Evaluation of hemodynamic variations during anesthetic induction in treated hypertensive patients

Abstracts

JUSTIFICATIVA E OBJETIVOS: Devido à alta prevalência da hipertensão arterial sistêmica, ao aumento da expectativa de vida e ao aprimoramento dos métodos diagnósticos e das técnicas cirúrgicas, essa comorbidade tornar-se-á comum em pacientes cirúrgicos. O objetivo deste estudo foi avaliar o comportamento das variáveis hemodinâmicas dos pacientes hipertensos tratados durante a indução anestésica. MÉTODO: Estudo observacional sobre o comportamento das variáveis hemodinâmicas (pressão arterial sistólica, pressão arterial diastólica e freqüência cardíaca) durante a indução anestésica dos pacientes hipertensos e normotensos, escalados para operações eletivas submetidos à anestesia geral em quatro momentos consecutivos durante a indução anestésica: preparo (MP), fármaco (MF), laringoscopia/intubação (ML) e laringoscopia/intubação 5 min (ML5). RESULTADOS: A amostra foi composta por 128 pacientes distribuídos nos grupos de pacientes hipertensos (GH) e normotensos (GN). Houve diminuição da PAD no momento MF em ambos os grupos, com menor redução percentual no GH (18,3 ± 14,0% versus 23,0 ± 11,4%, p = 0,04). Houve aumento das PAS e PAD no momento ML em ambos os grupos, com menores elevações percentuais no GH (8,2 ± 16,3% versus 18,2 ± 21,2%, p < 0,01; 8,6 ± 20,2% versus 25,0 ± 27,9%, p < 0,01; respectivamente para PAS e PAD). Quanto à PAS e PAD, após ML5, e à FC não houve diferença entre os grupos. CONCLUSÕES: Os pacientes hipertensos tratados com níveis pressóricos controlados apresentaram maior estabilidade hemodinâmica durante a indução anestésica.

ANESTESIA; DOENÇAS; SISTEMA CARDIOVASCULAR

SCIENTIFIC ARTICLE

Walter Viterbo da Silva Neto^I; Giselli Santos Azevedo^II; Fernanda Oliveira Coelho^III; Eduardo Martins Netto^IV; Ana Marice Ladeia^V

^IMestre em Medicina e Saúde Humana pela Escola Bahiana de Medicina e Saúde Pública da Fundação Bahiana para o Desenvolvimento das Ciências; Anestesiologista do Hospital Espanhol e Rede Alfa de Hospitais/ Hospital da Bahia

^IIME₃ do CET/SBA do Hospital São Rafael

^IIIMR₁ de Nefrologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo

^IVDoutor em Medicina pela Universidade Federal da Bahia

^VProfessora Adjunta do Curso de Pós-Graduação em Medicina e Saúde Humana da Escola Bahiana de Medicina e Saúde Pública da Fundação Bahiana para o Desenvolvimento das Ciências; Doutora em Cardiologia pela Universidade Federal da Bahia

Correspondence to

SUMMARY

BACKGROUND AND OBJECTIVES: Due to the high prevalence of hypertension, the increase in life expectancy, and improvement of diagnostic methods and surgical techniques, this comorbidity will be increasingly more common in surgical patients. The objective of this study was to evaluate the behavior of the hemodynamic variables during anesthetic induction in treated hypertensive patients.

METHODS: This is an observational study on the behavior of hemodynamic parameters (systolic blood pressure, diastolic blood pressure, and heart rate) during the anesthetic induction of hypertensive and normotensive patients scheduled for elective surgeries under general anesthesia, at four moments: preparation (MP), drug (MD), laryngoscopy/intubation (ML), and 5 minutes after laryngoscopy/intubation (ML5).

RESULTS: The sample was composed of 128 patients divided into two groups: hypertensive (GH) and normotensive (GN). Diastolic blood pressure was reduced at MD in both groups, with a smaller percentage reduction in GH (18.3 ± 14.0% versus 23.0 ± 11.4%, p = 0.04). There was an increase in SBP and DBP at ML in both groups, with smaller percentage reductions in GH (8.2 ± 16.3% versus 18.2 ± 21.2%, p < 0.01; 8.6 ± 20.2% versus 25.0 ± 27.9%, p < 0.01, respectively for DBP and SBP). As for ML5, HR, SBP and DBP did not show significant differences between both groups.

CONCLUSIONS: Hypertensive patients under treatment and with controlled blood pressure levels demonstrated greater hemodynamic stability during anesthetic induction.

Key Words: ANESTHESIA: induction; CARDIOVASCULAR SYSTEM: hemodynamic changes; DISEASES: hypertension.

