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3 Controversies inAntibiotic Prophylaxis inOrthopaedic Surgery
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23. Courtney MP, Melnic CM, Zimmer Z, Anari J, Lee G-C.Addition of vancomycin to cefazolin prophylaxis is associated with acute kidney injury after primary joint arthroplasty. Clin
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24. Clegg J, Soldaini E, McLoughlin RM, Rittenhouse S, Bagnoli F, Phogat S. Staphylococcus
aureus vaccine Research and Development: the past, present and future, including novel therapeutic strategies. Front Immunol. 2021;12:705360.
25. Zastrow RK, Huang H, Galatz LM, Saunders-Hao P, Poeran J, Moucha CS.Characteristics of
antibiotic prophylaxis and risk of surgical site infections in primary Total hip and knee arthroplasty. J Arthroplast. 2020;35:2581–9. https://doi.org/10.1016/j.arth.2020.04.025.
26. Berríos-Torres SI, Umscheid CA, Bratzler DW, Leas B, Stone EC, Kelz RR, Reinke CE,
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org/10.1001/jamasurg.2017.0904.
https://doi.org/10.1007/s11999- 014- 4062- 3.
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Chapter 4
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Perioperative Hemodynamic Monitoring
forHigh Risk Surgical Patients
RajMadhani, JingyuanBiaesch, andAustinPuchany
Introduction
The administration of anesthesia leads to physiologic perturbations, including
changes to hemodynamic regulation. These changes are primarily driven by loss of
sympathetic drive leading to decreased vascular tone, blood pressure, and cardiac
output [1–3]. This results in decreased perfusion and oxygenation of vital end
organs including the brain, heart, and kidneys, leading to anesthesia-related morbidity and mortality. Mortality rates related to or directly caused by anesthesia are currently estimated to be 0.82 in 100,000 surgical in-patients [4]. This is a vast
improvement since the 1940s when 100in 100,000 (1in 1000) healthy surgical
patients died from anesthesia [5].
In one meta-analysis of over 3000 cases, optimizing hemodynamics reduced
the number of major and minor postoperative gastrointestinal complications [6].
In another study, mean arterial pressures depressed by 30% led to an increased
risk of postoperative stroke in non-cardiac and non-neurosurgical procedures
[7]. Hypotension during non-cardiac surgeries has demonstrated an increased
risk of postoperative myocardial infarction and acute kidney injury as well [8].
Clearly, hemodynamics guided patient management plays an essential role in
achieving more positive outcomes, and in reducing poor perioperative courses.
To that end, proper hemodynamic data acquisition and interpretation is required.
R. Madhani (*) · J. Biaesch · A. Puchany
Department of Anesthesiology and Perioperative Medicine, University of Pittsburgh Medical
Center, Pittsburgh, PA, USA
e-mail: rxm656@jefferson.edu; maj6@upmc.edu; puchanyaj@upmc.edu
Switzerland AG 2024
J. Faintuch, S. Faintuch (eds.), Recent Strategies in High Risk Surgery,
https://doi.org/10.1007/978-3-031-56270-9_4
49© The Author(s), under exclusive license to Springer Nature
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R. Madhani et al.
Dening High-Risk Patients
With a wide array of hemodynamic monitoring tools available, deciding what
resources to use can often become overwhelming, inefcient, and expensive. As
with many aspects of medicine, a patient-specic approach can assist with these
decisions; thus, it is important to consider each patient on a case-by-case basis
to determine their monitoring needs. This starts with risk stratication by identifying the high-risk surgical patient. This subset of patients composes approximately 12% of all surgical patients but accounts for over 80% of surgical
mortality [9].
Risk Index Calculators
Traditionally, high-risk surgical patients were those with a greater than 5% chance
of mortality or twice the risk of mortality for a specic procedure when compared
to the general population [10]. The problem with this assumption is the focus on
mortality alone. As an aid to this narrow approach, a variety of risk index calculators
has been created to assess for perioperative complications. Many scores for surgical
use as well as for critical patients in general are available for online assessment at
mdcalc.com along with other more specic platforms such as the American College
of Surgeons—ACS-NSQIP.
