Changes in Physiological Dead Space During Deliberate Hypotension

Askrog, V; PENDER, JOHN W.; Eckenhoff, James E.

doi:10.1097/00000542-196411000-00003

Cited by 40 publications

(9 citation statements)

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“…In this study the mean P(ape)co2 of 4.1 torr for all patients, and of 4.5 torr for members of the subgroup of cardiac surgical patients compare reasonably well with the measurements of others (1-6). In the study of Askrog et al (5), using deliberate hypotension by tilting, the greater P(a-pe)coz of 5.9 -+ 2.7 torr might be expected from the changes in ventilation to perfusion ratio throughout the lung due to the positional changes. The lower values of P(a-pe)coz (1.7 i 3.5 torr) found in the population studied by Whitesell et al are not easily explained, but one might speculate that the population they studied was largely composed of patients undergoing surgical and anesthetic procedures with less profound impact on circulatory and ventilatory stability.…”

Section: Discussionmentioning

confidence: 93%

Variation in PCO2 between Arterial Blood and Peak Expired Gas during Anesthesia

Raemer

Francis

Philip

et al. 1983

Anesthesia & Analgesia

100

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gas during anesthesia. Anesth Analg 1983;62:1065-9.with maximum measurement of Pam2 often over-or underestimated Paco2.Mean estimated Paco2 from calibrated P(a-pe)co2 varied Variation in PCOZ between arterial blood and peak expired torr, Calibration of P(a-pe)co, based on a single initial Arterial PcOz (Pace,) can be continuously and noninvasively estimated by monitoring peak expired CO, tension (Ppeco,). The practice of calibrating the estimate by an initial measurement of Paco2 assumes that the difference in PCO, tension between arterial blood and expired gas P(ape)coz remains constant. We examined the stability of P(afrom -7.9-6.4 torr with extreme estimates and duration of anesthesia, variations in ventilation, blood pressure, Ppeco, or temperature. We conclude that estimation of Paco, by monitoring Ppeco2 is not invariably reliable. pe)co, during anesthesia in 15 patients undergoing major surgery. Mean P(a-peko2 values rangedfrom 0.8-7.9 forr

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Section: Discussionmentioning

confidence: 93%

Variation in PCO2 between Arterial Blood and Peak Expired Gas during Anesthesia

Raemer

Francis

Philip

et al. 1983

Anesthesia & Analgesia

100

View full text Add to dashboard Cite

show abstract

“…This is due to inadequate lung perfusion, so that in the presence of apparently adequate respiratory minute volumes falling arterial oxygen tension values can be found to parallel the falling blood pressure. These adverse respiratory effects are largely reversed by employing IPPV with mild hyperventilation and an inspired oxygen concentration of about 40 per cent (Eckenhoff et al, 1963;Askrog, Pender and Eckenhoff, 1964;Eckenhoff and Melman, 1964;Eckenhoff and Rich, 1966). These findings apply equally to the hypotension associated with spinal anaesthesia where increases in deadspace of up to 60 per cent have been found (Askrog, Smith and Eckenhoff, 1964).…”

Section: Discussionmentioning

confidence: 99%

The Effect of Anaesthesia, Hypotension, and Epidural Analgesia on Blood Loss in Surgery for Pelvic Floor Repair

Donald

1969

British Journal of Anaesthesia

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“…Studies (7)(8)(9)(10) have shown impairment of pulmonary gas exchange following the use of vasodilators for deliberate hypotension. Studies (7)(8)(9)(10) have shown impairment of pulmonary gas exchange following the use of vasodilators for deliberate hypotension.…”

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confidence: 99%

Intrapulmonary Shunting during Induced Hypotension

Casthely¹,

Lear²,

Cottrell³

et al. 1982

Anesthesia & Analgesia

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lntrapulmonary shunting during induced hypotension. Anesth Analg 1982;61:231-5.The effect of sodium nitroprusside (SNP) and nitroglycerin (TNG) on pulmonary shunting (Qs/Qt) in 14 consenting adults [nine with normal lung function and five with chronic obstructive pulmonary disease (COPD)] was studied under general anesthesia. Qs/Qt significantly increased ( p < 0.005) from 5.1 9% to 8.81 %, whereas pulmonary arterial pressure (PAP) decreased from 18.5 to 8 torr ( p c 0.005) and pulmonary vascular resistance (PVR) decreased from 235 to 147.75 dynes.sec/cm5 ( p c 0.025) when SNP was administered to patients with normal lung function. Nitroglycerin increased Qs/Qt from 5.13% to 6.19% ( p < 0.005), whereas PAP decreased from 18 to 10 torr ( p c 0.005) and PVR decreased from 237 to 162.6 dynessec/cm5 ( p c 0.025) in these patients. In patients with COPD, SNP and TNG produced no significant changes in Qs/Qt, PAP, or PVR. Cardiac output remained unchanged in both groups of patients. Various mechanisms to explain these results can be postulated. When hypotension is induced in patients with normal pulmonary function, PAP decreases and the effect of gravity puts more blood through dependent areas where most of the shunt units are. In patients with COPD, destructive vascular changes increase PAP, preventing vasodilators from decreasing PVR. In addition, dilation of hypoxic pulmonary vasoconstriction (if present) by SNP and TNG will occur independent of the two previously mentioned mechanisms. These results provide evidence that SNPand TNG-induced hypotension may cause significant impairment in pulmonary gas exchange in patients with normal lung function. In patients with COPD pulmonary gas exchange is not affected after deliberate hypotension with SNP or TNG.

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Changes in Physiological Dead Space During Deliberate Hypotension

Cited by 40 publications

References 0 publications

Variation in PCO2 between Arterial Blood and Peak Expired Gas during Anesthesia

Variation in PCO2 between Arterial Blood and Peak Expired Gas during Anesthesia

The Effect of Anaesthesia, Hypotension, and Epidural Analgesia on Blood Loss in Surgery for Pelvic Floor Repair

Intrapulmonary Shunting during Induced Hypotension

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