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: Debido a la alta prevalencia de la hipertensión arterial sistémica, al aumento de la expectativa de vida y al perfeccionamiento de los métodos diagnósticos y de las técnicas quirúrgicas, esa comorbidad se hará común en pacientes quirúrgicos. El objetivo de este estudio fue el de evaluar el comportamiento de las variables hemodinámicas de los pacientes hipertensos tratados durante la inducción anestésica.

MÉTODO: Estudio de observación sobre el comportamiento de las variables hemodinámicas (presión arterial sistólica, presión arterial diastólica y frecuencia cardíaca) durante la inducción anestésica de los pacientes hipertensos y normotensos, para operaciones electivas sometidos a anestesia general en cuatro momentos consecutivos durante la inducción anestésica: preparación (MP), fármaco (MF), laringoscopía/intubación (ML) y laringoscopía/intubación 5 min (ML5).

RESULTADOS: La muestra se compuso de 128 pacientes distribuidos en los grupos de pacientes hipertensos (GH) y normotensos (GN). Hubo una disminución de la PAD en el momento MF en ambos grupos, con menor reducción porcentual en el GH (18,3 ± 14,0% versus 23,0 ± 11,4%, p = 0,04). Hubo un aumento de las PAS y PAD en el momento ML en ambos grupos, con menores elevaciones de porcentaje en el GH (8,2 ± 16,3% versus 18,2 ± 21,2%, p < 0,01; 8,6 ± 20,2% versus 25,0 ± 27,9%, p < 0,01; respectivamente para PAS y PAD). En cuanto a la PAS y PAD, después de la ML5, y a la FC no hubo diferencia entre los grupos.

CONCLUSIONES: Los pacientes hipertensos tratados con niveles de presión controlados presentaron una mayor estabilidad hemodinámica durante la inducción anestésica.

INTRODUCTION

Hypertension is the most prevalent cardiovascular disorder, affecting approximately 1 billion individuals all around the world ¹. In Brazil, estimates indicate that the prevalence of hypertension varies from 22.3% to 43.9% ².

During anesthesia, most patients experience periods of hemodynamic instability, which healthy individuals can tolerate, but are usually catastrophic in hypertensive patients due to the wide pressure fluctuations and sympathetic hyperactivity ¹. Hypertension, especially when it is not treated, increases the risk of cardiovascular changes during the anesthetic-surgical procedure. On the other hand, pharmacological treatment of this condition is associated with possible interactions with anesthetic and adjuvant drugs ⁴. Besides, hypertensive individuals represent a challenge to the professionals involved with perioperative medicine because target-organ compromise (heart, brain, and kidneys), associated with variable functional changes, contribute to the increase in cardiac risk ⁵.

Because of the increased prevalence of hypertension, more rigorous definitions of the stages of hypertension, and evolution of anesthetic and anti-hypertensive drugs, associated with conflicting conclusions on the perioperative evolution of hypertensive patients, treated or not, the objective of this study was to evaluate the behavior of hemodynamic variables of treated hypertensive patients during anesthetic induction.

METHODS

After approval by the Ethics on Research Committee and signing of an informed consent, 128 patients scheduled for elective surgeries, regardless of the size of the procedure, undergoing general anesthesia at Hospital Agenor Paiva, Hospital Geral Roberto Santos e Hospital Espanhol, in Salvador, Bahia, Brazil, from December 2004 to October 2005, were selected for this study.

Inclusion criteria allowed normotensive (defined as individuals without prior diagnosis of hypertension and BP below 140 × 90 mmHg) and hypertensive (defined as individuals with a prior diagnosis of hypertension under treatment with anti-hypertensive medications), physical status ASA I and II, respectively, older than 18 years, of both genders, Mallampati I or II, and body mass index (BMI) up to 35 kg.m^-2. Patients with a diagnosis of liver, kidney, and cerebrovascular diseases, diabetes mellitus, asthma or chronic obstructive pulmonary disease, mental disorders of any etiology, or systemic disorders with cognitive compromise, illiterate, individuals whose time for intubation was greater than 30 seconds or in whom tracheal intubation was attempted more than once, or refused to participate in the study, were excluded.

On the day of the surgery each patient received as pre-anesthetic medication oral midazolam (0.1 mg.kg^-1) 60 minutes before the surgery, up to a maximal dose of 15 mg. Anti-hypertensive medications were maintained as prescribed by their physicians.

In the operating room, monitoring included continuous electrocardiogram, pulse oximetry, and non-invasive oscillometric blood pressure using a model 2010 Dixtal^® multiparametric monitor, after proper calibration. A peripheral vein was catheterized in one of the upper limbs with a 20G catheter for administration of drugs and hydration with NS (less than 500 mL of NS were infused until the end of the anesthetic induction).

