Pharmacologic drugs for controlled hypotension

ALM Resuscitation With Brain and Multiorgan Protection for Far-Forward Operations: Survival at Hypotensive Pressures

INTRODUCTION

Non-compressible torso hemorrhagic (NCTH) shock is the leading cause of potentially survivable trauma on the battlefield. New hypotensive drug therapies are urgently required to resuscitate and protect the heart and brain following NCTH. Our aim was to examine the strengths and limitations of permissive hypotension and discuss the development of small-volume adenosine, lidocaine, and Mg2+ (ALM) fluid resuscitation in rats and pigs.

MATERIALS AND METHODS

For review of permissive hypotension, a literature search was performed from inception up to November 2023 using PubMed, Cochrane, and Embase databases, with inclusion of animal studies, clinical trials and reviews with military and clinical relevance. For the preclinical study, adult female pigs underwent laparoscopic liver resection. After 30 minutes of bleeding, animals were resuscitated with 4 mL/kg 3% NaCl ± ALM bolus followed 60 minutes later with 4 h 3 mL/kg/h 0.9% NaCl ± ALM drip (n = 10 per group), then blood transfusion. Mean arterial pressure (MAP) and cardiac output (CO) were continuously measured via a left ventricular pressure catheter and pulmonary artery catheter, respectively. Systemic vascular resistance (SVR) was calculated using the formula: 80 × (MAP - CVP)/CI. Oxygen delivery was calculated as the product of CO and arterial oxygen content.

RESULTS

Targeting a MAP of ∼50 mmHg can be harmful or beneficial, depending on how CO and SVR are regulated. A theoretical example shows that for the same MAP of 50 mmHg, a higher CO and lower SVR can lead to a nearly 2-fold increase in O2 supply. We further show that in animal models of NCTH, 3% NaCl ALM bolus and 0.9% NaCl ALM drip induce a hypotensive, high flow, vasodilatory state with maintained tissue O2 supply and neuroprotection. ALM therapy increases survival by resuscitating the heart, reducing internal bleeding by correcting coagulopathy, and decreasing secondary injury.

CONCLUSIONS

In rat and pig models of NCTH, small-volume ALM therapy resuscitates at hypotensive pressures by increasing CO and reducing SVR. This strategy is associated with heart and brain protection and maintained tissue O2 delivery. Translational studies are required to determine reproducibility and optimal component dosing. ALM therapy may find wide utility in prehospital and far-forward military environments.

Efficacy and safety of intraoperative controlled hypotension: a systematic review and meta-analysis of randomised trials

BACKGROUND

Intraoperative controlled hypotension improves surgical field visibility by reducing blood loss (efficacy) but poses potential risks linked to organ hypoperfusion (safety). The use of controlled hypotension persists despite increasing evidence of associations between intraoperative inadvertent hypotension and adverse outcomes. Therefore, we tested the hypothesis that the focus and results of intraoperative controlled hypertension research differ across anaesthesia and surgery investigators because of differing priorities.

METHODS

We systematically reviewed randomised trials comparing controlled hypotension with usual care with trials categorised by investigators' affiliation.

RESULTS

We identified 48 eligible trials, of which 37 were conducted by anaesthesia investigators and 11 by surgery investigators. For the primary outcome, 54% of the anaesthesia-led trials focused on safety, whereas all (100%) surgery-led trials focused on efficacy (P=0.004). Compared with usual care, mean arterial pressure in controlled hypotension was 23% (95% confidence interval [CI] 17-29%) lower in anaesthesia trials and 30% (95% CI 14-37%) lower in surgery trials; estimated blood loss was 44% (95% CI 30-55%) less in anaesthesia trials and 38% (95% CI 30-49%) less in surgery trials. Overall, blood loss was reduced by 43% (95% CI 32-53%), and trial sequential analysis supported an efficacy conclusion. Mean arterial pressure and estimated blood loss reductions were associated (R2=0.41, P=0.002). All trials were underpowered for safety outcomes, and none adequately evaluated myocardial or renal injury.

CONCLUSIONS

Anaesthesia researchers prioritised safety outcomes, whereas surgery researchers emphasised efficacy in controlled hypotension trials. Controlled hypotension significantly reduces blood loss. In contrast, safety outcomes were poorly studied. Given increasing observational evidence linking inadvertent hypotension to myocardial and renal injury, the safety of controlled hypotension remains to be addressed.

