January 22, 2014 | 2 Comments
The 6th Annual International Pediatric Nephrology Fellows Conference in Las Vegas, Nevada
Table of Contents
Hypertension Pearls: Blood pressure measurement in evaluation of childhood hypertension
Joseph Flynn, MD – Seattle Children’s Hospital, University of Washington School of Medicine
The focus of Dr. Flynn’s talk will focus on how blood pressure should and should not be measured. One of the most common errors is “digit preference”. This error occurs when the operator reports an inaccurate number, such as a systolic blood pressure of 127. Gradations on the sphygmomanometer are in even numbers (digits), so a reading of 127 cannot be accurate.
In a child, try to use the smaller blood pressure cuff whenever presented with 2 cuffs of varying sizes. Larger cuffs in children can result in falsely low blood pressure readings. Remember to use the bell of the stethoscope (not the diaphragm) when measuring blood pressure and never place the bell under the bladder of the cuff. Both will give a false reading.
If you have a patient with a high office BP reading, the Fourth Report recommends that you repeat the blood pressure at any time during the visit but emphasizes the use of a manual sphygmomanometer. The authors of Acta Paediatr 2011; 100: 775 suggest repeating the measurement at the very end of the visit. Thirty to 40% of children will suffer from white coat hypertension, making a repeat in-office BP measurement essential. In a child of less than 6 months of age, you can measure an arm or calf blood pressure with equal validity and precision.
Measuring blood pressure in children is increasingly important because 3% of children have hypertension (and more common in obese children). Childhood hypertension is a risk factor for hypertension in adulthood, which increases the risk of heart and kidney diseases. Auscultation is still the preferred method of measuring the blood pressure.
Improper cuff size is the most common cause of errors in pressure readings. Larger cuffs do not result in low BP readings, but smaller cuffs do. Be sure that the bladder of the cuff does not overlap with itself or you will get inaccurate readings. Of course, this is becoming increasingly difficult because obese children require larger cuffs (and childhood obesity is increasing).
Which blood pressure monitor should you use? The manual BP machine is still the best but time consuming. Oscillometric machines are automatic, can perform repeated measurements, and have an internal memory chip. Unfortunately, these machines don’t really measure blood pressure – they use mathematical formulas to compute systolic and diastolic blood pressure based on pulse. Each machine uses a different formula, so the blood pressure readings you get can be different based on the machine you use.
You can watch a NEJM video by Dr. Gaber Mubarak at http://www.youtube.com/watch?v=V_J-sLUp30g to learn the proper technique of measuring blood pressure.
The auscultatory gap occurs when you hear the first Korotkoff sound, then hear nothing, and then hear another Korotkoff sound. Gaps occur if you do not inflate the cuff quickly. Most physicians use the second sound as the systolic blood pressure, but this is a falsely low reading. Always use the first Korotkoff sound. Never reflate the BP cuff mid-way through the measuring process because it causes venous congestion, which will raise the diastolic blood pressure. The aneroid needle may not correspond to the actual Korotkoff sound. Thus, one should always use their “ears” and not their “eyes” to measure blood pressure.
Kenneth Andreoni, MD – University of Florida
Pediatric priority is given to any child under the age of 18. This age “discrimination” is listed in the National Organ Transplant Act, which makes it legal for physicians to give priority to patients of young age. A candidate can be listed at any time, even at 17 years and 364 days. In fact, if you place this hypothetical patient on the list, then s/he will have pediatric priority even though they receive their kidney after the age of 18. Once a patient has pediatric priority, they can keep if for long into adulthood. No labs are needed to place a pediatric patient on the wait list.
Donors are prioritized to pediatric recipients if they (the donor) are under the age of 35. Other factors that go into the donor prioritization for a pediatric recipient include the presence of diabetes, hypertension, and the donor cause of death. The Kidney Donor Profile Index (KDPI) will help surgeons quantify how “good” a donor kidney is. It is comprised of 10 variables/factors (age, race, HTN, DM, Cr, cause of death = stroke, height, weight, HCV, donor after cardiac death). A KDPI of less than 35% will be prioritized to the pediatric patient. An average donor kidney will be defined as a KDPI of 50%.