Fentanyl (5 µg.kg^-1), lidocaine (1 mg.kg^-1), propofol (2.5 mg.kg^-1), and atracurium (0.5 mg.kg^-1) were used for anesthetic induction.

Initially, patients were oxygenated with a balloon mask with 100% O₂ for 3 minutes, followed by the administration of fentanyl and lidocaine (1 mL.s^-1). After one minute, the administration of propofol (1 mL.s^-1) was initiated. After the patient lost consciousness, a number 3 Guedel cannula was used for female patients and a number 4 for male patients; assisted ventilation was initiated under balloon mask with 100% oxygen and then the last drug, atracurium (1 mL.s^-1), was administered. After 2 minutes, when adequate anesthetic plane was confirmed by Bailey's criteria (centralized eyeball, miosis, and absence of pupillary reflexes to light), laryngoscopy was performed with a number 3 curved blade, for female patients, and number 4 for male patients. The patient was intubated within 30 seconds, on a single trial, by the same anesthesiologist, with a 7.5 endotracheal cannula, for female patients, and 8.0 for male patients.

Recording of hemodynamic parameters such as systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) was done by an independent researcher in four consecutive moments during anesthetic induction - preparation (MP): baseline control parameters determined before the administration of the anesthetics; drugs (MD): one minute after the administration of the anesthetics; laryngoscopy/intubation (ML): immediately after laryngoscopy/tracheal intubation; five minutes after laryngoscopy/intubation (ML5): five minutes after laryngoscopy/tracheal intubation.

Sample size was calculated considering a type I (alpha) error of 5% and a type II (beta) error of 20% with an statistic power of 80%, accepting up to 10 mmHg as a normal variation. Therefore, 128 was the number of patients necessary for the study (64 in each group).

The Student t test for independent samples (age, body mass index, and blood pressure levels), the Student t test for paired samples (blood pressure levels), and the Chi-square test (gender, race, and Mallampati index) were used to analyzed the data obtained. Statistical significance was defined as p < 0.05.

RESULTS

One-hundred and twenty-eight patients were divided into two groups, hypertensive (n = 64) and normotensive (n = 64). Both groups were homogenous regarding the demographic and clinical data (Table I).

Table II

According to the mean percentage variation at the different moments of anesthetic induction, a reduction in DBP was observed after the administration of the anesthetic drugs (MD) in both groups (Figure 1), with a smaller percentage reduction in the group of hypertensive patients (GH) (18.3 ± 14.0% versus 23.0 ± 11.4%, p = 0;04) (Figure 2). Systolic blood pressure showed no differences between the hypertensive and normotensive groups (19.5 ± 12.7% versus 19.0 ± 10.1%, p = 0.83 (Figures 3 and 4). An increase in SBP and DBP immediately after laryngoscopy and tracheal intubation (ML) were observed in both groups (Figures 1 and 3), with smaller percentage elevations in the group of hypertensive patients (GH) (8.2 ± 16.3% versus 18.2 ± 21.2%, p < 0.01; 8.6 ± 20.2% versus 25.0 ± 27.9%, p < 0.01; respectively for SBP and DBP) (Figures 2 and 4).

Differences in SBP and DBP between both groups 5 minutes after laryngoscopy and tracheal intubation (ML5) were not observed (0.4 ± 23.5% versus 7.0 ± 13.0%, p = 0.06; 1.0 ± 23.0% versus 7.2 ± 20.4%, p = 0.11; respectively for SBP and DBP) (Figures 1 and 3).

Heart rate did not show any differences between both groups throughout the study (Figure 5).

DISCUSSION

This study demonstrated that treated hypertensive patients modulate their hemodynamic responses within normal limits during anesthetic induction. Those observations are clinically very useful, since attenuation of hemodynamic fluctuations in treated hypertensive patients may lead to a decrease in the incidence of perioperative complications such as cardiac ischemia, strokes, and cardiac arrhythmias. Since hypertension has a high prevalence in the population, one can foresee how often professionals involved in perioperative medicine are faced with the hemodynamic consequences of the cardiovascular adaptations promoted by hypertension of any cause.

Since this is a study on hemodynamic variations during anesthetic induction, when several factors could affect the results, detailed inclusion and exclusion criteria were followed to improve methodological quality and minimize systematic errors. The groups being compared had similar demographic and hemodynamic characteristics, especially regarding the Mallampati index and physical status ASA. A possible confounding bias represented by hypoxemia, which increases blood pressure and heart rate ⁶, was ruled out by the determination of the oxygen saturation of hemoglobin during anesthetic induction, and it remained above 97% throughout the study (data not presented in Results).