SYSTEMATIC REVIEW PROTOCOL

PROSPERO (CRD42023450397).

Efficacy of Isoflurane-Remifentanil versus Propofol-Remifentanil on Controlled Hypotension and Surgeon Satisfaction in Rhinoplasty: A Single-Blind Clinical Trial Study

Background

Rhinoplasty is a complex but popular surgery in Iran. The main complications of the surgery are post-operative bleeding and nasal septal hematoma due to poor intra-operative controlled hypertension. This study aimed to compare the efficacy of isoflurane-remifentanil (I-R) versus propofol-remifentanil (P-R) to induce controlled hypotension and to assess surgeon satisfaction with each of these combinations during rhinoplasty.

Methods

In 2020-2021, a single-blind clinical study was conducted on 98 patients aged 18-50 years undergoing rhinoplasty at Mother and Child Hospital (Shiraz, Iran). Patients were randomly divided into P-R (n=48) and I-R (n=50) groups. Changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR) were assessed during surgery and in the recovery room. A questionnaire was used to evaluate the level of surgeon satisfaction. Data were analyzed using independent samples t test, Chi-square test, and repeated measures ANOVA with SPSS software. P<0.05 was considered statistically significant.

Results

Five minutes after anesthesia induction, the P-R combination had a greater effect on reducing SBP (P=0.010), DBP (P=0.007), MAP (P=0.003), and HR (P=0.026) than I-R. However, from the 40^th minute to the end of surgery and after 30 minutes of recovery, the I-R combination had a slightly better effect on blood pressure reduction than P-R. There was no difference in surgeon satisfaction with either of the two drug combinations.

Conclusion

Both P-R and I-R combinations are recommended to induce hypotension during rhinoplasty. However, I-R is more effective than P-R in inducing the desired controlled hypotension.

Effects of smoking on controlled hypotension with nitroglycerin during ear-nose-throat surgery

Background and Aim

In this study, the aim was to research the effects of smoking habits on controlled hypotension administered with nitroglycerin during ear-nose-throat surgery.

Materials and Methods

This study administered controlled hypotension with nitroglycerin and total intravenous anesthesia to a total of 80 patients undergoing septoplasty operations. The patients were divided into two groups of 40 non-smokers (Group 1) and 40 smokers (Group 2). Intravenous propofol infusion was used for anesthesia maintenance. Nitroglycerin with 0.25-1 μg/kg/min dose was titrated to provide controlled hypotension. During this process, the hemodynamic parameters of patients, total propofol and nitroglycerin amounts used, operation duration, and duration of controlled hypotension were recorded at the end of the operation. At the end of the operation, the surgeon assessed the lack of blood in the surgical field with Fromme Scale.

Results

Fromme scale values were significantly higher in Group 2 compared to Group 1. The MAP values at 10, 20, 30 min, and end of operation were lower, while 10- and 20-min heart rate values were higher in Group 2 compared to Group 1.

Conclusion

Nitroglycerin, chosen for controlled hypotension to reduce hemorrhage in the surgical field during nasal surgery, was shown to cause more pronounced hypotension and reflex tachycardia due to endothelial dysfunction linked to nicotine in patients who smoke. Despite lower pressure values in the smoking group, the negative effects of nicotine on platelet functions combined with similar effects of nitroglycerin to increase bleeding amounts.

The Effect of Desmopressin Intraoperatively on Hemorrhage During the Rhinoplasty Surgery

This clinical trial discusses the efficacy of premedication with desmopressin in the management of bleeding and clears the surgical field during rhinoplasty surgery. This study is a randomized, double-blinded placebo-control clinical trial. Seventy patients were enrolled in this study and divided into two equal intervention-control groups. Thirty minutes before surgery, the intervention group received 500 ml of normal saline containing 0.1 μg/kg desmopressin and, the control group received 500 ml of normal saline. According to the surgeon's opinion, the local distribution of bleeding was dramatically different in both groups. While DDAVP receivers had grade 1 or 2 bleeding (according to the FROMME-BOEZAART grading score), the control group had grade 3 or 4 bleeding, and this difference was statistically meaningful. It seems that intravenous DDAVP can reduce bleeding and clear the surgical field during rhinoplasty surgery, but further studies are needed to determine the exact role and dose of the DDAVP.

