = 37.6 C, Hgb = 10.2 gm/dL.)

Answer 2

Chronic renal failure is commonly associated with – metabolic derangements that include hyperkalemia, hyponatremia, hypocalcemia, hypermagnesemia, hypoalbuminemia, uric acid accumulation, and metabolic acidosis.

Long standing metabolic abnormalities can result in multiple systemic effects such as – peripheral and autonomic neuropathy, seizures, uremic encephalopathy, anorexia, delayed gastric emptying, insulin resistance, cardiac arrhythmias, conduction blocks, accelerated atherosclerosis (hypertension also contributes), and uremic pericarditis.

Renal retention of sodium and water combined with activation of the renin-angiotensin-aldosterine system often leads to hypertension, with subsequent – left ventricular hypertrophy, congestive heart failure (secondary to HTN, fluid overload, anemia, and metabolic acidosis), coronary artery disease (disordered fat and glucose metabolism contributes), and cerebral vascular disease.

Increased alveolar capillary permeability and volume overload may lead to pulmonary edema and restrictive pulmonary dysfunction.

Impaired phagocytosis leads to increased susceptibility to infections such as – tuberculosis, pneumococcus, and Hepatitis B or C.

Insufficient renal production of erythropoeitin, bone marrow suppression, gastrointestinal bleeding, hemodilution, and chronic infection leads to anemia when the GFR decreased to < 30 mL/min.

Finally, impaired platelet function may lead to bleeding, despite a normal platelet count, PT, and PTT.

Question 3

Pre-operative Management:

What lab work would you order prior to surgery?

(A 72-year-old, 78 kg, male presents for AV fistula revision. He has a 6-year history of renal failure, has been on hemodialysis for the last 4 years, and was dialyzed yesterday through a subclavian line. His past medical history includes HTN, peripheral vascular disease, GERD, and type II diabetes mellitus. His medications include lisinopril, ASA, metformin, nexium, gentamicin, and a multivitamin. Vital Signs: HR = 94, BP = 162/89 mmHg, RR = 20, Temp = 37.6 C, Hgb = 10.2 gm/dL.)

Answer 3

Considering this patient’s CRF, HTN, diabetes mellitus, anemia, and treatment with diuretics and dialysis, and considering all the comorbidities often associated with CRF (i.e. coronary artery disease, metabolic acidosis, and electrolyte disorders), I would order a chest x-ray to identify any pulmonary edema or cardiac hypertrophy;

a basic metabolic panel to identify any electrolyte abnormalities; and

an EKG to look for signs of myocardial ischemia, LVH, or conduction disturbances.

If regional anesthesia were being considered, I would also order coagulation studies.

Finally, I would review the patient’s dialysis record, predialysis and post-dialysis weights, and current weight.

Any additional lab work would be ordered as indicated by the history and physical exam.

Question 4

Pre-operative Management:

Is ordering a serum sodium level necessary?

(A 72-year-old, 78 kg, male presents for AV fistula revision. He has a 6-year history of renal failure, has been on hemodialysis for the last 4 years, and was dialyzed yesterday through a subclavian line. His past medical history includes HTN, peripheral vascular disease, GERD, and type II diabetes mellitus. His medications include lisinopril, ASA, metformin, nexium, gentamicin, and a multivitamin. Vital Signs: HR = 94, BP = 162/89 mmHg, RR = 20, Temp = 37.6 C, Hgb = 10.2 gm/dL.)

Answer 4

Obtaining a sodium level is necessary due to the association of hyponatremia with CRF.

While CRF results in sodium retention, the retention of a disproportionately larger volume of water can lead to hypervolemic, hypotonic, hyponatremia.

It is important to identify significant hyponatremia due to the associated risk of cardiopulmonary arrest, cerebral edema, seizures, coma, brain stem herniation, and death.

If his sodium level were low, I would review the patient’s previous sodium levels and examine him for any signs or symptoms of significant hyponatremia, such as nausea and vomiting, fatigue, lethargy, headache, confusion, anorexia, uncharacteristic irritability, restlessness, muscle weakness, or other changes in mental status (i.e. decreased level of consciousness).

