Early Detection of Hypo- and Hypertension

 

Blood Pressure Curve

 

Blood pressure (BP) is one of the most important cardiovascular parameters in clinical practice in nearly every care area. Particularly in perioperative, critical and emergency care, blood pressure needs to be monitored repeatedly or even continuously to facilitate the best care for patients. However, up to now, beat-to-beat blood pressure monitoring requires invasive placement of an intra-arterial catheter, while standard noninvasive blood pressure monitoring is an intermittent, discontinuous measurement.

A nationally representative survey among Austrian and German physicians provides strong evidence that in only 18% of inpatient surgeries is blood pressure measured continuously with invasive catheters (IBP) - mainly in patients where cardiovascular instability is expected or repeated blood gas analyses are needed. In 26% of these cases the catheter is used only for the continuous monitoring of arterial pressure [1].

In all other surgeries (82%) intermittent noninvasive blood pressure (NBP) monitoring is the standard of care. This assumes that the intermittent measurements adequately represent the actual blood pressure at all times during a surgical procedure. Yet, up to 38% of all hypotensive episodes during surgeries may be missed by intermittent upper arm blood pressure readings [2], [3]. This can lead to delayed treatment or to completely missing hypotensive episodes. According to the survey and to the literature listed here, physicians want to extend noninvasive blood pressure to a continuous measurement in up to 40% of all cases.

 

Current Future Practice

 

The following medical rationale emphasizes the need of continuous, noninvasive arterial pressure (CNAP®):

 

  • Intraoperative hypotension during surgery significantly increases the 1-year post surgical mortality rate [4]. Clinical studies show that up to 56% of perioperative cardiac arrests are preceded by pronounced hypotension [5]. Beyond the perioperative setting, hypotensive episodes might also be overlooked in the emergency room, during procedural sedation for endoscopy and in intermediate care facilities.

 

  • Further, intraoperative hypotension might play a role in the development of postoperative ischemic stroke. Especially with mean blood pressure values decreasing more than 30% from baseline blood pressure, an association with post- operative ischemic stroke risks was observed.[6]

 

  • A retrospective analysis in over 1000 patients undergoing proximal femoral fracture repair showed that severe hyoptension occurred in 79,8% of all patients: "Among 1131 patients undergoing surgical repair of hip fracture, retrospective analysis found general anaesthesia to be associated with greater intra-operative hypotension than spinal anaesthesia."[7]

 

  • "Episodes of nocturnal hypotension in patients with recent ischemic stroke are common and difficult to detect with clinical cuff measurements. [...] This high frequency of nocturnal episodes observed in our study shows that, surely, almost half of our patients are inadvertently subjected to a significant risk of critical fall in cerebral perfusion."[8]

 

  • Cardiovascular instability in hypertensive patients undergoing anesthesia and surgery is a well-documented problem. In a review on carotid endarterectomy (CEA) Howell et al. demonstrated that these patients are prone to episodes of hypotension and hypertension in the intraoperative period. Carotid cross-clamping is frequently associated with a marked increase in arterial pressure. CEA combines the hemodynamic effects of anesthesia with those of surgical manipulation of the carotid bifurcation. Hypertension is seen in 25–58% of patients after endarterectomy and hypotension in 8–10% of patients [9].

 

  • In an analysis with automated data collection, Hartmann et al. investigated the incidence and clinical cause of hypotension after spinal anesthesia induction. In 46.8%, mean arterial pressure (MAP) decreased by 10% to 20%. In 8.2% of all cases, MAP decreased more than 30%. A decrease of MAP of more than 30% from baseline values within a 10 min.-interval in the first 30 min. after spinal anesthesia induction requires therapeutic intervention until 20 min. after the onset of the decrease. An episode of relevant hypotension was detected in 5.4%. In patients with known hypertension, the risk for a relevant decrease in blood pressure is nearly twofold [10].

 

  • In patients after myocardial infarction, perioperative hypotension increases the risk of a reinfarction. Furthermore, Rao et al. suggested that continuous blood pressure monitoring and aggressive therapy of perioperative hypotension reduces the risk of reinfarction during and following anesthesia [11].

 

  • Hypotension is the most common cardiovascular complication in the PACU (hypotension: 4.5%, hypertension 4.3%, dysrhythmias 2.8%) [12]. Similar results have been shown for intraoperative hypotension, where 4.4% (3.8 - 5.4%) of the patients developed hypotension [13].

 


 

References:

[1] von Skerst B: Market survey, N=198 physicians in Germany and Austria, Dec.2007 - Mar 2008, InnoTech Consult GmbH, Germany

[2] Dueck R, Jameson LC. Reliability of hypotension detection with noninvasive radial artery beat-to-beat versus upper arm cuff BP monitoring. Anesth Analg 2006, 102 Suppl:S10

[3] Ilies Ch, Kiskalt H., Siedenhans D,. Meybohm P., Steinfath M., Bein B., Hanß R.: Hypotensive episodes during cesarean section under spinal anesthesia are more frequently detected by a continuous noninvasive arterial pressure device then by intermittent oscillometric arterial pressure measurement submitted to peer reviewed journal.

[4] Monk TG, Saini V, Weldon BC, Sigl JC. Anesthetic management and one-year mortality after noncardiac surgery. Anesth Analg. 2005 Jan;100(1):4-10.

[5] Sprung J, Warner ME, Contreras ME et al. Predictors of Survival following Cardiac Arrest in Patients Undergoing Noncardiac Surgery. Anesthesiology 2003;99:259–69

[6] Bijker et al. Intraoperative Hypotension and Perioperative Ischemic Stroke after General Surgery: A Nested Case-control Study. Anesthesiology (2012) vol. 116 (3) pp. 658-64

[7] Wood und White. Anaesthesia for 1131 patients undergoing proximal femoral fracture repair: a retrospective, observational study of effects on blood pressure, fluid administration and perioperative anaemia. Anaesthesia (2011) vol. 66 (11) pp. 1017-22

[8] Castilla-Guerra et al. Nocturnal hypotension in patients after ischemic stroke: does it really matter? Eur J Intern Med (2011) vol. 22 (5) pp. 501-4

[9] Howell SJ. Carotid endarterectomy. British Journal of Anaesthesia 2007;99(1):119–31

[10] Hartmann B, Junger A, Klasen J. The Incidence and Risk Factors for Hypotension After Spinal Anesthesia Induction: An Analysis with Automated Data Collection. Anesth Analg 2002;94:1521–9

[11] Rao TLK et al. Reinfarction Following Anesthesia in Patients With Myocardial Infarction. Anesthesiology 1983;59:499-505

[12] Mayson KV et al. The Incidence of Postoperative Complications in the PACU. CJA Suppl A62 2005

[13] Cooper JB, Cullen DJ, Nemeskal R et al. Effects of Information Feedback and Pulse Oximetry on the Incidence of Anestheisa Complications. Anesthesiology 1987;67:686-694