Application of Controlled Hypotension During Surgery for Spinal Metastasis

With advances in tumor treatment, metastasis to bone is increasing, and surgery has become the only choice for most terminal patients. However, spinal surgery has a high risk and is prone to heavy bleeding. Controlled hypotension during surgery has outstanding advantages in reducing intraoperative bleeding and ensuring a clear field of vision, thus avoiding damage to important nerves and vessels. Antihypertensive drugs should be carefully selected after considering the patient's age, different diseases, etc, and a single or combined regimen can be used. Hypotension also inevitably leads to a decrease in perfusion of important organs, so the threshold of hypotension and the maintenance time of hypotension should be strictly limited, and the monitoring of important organs during the operation is particularly important. Information such as blood perfusion, blood oxygen saturation, cardiac output, and neurophysiological conduction potential changes should be obtained in a timely fashion, which will help to reduce the risk of hypotension. In short, when applying controlled hypotension, it is necessary to choose an appropriate threshold and duration, and appropriate monitoring should be conducted during the operation to ensure the safety of the patient.

Desmopressin effects on bleeding during functional endoscopic sinus surgery on patients with chronic rhinosinusitis

OBJECTIVE

In this study we aimed to determine whether Desmopressin (DDAVP) can alter bleeding and improves surgeon visual field and decrease operation time or lessen use of anesthesiology medication in a clinical trial study.

METHOD

This study is a randomized clinical trial using the permuted block randomization method. 44 patients were enrolled in study and divided into two equal intervention-control groups. The intervention group received maximum dose of 0/2 micrograms per kg of DDAVP. In the control group, 30 min before the surgery, 100 ml of normal saline will be injected.

RESULTS

The amount of bleeding was 517/17 cc in control group during surgery while it was 387/72 cc in group receiving DDAVP which is significantly lower. The satisfaction of surgeon regarding suitable visual field was 6/45 in control group while it was 3/77 in DDAVP receivers which is lower.

CONCLUSION

It seems that intravenous DDAVP can reduce bleeding during surgery and offer an enhanced vision for surgeon during surgery but it has no potential efficacy on reduction of period of surgery and need for anesthesiology medication like remifentanil and isoflurane.

Analgesia and sedation post-coronary artery bypass graft surgery: a review of the literature

This review aimed to study the role of analgesia and sedation after coronary artery bypass graft (CABG) surgery, regarding pain management, assisted respiration, overall postoperative health care, and hospitalization. Data were collected from Pubmed, Scopus, and Cochrane databases. The following terms were used for the search: “analgesia”, “sedation”, “coronary artery bypass grafting”, CABG”, and “opioids”. Articles between the years 1988 and 2018 were evaluated. Several opioid and non-opioid analgesics used to relieve surgical pain are regarded as critical risk factors for developing pulmonary and cardiovascular complications in all kinds of thoracic surgery, especially CABG procedures. Effective pain management in post-CABG patients is largely dependent on effective pain assessment, type of sedatives and analgesics administered, and evaluation of their effects on pain relief. A significant challenge is to determine adequate amounts of administered analgesics and sedatives for postoperative CABG patients, because patients often order more sedatives and analgesics than needed. The pain management process is deemed successful when patients feel comfortable after surgery, with no negative side effects. However, postoperative pain management patterns have not included many modern methods such as patient-controlled analgesia, and postoperative pain management drugs are still limited to a restricted range of opioid and non-opioid analgesics.

The Effects of Oral Atenolol or Enalapril Premedication on Blood Loss and Hypotensive Anesthesia in Orthognathic Surgery

PURPOSE

The aim of this study was to evaluate the effects of premedication with oral atenolol or enalapril, in combination with remifentanil under sevoflurane anesthesia, on intraoperative blood loss by achieving adequate deliberate hypotension (DH) during orthognathic surgery. Furthermore, we investigated the impact thereof on the amount of nitroglycerin (NTG) administered as an adjuvant agent.

