Remembering the classics: Noninvasive blood pressure monitoring in neonates and infants.
Robert H. Friesen MD
It’s hard to believe but it’s already November and the holiday season is just around the corner! Today’s “remembering the classics” PAAD is written by my good friend Rob Friesen. I’ve asked Rob to pick one of his original articles and give us the back story of how and why he did this research. For those of you who don’t know him, Rob’s transformative research included the study of the hemodynamic effects of inhalational and intravenous anesthetic agents in the newborn and the effects of anesthetic agents on pulmonary vascular resistance in patients with pulmonary hypertension. An AAP Robert M Smith award winner, he is a model clinician-scientist, educator, and administrator. If you’d like to know more about his career, read his history of pediatric anesthesia interview: Twite MD, Ing RJ, et al. Outstanding contribution to pediatric anesthesiology: An interview with Dr. Robert H. Friesen. Paediatr Anaesth 2017; 27: 991-996 Myron Yaster MD
Original article:
Friesen RH, Lichtor JL. Indirect measurement of blood pressure in neonates and infants utilizing an automatic noninvasive oscillometric monitor. Anesth Analg 1981;60:742-745. PMID: 7197478
Technological innovation in anesthesia monitoring is an exciting and ongoing process that leads to better patient care and opportunities for clinical research. I saw the introduction of many new monitors during my career, and it was always fun to try something new, especially if it turned out to have a profound effect on the practice of pediatric anesthesia. I enjoyed reading Charlie Cote’s recent PAAD (9/27/2021) because the important introductions of capnography and pulse oximetry were major milestones during my early career. A similar event was the development of a device that automatically measured blood pressure non-invasively (NIBP).
When I started my career in the mid-1970s, we measured blood pressure in children and adults with a manually inflated BP cuff and auscultation of Korotkoff sounds over the brachial artery. In the operating room, this was accomplished by placing a slim rubber stethoscope head over the brachial artery under the BP cuff. Plastic tubing connected the stethoscope to our earpiece via a 3-way stopcock. When we wished to take a BP measurement, we switched the stopcock from the precordial stethoscope to the BP cuff stethoscope and inflated the cuff (see PS following the references at the bottom of the PAAD, MY). Unfortunately, this did not work in infants, who were too small for the available BP stethoscopes and in whom Korotkoff sounds were usually unobtainable. Instead, we taped a Doppler ultrasound probe over the brachial or radial artery, inflated a BP cuff and listened for the return of Doppler tones that indicated the systolic BP (1). Then we wrote the value on our hand-written anesthetic record. This worked most of the time, but the Doppler probe was easily dislodged by small movements, and the setup could be very temperamental.
This changed dramatically with the development of the NIBP monitor. The DINAMAP (Device for Indirect Non-invasive Automated Mean Arterial Pressure measurement) was introduced to clinical practice in 1979 (2). This monitor measured MAP oscillometrically and displayed computed MAP, systolic and diastolic BP, and HR at intervals. Wow! This made it easy to measure BP in our infant patients (although we still had to write the values down on our anesthetic record). But were those values accurate? The developers of the device had demonstrated good accuracy in adult patients, but as usual, pediatric patients were initially ignored. So, Lance Lichtor and I decided to study the accuracy of the monitor in infants and neonates. In this study (cited above as the PAAD), we compared 625 paired Doppler BP measurements with NIBP measurements in 27 preterm neonates, 24 term neonates, and 74 infants aged 5-26 weeks. We also compared 100 paired direct arterial pressure measurements with NIBP in an additional 20 babies aged 1 day to 22 weeks. We observed excellent correlation in every group and concluded that the device was consistently accurate in neonates and infants.
The results of that study and the ease of use and automaticity of the DINAMAP resulted in the rapid acceptance of NIBP in clinical pediatric practice. Furthermore, the capability to automatically record values on a connected device created many opportunities for clinical research, enabling us to study the hemodynamic effects of various anesthetics in infants and neonates (3-5) and in other groups in subsequent years. Fortunately, technologic innovation is ongoing and continues to improve our ability to monitor patients accurately, expand clinical research, and enhance the safety of pediatric anesthesia.
Robert Friesen MD
References
1. Janis KM, Kemmerer WT, Kirby RR. Intraoperative Doppler blood pressure measurements in infants. Anesthesiology 1970;33:361-363. PMID: 5454957
2. Yelderman M, Ream AK. Indirect measurement of mean blood pressure in the anesthetized patient. Anesthesiology 1979;50:253-256 PMID: 434517
3. Friesen RH, Lichtor JL. Cardiovascular depression during halothane anesthesia in infants: a study of three induction techniques. Anesth Analg 1982;61:42-45. PMID: 7198413
4. Friesen RH, Lichtor JL. Cardiovascular effects of inhalation induction with isoflurane in infants. Anesth Analg 1983;62:411-414. PMID: 6829944
5. Friesen RH, Henry DB. Cardiovascular changes in preterm neonates receiving isoflurane, halothane, fentanyl, and ketamine. Anesthesiology 1986;64:238-242. PMID: 3946810
PS: The 3-way stopcock used to switch between the precordial and blood pressure stethoscopes were often the source of anesthetic misadventures. One of my favorites: During a crisis and call for help, an assistant rushing into my OR plugged a blood line into the stopcock thinking it was the IV and pumped blood right into my ear! There really was no such thing as the “good old days”; we and our patients are so much better off than in the past. Myron Yaster MD