American Society ofAnesthesiologists Physical Status
(ASA-PS)
The classic American Society of Anesthesiologists Physical Status (ASA-PS) is a
six-level classication system that establishes and communicates a patient’s preanesthesia medical comorbidities. While it does not explicitly calculate perioperative risk, it can be used in conjunction with other factors like type of surgery, age,
and frailty to assess risk. Table4.1 outlines this system [11]. The simplicity of this
classication system is also its weakness. It has been shown to have moderate interrater reliability among anesthesiologists and lower inter-rater reliability among physicians of different specialties [12, 13]. When there is discordance among raters, a
statistically signicant increase in 30-day and 1-year mortality of the patient has
been shown [13].
Numerous studies have demonstrated its utility despite the potential for discordance and the ASA’s original purpose. Class I patients have a 0.1% mortality rate,
while class V patients have a 93.3% mortality rate [10]. The classication system
has also demonstrated its ability to predict the risk of readmission [14].
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Table 4.1
American Society of Anesthesiologists Physical Status Classication [11]
ASA-PS Level Denition
I Normal healthy patient (non smoker, non drinker)
II Patient with mild systemic disease (uncomplicated pregnancy, well controlled
comorbidities)
III Patient with severe systemic disease (poorly controlled chronic diseases,
dialysis dependent renal failure)
IV Patient with severe systemic disease that is a constant threat to life (severe
cardiovascular event <3months, shock, low ejection fraction)
V Moribund patient not expected to survive without the surgery (ruptured aortic
aneurysm, major intracranial bleed, ischemic bowel)
VI Declared brain-dead
Revised Cardiac Risk Index (RCRI)
The Revised Cardiac Risk Index (RCRI) was created and validated in 1999 to assess
the risk of major adverse cardiac complications in patients undergoing noncardiac
surgery. These complications include myocardial infarction (MI), pulmonary
edema, ventricular brillation or primary cardiac arrest, and complete heart block.
This index uses six, independent factors namely, high-risk surgical procedure, history of ischemic heart disease, heart failure, cerebrovascular disease, preoperative
treatment with insulin, and preoperative serum creatinine greater than 2.0mg/dL
[15]. Having at least two of these predictive factors leads to elevated risk. RCRI
differentiates well between low and high-risk for noncardiac surgery. However, it
has limited ability in vascular surgery and kidney transplant [16, 17].
American College ofSurgeons National Surgical Quality
Improvement Program (ACS-NSQIP)
The American College of Surgeons National Surgical Quality Improvement Program
Universal Surgical Risk Calculator (ACS-NSQIP) was started in 2013 with data
acquired from 393 hospitals and over 1.4 million patients, and is continuously
improved. This tool considers 21 preoperative factors that cover demographics,
comorbidities, and procedures [18]. Similar to a few other scores, ACS-NSQIP factors in ASA-PS which was previously discussed. Additionally, this vast calculator
database factors in over 1500 unique Current Procedural Terminology codes when
determining surgical risks. ACS-NSQIP uses patient-specic inputs and generates
risk predictions for categories including cardiac complications such as cardiac arrest
or myocardial infarction, pneumonia, surgical site infection, urinary tract infection,
venous thromboembolism, renal failure, readmission, return to the operating room,
death, discharge to an advanced care facility, sepsis, and predicted length of stay.
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This risk stratication tool has the advantage of being comprehensive yet standardized. It considers a wide range of patient- and procedure-specic factors and
relays risk stratication for a variety of complications. It is important to note that
while ACS-NSQIP determines the risk of various cardiac complications, it does not
specically capture the risk associated with pulmonary edema and complete heart
block [19]. Thus, it cannot completely replace RCRI but can be used in conjunction
with it. Furthermore, the calculator was developed from patient databases acquired
from 10% of hospitals in the United States that conduct 30% of the country’s surgical procedures and has not been externally validated [18]. Despite these limitations,
ACS-NSQIP provides useful risk stratication data that can allow for strategic perioperative surgical planning.
Physiological andOperative Severity Score
fortheEnumeration ofMortality andMorbidity (POSSUM)
The POSSUM system utilizes both preoperative and intraoperative conditions to
determine postoperative morbidity and mortality [20]. Each category is scored 1–4
with a corresponding graded value. The summative score for the preoperative and
intraoperative variables is inserted into a formula and then morbidity and mortality
are calculated (Table4.2).