MATERIALS AND METHODS

Seventy-three patients undergoing orthognathic surgery were randomly allocated into one of three groups: an angiotensin converting enzyme inhibitor group (Group A, n=24) with enalapril 10 mg, a β blocker group (Group B, n=24) with atenolol 25 mg, or a control group (Group C, n=25) with placebo. All patients were premedicated orally 1 h before the induction of anesthesia. NTG was the only adjuvant agent used to achieve DH when mean arterial blood pressure (MAP) was not controlled, despite the administration of the maximum remifentanil dose (0.3 μg kg⁻¹ min⁻¹) with sevoflurane.

RESULTS

Seventy-two patients completed the study. Blood loss was significantly reduced in Group A, compared to Group C (adjusted p=0.045). Over the target range of MAP percentage during DH was significantly higher in Group C than in Groups A and B (adjusted p-values=0.007 and 0.006, respectively). The total amount of NTG administered was significantly less in Group A than Group C (adjusted p=0.015).

CONCLUSION

Premedication with enalapril (10 mg) combined with remifentanil under sevoflurane anesthesia attenuated blood loss and achieved satisfactory DH during orthognathic surgery. Furthermore, the amount of NTG was reduced during the surgery.

Predictors of arterial blood pressure control during deliberate hypotension with sodium nitroprusside in children

BACKGROUND

Sodium nitroprusside (SNP) is used to decrease arterial blood pressure (BP) during certain surgical procedures. There are limited data regarding efficacy of BP control with SNP. There are no data on patient and clinician factors that affect BP control. We evaluated the dose-response relationship of SNP in infants and children undergoing major surgery and performed a quantitative assessment of BP control.

METHODS

One hundred fifty-three subjects at 7 sites received a blinded infusion followed by open-label SNP during operative procedures requiring controlled hypotension. SNP was administered by continuous infusion and titrated to maintain BP control (mean arterial BP [MAP] within ±10% of clinician-defined target). BP was recorded using an arterial catheter. Statistical process control methodology was used to quantify BP control. A multivariable model assessed the effects of patient and procedural factors.

RESULTS

BP was controlled an average 45.4% (SD 23.9%; 95% CI, 41.5%-49.18%) of the time. Larger changes in infusion rate were associated with worse BP control (7.99% less control for 1 μg·kg·min increase in average titration size, P = 0.0009). A larger difference between a patient's baseline and target MAP predicted worse BP control (0.93% worse control per 1-mm Hg increase in MAP difference, P = 0.0013). Both effects persisted in multivariable models.

CONCLUSIONS

SNP was effective in reducing BP. However, BP was within the target range less than half of the time. No clinician or patient factors were predictive of BP control, although 2 inverse relationships were identified. These relationships require additional study and may be best coupled with exposure-response modeling to propose improved dosing strategies when using SNP for controlled hypotension in the pediatric population.

Effects of preoperative β-blocker on blood loss and blood transfusion during spinal surgeries with sodium nitroprusside-controlled hypotension

BACKGROUND

The present study sought to determine whether premedication with oral β-blocker before hypotensive anesthesia with sodium nitroprusside could improve the quality of surgical field, decrease the blood loss, and decrease the need for homologous blood transfusion and duration of surgery.

METHODS

Eighty patients scheduled for spinal fixation surgery were included in a prospective, randomized, double-blinded study. Patients were classified into two groups: Group I received oral atenolol 50 mg twice one day before surgery; and Group II received placebo tablets identical in appearance to atenolol tablets for the same period and interval. All patients in both the groups received intraoperative sodium nitroprusside (SNP) as a hypotensive agent. Hemodynamic variables, amount of sodium nitroprusside used, quality of surgical field, and the amount of homologous blood transfusion and blood loss were compared between groups.

RESULTS

Heart rate and amount of SNP used were significantly less (P<0.0001) in the atenolol group, but no significant difference was found in intraoperative mean arterial blood pressure (MABP) between the two groups. The time of surgeries was significantly shorter in Group I than in Group II (185±15.21 vs 225±12.61 min), P<0.0001. The quality of surgical field was better in Group I than in Group II in all times of measurements, P<0.0001. The amount of blood loss and the amount of packed red blood cells transfused were significantly less in Group I than in Group II, P<0.0001. No clinically significant complications were observed in either group.

CONCLUSION

Premedication with oral atenolol 50 mg twice/day for one day before hypotensive anesthesia with SNP during spinal surgeries seems to be clinically safe and effective to reduce heart rate, amount of SNP used, amount of blood loss, and amount of blood transfused with better quality of surgical field.