Question 5

Pre-operative Management:

If the serum sodium were 130 mEq/L, would you cancel the case?

What if it were 120 mEq/L?

(A 72-year-old, 78 kg, male presents for AV fistula revision. He has a 6-year history of renal failure, has been on hemodialysis for the last 4 years, and was dialyzed yesterday through a subclavian line. His past medical history includes HTN, peripheral vascular disease, GERD, and type II diabetes mellitus. His medications include lisinopril, ASA, metformin, nexium, gentamicin, and a multivitamin. Vital Signs: HR = 94, BP = 162/89 mmHg, RR = 20, Temp = 37.6 C, Hgb = 10.2 gm/dL.)

Answer 5

Any decision to delay or cancel the case would depend, not only the laboratory value, but also on the urgency of the surgery;

the severity and rapidity of the drop in sodium;

the presence of signs or symptoms of hyponatremia;

and the presence, severity, and stability of any comorbid medical conditions.

Recognizing that brain swelling usually disappears at a serum sodium level of 130 mEq/L, my primary consideration would be the rapidity of the drop in his sodium level

(many authors recommend correcting the serum sodium level to > 130 mEq/L for elective cases).

Assuming the patient was asymptomatic and that this low sodium represented a more chronic condition, where the compensatory loss of intracellular solutes (mostly K+, Na+, and amino acids) has normalized cellular volume, I would proceed with this necessary (though not emergent) case.

If his serum sodium level were 120 mEq/L, I would delay the case for treatment, recognizing that serum sodium levels below 123 mEq/L (some sources say 120 mEq/L) may result in serious manifestations of hyponatremia (i.e. cerebral edema, cardiopulmonary arrest, seizures, coma, and brain stem herniation) despite the compensatory mechanisms associated with chronic hyponatremia.

Question 6

Pre-operative Management:

Obtaining intravenous access is difficult and the patient is becoming anxious. Would you administer an intramuscular dose of benzodiazepine?

(A 72-year-old, 78 kg, male presents for AV fistula revision. He has a 6-year history of renal failure, has been on hemodialysis for the last 4 years, and was dialyzed yesterday through a subclavian line. His past medical history includes HTN, peripheral vascular disease, GERD, and type II diabetes mellitus. His medications include lisinopril, ASA, metformin, nexium, gentamicin, and a multivitamin. Vital Signs: HR = 94, BP = 162/89 mmHg, RR = 20, Temp = 37.6 C, Hgb = 10.2 gm/dL.)

Answer 6

While I would consider administering a benzodiazepine to help reduce his anxiety and facilitate the placement of an intravenous catheter, I would avoid an intramuscular injection, if possible, due to the reduced muscle mass and uremic platelet dysfunction associated with CRF.

Instead, I would attempt to reassure the patient and administer a reduced dose of benzodiazepine via the oral route or his temporary dialysis catheter.

I would reduce the dosage because uremic-induced disruption of the blood-brain barrier and an increased free fraction of this extensively protein-bound drug are likely to result in an exaggerated clinical effect (acidic drugs experience reduced protein binding and basic drugs experience increased protein binding).

Question 7

Pre-operative Management:

You continue to struggle with intravenous access and the patient will not let you make any additional attempts.

Could you use the temporary dialysis catheter for the case?

(A 72-year-old, 78 kg, male presents for AV fistula revision. He has a 6-year history of renal failure, has been on hemodialysis for the last 4 years, and was dialyzed yesterday through a subclavian line. His past medical history includes HTN, peripheral vascular disease, GERD, and type II diabetes mellitus. His medications include lisinopril, ASA, metformin, nexium, gentamicin, and a multivitamin. Vital Signs: HR = 94, BP = 162/89 mmHg, RR = 20, Temp = 37.6 C, Hgb = 10.2 gm/dL.)

Answer 7

If the patient refused any further attempts to obtain intravenous access, I would consider utilizing his temporary dialysis catheter, recognizing that this would increase the risk of infection and/or clotting of this vital access site.

To prevent these complications, I would be very careful to access this site aseptically; leave the line heparinized and aspirate prior to connecting to an intravenous line; and re-heparinize the line and aseptically seal it at the time of disconnection.