Anesthesiology > Anesthesiology — Researchers analyzed data from a quarter-million surgery patientsby Jeff Minerd, Contributing Writer, MedPage Today May 30, 2015 Show
BERLIN -- Preoperative hypotension -- but not hypertension -- was associated with increased perioperative mortality risk, according to a large retrospective study presented at the Euroanaesthesia Congress. In the unadjusted analysis, both preoperative hypertension and hypotension were associated with mortality risk. However, after adjusting for risk factors and confounders, the risk associated with hypertension disappeared, reported lead investigator Robert Sanders, MBBS, PhD, FRCA, of the University of Wisconsin, and colleagues.
Sanders and colleagues analyzed data from more than 250,000 patients from the United Kingdom Clinical Practice Research Datalink who underwent noncardiac surgery. They looked for a link between preoperative blood pressure and 30-day perioperative mortality, adjusting for 29 risk factors including age, gender, race, comorbidities, surgical risk score, and end-organ vascular damage. For patients with a preoperative systolic blood pressure less than 100 mmHg, mortality risk increased by 40% (OR 1.40; 95% CI 1.05-1.86) in the adjusted analysis. For those with a preoperative diastolic BP less than 40 mmHg, mortality risk increased by approximately 250% (OR 2.49; 95% CI 1.43-4.33). As preoperative blood pressure decreased below the threshold of 100/40 mmHg, the odds of mortality increased. "While high blood pressure control is important for long-term health, high blood pressure itself does not impose a significant risk of postoperative death," the study authors said in a press release. "Rather the health consequences of uncontrolled high blood pressure convey other health risks -- therefore we still recommend that patients' blood pressure should be as well controlled as possible prior to surgery." "What these data tell us is that patients with low blood pressure before surgery are at higher risk. What we don't have is causality. There could be some other factor we haven't measured which is driving this risk. That will be the next step in our research," Sanders said in an interview with MedPage Today. "But we still think this is significant new information," Sanders said. "It will be important to understand how we can mitigate this risk to make sure these patients are less vulnerable." "This study is important because it makes us step back and recognize that hypotension, rather than hypertension, is the dominant problem," P.J. Devereaux, MD, PhD, of McMaster University in Hamilton, Ontario, told MedPage Today. Devereaux was not involved in the study. Physicians should be more aware of hypotension as a potential complication for surgical patients and have good procedures in place for measuring and monitoring it, Devereaux said. Advising patients to take all of their high blood pressure medicine the morning before surgery might need to be reconsidered in some cases, Devereaux said. "If you have an elderly patient who has fasted overnight and then takes three or four hypertension medications that morning, this might lead to a hypotensive episode that gets them into trouble." Richard Dutton, MD, an anesthesiologist at the University of Chicago and Chief Quality Officer for the American Society of Anesthesiologists, was more cautious in interpreting the study results. "This is a retrospective study, so it can show an association but it can't prove cause and effect," Dutton said in an interview with MedPage Today. "And you can't account for all the variables and potential confounders." Dutton was not involved in the study. Hypotensive patients may have fared worse in this study because they were sicker to begin with, Dutton said. A patient going into surgery with low blood pressure may be suffering from internal bleeding, dehydration, uncontrolled diabetes, malnourishment, or any number of maladies. "Still, this study increases my awareness of low blood pressure as a risk factor, and it raises the possibility that correcting low blood pressure might improve surgical outcomes," Dutton said. Disclosures No funding sources were reported for this research. Robert Sanders reported no financial relationships with industry. Neither P.J. Devereaux nor Richard Dutton disclosed financial relationships with industry. Richard Novak, MD is a Stanford physician board-certified in anesthesiology and internal medicine.Dr. Novak
is an Adjunct Clinical Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University, the Medical Director at Waverley Surgery Center in Palo Alto, California, and a member of the Associated Anesthesiologists Medical Group in Palo Alto, California.  DISCUSSION: During surgery, anesthesiologists balance their administration of drugs to the level of surgical stimulation the patient is experiencing. The placement of an endotracheal tube is an intense stimulus to an awake patient, but only a moderate stimulus to an anesthetized patient. After the placement of an endotracheal tube, a lag time of fifteen minutes to thirty minutes or more occurs prior to surgical incision. During this interval, the blood pressure sometimes sags. Let’s look at the anesthesia literature to learn what has been described about this problem. David Reich, et al of Mt. Sinai Hospital in New York queried the computerized anesthesia records of 4,096 patients undergoing general anesthesia and analyzed the incidence of hypotension in the period immediately after induction. (Predictors of hypotension after induction of general anesthesia Anesth Analg. 2005 Sep;101(3):622-8). The median blood pressure (MAP) was determined before anesthesia induction, during the first 5 minutes after induction, and also the period from 5-10 minutes after induction. Hypotension was defined as either (1) a mean arterial blood pressure (MAP) decrease of >40% and MAP Statistically significant predictors of hypotension after anesthetic induction included: ASA III-V, baseline MAP Dr. Reich wrote, “association with mortality alone was not reported in the manuscript but was nearly statistically significant (P = 0.066). The majority of our colleagues apparently believe that transient hypotension is inconsequential to outcomes. Although limited by the problems associated with retrospective studies, the results of our study provide preliminary evidence that runs counter to the prevailing wisdom regarding transient severe hypotension during general anesthesia.” What level of hypotension is unsafe for patients? The effects of hypotension in nonsurgical subjects was studied in 1954 (Finnerty, FA, Cerebral Hemodynamics during Cerebral Ischemia Induced by Acute Hypotension1Clin Invest. 