Effects of preoperative oral beta blocker versus intraoperative nitroprusside or esmolol on quality of surgical field during tympanoplasty

STUDY OBJECTIVE

To determine whether orally administered atenolol provides an optimal surgical field in comparison to intravenous sodium nitroprusside or esmolol during tympanoplasty.

DESIGN

Randomized, double-blinded study.

SETTING

Operating room in a university hospital.

PATIENTS

105 ASA physical status 1 and 2 adult patients undergoing tympanoplasty.

INTERVENTIONS

Patients were randomized to three groups to receive either oral atenolol 50 mg twice daily for one day prior to surgery (Group I), intraoperative nitroprusside infusion (Group II), or intraoperative esmolol infusion (Group III).

MEASUREMENTS

Quality of the operative field, mean arterial pressure, and heart rate were assessed. Blood gases, liver enzymes, cardiac troponin I, creatine kinase isoenzyme-MB release, blood urea nitrogen, and creatinine concentrations also were measured.

MAIN RESULTS

Time to achieve target surgical field was significantly reduced in the atenolol group versus the other groups (8.3 ± 3.2, 28.2 ± 6.4, and 17.2 ± 5.3 min, respectively). Heart rate significantly decreased in the atenolol and esmolol groups versus the nitroprusside group (P < 0.0001). Mean arterial pressure after extubation and frequency of rebound hypertension were comparable in the groups. No significant changes in cardiac enzymes, renal and hepatic function, or acid-base status were noted.

CONCLUSIONS

Although the three drugs are acceptable for obtaining an optimum surgical field, preoperative oral beta blocker appeared to be rapid in onset and was simpler to implement.

Small bolus of esmolol effectively prevents sodium nitroprusside-induced reflex tachycardia without adversely affecting blood pressure

PURPOSE

Hypotensive anesthesia with sodium nitroprusside (SNP) often is associated with reflex tachycardia. The purpose of this study was to investigate whether a small bolus of esmolol could counteract SNP-induced reflex tachycardia and sympathetic activation without affecting blood pressure.

MATERIALS AND METHODS

Using a time-series study design, 27 healthy young patients scheduled for mandibular osteotomy were enrolled in this study. General anesthesia was maintained with 2% sevoflurane and 67% nitrous oxide in oxygen. SNP was administered to decrease the mean arterial pressure to 55 to 65 mm Hg. When heart rate (HR) increased reflexively to higher than 95 beats/min from SNP-induced hypotension, esmolol 0.5 mg/kg was given. Blood pressure and HR were measured, and the low-frequency component (0.04 to 0.15 Hz) of systolic blood pressure variability and high-frequency component (0.15 to 0.4 Hz) of HR variability were calculated to evaluate the autonomic condition. Data were analyzed using 1-way analysis of variance after multiple comparisons or t test. P < .05 was considered statistically significant.

RESULTS

Of the 27 patients analyzed, 19 patients (70%) required esmolol. In these patients, SNP caused an increase in the low-frequency component of systolic blood pressure variability and a decrease in the high-frequency component of HR variability, leading to tachycardia (HR range, 95.9 ± 7.3 to 106.7 ± 7.4 beats/min; P < .001). Esmolol suppressed the effects of SNP on the low-frequency component of systolic blood pressure variability and high-frequency component of HR variability, resulting in an immediate decrease in HR to 86.9 ± 6.2 beats/min (P < .001), whereas mean arterial pressure remained unchanged.

CONCLUSIONS

A small bolus of esmolol can suppress reflex tachycardia without significantly changing mean arterial pressure. Thus, esmolol restores the autonomic imbalance induced by SNP during hypotensive anesthesia.

Effectiveness of dexmedetomidine in reducing bleeding during septoplasty and tympanoplasty operations

STUDY OBJECTIVE

To determine the effect of dexmedetomidine on intraoperative bleeding during septoplasty and tympanoplasty operations.

DESIGN

Randomized, placebo-controlled study.

SETTING

Univesity medical center.

PATIENTS

80 ASA physical status I and II patients, aged 18 to 65 years, 40 of whom were scheduled for septoplasty and 40 to undergo tympanoplasty operations.