The main pathophysiological characteristic of essential hypertension is the increase in systemic vascular resistance in the initial stages of the disease due to the increased neurogenic activity and, afterwards, to the arteriolar hypertrophy secondary to vascular remodeling. Thus, the vasodilator action of anesthetic drugs has a profound influence on blood pressure levels of hypertensive patients ⁷.

In the present study, fentanyl, lidocaine, propofol, and atracurium were the anesthetic agents used. The doses of fentanyl and atracurium used, 5 µg.kg^-1 and 0.5 mg.kg^-1 respectively, maintained hemodynamic stability ^8,9. However, studies on the suppression or attenuation of the hemodynamic response to laryngoscopy and tracheal intubation promoted by lidocaine have shown conflicting results, with some authors demonstrating protection against cardiac arrhythmias, hypertension, and tachycardia ⁸, while others observed a significant increase in cardiovascular parameters ^10,11.

Thus, since propofol is a known potent depressor of the cardiovascular system, it was the drug with the greatest impact on the hemodynamic changes observed in the present study. A reduction in blood pressure ranging from 18% to 23% was observed with a dose of 2.5 mg.kg^-1 of propofol, which is similar to the results of other authors ^12-15. This drug leads to hypotension by causing myocardial depression, mixed vasodilation, sympathetic inhibition, and depression of the baroreceptor reflex ¹⁶.

Prys-Roberts et al. ¹⁷ and Goldman & Caldera ¹⁸ demonstrated similar reduction in blood pressure in hypertensive and normotensive patients after the administration of anesthetic drugs, and such observation was confirmed by the present study regarding SBP, but not for DBP. In our study population, we did not observe a greater percentage reduction in DBP in hypertensive patients when compared with normotensive patients, probably due to vascular remodeling and increased sympathetic tonus by compensatory mechanisms caused directly by hypertension, which are responsible for the maintenance of an elevated systemic vascular resistance.

Laryngoscopy and tracheal intubation, common maneuvers in anesthetic procedures, can be associated with an increase in heart rate and blood pressure secondary to the sympathetic stimulation ¹⁹, and similar hemodynamic changes were also observed in this study. Data in the literature indicate a more pronounced hemodynamic response in hypertensive patients than in normotensive individuals ^17,20 secondary to adaptive cardiovascular changes and sympathetic hyperactivity ⁴. On the other hand, in the present study, greater percentage elevations in blood pressure in hypertensive patients than in normotensive individuals were not observed. Possible explanations include: only ASA II hypertensive patients, and most of them with the diagnosis of stage 1 (71.8%) hypertension, were included; systolic blood pressure greater than 180 mmHg and diastolic pressure greater than 110 mmHg are associated with a greater incidence of cardiovascular lability ^7,21. Besides, individuals included in the group of hypertensive patients were on long-term treatment for their condition, excluding the acute blood pressure control (less than 10 days of treatment), which is associated with greater perioperative variations in blood pressure ⁷. Another aspect to be considered would be that only patients Mallampati I and II were included in this study; difficult tracheal intubation is related with greater noxious stimuli and exacerbated adrenergic response.

Comparing the present study to the classical series of Prys-Roberts et al. ¹⁷ on anesthesia and hypertension, it was observed that patients considered normotensive in their series, nowadays would be classified as hypertensive. Besides, hypertensive patients (SBP varying from 150 to 235 mmHg and DBP from 90 to 130 mmHg), both treated (including those whose BP was under control) and non-treated hypertensive patients would be classified as hypertension stage 2 according to the VII JNC ¹, justifying the greater hemodynamic instability described by those authors.

The evaluation of all steps of anesthetic induction provided new evidence on the hemodynamic behavior in hypertensive patients that is similar to normotensive individuals, since evaluation of only two moments, control (MP) and immediately after laryngoscopy and tracheal intubation (ML), revealed greater percentage variation in the group of hypertensive patients. This could justify the exacerbated hemodynamic responses of hypertensive patients observed by some authors, such as Prys-Roberts et al. ¹⁷, who emphasized only those moments, and did not mention any changes after the administration of the anesthetic drugs in their study.

This study did not evaluate the contribution of each class of anti-hypertensive agents on the hemodynamic response during anesthetic induction. Additional studies, which should include a representative sample of the population, are necessary to generalize the results.

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Evaluation of hemodynamic variations during anesthetic induction in treated hypertensive patients

Evaluación de las variaciones hemodinámicas durante la inducción anestésica en pacientes hipertensos tratados

Publication Dates

• Publication in this collection
  14 Oct 2011
• Date of issue
  Aug 2008

History

• Accepted
  28 Apr 2008
• Received
  04 Dec 2007