The POSSUM score is a complex mathematical equation, yet available at
mdcalc.com. It tends to overestimate morbidity and mortality in low-risk
patients and underestimate in extreme age and in emergency surgical situations
[19]. The Portsmouth-POSSUM (P-POSSUM) score is a modied equation of
the original POSSUM score that appears to mitigate this overestimation [21].
Because this score cannot be calculated until the end of the procedure, its utility
is limited to postoperative care. Though the score does not aid in the preoperative and intraoperative anticipation and preparation for hemodynamic monitoring, it does indicate which patients may need closer postoperative hemodynamic
monitoring. It is also non- exclusive to any surgical specialty and has been validated in multiple continents [19].
Table 4.2 Physiological and Operative Severity Score for the Enumeration of Mortality and
Morbidity (POSSUM score) [20]
Preoperative Variables Intraoperative Variables
Age, chest X-ray, cardiac and pulmonary conditions,
systolic blood pressure, pulse rate, Glasgow coma score,
blood urea nitrogen, Na+, K+, hemoglobin, white blood
cell count, electrocardiogram
Operative magnitude and urgency,
operations within 30days, blood
loss, peritoneal contamination,
malignancy
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Surgical Apgar Score (SAS)
SAS calculates the 30-day postoperative risk of morbidity and mortality for
general and vascular surgeries [22]. Each factor is given a graded score and the
total sum is added to determine risk. It has been widely validated however
appears to be less predictive in procedures where regional anesthesia is used
[23]. Similar to ACS- NSQIP, SAS has been studied in combination with ASA-PS
and found to augment postoperative risk prediction [24]. Analogous to POSSUM,
it is calculated postoperatively and thus cannot help with preoperative
preparation.
Functional Capacity Assessment
Functional capacity refers to the body’s ability to uptake oxygen for use in aerobic
metabolism to partake in activities of daily living [25]. Though it is mathematically
dened by the maximal oxygen uptake based on cardiac output and arteriovenous
oxygen difference at maximal exertion, it is typically represented as metabolic
equivalents (MET). One MET is equivalent to basal energy usage, and can be
thought of as the resting metabolic state within a given context. METs for activities
of daily living are quantied, available electronically, and used to assess a patient’s
functional capacity [26].
Less than four METs are determined to be high-risk for perioperative complications and require further preoperative cardiac evaluation, such as cardiopulmonary
exercise testing [27]. Subjective assessment of functional capacity involves asking
patients about their ability to complete common activities of daily living. For example, four METs are the equivalent of climbing two ights of stairs. Subjective,
patient-reported METs have demonstrated low sensitivity and thus cannot reliably
exclude poor functional capacity [28].
The gold standard for determining functional capacity is cardiopulmonary
exercise testing (CPET) [19]. This costly and time-consuming test does not represent a viable method for all patients undergoing surgery. An appropriate alternative would be to conduct an initial screening to determine who might need
CPET.The Duke Activity Status Index (DASI) represents this alternative. DASI
is a self- administered standardized questionnaire that has been validated as an
accurate surrogate for functional capacity assessment [29]. Each question corresponds to a weighted value which is added together to determine functional
status that positively correlates to METs. While it does not substitute for the
accuracy of the CPET, it decreases the total number of patients who may need
further testing.
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Biomarkers
Most postoperative MIs are “silent” as patients do not display typical ischemic symptoms [30]. 30-day mortality rates are elevated in patients who experience a postoperative MI, with the majority occurring within 48h of surgery. Thus, there is a need to
identify those patients who are potentially at increased risk for cardiac morbidity and
mortality. Natriuretic peptides, including B-type natriuretic peptide (BNP) and
N-terminal-pro BNP (NTP-BNP), and cardiac troponin are two extensively studied
biomarkers for perioperative risk stratication [19, 31]. Natriuretic peptides are
released in response to ventricular dysfunction stemming from cardiac wall stretching. Troponins are released in response to cardiac ischemia and wall damage [3].