INTERVENTIONS

Patients undergoing septoplasty (S) and tympanoplasty (T) operations were randomly divided into 4 groups. Dexmedetomidine (D) was administered to Group SD and Group TD first as a bolus dose of one microg kg(-1), then intraoperative maintenance was supplied with dexmedetomidine 0.7 microg kg(-1) hour(-1). Groups S and T (controls) were given identical amounts of saline. If systolic blood pressure measurements are greater than 20% preoperative values, then fentanyl one microg kg(-1) was given.

MEASUREMENTS

Intraoperative blood loss was determined with suction volumes and gauze counting. Bleeding was rated according to a 6-point scale. Hemodynamic parameters and fentanyl administration were recorded.

MAIN RESULTS

Group SD had less bleeding and lower bleeding scores (P < 0.05). In addition, this group received less intraoperative fentanyl (P < 0.05). The only significant difference between Groups TD and T was the amount of intraoperative fentanyl given (35.4 +/- 58.8 vs 110.0 +/- 81.0 microg) (P < 0.05).

CONCLUSION

Dexmedetomidine reduces bleeding, bleeding scores, and intraoperative fentanyl consumption during general anesthesia in septoplasty operations.

Nitroglycerin- and nicardipine-induced hypotension does not affect cerebral oxygen saturation and postoperative cognitive function in patients undergoing orthognathic surgery

PURPOSE

The aim of this study was to investigate the influence of nitroglycerin- and nicardipine-induced hypotension on regional cerebral oxygen saturation (rSO(2)) and postoperative cognitive function in patients undergoing orthognathic surgery.

PATIENTS AND METHODS

Sixty adult patients scheduled for orthognathic surgery were randomly assigned to either the nitroglycerin group (group 1) or nicardipine group (group 2). After induction of anesthesia, hypotension was induced with continuous infusion of nitroglycerin or nicardipine. Mean arterial pressure (MAP), heart rate (HR), and rSO(2) were measured at the following time points: before induction of anesthesia, immediately before commencing induced hypotension, at 30 and 60 minutes after induced hypotension, and immediately before the end of surgery. Cerebral desaturation was defined as a reduction of rSO(2) less than 75% of baseline for > or = 15 seconds. The Mini Mental State Examination (MMSE) was conducted before surgery and then repeated after 1 week.

RESULTS

Baseline rSO(2) values were similar in the 2 groups. There were no significant differences in rSO(2) values between the 2 groups. Cerebral desaturation was not observed in any of the patients. Both nitroglycerin and nicardipine reduced MAP and increased HR during induced hypotension as compared with the baseline values (P < .05). No differences in MAP and HR during baseline and induced hypotension were observed between the 2 groups. Decreased MMSE scores were not observed in any of the patients.

CONCLUSION

Cerebral oxygen saturation and postoperative cognitive function were not impaired during nitroglycerin- and nicardipine-induced hypotension in patients undergoing orthognathic surgery.

Hyperperfusion syndromes: insight into the pathophysiology and treatment of hypertensive encephalopathy

Hypertensive encephalopathy is one of the manifestations of a hypertensive crisis. It is not the absolute value of the blood pressure that causes the encephalopathy, rather the presence of an abrupt rise in pressure. In terms of clinical and radiographic findings, there are many similarities among a group of entities, including hypertensive encephalopathy, eclampsia, and immunosuppressant neurotoxicity. Hyperperfusion syndromes may represent these clinical disease states that may share the same pathophysiology. Magnetic resonance imaging fluid attenuated inversion recovery sequences have recognized the prominent cortical involvement of the disease that had been previously missed on computed tomography. Studies have found cortical involvement in 94% of their patients, particularly in mild cases. Animal models demonstrate endothelial damage and enhanced pinocytosis in the cortex as reasons why edema may begin in that region of the brain. Patients diagnosed with hypertensive encephalopathy should be diagnosed and treated promptly in order to avoid further neurological complications. The mean arterial pressure should be lowered by 20% to 25% within the first hour of patient presentation, followed by further gradual reduction in blood pressure over the following 24 hours. Hypertensive emergency in acute ischemic stroke should be managed with more caution. According to the 2003 American Stroke Association treatment guidelines, for patients with ischemic stroke not eligible for thrombolytic therapy, target blood pressures are a diastolic blood pressure <120 mmHg and systolic blood pressure <220 mmHg. The systolic pressure must be <185 mmHg and diastolic pressure <110 mmHg at all times if eligible for thrombolytic therapy.