1954 Sep; 33(9): 1227–1232). Young and old experimental subjects were subjected to increasing degrees of hypotension until clinical signs of cerebral ischemia developed. Hypotension was induced by intravenous administration of the anti-hypertensive medication hexamethonium. The authors discovered a linear relation between pre-hypotensive blood pressure and the level of induced hypotension that produced clinical signs of cerebral ischemia such as yawning, sighing, staring, confusion, inability to concentrate, inability to perform simple commands, nausea, dizziness, and involuntary body movements. Their data revealed that the safe level of hypotension was no lower than about 2/3 of the resting blood pressure before inducing hypotension. At 2/3 of their pre-procedure MAP, patients reached a threshold of clinical cerebral ischemia, with onset of yawning, sighing, staring, confusion, inability to concentrate, and inability to carry out simple commands. Because these studies were done on unanesthetized humans, it’s impossible to equate the data to patients with surgical anesthesia. Surgical patients have a different etiology for their hypotension, as well as reduced cerebral oxygen consumption from general anesthetic drugs. This explains why most surgical patients fail to manifest any cerebral damage resulting from episodes of hypotension occasionally following the induction of anesthesia. The problem of hypotension and refractory hypotension following induction of anesthesia is currently being studied in an ongoing clinical trial at the University of Iowa. (ClinicalTrials.gov identifier: NCT02416024, contact Kenichi Ueda, MD, ). Induction agents in this study will include 1.5 mg/kg propofol, 2 mcg/kg fentanyl, 100 mg lidocaine, and 0.6 mg/kg rocuronium. Inhaled anesthetic will be sevoflurane at 0.5 MAC with 5L/min of 100% oxygen starting at mask ventilation till 10 minutes after tracheal intubation. Blood pressure will be measured by a brachial cuff prior to induction and every minute after intubation for 10 minutes. If the systolic pressure drops below 90 mmHg or more than 25% from baseline, the patient will be classified in the study as “Hypotensive.” Conversely, if the patient’s systolic blood pressure does not drop below 90 mmHg more than 25% from baseline within 10 minutes of intubation, the patient will be classified as “Not Hypotensive.” In attempt to bring systolic blood pressure up to above 90 mmHg or more than 25% from baseline in “hypotensive” patients, the anesthetic provider will use 100 mcg of phenylephrine (or 5 mg ephedrine if heart rate < 50 bpm) within 10 minutes of intubation. If over 200 mcg of phenylephrine (or 10 mg ephedrine) has been used without a return of the systolic brachial blood pressure >90 mmHg or more than 25% from baseline, the patient will be classified in the study as “Refractory Hypotensive.” Look for the results of this trial to be published in years to come. Based on the data reviewed in this column, it seems advisable to maintain a patient’s mean arterial pressure at or above a level of 2/3 of their baseline pressure. What if the patient’s baseline blood pressure in their outpatient clinic notes is 120/80 (MAP=93) yet in the pre-operative room on admission to surgery their blood pressure is 150/90 (MAP=110)? This is not an uncommon occurrence, as blood pressure often spikes secondary to the inevitable anxiety which accompanies a pending surgery. Is the anesthesia provider compelled to maintain the blood pressure at 2/3 of 110 = 73 after induction, or compelled to maintain the blood pressure at 2/3 of 93 = 62 after induction? I can find no specific data to answer this question. In my experience, after the administration of 2 mg of intravenous midazolam the hypertensive 150/90 often decreases to the 120/80 (MAP=93) range. With this MAP = 93 value as the baseline blood pressure, 2/3 X 93 = 62 would be the lowest level of MAP I’d feel comfortable with. We’re trained to treat post-induction hypotension with a vasopressor. Typically phenylephrine 100 mcg will increase the pressure to its preinduction level. Some patients require more than one dose of phenylephrine. Let’s return to the management of your Clinical Case above.
The most popular posts for laypeople on The Anesthesia Consultant include: How Long Will It Take To Wake Up From General Anesthesia? Why Did Take Me So Long To Wake From General Anesthesia? Will I Have a Breathing Tube During Anesthesia? What Are the Common Anesthesia Medications? How Safe is Anesthesia in the 21st Century? Will I Be Nauseated After General Anesthesia? What Are the Anesthesia Risks For Children? The most popular posts for anesthesia professionals on The Anesthesia Consultant include: 10 Trends for the Future of Anesthesia Should You Cancel Anesthesia for a Potassium Level of 3.6? 12 Important Things to Know as You Near the End of Your Anesthesia Training Should You Cancel Surgery For a Blood Pressure = 178/108? Advice For Passing the Anesthesia Oral Board Exams What Personal Characteristics are Necessary to Become a Successful Anesthesiologist? Learn more about Rick Novak’s fiction writing at ricknovak.com by clicking on the picture below:Can you survive surgery with low blood pressure?However preoperative hypotension (low blood pressure) was associated with statistically significant increases in the odds of perioperative mortality. For patients with a systolic BP of below 100 mmHg, the likelihood of death increased by 40%.
How is low blood pressure treated during surgery?Ephedrine and phenylephrine
Ephedrine is the first-line treatment of intraoperative hypotension during general anesthesia. Ephedrine is an indirect alpha and beta-adrenergic agonist, whereas phenylephrine is a direct alpha-agonist of the sympathetic system.
Why did my blood pressure drop during anesthesia?Anesthetic drugs, which are used to put you to sleep during surgery, can affect your blood pressure. Changes can happen while you're being put to sleep and then when you're coming off of the drugs. In some people, anesthesia causes a significant drop in blood pressure.
What is considered a dangerously low blood pressure?Generally, if the blood pressure reading is under 90/60 mm Hg, it is abnormally low and is referred to as hypotension. Some adults regularly have blood pressure in the hypotensive range but have no symptoms and do not require treatment.
|
What happens when blood pressure drops too low during surgery
Related Posts
Copyright © 2024 themosti Inc.