Both preoperative and postoperative BNP and NTP-BNP measurements have
demonstrated signicant predictability for 30- and 180-day mortality and cardiac
morbidity in patients undergoing noncardiac surgery [32]. Threshold values for postoperative elevated risk include a BNP greater than 245pg/mL and NTP-BNP greater
than 718pg/mL.The same concept holds true for perioperative troponin measurements. Both elevated preoperative and postoperative troponin measurements are independent predictors of 30-day mortality [31, 33]. Finally, these biomarkers have
demonstrated augmentation of RCRI’s ability to predict adverse cardiac events [34].
Current studies do not demonstrate how knowledge of these biomarkers can lead to
directed therapeutics to improve outcomes [19]. One component of this solution will
likely be to maintain comprehensive perioperative hemodynamic monitoring.
Standard ASA Monitors
The American Society of Anesthesiologists has created standards for basic anesthetic monitoring to be used in all procedures that utilize general, regional, or monitored anesthetic care, except for laboring obstetric patients and practice of pain
management. The standard requirements include monitoring oxygenation, ventilation, circulation, and temperature [35]. These parameters are essential to the practice of anesthesiology. In higher-risk patients, a series of invasive and non-invasive
devices can augment basic monitoring and should be utilized on a case-by-case basis.
Oxygenation
Monitoring oxygenation allows for adequate oxygen delivery to end organs and prevents anaerobic respiration with consequent end-organ damage secondary to hypoxemia. To monitor oxygenation, quantitative pulse oximetry should be used. Pulse
oximeters measure blood oxygen saturation/SpO
of arterial hemoglobin [36]. Light-emitting probes are placed on the ngertip, earlobe,
or forehead; all are areas with high vascularity. SpO2 is generated by differential
, a surrogate for oxygen saturation
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absorption of red and near-infrared light as light passes through the artery overlying
the light-emitting diode. This generates a percent saturation of arterial hemoglobin.
When these devices were rst designed, they were generated using healthy volunteers
who had their arterial oxygen saturation altered from 70% to 100%, thus SpO2 readings less than 70% are unlikely to be reliable. Additionally, these probes rely on adequate circulation through the body part the probe is analyzing. Patients with impaired
peripheral circulation may have difculty getting accurate readings.
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Plethysmographic Waveform
This is another variable that can be collected with pulse oximeter and elucidates
heart rate and rhythm as well as gives insight into the volume status of the patient
[36, 37]. Volume status assessment by monitoring the pulse oximeter plethysmographic waveform amplitude (dPOP) allows for targeted volume resuscitation in
uid-responsive patients [38]. dPOP is a calculation of the variability seen in plethysmographs over the respiratory cycle and has been correlated with uid responsiveness. However, it is not easily calculated from a bedside monitor. Pleth variability
index (PVI), (Masimo Corp, Irvine, USA) is an accurate surrogate calculation for
dPOP [38, 39]. It is a continuous, automatic calculation based on the plethysmographic waveform and is used in conjunction with pulse oximetry monitoring.
Ventilation
To assess for ventilation qualitative clinical signs, such as chest excursion and auscultation may be benecial, but quantitative measurement is considered superior. This
can be achieved through the measurement of end-tidal carbon dioxide via capnography and/or capnometry. These devices respectively provide waveforms and numerical
measurements of end-tidal carbon dioxide, to evaluate the delivery of carbon dioxide
back to the lungs via circulation [35, 40]. Thus, clinicians can glean information about
a patient’s hemodynamic status, including cardiac output, from ventilation assessment.
Circulation
Every patient receiving anesthesia should have continuous electrocardiogram
(ECG) monitoring and arterial blood pressure measurements at least every 5min
[35]. Patients under general anesthesia should also have an additional mode of circulatory evaluation. This is most often done with plethysmographic waveform but
can also be achieved with pulse palpation, cardiac auscultation, monitoring of arterial blood pressure tracing, or ultrasound of peripheral pulses.
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ECG monitoring conveys information regarding the heart rate and rhythm, in
addition to allowing for the detection of cardiac ischemia and electrolyte derangements [41]. Typically, ve-electrode ECGs are used on patients in the operating
room, allowing for monitoring of all limb leads and at least one precordial lead.
Leads II and V5 are the most sensitive ones in detecting intraoperative myocardial
ischemia and are typically displayed on the bedside monitor. Limitations to ECG
analysis include improper lead placement and signal interference during electrocautery utilization.