Nicardipine versus nitroprusside for deliberate hypotension during idiopathic scoliosis repair

STUDY OBJECTIVE

To compare coagulation, blood loss, and transfusion requirements between patients receiving nicardipine and nitroprusside for deliberate hypotension during idiopathic scoliosis repair.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PATIENTS

51 ASA physical status I patients presenting for spine fusion for idiopathic adolescent scoliosis.

INTERVENTIONS

Patients were randomized to two groups to receive nicardipine or nitroprusside to maintain mean arterial pressure (MAP) between 55 and 65 mmHg.

MEASUREMENTS

Blood loss, blood transfusions, and coagulation studies (thromboelastogram and platelet aggregation) before starting vasodilator, 30 minutes and 90 minutes after starting vasodilator, and 30 minutes after stopping vasodilator, were all recorded.

MAIN RESULTS

There was no difference between the groups in blood loss [nicardipine = 1,129 cc (893 to 1,480), nitroprusside = 960 cc (704 to 1,473)] and only one patient required a nonautologous transfusion. There were no differences in prothrombin time (pT, partial thromboplastin time (pTT), platelet count, or platelet aggregation between groups. There were more episodes of severe hypotension (MAP <45 mmHg) in the nitroprusside group (0% vs. 28%, p = 0.0175). On average, patients in the nicardipine group spent 21 minutes less in the recovery room than did the nitroprusside group (p = 0.043).

CONCLUSIONS

Nitroprusside's effect on platelet aggregation produces no increase in blood loss compared with nicardipine. Nicardipine causes less transient severe hypotension than nitroprusside, although both drugs are acceptable choices for obtaining the goals of deliberate hypotension.

ICU sedation after coronary artery bypass graft surgery: dexmedetomidine-based versus propofol-based sedation regimens

OBJECTIVE

To compare dexmedetomidine-based to propofol-based sedation after coronary artery bypass graft (CABG) surgery in the intensive care unit (ICU).

DESIGN

Randomized, open label.

SETTING

Twenty-five centers in the United States and Canada.

PARTICIPANTS

Two hundred ninety-five adults undergoing CABG surgery.

INTERVENTIONS

At sternal closure, patients in group A received 1.0 microg/kg of dexmedetomidine over 20 minutes and then 0.2 to 0.7 microg/kg/h to maintain a Ramsay sedation score > or =3 during assisted ventilation and > or =2 after extubation. Patients could be given propofol for additional sedation if necessary; group B patients received propofol-based care according to each investigator's standard practice.

MEASUREMENTS AND MAIN RESULTS

Mean sedation levels were within target ranges in both groups. Mean times to weaning and extubation were similar, although fewer dexmedetomidine patients remained on the ventilator beyond 8 hours. Morphine use was significantly reduced in the dexmedetomidine group. Only 28% of the dexmedetomidine patients required morphine for pain relief while ventilated versus 69% of propofol-based patients (p < 0.001). Propofol patients required 4 times the mean dose of morphine while in the ICU. Mean blood pressure increased initially in both groups, then decreased to 3 mmHg below baseline in dexmedetomidine patients; mean arterial pressure remained at 9 mmHg above baseline in propofol patients. No ventricular tachycardia occurred in the dexmedetomidine-sedated patients compared with 5% of the propofol patients (p = 0.007). Respiratory rates and blood gases were similar. Fewer dexmedetomidine patients received beta-blockers (p = 0.014), antiemetics (p = 0.015), nonsteroidal anti-inflammatory drugs (p < 0.001), epinephrine (p = 0.030), or high-dose diuretics (p < 0.001).

CONCLUSION

Dexmedetomidine provided safe and effective sedation for post-CABG surgical patients and significantly reduced the use of analgesics, beta-blockers, antiemetics, epinephrine, and diuretics.

Initial experience with dexmedetomidine in paediatric-aged patients

We present preliminary clinical experience with the use of dexmedetomidine, an alpha2 adrenergic agonist, in children. Dexmedetomidine was administered in three clinical scenarios: (i) to provide sedation during mechanical ventilation; (ii) intraoperatively for controlled hypotension during an orthopaedic surgical procedure; and (iii) to provide sedation during an invasive procedure. Preliminary data from studies in the adult population, its physiological effects and potential applications in paediatric anaesthesia and critical care are discussed.

