On “Maintenance Fluids” under Anesthesia: Isotonic or Bust!
Myron Yaster MD, Lynne G. Maxwell MD, and Justin L. Lockman MD MSEd
Generations of pediatric residents have been taught that IV fluid administration rate and composition should be based on the Holliday and Segar recommendations from 1957.[1] Every patient received either D5 0.45NS or D5 0.2NS (usually with potassium) as a “maintenance” fluid, with rates following the 4-2-1 rule. But as pediatricians who later studied anesthesiology, we were taught, based on the teachings of the late Dr. Fritz Berry,[2] to NEVER use hypotonic IV fluids perioperatively because of the very real risk of hyponatremia, particularly in surgical patients, because non-osmotic stimuli like pain, surgery, trauma, sepsis, lung disease, etc. may result in increased anti-diuretic hormone (ADH) activity which would only exaggerate the hyponatremia risk. And of course, the rate of fluid administration in the OR is necessarily not based on “4-2-1 maintenance” anyway because of bleeding and insensible losses and NPO deficits.
When I (MY) was a young faculty member at Hopkins in the 1980s, several episodes of symptomatic hyponatremia (seizures) in the PACU resulted in our banning hypotonic solutions like D5W, D5 0.2 or 0.45 Saline from the OR (just like our colleagues in the United Kingdom and Europe had already done). Instead, we used ONLY isotonic solutions like 0.9% Normal Saline (NS) or Ringers Lactate (LR). And then, in the early part of the 2000s, the use of normal saline, or better said abnormal saline, came into question because that solution had too much chloride (154 mEq) resulting in hyperchloremic metabolic alkalosis. What to do? As a group, we settled on a concerted push to remove LR and NS and switch to balanced salt solutions like Plasmalyte or Normosol.[3] To be honest, I thought that was the end of it. However, in Colorado virtually all patients coming to the OR from the inpatient units or ED were routinely being infused with hypotonic solutions. When I asked why, I would get a blank look of incredulity as to the stupidity of my question. I couldn’t fight the system so my work around was to throw out the hanging solutions and switch to isotonic solutions (with or without dextrose).
Today’s Pediatric Anesthesia Article of the Day is a randomized controlled clinical trial comparing hypotonic vs isotonic solutions in the emergency department. The results are not at all surprising, but do confirm what we already know: Holliday and Segar studied a group of healthy outpatient “volunteer” children and determined what rates and fluids were needed to keep their urine output and electrolytes normal. Yet patients coming to the OR (whether from the hospital or from home) are not healthy. Indeed, even those who start out healthy for elective procedures then undergo general anesthesia and surgery.
Original article
Kumar Ratnjeet, Pallavi Pallavi, Urmila Jhamb, Romit Saxena. 0.45% Versus 0.9% Saline in 5% Dextrose as Maintenance Fluids in Children Admitted With Acute Illness: A Randomized Control Trial. Pediatr Emerg Care . 2022 Sep 1;38(9):436-441. PMID: 36040464
We’ll let the authors speak for themselves: “The primary objective was to study change in serum sodium level at 24 hours in children receiving total IV fluid maintenance therapy as 0.45% or 0.9% normal saline in 5% dextrose. Secondary objectives of this study were to estimate change in serum sodium levels from the baseline to 48 or 72 hours, if IV fluids were continued, and to find incidence of hyponatremia and hypernatremia after administering these 2 types of maintenance fluids.” The results: “Fall in mean serum sodium from baseline was more with increasing duration of IV fluids until 24 hours in 0.45% saline group as compared with 0.9% saline group, which was statistically significant (P < 0.001). The incidence of mild and moderate hyponatremia was significantly more in hypotonic group at 12 hours (P < 0.001) and 24 hours (P < 0.001). However, there was no significant difference at 48 hours.”[4] They concluded: “The fall in serum sodium values was significant, and there was significant risk of hyponatremia with the use of hypotonic fluids at 12 and 24 hours. Hence, the use of isotonic fluids seems to be more appropriate among the hospitalized children.”[4]
One of us (JLL) works in a 72-bed PICU and can count on two hands the number of times I’ve ordered hypotonic fluids in a year – and all for patients with abnormal free water losses (think: diabetes insipidus, for example). We wonder what you do in your practice? Please send Myron your thoughts and we’ll post in reader response. And one more thing: For those of you who teach in the ORs, a really good exercise is to ask your students to build a table where the rows are the various solutions (LR, NS, ½ NS, plasmalyte, etc) and the columns are attributes (Na, Cl, K, Ca, pH, bicarbonate, osmoles, etc.) We think you will be shocked to find out how little your trainees/students know about this most basic information.
PS from Myron
Dr. Frederic (Fritz) Berry passed away a few days ago. Fritz was one of the giants in our profession and taught generations of anesthesiologists how to provide anesthesia to pediatric patients. His Refresher Course Lectures on perioperative fluid management at the annual meetings of the ASA were always sold out. Fritz was the author of two authorative (and readable) textbooks: Anesthetic Management of Difficult and Routine Pediatric Patients (1990) and Pediatrics for the Anesthesiologist (1993). In writing about his career as part of the history of pediatric anesthesia project, Christine Mai et al.[2] interviewed Fritz and concentrated on how and why he made fluid management the keystone of his thinking and teaching. Indeed, he thought “His early advocacy of balanced electrolyte solution for perioperative fluid resuscitation as his defining contribution”.[2]
From his interview: “I had a child who had a tonsillectomy and adenoidectomy and lost a fair amount of blood. Berry administered Ringer's lactate solution intraoperatively. In the recovery room, the surgeon immediately changed the postoperative fluids to D5 0.25 NS. ‘I was supervising a resident in a difficult case when 3 h later I got an emergency call to the recovery room and was told the child was seizing. The child was postictal when I got there’. The nurse reported that the child had copious diarrhea and postoperative vomiting and was given a large amount of D5 0.25 NS to replace ongoing losses. ‘Oh my lord!’ thought Berry. ‘This child was suffering from acute hyponatremia’. Berry intubated the child and administered 3% saline boluses at 2 ml·kg−1, which helped stop the seizures. Within the next 2 h, the child's sodium increased from 115 to 130 mm. He was extubated after 4 h, lucid and clinically stable. Given his own experience and several other reports of seizures due to iatrogenic hyponatremia, Berry became a passionate advocate for the use of balanced electrolyte solutions instead of hypotonic saline in the perioperative period”.[2] Thus, the findings of the publication which is the focus of today’s PAAD isn’t anything new and reminds us that those who forget history are doomed to repeat it. Fritz was a good friend, colleague and mentor. I and many of you will miss him. If you have thoughts about him that you’d like to share please send them to me and I will post in the PAAD.
References
1. Holliday, M.A. and W.E. Segar, The maintenance need for water in parenteral fluid therapy. Pediatrics, 1957. 19(5): p. 823-32.
2. Mai, C.L., et al., The development of pediatric fluid resuscitation: an interview with Dr. Frederic A. 'Fritz' Berry. Paediatr Anaesth, 2014. 24(2): p. 217-23.
3. McNab, S., et al., 140 mmol/L of sodium versus 77 mmol/L of sodium in maintenance intravenous fluid therapy for children in hospital (PIMS): a randomised controlled double-blind trial. Lancet, 2015. 385(9974): p. 1190-7.
4. Ratnjeet, K., et al., 0.45% Versus 0.9% Saline in 5% Dextrose as Maintenance Fluids in Children Admitted With Acute Illness: A Randomized Control Trial. Pediatr Emerg Care, 2022. 38(9): p. 436-441.