Saturday, March 11, 2017

Blood Pressure Monitoring Under Anesthesia in Companion Animals No. 21


Centers for Oral Care
New England & New York
Animal Dental Health Services
www.animaldentistrysolutions.com
No. 21~08March2017
DH DeForge, VMD
Fellow of the Academy of Veterinary Dentistry

Blood Pressure Monitoring Under Anesthesia in Companion Animals

“There are no safe anesthetic agents; there are no safe anesthetic procedures; there are only safe anesthetists.” – Robert M. Smith, MD

Abstract: Blood pressure monitoring under anesthesia is a very important parameter to evaluate circulatory changes that could cause hypotension.  Coupled with % hemoglobin concentration; electrocardiogram; end tidal C02 measurement; body temperature; and physical vital signs monitored by the anesthesia monitoring assistant--- the anesthesia journey can be well evaluated preventing unexpected difficulties from occurring.


Anesthesia Monitoring-Non-Invasive Blood Pressure: A Discussion


ACVA Monitoring Guidelines Update, 2009

Recommendations for monitoring anesthetized veterinary patient

CIRCULATION

1)     Palpation of peripheral pulse to determine rate, rhythm and quality, and evaluation of mucous membrane (MM) color and capillary refill time (CRT).
2)    Auscultation of heart beat (stethoscope; esophageal stethoscope or other audible heart monitor). Continuous (audible heart or pulse monitor) or intermittent monitoring of the heart rate and rhythm.
3)    Pulse oximetry to determine the % hemoglobin saturation. 
4)    Electrocardiogram (ECG) continuous display for detection of arrhythmias.
5)    Blood pressure:
a.     Non-invasive (indirect): oscillometric method: Doppler ultrasonic flow detector
Invasive (direct): arterial catheter connected to an aneroid manometer or to a transducer and oscilloscope.  Parks Medical Electronics/Oregon


The Doppler




Parks Medical Electroni

Sphygmomanometer





Assorted Blood Pressure Cuffs






Parks Medical Electronics, Inc


The Doppler is used for detecting blood flow acoustically and for making blood-pressure measurements indirectly using an inflatable cuff and sphygmomanometer.

The method is like that used on humans; the Doppler functions as a stethoscope. Systolic pressure is measured by reading the pressure on a sphygmomanometer when the blood flow sound first returns as cuff pressure is lowered. Normally, only systolic pressure is measured. Diastolic pressure measurements can be made, but they are not very accurate and require lots of subjective judgment.  Parks Medical Electronics, Inc
The Importance of Blood Pressure Measurement under anesthesia
Blood pressure should be routinely measured on any patient undergoing general anesthesia. The best way to prevent hypotension is to detect changes in blood pressure as soon as they begin.
The information obtained via patient monitoring is used to achieve three goals:
1.      Ensure adequate tissue perfusion with well-oxygenated blood
2.    Prevent pain before, during, and after a surgical procedure
3.    Provide a smooth and rapid recovery from anesthesia/surgery.
What is a Normal Blood Pressure Reading in Companion Animals?
What is a normal and what is an abnormal blood pressure reading in dogs and cats? Normal systolic arterial blood pressure ranges from: 110-160 mm of mercury (Hg). Normal diastolic arterial blood pressure ranges from: 60-90 mm of Hg. Normal MAP is in the range from 85-120 mm of Hg.
We cannot measure cerebral blood flow during anesthesia, so blood pressure, is all that is possible to measure the adequacy of cerebral blood flow and provide safe margins to prevent potentially damaging hypotension.

By monitoring the anesthetized patient, the anesthetist obtains information in the following areas:
Physiologic condition of the patient (eg, cardiovascular, respiratory, and metabolic systems)
Patient’s response to anesthesia, including anesthetic depth and level of analgesia.

In addition, assessing the status of the anesthetic equipment ensures its proper function, helping the anesthetist prevent iatrogenic crises that can jeopardize the patient’s health. Jeff Ko, DVM, MS, Diplomate ACVA


Commentary from Dr. DeForge:

The journey in anesthesia can be a journey with safety if there is a combination of excellent pre-anesthesia testing coupled with excellent anesthesia monitoring.  This report talks about one of the monitors of blood pressure called the Doppler System.
The Doppler system is excellent and is used commonly in conjunction with other blood pressure measuring systems in toy breeds and in the cat during anesthesia. 

This report has featured comments from Dr. Jeff Ko, a well known veterinary anesthesiologist; a position statement from the American College of Veterinary Anesthesiology; a discussion of the Parks Medical Doppler; and an introductory quote from the “Father of Pediatric Anesthesiology,” Robert M. Smith, MD.  Dr. Smith’s words should echo in all human anesthesia and veterinary anesthesia operatories as a reminder of the importance of the human hand in providing ultimate safety in anesthesia.