Fenoldopam for controlled hypotension during spinal fusion in children and adolescents

Fenoldopam is a dopamine1 agonist whose pharmacological effects include vasodilation of the vascular beds of the kidney, mesentery, skeletal muscle, and coronary systems, resulting in a decrease in systemic vascular resistance and mean arterial pressure. The current retrospective review outlines the use of fenoldopam for controlled hypotension during anterior or posterior spinal fusion in 10 children and adolescents, aged 8-14 years and weighing 22-61 kg. Fenoldopam was infused at a starting dose of 0.3-0.5 microg.kg-1. min-1 and increased incrementally to achieve a mean arterial pressure (MAP) of 50-65 mmHg. The desired MAP was achieved in 4-11 min (7+/-2.5 min). The fenoldopam infusion was administered for 135-225 min (160+/-25 min) in doses ranging from 0.2 to 2.5 microg. kg-1.min-1. The mean fenoldopam infusion rate for the 10 cases varied from 0.5 to 1.4 microg.kg-1.min-1 (1.0+/-0.3 microg.kg-1. min-1). No excessive hypotension or clinically significant adverse effects were noted. Statistically significant, but clinically insignificant, increases in heart rate and decreases in PaO2 were noted during the fenoldopam infusion. The baseline heart rate increased from 87+/-13 b.min-1 to a maximum of 114+/-16 b.min-1 (P < 0.0001) during the fenoldopam infusion. In the six patients undergoing posterior spinal fusion, the baseline PaO2 decreased from 232+/-7 mmHg to a low of 199+/-11 mmHg (P=0.0004) during the fenoldopam infusion. Fenoldopam can be used to provide controlled hypotension during spinal surgery in children and adolescents. Future studies, with direct comparison to other commonly used agents, are needed to better define its advantages and disadvantages as well as its effects on estimated blood loss.

Sevoflurane for controlled hypotension during spinal surgery: preliminary experience in five adolescents

The physical properties of sevoflurane suggest that it may be a suitable agent for controlled hypotension. With its low blood:gas partition coefficient of 0.69, it has a rapid onset of action making it easy to rapidly control blood pressure. The current report outlines preliminary experience with sevoflurane for controlled hypotension during posterior spinal fusion in five adolescents. The patients ranged in age from 12 to 16 years and in weight from 49 to to 72kg. The duration of controlled hypotension varied from two to three h. The expired sevoflurane concentration required to maintain the mean arterial pressure (MAP) at 55 to 65 mmHg varied from 2 to 4%. With sevoflurane, there was an increase in heart rate from baseline of 74 +/- 7 beats.min-1 to a maximum of 83 +/- 13 beats.min-1 (P = 0.038). One patient required three intravenous doses of esmolol (10mg each) for a heart rate in excess of 100 beats.min-1. Estimated blood loss varied from 300 to 850 ml. No patient received homologous blood. No excessive hypotension was noted with sevoflurane. No patient required calcium, alpha adrenergic agonists, or ephedrine for excessive hypotension. When controlled hypotension was no longer necessary, the sevoflurane concentration was decreased to 1%. After decreasing the sevoflurane to 1%, the time to return of the MAP to baseline varied from 4 to 8 min (5.6 +/- 1.8 min).

Nicardipine for controlled hypotension during spinal surgery

Nicardipine is the first intravenously administered dihydropyridine calcium channel blocker. Its primary physiologic actions include vasodilatation with limited effects on the inotropic and dromotropic function of the myocardium. Several reports have documented its use in adult patients for pharmacologic control of blood pressure. We present our experience with nicardipine as an agent for controlled hypotension during spinal surgery in 24 children. After the induction of general anesthesia, nicardipine was started at 5 (22 patients) or 10 micrograms/kg/min (two patients). The target mean arterial pressure (MAP) of 55-65 mm Hg was reached in 5.1 +/- 2.1 min (range, 2-10). Intraoperative infusion requirements to maintain the target MAP varied from 0.5 to 7 micrograms/kg/min (mean, 2.5 +/- 1.1). No adverse effects related to nicardipine were noted. Nicardipine appears to be an effective agent for controlled hypotension in children. Future studies are required to determine its advantages/disadvantages compared with more commonly used agents such as sodium nitroprusside or adrenergic antagonists.