Intraoperative hypotension increases the risk of postoperative morbidity and
mortality. Thus, reliable and frequent blood pressure measurements are required
during all surgeries. While the gold standard is arterial catheterization, cuff blood
pressure measurements are more routinely used [1]. Cuffs measure blood pressure
using oscillometry. This method relies on inating the cuff to supra-systolic pressures, slowly deating the cuff, and having a pressure transducer observe the oscillations produced as blood begins to ow within the artery [42]. The pressure at
which maximum oscillations occur is the measured mean arterial pressure. Each
cuff manufacturer has its own algorithm to calculate the systolic and diastolic pressures using the measured mean arterial pressure.
The cuff should be 80% of the length and 40% of the width of the extremity to
be measured. Cuffs too small will result in pressure improperly elevated, and cuffs
too large will result in pressure falsely low [43]. Measurements are typically done
on the upper arm to record brachial artery pressures. For obese patients, nding an
appropriately sized cuff may be challenging. Recently, it has been found that forearm cuff measurements may be more accurate than upper arm or lower leg cuff
pressures in obese patients [44].
R. Madhani et al.
Temperature
Induction of anesthesia results in peripheral vasodilation and a reduction in core
body temperature [45]. Patients can become hypothermic without appropriate
warming and proper temperature monitoring. This can lead to complications including altered drug metabolism, prolonged recovery, and coagulopathy. Core temperature can be measured from the nasopharynx, mouth, esophagus, or bladder.
Pulse Contour Analysis Devices
The pulmonary artery catheter and the Swan Ganz catheter have been employed far
less in recent decades due to high risks associated with placement and maintenance
[46]. According to the Society of Cardiovascular Anesthesiologists, the pulmonary
artery catheter was used by 68% of respondents 75% of the time, but that it is usually used with transesophageal echocardiography as an addition, and the decision is
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related to the geographical region and surgeon preference [47]. Pulmonary artery
catheters have decreased in sales through the years while newer pulse contour analysis devices have become more popular [48]. These are minimally invasive by simply using a nger blood pressure cuff or thoracic electrical impedance. The system
obtains a cardiac output value through calibration of heart rate multiplied by stroke
volume. Stroke volume is obtained through the measurement of pressure, such that
an estimated ow integrated over time is calculated to volume. The system provides
cardiac output, stroke volume, stroke volume variation, systemic vascular resistance, and mean arterial pressure.
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Customized Information
The system is enabled to receive specic demographic data to tailor the algorithm
for specic patients, such as providing an estimated cardiac output goal. The hemodynamic values can be applied to intraoperative hypotension and large volume
changes. They are relatively easy to use and monitor screens display easily interpreted trends. Well known products and manufacturers include FloTrac/Vigileo
technology (Edwards LifeSciences, Irvine, CA, USA), ProAQT/PulsioFlex (Pulsion
Medical Systems, Munich, Germany), LiDCOrapid system (Masimo Corp, Irvine,
CA, USA), and pressure recording and analytic method MostCare Up (Vygon,
Ecouen, France). ClearSight system (Edwards Lifesciences, Irvine, CA, USA) is
comprised the ClearSight nger cuff and EV1000 clinical platform. These products
often require an invasive arterial line, except for products similar to the ClearSight
nger cuff [49].
Using indirect calculations to change pressure to volume, the data tends to contain errors, notably in patients with already low systemic vascular resistance. This
combination would lead to even more inaccuracies in septic patients with depressed
systemic vascular resistance. However better algorithms are constantly emerging,
and the elimination of invasive access fosters the popularity of the pulse contour
devices.
Cerebral Hemodynamics
In intracranial neurosurgical, cardiothoracic, and large intra-abdominal vascular
cases, assessing cerebral autoregulation during surgery allows for not only immediate information during intraoperative maneuvers, but provide short to long term
benets, such as decreasing risk of stroke, postoperative delirium, and length of
hospital stay [50]. These include somatosensory evoked potential (SSEP), transcranial Doppler ultrasonography, brain tissue oxygen monitor, intracranial pressure
(ICP)—derived pressure reactivity index (PRx), brain tissue oxygen partial pressure
(PbtO2), electroencephalography(EEG), and near-infrared spectroscopy (NIRS).
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