Currently the prioritization for receiving a kidney is as follows: multi-organ transplant > 0 mismatch > PRA greater than 80 > pediatric recipient > prior living donor recipient. Despite all these algorithms, a living donor kidney is still better than a deceased donor kidney.
Currently, children start to accrue “wait time” once they are placed on the waitlist. A kidney function measurement of a GFR < 20 ml/min is not needed to accrue time (as it currently is for adult patients). The new proposal for adults and pediatrics is to use the dialysis vintage time to accrue waitlist time. The longer a patient (adult or child) is on dialysis, the more time they accrue on the waitlist.
Renal Replacement Therapies Pearls
Timothy Bunchman, MD
Dr. Bunchman starts off with questions. He first starts off with a case of a woman with hyperkalemia, hypernatremia, hyperglycemia and an serum osmolarity of 488 mmol/L. The osmolarity of an HD solution is about 280. For PD, the range of osmolarities is 290-330, depending on the amount of glucose in the solution ([Na+] in PD fluid is about 132). For CRRT, the osmolarity is about 280. HD and CRRT solutions have similar osmolarities. This patient’s risk in dialysis is the major changes in osmolarity. Many of the fellows want to add extra sodium to the dialysate (whether it is via HD or CRRT). Generally, the maximum amount of the Na+ that can be added to dialysate on HD is about 150 (limited by conductivity). For CRRT the maximum [Na+] will depend on the pharmacy with which you work. Dr. Bunchman emphasized that an inefficient dialysis is needed so that the osmolarity can be decreased slowly while K+ is removed.
Dr. Bunchman now presents a case of a patient with Lithium and polypharmacy intoxication. The patient has EKG changes suggestive of Li+ toxicity and renal replacement therapy is needed. He asks the group how they would perform dialysis (modality and prescription). If CRRT is chosen, convection is usually preferred over diffusive. The higher the molecular weight, the more will be removed with convection rather than diffusion. If hemodialysis is chosen, either standard or high-flux can be used. Dr. Bunchman mentions EXTRIP (extrip.org as an organization that is trying to identify the ideal renal replacement prescriptions for various intoxications.
The final case is of a 2-day old boy with an inborn error of metabolism, resulting in ammonia of 1533, bicarbonate 14, Cr 0.9, normal K levels. Hyperammonemia is a medical emergency because the longer it remains elevated, the greater decrease in IQ a child will have for a longer period of time. The appropriate cocktail for hyperammonemia patients is in Picca et al Ped Nephrol 2001. It is composed of Na-benzoate + Na-phenylacetate + carnitine + arginine.
The most common peritoneal dialysis catheter is the 2-cuffed curled catheter. Other catheter shapes have been used but not that common today. Omentumectomy can be removed laparoscopically but can bleed because it is rich with blood vessels. Removal of the omentum, however, is thought to cause more incidences of infection; it is believed that the omentum serves an immunologic role within the peritoneal space.
It takes 6-8 weeks for the PD catheter to heal. If the catheter has to be used sooner, use smaller volumes (5 ml/kg/dwell). About 10% of the ideal volume can be used initially. Some catheters take longer to heal because children can induce mechanical trauma (tugging on the catheter).
Children can be trained to perform peritoneal dialysis, especially if the parent is illiterate. Always perform a home visit before initiating PD, especially to determine the number of siblings and pets. The latter two can affect the longevity of the catheter (siblings and pets are know to tug on the catheter).
Care of the exit site – neither alcohol or betadine are recommended. Alcohol will cause the PD catheter to crack. Soap and water work fine with topical antibiotics as need for exit-site infections. All major PD groups recommend against suturing at the exit site. The most common cause of a non-functional catheter is constipation. In these instances golytely or miralax 3x/day is required.